IE 771 M H O r o r M A HANDBOOK INCANDESCENT LAMP ILLUMINATION 1913 COPYRIGHT by the GENERAL ELECTRIC CO PRICE FIFTY CENTS Y-177 Mazda Lamps For Standard Lighting Service 100-130 Volts Straight side bulbs 15, 20, 25, 40, 60, 100, 150, and 250 watts. Round bulbs 15, 25, 40, 60, 100, 150, 400, and 500 watts, 200-260 Volts Straight side bulbs 25, 40, 60, 100, 150, and 250 watts. Round bulbs 25, 40, 60, 100 and 500 watts. (For complete schedule of Mazda lamps, see page?; 66 and 66) PREFACE In preparing this book the object has been to provide a ready reference for those inter- ested in incandescent lamps and in problems dealing with incandescent lamp illumination. With this in view there have been included tables and formulae covering the various problems that may present themselves to the central station man, to the lamp solicitor, to the student, and to the user of incandes- cent lamps. As this is the first publication of this nature, it is to be expected that some sections will contain superfluous matter, while others will not be covered thoroughly enough to meet the requirements as intended. Suggestions, criticisms and corrections from those who find use for this book are earnestly solicited, as such will help materially in the preparation of future editions. 268686 CONTENTS Dictionary of Terms General Formulae Photometers and Photometer Methods Candle-power Relations Illumination Calculations Point by Point Method Flux of Light Method Reflectors Classes of Lighting Service Miniature Lamps Sign Lighting Street Lighting Mill Lighting General Information on Incandescent Lamps History of the Incandescent Lamp Ktching and Frosting The Best Lamp Cleaning and Handling of Incandescent Lamps Cost of Light Characteristics of Lamp Filaments Average Performance of Lamp Filaments Energy Losses in Lamp Filament Prevention of Static Effects Distribution Systems Formulae Wire Tables Rectifier Watt-hour Meters Extracts from N. E. C. Storage Batteries Transformers Types Connections Testing Miscellany Trignometric Functions Mensuration Rates Resuscitation from Electric Shock Index Dictionary of Yeriris The Actual Life of a lamp is the number of hours it burns before its filament breaks, or be- fore it becomes useless. Ampere. The unit of electric current strength is the ampere. It is that current which, when passed through a solution of silver nitrate in a silver voltameter, will deposit silver at the rate of .001118 grams per second. It is the amount of current flowing through a resistance of one ohm under a pressure of one volt. Candle=Power is the unit of intensity of light emitted from a lamp or other light source. (See "Candle-Power Relations" for further discus- sion) . The Cold Resistance of a filament is its resist- ance at centigrade. Efficiency as applied to incandescent lamps is usually expressed in watts per candle. (See "Candle- Power Relations.'') Fechner's Fraction is the minimum fractional difference between any two luminosities which the eye can perceive. This ability to discern difference in luminosities depends on the ca- pacity of the eye to determine shade perception. The value of this fraction attains its normal value, that is, the eye is at its full sensitiveness when the illumination is about 1 foot-candle. (See page 83.) The Flux Factor or lumen constant for any given zone is the constant which multiplied by the average candle-power in that zone gives the total quantity of light expressed in the lumens emitted in that zone. Glare is a condition of brilliancy of light sources or illuminated surfaces, whereby ocular discom- fort or interference with vision results. Glare is likely to occur when a bright light or excessive contrast of intensity intrudes in the field of vision. Illumination, as generally used in a technical sense, refers to luminous radiation falling on surfaces in contradistinction to the light emitted from a lamp. Intensity of Illumination is measured in foot- candles, one foot-candle being the intensity in- cident at right angles upon a plane one foot distant from a point source of one candle-power. Flux of Illumination is measured in lumens and is equal to the intensity of the illumination multiplied by the area over which it is dis- tributed, i. e., lumens = foot-candles X square feet. Intrinsic Brilliancy, or surface brilliancy, is the intensity of light emitted from a source per unit of its projected area. It is usually expressed in candle-power per square inch. 1 Kelvin's Law. The'most economical area of a conductor is that for which ^the annual cost of energy wasted is equal to the anriual interest on that portion o? the capital outlay which repre- sents the cost of metal used. (See example page 100.) The Kilowatt is 1000 watts. Lumen. (See ' Candle-Power Relations.") Luminous Efficiency denotes the ratio of the luminous radiation of an illuminant to its total radiation. The Mean Horizontal Candle=Power is the aver- age of the candle-powers in the horizontal plane in all directions about a lamp whose axis is ver- tical. The Mean Spherical Candle=Power is the mean of the candle-powers in all directions about a lamp. Mean Zonular Candle-Power is the average candle-power given off in the particular zone in question. The Micron is the unit of light wave length and is equal to .001 mm. A Mil is .001 inches. A Circular Mil is the area of a circle 1 mil in diameter. The area of any conductor in circular mils is equal to the square of its diameter in mils, or to 1,000.000 times the square of its di- ameter in inches. 1 sq. mil is equal to 1.273 times one circular mil The Net Efficiency of an illuminant is the ratio of the luminous energy to the total energy con- sumed. Ohm. The unit of resistance is the ohm and is the resistance that would be offered to the flow of an electric current by a column of mer- cury 106.3 cm. in length, and 14.4521 grams in mass. A Photometer is a device used to compare the candle-powers of light sources. The simple pho- tometer consists of two lamp receptacles, one at either end of a scale called the photometer bar. Between these receptacles is a movable sight box for comparing the light intensities incident on the screen contnined therein. Purkinje Effect. If a red field and a blue neld are illuminated so as to appear of about the same brightness, and then the intensity of illu- mination on both be greatly reduced in the same proportion, the red field will appear darker than the blue; and conversely, if the intensity be greatly increased the red will appear brighter. Selective Radiation occurs where a surface emits radiation of the various wave lengths in different proportions from that of a theoretically black body at the same temperature. The Spherical Reduction Factor is the ratio of the mean spherical candle-power to the mean horizontal candle-power. Temperature Coefficient. The resistance of a filament changes by the addition ' or subtraction) of a certain percentage of the cold resistance for each degree of temperature change. This per- centage is called the temperature coefficient. The formula for finding the resistance at any temperature is Rt = Ro + Ro a t where Ro = the cold resistance a = the temperature coefficient t the degrees centigrade at which Rt is to be found. The Useful Life of a lamp is the number of hours it burns before it drops to 80% of its initial candle-power. The Visible Spectrum includes wave lengths varying from approximately 0.4 microns to 0.8 microns. Visual Acuity is the ability to observe detail. Acuity is measured by the ratio of the distance at which the eye can discern the details of a standard letter to the distance regarded as standard for that letter. (See article, page 83.) The Volt is the unit of electro-motive force or electrical pressure. It is the pressure necessary to force a current of one ampere through a re- sistance of one ohm. The Watt is the unit of electrical power; it is the product of instantaneous values of electro- motive force and current in the circuit when their values are respectively one volt and one ampere. The Watt-Hour is the unit of electrical energy, and is the product of power and time. Formulas OHM'S LAW FOR DIRECT CURRENT E = IR Volts =: amperes X ohms Amperes volts -f- ohms Ohms volts -7- amperes Series Circuit R = n + r2 + rn E = ei + 62 + en R is the total resistance of the circuit and is the sum of the resistances of sections of the circuit. E is the total wattage and is the sum of the voltage drops across the resistances r, r* and rn . Shunt or Multiple Circuit I = ii 4- ia 4- is E e 62 = e 1 R = rsr3 ~^~ rira + rirs Parallel and Series Circuit I -AW/A i I WWV Fig. 1 I := h 4- ia 4- is E = Ir 4- e 4- Ir 4 e = hn = isra = iara Power in Direct Current Circuits Watts = volts X amperes Amperes = watts -f- volts OHM'S LAW FOR ALTERNATING CURRENT E-IZ Volts := amperes X impedance ohms Z = impedance ohms = \/R a + X 2 R = ohms resistance X = ohms inductive reactance The voltage drop due to inductive reactance is 90 ahead of the IR drop and the impedance drop is the resultant of the two. When repre- sented graphically the IZ drop is the diagonal of the parallelogram constructed on the IX and IR drops. As the diagonal is equal to the square root of the sum of the sides squared, The common factor I cancels out so that Z = VR 2: f X 2 Power in Alternating Current Circuit Watts = volts X amperes X power- factor The power-factor is the cosin of the an- gle between the impedance volts IZ and the volt- i> age drop IR and is equal to . /j Conversion Factors (746 watts ~ | 33 ,000 ft. Ibs. permin. f . 00134 h. p. 1.44.24 ft. Ibs. per min. | .000000377 kw-hrs. ~ \ .0000005 h.p. hrs. f 1000 watt , v _ J 1-34 h. p. ] 2,655,400 ft. Ibs. per hr. 1229 Ibs. of coal oxidized per hour flOOO watt hours I 1.34 horse-power hrs. 1 kw-hr. - < 2,655,400 ft. Ibs. 229 Ibs. of coal oxidized with per- L feet efficiency. ( .746 kw-hr. _ J 1.980,000 ft. Ibs. ] 172 Ibs. of coal oxidized with per- L feet efficiency. Calculation of Lamp Data Candle-power watts -r watts per candle Candle-power = volts X amperes ~r watts per candle Candle-power = ohms X (amperes) 2 ~- watts per candle Watts = candle-power X watts per candle Watts per candle =. watts -r candle-power Amperes = candle-power X w.p.c- -r volts Ohms = watts ~r (amperes) 2 = candle-power X w.p.c. -r (amperes) 2 Volts = watts -r amperes = candle-power X w. p.c. -r amperes Mean spher. C.P. = mean hor. C.P. X mean spher. C.P. factor Mean spher. C.P. Mean spher. C.P. factor = M h c.p. Mean hor. C.P. = j^^^f^^ Total cost of lighting (renewal cost and cost of power) for any given number of hours H. is equal to f H X Price of Lamps ) , \ H X Initial watts \ Total life > < 1000 Cost of power per kw-hr. | Method of Photometering lncandes= cent Lamps As all lamps must be photometered and labeled with the voltage at which they give the required candle-power, it is necessary to have working standards with which they may be compared in order that the rating be uniform. These stand- ard lamps are carefully selected and rated on an accurately designed precision photometer, and are then checked by the Electrical Testing- Laboratories. It is quite possible to determine when the two sides of a screen are illuminated to the same intensity, when some arrangement is made whereby both sides can be viewed at the same time. This, combined with the law of inverse squares, forms the basis of all photornetering methods. A working standard, made as ex- plained above, is set in a revolving holder at one end of a photometer bar, and the voltage is ad- justed on a lamp at the other end, known as the back standard, until equal intensities are ob- served on the screen. If it is desired to "set" this back standard for the same candle-power as the standard lamp, the screen must be halfway between the two lamps, that is, in the equation, '2 ,2 - P " * = the ratio must be unity. C. P. 2 A 2 d 2 C.P. C.P.o Fig. 2 After "setting" the back standard, the work- ing standard is replaced by the lamp to berated, and the voltage is adjusted on this lamp until a "balance" is obtained on the screen. That volt- age is marked on it as the voltage at which it will give its rated candle-power. With a little experience the operator soon becomes an ac- curate reader, being able to check her readings with little or no variation. Photometer Heads The types of photometers in most general use are those employing the Bunsen and the Lumner Brodhun sight boxes and the flicker photometer. In the Bunsen sight box, mirrors are arranged so that both sides of a screen can be observed at the same time. The screen is made of white opaque paper with a sharply defined translucent spot, usually made with paraffine, in the center. The Leeson disc is a slight improvement over the Bunsen screen. This consists of a trans- lucent disc between two opaque discs with two star shaped apertures opposite each other. _ Al- though they are not the most accurate 'sight boxes, they are the least tiring to the eyes when used continually. Fig. 3 The Lumner Brodhun Screen is a far more satisfactory form for precise work. It is some- what intricate as will be seen from Fig. 3 which shows the sight box in plan. The box is mounted on the photometer bar with its axis of rotation lUiii UULII siu.cn uy LUC u^i\-> \JL i.ii^ mil ji wi o t- 1, A- x nd the right angled prisms, A, B t shown in plan Fig. 4 Fig. 5 as shown. When the prisms are cemented, the spaces between the strips are transparent, but at the strips there is a total reflection for light enter- ing normal to the free prism faces. Therefore the odd numbered rays (Fig. 4) received from c c f via F\ enter the sight field only through the cemented faces, and the even rays from d d r via Fs only by total reflection at the strips. The arrows in the figure show plainly the course of the rays. The result is a field resembling Fig. 5. each half circle receiving light from one side of the screen and having superposed upon it a trapezoidal area received from the other side of the screen. These areas are slightly darkened by absorption from the glass strips me and gb t so that when everything is in balance one has two equally shaded areas in a uniform field. One can work either by uniformity of field or by equality of contrast of the trapezoids, preferably the latter particularly in comparing lights differ- ing slightly in color. When lights of two different colors are to be compared, as for instance red and blue, it is ex- tremely difficult to judge when the intensities are equal. For precise work the flicker photo- meter is used. In this type a screen is illuminated by the two sources of light in rapid alternation. When the speed is adjusted between 10 and 20 alternations per second the illumination appears to flicker until the intensities of the two become equal, or the flash from one bridges over the gap to the flash from the other. The Sharp Millar Illuminometer is used quite extensively as a portable instrument. A com- partment at one end of the blackened interior contains a Lumner Brodhun prism. At this end of the box is an elbow tube, the top of which is fitted with a diffusing cap of milk glass. A mirror is placed at the elbow of the tube which reflects the light rays to the Lumner Brodhun prism set, where they are redirected to the eye-piece in the side of the box. The other end of the prism compartment contains a milk glass window illum- inated from behind by a comparison lamp at the further end of the box. This lamp can be moved back and forth to secure a balance. When a balance is obtained, the intensity is read directly on a scale in the side of the box, the scale being based on the law of inverse squares. Candle-Power Relations The candle-power as a unit of light intensity was originally determined by the horizontal in- tensity of light from a certain specified candle known as the British standard candle. But since the value can be more accurately pre- served and reproduced in the incandescent lamp, this arbitrary value is now maintained in tested incandescent lamps in the U. S. Bureau of Stand- ards at Washington and in other laboratories. The present standard in general use in the United States, Great Britain, France and other countries (Germany excepted), is the Inter- national Candle-power, which was established at the International Conference of 1909. It js 1.6% less than the British candle used in this country. Thus 16 British candle-power corres- ponds to 16.26 International candle-power. The relations of the International Candle to other terms are as follows; 1 International Candle = 1 American Candle United States) . 1 International Candle = 1 Pentane Candle (Great Britain) . 1 International Candle = 1 Bougie Decimale or 0.104 Carcel Units. (France) . 1 International Candle = 1.11 Hefner Units (Germany). For a more detailed description reference is made to U. S. Bureau of Standards Circular No. 15, dated May 20, 1909. In the case of the incandescent lamp it has become customary to rate a lamp in terms of the mean horizontal candle-power with clear bulb and no reflectors. The horizontal candle-power measurement was adopted simply because it was the customary and most convenient method of measuring the light intensity of gas, oil, and candle flames, which burn generally in a vertical direction. In- candescent lamps, however, may be used in any and every position, and in addition it is possible to alter considerably the distribution of light from an incandescent lamp by the simple pro- cess of changing the shape of the filament. As horizontal measurement of candle-power disre- gards all light emitted save that emitted in a horizontal direction, and as light sources giving widely different total amounts of light may emit the same amount of light in a horizontal direc- tion, it obviously follows that this method of candle-power measurement is incomplete, espec- ially when lamps of different types of filaments are compared. Furthermore, with any type of lamp the intensity of light varies in different di- rections, particularly for various angles of eleva- tion. It is moreover modified by the use of globes and reflectors. Therefore a candle-power rating of a lamp has no value (except in the case of a standard type of incandescent lamp) unless the equipment used and the candlepower re- ferred to are fully described. A full and complete measure of candle power requires consideration of the light given in all directions, or at all points of a sphere surround- ing the lamp. If we take the mean of all these candle-power values we have what is termed the mean spherical candle-power. The mean spher- ical candle-power may then be considered as a measure of the total flux of light. M. S. C. P. X 4 IF = total lumens emitted. The complete measurement of spherical can- dle-power of incandescent lamps involves con- siderable work with special apparatus. It is possible, however, to express approximately the mean spherical candle-power in terms of the mean horizontal candle-power and a spherical reduction factor. The spherical Candle-power Factor or Reduc- tion Factor of a lamp is the ratio of its Mean Spherical to its Mean Horizontal Candle-power, or Mean Spher. C. P. -f Mean Horiz. C- P. Example: -The Spherical Candle-power Factor of a lamp whose Mean Horizontal Candle-power is 33.9, and whose Mean Spherical Candle-power is 26.44, is equal to 26.44 -r 33.9 = .78. The Spherical Reduction Factors for tungsten filament and metallized filament lamps are as follows: Mazda Compensator type 79 Tubular 78 Train Lighting 80 Round Bulb, 15 W-250 W, 100-130 volt .78 All other large styles - 79 Gem Regular 825 Train Lighting 85 The Mean Horizontal Candle-power is the mean of the candle-power in all directions either above or below the horizontal. When above it is designated as mean upper hemispherical can- dle-power. Mean lower hemispherical candle- power, i.e.. below the horizontal, is understood when merely mean hemispherical candle-power is specified, This unit is then a measure of the flux of light in its hemisphere. Lumens (in lower hemisphere) = 2^ M. Hemispherical C.P. The lumen is the unit of the flux either of light or of illumination, and is equal to the intensity distributed over one unit of space. Ex. -Lumens (of light)=: C.P. X radians of solid angle. There dies X square feet of area. The lumens of light correspond directly to those of illumination, so that if all the lumens from a light source fall upon a surface, the lum- ens of light and of illumination will be equal. For practical service and in the commercial rating of lamps the mean horizontal candle- power is still in use, but in testing and compar- ing lamps of different shape filaments the mean spherical candle-power should be considered for the following reasons which apply to lamps of any one class of filament. The life and candle-power performance of a lamp depend upon the temperature of its fila- ment. It is not practicable to measure this tem- perature in degrees, and since with similar conditions of vacua and filament surfaces the temperature is indicated by the consumption of power per candle or watts per candle, we utilize watts per candle as a basis for determining rela- tive temperatures or the relative measure of strain upon filaments while operating. As watts per candle is a ratio of watts con- sumed to total candle-power given, it is appar- ent that the method of obtaining the candle- power has an important bearing in determining the relative strain. When the horizontal candle- power is taken, the watts per candle determine the relative strain correctly, only when the fila- ments are exactly alike in shape. With spherical candle-power, however, the watts per candle determine correctly the relative strain between filaments no matter what their size or shape. If, therefore, a test be made between lamps hav- ing filaments differing in shape, we must com- pare them at the same watts per mean spherical candle-power and not at the same watts per mean horizontal candle-power. This can be ac- complished by either of two methods, viz.: 1. By testing the lamps at the same watts per mean spherical candle-power, or 2. By testing the lamps at the same watts per mean horizontal candle-power, and calculat- ing their lives at the same watts per mean spher- ical candle-power by means of their spherical and horizontal candle-powers and their life factors, Ex.: Suppose two lamps, A and B, are placed on test at 1.23 watts per Mean Horizontal Candle- power, and that = x 282 and Mean Spher. C. P. .Mean Hor. C.P. Mean Spher. C. P. Then Watts per Mean Spher. C.P. of A = 1.23 X 1.282 =1.577. Watts per Mean Spher. C.P. of B = 1.23 X 1.208 = 1.486. Considering the watts per M.S. C.P. of A as 100%, the watts per M.S. C.P. of B will be 94.3%, and the life factor of B is 68%. Therefore to re- duce lamp B to an equal comparative basis with lamp A we must multiply B's result by .68. Efficiency of a lamp or light source is expressed in terms of specific consumption, or specific out- put, as watts per mean spherical candle-power, total lumens per watt, lumens per cubic foot of gas or per gallon of oil. In the case of the in- candescent lamp it is customary to use watts per candle-power (Mean Horizontal). Lumens per watt is, however, a more reliable measure and will probably be used to a greater extent, if not altogether in the near future. The rated or commercial efficiency of a lamp is its initial efficiency or efficiency when new. As the efficiency of a lamp changes during its life it is obvious that its average efficiency is quite different from its initial efficiency and should be carefully distinguished from it. The candle-power and voltage of a lamp are fixed by its initial efficiency (W.P.C ), and the three terms, candle-power, voltage, and watts per candle are necessary for a complete express- ion of a lamp's rating. Illumination Calculations Relations of Foot Candles, Candle-Power, and Distance between the Source of Light and the Surface Illuminated. Consider a light of 1 candle-power intensity in all directions placed at the center of a hollow spherical shell of 1 ft. radius. This light would illuminate the inner surface with an intensity of 1 ft. candle, and the illuminated area would be 4 if (12.56) sq. ft., since the surface of a sphere is found by multiplying the square of the radius by the constant 4 if. If the same light were placed at the center of a spherical shr-11 of 2 ft. radius, the quantity of light originally distributed over the area of 4 if sq. ft. would now be distri- buted over an area of four times 4 if, (50.28) sq. ft. It is readily seen that the illumination on the larger surface would be 1 A of a foot candle, since the total amount of light is the same in both cases, and the larger surface is four times the smaller. A lamp of 16 spherical candle power at the center of the smaller sphere would give an illumination of 16 foot candles on the innersurf ace. If placed at the center of the larger sphere the illumination on the inner surface would be 4 foot candles. If placed at the center of a hollow sphere of 4 ft. radius the illumination on the inner surface would be 1 foot candle. If a light source be located at the center of a spherical surface all the light rays emanating therefrom will meet this surface normally : hence, normal illumination in foot candles is found by dividing the candle-power of the source by the square of its distance from the surface illuminated . Therefore, normal illumination = Candle-power (c.p.) Distance squared (d a ) 12 This rule, known as "The Law of Inverse Squares" does not apply where the light falls ob- liquely on the surface under consideration, nor where the source is a long line, as the Moore tube. Calculation of Horizontal Illumination (Point by Point Method) THIS is THE FUNDAMENTAL OR BASIC METHOD Fig. 6 In practical illumination most of the rays do not meet the surface normally. In Fig. 6 the rays from the lamp shown at "S" are assumed to be normal to the plane "AB". As has been shown the illumination on this plane is _c.p. In=' d 2 (1). C.P. equals candle-power of the lamp at"S"; d equals distance "SA". But in reality the light that would have been intercepted by "AB" will be distributed over the larger plane "AC". From the triangle ABC rr- = cos a ......... (2) hence, AC = ........ (3). that is, the square feet in plane AC is found by dividing the square feet in AB by the cos a. To illustrate, if a had such a value as to make its cos equal to .5, the area of the plane AC would be found by dividing that of AB by .5, that is, area AC would be twice as great as AB, and the in- tensity of illuminati- >n would, therefore, be one-half that of AB Hence the general rule that since the area of the oblique plane AC is obtained by dividing that of the normal plane AB by cos a, the illumination of AC is thai of AB multiplied by cos a, or for oblique illumination, Ih ~bjr cos a (4) But from the triangle OSA 13 1. Table of Angles, Sines and Cosines. a sin a sin a a cos a cos 2 a cos 3 a .0 .0000 1.000 1.000 1.000 1 .0175 .0000 1.000 1.000 1.000 2 | .0349 .0000 .999 .999 .998 3 .0523 .0001 .999 .997 .996 4 .0698 .0003 .998 .995 .993 5 .0872 .0007 .996 .992 .989 6 .105 .0011 .995 .989 .984 7 .122 .0018 .993 .985 .978 8 .139 .0027 .990 .981 .971 9 .156 .0038 .988 .976 .964 10 .174 .0052 .985 .970 .955 11 .191 .0069 .982 .964 .946 12 .208 .0090 .978 .957 .936 13 .225 .0114 .974 .949 .925 14 .242 .0142 .970 .941 .913 15 .259 .0173 .966 .933 .901 16 .276 .0209 .961 .924 .888 17 .292 .0250 .956 .915 .875 18 .309 .0295 .951 .905 .860 19 .326 .0345 .946 .894 .845 20 .342 .0400 .940 .883 .830 21 .358 .0460 .934 .872 .814 22 .375 .0526 .927 .860 .797 23 .391 .0596 .921 .847 .780 24 .407 .0673 .914 .835 .762 25 .423 .0755 .906 .821 .744 26 .438 .0843 .899 .808 .726 27 .454 .0936 .891 .794 .707 28 .470 .104 .883 .780 .688 29 .485 .114 .875 .765 .669 30 .500 .125 .866 .750 .650 31 i .515 .137 .857 .735 .630 32 .530 .149 .848 .719 .610 33 .545 .162 .839 .703 .590 34 .559 .175 .829 .687 .570 35 .574 .189 .819 .671 .550 36 .588 .203 .809 .655 .530 37 .602 .218 .799 .638 .509 38 .616 .233 .788 .621 .489 39 .629 .249 .777 .604 .469 40 .643 .266 .766 .587 .450 41 .656 .282 .755 .570 .430 42 .669 .300 .743 .552 .410 43 .682 .317 .731 .535 .391 44 .695 .335 .719 .517 .372 45 .707 .354 .707 .500 .354 Table of Angles, Sines and Cosines Continued. a<> sin a ' sin :5 a cos a cos -a cos s a 46 .719 .372 .695 .483 .335 47 .731 .391 .682 .465 .317 48 .743 .410 .669 .448 .300 49 .755 .430 .656 .430 .282 50 .766 .450 .643 .413 .266 51 .777 .469 .629 .396 .249 52 .788 .489 .616 .379 .233 5A .799 .509 .602 .362 .218 54 .809 .530 .588 .345 .203 55 .819 .550 .574 .329 .189 56 .829 .570 .559 .313 .175 57 .839 .590 .545 .297 .162 58 .848 .610 .530 .281 .149 59 .857 .630 .515 .265 .137 60 .866 .650 .500 .250 .125 61 .875 .669 .485 .235 .114 62 .883 .688 .470 .220 .103 63 .891 .707 .454 .206 .0936 64 .899 .726 .438 .192 .0842 65 .906 .744 .423 .179 .0755 66 .914 .762 .407 .165 .0673 67 .921 .780 .391 .153 .0597 68 .927 .797 .375 .140 .0526 69 .934 .814 .358 .128 .0460 70 .940 .830 .342 .117 .0400 71 .946 .845 .326 .106 .0345 72 .951 .860 .309 .0955 .0295 73 .956 .8)5 .292 .0855 .0250 74 .961 .888 .276 .0,60 .0209 75 .966 .901 .259 .0670 .0173 76 .970 .914 .242 .0585 .0142 77 .974 .925 .225 .0506 .0114 78 .978 .936 .208 .0432 .0090 79 .982 .946 .191 .0364 .0070 80 .985 .955 .174 .0302 .0052 81 ."88 .964 .156 .0245 .0038 82 .990 .971 .139 .0194 .0027 83 .993 .978 .122 .0149 .0018 84 .995 .984 .105 .01(9 .0011 85 .996 .989 .0872 .0076 .0007 86 .9976 .993 .0697 .0048 .0003 87 .9986 .996 .0523 .0027 .0001 88 .9993 .998 .0349 .0012 .0000 89 .9998 1.000 .0175 .0003 .0000 90 1.000 1.000 .0000 .0000 .0000 s I o 8888888S.S ; 8 : 8 : 8 : 888 ; 8 : 8 ; S.888.88 : ll8 ir ?' 3 i? ilisilliilill oopooooc is23|||s sppppppopc 8ooo88o ppppppSqpppppSpopSS pajisap si uoiieuuunin jo Xiisuaiui aaaqM. miod 01 aoanos iqSjl Japuri ' ,oajtp luiod uiojj jaaj in aouBjsip JB;UOZUOH 82 8E il 16 h SO ,_. = - = cos a (5) or, d SA d=- h = (6) cos a Squaring, d 2 = -~- (7) cos 2 a Substituting for d 2 in equation (4) lh = - cosa (8) values of a from 1 to 90. To facilitate the use of the above formula there are given in Table 2, values of illumination on horizontal planes at different heights and at different horizontal distances of a light source of 1 candle-power and also the corresponding angles made by the light rays with the perpendicular to the plane. Method of Using: Table From the lamp and reflector in use obtain the distribution curve. Take from Table 2 the value (in foot candles) of illumination which a one candle-power light source would produce at the point selected. Also note the angle corres- ponding to this point. From the distribution curve of the lamp take the candle-power at the corresponding angle. Multiply this value by the illumination value found in the table, and the resulting value will be the illumination, in foot candles at the point selected, of the lamp under consideration. For example : required the illumination pro- duced by a 60 watt clear Mazda lamp with intensive type Holophane reflector at a point 12 ft. below and 12 ft. to one side of the lamp. From Table 2 the vahte corresponding to these distances is .0025 foot candles and the corresponding angle is 45 C . From the distribution curve of the 60 watt lamp with intensive type reflector on Page 31 the candle-power at 45 is approximately 64. Then .0025 x 64 = .16 which is the illumination at the point selected. If there be more than one lamp in the room , the illumination produced by each lamp is found in thfe above manner, and the sum taken for the total illumination at the point under consideration. Calculation of Vertical Illumination Suppose it is desired to calculate the illumina- tion I on a vertical plane through A. The light rays that would have fallen on AB will be inter- cepted by the vertical plane DA. From triangle ABD 17 AB AD Then ......... (10) sin a that is, the square feet in AD is found by divid- ing the square feet in AB by the sin a. To illustrate, if a had such a value as to make sin a equal to .866 the area of the plane AD would be found by dividing the area of AB by .866. In other words, the area of AD would be 1/.866 times that of AB and the intensity of illumination on AD would eaual .866 of that on AB. In general then, the intensity of illumination on a vertical plane is equal to that on the normal plane, multiplied by the sin a ......... (11) From triangle OSA OA / -5-7- -r sin a ......... (12) oA Q ord= / ......... (13) sin a /2 squaring, d 2 = -T- sin 2 a then in equation (11) /2 Iv = c. p. sin 2 a -~ -7-=- ........ (15) sin 2 a = ^sina ......... (16) The values of sin 3 a are given in Table 1. Flux of Light Method of Calculating Horizontal Illumination. For rapid calculation the following tables and formulae will be found convenient : As stated under "Candle-power Relations," a lumen is the quantity of light required to illu- minate 1 sq. ft. area with an intensity of 1 ft. candle. Now from Table 8 can be determined the intensity of illumination in foot candles recommended as satisfactory for various classes of service. The floor area of the '"oom is known and the product of foot candles times sq. ft. floor area equals effective lumens required. Having ascertained the effective lumens required, there are two methods by which the number and sizes of lamps necessary can be determined. The efficiency of an illumination effect can be expressed in effective lumens per watt, which is equal to the foot candles divided by watts per sq. ft. This shows the distinction between total lumens as emitted by a light source and effective lumens as received on some surface or working plane. As a result of numerous experiments the effec- tive lumens per watt for various lamps and reflector equipments and conditions of walls and ceilings, has been determined. These values are shown below in Table 3. 3. Effective Lumens per Watt Lamp Equipment Ceiling Walls Constant Mazda Clear Holophane Refl. Light Light 5.0 Mazda Clear Holophane Refl. Light Dark 4.0 Mazda Clear Holophane Refl. Dark Dark 3.4 Gem Clear Holophane Refl. Light Light 2.2 Gem Clear Holophane Refl. Light Dark 1.8 Gem Clear Holophane Refl. Dark Dark 1.5 By dividing the total effective lumens required by the proper constant from the above table, the total wattage required is obtained. This wattage is divided by the necessary number of lamps (method of determining this is shown later) to get the watts per lamp. The other of the two schemes mentioned above is as follows: Illumination tests have shown that with certain lamps, reflectors, and wall conditions, a given percentage of the total lumens emitted by the lamp reaches the working plane and the percentage is called the illumina- tion constant for that particular equipment (Table 4). Hence, if the total effective lumens required be divided by this illumination constant, the total lumens emitted by the lamp is determined. Di- viding this by the required number of lamps will give the total lumens per lamp. The total lumens given by any of the standard lamps is shown in Table 5. 4. Illumination Constants Lamp Equipment Ceiling Walls Constant Mazda Mazda Mazda Gem Gem Gem * Clear Holophane Rfl. Light Light Dark Light Light Dark Light Dark Dark Light Dark Dark .64 .51 .43 .57 .45 .38 5. Total Lumens Given by Different Types of Incandescent Lamps RATED MAZDA OR TUNGSTEN GEM CARBON WATTS 100 v 200,,. 100 v 100 v 200 v 130 V " 260 V ' 130 V ' 130 v ' 250 V 10 21. 15 112. 20 151. 50. 25 185. 84. 30 96. 35 84. 40 320. 160. 45 300. 50 205. 175. 60 500. 400. 250. 210. 170. 80 335- 100 830. 670. 420. 350. 120 420. 340. 150 1250. 1000. 250 2170. 400* 3470. 1670. 500* 4330. 4030. *Round bulb lamps. All other lamps given here have regular type straight sided bulbs. Determining: the Number of Lamps The area to be lighted should be divided as nearly as possible into equal squares and the light unit placed at the center of each square. The size of the square depends in some cases upon the extent to which shadows will be objec- tionable and in general the smaller the square the less intense will be the shadows. In lighting large offices where individual desk lights are not employed, the square should be comparatively small in order to have the light on any one desk coming from many units. Table 6 gives the de- sirable sizes of squares for various classes of service. Having determined the wattage of the lamps, the number to be used and the spacing, there remains the choice of the reflector. Choice of Reflector In selecting a reflector, a careful study of the dimensions of the room is necessary, in general, an extensive type of reflector should be used for stores where there is a single row of lights illu- minating both show cases and shelves, also for large areas with low ceiling. 20 w w H ft |p = ^J p p q q q p q c> 5 5 Q fi I I | 1 ,:,,, : ,,.,:^ g p Q o t-i t-i Q p i* p p p $H gj 3 t/2 w tn -*-< -*-> -*-> 42.5?.5P.Sf 5 2 0, ... 2 I*" o K If the area to be lighted is small or requires high intensity of illumination, an intensive re- flector is used. Examples may be found in restaurants, department stores, etc. Focusing- reflectors are used in show windows, offices, and other places where high intensities are required. Table 7 shows the proper height for lamps in terms of distance between units. Application of the Foregoing: Paragraphs As an example of the above rules, the "flux of light " method is used for the following specific case : A shoe store 50 ft. x 150 ft. with a 12 ft. ceiling, light ceiling and side walls, lined with shelves containing boxes is to be illuminated. From the table of foot candle intensities recommended for classes of service, Shoe stores, 2.0 4.0, taking 3 as an average. Floor area, 50 x 150 =r 7500 sq ft. Effective lumens required, 7500 x 3 = 22,500. Since prismatic glass reflectors are very effi- cient, are sufficiently decorative for this class of service, and the Holophane are the best made and most efficient of this class of reflectors, it is applicable here. First Method In Table 3 for clear Holophane, light walls and ceiling, the effective lumens per watt are 5. Hence, 22,500 ~ 5 gives 4500 watts required. Second Method The illumination constant (Table 4) for clear Holophane, light ceiling and light walls, is .64. Hence, 22,500 -j- .64 gives 35,150 total lumens required. Next, referring to the table of desirable sizes of squares is found, "stores, 11 to 15 ft. ceiling height, 10 to 16 ft. squares." For a symmetrical arrangement the size of the squares will be taken as \2% ft., making four rows of twelve lamps each, a total of 48 lamps. Then, 4500 watts -r 48 gives 93.8 watts per lamp. Taking the 100 watt lamp as the nearest size. Or 35,150 total lumens ~ 48 = 732 lumens per lamp. From Table 5 the 60 watt Mazda lamp gives 500 total lumens and the 100 watt 830 total lumens. The 100 watt lamp should be used as it is better to run a little above the calculated value than to drop a marked amount below it. If it is desired to more closely approach the values calculated, the rows of lamps may be spaced 12% ft. apart, and in the rows the lamps may be spaced 13} ft. apart, making a total of 44 100 watt lamps. In a shoe store the plane of illumination is about 1 ft. from the floor, where inspection of the shoes is made, and there must be sufficient dif- fused light on the boxes to enable the clerk to read the labels. With the above arrangement 22 of lamps and conditions to be met, the inten- sive type of Hplophane reflector is applicable. The average distance between lamps is 13 ft. As shown in Table 7 the hanging height for intensive reflectors should be % of the distance between lamps. % X 13 = 10.4 or, say, 10K ft. from the working plane or the surface to be illuminated. The lamps should then be hung about 11> ft. from the floor. As a summary of the foregoing calculations, 44 100 wait bowl frosted Mazdalamps, equipped with intensive, clear, Holophane reflectors, form H holders, spaced 12% x 13> ft., hung with the center of the lamp about 11 % ft. from the floor. 8. Foot -Candle Intensities Recom- mended for Various Classes of Service. Armory or Drill Hall 2.0 Armory (Cavalry tan-bark floor) 3.0 Art Gallery (walls) 5.0 10.0 Auditorium 1.0 3.0 Automobile Showroom 3.0 6.0 Automobile (interior) 5 1.0 Ball Room 2.0 3.0 Bank (general) 2.0 3.0 Bank (desk work) 4.0 6.0 Bar Room 2.0 5.0 BarberShop (over chairs) 3.0 6.0 Bath (public) Dressing rooms .7 1.0 Swimming pool 1.5 2.0 Billboard 5.0 15.0 Billiard Room (general) .8 1.5 Billiard Room (with distributed and diffused light) 6.0 10.0 Book Binding. Folding, Assembling, Pasting, etc. 2.0 3.0 Cutting, Punching and Stitching. . 3:0 5.0 Embossing 4.0 6.0 Bowling Alley. Alley 1.5 Pins 4.0 Cafe (general illumination only) 2.0 4.0 Cafe (lights on tables) 1.0 2.0 Canning Plants. Pressing Tables 1.0 1.5 Filling Tables 1.0 1.5 Packing Tables (dried fruits) 1.5 2.5 Preserving Caldrons 2.0 2.5 Coffee Roasting at Tables 2.0 3.0 Assorting Tables 2.5 3.0 Packing Tables 1.0 2.0 23 Shipping Rooms 2.0 3.0 Card Room 2.0 3.0 Carpenter Shop 2.0 5.0 Cars. Baggage .7 1.0 Day Coach 2.0 3.0 Dining (general illumination only) 2.0 4.0 Dining (lights on tables) 1.0 20 Mail 5.0 10.0 Pullman 2,0 4.0 Street 2.0 3-0 Church 1.0 2.5 Club. For various rooms, see Bath, Hotel, Residence, etc. Cotton Mill. Receiving and Opening Bales .8 1.5 Opening and Lapping 1.0 2.0 Carding 1.5 2.5 Drawing Frame 1.5 2.5 Roving, Spooling, Ring Spinning, etc 2.0 3.0 Warping 1.5 2.5 Slashing 1.0 2.0 Drawing in 2.0 4.0 Weaving (light goods) 2.0 4.0 Weaving (dark goods 3.0 5.0 Dyeing 2.0 3.0 Dyeing (inspection") 1.5 2.0 Inspecting (general) 5.0 10.0 Courts. Handball 7.0 10.0 Squash 7.0 10.0 Tennis 7.0 10.0 Court Room .. 2.0 4.0 Dairies and Milk Depots 1.0 3.0 Dance Hall 2.0 4.0 Depot (see Station Railway). Desk <0 6.0 Draughting Room 6.0 12.0 Engraving 10.0 12.0 Factory. General illumination only, where additional special illumination for each machine or bench is provided .8 1.5 Local Bench Illumination (fine work) 5.0 10.0 Local Bench Illumination (coarse work) 3.0 5.0 Fire Stations. When the alarm is turned in 3.0 At other times 1.0 Forge and Blacksmithing 1.0 2.0 Foundry 3.0 24 Garage 1.0 3.0 Gymnasium 1.0 3.0 Hall. See Auditorium, Corridor of Hole or Office Building. Hospital. Corridors .5 Wards (with no local illumination supplied) 1.0 3.0 Wards ("with local illumination sup- plied) 5 Operating Table 12.0 20.0 Hotel. Lobby 2.0 4.0 Dining Room (general illumina- tion only) 2.0 4.0 Dining Room (lights on tables) 1.0 2.0 Writing Room 2.0 3.0 Corridor .6 Bed Rooms 1.5 2.0 Lavatory 1.5 2.0 Laundry 2.0 3.0 Library. Stack Room 1.5 2.0 Reading Room (with no local il- lumination supplied) 3.0 4.0 Reading Room (with local illumi- nation supplied) .7 1-5 Lodge Room 2.0 3.0 Lunch Room 2.0 4-0 Machine Shop. Machine Tools (fine work) 5.0 8.0 Machine Tools (coarse work) 2.0 5.0 Buffing and Grinding 2.0 3-0 Bench Work. (See Bench Work). Assembling and Erecting 1.0 3.0 Inspecting 4.0 7.0 Market 3.0 5.0 Moving-picture Theater 1.0 1-5 Museum 2.0 4.0 Office Lighting. Small Offices (officials) 3.0 4.0 Small Offices (desks against walls) 3.0 6.0 General Offices (accounting, etc.).. 4.0 8.0 Opera House. (See Theater) . PaintShop (fine work) 4.0 8.0 PaintShop (coarse work) 2.0 4.0 Pattern Shop (wood) 3.0 5.0 Pattern Shop (metal) 4.0 6.0 Pool Room. (See Billiard Room) . Power House 2.0 3.0 Postal Service 5.0 10.0 Printing. Linotype and Monotype 5.0 10.0 Typesetting 6.0 8.0 25 Composing Stone 6.0 8,0 Matrixing and Casting 2.0 4. Proof Reading 3.0 5. Presses 3.0 5. Paper Cutting, Folding, etc 2.0 4. Public Square .1 .8 Railway Station. Waiting Room 1.5 2.5 Ticket Offices, etc. (See Offices). Rest Room, Smoking Room, etc.... 1,0 2.0 Baggage Room .8 1.5 Concourse 5 8 Train Platforms .5 .8 Reading (ordinary print) 2.0 4.0 Reading (fine print) 3.0 5.0 Residence. Porch .2 1.0 Porch (reading light) 2-0 3.0 Hall (entrance) .7 1.0 Reception Room 1.0 3.0 Parlor 1.0 3.0 Sitting Room 1.5 2.5 Library 2.0 4.0 Music Room 2.0 3.0 Dining Room 1.5 2.5 Dining Room Table (with dome).. 3.0 5.0 Pantry 1.0 2.0 Kitchen 2.0 3.0 Laundry 1.5 2.0 Hall (upstairs) .5 .8 Bed Room 1.0 3.0 Bath Room 2.0 3.0 Furnace Room .4 .8 Store Room .4 .8 Restaurant. (See Hotel Dining Room) Rink (skating) 1.0 3.0 Rug Rack 10.0 20.0 Saloon. (See Bar Room). School. Class Room 3.0 5.0 Study Room 3.0 5.0 Assembly Room 2.0 3.0 Office 3.0 4.0 Cloak Room .7 1.0 Corridor .8 1.0 Manual Training. (See Carpenter and Machine Shops). Laboratory 3.0 5.0 Drawing. < See Draughting Room) Sewing, Hand (light goods) 3.0 5.0 Sewing, Machine (light goods) 4.0 6.0 Sewing, Hand (dark goods) 4.0 8.0 Sewing, Machine (dark goods) 10 15.0 Shipping Room 2.0 3.0 Show Window. Dry Goods Oiigh grade) 15.0 30.0 Dry Goods (ordinary) 10.0 20.0 Dry Goods (smalltown) 5.0 15.0 26 Miscellany (large city) 10.0 20.0 Miscellany (smalltown) 5.0 10.0 Silk Mills. Receiving 1.0 2.0 Winding Frames 2.0 4.0 Throwing Frames 2.0 4.0 Quilling and Warping 3.0 5.0 Weaving 4.0 6.0 Dyeing 2-0 3.0 Dyeing Inspection .15.0 25.0 Finishing 3.0 5.0 Sign. (See Billboard) . Stable .4 1.0 Stamping and Punching (sheet metal) 2.0 5-0 Station, Railroad. (See Railway Sta- tion) . Steel Works. Executive and Clerical Offices. (See Offices). Drafting Offices 4.0 8.0 Machine Shops. (See Machine Shops). Unloading Yards .1 .3 Open Hearth Floors, Soaking Pits and Cast Houses 1 .3 Mould Yard, Skull Cracker Yard and Ore Yard 1 .3 Loading Yards (inspection) 3 .5 Blast Furnace Cast House .3 .5 Rolling Mills 1.0 2.0 Wire Drawing 1.0 2.0 Threading Floors of Pipe Mills 1.0 2.0 Transfer and Storage Bays .5 1.0 Stock Room 5 1.5 Store. Art, (Light on Exhibits) 5.0 10.0 Book 3.0 5.0 Baker 2.0 4.0 Butcher 2.0 4.0 China 2.0 3.0 Cigar 4.0 6.0 Clothing 40 7.0 Cloak and Suit 4-0 7.0 Confectionery 3.0 5.0 Decorator 4.0 5.0 Department (see each department) Drug 2.0 4.0 Dry Goods 4.0 7.0 Florist 2-0 3.0 Furniture 2.0 4.0 Furrier 5.0 8.0 Grocery 2.0 4.0 Haberdasher. (Men's Furnishings) 5.0 7.0 Hardware 2.0 4.0 Hat 4.0 6-0 Jewelry 4.0 6.0 Millinery 4.0 6.0 Music 2.0 4.0 27 Notions 3.0 5.0 Piano 2.0 4.0 Shoe 2.0 4.0 Stationery 2.0 - 4.0 Tailor 4.0 6.0 Tobacco. (See Cigars). Street. Business, (not including light from show windows and signs) .1 .2 Residence 1.1 Telephone Exchange (operators) 2.0 3.0 Theater. Lobby 2.0 5.0 Auditorium 1.0 2.5 Warehouse .5 i o Wharf .1 > Woolen Mill. Picking Table 2.0 4.0 Washing and Combing 3.0 4.0 Carding 1.5 2.5 Twisting 2.0 3.0 Dyeing 2.0 3.0 Dyeing (inspection) 15.0 25.0 Drawing in 2.5 4.5 Warping 3.0 5.0 Weaving 4.0 6.0 Weaving (dark goods) 6.0 8.0 Perching 8.0 15.0 Reflectors for Use with Mazda Lamps. Good illumination not only requires sufficient light but the proper location and equipment of the lamps, in order that such proper distribution and diffusion of light may result, that the eye is able to see clearly and to the best advantage without strain or glare. Mazda lamps, due to their construction, give the greatest amount of light in a horizontal di- rection. Since, in general, the lamp should be located above the line of vision it is necessary to use reflectors to distribute the light properly and direct it upon the working plane. Reflectors may be divided into two general classes, namely, industrial and decorative. These however overlap, as for instance, the prismatic glass reflector, while under the deco- rative class, may be well used in an industrial layout. The industrial reflectors are primarily of metal with reflecting surface of porcelain enamel or aluminum mat, and the decorative reflectors of glass, either prismatic or opalescent. As excellent examples of these types, des- cription is given herewith in brief of several. 28 Industrial. Mazda Mill Diffuser, made by the General Electric Co., Schenectady, N. Y. This is a sheet metal reflector, heavily porce- lain enameled. The metal is of considerable thickness, and the strength of the reflector re- markable, considerable force being required to even bend it slightly. The porcelain enamel is smooth and of several coats, making an excellent reflecting surface. The diffuser is of a flat cone shape with concentric rings to additionally diffuse the light. Fig-. 7 The distribution obtained is excellent for any general illumination in industrial service, as shown from the accompanying curve (Fig. 7) which is the vertical distribution of candlepower of the 100 watt multiple Mazda lamp with MM 12" diffuser, form "H" holder: (a) clear lamp; () clear lamp with MM Diffuser; (c) bowl frosted lamp with Mazda mill diffuser. Practically all of the light flux is in the lower hemisphere with the maximum at about 45. The following sizes are available : 12" diameter 25 to 100 watt Mazda- 16" 100 to 250 ' 21" 250 to 500 ' Holophane D'Oh'er, made by the Holophane Works of the General Electric Co. This is a sheet steel reflector of two finishes: (1) Mat aluminum interior finish with green paint exterior; (2) Porcelain enamel inside and out. The porcelain enamel has these advantages ; it is more readily cleaned resists acid fumes and heat, gives good service in the open and is a slightly better reflecting surface than the alu- minum. The enameling of both the Mazda Mill Diffuser and the Holophane D'Olier reflector is heavy and the metal rigid so that there is no liability of the porcelain being chipped off if hit accidently by the operatives. The Holophane D'Olier reflector is bowl shaped, made to give two distributions with alu- minum finish, namely, extensive and intensive, and for sizes of lamps from 25 to 500 watts. The enamel finish is made to give the extensive distribution only. Fig. The above curve (Fig. 8) shows the distribu- tion of the aluminum finish intensive 100 watt D'Olier reflector with 100 watt Mazda: (a) bare clear lamp: () clear lamp with Holophane D'Olier reflector; (c) bowl frosted lamp with Holophane D'Olier reflector. The D'Olier reflector is also made in the alu- minum finish in the form of an angle reflector, 15-30-45 and 90 for use in localized machine light- ing with the smaller wattage Mazda lamps. Decorative. The Holophane Prismatic reflector is made by the Holophane Works of the General Electric Co. This reflector is typical of the best prismatic glass reflectors, and is applicable for use in offices, stores, dwellings, etc. This reflector is of a scientific design, the prisms being carefully calculated to direct the light in the required directions to give any desired dis- tribution, which makes it the most efficient dec- orative reflector on the market. For distribution curves of these reflectors see pages 31, 32 and 33. The side prisms, besides redirecting the light, serve as a diffusing medium, and allow a small portion of the light to pass through and illuminate the ceiling and side walls. The standard line of Holophane reflectors is made to give extensive, intensive, and focus- 30 Fig. 9 Mazda Lamps. 25, 40 and 60-watt, 100-130 volt, Bowl-frosted, with Intensive Reflectors. Fig. 10 Mazda Lamps. 25, 40 and 60-watt, 100-130 volt, Bowl-frosted, with Extensive Reflectors. 31 . Fig. 11 Mu/,da Lamps. 25. 40 and 60-watt, 100-130 volt, Bowl-frosted, with Focusing- Reflectors. Fig. 12 Mazda Lamps. 100, 150 and 250-watt, 100-130 volt, Bowl-frosted, with Intensive Reflectors. 32 Fig. 13 Mazda Lamps. 100, 150 and 250-watt, 100-130 volt, Bowl-frosted, with Extensive Reflectors. Fig. 14 Mazda Lamps. 100, 150 and 250-watt, 100-130 volt* Bowl-frosted, with Focusing Reflectors. 33 ing distribution, in sizes from 25 to 500 watts. A large variety of spheres, hemisperes. reflector bowls, stalactites, and ornamental reflectors for store and residence use are also made, but space does not permit listing them here. Veluria Reflectors, made by the Holophane Works of the General Electric Co., are typical of opalescent decorative reflectors. They are made the of opal glass, and in two types, the bowl and flared . Opalescent glass reflectors are particularly suited for residences, etc. where the artistic effect is more important than the actual illuminating efficiency. Fig. 15 shows the distribution of the bowl shaped 100 watt Veluria reflector, with a 100 watt Mazda lamp, (a) clear lamp ; (b) clear lamp with Veluria reflector; (c) bowl frosted lamp with Veluria reflector. Fig. 15 As will be seen, a considerable portion of the light is not reflected downward but is diffused through the reflector and serves to illuminate the side walls and ceiling. The Veluria reflector is made in the following finishes: smooth interior and roughed exterior; smooth exterior and roughed interior ; roughed interior and roughed exterior : smooth interior and exterior roughed with design etched upon it. Mazda Monohix. These area decorative art glass reflector made in various shapes and sizes to accommodate thehigherwattageMazda lamps. They are particularly adaptable for the larger rooms in residences, offices, and the higher class stores. Various types of distribution can be ob- - tain ed, depending upon the shape of the reflector. It is made for both the direct and semi-indirect systems of illumination, and is exceedingly ornamental. 34 Distribution curves of any combinations of lamps and reflectors, or other information, may be obtained from the General Sales Office of the Edison Lamp Dept., General Electric Co., Har- rison, N. J. Miniature Lamps The subject of miniature lamps covers a wide range of uses for which the various lamps coming under this heading are employed. The field of decorative lighting demands the use of various sizes of Miniature lamps to bring out the effects in harmony with the decorations with which they are used. Churches, libraries and resi- dences are made more cheerful by the soft glow of candelabra lamps. At Christmas time the house and Christmas tree are safely and artis- tically decorated with various colored lamps. Dentistry and surgery make use of the extreme- ly small lamps which may be inserted in incisions, furnishing light where it is impossible to direct light rays from any other source. The small battery capacity of these lamps makes their use possible under all conditions. The United States Government makes use of a great number of miniature lamps in various instruments, and in the sighting of large guns. Telephone switch- boards are equipped with small lamps, by means of which the operator is signalled by the sub- scriber. In short, the Miniature lamp, in some shape or style, meets almost every demand in the field of small lighting. General Battery Lamps Mazda General Battery lamps are made for use primarily on battery circuits, but they may be used on any low voltage circuit, or in series on circuits of standard voltage. Novelty Battery Lamps Mazda Novelty Battery lamps are used with dry batteries in all kinds of ornamental and portable lighting devices. The Mazda filament emits very little heat, gives a very brilliant light and requires but little battery capacity. These characteristics make it especially desirable for all the lighting devices in which the Novelty Battery types are employed. Lamps 20 Volts and Below The low voltage besides permitting the use of a short sturdy filament in the low volt lamp, pro- vides for the production of low candle-power with low wattage consumption. Automobile and Electric Vehicle Lamps. Electric lamps have two important advantages for Automobile Lighting ; safety and conven- 35 ience. The fact that the foremost car manufac- turers are equipping their cars with electric lights is proof that these advantages are real and not fancied. With the electrically equipped car there is no annoyance in lighting lamps and no fire risk from high pressure gas. A better focus can be obtained with the electric lamp, as the exces- sive heat of a gas flame prohibits the placing of same deep enough in the reflector to use the greater part of the light, while the low heat of the electric light permits its being set back in a deep reflector. Furthermore, the electric head- light is concentrated into practically a po.'nt at the focal center and remains steady and in focus, as it cannot flicker or be blown out of focus by the wind. The interior equipment of a limousine shows the convenience and beauty of electric lamps as applied to auto lighting. The standard voltage adopted by manufac- turers for auto lighting is 6 volts. This low voltage permits the use of a short metallic fila- ment of a comparatively large cross section. The side lights are supplied in G-8 and G-10 bulbs in candle-powers of 3, 4 and 6, and of 3, 6 and 8 respectively. In the P-8 and P-9 bulbs, also used as side lights, the candle-powers are 4 and 6, and 6 and 8. The rear lights are furnished in G-8 bulbs 1-3^ candle-power, and in G-6 bulbs in l-#, 2 and 3 candle-power. The headlight is equipped with a vertical coil filament and furnishes 9, 12, 15 and 18 candle-power in the G-12 bulb, and 15, 18. 21 and 24 candle-power in the G-16-> bulb. It has an effi- ciency of 1 watt per candle. The standardized focal length for parabolic reflectors is \" and the filament mounted in the G-12 or G-16-# bulb meets this requirement. These lamps are fur- nished either with a standard candelabra base or with a bayonet candelabra base. The latter is more generally used, and is recommended be- cause there is no possibility of its jarring out of the socket. For electric vehicle service the General Elec- tric Co. offers a complete line of electric vehicle lamps, ranging from 21 to 65 volts in G-16% (2Vte ' diatn.), and 21 to 90 volts in G-18& (2 5 /i6 // diam.) round bulbs. These are made in 15 and 25 watt sizes and operate at an efficiency of 1.23 W. P. C. Current Supply Systems There are three distinct systems in general use for supplying energy; the storage battery, the 36 generator and storage battery, and the magneto system. With the storage battery system, the six volt battery is in general use, although elec- trically driven machines operate the lights on various voltages, according to the make of the machines. A Ithough it is not practical to operate lights on ignition batteries, the lighting battery when properly equipped can be used for the ignition. With such a system it is good practice for the wiring to be such that the headlights can be switched off and the side lights be left burning while running in the city, and vice versa when running in the country. In the generator and storage battery systems the battery floats on the line and furnishes the energy for the lights when the car is at a stand- still or running at a speed so low that the voltage would otherwise be too low to light up the lamps. When the generator voltage falls below that of the battery the generator is disconnected by a disconnecting switch, making it impossible for the battery to discharge and run the generator as a motor. One of the most successful types, by virtue of an ingenious yet simple scheme of winding, auto- matically regulates the current irrespective of speed variations. That is, when the lamps are turned on, a higher current output from the generator itself is obtained. When the lamps are switched off, the current falls off to a safe charging value for the batteries. The field is compound wound, and is surrounded by a per- manent magnet to prevent a reversal of polarity. Provision can be made for ignition in conjunction with the lighting system. The generator can be driven by gear, silent chain or belt drive. In the magneto system a storage battery must be used as an auxilliary, with a relay or hand operated switch to throw it on when the car is not running. With any generating or battery system it is necessary to have the smallest pos- sible length of wire between the source of energy and the lights, since with so low a voltage a small drop means a big per cent, of the original voltage. Any argument which applies to the lighting of automobiles by electricity applies equally well to motor boats and motor cycles. For the motor cycle the limited space gives the electric head- light an advantage over any other means of illumination. A 3" X 3" X 6", 2 volt, 20 ampere hour battery is generally used, and can be placed in the tool box. Bulbs The shape of the bulb of the regular types is designated by a letter, and the diameter, in eighths ( pf an inch, by a figure following this letter; "P" for pear shape, V 'G" for round and "T" for tubular. For example a G-12 bulb is a round bulb \ 1 A" in diameter; a G -6 bulb is a round bulb %" in diameter. Besides the regular types there are various shaped bulbs for decora- tive purposes and many other special lamps. Bases The standard bases for miniature lamps are the miniature screw b^se and candelabra screw base. The former is W in diameter and 7 /i" long, with 14 threads to the inch, and the latter is Vie" in diameter and 1 %2 // long, with 10 threads to the inch. The Bayonet Candelabra base is furnished for special service, such as automobiles, etc. Sockets and Shades A large line of shades of all colors is supplied for Miniature lamps, which add materially to their decorative qualities. Since shade holders for Miniature Candelabra sockets are not inter- changeable, the style wanted should always be specified. Train Lighting It is needless to dwell upon the advantages of electrically lighted trains. Along with the mod- ern steel coaches the further safety of electrical equipment is essential. Other than immunity from fire, there are added advantages both in convenience and in appearance. An electrical equipment permits the u^e of. berth-lights and any desired distribution of units. The train so equipped with means for making travelling pleasant has in itself a definite advertising value. The Drawn Wire filament of the Mazda lamp, with its low energy consumption, its strength, and its adaptability to any situation, has solved the problem of scientific and eco- nomical train lighting. The round bulb has been generally adopted as a standard for train lighting, as this type har- monizes much better with the general appear- ance of the car. 10, 15, 20 and 25 watt Mazda lamps are supplied in the G-18>2 round bulbs, 2-5/16" in diameter, and a 50 watt lamp in the G-30 round bulb, 3-%" in diameter. 10, 15, 20 and 25 watt lamps are also supplied in either the S-19 bulb, 2-3/8" in diameter, or the S-17 bulb, 2-1/8" in diameter. A 40 watt lamp is supplied in the S-19 bulb, 2-3/8" in diameter, and a 50 watt lamp in the S-21 bulb, 2-5/8" in diam- eter. These lamps are all furnished in two ranges, 25 to 34 volts and 50 to 65 volts. At pres- ent the 15 watt Mazda lamp in the G-18-1/2 bulb is generally used for berth lights, although the Gem lamp in a G-12 bulb, 1-1/2" in diameter is sometimes used in coaches having old fixtures. The Edison Train Lighting lamps are furn- ished with the medium screw base, except the Gem Berth Light, which is fitted with the Can- delabra screw base. Three general systems for supplying current .ire used in train Hghting. They are known as he "Head-End," "Straight Storage" and "Axle Generator" systems. Head-End System The Head-end system consists of a complete power plant, including a steam turbine-driven generator, a storage battery and a switchboard. The generating set is located either in the bag- gage car at the front of the train, or is mounted m the locomotive. When installed in the bag- gage car, steam is supplied from the locomotive ;ither by a direct steam line or through the leating system. The battery supplies current for the lights when the locomotive is disconnected from the train. It also supplies a part of the current \vhen the load is greater than the capacity of the generator set. An additional battery is often nstalled in the rear car so that the rear half of the train will not be in darkness in case an extra car is placed in the middle of the train. The Head-end system is used principally on 'solid trains" where the cars are kept together throughout the entire trip. Straight Storage System In the Straight Storage system, storage batteries are used alone, one for each car. The cells are usually arranged in two sets of 16 each, which, when connected in series, give a voltage range of 57 to 65 volts, and when in multiple, a voltage range of 28 to 34 volts. With the straight storage system, facilities for charging the batteries must be provided at the terminals. Axle Generator System The Axle Generator system consists of a small generator on each car, usually mounted on the truck frame, and driven from the car axle by a belt or chain. A storage battery is also pro- vided for each car to furnish light when the car is not moving. In order to prevent the battery from feeding back into the generator when the train is run- ning at low speed, an automatic switch is used which disconnects the generator from the bat- tery when the voltage of the generator is lower than that of the battery. This automatic switch also connects the generator to the battery when the voltage of the generator rises to the normal value. It is usually designed to connect in at train speeds of about 15 miles per hour. To prevent the generator voltage from rising to an excessive value when the train is running at speeds higher than the "cutting-in" speed, a regulating device is used, consisting of a vari- able resistance inserted in the field of the gen- erator, or a separately driven generator which either bucks or boosts the main generator field. An automatic device is also used to maintain the polarity of the wires from the generator to the battery when the direction of the car's mo- tion is reversed. Automatic variable resistances are used in series with the lamp circuits to maintain a more nearly constant voltage at the lamps. This re- duces the lamp renewal cost by preventing ex- cessive voltage on the lamps, and furnishes steady illumination. Sign Lighting Electric Sign Lighting is simply a part of the immense advertising field, and should be so con- sidered. It should be borne in mind by the merchant, the sign maker and the central sta- tion that an electric sign is first, last and always an advertisement, and its ultimate success de- pends to what degree these facts are borne in mind. Some merchants seem to have the impression that an electric sign is expensive advertising. Nothing is furtner from the truth. When con- sidered strictly as an advertisement and figured on a per capita basis, electrical advertising is the cheapest, as well as the most effectual method of reaching the public. National advertisers are beginning to realize this and are erecting large spectacular displays in the principal cities of this country. As compared with other methods of advertis- ing the electric sign has the following advan- tages: It works both night and day. It has the virtue of continual repetition. It costs less per capita than any other method of advertising. It is brief, concise and right to the point. The impression produced is a lasting one. No turning of pages. No irrelevant matter. Costs nothing to read it. Read by all classes of people. Kindly bear in mind that it is not the object of the electric sign to supplant either newspaper or magazine advertising, as these branches of advertising are closely related, and in order to get the best results all should be used in con- junction with each other. The story is told in detail in magazines and newspapers, and the spectacular electric sign follows with its flashing presentation of the trademark or name of the merchant. To produce the best results, signs should be carefully constructed, for good material and workmanship are very essential. The sign should be erected in such a way as not only to 40 3 oo o Tf e* o a 2i?"s3ss^s UJ .S .appear safe but also to be safe. The signs built by the successful companies are designed on this principle, having a higher factor of safety than would appear to be necessary, so that a failure of any part of the sign is practically impossible. Sign Lamps The Mazda Sign lamp situation has been won- derfully improved by the addition of two new lamps. The General Electric Company is now manufacturing 10 watt, 100 to 130 volt, and 5 watt, 50 to 65 volt Mazda Sign lamps. The ad- dition of these two new lamps makes the sign lamp schedule complete, and there is no logical reason why any merchant should continue to use the inefficient carbon lamps. The use of the Mazda lamps insures more light and better light for less expense than the Carbon lamps. See Table 10 for a complete list of Mazda Sign lamps. 10. TECHNICAL DATA COVERING THE COM- PLETE SCHEDULE OF MAZDA SlGN LAMPS. ltage 10 -13 10 -13 10 -13 50 -65 100-130 10 .33 1.33 1.33 1.5 1.5 1.8 120001100 1 S-14 3.8J200-J100 S-14 3.8 2000:100 3.3 2000J100 6.7 !2000!100 S-14 S-14 Std. Std. :and. As the 10-13 volt sign lamps are made in 1/2 volt steps, the voltage of the lamps to use would be the nearest 1/2 volt obtained by dividing the circuit voltage by 10. As an example, suppose the circuit voltage in a particular case is 113; by dividing 113 by 10 we get 11. 3, and hence we should use 11.5 volt lamps in this case. With the 50-65 volt and 100-130 volt lamps, the voltage to be ordered should be obtained by testing the vol- tage directly at the lamp sockets In case of voltage fluctuation the maximum value should be used. It has been demonstrated time and time again that when operated properly Mazda Sign lamps give satisfactory results. In order to avoid mis- understanding in the future each method of wiring will be taken up separately. Mazda Sign wiring, as experienced by the Cen- tral Station and merchant, may be divided into two broad classes: First, Cities having direct current. Second, Cities having alternating current. On the opposite page is given in tabulated form the methods of wiring and types of lamps to use -on direct current. 42 For Cities Having Direct Current Size of Sign Voltage Wattage Lamp to Order Under 100 10-13 2.5,5, 10 in series Series Over 100 10-13 2.5,5, Multiple series Series Any number 50-65 5 2 in series Series " " 100-130 10 Multiple Multiple 10 in Series It will be noted in the above table that the series method of wiring with 10 lamps in series (Fig. 16) is only recommended where the sign con tains less than 100 lamps. Under no condition should a sign containing, say 300 or 400 lamps be wired in straight series, as unsatisfactory per- fcrmancewill probably result. It is recommended that in every case 10 lamps be wired in each series, the voltages of the lamp being one-tenth of the circuit voltage. As the same current flows through all the lamps in each series, it is neces- sary that the lamps be selected for amperes. This is done by the lamp manufacturers, and all lamps so selected have an additional label reading SERIES BURNING. Do not operate lamps of different manufacture in the same series, because the different manufacturers select their series lamps according to different schedules, and hence by mixing them unsatisfactory performance will result. Fig. 16 Multiple Series When a sign contains more than 100 lamps, and it has been decided to use 10-13 volt lamps, it is recommended that they be wired in mul- tiple series (Fig. 17) with 10 multiple banks con- 43 nected in series. If it is decided to wire less than 100 lamps in this manner it is recommended that enough resistance be inserted to make the total resistance equal to that of 100 lamps. As series lamps are selected for volts and amperes, it is evident that they should be used for this class of service and the order should so specify. -o 0< K -0 o- -0 -o-> -o o -o^ o- -0-. -o o- -0 -o -CH -On -o- -o -o- -o -o- OH -o -o- o- -o -o- -o- -0 On -0 -o- 1 - -o- -o -o -o- -o -o- -o- -o- - -o - Fig. 17 When the lamps are so wired that the failure of one lamp in a multiple bank causes the re- maining lamps to be operated at an excess volt- age, it is suggested that all burn outs be promptly replaced. Therefore, when a sign is wired in this manner it should be easily access- ible so that any lamp which has failed can be re- placed promptly and conveniently. 50-65 Volt, 5- Watt Mazda Lamp This lamp has recently been standardized and it is a long step forward in the series sign lamp proposition on direct current. These lamps may be wired, either two in series (Fig. 18) or in mul- tiple series (Fig. 19.) When wired two in series, it Fig. 18 is suggested, that the lamps be staggered so that the failure of one lamp will not throw out two ad- jacent lamps. In the case of a double face sign it is recommended that the lamps on each side be wired in multiple and the two sides be con- nected in series. In this way we get a condition of operation which is practically similar to 44 straight multiple, as when approximately 50 amps are used on a sign, the failure of one lamp will not unbalance the circuit to any appreciable extent. Service Wires Fig. 19 100-130 Volt, 10 Watt, Mazda Lamp This new sign lamp makes it possible to wire the signs in straight multiple, (Fig. 20) this be- ing the most simple and satisfactory method of wiring in practice. This lamp makes it possible to eliminate transformer expense, and thus helps to offset the slightly higher renewal cost of the lamps. It is possible to replace any exist- ing 30-watt or 20-watt Carbon lamp by this lamp, without any rewiring, to show a material sav- ing to the customer, and at the same time greatly improve the appearance of his sign. o- 2 SL 5 5 ^> o- G- 4 5 5 5 5 Fig. 20 For Cities Having Alte mating Current 11. TABLE SHOWING THE LAMPS AND METHODS OF WIRING TO USE IN CITIES HAVING ALTER- NATING CURRENT. SizeofSign Lamps Method of Wiring Lamp to Order Voltage Wattage Any Size Any Size Any Size 10 -13 50 -65 100-130 2.5,5 5 10 Multiple, trans, two in series Multiple Multiple Series Multiple 10-13 Volt Lamps Since the multiple method (Fig. 20) of oper- ating lamps is always the best, it is recom- mended that a transformer be used whenever alternating current is available. The trans- former expense is justified since the best possi- ble performance is secured by its use. 50-65 Volt, 5 Watt Lamp This lamp will operate just as satisfactorily on alternating current as on direct current, and the same methods of wiring should be employed in both cases. 100-130 Volt, 10 Watt Lamp This lamp can be operated on alternating cur- rent with the same success as on direct current. Its use simplifies both the wiring and operation. Wiring For low voltage Mazda Sign lamps the wiring must be such that the voltage drop does not ex- ceed a certain definite amount, and that the Fire Underwriters' Rules are not violated. Ac- cording to the specifications of the National Board of Fire Underwriters not more than 1320 watts shall be dependent upon the final cut-out. In some cases, however, the municipal rules allow only 660 watts, and this ruling must be observed and the wiring governed accordingly. Below is a table which shows the carrying ca- pacity of wires as approved by the National Board of Fire Underwriters. It is seen from this Table that with low voltage Mazda lamps the carrying capacity of the wires is the govern- ing feature. 12. CARRYING CAPACITY OF WIRES B &S Gauge Rubber Insula- tion Amperes No.Swatt 10-13 Volt Lamps No 5 watt 50-65 Volt Lamps No. 10 watt 100-130 Volt Lamps 14 12 10 8 6 5 4 3 2 1 12 17 24 33 46 54 65 76 90 107 127 27 38 54 75 104 122 147 172 204 242 J 127 181 256 I 1 t Exceeds the 1320 watts as allowed by Na- tional Board of Fire Underwriters. With the 10-13 volt lamps it is essential that the voltage drop in all cases be less than % volt. Table 13 gives the number of lamps which can be used on the four different sizes of wire when the 13. SHOWING RELATION BETWEEN NUMBER OF LAMPS, SIZE OF WIRE, SPACING AND VOLTAGE DROP. Spacing of Lamps in Inches Size of Wire (B & S) 14 .12 10 8 6 8 10 12 16 20 64* 55 47 42 38 33 29 92* 70 60 54 49 42 38 125* 88 75 68 62 54 48 159* 112 97 86 79 68 61 Number of Lamps 14. NUMBER OF LAMPS, SIZE AND LENGTH OF FEEDERS , Combined length of pair of feeders. Size of Feeder (B & S) 10 8 6 4 2 3 64* 92* 130* 184* 262* 4 50 77 125 184* 262* 5 40 62 100 158 254 6 33 53 84 135 210 Number 8 25 40 63 101 160 of 10 20 31 50 79 127 Lamps 15 13 21 33 53 85 20 10 15 25 39 63 30 7 10 17 26 42 * This limit imposed in order not to exceed the safe carrying capacity of weather-proof wire. With the 50-65 volt, 5 watt, and 100-130 volt, 10 watt lamps, since the amperage is very small the governing feature will be the limit of 1320 watts imposed by the National Board of Fire Under- writers. Sign Lighting: Transformers. The General Electric Company has developed a complete line of transformers for reducing the circuit voltage to that of Mazda sign lamps. The transformation ratio is 10 to 1 and 20 to 1 . and con- sequently with a primary voltage averaging 110, 11 volt lamps should be used and with primary voltage of 120, 12 volt lamps should be used, etc. These transformers are made in four standard sizes, as shown in Table 15. As the secondary can be connected for either two or three wire service, the transformers can, therefore, be applied to any sign without neces- sitating a change in wiring. 47 15. G. E. Sign Lighting Transformers. Capacity Waits Capacity 5-watt Lamp Wall Space Inches Depth Inches Net Weight Pounds Catalog Number 250 500 1000 2000 50 100 200 400 7x6* 8x8 9x9 lOKxlO 5% 7K 9 10 30 45 70 100 76676 76678 76680 76683 Flashers. The flasher has three advantages; it gives movement, which attracts attention, enables one to secure spectacular effects, and reduces the amount of current necessary to operate a given sign. To prevent arcing and also because most flashers are designed to operate on 110 volts, it is recommended whenever possible that the flasher be placed on the service side of the transformer. However the simple on and off flashing sign is the only type that can be so ar- ranged because the several circuits of a com- plicated sign must be brought together at the flasher and cannot be united in the transformer on the way. In Table 16 we have given the various kinds of flashing effects with the corresponding possible methods of wiring on either direct or alternating current. The type of lamp which can be used in order to produce these flashing effects is shown in the last column. 16. TABLE SHOWING THE POSSIBLE SYSTEMS OF WIRING AND LAMPS TO USE FOR VARIOUS FLASHING EFFECTS : Flashing Effect fMult. A.C. | or J Mult. Series rj) c I Ten in series One line I ( Two " atatimej A.C. Flashing Effect Script Spelling Fountain Current Wiring Steady Burning On and Off Lamps 110 V. Mazda 10 V. 10 V. 55V. " Mult, with Trans. 10 V. Current Wiring Lamps Multiple 110 V.Mazda I A.C. , j Multiple ' A.C. ^with Trans. 10 V. Mazda 1 D.C. or _ A.C. Rat Chaser Falling Water . Lightning J Tn order to estimate approximately the number of lamps which will be required for any sign, the following table is given which shows the average number of sockets for different sizes of letters 48 Average Number Sockets for Different Size Letters 12"-. 14 "... 16 "- 24 ".. 36"... 48"-., 60"... 72"... 84"... ..20 -.24 -.27 96" 32 108" 36 120" 1 39 In Special designs a space of 5 " between cen- ters of sockets can be used for estimating the number of receptacles. 1 2 3 4 5 6 7 8 9 10 11 12 Rate per Kw.-hr. in Cents Fig. 21 Fig. 21 shows the approx. total operating costs ?n\ corres P ndin8: cart >on and Mazda sign lamps The decided economy of the Mazda lamps is clearly shown. These curves are based on stand- ard package prices in effect June 1, 1912. 49 Street Lighting During the last few years remarkable ad- vances have been made in the standard of illumination required for street lighting. The introduction of Mazda Street Lighting Lamps has undoubtedly been one of the most note- worthy advances along this line. With the in- creased economy and effectiveness insured by their use, the benefits of electric street lighting are now practically applicable to all classes of service in either large or small cities. They have for the first time made it commercially possible to operate satisfactorily both arc and incandes- cent units in series on the same circuit, thus pro- viding the most flexible and efficient system of street lighting ever devised. This system allows a wide selection of candle power sizes so that by distributing both Mazda and Arc Lamps where they will do their best work, a very effective and economical arrangement can be obtained, which eliminates much of the dissatisfaction inherent in former systems of lighting. Moreover the conditions of the present day differ greatly from those of the past ; greater crowds are on the street in the evening; high speed vehicles are more generally used; the commercial value of good lighting is realized by a larger per cent, of busi- ness men ; the scientific principles of streetlight- ing are better understood, and above all there has been a decided gain in the efficiency and economy of lighting units. These conditions re- quire that both city and country roads be much better illuminated than was formerly possible without an excessive expenditure of money. The problem of meeting the above conditions is solved by the Series Mazda system. The ad- vantages <>f this system may be briefly summar- ized as follows : 1. The Series Mazda system effects a great saving in copper and energy transmission losses on account of its comparatively high line voltage. 2. The Series Mazda system has a very low maintenance cost per unit on account of the ex- tremely long life of the Mazda lamp, its high energy efficiency and the very slight amount of attention required during life. 3. Series Mazda lamps will burn under a great variety of conditions and are absolutely unaffected by external surroundings or weather conditions 4. Series Mazda lamps are made for many different current strengths, thus allowing the selection of that value of current which is most economical under the local generating and trans- mission conditions. 5. Series Mazda lamps are made in many dif- ferent sizes, and, as all operate at a high effi- ciency, that size unit can be selected which will give the desired amount of light most economic. ally, or where the appropriations for street lighting increase slowly, the standard of illumi- nation can be increased accordingly. 6. The Series Mazda system allows several different size units to be connected to the same circuit, and an easy method of changing either temporarily or permanently the amount of light at any spot. 7. Series Mazda lamps have a low intrinsic brilliancy and thus reduce glare to as low a value as is compatible with economy. 8. A Series Mazda system permits standard' ization of equipment, interchangeability of parts, and lighting of an entire city from the same or similar circuits. 9. The Series M azda system offers a simplicity and ease of operation and control unsurpassed by any other system. 10. The Series Mazda system utilizes to the highest degree all the light rays from the lamp units, even when the streets are narrow, crooked, hilly or lined with shade trees. 11. The Series Mazda lamps when equipped with radial wave reflectors increase by about 25% the maximum intensity of light at the angles near the horizontal, thus throwing the greatest amount of light out to the distant points. 12. The Series Mazda lamps have a color value very near to that of daylight, thus giving objects their normal appearance. Equipment With a Series Mazda system all the lamps are designed for the same current flow, and there- fore soms method is necessary for holding the current in the circuit constant. For this purpose a transformer has been especially designed by the General Electric Company which changes the nearly constant impressed voltage to con- stant secondary current. This transformer has been so well designed that it holds the second- ary current within 1/10 of an ampere of its nor- mal value from no load to full load, even with a 5% variation in impressed voltage. This trans- former gives a closer regulation , higher efficiency and a better power factor than any other con- stant current regulator, and at the same time by keeping the primary and secondary Circuits sepa- rate, protects the generating equipment from any accidents due to grounds or short circuits on the distributing lines. The series socket and cut-out is very necessary for the successful operation of a series system, and is designed for two special purposes; first, to short-circuit the lamp automatically when the filament fails, and second, to permit the removal of the lamp from a live circuit without inter- rupting the service. For general purposes all streets may be di- vided into four classes : 1. Principal business streets. 2. Important cross streets and boulevards. 3. Residence streets. 4. Outlying districts. In every one of the above divisions the Mazda lamp can be used so as to economically give an abundance of light, and in most cases at a cost less than that for any other type of illuminant. Where a high intensity of light is desired, units of about 200 or 350 candle-power should be used, but in the majority of cases a smaller size lamp will be found more suitable. With the smaller lamps, spaced more frequently, more uniform illumination is obtained, less glare is experienced and the general lighting effect is much better. If we have a certain minimum intensity on the street and desire to keep this value constant, but to double the distance between lamps, then we find that the new light unit must be at least four times as powerful as the old ones; con- versely, if we decrease by half the distance be- tween lamps and keep the same minimum illumi- nation our new light sources need be only one- fourth as powerful as the original lamps. It will therefore be seen that the saving in energy in- creases very rapidly as we decrease the size of the lamps and their distance apart, while at the same time maintaining the same minimum in- tensity of light. Consequently the Series Mazda lamps are the most economical illuminant for streets where a uniform low intensity of light is desired. Upon the principal business streets the illumr nation should be of a character, both in bright- ness and general appearance, to bring credit to the city. For this class of street lighting the Mazda lamp, whether in multiple or series, has been a popular illuminant. The best results have been obtained from posts placed opposite one another on each side of the street, at a dis- tance apart slightly greater than the width of the street. Five lamps per post are commonly used, enclosed in a diffusing globe, and of a size to give approximately 10 watts per running foot of street. It is also the practice to use combina- tion trolley lighting poles, where an agreement can be reached between the trolley and lighting company. In other towns where the ornamental feature is not desired, 350 C. P. Mazda lamps should be used, and equipped with a 24" Radial Wave reflector. These lamps should be placed from 20 to 25 feet above the ground, and about 100 feet apart. Upon the important cross streets and boul- evards either one-light ornamental standards can be used, placed at the sides of the streets, or lamps suspended from brackets, and equipped with Radial Wave reflectors. In each case the lamp should be placed at the side of the street so as to reduce the glare, for the foliage often 52 requires a low suspension of the lamp. Where the foliage does not interfere with the distribu- tion of the light the lamp should be placed from 15 to 20 feet above the ground. The lamps commonly used are the 60 and 100 C. P. Upon the residence streets the lamp is usually suspended at the side, as it is less expensive than the center suspension, and gives sufficient il- lumination over all the street, except where same is unusually wide. The most common equipment consists of either 40, 60 or 80 C. P. lamps, equipped with 20" Radial Wave reflect- ors, and placed from 15 to 18 feet above the ground. In the outlying districts the character of the lighting depends on the amount of money avail- able for this work. The 32 and 40 C. P. lamps are generally used and placed about 15 feet above the ground. Staggered placing of units is seldom advisable in street lighting, as it makes the outline of the road less distinct, especially where there are curves. Rating of Lamps Owing to recent improvements in lamp manu- facture it is now possible to supply series lamps for a definite amperage rather than for an am- pere range, as has been the practice heretofore. This improvement has been long striven for, as it permits the central stations to use one current value on their series lines and thus make all their apparatus interchangeable. It is to the advantage of the central stations, there- fore, that in all new installations they adopt a standard ampere value, preferable 6.6, and also that they change their present lines to the near- est standard current value. The standard amperages are as follows : Ampere Range of Standard Ampere Lamps Used in Lamps to be Used the Past in Future 3.0 to 3.8 3.5 3.8 to 4.3 4.0 5.1 to 5.9 5.5 6.1 to 6.9 6.6 7.0 to 8.0 7.5 Mill Lighting In mill work the quality of illumination plays an important part in the efficiency of production. In a well lighted mill the actual operating hours may be increased, thereby increasing the out- put, while the fixed charges remain the same- Spoilage has proven to be the chief obstacle to economical production in mill work. Census experts claim that 25% of the total spoilage can be avoided by good illumination. The employee, considered as a unit with his machine, works at least 2% more efficiently under good than under 53 poor illumination. Furthermore, the employee of several years' service, will, by virtue of his long training, be highly efficient, provided his eyesight has not been injured by working under poor illumination. An investment in a good lighting system is a good insurance against lia- bility for accident. This is borne out by statis- tics, which show that the greatest number of industrial accidents occur in those months which average the greatest number of hours of dark- ness and gloom. The effect of well lighted surroundings upon the employee is also a consideration not to be neglected. No far sighted mill man would cut off his heat supply during the winter months to reduce his operating expense. The same should be said about his illumination, as a man whose mill is well illuminated removes by several de- grees the likelihood of labor disturbances. The General Electric Company has a complete line of information covering any class of lighting service. A request for advice on any phase of lighting service will secure a Bulletin giving a review of conditions to be met with, and recom- mendations for securing the best results. Recom- mendations for the lighting of Textile Mills are given below, and in the table beginning on page 23 will be found the intensities recommended for various other classes of lighting service. Recommendations Cotton Processes OPENERS. One 40 watt Mazda lamp with extensive Holophane D'Olier reflector over each end of machine. PICKERS. Same as Openers. CARDING. One 40 watt Mazda lamp with extensive steel reflector, per machine staggered. DRAWING FRAME. One 40 watt Mazda lamp with extensive D'Olier reflector, spaced 8 feet. ROVING FRAMES. Two 40 watt Mazda lamps with extensive reflectors in aisle, spaced 7' to 10'. RING SPINNING. Two 60 watt Mazda lamps with extensive reflectors in aisle, spaced every 100 spindles on each side of alley. TWISTING. Same as Ring Spinning. SPOOLERS. Two 60 watt Mazda lamps with extensive reflectors in aisle, spaced 7' to 10'. 54 WARPING. One 60 watt Mazda lamp with extensive re- flector over beam. One 60 watt Mazda lamp with intensive re- flector over or inside rack. General illumi- nants when warpers are movable. SLASHER. One 40 watt Mazda lamp with expensive re- flector at each end of the machine. DRAWING IN. General illumination in portion of mill for drawing in furnished by 40 watt Mazda lamps, with extensive reflectors, spaced 10 centers. Supplemented by special lights on each stand. WEAVING. Looms for light colored goods up to 42 // , one 60 watt Mazda lamp with extensive reflector, at center of square formed by four machines. Looms for 54-72 inch goods, one 60 watt Maz- da lamp with extensive reflector at each end of machine in weaver's alley. INSPECTING. One 60 watt Mazda lamp with intensive re- flector over each table. PACKING AND SHIPPING. General illumination, 100 watt Mazda lamp with extensive reflector hung 12 feet above floor, spaced about 15 to 18 foot centers. Silk Processes WINDING FRAMES AND THROWING FRAMES. Three 60 watt Mazda lamps with extensive reflectors, placed in aisle, spaced 7' to 10'. QUILLING. Two 60 watt Mazda lamps with extensive re- flectors in aisle, spaced 5' to 10'. WARPING. One 60 watt Mazda lamp with extensive re- flector over creel. One 60 watt Mazda lamp with intensive re- flector over reed. One 60 watt Mazda lamp with extensive re- flector over reel. WEAVING. One 60 watt Mazda lamp with intensive re- flector over lay of loom. One 40 watt Mazda lamp with extensive re- flector in rear alley. FINISHING. One 60 watt Mazda lamp with intensive re- flector over each table. PACKING AND SHIPPING. 100 watt Mazda lamp with extensive reflec- tor, 12 feet high, spaced 15'' to 18'. 55 Woolen Processes PICKING TABLE. One 40 watt Mazda lamp with intensive re- flector over each table. If tables are placed back to back, one 60 watt Mazda lamp with extensive reflector. WASHING. General illumination, 100 watt Mazda lamps with extensive reflectors. 12' above floor, spaced 10' to 12'. COMBING. General illumination, 100 watt Mazda lamps with extensive reflectors, 10 to 12 feet hig'h with 10 to 12 foot centers. CARDING. One 40 watt Mazda lamp with extensive re- flector per machine staggered. TWISTING. 40 watt Mazda lamps with extensive reflect- ors, 7' above floor in aisle, 7' to 10' centers. DYE HOUSES. Illumination can be greatly improved if ven- tilating fans are used to draw off steam. Place one 100 watt Mazda lamp with exten- sive reflector between every other tank. Raw stock dyeing machine, one 60 watt Maz- da lamp with extensive reflector in front of each machine. Skein and slubbing dyeing machines, one 60 watt Mazda lamp with extensive reflector in front of each machine. DRAWING IN. General illumination in portion of mill de- voted to drawing, in 60 watt Mazda lamps with extensive reflectors spaced S / centers. WARPING. 60 watt Mazda lamp with extensive reflector over reel. 60 watt Mazda lamp with inten- sive reflector over reed. WEAVING. One 60 watt Mazda lamp with intensive re- flector over lay with 36" goods. Two 40 watt Mazda lamps with intensive re- flectors over looms weaving 54" goods. One 40 watt Mazda lamp with extensive re- flector in rear alley. (If black cloth, use 100 watt Mazda lamp for 36", and two 60 watt for 54" goods) . PERCHING. One 100 watt Mazda lamp with intensive re- flector over each perching frame. If perch- ing frames are portable, by general illumina- tion with 150 watt Mazda lamps with exten- sive reflectors, !(/ to 12' above floor, spaced 56 12' to 15' centers; if dark cloth is perched, 250 watt Mazda lamps, 15' to 18' centers. PACKING AND SHIPPING. Same as above. Knitting KNITTING RIB, TOP, SHIRT BODY, AUTOMATIC SEAMLESS AND COLOR STRIPER. Machines generally placed in groups, one 60 watt Mazda lamp with extensive reflector to every four machines. FLAT KNITTERS. Place 60 watt Mazda lamps with extensive reflectors in aisle, spaced 6' to 8' centers. LOOPING AND SEAMING MACHINES. FINISHING MACHINES. One 25 watt Mazda lamp with anchored re- flector, hung 12" above table and 18" from head of machine. NAPPER MACHINES. One 40 watt Mazda lamp with extensive re- flector over the front roll. General Information on Incandescent Lamps History of the Incandescent Lamp The first commercial incandescent lamp was introduced by Thomas A. Edison in 1879. The filament was horseshoe shaped and was made of carbonized paper. The essential parts of the lamp were the same as those of the lamp of the present day. The efficiency at which the lamp operated was about 7 watts per candle. Later the efficiency was increased to 5.8 \vatts per can- dle by the adoption of a carbonized strip of bamboo. This increased the total life of the lamp, yet the candle-power declined approxi- mately 20% in the first 100 hours. Further im- provement in 1881 increased the efficiency to 4.6 watts per candle. The present carbon filament is made by dissolving absorbent cotton, forming a thick viscous solution, which is forced under pressure through a die, forming a long thread- like filament, which is then carbonized. The efficiency of the present carbon filament is ap- proximately 3.1 watts per candle. The next important step in the development of the incandescent lamp was the "metalliza- tion" of the Carbon filament. This was placed on the market as the Gem lamp by the General Electric Company. The Gem filament is pro- duced, by heating the ordinary treated Carbon filament in an electric furnace to a very high temperature. The cold resistance of the fila- ment is considerably reduced by this heating, and the temperature coefficient is changed from negative to positive. This improvement is shown in the resistance curves on page 73. The re- fractoriness of the filament is increased suffi- ciently to permit its operating at a temperature some 200 higher than the carbon filament for the same deterioration. The most important advantage is the increase in efficiency, the Gem lamp operating at 2.5 watts per candle as com- pared -with 3.1 watts per candle for the Carbon. The Tantalum lamp was placed on the market in 1906. It had an added efficiency over the Gem, operating at 2 watts per candle. As the Tantalum lamp gave rather unsatisfactory ser- vice on alternating current it has given way to the more efficient Mazda lamp. The metal tung- sten of the Mazda, filament has a high melting point, and high vaporizing temperature. These qualities are essential to a good filament. The tungsten filament is also a poor radiator of heat, and accordingly operates more efficiently than the Carbon filament. The high efficiency of the 58 O, I o a 3a e E I O* M *fs r ^ > SO O a *- a. S I i s * I i *? f/\ D |5? 8f<, ^ . -0 OC * *|J ,_; CM _J Tungsten Pressed Filament Lamp 1908 >o o S llU % g CM CT -H ^2 O rH CM *" -2fo O CO CM O CO O S g CM O VO O O rH CM B fgl ,_( t^ O IO VO c^ SS ^ S CO O ^ - 2 3 g * 6 CM VO &0 MJ el 8 Jfl ^ 10 ^ N 2 3 5=5 3 18 g CM v: o CO i-4 O r-i CM 3 CO c3 1 i) 43 (H 0) a SH > ^-> ft o s < 4J Ifl ^o o 2 00 | 1 o i! pj 10 3 o o ^ & !- SSI i.fli | o o o fa fa h ^ be t, t -Jf J-l v ^ * Efficiency in Voltage Ran Candle Powe Candle Powe .S3 o 6 |^ Cost per 1000 Candle-hours of light 59 Tungsten filament is further due to selective ra- diation as defined on page 2. The average effi- ciency of the pressed filament Mazda lamp was about 1-23 watts per candle, with a life of 1000 hours. Pure tungsten metal has a very bright steel gray appearance, is very heavy, having a spe- cific gravity of 19 12, and until recently was pro- duced only in a brittle form. Recently improved methods of manufacturing tungsten into wire made it possible to produce the drawn wire Maz- da lamp. The possibility of producing tungsten wire in great lengths has permitted a change in the construction of the lamp, by which a con- tinuous filament is employed, instead of welding four or five filament loops together, as was done in the past. This new construction furnishes a lamp ihat is many times stronger than the pressed filament. This lamp operates at an av- erage efficiency of 1.15 watts per candle with a life of 1000 hours. The temperature of the Mazda filament reaches about 2300 Centigrade when operated at 1 watt per candle, and between 2100 and 2200 Centigrade when operated at 1.25 watts per can- dle. The filament has a high positive tempera- ture coefficient so that a remarkably steady candle-power is obtained over a comparatively wide range of voltage. This is shown by the curves on page 71. Due to the high positive temperature coefficient the current density re- mains fairly constant insuring a uniform life. Etching and Frosting Etching The process of etching lamps with names, letters, symbols, etc., is simple and inexpensive, out when done by the manufacturer will cause delay in shipment, as it specializes every order. The following instructions will enable customers to etch their own lamps, but it should be borne in mind that the solution described will not give satisfactory results for frosting: Mix in a small lead or rubber cup a good grade of hydrofluoric acid, and crystalline ammonium carbonate until the acid is partly neutralized. This can be determined by a test; if too little of the carbonate is present, the etching is more of a transparent eating of the glass. To obtain clear cut letters or symbols, spread a little of the acid on a rubber pad with a tooth brush, or some- thing similar, then spread the solution on the rubber stamp to be used, taking it from the pad with a brush. Ordinary blotting paper may be used to remove an excess of acid from the stamp. Now take a lamp and apply the rubber stamp to the part to be etched ; this part of the lamp, pre- vious to applying the stamp, should be heated 60 over an ordinary gas flame to a temperature that will render the lamp uncomfortable to the touch. A gas heater can be made of a per- forated strip of sheet iron, arranged so that a tray of about 50 lamps can be placed on top of it with the base or tip of the lamp down, so as to heat the part to be etched. Be sure to return the etched lamps to the tray for reheating, as this gives better and quicker results. Frosting The term "frosted" lamp is used to describe a lamp with a frosted or etched bulb. Lamps may be permanently frosted by either sand- blasting or acid etching, both processes giving results so similar that it is difficult to distinguish them. The acid method is used entirely in the frosting of Edison lamps. Although the mixing of the etching paste is comparatively simple, it is dangerous to handle and difficult to secure good results. For this reason it is not advisable for customers to do their own frosting. The regular acid frosting is applied to Carbon, Gem and Miniature lamps of all classes. The "satin finish" frosting is used on regular mul- tiple Mazda lamps. This is a more expensive operation, and is known as the German process. The solution is more or less a paste. Lamps are dipped in the paste, allowed to stand for some- time, and are then rinsed in water. The finish is smooth and satin like. The principal styles of frosting are "bowl" frosting, "full" frosting and "bulls eye" frosting. In full frosting the entire bulb is frosted. In bowl frosting only the lower part or the bowl of the bulb is frosted. In bulls eye frosting the whole bulb is frosted, excepting a clear spot 2 inches in diameter. This type of frosting is sometimes used for stereopticon lamps. Colored Lamps Colored lamps can be supplied with bulbs made of either clear glass superficially colored or of natural colored glass. Superficially colored bulbs are bulbs which have had a dipping or coating of color applied to their exterior surfaces ; their color is not weather proof. Natural colored bulbs are bulbs made from permanently colored glass ; their color is weather proof. The Best Lamp The fallacy of the contention that the lowest price lamp is the best lamp lies in the assumption that a lamp's value is measured solely by its first cost, instead of by its ultimate cost. The first cost or price of a lamp is but a fraction of its ultimate or true cost, and completely ignores useful life, efficiency and cost of power, which are the most important factors of a lamp's cost. 61 To illustrate what a small percentage the first cost is of the ultimate cost and to set forth its incorrectness as a standard of lamp value let us assume that a carbon 50.0 watt, 2.97 w.p.c. lamp has a useful life of 700 hours, that its price is 16c, and that power costs 5c per kilowatt-hour: Then 50 x 70 - 35.00 kilowatt-hours. 1000 35.00 X .05 = $1.75 or cost of power Price of lamp = .16 Therefore $1.91 equals ultimate cost of lamp But Price of lamp _. ^16_ = Qi084 Ultimate cost of lamp 1.91 or 8.4 per cent. Therefore while the first cost of the lamp at this life and efficiency is but 8.4 per cent, of its ultimate cost, the cost of power is 91 per cent, of its ultimate cost or nearly 11 times the price of the lamp. Is the best lamp the lamp that lasts the longest or gives the longest actual life? Let us consider: The actual life of a lamp fails not only to com- prise the important factors in lamp service of useful life, efficiency and cost of power, but ignores also the price of the lamp. Therefore, the actual life can be no criterion of a lamp's quality. Besides, experience demonstrates that long actual life is usually attained only at the expense of candle-power and efficiency. Lamps are made for the twofold purpose of giving light and life, not mere life alone, but useful life life with candle power. We therefore conclude that the best lamp is not the lamp that sells at the lowest price nor the lamp that lasts the longest, but is the lamp whose ultimate cost is the lowest, i.e., the cost of the lamp and the cost of power: or with equal price and economy the lamp that gives the longest useful life. It is a fact demonstrated by test and practical experience that the Edison Gem and Mazda lamps surpass any and all makes in these desir- able qualities. Compared with the products of other manufacturers they are, therefore, the cheapest lamps to use, although the prices are not always the lowest. That they alone are en- titled to the distinction of "best" is shown by the claims made for other lamps that they are "as good as the 'Edison,' etc." Characteristics of the Best Lamp The best lamp has the following distinguish- ing features: a Absence of physical defects. b Correctness of rating. c Uniformity of performance. 62 d Maintenance of candle-power. e Low ultimate cost of operation. Edison lamps are carefully inspected after each step in their manufacture and are then subjected to a rigid final inspection before being sent out. The lamps are carefully tested and selected to give the proper ratings. It is not sufficient, however, that lamps ini- tially meet all requirements; they must also, after installation, give uniform useful life, and during that life afford uniform candle-power and consume uniform watts or power; thereby ren- dering that uniform and definite lamp service which is so essential to good lighting. Uniform useful life makes possible the adoption of a sim- ple and effective system of lamp renewals and also serves as an excellent index of the efficiency at which the lamps are operated. Uniform candle-power precludes unsatisfactory light con- trasts and insures even illumination. Uniform- watt or power consumption prevents complaints of excessive and uncertain meter bills: it elimi- nates the question of allowance to customers which is an undesirable source of friction and is the result of unsatisfactory and expensive lamp service; and it also insures stations which sell light by contract against loss due to excessive wattage or power consumption for which there is no pecuniary return. An ideal lamp would be one that maintained its initial candle-power throughout its life. So then, other conditions being equal, the best lamp is the lamp that at a definite w.p.c. maintains its candle-power for the longest time, or the lamp that gives the best useful life. In conclusion, it pays most decidedly to use carefully selected lamps, because the saving to the lamp user is worth many times the saving in first cost of a few cents which the care- less and incompetent lamp manufacturer offers as an inducement to use his lamps. The amount paid for the extra wattage consumption of an inefficient lamp during its useful life is often six or seven times the first cost saving. It costs the careful and competent manufacturer much money to inspect his product rigidly and hon- estly, to test and select his lamps carefully, and to weed and cull out the imperfect ones. The user has the choice of wisely paying the full price for reliable results or of buying on price only, and of paying far more finally through failure, breakage and increased consumption of power. Cleaning Mazda Lamps. Where no regular provision is made for clean- 63 ing lamps, it is safe to say that the lighting would be increased 15% by the introduction of such service. With monthly cleaning the average loss of light due to dust will in most cases be only 2 or 3%. For a 100 watt unit burning 1000 hours, per year with energy at 10 cts. per kw-hr. the total operating cost will be about $12.00 and 15% of this is $1.80. The cost of cleaning this lamp monthly will amount to from 25 to 35 cts. per year, which means a saving in light of $1.45 to $1.55 perlamp per year by keeping the lamp clean. Consider the case of a 250 watt Mazda lamp in an industrial plant where the units are used 4000 hrs. per year and energy costs 2 cts. per kw-hr. The total cost of operation is approximately $26 and a 15% saving amounts to $4.00. The units can be cleaned once a month for about 40 cts. per year, which is a saving in light of $3.60 per lamp per year. These figures apply to average installations but in many instances the saving would be greater. There are any number of schemes for cleaning lamps and reflectors. In offices, stores and places of such character, where glass reflectors are used, it will be found necessary to take the reflectors down for a thorough cleaning only once every three or four months, and when the lamps are re- newed. A wet cloth used with a bristle brush is sufficient for a good cleaning until reflectors are taken down for washing. In cleaning lamps dry woolen or silk cloths should never be used, as the static electricity developed may cause the fila- ment to break. Always use a cotton cloth or cotton waste. In textile mills and places where only a coating of dust settles on the lamps and reflectors a dry cloth is all that is necessary to put the lamps in good condition. In mills and shops where steel and enamel reflectors are used and where more or less grease accumulates on the reflector, a bunch of cotton waste and some gasolene is necessary to remove the dirt. In all case^, it is seldom necessary to remove the re- flectors in order to clean them. In cleaning Mazda lamps it is always best to have the lamp burning. Although the present drawn wire Mazda lamp is very much stronger than its predecessor, the pressed filament lamp, this minor precaution of switching on the cur- rent for one or two minutes will often prevent broken lamps. Drawn Wire Mazda Lamps The drawn wire filament of the present Mazda lamp is many times stronger than the old pressed filament at any time during its life. This fila- ment is continuous and of uniform size, so that uneven heating of any part of the filament is 64 impossible. This quality has much to do. with the uniform life of this lamp. The essential qualities of an incandescent fila- ment are: 1. High Melting point 2. Low vapor tension 3. Proper radiating characteristics 4. High resistance. The higher the temperature at which a given incandescent filament operates the greater the quantity of light radiated in proportion to the energy used. The increase of light emitted is very marked at high temperatures, so that a slight increase of temperature of an incan- descent filament means a large increase in the amount of light given off. The melting point of Tungsten is higher than those of other materials now used for filaments. Low vapor tension is very important, as it is necessary that the filament does not evaporate rapidly at high temperatures. The drawn wire filament is especially ideal in this particular as tungsten has a low vapor tension. The drawn wire tungsten filament is a poor radiator of heat, so that at the same temperature it will emit more light than a carbon filament, The superior light giving quality of the Mazda filament is due in part to the fact that a rela- tively large per cent, of the energy radiated falls within the limits of the visible spectrum, High specific resistance is a desirable feature of an incandescent filament in that it allows the use of a thick and short filament. The positive temperature coefficient of the Mazda filament is another valuable feature, as it insures a more nearly uniform candle-power on fluctuating volt- age. The effect of this positive temperature coefficient is shown in the curves on page 71. Types of Mazda Lamps Mazda lamps of the regular type are made in sizes of 10, 15, 20, 25, 40, 60, 100, 150 and 250 watts, for voltage ranges of 100 to 130, and 200 to 260, excepting the 15 and 20 watt lamps, which are made for 100 to 130 volts only. These are fur- nished in straight side bulbs designated by the letter "S," and the extreme diameter in eighths of an inch, as for example: the S-17 bulb has a diameter of 2-1/8 inches. The round bulb types are made in sizes of 15, 25, 40, 60, 100, 150, 400 and 500 watts for the 100 tc 130 volt range, and in sizes of 25, 40, 60, 100 and 500 watts for the 200 to 260 volt range^ The round bulbs are designated by the letter "G." A tubular lamp is made in the 25 watt size for the 100 to 130 volt range. This bulb is designated by the letter "T." A concentrated filament lamp is made in the 100 watt size, round bulb, for the same voltage range. 65 The schedule of Mazda Sign lamps is shown complete on page 42. Large style lamps for 20 volts, and below, are made as follows: 2.5, 5, 7.5 and 10 watts in the S-14 bulb, 10, 12.5 and 15 watts in the S-17 bulb. 15, 20, 25 and 30 watts in the S-19 bulb. 2.5, 5, 7.5, 10, 12.5, 15, 20, 25 and 30 watts in the G-16K bulb. Mazda St. Series lamps are made for the fol- lowing ampere ranges, and in the following candle-power sizes: 3. to 3.8 amperes in 32, 40, 60 and 80 C.P. sizes; 3.8 to 4.3 amperes in 32, 40, 60, 80, 100, 200 and 350 C.P. sizes; 5.1 to 5.9 am- peres in 32, 40, 60, 80, 100, 200 and 350 C.P. sizes : 6.1 to 6.9 amperes in 32, 40, 60, 80, 100, 200 and 350 C.P. sizes; 7. to 8. amperes in 32, 40, 60, 80 and 350 C.P. sizes. Train lighting lamps. The Gem berth lights are made in sizes of 15 and 20 watts in the G-12 bulb. The Mazda Train Lighting and Compen- sator lamps are made as follows: 25 to 34 volts and 50 to 65 volts in sizes, 10, 15, 20, 25 and 50 watts in the round bulbs, and in sizes, 10, 15, 20, 25, 40 and 50 watts in the "S" bulbs. Mazda Street Railway Lamps are made in 23 and 36 watt sizes. 100 to 130 volts, to operate five in series on circuits of 500 to 650 volts, and are especially selected for amperes. In addition to the standard Mazda Railway Lamps, Mazda Gauge Lamps of 10 volts are supplied for use in series with the standard lamps. Automobile and Electric Vehicle lamps are given on page 36. Gem Lamps The Edison Gem or metallized filament lamp, although not as efficient as the Edison Mazda lamp, has a decided advantage over the Carbon lamp as a low initial cost unit. A great many Central Stations give free re- newals on Gem lamps, and are substituting them \vatt for watt for Carbons. The substitution watt for watt does not reduce the Central station load, but gives the customer a 20% increase in illumination for the same cost. The Gem lamp gives a whiter and more agreeable light and due to the positive temperature coefficient, is steadier on varying voltages. In private plants running at full capacity, the adoption of Gem lamps will give an increase of illumination of 20%, or if additional space is to be illuminated, 20% of the generator capacity may be secured for this purpose by their substi- tution. In designing a new private plant the 1 i o N * J ON o : x : _ CO * ^ 1 _i J on" : CM r^ CO i ON '-' 1-1 8 8 O 1 X ^ C>J s s 10 f> O "^T io X ON 2 | 1 ^ O 5: 2 CM ON s X 10 rH T 8 X <-> O ^- _ X O X X s 1 e o 3 f. J o CM CN] ^ 1 ?. o ~> CO VO rH ' > 10 ^> 10 ON *" 00 r ~ { ^ tn ON 5? !<5 ^ CM 'JU ^J 2 X CO - i ! ^ . PC 8 25 ? o CM T o s; 10 ON ^ ^ ^ J-. ^ i I, J o O '"' s X S O % j q o ^ ^ 2 00 ^ vd ,,_, r-( I X ^ rn' T * * rH o < S3 X o oc X c^ a T) tn a rn E (D p (11 a ps now in use rt J CO O "o to be substitut rt 1 "o Wattage n candle-powe ps now in use . of Carbon La jjj 1 1 o f. of Gem Lam Wattage T candle-powe E ,2-.a5 isliiel ilSl-J 3 !5H iikfli - a) ^i?^::::::^^ -~-ht- Percent 3 :" !^ ? Candle 6 ^^^-- Power 110 ^ LtfTI 1 1 1 1 i+H ^ PwKN ^$^ t=* 8 7Q ^HJtfMtr so ::::^s?j:::::: 50 : 5;S^ 2 / : ::::::: sf|-2?:: :::::::: 30!=:::: + :::::::: 20 -- ---vi^ d --J5g so g []]^ffl^70 ^ ::::::::::;; so 10 -- J ;; :; JEB 1 1 M | 1 1 1 II 1 r >0 U5 101) 105 110 1-13 120 Percent Volts Fig. 24 71 little from the average results obtained by test. The contrast in performance as shown by the curves is apparent at a glance. The decline of candle-power and the increase in specific con- sumption are least for the Mazda lamps. Thro- ughout its life this lamp has very nearly a uni- form performance, the slope of its curves being much less than that of any other lamp. Characteristics of Lamp Filaments In Fig. 25 are given curves showing the per- centage change in volts, amperes, watts, and watts per candle, accompanying the changes in candle-power of Mazda lamps. Fig. 26 shows the variation in resistance, due to temperature changes, of the Tungsten, Tantalum, Carbon, and Gem filaments in percentages of their re- Percent Wat 00 000 2 300 , --,- 0005 2vjQ|j [I 1 1 |l|| 1 || 1 || HI || 280 tH 270 ts per Candle ^SSSS^SiSSS 25o| ! 1 1 1 1 1 ! HI tlrn nttt 24QU4. 1 IjjJI Mil 23QJ- ff$--- :::: 220 ;r Tm--- 1 " 1 ^ 210 LU--lg_---- 200::: :::Js:^:::: *l90 + :-=:=::gtt::::^ l70::::+::i.y::::::: ^ ;i % laO-- + XTJ i~ g 130H-I4-I [I 1 1 |\| I) // ^l2Q--^-^ gllo::::::::::: = ::ffl^: Sioo-- !--- iljiiiilljij ii|ii:; |r5&::::::z::::::: :::::::::::::::!:: * *0:::f::2?S T ::: : 2?: : 3S::: "fTTtTTItlTttlllllliJ- iliiii -Percent Volts, Amperes and Watts Fig. 25 72 spective cold resistances. As can be seen the Carbon lamp has a negative temperature coeffi- cient so that an increased voltage means a de- crease in resistance, thereby increasing the variation to a further extent. The Tungsten filament, however, has a positive temperature coefficient, and as an increase of voltage means a marked increase of resistance the Change of current is small in proportion to the rise of volt- age. Due to this positive temperature coeffi- cient the Mazda lamp undergoes smaller changes in candle power, efficiency and life than does the carbon filament. The variations of candle-power and efficiency with variations of voltage are shown by the curves in Fig. 24. As explained above these curves show that the Tungsten filament under- goes but small change as compared to the other types of filaments. 1400 10 30 50 70 90 110 i 130 20 40 60 80 100 120 140 For cent oZ Volts Fig. 26 73 Cost of Light The average total cost per unit of light pro duced by incandescent lamps may be considered as made up of two elemental parts, cost of energy and the cost of renewals. It is evident, then, that the most economical efficiency at which a lamp can be operated is that at which the sum of these expenditures is lowest. As the cost of energy becomes higher, or as the cost of re- newals becomes lower, the efficiency should be increased. This is shown by the curves in Figure 28. These curves show the economical efficiencies at which a 250 watt Mazda lamp should operate for various charges per kilowatt hour of energy. The average total cost in dollars of 1000 candle hours of light is equal to Cost per kw-hr. in dollars X initial efficiency factor , cost of lamp in dollars X 1000 hours life X initial candle-power X factor. The factor referred to in the above formula is the -ratio of the average to the initial candle- power and life. These values are : Mazda .95 Gem .85 Carbon .80 The total cost of a number of hours service is composed of the cost of energy and the cost of renewals for that number of hours as shown in the formula on page 5. Table 21 shows the total cost of lighting for 1000 hours service, with the various sizes of Mazda lamps, Owing to the greater efficiency of operation there is a great saving effected by the substitution of Mazda lamps for either Carbon or Gem lamps. This saving has been calculated for several substitu- tions, and the results are given in Table 20. As can be seen in this table the Mazda installation will in each case give equal or higher candle- power than the replaced Carbon or Gem lamps. The tables referred to above show the Mazda lamp to be the most economical lamp. It should be remembered, however, that in general this lamp should be operated at high operating effi- ciency. Quite often in installing a lighting sys- tem a lamp is specified as operating at high efficiency for a voltage two volts higher than the actual voltage at the lamps. For example, a lamp specified as operating at high efficiency at 118 volts will operate at medium efficiency if the actual voltage at the lamps proves, by test, to be 116 volts. This means that the economy of the installation is decreased, and it is essential that the user of incandescent lamps makes sure that his lamps are operating at the proper effi- ciency. Too often a lamp that has outlived its 74 rated life is allowed to remain in the circuit- This not only mars the appearance of the instal- lation but also cuts down the efficiency. The wattage consumption remains practically the same, so that the user of a lamp that has passed its rated life by several hours, is paying for energy that does not produce the amount of light that could be gained by renewal. 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Rate per K\v.-hr. in Cents Fig. 27 Curves showing total cost of 1000 candle-hours of light produced by various types of lamps. 75 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 tN3 rf^ 00 H- 1 Bate in Cents per K\v.-hr. / cf /' , - ~ '/& /^/ a /^/ \ ^/ ^ // J / ^ x ^ G "V V| x / / b^ i ^ C / ?# \ ? ^ 1 i ^ se '\ ^ ^ ,-- ^ v f ^ s ~~~ ^ "^ \ .if "* ^ \ 3 8 ^, x, H sss ^ ^ \ o. f,al _c 3= ^ t Q \ =1 \y ita . JJ - - 2 ^ r> ^ ^ 7 Q ^ I 3 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Watts per Candle Fisr. 28 |,J a "o "H 1 | | ft 3 3 iji|l ^ S d "3 row A\ OZl-II I I | 1 | 1 | S Iflii 7| ^ 6-Sai ?ac .l d '3 S'Z "Ai 08-01 | IS 1 S 5 ^lasin HIM ^ S "M. 001-01 | || | 2 | | = Ull! > 3 ui?o H 1 IK S s v OOOOOgOO|g 3-w S| i|^^ d '3 'OZ - A\ OS-IT '-sssasaas! ogtE-^ fsSo d "3 Z 'Oc 'A\ 09-01 IM 2 a 1 3 ]||||| . t ? aalo a^o H 1 g i = 1 * !2l2SSft5S Isllil 8-3 "AY OOT-r S 2 J -.^w^^^O^-.;^ 2 d^' * S '& d "3 vot 'M OZl-f 1 fH I 1 * S - - o in iSSo 1^11! > * a OH S 83 3 W 8 . tffi2g|5ggS|5 " - 2 3 S 6? 1 ^ 3 'O'H 2 5 o 1 g ~ ^ i|l! 5 ^.l a 'o H 'd^siz 1 IS ft c^ SI2ilssl ^SS'S-c stPf! S'Sjy 'M09-Z S -~M* SlsslS- ai a'O'H uoqjBO d "3 8-91 2 l 1 | g g pips.^si "TJ8 . fc ' a u2 H 8S 8 ^..^l-^-J^ S^|J 5 'H^ 'AV08 " ? S 8 S cid--rii-r gl|lS "s a 'o 'w uoqjBO 'd "3 S 01 'MOOT - i i 1 i i 2 ^^282^1 |lp|| a -o -w d'30Z 'AV OS S iS ! ? 2 3 3 l^g^PiS ^I'lii | s ? d '3 8 91 AVOS I^ S 8 ^ * o ? s a g-sfg^l IRfli e -'M^S^S Mazda Lamps to replace S I TJ fe K . SlU-!lS il^isllsl^^is 35 aJ'jrra"!* I 1 III 77 I I, *I a: |li c^g' * S o , _ 5 11 o 5J-2 H 85 >M j. * SlS'S 5 o s ;i||{ I ell 1 ^i!fi! i |i! | ol 5-S^82 1 1!!! SI K ! S S!1 Illfl in!!! Ss?;s! III! 78 S c .1*1 a 1 6! = * 2> 1^ - bfill 3 f* ^!|- s<2 8S 3 i c X : * 3 5 8 *S 3 CU ' |S i s - "! j a 31 ^sa -I Kill . 0-0075 .0100 ; Powe r * 1 ^ tt-Hou IPlP w 29_3 o i! 79 Energy Losses in Incandescent Lamp Filaments. Transmission of electrical to thermal power in incandescent lamps is, so far as known, perfect and without loss. The heat produced in the fila- ment must, in the steady state, escape at the same rate at which it is generated. The escape, or heat dissipation, from the filament must occur by radiation, conduction, or convection. Radi- ation is believed to be an electro-magnetic process whereby electro-magnetic waves are set up in the space surrounding the filament, and are transmitted outwardly in all directions at the velocity of light. All the light usefully delivered by the lamp is due to this radiation, and depends upon how much radiation is pro- duced within the limits of the visible spectrum. The major part of the radiation given off by the filament is non-luminous, that is, it has a fre- quency either too low or 100 high to be perceived by the eye. Moreover, some of the radiation in passing through the glass walls of the lamp is absorbed and heats the glass, so that this lost radiation is given off finally by air convection from the bulb. A percentage of the heat escapes from the filament by conduction through the leads and through the supporting anchors. A part of the heat escapes from the filament into the surounding gas by convection. This is neces- sarily only a small part, however, and depends upon the condition of the vacuum. The ratio of total energy radiated to the power consumed is spoken of as the relative radiation capacity. > The ratio of luminous radiation to the total radiation is called the light effect and the ratio of luminous power to the total power con- sumed is the useful effect or net efficiency. The determination of these relations is difficult and various schemes have been used for their meas- urement. The values given in the table are conclusions arrived at by different experiments, and an average of the values for each relation may be considered as a fair approximation. In the pressed filament type of lamp it was necessary that the filpment have good electrical contact with the bottom anchors, and a good electrical contact is a good thermal contact. In the drawn wire type the only electrical contacts are at the lead wires, consequently the heat loss due to conduction is less. This means an in- creased ratio of total radiated energy to total power consumed. A comparatively large per- centage 'of the radiation from the drawn wire filament is within the visible spectrum, so that this lamp has a high ratio of luminous radiation to total radiation. As both of these ratios are high, the lamp has a high net efficiency. g e id cj >> S'S ll'| H fi J3 j -s|S h-3td 0) s^ 03 (S U ^ < Carbon 61.9 2.85 1.75 3.8 a 1.56 3.1 115 Volt 2.2 2.85 c 3.1 2.64 250 Volt 12.42-3.42 3.1 b Tantalum 64.8 4.26 6.35-6.66 2.75 2.02 1.97 a b Osram ' 75.6 4.63 3.5 151 a Tungsten 250 Volt 7.6-9.39 1.31 b 130 Volt 6.43-6.61 I 1.28 b 4.5 1.31 115 Volt 5.2 1.18 c 6.00 1.05 References : Electrical World, March 9, 1911, Page 593. a- Elek. Zeit., March 16, 1911, G. Leimbach, E. World, April 27, 1911. b- Electrical World, May 18, 1911 , R. A. Houston, c- Elek. Zeit., Oct. 12, 1911, J. Russner, Electrical World, April 20, 1911, Page 982. Prevention of Static Effects Incandescent lamp filaments are sometimes affected by static electricity from moving belts, silk, etc. As a means of preventing any trouble from this source a metallic comb consisting of a row of sharp projecting teeth is placed on the top and under side of the belt, and securely grounded. Though this method is fairly effect- ing with the operatives. Another device, which has found considerable favor in many mills, consists of a small motor generator set with transformer. The current is transmitted to two inductor bars, extending across the width of the machine, and about three inches above the moving bands of paper, silk or wool threads. These inductor bars have several fine wire points which carry the electric charge. Since these points are charged by alternating current, they carry both positive and negative charges. Consequently it makes no difference which of the two kinds the hostile charge may be, as it will be neutralized by an opposite charge from the wire points. 81 The cheapest and perhaps simplest way to overcome the harmful effects on incandescent lamps is to form a protection for each individual lamp unit. This is easily accomplished by means of a wire guard around the lamp. As the pur- pose of the guard is to neutralize the static flux before it can collect on the lamp, it is evident that the smaller the meshes the more effective it will be, though, of course, they must not be so small as to noticeably reduce the amount of light from the lamp. Where several lamps are combined in one cluster the same result can be obtained by using one bowl shaped wire guard underneath. The wire guard can be grounded by means of a wire extending up along the fixture to some iron work in the building, or to a nearby gas or water pipe that will make a good ground. This wire, when intertwined in the lamp cord, should be heavily insulated, in order to avoid any possi- ble short circuit. A three wire lamp cord would be very satisfactory for this arrangement, the third wire being used on the lamp guard. By using a wire guard which fastens to the bulb of the lamp there will be no metal connections be- tween the socket and the grounded guard, thereby making this entire arrangement strictly in accordance with the underwriters 1 rules. Fixtures The selection of fixtures in an installation de- pends on the surroundings and no set rules can be given to govern the selection. When we consider that in a successful installation of an artistic or decorative nature the fixtures and illuminants must blend so well with the general scheme that attention is not attracted to them, and a person having left the room is unable to describe the lighting fixtures, we can readily see that the designer must have had a considerable sense of harmony. The manufacturers of elec- trical equipment have, in the last ten years, made rapid strides in the development of a great variety of designs. There is a wide range from the plain designs of cheap tubing to the more expensive ornamental designs, but there is a wider range within the latter class itself. The use of fixtures, however, is often a source of danger, unless the proper, precautions are ob- served. The National Board of Fire Underwriters has laid down strict rules regarding the use of fixtures which are given in the National Electric Code on Page 110. 82 Visual Acuity Visual acuity is, in its broad sense, as the name implies, acuteness of vision. It may, however, be better understood by a study of the means used to measure this acuteness of vision. Fechner performed a series of experiments, in which he varied the intensity of a shadow on an illu- minated background, and determined the mini- mum difference in illumination distinguishable. He expressed this difference in illumination in the form of a ratio, and this latter became known as Fechner \s constant, and is a basis of visual acuity measurements. This constant is 1/101 and it means that when \ve have a 1% difference of intensity we can just distinguish this difference in intensity, provided the two surfaces illuminated are in juxtaposition, and can be seen simul- taneously. The constant does not hold good for very low or very high intensities. Any object focused in the retina of the eye sub- tends a certain angle at the eye, and from this angle and the focal length of the eye may be de- termined the size of the image on the retina. Helmholz conducted a series of experiments to determine the smallest visual angle and the size of the focused image. Later this work was sup- plemented by Snellen, and the results of his investigations embodied in the reading chart bearing his name. Snellen determined that the smallest visual angle for the average eye was one minute, and on this basis he built letters giving the distance at which the normal eye should just perceive them. For instance, we find E for the above letter "E" the normal reading dis- tance is 20 ft. In this letter we have vertically two spaces and three lines ; each space and line must subtend an angle of one minute at 20 feet or the entire letter subtend an angle of five minutes. Now, if a person can just distinguish this letter at 21 feet we say he has a visual acuity of 21/20, or 1.05, and we have another means of measuring acuteness of vision. This is by far the most popular conception of the term, and this chart is often used by opticians in testing eyes. Visual acuity is affected by the intensity of the light, the color of the light, and the condition of the eye (Contraction of the pupil); also it is affected by the health, loss of sleep, mental and physical fatigue and fatigue of the eye itself. However, the effect of fatigue is much less than 83 is popularly supposed. The effect of variation on intensity may be shown by the following curve in which acuity is plotted as ordinates and intensity of illumina- tion as abscissae. ir? f\ ^ i b c d Int2nsity e / Fig. 29 a Total darkness. b Threshold point where vision begins, about .00002 (by Aubert) . c About 2% foot candles. f Where vision ceases at extremely high in- tensities probably above 4000 foot candles. The point that should be noted is the very small variation in acuity from c to e, and it is be- tween these points that Fechner's constant holds good, slight variations being due to the fact that there is a slight increase of the acuity up to d and a gradual falling off from there to e. The effect of the color of the light on acuity has also been thoroughly established, but exact values are hard to obtain The fact that mono- chromatic colored lights present many difficulties in photometry, and are hard to obtain, probably accounts for the scarcity of reliable data. It is undoubtedly a fact, however, that with high candle-powers the part of the spectrum which gives maximum acuity is about the orange- yellow, while with low intensities this point shifts to the yellow-green part of the spectrum. This shifting of the maximum acuity point was first noticed by Purkinje, and was thereafter known as the Purkinje effect. The luminosity curve for the different parts of the spectrum has been in- vestigated to quite an extent, and it is probable that the acuity follows this curve in a general way. Several experiments in acuity with the use of different illuminants used under different con- ditions have been performed by Mr. Ashe, at Harrison, and this data has been published from time to time in the various engineering periodi- cals, and the Transactions of the Illuminating Engineering Society. In considering any illuminant or form of illu- mination the visual acuity values obtained with a certain foot candle intensity are by no means the final criterion by which to judge any illumin- ant or installation. The aesthetic side which em- braces color adaptability and general appearance 84 must also be considered. Then too, we have a more technical side which embraces distribution, watts per effective lumens, etc., but the fact still remains that visual acuity is an important factor both in installation and research work. Intrinsic Brilliancy of Light Sources. Louis BELL, Ph. D. Candle-power per sq. in. Moore tube 0.3-1.75 Frosted incandescent 2-5 Candle 3-4 Gas Flame 3-8 Oil lamp - 3-8 Cooper-Hewitt lamp 17 Welsbach gas mantle 20-50 Acetylene 75-100 Enclosed A. C. arc 75-200 Enclosed D. C. arc 100-500 INCANDESCENT LAMPS Carbon 3.5 watts per candle 375 Carbon 3.1 watts percandle 480 Gem 2.5 watts per candle .- 625 Tantalum 2.0 watts per candle 750 "Mazda" 1.25 watts per candle 875 "Mazda'' 1.15 watts per candle 1000 Nernst 1.5 watts per candle. 2200 Sun on horizon 2000 Flaming arc 5000 Open arc lamp 10.000-50,000 Open arc crater 200.000 Sun 30 above horizon 500,000 Sun at zenith 600,000 Luminescence Light in any form is produced either through temperature radiation or through luminescence, or a combination of the two. When light is produced by simply heating such ordinary material as carbon or a metal to a high temperature, the light is said to be produced by temperature radiation. Examples of this are the radiation of light from (a) heated carbon particles in an ordinary flame as of a candle, kerosene lamp, or gas flame, (b) the crater light of an open or enclosed carbon arc, or (c) the light of an incandescent lamp filament. The term luminescence is applied to radiation through more complex action, involving a change in the material. There are a number of allied phenomena included in this class which are more or less indefinitely classified and de- fined. 85 Phosphorescence and Fluorescence are per- haps the most familiar forms of luminescence. Phosphorescence is the phenomenon peculiar to certain substances such as calcium sulphide which gives off a glow after having been ex- posed to light. This is also known as photo- luminescence. Phosphorescence is also applied to describe light which accompanies the slow oxidization of phosphorus, although, this is more scientifically designated as chemi-lumines- cence. The light of the fire-fly is an example of chemi-luminescence. Fluorescence refers to the property of sul- phate of quinine and certain other materials by which they glow when exposed to light, the light emitted being of a lower rate of vibration than the impinging light. A common example of this is the transformation of invisible ultra-violet radiation into visible light by willamite. The color of phosphorescent and fluorescent light does not. usually correspond to the usual superficial color of the material. Moreover, in the case of materials subject to both phenomena, the fluorescent color often differs from the phos- phorescent. Luminescence may be induced by heat or electric energy. The light from a flaming arc lamp is usually ascribed to luminescence induced by heat generated from the electric current. In the case of gas mantles, investigators do not agree as to whether or not luminescence is in- volved in the light production. Electro-luminescence occurs in the mercury vapor arcs and vacuum tube light sources. Al- though heat is present, there is reason to be- lieve that the action takes place without its forming an intermediate step. Luminescence is of especial interest in connec- tion with the development of new illuminants, since with our present knowledge it seems to offer the greatest possibilities in the way of in- creased efficiency. Investigations of the light of the fire-fly indicate an almost perfect effi- ciency, although, its color in high intensities would be rather disagreeable. present, til Liiic'itu iiiumriiciuu-i, even it IL wcic carried so far as to make a sacrifice in color. Instructions for Ordering Lamps To avoid misinterpretation of orders it is ad- visable that customers mention the following facts on each order: 1. QUANTITY (number of lamps desired). 2. CLASS (Gem, or Mazda). 3. SIZE OF LAMPS (in watts, whether 40 watt, 100 watt, etc. If Street Series lamps are ordered give amperes and candle-power. If Mazda minia- ture lamps are ordered give candle=power). 4. CIRCUIT VOLTAGE (voltage at the lamp socket) . 5. OPERATING EFFICIENCY (whether High, Medium or Low) . 6. STYLE OF BASE (whether Medium Screw, Mogul Screw, Bayonet Candelabra, etc., and also the style number of the base. When lamps are scheduled as being manufactured with skirted and unskirted bases, as for example, the regular 40 watt Mazda, the order should distinct- ly specify whether skirted or unskirted base is desired). 7. TYPE OF BULB (whether Straight, Round or Tubular) 8. WHETHER LAMPS ARE DESIRED CLEAR, BOWL FROSTED OR ALL FROSTED. If colored lamps are desired, state color and whether lamps should be superficially colored or made of nat- ural colored glass. When lamps are furnished with the single voltage label, item No. 5 should be omitted. Order Standard Packages. When ordering lamps, customer should bear in mind that the manufacturer stores the lamps packed in standard packages. An order for quantities less than standard package incurs delay and needless expense on account of the repacking which necessarily has to be done in order to supply a broken package. It is also to the customer's advantage to ad= here to standard lamps listed in the schedules. The large variety of lamps and voltage ranges which are listed should permit the selection of lamps that will give satisfactory results under any conditions. Whenever it becomes necessary to order spec- ial lamps, the manufacturer reserves the right to fill all such orders either short or in excess of the exact quantity ordered within the limits of 10 per cent. This is necessary on account of the fact that it is impossible to always produce an exact quantity of any special lamp. If the above directions are carefully followed when orders are placed, needless errors and de- lays will be avoided. 87 Predominating Color of Light from Various Sources. Illuminant Color Average Daylight White High sun Yellowish White Low sun Yellow to orange red Sky light Bluish white Arc-D.C. open White slight yellow tint Arc-D.C. enclosed, 80V. Arc-D.C. intensified Arc-D.C. enclosed, 150V. Purplish or violet tint Arc-A.C. enclosed, 75V. Slight purple tint Arc-Magnetite Approximately white Arc-Flame (yellow carbons) Orange yellow Arc-Flame (white carbons) Approximately white Arc-Flame (red carbons) Orange red Nernst Lamp Yellowish tint Tungsten- (1.25 wpc.) Nearly white, slight yellow tint Incandescent (carbon) Yellow tint Acetylene flame Yellow tinted Mercury arc Blue green Gas Mantle Greenish white or amber Gas, ordinary burner Pale orange yellow Kerosene Orange yellow Cs.,idle Orange Moore Tube (COa) Approximately white Moore Tube (NTs) Salmon pink 88 Electric Circuits With Special Reference to Incandescent Lamps There are two distinct systems for distributing electrical energy; namely, series and parallel sys- tems. The former is known as the constant current system and the latter as the constant potential. A combination of the above systems is used for sign lighting and is known as the parallel group in series, or simply the parallel series method of distribution. Series System In the series system, the same current flows through all the lamps and is usually maintained at a fixed value by a regulator or a constant current transformer, as used in alternating cur- rent circuits. In this system, the voltage of the generator or transformer directly supplying en- ergy to the system is divided according to the resistance of the lamps. If all the lamps have the same rating and there are ten lamps in a series circuit of 100 volts, then there is a voltage of 100 volts divided by 10 lamps or 10 volts across the terminals of each lamp. For series systems all lamps should have ap- proximately the same current rating. Lamps are cut out of a series system, not by turning off the lamp, that is, by opening the socket, but by short-circuiting the lamp to be cut out of the system. In an incandescent series system each lamp socket is equipped with an automatic cut-out which short circuits the filament of the lamp in case of failure or burnout. A thin insulating film, w r hich will puncture under a potential of 75 to 100 volts, but which withstands lower volt- ages is placed between two contact points. When a lamp circuit is broken the full feeder voltage is impressed upon the contact points, breaking down the insulating film, thereby re- storing the circuit by bridging the filament. With alternating current the constant current transformer supplying the current is usually de- signed so as to maintain the current constant under all conditions independent of the number of lamps in the circuit. Parallel System In this system the voltage is approximately constant and the current is divided between the lamps according to their resistance. This is called the parallel system because the lamps 89 are used in parallel or multiple. This system is used almost exclusively for interior lighting. The 100-130 volt lamps operate at a better effi- ciency than 200-260 volt lamps, so that on a 200- volt circuit 2-100 volt lamps are used in series in- stead of 1-200 volt lamp. This scheme, however, has two disadvantages; first, if one lamp fails the circuit is open and both lamps are out of service; second, the lamps used in series must have approximately the same current and volt- age ratings, as it is impossible to satisfactorily operate lamps of different wattages in series. The advantage, however, of the 200-volt system is that for the same energy transmitted the cur- rent is halved so that the amount of copper necessary for the installation is quartered, there- by securing great economy in construction. To make use of this advantage and to do away with the disadvantage of two lamps in series the Edison Three-Wire System was designed. By this scheme two generators in series supply power to the outside wires. The lamps are con- nected between these outside wires and the middle or neutral wire, which is connected be- tween the two generators. Now the burning out of a lamp on one side does not materially effect the lamps on the other side since the cur- rent returns to the neutral wire and maintains a circuit. When this system is properly balanced, the neutral wire carries very little current, and therefore can be smaller in diameter, thus secur- ing greater economy. Three=Wire System with Balancer This system has a decided advantage over a three-wire system supplying energy by two gen- erators in series, inasmuch as 1-200 volt gen- erator can be employed. Between the outside mains is connected two dynamos of 100 volts each, the two machines being in series, the neu- tral wire being connected between these ma- chines. In case more lamps are operating on one side of the system than the other the voltage on the side which has the most lamps in operation tends to fall off, but is automatically maintained by the current flowing along the neutral wire to one machine running as a generator , and there- by boosting the voltage of the loaded side enough to make up for the voltage drop caused by the unbalanced conditions. The reverse will be true if the system becomes unbalanced by more lamps being operated on the other side. By care- fully balancing the two sides of this system the load will not vary more than 8 or 10%, so that the capacity of the motor generator set will only be about 8 or 10% of the capacity of the main generator supplying the energy of the circuit. 90 Voltage Regulation In maintaining the voltage at the lamp to a fairly constant value it is necessary that the group of lamps employed be as near the point of distribution as possible and that the diameter of the wire be large enough to carry the current without a very large drop in voltage. A formula is given on page 99 for calculating the drop in voltage between the lamps and the point of dis- tribution. The factors which determine the sizes of wire are: First; the wire must be large enough to carry the desired current without overheating and injuring the insulation. Second; the wire must be large enough to keep the voltage at the lamps within certain limits. A total drop of 5% is permissible; 2% in the mains and 3% in the distributing wires. In a system where power is fed at the end of the system the lamps are arranged in parallel. In this system the voltage drop is great, inas- much as the load center is far from the point of distribution, and the current has to traverse a large amount of copper. It is also necessary to have a wire of large diameter to prevent ex- cessive drop. A method for maintaining a constant voltage at the lamps but which requires more copper is the return loop system. In this system each lamp receives approximately the same voltage, inasmuch as the current to each lamp has to traverse the same amount of copper conductor. This is a great advantage in all extensive in- teriors, for when lamps are installed they can be selected for the same voltage and there is no fear that a lamp on the top floor of a very tall building would receive a lower voltage than on the lower floor. A system of this type installed in one of the prominent tall buildings of New York City on voltage survey showed a drop of less than 2% on a 200-volt system and the volt- age was fairly constant over the entire building. The Conversion of Two=Wire High Voltage Systems to Three=Wire y^ Low Voltage Systems. Due to the better performance and greater economy gained by the use of 100-130 volt lamps in preference to the 200-260 volt types it is often desirable to change a high voltage system. In such a case it is oiten inconvenient and not at all practical to alter the wiring: of the whole building. Recently such a change was desired in a large building in New York City. The prob- lem here was simplified to a great extent by the plan of wiring then in use. This plan is shown in Fig. 30 and consisted of a three-wire system with Fig. 30 the two outside wires connected to the negative bus-bar and the return loop connected to the positive, so that in reality it was a double two- wire system, having a potential of 240 volts be- tween the positive and each of the two negative wires. This plant was changed over without altering the wiring of the building, by changing the switchboard connections in the following manner: A balancer set was installed and what was formerly the positive wire was connected to the neuti al of this set. One of the outside wires was connected to the negative bus-bar and the other to the positive. The new connections are shown in Fig. 31. By this method 120 volt lamps can be used instead of the 240 volt types. As the load is nearly balanced, a balancer set of small capacity is used to take care of any fluctuations in either side of the line. Distribution Systems Direct Current Two Wire Fig. 32 Return Loop Fig. 33 Three=Wire, Two Generators Fig. 34 Balancer Set Pig:. 35 93 Storage Battery Balancer Fig. 36 Double Dynamo Two armature windings on the same core at- tached to two separate com- mutators. Fig. 37 Three Brush Dynamo This machine has two adjacent north poles and two adjacent south poles, making practically a bi-polar Fig. 38 machine with divided poles. The neutral brush is taken off between like poles where there is very little e. m. f. gen- erated, reducing sparking to a minimum. Dobrowolsky System Fig. 39 The neutral wire is connected to the middle point of an induction coil which in turn is connected to two diametrically opposite points of the winding of the armature. The e. m. f. 94 impressed on the terminals is alternating and the inductance set up in the two halves of the coil are equal, keeping the potential of the neutral wire midway between that of the out- side wires. Three=Wire System With Compound Wound Boosters Fig. 40 The main generator is sufficiently over-com- pounded to take care of the total drop in the conductors. The boosters are also compound wound and mechanically coupled. An increase of current through the series field coil of either machine produces a higher voltage on the loaded side, so that the balance is maintained. The three-wire system can be extended to a five or seven-wire system, using compensator sets or storage batteries for the balancers. The table given below shows the comparative weights of copper required for the different sys- tems to deliver the same wattage with the same drop in potential at the receiving end. Ordinary two-wire system 1.000 Three-wire system ; all three wires of same size .375 Three-wire system; neutral one-half size .313 Four-wire system; all wires same size .222 Five-wire system; all wires same size 156 Five-wire system; three inside wires one- half size .109 Seven-wire system; all seven wires of same size 097 Table 22 shows the carrying capacity of copper wire for direct current circuits. Alternating Current Systems. In Table 23 is shown the amount of copper re- quired by the various systems as compared with that required for the single phase two-wire system. The amount required for the single phase two-wire system is taken as 100%. In the single phase three-wire system consider the po- tential between the two outside wires as 2 e t where e represents the voltage of the two-wire system. Applying the rule that the amount of copper varies inversely as the square of the volt- age, only one quarter the copper will be needed, 1 M OOOOC u 1 5 !z; ^j S232S8SS888888 98 _DXWXK Area of conductor in circular mils p x F 2 W X T Current in main conductors = - Volts loss in lines ~ E P X E X M 100 1)2 x WXK X A Pounds copper required = pxE 2x l 000000 W total watts delivered. D = distance of transmission in feet (one way) . P Line loss in per cent of power delivered, that is. of W. E = Voltage between main conductors at receiv- ing end of circuit. The values of constants K, T, M and A for alter- nating current are given in Table 25. For continuous current : K = 2160, T = 1, M = 1 A = 6.04 Wiring The following formulae will be found sufficient for calculating the size of wire required to carry a given load with a specified allowable voltage drop. The resistance of ordinary copper wire is equal to the length in feet divided by the area in cir- cular mils multiplied by the resistance per mil foot, which under working conditions is 10.8 ohms. that is, R = ~ X 10.8 ohms (1) A R = Resistance in ohms / = Total length in ft. A = Area in circular mils From Ohm's Law, the loss in volts (e) in a conductor is equal to the current (I) multiplied by the resistance (R) that is, e = RI (2) Substituting the value of R from equation (1) in equation (2) Expressed in words, the voltage "drop" is equal to the current times the length of the con- ductor times 10.8 divided by the area in circular mils. The / in formula (3) is the length of wire measured both ways or the entire circuit, that is, IX2LX10.8 I X LX21.6 ... e = - - - = -- - -- (4) A A Where L is the distance between the gen- erating and the receiving ends. Formula (4) is used to find the drop in a line knowing the size 99 of wire, the current to be carried, and the dis- tance. If we wish to find the size of wire necessary to carry a current (I) a distance (L) with an allow- able voltage drop (e), by transposing the for- mula, Or to determine the current that may be car- ried by a wire, If it is desired to find the size of wire required to carry a certain number of lamps, substitute for (I) the number of lamps (N) multiplied by the current taken by each lamp (i) NXIXLX21.6 or A = (7) e It is sometimes more convenient to make the calculation in terms of the wattage of the lamps used, WXNXLX21.6 thenA=: ~E^ Where W watts per lamp, E = circuit volt- age at lamps and e is the voltage "drop." Application of Kelvin's Law The question of permissible voltage drop in a circuit increases in importance as the cost of energy increases. There are so many factors to be taken into consideration that it is impossible to give a complete discussion in a limited space. However, in any installation the amount of energy to be transmitted being' known, it is an easy matter to find the average kilowatt hours wa,sted in a conductor of a given resistance. With regard to the conductors it is principally a question of additional cost of copper, as the other construction charges are not greatly affected by the increase in size of the conductors. In calculating the size of wire to carry a given load, a simple application of Kelvin's law may be used. The most economical current density per million circular mils is Where L = increase in annual charges on transmission line resulting- from increasing the weight of feeders one ton, and C increase in annual operating cost and capital charges on the power station, resulting from increasing the out- put one kilowatt, A is a constant whose value is A/ Weight of conductors, Ibs. per cu. in. Specific resistance, ohms, per mil foot I AAAMAMAA/ ' For copper, A 380 Aluminum, A = 165 To obtain the economical current density it is best to make calculation using the maximum possible value of L, also calculations using the minimum possible value of L. The mean of these calculations will give the advisable cur- rent density. General Electric Company Mercury Arc Rectifiers. (P. D. WAGONER) A detailed idea of the operation of the mercury arc rectifier circuit may be obtained from Fig. 41. Assume an instant when the terminal H of the supply transformer is positive, the anode A is then positiv e and the arc is free to flow between A and B, B being the mer- cury cathode. Following the directions of the arrows still further the f(P current passes through the load J, through the reactance coil E and back to the negative ter- minal G on the trans- former. A little later when the impressed elec- tromotive force falls below a value sufficient to maintain the arc against the counter elec- tromotive force of the arc and load, the react- ance E, which heretofore Fig. 41. has been charging, now discharges, the dis- charge current being in the same direction as formerly. This serves to maintain the arc in the rectifier until the electromotive force of the supply has passed through zero, reverses and builds up to such a value as to cause A' to have a sufficiently positive value to start an arc be- tween it and the mercury cathode B. The discharge circuit of the reactance coil E is now through the arc A'B, instead of through its former circuit. Consequently the arc A'B is now supplied with current, partly from the transformer and partly from the reactance coil /;. The new circuit from the transformer is indicated by the arrows inclosed in circles. The amount of reactance inserted in the circuit re- duces the pulsations of the direct current suffi- ciently for all ordinary commercial purposes. Where it is advisable to still further reduce the amplitude of the pulsations, as, for instance, in telephone work, this is done with very slight reduction in efficiency by means of reactances- 101 3 S o 2 c a 3 aj -5 .a ty ifi S 3 !!!. t> ? * -5 ^ W g O W O 102 strength > i I 0) c O s D I -*' 3" o so t5| ^ ", < . i-i c . ei. co * I 3 III - ^ co ^J >: oi 2 gj g $ 5 S 8 8 S 8 S S S S S 2S2^g^^Sf:! ^ IS $ 8 3 S S 3 S g ^ ' eo' cd oi 5 ci * o cc t^* --< -' S S S 8 8 r. ^ ^ co o o 00 * * S S g 83 S ^ S; S ' J5 Spe 3 vac's 1 !! ii "3 SIS 111 111? 103 28, TABLE OF iN COMPARATIVE SIZES OF WIRE GAUGES DEC.MALS OF AN INCH. No. of Wife Brown & Gauge Sharpe jAttSik"? English Pn nrWash-l nam or Le 8 a ' ftESg" 1 *' Standard 000000 00000 0.58000 0.51650 0^4615 0.4305 0.500 u.ouu 0.464 0.432 0000 000 00 046000 0.40964 0.36480 0.3938 0.3625 0.3310 0.454 0.425 0.380 0.400 0.372 0.348 0.454 0.425 0.380 1 2 0.32495 0.28930 0.25763 0.3065 0.2830 0.2625 0.340 0.300 0.284 0.324 0.300 0.276 0.340 0.300 0.284 3 4 5 0.22942 0.20431 0.18194 0.2437 0.2253 0.2070 ' 0.259 0.238 0.220 0.252 0.2.<2 0.212 0.259 0.238 0.220 6 7 8 0.16202 0.14428 0.12849 0.1920 0.1770 0.1620 0.203 0.180 0.165 0.192 0.176 0.160 0.203 0.180 0.165 9 10 11 0.11443 0.10189 0.09074 0.1483 0.1350 0.1205 0.148 0.134 0.120 0.144 0.128 0.116 0.148 0.134 0.120 12 13 14 0.08081 0.07196 0.06408 0.1055 0.0915 0.0800 0.109 0.095 0.083 0.104 0.092 0.080 0.109 0.095 0.083 15 16 17 0.05706 0.05082 0.04525 0.0720 0.0625 0.0540 0.072 0.065 0.058 0.072 0.064 0.056 0.072 0.065 0.058 18 19 20 0.04^30 0.03589 0.03196 0.0475 0.0410 0.0348 0.049 0.042 0.035 0.048 0.040 0.036 0.049 0.040 0.035 21 22 23 0.02846 0.02535 0.02257 0.0317 0.0286 0.0258 0.032 0.028 0.025 0.032 0.028 0.024 0.0315 0.0295 0.0270 24 25 26 0.02010 0.01790 0.01594 0.0230 0.0204 0.0181 0.022 0.020 0.018 0.022 0.020 0.018 0.0250 0.0230 0.0205 27 28 29 0.01420 0.01264 0.01126 0.0173 0.0182 0.0150 0.016 0.014 0.013 0.0164 0.0148 0.0136 0.01875 0.01650 0.00155 30 31 32 0.01003 0.00893 0.00795 0.0140 0.0132 0.0128 0.012 0.010 0.009 0.0124 0.0116 0.0108 0.01375 0.01225 0.01125 33 34 35 0.00708 0.00630 0.00561 0.0118 0.0104 0.0095 0.008 0.007 0.005 0.0100 0.0092 0.0084 0.01025 0.00950 0.00900 36 37 38 0.00500 0.00445 0.00396 0.0090 0.0085 0.0080 0.004 0.0076 0.0068 0.0060 0.00750 0.00650 0.00575 39 40 0.00353 0.00314 0.0075 0.0070 0.0052 0.0048 0.00500 0.00450 The Edison Gauge is the area in circular mils divided by 1000. 104 osao-. <*;*-< W j Sj^^ 5t^-* d c^ * M o\ bo o v. ^ ?HK)?3 ^!i-!r-i do Ot?)-* ^C-Jv^) M i -H i-iOO OOO OOO OOO OO c d o odd odd o' c d c d o' odd d d d odd J & O s I * 1 o s I c s fM d odd odd odd odd odd odd d OO-H-I re * ir, so f^ CC <>2 22!2S5^ S2) 105 i/) CT\ vo 00 CO r}- OOONO t^vot^-coooio 1 Q ON IO CM ON t^ VO rf CO co CM > I ,-H o* o o o o o' oo'o'o'oo W MtJ T-H TH CM co co T}- vd t-^ ON CNJ 10 o" 3 I r-H r-, CM W & k o " . IOOCCIOCOON cO^-CMTfOON VOiOTTCOCMCM r-\ r-( r- 1 O O O o'oo'ooo' oo'oo'o'o W OOOOt^.CMOO ON ^- ON CO r- ON ON r-l 00 CO CM O Tf CO CM CVl i I r-H o ^y \O CO ON fO VO Ti-cOONOcOlO I^SSIS SIS32S o* o' o* o' o" o o o" o o o* o CO rMO ^O t^.OO 106 3 CM w CO O CO \O -l MD vd ^ 10' o -H ^J- CO CM ro r^ IO ^ d P H Si ^SogSg IISllI j oo o o o o o o o o o o p< . PL, PO CM CM Ox Ox TJ- CM oo 1-1 \nt^ Tf sj^ssizi O CM \O O O CM -H f-H r-( CM CM CO PH 8 g O O O O O O 000000 O O O O OO H CO O I s - Ox t^ IO OO IO ^O CM VO CM OO Ox O> ^O C^J CM W O OO Vj IO ^ CO 'M CM 1 r~( ^ i-H -H O O O O o' o o o o' o O QO CM rO OO Ox q o o q o q o* o o o o o o* Ox O i-> CM CO rf IOVO t^ 00 Ox O 5^ 107 Watt-Hour Meters The Watt-hour meters on the market at the present time are, in the main, of two general types, the induction type and the Thomson or motor type. There are several makes includ- ing- meters for various conditions of service, but the majority are an adaptation of one or the other of these two types. With this in mind, a brief discussion is given herewith on the theory of each type. The Induction Watt-hour Meter is suitable for alternating current circuits only. In this meter a tri-polar magnet of laminated iron exerts a driving torque on an aluminum disc. The two positive lugs Li Li of the magnet are wound with coarse wire to carry the line current, and the middle lug I>2 is wound with fine wire, which is connected across the main as shown in Fig. 42. Fig. 42 As before stated, this meter is used on alternat- ing current circuits. The surging of the cur- rent back and forth through the coils of Li Li sets up a changing flux in the lugs, producing in turn a surging current through the disc under L,2. This in turn sets up a changing flux in Li>, producing an electro-motive-force equal to the line voltage at each instant. Furthermore, this flux induces a proportional electro-motive : force about I>2 in the disc, A current is set up in the disc in the direction of the induced electro-mo- tive-force and proportional to the line voltage at each instant. This current flowing under Li Li causes the flux under them to exert a torque on the disc which is proportional at each instant to both line current and the line voltage, so that the driving torque is at each instant propor- tional to the load delivered to the receiving cir- cuit. The motion of the disc is damped by per- manent magnets so that the speed is propor- tional to the driving torque. The total work delivered to the receiving circuit is registered on the dials which are driven by the spindle on which the disc is mounted. The Thomson Watt-hour Meter can be used on either direct or alternating current lines. This meter (Fig. 43) is a small electric motor without iron parts. The field coils carry the line ins Shaft Operating Dials Fig. 43 current and the armature is connected across the line. The speed of reduction is damped by the electro-magnetic drag upon the copper disc caused by the permanent magnets DD. The driving torque exerted upon the armature is proportional at each instant to the current both in the field coils and in the armature, that is, it is proportional both to the line current and to the line voltage. The damping force exerted on the disc by the magnets is proportional to the speed, so that the total number of revolutions on the dials is always proportional to the watt- hours of work delivered to the receiving circuit. Extracts from the National Electrical Code as issued by the National Board of Fire Underwriters. 22. Incandescent Lamps in Series Circuit. (a) Conductors must be installed as follows 1 1. Must have an approved rubber insulating covering:. 2. Must be arranged to enter and leave the building through an approved double-con- tact service switch, mounted in a non-combusti- ble case, kept free from moisture, and easy of access to police or firemen. 3. Must always be in plain sight, and never encased, except when required by the Inspec- tion Department having jurisdiction. 4. Must be supported on glass or porcelain insulators, which separate the wire at least one inch from the surface wired over and must be kept rigidly at least eight inches from each other, except within the structure of lamps, on hanger- boards or in cut-out boxes, or like places, where a less distance is necessary. 5. Must, on side walls, be protected from mechanical injury by a substantial boxing, re- taining an air space of one inch around the con- ductors, closed at the top (the wires passing through bushed holes) , and extending not less than seven feet from the floor. When crossing floor timbers in cellars, or in rooms where they might be exposed to injury, wi^es must be at- tached by their insulating supports to the under side of a wooden strip not less than one-half an inch in thickness. Instead of the running- boards, guard strips on each side of and close to to the wires will be accepted, These strips to be not less than seven-eighths of an inch in thickness and at least as high as the insulators. (b) Kach lamp must be provided with an automatic cut-out. (c) Each lamp must be suspended from a hanger-board by means of rigid tube. Hanger- board (73) must be so constructed that all wires and current-carrying devices thereon will be ex- posed to view and thoroughly insulated by being mounted on a non-combustible non-ab- sorptive insulating substance. All switches at- tached to the same must be so constructed that they shall be automatic in their action, cutting off both poles to the lamp, not stopping between points when started and preventing an arc be- tween points under all circumstances. (d) No electro-magnetic device for switches and no multiple-series or series-multiple system of lighting will be approved. (e) Must not under any circumstances be attached u> gas fixtures. 110 23. Automatic Cut outs. (d) Must be so placed that no set of incan- descent lamps, requiring more than 660 watts, whether grouped on one fixture or on several fixtures or pendants, will be dependent upon one cut-out. Special permission may be given in writing by the Inspection Department having jurisdiction, for departure from this rule, in the case of large chandeliers. (For exceptions, see rule on thea- ter wiring). All branches or taps from any three-wire system which are directly connected to lamp sockets or other translating devices, must be run as two-wire circuits, if the fuses are omitted in the neutral, or if the difference of po- tential between the two outside wires is over 250 volts, and both wires of such branch or tap cir- cuits must be protected by proper fuses. 25. Electric Heaters. It is often desirable to connect in multiple with the heaters and between the heater and the switch controlling same, an incandescent lamp of low candle-power, as it shows at a glance whether or not the switch is open, and tends to prevent its being left closed through oversight- (a) Must be protected by a cut-out and con- trolled by indicating switches. Switches must be double pole except when the device con- trolled does not require more than 660 watts of energy. (b) Must never be concealed, but must at all times be in plain sight. Special permission may be given in writing by the Inspection De- partment having jurisdiction for departure from this rule. (c) Flexible conductors for smoothing irons and sad irons, and for all devices requiring: over 250 watts must have an approved insulation and covering. (d) For portable heating devices the flexi- ble conductors must be connected to an ap= proved plug device, so arranged that the plug will pull out and open the circuit in case any abnormal strain is put on the flexible conductor. This device may be stationary, or it may be placed in the cord itself. Th e cable or cord must be attached to the heating apparatus in such manner that it will be protected from kinking, chafing or like injury at or near the point of connection. (e) Smoothing irons, sad irons and other heating appliances that are intended to be ap- plied to inflammable articles, such as clothing, must conform to the above rules so far as they apply. They must also be provided with an ap- proved stand, on which they should be placed when not in use. (f) Stationary electric heating apparatus, 111 such as radiators, ranges, plate warmers, etc., must be placed in a safe location, isolated from inflammable materials, and be treated as sources of heat. Devices of this description will often require a suitable heat-resisting material placed between the device and its surroundings. Such protec- tion may best be secured by installing two or more plates of tin or sheet steel with a one-inch air space between or by alternate layers of sheet steel and asbestos with a similar air space. (g) Must each be provided with name-plate, giving the maker's name and the normal capac- ity in volts and amperes. 31. Sockets. (For construction of Sockets see No. 72). (a; In rooms where inflammable gases may exist, the incandescent lamp and socket must be enclosed in a vapor-tight globe and supported on a pipe-hanger, wired with approved rubber- covered wire soldered directly to the circuit. (b) In damp or wet places "waterproof" sockets must be used. Unless made upon fix- tures they must be hung by separate stranded rubber-covered wires not smaller than No. 14 B & S gauge, which should preferably be twisted together when the pendant is over three feet long. These wires must be soldered directly to the circuit wires but supported independently of them. (c) Key sockets will not be approved if in- stalled over specially inflammable stuff, or where Exposed to flyings of combustible material. Flexible Cord. (For construction of Flexible Cord see No. 54) . (a) Must have an approved insulation and covering. (b) Must not, except in street railway prop- erty, be used where the difference of potential between the two wires is over 300 volts. (c) Must not be used as a support for clus- ters. (d) Must not be used except for pendants, wiring of fixtures, portable lamps or motors, and portable heating apparatus. For all portable work, including those pend- ants which are liable to be moved about suffi- ciently to come in contact with surrounding objects, flexible wires and cables especially de- signed to withstand this severe service must be used. When necessary to prevent portable lamps froni coming in contact with inflammable ma- terials, or to protect them from breakage, they must be surrounded with a substantial wire guard. (e) Must not be used in show windows or 112 show cases except when provided with an ap= proved metal armor. (f) Must be protected by insulating bush- ings where the coixi enters the socket. (g) Must be so suspended that the entire weight of the socket and lamp will be borne by some approved method under the bushing in the socket, and above the point where the cord conies through the ceiling block or rosette, in order that the strain may be taken from the joints and binding screws. 37. Decorative Lighting Systems. Systems of Decorative Lighting, provided the difference of potential between the wires of any circuit shall not be over 150 volts and also pro- vided that no group of lamps requiring more than 1,320 watts shall be dependent on one cut- out. 71. Rosettes. Ceiling rosettes, both fused and f useless, must be constructed in accordance with the fol- lowing specifications: (a) Base. Current carrying parts must be mounted on non-combustible, non-absorptive, insulating bases. There should be no openings through the rosette base except those for the supporting screws and in the concealed type for the conduc- tors also, and these openings should not be made any larger than necessary. There must be at least one-fourth inch space, measured over the surface, between supporting screws and current-carrying parts. The sup- porting screws must be so located or counter- sunk that the flexible cord cannot come in con- tact with them. Bases for the knob and cleat type must have at least two holes for supporting screws; must be high enough to keep the wires and terminals at least one-half inch from the surface to which the rosette is attached, and must have a porce- lain lug under each terminal to prevent tlie rosette from being placed over projections which would reduce the separation to less than one- half inch. Bases for the t moulding and conduit box types must be high enough to keep the wires and terminals at least three-eighths of an inch from the surface wired over. (b) Mounting. Contact pieces and terminals must be secured in position by at least two screws, or made with a square shoulder, or otherwise arranged to pre- vent turning. The nuts or screw heads on the under-side of the base must be countersunk not less than one- eighth of an inch and covered with a water- proof compound which will not melt below 150 degrees Fahrenheit (65 degrees Centigrade). 72. Sockets. (For installation rules see No. 31.) (b) Ratings. Key Sockets. The standard key socket (any socket haying Standard Edison screw shell and ordinary "slow make" switch) to be rated 250 watts, 250 volts. Marking may be 250 W,, 250 V. This rating shall not be interpreted to permit the use, at any voltage, of current above 2K amperes on any standard key or pull socket. A key socket with Standard Edison shell and special switch which "makes" and "breaks" with a quick snap and does not stop when motion has been once imparted by the button or handle may be rated 660 watts, 250 volts (660 W., 250 V.) . Miniature and Candelabra key sockets to be rated 75 watts. 125 volts (75 W., 125 V.). Keyless Sockets. Standard keyless sockets with Standard Edison screw shell to be rated 66U watts, 250 volts ( 660 W. . 250 V.) . This rating shall not be interpreted to permit the use, at any volt- age, of current above 6 amperes on any keyless socket. Weatherproof sockets with Standard Edison shell and having no exposed current carrying parts may be rated 660 watts, 600 volts (600 W., 600 V.). Minature and candelabra keyless sockets to be rated 75 watts. 125 volts (75 W., 125 V.). Double Ended Sockets. Each Edison screw shell to be rated at 250 watts, 250 volts for key type, 660 watts, 250 volts for keyless type, the de- vices being marked with a single marking apply- ing to each lamp holder. These ratings shall not be interpreted to per- mit the use, at any voltage, of current above 2Y Z amperes for key type, or above 6 amperes for keyless types. (g) Spacing. Points of opposite polarity must everywhere be kept not less than three sixty-fourths of an inch apart, unless separated by a reliable insulation. (h; Connections. The connecting points for the flexible cord must be made to very securely grip a No. 16 or 18 B. & S. gauge conductor. An up-turned lug, arranged so that the cord may be gripped be- tween the screw and the lug in such a way that it cannot possibly come out is strongly advised- (i) Lamp Holder. The socket must firmly hold the lamp in 114 place so that it cannot be easily jarred out and must provide a contact good enough to prevent undue heating with the maximum current al- lowed. The holding pieces, spring and the like, if a part of the circuit, must not be sufficiently exposed to allow them to be brought in contact with anything outside of the lamp and socket. (j) Base. The base on which current carrying parts are mounted must be of porcelain and all insulating material used must be of approved material. (k) Key. The socket key-handle must be of such a material that it will not soften from the heat of a fifty candle-power lamp hanging downwards from the socket in air at 70 degrees Fahrenheit (21 degrees Centigrade), and must be securely, but not necessarily rigidly attached to the metal spindle which it is designed to turn. (1) Sealing. All screws in porcelain pieces which can be firmly sealed in place, must be so sealed by a waterproof compound which will not melt below 200 degrees Fahrenheit (93 degrees Centigrade) . (m) Putting Together. The socket as a whole must be so put to- gether so that it will not rattle to pieces. Bayo- net joints or an equivalent are recommended. (o) Keyless Sockets. Keyless sockets of all kinds must comply with the requirements for key sockets as far as they apply. (p) Sockets of Insulating Material. Sockets made of porcelain or other insulating material must conform to the above require' ments as far as thev apply, and all parts must be strong enough to withstand a moderate amount of hard usage without breaking. Porcelain shell sockets being subject to breakage and constitutin g a hazard when broken, will not be accepted for use in places where they would be exposed to hard usage. number of Standard 10 C.P. Incandescent Lamps. }*(i_ Ceiling Outlet; Combination, -i- indicates 4-10 C.P. Standard ^ - Incandescent Lamps and 2 Gas Burners. Iff If gas only. JJvv Bracket Outlet; Electric only. Numeral in center indicates %**** number of Standard 10 C.P. Incandescent Lamps. Bracket Outlet; Combination. 4 indicates 4-10 C.P. Standard < 2 Incandescent Lamps and 2 Gas'liurners. |-JK If gas only. |_hr| Wall or Baseboard Receptacle Outlet. Numeral in center pp-* indicates number of Standard 10 C.P. Incandescent Lamps . M Floor Outlet Numeral in center indicates number of Standard 10 C.P. Incandescent Lamps. _ Outlet for Outdoor Standard or Pedestal; Electric only. *-* 6 Numeral indicates number of Standard 10 C.P.Lamps. *gy(Q Outlet for Outdoor Standard or Pedestal; Combination -J JL indicates 0-10 C.P.Standard Incan. Lamps; 6 Gas Burners. JDJ Drop Cord Outlet. Oue Light Outlet, for Lamp Receptacle. ^ Arc Lamp Outlet. ^ Special Outlet, for Lighting, Heat'ng and Power Current. ^ as described in Specifications. C=OO Ceiling Fan Outlet. S 1 & P. Switch Outlet. yj L>. P. Switch Outlet. S :; 3- Way Switch Outlet. g> 4- Way Switch Outlet. S D Automatic Door Switch Outlet Show as many Symbols as there are Switches. Or iu case of a very large group of Switches. indicate number of Switches b\ a Roman numeral, thus: SlXll. meaning 12 Single Pole Switehe Describe Type of Switch^in Specifications, that is. Flush or Surface, Push Button or Snap. Electrolier Switch Outlet. Q Meter Outlet. flOH Distribution Panel. $$m&\ Junction or Pull Box. J^ Motor Outlet; Numeral ia center indicaU-e Horse Power. [><] Motor Control Outlet. =trzt= Trans former. - _ Main or Feeder run concealed under Floor. Main or Feeder run concealed uud^r Floor above. Main or Feeder run exposed. Branch Circuit run concealed under Floor. Branch Circuit ran concealed under Floor above. - Branch Circuit run exposed. ---- Pole Line. Riser. (3 . Telephone Outlet: Private Service . |4 Telephone Outlet; Public Service. Q Bell Outlet. Q/ Buzzer Outlet. 02 Push Button Outlet; Numeral indicates number of Pushed. <> Annunciator; Numeral indicates number of Points. _^ Speaking Tube. -ue to the increase of resistance the regulation in- creases with rise of temperature. Transformer Testing for Central Stations The financial success or failure of a lighting or power plant is dependent on the efficiency of the system. In alternating current distribution the transformers are frequently scattered in large numbers throughout the system and their cumulative losses greatly effect the efficiency of the entire system. It is therefore essential to the self-protection of Central Stations that suffi- cient tests are made on the transformers to be sure that the guarantees are fulfilled. The fol- lowing tests can be made without a great outlay for instruments. Insulation Test Fig. 46. 1. Between primary and all other parts. 2. Between secondary and all other parts. 3. Between turn sand sections of the windings. The method of connection is shown in Fig. 46. In applying the high potential test to one wind- ing the remaining winding should be carefully grounded to the core and frame to avoid static- ally induced strains. All primary leads should be connected together as well as secondary leads, in order to secure throughout the winding a uniform potential strain during the test. 1. Set the spark gap for a voltage 10 per cent, in excess of that which is to be applied. (See Table 31), 2. By means of the regulator on the low volt- age side adjust the testing outfit to deliver minimum voltage. 3. Connect the apparatus to be tested to the high voltage side of the testing outfit. 4. Close low voltage switch and gradually in- crease the voltage until the desired potential is indicated on the electrostatic voltmeter. 5. Reduce the voltage slowly. 124 If the insulation under test be good there will be no difficulty in bringing- the potential up to the desired value, provided the transformer be of sufficient capacity. If, however, the insula- tion be weak or defective it will be impossible to obtain a high voltage, and an excessive current will be indicated by the ammeter. A breakdown in insulation will result in a drop in voltage in- dicated by the electrostatic voltmeter and by an excessive current. 31. Standard Spark Gap Voltage in Kilovolts 5 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Core Loss < Ope a Circuit-> Fig. 47. Gap in Inches .2 .5 1.0 1.65 2.50 3.50 4.60 5.85 7.10 8.35 9.50 10.70 11.85 12.98 14.00 15.00 1. Estimate the capac- ity of the instruments required. 2. Connect the selected instruments as shown in Fig. 47 to the low potential side of transformer on test, the high potential side being on open circuit. The generator speed should be observed by a tachometer or speed counter in case a fre- quency meter is not available. 3. Connect leads from the transformer on test to the leads from the switch- board or source of power through a double pole, sin- gle throw switch. 125 4. 'dose the switch' and make a preliminary reading of -the instruments at approximately the voltage and frequency required. 5. Adjust the voltage and frequency of the circuit as desired and make simultaneous obser- vations of the wattmeter, voltmeter, ammeter and frequency meter. 6. Record the results and note the numbers of the instruments used with their correspond- ing- constants. NOTE: The generator should carry no other load during the test. 7. Calculate the losses in the voltmeter and in the pressure coil of the wattmeter and sub- tract them from the observed reading of the wattmeter. The result is the core loss of the transformer. NOTE: The loss in the voltmeter and in the pressure coil of the wattmeter are equal in each E 2 case to , R being the resistance of the coil in question. Measurement of Resistance Transformer under Test Fig. 48 This method of finding the resistance of a transformer is simply an- application of Ohm's Law, that is, R = y . Direct current is used and the connections are as shown in Fig. 48. Simul- taneous readings should be taken on the volt- meter and ammeter at different values of cur- rent. Reduce the value of resistance to standard room temperature of 25 C. using the following equation: Resistance at 25 C. = R R = resistance at t C. t = temp, of transformer on test, Impedance Loss Impedance may be considered as constant at all loads. It is generally measured at full load current, and the impressed voltage is then known as the impedance volts, and, when ex- pressed in per cent, of the normal rated voltage of the transformer, as the per cent, impedance drop. 126 Transformer under Test Fig. 49 Connections should be as in Fig. 49. 1. Short circuit one of the windings of the transformer, preferably the secondary. 2. Adjust the voltage to give full load current in the winding of the transformer; then make simultaneous readings of the voltmeter, am- meter and frequency meter. Record the results and calculate the imped- ance. In the equation, TC I= =VR 2 + (27rnL) 2 the expression v / R 2 -|-(2 * n L)~ is'the im- pedance in ohms. Polarity When transformers manufactured by different companies are to be run in parallel, it is necessary to test them in order to avoid the possibility of connecting them in such a way as to short-cir- cuit the one on the other. A Fig. 50 Refer to Fig. 50. In the connections shown the leads are so brought out that the primary and secondary form a continuous winding, uniform in direction when B and D are connected to- gether. Consequently, if with B and 1) con- nected a given voltage is impressed from A to B the result of the voltage from A to C will be more than that impressed at A B if the leads have been properly brought out, and less than the voltage impressed at A B if they have not been properly brought out. 127 Transformer Connections Delta-Delta Connection Delta -Delta Fig. 51 The voltage per transformer is the same as that between the line wires, the current per transformer^ equal to the current per line wire divided by \/3. Star or Y Connection Wdv-T tTflmrH Star or Y Connection Fig. 52 The current per transformer is the same as that per line wire; the voltage per transformer isjiqual to the voltage between wires divided by S-. Delta=Y Connection Delta -Y" Connection Fig. 53 Y=Delta Connection " Delta-Connection Fig. 54 128 T-Connection (Scott Transformer) ' ! T" Connection. Fig. 55 In this scheme the voltage impressed across one transformer is only 86.6 per cent, of that im- pressed across the other. Method of Cooling Transformers 1. Self-cooling dry transformers. 2. Self-cooling oil filled transformers. 3. Transformer cooled by forced current of 4. Transformer cooled by forced current of water. 5. Transformer cooled by combinations of both. Limiting Temperature Rise The temperature rise should not exceed 50 C. in electric circuits by resistance and in other parts by thermometer. Overload Capacity Constant potential transformers, 25 per cent, for two hours, except in transformers connected to apparatus for which a different overload is guaranteed, in which case the same guarantee shall apply for the transformer as for the appa- ratus connected thereto. Standard Ratios It is recommended that the standard trans- former ratios should be applicable to the follow- ing voltages, which are standard: 6600; 11,000; 22,000; 33,000; 44,000; 66,000; 88,000; 110,000. The ratio will usually be an exact multiple of 5 or 10. Rules for Installing and Operating Tranformers. Must not be placed in any but metallic or other non-combustible cases. Must be constructed to comply with the following tests : 1. Shall be run for eight consecutive hours at full load in watts under conditions of service, and at the end of that time the rise in temperature, as measured by the increase of resistance of the primary coil shall not exceed 135 F. 2. The insulation of transformer when heated shall withstand continuously for rive minutes a 129 difference of potential of 10.000 volts (alternating-) between primary and secondary coils and core, and between the primary coils and core; 'also must withstand a no load run at double voltage for 30 minutes. In Central or sub-stations the transformers must be so placed that the smoke from the burn- ing out of the coils, or the boiling over of the oil, where oil filled cases are used, can do no harm. The neutral point of the transformer or the neutral wire of distributing systems may be grounded and when grounded the following rules must be complied with. 1. Transformers feeding two wire systems must be grounded at the center of the second- ary coils. 2. Transformers feeding systems with a neut- ral wire must have the neutral wire grounded at the transformer and at least every 250 ft. beyond. In general, in order to obtain minimum operat- ing costs, transformers of the present standard performances should be used on a load which will bring them up to the maximum safe tempera- ture rise. Constant Current Transformers The Constant Current Transformer in its sim- plest type consists of a core of the double mag- netic circuit type with three vertical legs and two coils placed around the central leg. The primary is fixed and the secondary is suspended and balanced by counter weights so that it can move up and down. A flow of current in the coils causes a repulsion between them, causing them to separate to the position for which they are balanced. An increase of current due to cut- ting out of series lamps, for example, causes them to separate farther, increasing the leakage and thereby cutting down the induction. With any current less than normal the repelling force diminishes, and the primary and secondary coils approach each other thereby restoring the cur- rent to its normal value. The General Electric Company has recently designed a new edgewise wound transformer, with concentric coils and cruciform core, giving better efficiency, higher power factor and closer regulation. It is so designed that the short cir- cuiting of the secondary at any time will not cause any serious damage. It will regulate from no load to full load within 1/10 of an ampere, above or below normal rated current on any pri- mary voltage within 5 per cent of the normal rated value. By means of a slight adjustment it can be adapted for any secondary current within 7 1/2 per cent of normal rated value, thus allow- ing the customer to order lamps of other than exact standard values. 130 Trigonometric Functions and Rules. 1. The sine of an angle is the ratio of the opposite leg to the hypotenuse. 2. The cosine of an angle is the ratio of the adjacenl leg to the hypotenuse. 3. The tangent of an angle is the ratio of the opposite leg to the adjacent. 4. The cotangent of an angle is the ratio of the adjacent leg to the opposite. 5. The secant of an angle is the ratio of the hypotenuse to the adjacent leg. 6. The cosecant of an angle is the ratio of the hypotenuse to the opposite leg. 7. The versed sine of an angle a is equal to 1 cos a. 8. The coversed sine of an angle a is equal to 1 sin a. Sin x =: --- : Cos x =: - ; Tan x = sin'- x -f cos 2 x = 1 ; 1 + tan 2 x = sec- x : 1 -fcot 2 x = csc 2 x. ( TT I \ n COS X = sill - -- -- x . sin (if x ) = sin x ; cos (* x ) = cos x ; tan ( if x ) = tan x sin ( x -}- y ) = sin x cos y + cos x sin y. sin ( x y ) = sin x cos y cos x sin y. cos ( x + y ) cos x cos y sin x sin y. , . v tan x -J- tan y tan ( x + y ) = 1 tan x tan y , tan x tan y tan ( x y ) = 1 + tan x tan y sin 2 x 2 sin x cos x; cos 2 x = cos- x sin 2 x ; 2 tan x tan 2 x = - - 5 . 1 tan 2 x . XX X . X sin x = 2 sm cos : cos. x = cos 2 sin 2 . 2 tany l-tan 2 y cos 2 x= H r-cos2x; sin 2 x=: cos2x. 131 1 -f cosx = 2 cos' 2 -^; 1 cos x = 2 sin 2 -. !f= ^L5iI ; -- 1 -f cos x sin x + sin y = 2 sin (x -f y) cos (x y ) sin x sin y = 2 cos ^~ ( x + y) sin (x y) cos x -j- cos y = 2 cos (x + y) cos (x y) cosx cosy == 2 sin (x -f- y) sin (x y) Law of sines sin A sin B sin C Where A is the angle opposite side a B is the angle opposite side b C is the angle opposite side c Law of cosines as rr b 2 + c 2 2 be cos A The following table gives the signs for the trigo- nometric functions in the various quadrants : Quadrant sin cos tan cot sec CSC First + + + + + -f Second + - + Third + + - - Fourth ~ 1 + + - In the diagram below (Fig. 56) the functions are positive in quadrants denoted by arrows. Mensuration. Square Root The method of extracting square root is best shown by the use of an example: Find the square root of 2809, or, in other words, find the length of the side of a square which contains 2809 units : 2 x 50 = 100 3 103 25 309 309 Fig. 57 First divide the number into periods of two fig- ures each, starting from the decimal point. The square root will have one figure for each period in the square, so the side of this particular square will be represented by tens, and obviously by 5 tens since the largest square in 28 is 25. This square subtracted leaves 309 square units to be taken into account. These 309 square units can be divided up into three parts, consisting of two strips B and C, 50 units long and a smaller square D at the corner, whose dimensions we do not yet know. The combined length of B and C is 2 x 50, or 100, and 100 is contained in 309, 3 times. Now assuming the width of these strips to be 3 the area of the strips will be 300, and that of the square will be 9, making a total of 309 which completes the square. Rule to be Followed in Extracting the Square Root of a Number. Separate the number into periods of two figures each, beginning at the decimal point. Find the greatest square in the left hand period and write its root for the first figure of the required root. Square this root and subtract the result from the left hand period and annex to the remainder the next period for a dividend. Double the root already found and multiply it by 10 for a trial divisor, and divide it into the dividend, making allowance for the fact that the dividend must contain in addition to the pro- duct of the trial divisor and the quotient obtained, the square of the quotient itself. Subtract this sum of the products from the dividend, annex to the remainder the next period, and proceed as before. CUBE ROOT Rule to be Followed in Extracting the Cube Root of a Number. Separate the number into periods of three figures each, beginning at the decimal point. 133 Find the greatest cube in the left hand period and write its root for the first figure of the required root. Cube this root, subtract the result from the left hand period and annex to the remainder the next period for a dividend. Take three times the square of the root already found, consider it as tens for a trial divisor and divide it into the dividend. The quotient or the quotient diminished will be the second part of the root. To this partial divisor add three times the pro- duct of the first part of the root, considered as tens by the second part, and also the square of the second part. Their sum will be the complete divisor. Multiply the complete divisor by the second part of the root and subtract the product from the dividend. Continue this until all the figures of the root have been found. Illustration and Explanation of the Above Rule Fig. 58 Find edge of cube whose contents are 13,824 units. 13824 1 24 As there are two periods in this fig- ure the root will be in the order of tens- The largest cube in - 3X2Q 2 1200 (4) X 1200 = 4800 (4) X 4X3 X 20 = 960 (4) = 64 co ?4 . the first period is 8. This subtracted from the number This remainder must 5824 leaves 5,824 cubical units. be composed of seven parts, C, B, D, E, F, G and H. The sum of the areas of the faces of C, B and D is 20 2 X 3 1200. This is contained in 5,824 four times. With this as a trial quotient we can now find the contents of the additional parts. The contents of C, B and D is 1200 X 4 = 4800; of E, F and G is 3 (4 X 4 X 20) = 960; of H is 4 s 64, making a total of 5,824. 134 Figr. j 135 Formulae for Finding Area and Volumes of Geometrical Figures. Meaning of Symbols Used A = Area of plane surface d = Diameter R = Radius V - Volume p = Perimeter b = Base h Altitude C = Area of convex surface S = Area of entire surface ir = 3.1416 Circle A = 7T R-' p 2 7T R Triangles Fig. a a = V b 2 4- h 2 A = bh 2 Fig. b c = 1 Fig. c c = 1 jj Rectangle Fig. d A = rib Paralellogram Fig. e A = hb Trapezoid Fig. f A = |-h (a + b) Trapezium Fig. g A f(h-f-h / ) + ~he + j h' g =y [f (h + h') + he -f h' g] Ellipse A= D d Sector Fig. i A = ~l R A - n - .008727 Segment Fig.j A=-| [/R-c (R-h)] Cylinder C= * dh S = 2 ir R h -h 2 T R* V= IT R2h Cone C = % TT d / (/ = Slant height) S = IT R / + TT R2 V= 1/3 TT R2 h Sphere S =1 4 TT R2 7T d- Circular Ring r = Radius of cross section R = Mean radius of ring S = 4 * R r V = 2 T R r 2 Frustum of a Cone C = ^y- (D + d) (d = Diameter of upper base ; D = Diameter of lower base) S = ^- (D + d) -h - (D2 + d) Pyramid / = Slant altitude p = Perimeter of base C = 1/2 p / S = 1/2 p / + area of base V = 1/3 area of base X h 137 Frustum of a Pyramid C = 1/2 / (P + P) S = 1/2 (P + P) / + A + a V=l/3h (A -fa 4V All) a Area of upper base A = Area of lower base p Perimeter of upper base P = Perimeter of lower base Centigrade and Fahrenheit Scales Temperature Centigrade Fahrenheit Centigrade Fahrenheit 32 50 122 5 41 55 131 10 50 60 140 15 59 65 149 20 68 70 158 25 77 75 167 30 86 80 176 35 95 85 185 38 100.4 90 194 40 104 95 203 42 107.6 100 212 45 113 Temp. C = 5/9 (Temp. F 32) Temp. F = 9/5 (Temp. C + 32) 138 32. Squares, Cubes, Square] Roots, Cube Roots and Reciprocals. No. Squires Cubes Square Roots Cube Roots Recip- rocals 1 1 1 1.0000 1.0000 1.0000 2 4 8 1.4142 1.2599 .5000 3 9 27 1.7320 1 .4422 .3333 4 16 64 2.0000 1.5874 .2500 5 25 125 2.2360 1.7099 .2000 6 36 216 2.4494 1.8171 .1666 7 49 343 2.6457 1.9129 .1428 8 64 512 2.8284 2.0000 .1250 9 81 729 3.0000 2.0800 .1111 10 100 1000 3.1622 2.1544 .1000 11 121 1331 3.3166 2.2239 .0909 12 144 1728 3.4641 2.2894 .0833 13 169 2197 36055 2.3513 .0769 14 196 2744 3.7416 2.4101 .0714 15 225 3375 3.8729 2.4662 .0666 16 256 4096 4.0000 2.5198 .0625 17 289 4913 4.1231 2.5712 .0588 18 324 5832 4.2426 2.6207 .0555 19 361 6859 4.3588 2.6684 .0526 20 400 8000 4.4721 2.7144 .0500 21 441 9261 4.5825 2.7589 .0476 22 484 10648 4.6904 2.8020 .0454 23 529 12167 4.7958 2.8434 .0434 24 576 13824 4.8989 2.8844 .0416 25 625 15625 5.0000 2.9240 .0400 26 676 17576 5.0990 2.9624 .0384 27 729 19683 5.1961 3.0000 .0370 28 784 21952 5.2915 3.0365 .0357 29 841 24389 5.3851 3.0723 .0344 30 900 27000 5.4772 3.1072 .0333 31 961 29791 5.5677 3.1413 .0322 32 1024 32768 5.6568 3.1748 .0312 33 1089 35937 5.7445 3.2075 .0303 34 1156 39304 5.8309 3.2396 .0294 35 1225 42875 5.9160 3.2710 .0285 36 1296 46656 6.0000 3.3019 .0277 37 1369 50653 6.0827 3.3322 .0270 38 1444 54872 6.1644 3.3619 .0263 39 1521 59319 6.2444 3.3912 .0256 40 1600 64000 6.3245 3.4199 .0250 41 1681 68921 6.4031 3.4482 .0243 42 1764 74088 6.4807 3.4760 .0238 43 1849 79507 6.5574 3.5033 .0232 44 1936 85184 6.6332 3.5303 .0227 45 2025 91125 6.7082 3.5568 .0222 46 2116 97336 6.7823 3.5830 .0217 47 2209 103823 6.8556 3.6088 .0212 48 2304 110592 6.9282 3.6342 .0208 49 2401 117649 7.0000 3.6593 .0204 139 32. Squares, Cubes, Square Roots, Cube Roots and Reciprocals. Continued. No. Squares Cubes Square Roots Cube Roots Recip- rocals 50 2500 125000 7.0710 3.6840 .0200 51 2601 132651 7.1414 3.7084 .0196 52 2704 140608 7.2111 3.7325 .0192 53 2809 148877 7.2801 3.7562 .0188 54 2916 157464 7.3484 3.7797 .0185 55 3025 166375 7.4161 3.8029 , .0181 56 3136 175616 7.4S33 3.S258 .0178 57 3249 185193 7.5498 3.8485 .0175 58 3364 195112 7.6157 3.8708 .0172 59 3481 205379 7.6811 3.8928 .0169 60 3600 216000 7.7459 3.9148 .0166 61 3721 226981 7.8102 3.9364 .0163 62 3844 238328 7.S740 3.9578 .0161 63 3969 250047 7.9372 3.9790 .0158 64 4096 262144 8.0000 4.0000 .0156 65 4225 274625 8.0622 4.0207 .0153 66 4356 287496 8.1240 4.0412 .0151 67 4489 300763 8.1853 4.0615 .0149 68 4624 314432 8.2462 4.0816 .0147 69 4761 328509 8.3066 4.1015 .0144 70 4900 343000 8.3666 4.1212 .0142 71 5041 357911 8.4261 4.1408 .0140 72 5184 373248 8.4852 4.1601 .0138 73 5329 389017 8.5444 4.1793 .0136 74 5476 405224 8.6023 4.1983 .0135 75 5625 421875 8.6602 4.2171 .0133 76 5776 438976 8.7177 4.2358 .0131 77 5929 456533 8.7749 4.2543 .0129 78 6084 474552 8.8317 4.2726 .0128 79 6241 493039 8.8881 4.2908 .0126 80 6400 512000 8.9442 4.3088 .0125 81 6561 531441 9.0000 4.3267 .0123 82 6724 551368 9.0553 4.3444 .0121 83 6889 571787 9.1104 4.3620 .0120 84 7056 592704 9.1651 4.3795 .0119 85 7225 614125 9.2195 4.3968 .0117 86 7396 636056 9.2736 4.4140 .0116 87 7569 658503 9.3273 4.4310 .0114 88 7744 681472 9. -808 4.4479 .0113 89 7921 704969 9.4339 4.4647 .0112 90 8100 729000 9.4868 4.4814 .0111 91 8281 753571 9.5393 4.4979 .0109 92 8464 778688 9.5916 4.5143 .0108 93 8649 804357 9.6436 4.5306 .0107 94 8836 830584 9.6953 4.5468 .0106 95 9025 857375 9.7467 4.5629 .0105 96 9216 884736 9.7975 4.5788 .0104 97 9409 912673 9.8488 4.5947 .0103 98 9604 941192 9.8994 4.6104 .0102 99 9801 970299 9.9498 4.6260 .0101 100 10000 1000000 10.0000 4.6415 .0100 140 Rates The cost of^'generating and delivering elec- trical energy may be considered as divided into two parts, running expenses and standing ex- penses : The running expenses comprise the cost of fuel, labor, repairs, supplies and water, and are proportional to the power used. The stand- ing expenses consist of depreciation, interest and general expenses. The standing expenses may be regarded as fixed, yet they are de- pendent on the character of the load, or rather on the load factor. From 60 to 70 per cent, of the entire expense is represented by the standing expense so that the rate charge per kw-hr. will increase rapidly when conditions demand a high standing expense. In adjusting rate schedules the following fac- tors demand first consideration: The con- sumer's "demand" on the capacity of his install- ation or connected load for drawing on the station; the number of hours use to which he puts his capacity; the "interweave" or variation in the consumer's use of service; the cost of gen- erating the current itself. In any receiving in- stallation it is probable that the consumer's de- mand will seldom reach the maximum of his installed capacity, yet when it does he wishes good service, and the central station must be able to supply it. Again, when the demand of any one class of consumers is highest the de- mand of the other consumers will probably be low. The aggregate of these variations is called the "interweave." If it were not for this inter- weave the central station would need equipment enough to meet the simultaneous demand of the total connected load on its lines. This would require a large investment in machinery equip- ment and help, -syhich would necessarily be idle and non-productive at times. There are varia- tions in interweaves, however, for different hours of the day and different seasons of the year, and the central station must be equipped to meet the maximum demand for the inter- weave. On this account the customer with a large installed capacity connected to the linevS represents a standing expense to the station, irrespective of his use of current, and rates should be adjusted with this in mind. The customer who uses his installation a large number of hours per day is more profitable to to the central station than the customer who uses a large amount of current for only a few hours. This is due to the fact that the portion of maximum demand on the central station that may be considered as reserved for this customer is producing returns in revenue for a greater number of hours, or, stating it in other terms, the equipment reserved for this customer is idle 141 a smaller number of hours, accordingly the loss due to investment on non-productive equip- ment is lowered. The factors in rate adjusting- vary to a great extent for different classes of service, and it is difficult to use any one schedule without appar- ent discrimination, favorable or unfavorable to some one of the different classes. In general, however, the object should be to charge for the service in direct proportion to the cost of serving. Rate Schedules Flat Rates , A fixed rate per kilowatt hour. This system does hot provide a fair return to the company, neither does it encourage the profitable cus- tomer. Rate Differentials A lower rate is given for motors and battery charging than for lighting loads. This is ad- visable when these two classes of service are limited to the hours when otherwise a part of the equipment would be idle, although some classes of motor load, as elevators, etc., by their intermittent service, may seriously affect the lighting voltage. Manchester or Hopkinson System A fixed price is charged for each kilowatt of installed capacity, plus the price per kilowatt hour. The chief objection to this system is that it discourages the installation of lamps excepting where they are burned for long hours, or where they are considered a necessity. It also tends to make the cost of residential lighting unattractive. Rate Discounts A discount is given on the gross bills and also an additional discount based on the average use of the installation. The objection to this system is that the discount rate must evidently be di- vided into steps. In case of a 5% discount on a $100 bill the charge would be $95, while a bill for $98 would not be discounted, so that the first cus- tomer would get more energy for $95 than the second would get for $98. Wright or Brighton Demand System In this system the customer pays his equitable quota of the strictly fixed charges and also of the standby charges. These items are included in the charge per hour made for the first hour's use of the number of lamps equivalent to practically the maximum number of lamps used at any one time. For the energy used in ex- cess of the first hour's average use of the maxi- mum demand the customer pays a different rate proportional to the additional expense which the company is under in supplying him with ad- ditional energy, 142 Kapp System The rate is based on the time of maximum de- mand of the consumer as compared with the time of the station's maximum load. The ad- vantage of this system is that the customer, who for the same total current supplied to him contributes least to the station's maximum load, benefits most largely by discounts. Wholesale or Bulk Supply Energy is usually sold under a flat rate and at a reduced price. The reduction is due partly to the fact that a large supply can be furnished more cheaply per unit than a smaller supply. The chief reason for lowering the rate, how- ever, is that this class of business is usually com- petitive and a lower rate must be given to obtain the contract. 143 Resuscitation From Electric Shock FOLLOW THESE INSTRUCTIONS EVEN IF VICTIM APPEARS DEAD /. Immediately break the circuit. With a single quick motion, free the victim from the current. Use any dry non-conductor (clothing, rope, board) to move either the victim or the wire. Beware of using metal or any moist material. While freeing the victim from the live conductor have every effort also made to shut off the current quickly. //. Instantly attend to the victim's breathing. 1. As soon as the victim is clear of the con- ductor, rapidly feel with your finger in his mouth and throat and remove any foreign body (tobacco, false teeth, etc. ) . Then begin artificial respiration at once. Do not stop to loosen the victim's clothing now; every moment of delay is serious. Proceed as follows: (a) Lay the subject on his belly, with arms extended as straightforward as possible and with face to one side, so that nose and mouth are free for breathing. Let an assistant draw forward the subject's tongue. (b) Kneel straddling the subject's thighs and facing his head; rest the palms of your hands on the loins (on the muscles of the small of the back), with fingers spread over the lowest ribs. (c) With arms held straight, swing forward slowly so that the weight of your body is grad- ually, but not violently, brought to bear upon the subject. This act should take from two to, three seconds. Immediately swing backward so as to remove- the pressure, thus returning to the first position. (d) * Repeat deliberately twelve to fifteen times a minute the swinging forward and back- a complete respiration in four or five seconds. (e) As soon as this artificial respiration has been started, and while it is being continued, an assistant should loosen any tight clothing about the subject's neck, chest or waist. 2. Continue the artificial respiration (if neces- sary, at least an hour), without interruption, until natural breathing is restored, or until a physician arrives. If natural breathing stops after being restored, use artificial respiration again. 3. Do not give any liquid by mouth until the subject is fully conscious. ///. Send for nearest doctor as soon as accident is discovered. A poster embodying the above rules hag been published and distributed by the ELECTRICAL WORLD. INDEX A Ampere 1 Automobile Lighting 35 B Batteries Storage 118 Lead Plate 118 Edison 121 Bunsen Screen 7 C Calculation of Illumination 12 Candle-power 1 Mean Horizontal 2 Mean Spherical 2 Mean Zonular 2 Circle 136 Circular mil 2 Circular ring 137 Cleaning Mazda Lamps 63 Constants, illumination 19 Cone 137 Connections, transformers 128 Cost of light formula 74 Cube root 133 Curves, distribution 31 Cylinder 137 D Differential rate 142 Distribution curves 31 Distribution systems 93 E Edison battery 121 Electrical units 1 Ellipse 136 P Fechner's fraction 1 Fixtures 82 Flat rates 142 Flux of illumination 1 Foot candles 12 Formulae used in calculation of lamp data... 5 Frustum of a cone 137 of a pyramid 138 Glare 1 H Hopkinson System 142 Illumination 1 calculation of 12 fundamental formula 12 constants 19 Ml I Intensities recommended 23 Intrinsic brilliancy 1 K Kapp System 143 Kilowatt 2 L Lambert's Law 17 Lamps Automobile 35 Gem, advantages of 66 Miniature 35 Low voltage 35 Mazda 65 Sign 40 Street series 50 Train 38 Law of Inverse Squares 12 Lead plate battery US Leeson Disc 7 Lighting Mills 53 Sign 40 Street 50 Losses in incandescent filaments 80 Lumen 2 Lumen constant 19 Lummer Brodhun screen 7 M Manchester System 142 Mazda lamps 65 Cleaning 63 Energy losses 80 Mensuration 133 Mercury arc rectifier 101 Mill lighting 53 Miniature lamps 35 N National Electric Code 110 O Ohm 2 Ohm's Law 3 P Parallelogram 136 Photometry 6 Point by point method 13 Purkinje effect 2 Pyramid 137 R Rate schedules 142 Rectangle 136 Rectifier .mercury arc 101 Reflectors, types and styles of 28 S Schedules, rate 142 ux s Sector 136 Segment 1--7 Sign lighting... 40 Sphere 137 Spacing of units 21 Square root 133 Street lighting 50 Systems of distribution 93 T Transformers 123 Types 123 Core loss 123 Hysteresis loss 123 Foucault, Eddy current loss 123 Copper loss 123 Efficiency 123 Regulation 124 Testing 124 Connections 128 Installation 129 Operation 129 Train lighting 38 Trapezium 136 Trapezoid 136 Triangle 136 V Visual acuity 3 Volt 3 W Watt 3 Watt-hour 3 Wire data 104 Wiring Symbols 116 Wright System 142 General Electric Company >>r! iciuRl Offices, S-henectady, N. Y. ' \ ; General Sale** Office Edison Lamp Department, Harrison, N. J. SALES OFFICES (Address nearest ffice) BOSTON. MASS 84 State Street Springfield, Mass Massachusetts Mutual Building Providence, R. I Union Trust Building NEW YORK, N. Y 30 Church Street Rochester, N. Y Granite Building Syracuse, N. Y Post-Standard Building Buffalo. N. Y Ellicott Square Building Erie, Pa Marine National Bank Building New Haven, Conn Malley Building PHILADELPHIA, PA Witherspoon Building Baltimore, Md Electrical Building Charlotte, N. C Trust Building Charleston, W. Va Charleston National Bank Building Pittsburgh, Pa Oliver Building Richmond, Va Mutual Building Youngstown, Ohio Wick Building ATLANTA, GA Third National Bank Building Birmingham, Ala Brown-Marx Building New Orleans, La Maison- Blanche Building Jacksonville, Florida Florida Life Building CINCINNATI, OHIO Provident Bank Building Columbus, Ohio Columbus Savings & Trust Building Cleveland, Ohio Citizens Building Dayton, Ohio Reibold Building Toledo, Ohio Spitger Building Chattanooga, Tenn James Building Knoxville, Tenn Bank and Trust Building Memphis, Tenn Randolph Building Nashville, Tenn Stahlman Building Indianapolis, Ind Traction Terminal Building Louisville, Ky Paul Jones Building CHICAGO, ILL Monadnock Building Davenport, Iowa Security Building Keokuk, Iowa Monarch Building Detroit, Mich Majestic Building (Office of Soliciting Agent) Joplin, Mo Miners' Bank Building St. Louis. Mo Wairtwright Building Kansas City, Mo Dwight Building Butte, Montana Electric Building Minneapolis, Minn 410 Third Ave., North Milwaukee, Wis Public Service Building DENVER, COLO First National Bank Building Boise, Idaho Idaho Building Salt Lake City, Utah Newhouse Building SAN FRANCISCO, CAL Rialto Building Los Angeles, Cal 124 West Fourth Street Portland. Ore Electric Building Seattle, Wash Colman Building Spokane, Wash Paulsen Building For TEXAS and OKLAHOMA Business refer to Hobson Electric Company Dallas, Tex Lamar & Caruth Streets El Paso, Tex Chamber of Commerce Building Houston, Tex Chronicle Building Oklahoma City, Okla Insurance Building FOREIGN SALES OFFICES Schenectady, N. Y. , Foreign Dept. New York, N. Y., 30 Church St. London, . C., England, 83 Caonon St. For all CANADIAN Business refer to Canadian General Electric Co,, Ltd,, Toronto, Oat, Additional Data c| H OF CALIFORNIA LIBRARY