GIFT OF 
 Mr*. H. T. 
 
PRACTICAL DIRECTIONS 
 
 -FOR- 
 
 AND 
 
 FIELD-MAGNET WINDING. 
 
 BY EDWfllJD 
 
 AUTHOR OF 
 
 Everybody's Hand-Book of Electricity, 
 
 How to make Electric Batteries at Home, 
 Experimental Electricity, 
 
 Dynamos and Electric Motors, 
 
 Electricity and its Recent Applications, 
 
 A Practical Treatise on Electro-Plating, etc. 
 
 ILLUSTRATED. 
 
 CONTAINING WORKING DIRECTIONS 
 
 FOR WINDING DYNAMOS AND MOTORS, WITH ADDITIONAL DESCRIPTIONS OF SOME 
 
 APPARATUS MADE BY THE SEVERAL LEADING ELECTRIC COMPANIES 
 
 IN THE UNITED STATES. 
 
 Itynn, JVlass.: 
 
 BUBIEJ* PUBLtlSHH^G CO|WPflJ4Y. 
 1892. 
 
VA -T. 
 
 COPYRIGHTED BY 
 
 BUBIER PUBLISHING COMPANY. 
 1892. 
 
 Press of G. H. & W. A. Nichols, Lynn, Mass. 
 
PREFACE. 
 
 THE winding of a dynamo or motor is a matter of 
 some difficulty (as all students of Electricity have 
 discovered), hence many attempts otherwise success- 
 ful, have ended here in failure and discouragement. 
 The importance then of knowing how to wind a 
 machine properly, can be seen at once. . 
 
 The standard works on Electricity contain very 
 little practical information on this subject. The reason 
 for this lack of information probably is the fact that 
 the art of winding was to a great extent theoretical, 
 until a very recent date. At present, although not 
 absolutely perfect, electrical knowledge has reached a 
 more scientific basis. By following certain rules, one 
 may wind a machine to obtain almost any result 
 desired. 
 
 In this treatise theories have not been deeply 
 entered into, the information being more of a practical 
 character. It is thus adapted to the use of beginners 
 and to the more advanced student. Illustrations have 
 been used wherever necessary to make the text clear 
 to the mind of the reader. 
 
 EDWARD TREVERT. 
 
 LYNN, MASS., Feb. 10, 1892. 
 
 46450? 
 
CONTENTS. 
 
 INTRODUCTION. 
 
 CHAPTER i. The Armature in Theory. 
 
 CHAPTER 2. Forms of Armatures. 
 
 CHAPTER 3. Drum Winding. 
 
 CHAPTER 4. Field Winding. 
 
 CHAPTER 5. Field Formulae. 
 
 CHAPTER 6. General Methods of Winding. 
 
 CHAPTER 7. Field Winding concluded. 
 
 CHAPTER 8. Dynamos. 
 
 CHAPTER 9. Motors. 
 
Armature and Field-Magnet Winding, 
 
 INTRODUCTION. 
 
 ALL magnets are surrounded by what is known 
 as a field of force. The familiar experiments with 
 the magnet and iron filings give us some notion of 
 the character of this field, for the filings always 
 adjust themselves along certain lines, generally 
 curves, depending for their shape upon the form of 
 the magnet. 
 
 The region surrounding the magnet is conceived 
 as being penetrated by " lines of force," which 
 radiate from the poles and are parallel to the lines 
 of iron filings. They emerge from the magnet 
 something like the bristles of a brush, and always 
 form closed curves, that is, they always return by 
 longer or shorter routes to the body of the magnet 
 and through it to the starting point. It is for this 
 reason that it is impossible to make a unipolar 
 magnet. Every magnet must have two poles, a 
 north and south. 
 
 These lines do not pass with equal facility 
 through all substances. Most bodies offer a high 
 
resistance to them, but iron, steel, nickel, and one 
 or two others to a less degree, are good "magnetic 
 conductors." Magnetism always follows the path 
 of least resistance, and with a given magnetizing 
 force the intensity of the resulting magnetism is 
 enormously increased by the presence of iron. It 
 is for this reason that we use iron in the fields of 
 our dynamos and motors and we shall see later 
 that it is of the highest importance that the 
 " magnetic circuit" or path over which the mag- 
 netic force passes should have a large cross section 
 and a low resistance. 
 
 Whenever a conductor of electricity is passed 
 through the field of force surrounding a magnet, at 
 right angles to the lines, an electromotive force is 
 set up in it, depending upon the length of the 
 conductor, the speed at which it moves, and the 
 intensity of the field. This fact is the one utilized 
 in the construction of dynamos, and forms the 
 basis of our calculations, for, knowing the strength 
 of the field magnets, the length of the wire on the 
 armature, and the speed at which it revolves, we 
 have all the data necessary to calculate our electro- 
 motive force. 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 CHAPTER I. 
 
 THE ARMATURE IN THEORY. 
 
 IN making our calculations we designate the 
 strength of the field by the "number of lines of 
 force " for a given sectional area. In speaking of 
 lines of force the reader must not be led into the 
 idea that these lines have any real existence. 
 They simply form a convenient symbol for a state 
 of affairs which nobody understands very clearly 
 at present, but which must be dealt with in some 
 manner in this kind of work. If we take a con- 
 ductor and move it so as to cut across the field of 
 force at right angles to it, we get an electromotive 
 force proportional to the speed of the conductor 
 and the number of lines of force it cuts, or 
 
 s=s-i 
 
 Where E= the E. M. F., 5= the speed, and / 
 the number of lines of force. 
 
 Suppose this conductor is on the periphery of 
 an armature, /the total number of lines of force 
 passing through the armature from one pole to the 
 other and n the number of revolutions of the 
 armature per minute. Then it can easily be shown 
 
10 ARMATUKE AND FIELD-MAGNET WINDING. 
 
 that the average E. M. F. generated in this con- 
 ductor during a revolution is 
 
 E=2/ 
 
 60 
 
 To get the E. M. F. for a coil of wire instead of 
 a single conductor we multiply the second term of 
 our formula by the number of wires in this coil 
 upon the external surface of the armature and 
 calling / this number we would have 
 
 E=2lt 
 
 4 / would of course be equal to the number of 
 times in a Gramme ring coil and double the number 
 of times in a drum armature coil. Then suppose 
 we have a number of coils in series. The E. M. 
 F. for the whole of them would clearly be this 
 number multiplied into the second term of the 
 above and letting N stand for this number of coils 
 we get 
 
 E=2ltN 
 
 As closed coil armatures are ordinarily con- 
 nected, they have half the wire on them in series 
 and the two halves in parallel, so that the E. M. F. 
 they produce is one-half that which would be given 
 if the entire number of external wires (= N t) were 
 in series. Consequently, if we take Nt in such a 
 case to represent the entire number of external 
 wires, we should get for the E. M. F. 
 
ARMATUKE AND FIELD-MAGNET WINDING. 
 
 11 
 
 The simplest form of armature is the shuttle 
 armature, devised by Siemens. It consists of a 
 single coil of wire wound lengthwise upon an iron 
 " shuttle." (See Fig. 2, 3, 4, 5.) 
 
 When this is revolved between the poles of a 
 magnet a current is set up in the wire, the direc- 
 
 FlG. I. 
 
 tion of which may be determined by the following 
 "rule of thumb." Spread out the thumb and first 
 two fingers of the right hand in such a way that 
 each will be at right angles to the other two. (See 
 Fig. i.) 
 
12 ARMATURE AND FIELD-MAGNET WINDING. 
 
 FlG. 2. 
 
 FIG. 3. 
 
 FIG. 4, 
 
 FIG. 5. 
 
ABMATUKE AND FIELD-MAGNET WINDING. 
 
 13 
 
 Then if the thumb be pointed in the direction 
 of motion of the wire, and the forefinger in the 
 direction of the lines of force (that is, from the 
 north to the south pole of the magnet), the middle 
 finger will be pointing in the direction of the cur- 
 rent. 
 
 It will be seen that by applying this rule to the 
 coil just spoken of we find that the current in the 
 
 FIG. 6. 
 
 wire will reverse at each half revolution, and that 
 if we desire the current in the external circuit to 
 be in one direction we must place what is known 
 as a commutator at the point where the current is 
 led from the armature. The commutator in this 
 
14 ARMATURE AND FIELD-MAGNET WINDING. 
 
 case will consist of two halves of a metallic cylin- 
 der attached to the armature shaft but insulated 
 from it and each other. The ends of the coil are 
 fastened one to each half of the cylinder and the 
 brushes or collectors which lead off the current 
 rub against them. (See Fig. 6.) 
 
 Then when the armature is in the position 
 shown, the current in the external circuit will flow 
 as indicated by the arrow, and when the armature 
 has made half a complete revolution its current 
 will be reversed, but at the same time its connec- 
 tion with the external circuit is reversed by the 
 commutator, and the current still flows there in 
 the same way. 
 
 When the armature has made a quarter revolu- 
 tion or stands at right angles to its present posi- 
 tion, the brushes will touch both segments of the 
 commutator, and the coil is short circuited, but at 
 the same time it will be seen that the wires of the 
 coil are not moving across the lines of force, but 
 parallel to them, and that they are therefore genera- 
 ting no E. M. F., so there is no harm done, that is, 
 there would be none if the above statements were 
 accurately true. Practically if the coil has any 
 breadth it cannot be moving parallel to the lines 
 of force at every point at the same instant, and a 
 sufficient current may be generated during this 
 period to cause a spark to form when the short cir- 
 cuit, caused by the brushes passing from one 
 
ARMATURE AND FIELD-MAGNET WINDING. 15 
 
 segment to the next, is broken. In well designed 
 machines, this can be avoided by attention to the 
 shape of the pole pieces of the fields, that is by so 
 making them that few, if any, lines of force are 
 cut by the coils when short-circuited. 
 
 The current given by the above arrangement 
 while it flows in but one direction is nevertheless 
 an intermittent one, varying from its maximum, 
 
 FIG. 7. 
 
 when the coil is horizontal to nothing, when it is 
 vertical and short-circuited. If we wind another 
 coil on the armature with its plane at right angles 
 to the first, we shall evidently lessen this tendency, 
 for when one coil is in its idle position, the other 
 will be doing its best work and vice versa, but 
 
16 ARMATURE AND FIELD-MAGNET WINDING. 
 
 there would still be a jog in the current strength, 
 though to a much smaller degree. 
 
 Three coils would evidently be a step further in 
 the right direction, and in fact, the greater the 
 number of coils we use, and of course the greater 
 the number of commutator segments, the nearer 
 we come to having a smooth current. The num- 
 ber is limited by the difficulty of construction 
 which increases with each additional commutator 
 segment. 
 
 In the usual construction of the closed coil 
 armatures the end of one coil is connected to the 
 beginning of its next neighbor, and a wire is taken 
 from this junction to a commutator bar, and there 
 must therefore be as many commutator segments 
 as coils. This arrangement is best shown on a 
 Gramme ring, but the principle is the same for 
 any style of armature. (See Fig. 7.) 
 
 In the sketch showing this arrangement it is 
 seen that the current in the armature is flowing in 
 the opposite direction in the two halves made by 
 the line A B. In each case, it flows from B to A, 
 and therefore if brushes be placed against the com- 
 mutator on the line A B they will be in the proper 
 position to take the current. In an open coil arma- 
 ture, that is, one in which each coil is by itself and 
 has no connection with the others, the brushes 
 must be on a line at right angles to A B, or so 
 that they can take off the current when the coil is 
 generating the highest E. M. F. 
 
AKMATURE AND FIELD-MAGNET WINDING. 17 
 
 CHAPTER II. 
 
 FORMS OF ARMATURES. 
 
 THE two forms of armature most commonly met 
 with in practice are the Gramme ring and drum. 
 Each has its special advantages, and in choosing 
 either we must be guided largely by the conditions 
 governing the construction and running of a ma- 
 chine. 
 
 The Gramme ring armature consists of a ring or 
 hollow cylinder of iron, upon which the wire is 
 wound. Instead of going completely around the 
 outside of the armature, each turn of wire goes 
 through the opening in the middle and thence 
 back to the outer surface again. On an armature 
 of this description each coil is wound by itself and 
 is not overlapped by any of the others, conse- 
 quently if repairs are necessary at any time it is 
 easy to get at the particular coil where the fault 
 is without disturbing the others, and this is often 
 an important point where the armature is wound 
 with a large number of .turns of fine wire. The 
 coils being each one open to the air makes it bet- 
 ter, too, for getting rid of the heat generated in 
 
18 ARMATURE AND FIELD-MAGNET WINDING. 
 
 wire and core. On the other hand the wire which 
 passes through the middle of the armature is 
 "dead" so far as exciting E. M. F. is concerned 
 and it not only does not help but adds a wasteful 
 resistance. 
 
 Then a ring armature is much more difficult to 
 wind, as the wire must be passed through the 
 middle for each turn. The cross section of the 
 armature core is also necessarily smaller than 
 for a drum armature of the same dimensions 
 and therefore its magnetic resistance is greater. 
 In a general way we may say that the ring arma- 
 ture is better adapted for machines giving constant 
 current and high potential and that the drum 
 armatures are the proper ones to use for constant 
 potentials and large currents. The core of the 
 ring armature is made in several ways. It 
 should never.be a solid piece on account of the 
 eddy currents which would be generated in it, and 
 cause it to heat. It might be made of a flat ribbon 
 of sheet iron wound up to make a cylinder, but 
 this would have, to a smaller degree, the same 
 objection as the solid core. It is frequently made 
 of iron wire wound in a former of wood and shel- 
 laced and bound with tape to make it keep its 
 shape. This method has many advantages; it is 
 cheaply and easily done and gives good results and 
 unless one has special facilities for doing the work 
 is probably the best. 
 
ARMATURE AND FIELD-MAGNET WINDING. 19 
 
 A core of this sort, however, is slightly inferior 
 considered as a magnetic conductor to one made 
 of disks or flat rings of sheet iron. Magnetism 
 always shows a preference for running along the 
 grain of the iron, and it would have more difficulty 
 in getting out of the centre of a core made of wire 
 where it would have to go at right angles to the 
 grain and besides have numerous air gaps to leap 
 across than it would to get out of a similar core 
 made up of disks. (See Fig. 8.) 
 
 FIG. 8. 
 
 If a core made of rings cut from sheet iron is 
 used, some means must be used to hold them to- 
 gether. This may be done by a bolt or screw 
 through them from end to end, or they may be 
 held by the " spider" by which they are attached 
 to the armature shaft. (See Fig. 9.) 
 
20 
 
 ARMATUKE AND FIELD-MAGNET WINDING. 
 
 There is no need of paper or any other insula- 
 tion between the disks. The black oxide of iron 
 on the surface is sufficient, the danger from heat- 
 ing not being so much from the small currents in 
 the disks jumping across from one to the other, as 
 from the lines of magnetic force going through 
 the armature slantingly. One prominent inventor 
 even goes so far as not only to discard the paper 
 insulation but to replace it at intervals with disks of 
 zinc, and claims that his armatures run much cooler. 
 
 FIG. Q. 
 
 Another point which should be brought out in 
 this connection is that the armature core should 
 be the same length that the pole pieces are wide, 
 in order that the lines of force as stated above may 
 go straight from one pole to the other. 
 
 In regard to the necessity for some means of 
 holding the armature coils in place there is a 
 diversity of opinion. Some builders wind their 
 
AKMATUKE AND FIELD-MAGNET WINDING. 
 
 21 
 
 coils upon a smooth core and trust to friction and 
 good luck to hold them where they are placed. 
 The author, however, believes that there is no use 
 in taking needless risks in a matter of this sort 
 where slight additional precaution may be the 
 saving of an expensive piece of repairing. The 
 necessity is perhaps not so great in the case of 
 the Gramme ring as the drum armature, but there 
 is no harm in using it in either case. 
 
 FIG. 10. 
 
 The strain on these coils is of course the resist- 
 ance against which the armature must be turned 
 and the effect is very much the same as if a brake 
 were applied to the surface of the armature to pre- 
 vent its rotation. The method generally em- 
 ployed to prevent the coils from slipping is to bore 
 
22 ARMATURE AND FIELD-MAGNET WINDING. 
 
 holes in the external surface of the armature close 
 to the ends between the coils, and drive pegs 
 either of wood or iron into them ; if the latter they 
 must of course be carefully insulated. (See Fig. 10.) 
 Sometimes the ends are sawed across and 
 
 FIG. ii. 
 
 wedges of hard wood driven in, as in Figure 
 
 11, and sometimes these wooden wedges extend 
 the whole length of the armature, as in Figure 
 
 12. Perhaps the best, but at the same time 
 
 FIG. 12. 
 
 most expensive way, is to make the disks which 
 form the core of the armature like a toothed wheel. 
 (See Fig. 13.) 
 
 When these are put together to form the core 
 
ARMATURE AND FIELD-MAGNET WINDING. 23 
 
 the projections will make ribs, running the length 
 of the armature, between which are channels in 
 which the wire may be wound. This not only 
 gives a solid construction, but also has the advan- 
 tage of reducing the magnetic resistance of the air 
 space. The core of the armature must always be 
 carefully insulated by two or three layers of wrap- 
 ping paper stuck on with shellac. On larger arma- 
 tures a layer of canvas is advisable between the 
 papers to lessen the liability to breaking through 
 on corners and sharp edges. 
 
 FIG. 13. 
 
 The winding of a Gramme ring is not a very 
 easy thing to do, since the wire must be passed 
 through the centre of the armature for every turn 
 on the coil. You may either do this with as large 
 a bundle of wire as you can get through the open- 
 ing, and run the risk of its tangling, or use shorter 
 pieces and make a number of joints. 
 
24 ARMATUKE AND FIELD-MAGNET WINDING. 
 
 Decide upon how many coils you are going to 
 have, and lay out the ends of the armature in this 
 number of divisions. If you are going to use pegs 
 to hold your coils in place, put them in at these 
 division marks and they will serve as guides for 
 winding. You should certainly have something 
 to guide you, so if you do not have the pegs, clamp 
 on two strips of wood the length of the armature 
 core and as far apart as your coil is to be wide. 
 Then when it is wound remove them and proceed 
 "in the same way for the next coil. Begin at any 
 one of the divisions to wind. It does not matter 
 which way you wind so long as you follow the 
 same direction in each coil. Leave a few inches 
 of your starting wire hanging loose. Shellac every 
 layer when you have completed it, and when you 
 have the required depth of wire, do not cut it 
 off but throw out a loop, and continue winding 
 with the same wire and in the same direction on 
 the next coil. Of course these loops must all be 
 at the same end of the armature, viz., at the com- 
 mutator end. 
 
 Continue winding and throwing out loops be- 
 tween each coil until you have occupied all the 
 spaces, and when you have finished the last coil 
 leave a few inches of wire hanging free, and twist 
 it together with the starting wire of the first coil. 
 If the coils come close together on the inside of 
 the armature, and if they are in danger of touch- 
 ing they should be insulated carefully. 
 
AKMAT17KK AND FIELD-MAGNET WINDING. 25 
 
 Joints in the wire should always be soldered. 
 If the wire is small the ends can be compactly 
 twisted together, and the place where this is done 
 should be where the increased thickness will not 
 make a lump in the winding which will be un- 
 sightly or in danger of touching the pole pieces. 
 
 FIG. 14. 
 
 Large wires are not so likely to need joining 
 since the coils made by them are generally short, 
 and you can usually arrange it so that the break 
 will come between two coils. Should it be neces- 
 sary, however, to make a junction in a coil, and 
 
26 
 
 ARMATURE AND FIELD-MAGNET WINDING. 
 
 the wire is large enough to make a large swell if 
 twisted together, bevel off the two ends and bind 
 them together with fine wire and solder, being 
 careful to get the wire hot enough to cause the 
 solder to penetrate everywhere. (See Fig. 15.) 
 
 Sometimes a sleeve of thin copper is made, into 
 which the ends may be slipped and soldered, but 
 the author prefers the binding wire method as 
 being the surest. 
 
 FIG. 15. 
 
 The joint must be wrapped in white tape, after 
 having been washed in alcohol to remove the sol- 
 dering acid which would in time destroy the insu- 
 lation. After the armature is wound it should 
 be put into a drying oven of some sort to dry it 
 out, for the shellac when wet makes a very noticea- 
 ble reduction in the resistance of the armature. 
 An oven heated by steam is the safest, as it pre- 
 vents the armature from getting hot enough to 
 
ARMATURE AND FIELD-MAGNET WINDING. 27 
 
 burn or char the insulation. The time it is to 
 remain in the oven will depend of course upon the 
 size of the armature, and the thickness of the 
 wire upon it, and will vary from two to twelve 
 hours. The armature is attached to the shaft in 
 various ways. In the larger machines it is gener- 
 ally done by means of a spider, as referred to 
 above in speaking of the core. This is a hub with 
 three or four spokes reaching out and holding the 
 core by means of channels or key-ways cut in the 
 inside of the core to receive the spokes. In small 
 machines it will often be sufficient to drive wooden 
 cones into each end of the opening in the arma- 
 ture and pass the shaft through them. Suitable 
 precautions must be taken to prevent the cones 
 from abrading the insulation on the wires they 
 touch, by protecting them with canvas. The shaft 
 must be in the exact centre of the armature, 
 since it must run as closely as possible to the pole 
 pieces. 
 
 The last operation to the armature itself is to 
 put on the binding wire. This is to prevent the 
 wires from flying out when run at a high speed. 
 The number of bands you put on will depend upon 
 the length of the armature, a small one needing 
 only one, and a large one three or four. Wrap a 
 strip of shellaced paper and canvas around the 
 armature where you have decided to put your bind- 
 ing wires, and then using fine brass wire, wind on 
 
28 ARMATURE AND FIELD-MAGNET WINDING. 
 
 a number of turns, till you have a band from 
 3^ to y? an inch wide. Wind it on tightly, and at 
 intervals solder the whole width of the band to- 
 gether. 
 
 The connections to the commutator should be 
 made either by screws or solder, but perhaps best 
 by both. In some cases it is thought that it is 
 better not to connect the wires directly to the 
 commutator bars, but to solder them to flat strips, 
 which may be bent around the wires to make a 
 better connection, and then screw and solder these 
 strips to the commutator bars, their shape allow- 
 ing them to make a better contact than the round 
 wires. 
 
 Understand each loop, that is to say, the begin- 
 ning of one coil and the ending of the adjacent one 
 is to be connected to a bar by itself. When the 
 connections are all made, and the armature is in 
 shape for running, it must be balanced. This is 
 done by placing the two ends of the shaft upon a 
 couple of straight edges, which have previously 
 been carefully levelled. 
 
 The armature will usually come to rest in some 
 particular position, which shows that the top side 
 needs more weight. If it is badly out of balance, 
 some pieces of lead should be wedged under the 
 binding band, but if only a little off, add a little 
 solder to the binding wire on the light side, until 
 the armature will stay in any position you put it. 
 
ARMATURE AND FIELD-MAGNET WINDING. 29 
 
 Before leaving the Gramme ring armature we will 
 speak of armatures for four pole machines, which 
 are or may be slightly different from the ordinary 
 two pole armature. (See Figs. 16 and 17.) The 
 connection between the winding and the com- 
 mutator may be the same as for the two pole 
 machine, in which case four brushes will be 
 necessary as in the first sketch. The brushes 
 nearest each other will have the opposite sign 
 (-[- or ) and consequently those diametric- 
 ally opposite will have the same sign. Two op- 
 posite brushes, then, must be connected together 
 for one pole of the machine, and the other two for 
 the other pole. It is not necessary to use four 
 brushes, however, if the connections are made as 
 shown in Figure 17. Here the opposite seg- 
 ments of the commutator or the wires leading 
 to them are connected, which amounts to the same 
 thing as connecting the opposite brushes. 
 
 Another point should be spoken of here, although 
 it applies equally to the drum armature, and that is 
 the open coil connections. In this armature there 
 are twice as many commutator segments as coils, 
 and the ends of each coil instead of being con- 
 nected to neighboring segments, are connected to 
 the diametrically opposite segments and only one 
 end to each segment. There is then no connection 
 between the different segments. 
 
 A rather novel form of Gramme ring machine, 
 
30 AliMATUKE AND FIELD-MAGNET WINDING. 
 
 FIG. 1 6. 
 
ATCMATUltE AND FIELD-MAGNET WINDING. 81 
 
 which is perhaps better adapted for use as a 
 motor than a dynamo will be described while we 
 are still on the subject of ring armatures. The 
 armature is of the ordinary ring pattern, preferably 
 with projecting lugs on the inside between the coils. 
 
 FIG. 18. 
 
 The field instead of being around the armature is 
 inside it, and is simply a shuttle-wound armature 
 supplied with a current in one direction only. 
 This gives a very short magnetic circuit and con- 
 sequently requires but little magnetizing power. 
 (See Fig. 18.) 
 
32 ARMATUKE AND FIELD-MAGNET WINDING. 
 
 CHAPTER III. 
 
 DRUM WINDING. 
 
 THE drum armature is as stated in the previous 
 chapter, better adapted for low potentials than 
 the ring armature. It has a greater capacity for 
 large currents than the lines of magnetic force, 
 which means a stronger field. 
 
 Formerly the practice was to place a number 
 of layers of wire on the armature to obtain the 
 necessary E. M. F., but while this custom exists 
 still in the ring armatures, the tendency in the case 
 of drum armatures has been to reduce the number 
 of layers as much as possible, and to make up for 
 the loss of potential caused by the fewer turns by 
 strengthening the field and increasing the speed, 
 or the diameter of the armature. The reason for 
 this is that people are beginning now to see 
 the importance of reducing the resistance of 
 the magnetic circuit to its lowest limit. The 
 gain affected by leaving off one layer of wire, 
 and diminishing the air space between the core and 
 pole pieces by that amount, is astonishing to one 
 who has never seen it tried. 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 It is even stated that the pole pieces should fit 
 the armature winding so closely, that they have to 
 be bored out in shallow grooves where the bands 
 of binding wire come, and persons who have tried 
 this, claim that the benefit resulting from it is 
 much in excess of the slight additional work it 
 makes. 
 
 We cannot impress the fact too forcibly upon 
 our readers, then, that they should make every 
 effort to keep down this magnetic resistance. 
 Builders generally nowadays are trying to get along 
 with a single layer of wire on the armature. Wind- 
 ing two layers has other disadvantages. It makes 
 it worse about getting at a fault to repair it, and 
 does not allow such good ventilation. When two 
 layers are wound on, it usually means that one-half 
 of the armature winding is in the first layer, and 
 the other half in the second, and that the second 
 having a greater length of wire has a greater resist- 
 ance which throws the armature out of electrical 
 balance, causing sparking and other evils. 
 
 Various ingenious devices have been used by in- 
 ventors to overcome this last difficulty, by winding 
 with double wires, so that the outside and inside 
 layers may have equal shares of each coil, but they 
 are at best make shifts and greatly increase the 
 trouble of construction, and we should advise in all 
 cases when the necessary potential cannot be se- 
 cured, except by a large number of turns, that a 
 Gramme armature be used. 
 
34 ARMATUKE AND FIELD-MAGNET WINDING. 
 
 The drum winding is not essentially different 
 from the ring, except of course that the wires go 
 completely around the length of the armature in 
 place of passing through its center. The same 
 remarks apply to lamination of the core, and to the 
 pegs for keeping the wire in place. The disks can 
 be held in place on the shaft by washers which can 
 be screwed against them along the shaft from either 
 end. (See Fig. 19.) 
 
 " FIG. 19. 
 
 In laying out the spaces on the core to be occu- 
 pied by the coils, you must have double the num- 
 ber of spaces that you have coils, if you intend to 
 have only a single layer of wire, for each coil occu- 
 pies two spaces, one at each end of a diameter of 
 the core. If you have two layers of wire and wind 
 one-half of your wire in the first, and the other 
 half in the second layer, you will only need the 
 
ARMATURE AND FIELD-MAGNET WINDING. 35 
 
 same number of spaces as coils. This is a point 
 that sometimes puzzles young amateurs. They 
 have only the same number of spaces as coils and 
 find to their surprise when they have filled all the 
 spaces that they have only commutator connec- 
 tions for half of the commutator bars. 
 
 When you are winding on two layers of wire 
 you start as you did in winding the Gramme ring, by 
 leaving a loose end hanging, and then winding along 
 the length of the armature and into the spaces 
 diametrically opposite When you have filled one 
 space leave a loop hanging, and go on and wind up 
 the next in the same way. When you have half 
 your coils wound, you will find, as stated above, 
 that all the spaces are occupied. Shellac the wind- 
 ing well and cover it over with a strip of cloth. 
 The wires of the different coils will cross at the 
 ends of the armature. These points of intersec- 
 tion must always be covered by a piece of cloth be- 
 fore the next coil goes on. 
 
 Wind the second half of the armature over the 
 top of the first one and connect the last end with 
 the starting wire of the first layer. When wind- 
 ing, as in this case, into diametrically opposite 
 spaces, you will find that the armature shaft inter- 
 feres with the wire going straight across the end 
 and you will have to go around it, one-half the coil 
 on one side and one-half on the other. The 
 armature shaft at this point must be insulated as 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 thoroughly as the core itself. When winding on 
 only one layer, we proceed in a slightly different 
 manner. 
 
 Suppose, for example, that we have a four-coil 
 armature. Then beginning at one of the spaces, 
 wind, not into the diametrically opposite one but 
 into its neighbor. 
 
 H 
 
 FIG. 20. 
 
 Beginning at a, wind the coil 1-2, and throw 
 out a loop, and skipping space b, wind coil 
 3-4. Throw out a loop again and skipping d, wind 
 56, and lastly skipping f y wind 7-8, and join the 
 two ends, and connect to the commutator as 
 shown. This method is to be followed for any 
 number of coils. We simply wind into an adja- 
 cent space to the one diametrically opposite the 
 
ARMATUKE AND FIELD-MAGNET WINDING. 37 
 
 starting space, and then skip a space in starting 
 the next one. (See Fig. 20.) 
 
 The remarks about finishing up the ring arma- 
 ture all apply equally to the drum armature. 
 
 We will now take up the theoretical armature 
 and the methods of making our calculations. The 
 formula given above, for the E. M. F. of the arma- 
 ture is 
 
 E=l t N ^ 
 
 This expression if the lines of force / are given 
 in absolute units would give the E. M. F. in abso- 
 lute units. The absolute unit is TOOO^OO^TT of the 
 practical unit or volt, so we must divide the result 
 above by 100000000 to get it into volts or what 
 means the same thing, multiply it by io" 8 . 
 
 If we adopt the Kapp notation and make our 
 unit of field strength 6,000 times as large as the 
 absolute unit, and call the strength of field as 
 expressed by this new unit Z, we should have for 
 the relation between Z and / 
 l=6ooo Z. 
 
 Z and / are the number of lines of force,, 
 which, for a given field will vary inversely as the 
 size of the unit. If we use this new unit we must 
 divide the result by 1,000,000 instead of 100,000,000 
 to get E in volts and will have 
 
 ZtNn -7 f M n irT 8 
 
 Toooooo ^ t IN n IO 
 
 If we let m equal the number of lines of force per 
 square inch of section of armature core and a be 
 
38 ARMATURE AND FIELD-MAGNET WINDING. 
 
 the length of the core and b equal its thickness 
 then 2 abm will equal the number of lines of 
 force passing through the core in the case of the 
 Gramme ring and abm in the case of the drum 
 armature. (See Fig. 21.) 
 
 FIG. 21. 
 
 M according to Kapp reaches its maximum when 
 it equals 30, and the iron is then said to be satu- 
 rated ; 20, according to the same authority is a 
 fair average value for good modern dynamos and 
 motors. 
 
ARMATUHE AND FIEI.D-MAGXET WINDING. 39 
 
 CHAPTER IV. 
 
 FIELD WINDING. 
 
 THE magnetic field in which the armature re- 
 volves may be produced by permanent or electro- 
 magnets. The first method makes a bulky machine 
 for the hardened steel, of which such magnets are 
 made is an inferior conductor of magnetic force 
 to wrought or cast iron. It has given away in ma- 
 chines meant to supply any considerable current, 
 to the electro-magnetic field, but is still used on the 
 "magnetos" for ringing bells and for therapeutical 
 purposes. In such cases it is customary to use a 
 shuttle armature with fine wire winding and no 
 commutator. 
 
 It is stated that permanent magnets are much 
 better adapted for dynamos than motors, as in the 
 former case they tend to become stronger and in 
 the latter weaker through use. In every case how- 
 ever where the machine is of any size, and space and 
 weight an object, the iron fields are vastly superior 
 since a given weight of iron will give a much 
 stronger field than an equal weight of hardened 
 steel, of the same shape. 
 
40 ARMATURE AND FIELD-MAGNET WINDING. 
 
 The magnetic qualities of the iron are conferred 
 upon it by a winding of insulated wire through 
 which a current is passing. Theoretically there 
 should be no difference in the magnetic force pro- 
 duced by a given coil of wire and current, no mat- 
 ter at what point of the magnet's length it is placed. 
 And really there is not, but there seems to be a 
 general idea among dynamo constructors, that 
 coils put upon the poles or close to them, prevent 
 the lines of force from straying around in some 
 other way than through the armature where they 
 will do some useful work. It is mainly -for this 
 reason that we see the series coils of so many 
 dynamos placed upon the poles. There are also 
 the advantages of greater accessibility for repairs, 
 and less damage from over heating. 
 
 In winding a magnet it makes no difference so 
 far as the magnetic effect is concerned, whether 
 there are 100 turns of wire with I ampere flowing 
 through them, or I turn with 100 amperes. The 
 product of the number of turns by the amperes is 
 called the "ampere-turns." 
 
 The fields of different dynamos may be wound 
 very differently but have the same strength. The 
 fields of a shunt wound dynamo get their current 
 at a constant potential, and as it is desirable to use 
 as little power as possible on them, the winding is 
 made of fine wire to give a high resistance, and 
 the small amount of current is made up for by 
 the larger number of turns. 
 
ARMATURE AND FIELD-MAGNET WINDING. 41 
 
 In a series wound dynamo there is usually a cer- 
 tain amount of current available, and it is taken 
 around the fields on large wire, and with as few 
 turns as possible. The character of the winding 
 will depend therefore upon the conditions under 
 which the dynamo is to run. 
 
42 ARMATURE AND FIELD-MAGNET WINDING. 
 
 CHAPTER V. 
 
 FIELD FO RMUL AE . 
 
 THE calculations for the strength of the field, 
 and the necessary current to produce it, are based 
 upon the assumption that the lines of magnetic 
 force obey a similar law to that for electric current, 
 viz. ; that they vary directly as the magnetizing force 
 and inversely as the resistance of the circuit. 
 Kapp has made this a subject of investigation and 
 finds a formula which fits approximately to 
 observed facts. This is given below : 
 
 P_ 
 
 Z 1 440*1+ i + ^ 
 
 h cb ' ab ' AB 
 
 and 
 0.8 P 
 
 _-. 
 
 ' ab ' AB 
 
 Where Z= the total number of lines of force, 
 P the exciting power in ampere-turns, a b the cross 
 section of the armature (Gramme ring in this case), 
 c the arc spanned by each pole piece, d the distance 
 between the polar surface of the magnets and the 
 external surface of the armature core, 1 the average 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 43 
 
 length of the magnetic circuit inside the armature, 
 L the length of the magnetic circuit in the field 
 magnets, and A B the cross sectional area of their 
 core. See Fig. 22. 
 
 As the lengths are all given in inches, the excit- 
 ing power in ampere-turns, and the result Z in the 
 same units chosen in the armature formula viz. : 6000 
 times larger than the absolute unit, so that the 
 
 FIG. 22. 
 
 results obtained by this formula may be readily 
 applied to the armature calculations. 
 
 The first of the two formulae is for well an- 
 nealed wrought iron, and a wrought iron armature 
 core, the second is for cast iron magnets. The 
 formulae only apply where the degree of magne- 
 
44 
 
 ARMATURE AND FIELD-MAGNET WINDING. 
 
 tization of the field core is not higher than 10 lines 
 per square inch, and there give pretty fair results. 
 Higher degrees of magnetization demand more 
 current than the formulae call for, and when the 
 saturation point is approached, the increased power 
 necessary over that given in the formulae is from 
 40 to 100 ft. 
 
 Different specimens of iron will sometimes vary 
 in their magnetic qualities, to such an extent that 
 
 FIG. 23. 
 
 a formula will often not serve a much better pur- 
 pose than a foundation upon which to base a good 
 guess. The formulae of Kapp however are about 
 the best that have been brought out as yet, and are 
 near enough to the truth to enable one to build a 
 dynamo, and not come very far from the calculated 
 output. By multiplying the Z by the denomi- 
 nator of the fraction in the second term we get 
 the value of P or the ampere-turns which we 
 
ARMATURE AND FIELD-MAGNET WINDING. 45 
 
 must use upon our magnets. The formulae where 
 double magnetos are used, are 
 
 for wrought iron and for cast iron 
 Z_ 0.8 P 
 
 2 
 
 The double field magnet can be made lighter 
 than the single one for the same power, but re- 
 quires more copper. Where expense is an item 
 to be considered it must give way to the single 
 magnet, but where weight is the chief point, it is 
 to be preferred. (See Fig. 23.) 
 
46 ARMATUBE AND FIELD-MAGNET WINDING. 
 
 CHAPTER VI. 
 
 GENERAL METHODS OF* WINDING. 
 
 AN experimental method of determining the 
 winding will next be considered. This is not only 
 useful in itself but can be applied advantageously 
 as a check upon the calculations described in the 
 previous chapter. 
 
 The armature is supposed to be wound, and the 
 field cores ready to receive their wire. Put the 
 armature in place and start it to revolving at the 
 speed you desire it to have. Put a few turns of 
 large wire around the field cores and pass a current 
 over them from some independent source. Take 
 the current off your armature through some adjust- 
 able resistance a bank of incandescent lamps makes 
 a good one where it can be had and a water resistance 
 is also good. This is made by putting two metallic 
 electrodes in a vessel of water and arranging them 
 so that the distance between them can be altered. 
 A resistance varying from a high to a low limit 
 can be had by using pure water, and adding a drop 
 or two of sulphuric acid per gallon. Pure water 
 will give a high resistance and the acid lowers it. 
 
AKMATUKE AND FIELD-MAGNET WINDING. 47 
 
 The finer adjustment is made, after you have 
 about what you want in this way, by altering 
 the distance apart of the electrodes. Iron tel- 
 egraph wire also makes a good resistance, coiled 
 up in springs, or wound around a wooden frame. 
 Vary this resistance and the current around your 
 fields until you get the required current and E. M. 
 F. from your armature. Then note the current in 
 the wire around your fields, and the number of 
 turns and you have the ampere turns necessary to 
 give the required strength of field. 
 
 As explained above, it makes no difference how 
 these ampere turns are put on, so that only a few 
 turns of wire are necessary for the experiment, 
 providing you have sufficient current. 
 
 Then comes the question as to what size wire to 
 use on the fields. In a series wound machine this 
 is simply a question as to what size wire will carry 
 the current without overheating, for your amperes 
 are already decided by the current that comes from 
 the armature, and you have simply to divide the 
 ampere turns as determined above by this, to get 
 the number of turns. 
 
 In the case of a shunt wound machine it is dif- 
 ferent. Here you have a certain E. M. F. avail- 
 able and you must adjust your field winding so 
 that it will produce the requisite number ampere 
 turns. 
 
 Here comes in a little point upon which good 
 
48 ARMATURE AND FIELD-MAGNET WINDING. 
 
 men trip up, and which the author has never seen 
 mentioned in text books. It does not make 
 any difference, once the size of wire on the 
 fields is chosen, how many turns you put on if 
 your dynamo or motor is shunt wound. For ex- 
 ample, suppose you have ten turns of wire of such 
 a size that with the given E. M. F. of the machine 
 it will allow fifteen amperes to flow over it. This 
 will, of course, mean 150 ampere turns on the 
 magnet. Suppose, with the E. M. F. unchanged, 
 you increase the number of turns to 20. This will 
 double the resistance of the wire and consequently 
 cut down the current to half its original strength, 
 or to seven and a half amperes. Multiplying this 
 by 20 we again get 150 for the ampere turns, and 
 this would hold true in whatever way we change 
 the number of turns, keeping the E. M. F. and 
 size of wire constant. This will not be strictly 
 accurate where we have several layers of wire, 
 since the outer layers will be longer than the 
 inner ones and, consequently, have a greater re- 
 sistance. If the diameter of the core bears a large 
 ratio to the thickness of the layer of wire upon it 
 the rule will be nearly enough right for all practi- 
 cal purposes. 
 
 Suppose, then, that we have found out the num- 
 ber of ampere turns and know what E. M. F. we 
 are to have. Dividing the E. M. F. in volts by the 
 number of ampere turns we get the resistance 
 
ARMATURE AND FIELD-MAGNET WINDING. 49 
 
 required of a single turn of wire around the fields 
 to give the required number of ampere turns. 
 Find the average length of one turn of wire and 
 from a wire table find the size of wire which has 
 the desired resistance for this length. This is the 
 size wire to use. Of course, a single turn of this 
 wire would, under ordinary circumstances, be 
 burnt up by putting it on the E. M. F. of the 
 machine, so we must put on a large number of 
 turns, reducing the current in consequence, until 
 we have it too small to do any damage. It will 
 easily be seen that the greater number of 
 turns we put on the less energy necessary to 
 magnetize the fields, for more turns means a 
 higher resistance or less current, and the energy 
 used on the fields being equal to the current 
 through them, multiplied by the E. M. F., it natur- 
 ally follows that it is reduced in the same propor- 
 tion that the turns are increased. 
 
 It might seem at first as if we might, by increas- 
 ing the amount of copper on the fields, come at 
 last to the point where no energy is required to 
 rim them, but of course this would be impractica- 
 ble, for it would mean, in the first place, a resist- 
 ance equal to infinity, and in the second, that the 
 layer would have to be so thick that the rule given 
 above would no longer hold true. There is a limit 
 depending upon the money interest or the 
 copper used, and the cost of the energy lost. A 
 
50 AKMATURE AND FIELD-MAGNET WINDING. 
 
 process similar to that used by Sir William Thom- 
 son in determining the proper amount of copper 
 to use on a certain piece of wiring could be applied 
 here, but this is an unnecessary piece of refinement 
 and all that is really needful is to see that the wire 
 is long enough to reduce the current within safe 
 limits. 
 
 Often it will be found that no size of wire given 
 in the table will give the exact resistance called for, 
 and in that case you will have to use two different 
 sizes which fall on each side of the required resist- 
 ance, winding a few layers with one, and the rest 
 with the other. This is also the course to pursue, 
 if the winding when completed fails to give the 
 desired result. Unwrap a layer or two and rewind 
 with a different size wire, larger or smaller accord- 
 ing as you wish, the fields to be stronger or weaker. 
 
 The experimental method answers very nicely for 
 getting the data for compounding a machine. 
 Run your dynamo first unloaded and measure the 
 ampere turns as directed above, necessary to give 
 the E. M. F. Then run it on the full load and 
 again get the ampere turns. The first will give 
 you the ampere turns for the shunt winding, and 
 the difference between the first and second, the 
 ampere turns for the series. As this is not always 
 an even number it is customary in some places to 
 make the series coil larger than is really necessary, 
 and then put a German Silver shunt across its ends 
 
ARMATURE AND FIELD-MAGNET WINDING. 51 
 
 which will reduce the current in it to the proper 
 amount. This series coil is generally placed as 
 near the pole pieces as possible, and is often made 
 of flat strips of copper, these requiring less room 
 than round wire and being better adapted to radiate 
 the heat. 
 
 In making the above calculations some allowance 
 must be made for the increased resistance caused 
 by the rise in temperature. In the series machine 
 this does not play any part, as the current has to 
 get over the coils, but in the case of the shunt 
 coils where the current is determined by the re- 
 sistance, this must be taken into account. The 
 rise in resistance due to temperature is .21^0 for 
 every degree Fahrenheit. And it is well not to let 
 the wire get much above 110 or 1200, and a 
 lower temperature means much less waste of 
 energy. 
 
 The old rule for the safe carrying capacity of 
 copper wire, is to allow one square inch cross sec- 
 tion of wire for 1,000 amperes of current where 
 the wire is by itself, and one square inch cross sec- 
 tion for 400 or 500 amperes in places where the 
 wire is covered or surrounded by other wires. 
 Prof. Forbes says that wires used in winding which 
 are 2 millimetres in diameter will carry 5 to 6 am- 
 peres per square millimetre, and that wire 5 mil- 
 limetres in diameter will carry 3 amperes per square 
 millimetre. 
 
52 ARMATURE AND FIELD-MAGNET WINDING. 
 
 CHAPTER VII. 
 
 FIELD WINDING. 
 
 The method of winding will depend largely 
 upon the form of the field core, and we will briefly 
 discuss that before going further. 
 
 Cast iron cores will, in most cases, be cheapest 
 to construct, but a wrought iron core is always the 
 most effective electrically, as the formulae given 
 above show. A cast iron core can be made almost 
 any shape, but there is a limit to the number of 
 shapes in which wrought iron can be made, unless 
 an expensive amount of forging is done. 
 
 One wrought iron form, which can be made 
 without much trouble, is given in Fig. 24. 
 
 After bending into shape, the space for the 
 armature can be bored out and the winding slipped 
 over spools. 
 
 Another of the same style is shown in Fig. 25. 
 
 In this case it would be well to make it in two 
 pieces, and bolt together at A and B. This makes 
 it easier to get the winding on. 
 
 Often the cores, and perhaps yoke of the fields, 
 are made of wrought iron, as they are ordinarily 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 53 
 
 square or round pieces, and the poles made of 
 cast iron. The poles should, in this case, be made 
 more massive in proportion to the other parts than 
 if they were wrought iron. 
 
 In general, it is not advisable to have too many 
 breaks across the paths of the lines of force, and 
 
 FIG. 24. 
 
 FIG. 25. 
 
 for this reason the author does not think that one 
 form of field he has seen described is very desira- 
 ble, except for small machines, although it is of 
 the best wrought iron. It is made of a strip of 
 sheet iron, wrapped around a former, until the right 
 thickness is obtained. The lines of force have a 
 free path until they come to get into the armature, 
 
54 ARMATL'BE AND FIELD-MAGNET WINDING. 
 
 FORMS OF FIELD MAGNETS 
 
AKMATUUE AND FIELD-MAGNET WINDING. 55 
 
 [/-~\l 
 
 FORMS OF FIELD MAGNETS. 
 
56 
 
 ARMATURE AND FIELD-MAGNET WINDING. 
 
 and then they have to jump across from face to 
 face of the sheets. (See Fig. 26.) 
 
 A better way, and one adopted by a certain 
 prominent company, is to stamp out sheets of iron 
 into the proper shape and then bind them together 
 with the plane of their faces running lengthwise 
 of the magnet, but at right angles to the way 
 shown above. The pole pieces should not embrace 
 
 FIG. 26. 
 
 the armature more than the diameter of the arma- 
 ture core. (See Fig 27.) 
 
 Nor should they project beyond the ends of the 
 core for the reasons given in speaking of the 
 armature. The wire should always, where it is 
 possible to do so, be wound in a lathe, as it is much 
 less tedious and can be done more evenly. It can 
 be wound directly upon the field core, or may be 
 wound upon a spool and slipped over the core 
 afterwards. (See Fig. 28.) 
 
ABMATUIiE AND FIELD-MAGNET WINDING. 
 
 57 
 
 This spool is generally made of sheet iron to fit 
 closely upon the core, and is flanged at the open 
 ends to the depth of the winding. A flange made 
 of brass, with the edges polished, gives a very 
 neat appearance. A spool is generally used where 
 it is impossible to swing the cores in a lathe. 
 
 A double magnet, made in a solid piece, will 
 have to be wound by hand, as it is impossible to 
 swing it in a lathe or to put on a spool. Such 
 
 FIG. 27. 
 
 forms in general should be avoided. Before 
 commencing to wind, the bare metal must be in- 
 sulated with a couple of thicknesses of yellow 
 wrapping paper laid on with shellac. The starting 
 end of your wire, if the wire be small, must be 
 soldered to a larger piece of wire, preferably 
 with waterproof insulation, and this piece lead 
 out through a hole in one of the flanges to 
 make the connection. Wind the wire on in even 
 
58 ABMATUBE AND FIELD-MAGNET WINDING. 
 
 layers and drive the coils, every dozen turns, back 
 upon themselves with a smooth piece of wood and. 
 a light hammer, being careful not to abrade the 
 insulation. Double cotton-covered copper wire 
 should be used both for armature and fields. Shel- 
 lac each layer as you finish it and cover it with a 
 piece of paper before beginning the next. The 
 wire must be drawn tight enough to insure the 
 wire lying snugly. This tension is produced by 
 taking the wire around a number of grooved 
 
 FIG. 28. 
 
 wooden wheels which turn rather stiffly, but not 
 enough so that the wire will slide over them. (See 
 Fig. 29.) 
 
 When you commence to wind the next to the 
 last layer, tie a piece of string around the first turn 
 of wire and leave the ends hanging loose, and when 
 you return to that end, winding the last layer, tie 
 the last turn down by these strings, and this will 
 prevent the wire coming loose when the tension is 
 taken off. The winding should now be baked, 
 like the armature, and is then ready to be as- 
 
AK MATURE AND FIELD-MAGNET WINDING. 
 
60 ARMATURE AND FIELD-MAGNET WINDING. 
 
 sembled. The connections should all be soldered 
 and taped over, and the wire should be taped wher- 
 ever it comes in contact with the metallic work 
 about the machine. 
 
 Both fields and armature should be tested to see 
 that there is no contact with the core by trying to 
 ring a magneto from the wire to the core, and if 
 any contact is discovered it should be fixed at once. 
 Some manufacturers wind heavy twine around 
 the fields over the wire after it is all on. This 
 
 FIG. 30. 
 
 gives a neat appearance and protects the fine 
 wire from injury. The fields must be con- 
 nected up in such a way as to make the pole 
 pieces north and south magnetic poles. To 
 know if the pole is north or south, look at the 
 winding at the end from which it projects, and if 
 the current goes in the direction of the hands of a 
 watch, the pole is south, and if in the contrary 
 direction, north. (See Fig. 30.) 
 
 If more than two poles are used, they must 
 alternate north and south. 
 
 In making the armature and field connections, 
 
ARMATURE AND FIELD-MAGNET WINDING. 61 
 
 you must be careful to get the machine connected 
 for the way in which it is to run. A dynamo or 
 motor will not run in either direction indifferently. 
 
 If you run the dynamo in the wrong direction, 
 you get no current. 
 
 First make up your mind which way the machine 
 is to run, and then follow up the current and see 
 if it will magnetize the fields in the proper direc- 
 tion. If it will not, your connection must be 
 reversed. 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 Table of Dimensions and Resistances of Pure 
 Copper Wire.* 
 
 REVISED. 
 
 No. 
 B. &S. 
 
 Diam. 
 Mils. 
 
 Area. 
 
 W'gt & Length. Sp. gr. 8.9 
 
 Circular 
 Mils. 
 
 Square 
 Inches. 
 
 Lbs. 
 per 
 1000 ft. 
 
 Pounds 
 per 
 mile. 
 
 Feet 
 per 
 pound. 
 
 0000 
 000 
 00 
 
 
 460.000 
 409.640 
 364.800 
 324.950 
 
 211600.0 
 167805.0 
 133079.0 
 105592.5 
 
 166190.2 
 131793.7 
 104520.0 
 82932.2 
 
 640.73 
 508.12 
 402.97 
 319.74 
 
 3383 04 
 2682.85 
 2127.66 
 1688.20 
 
 I.o6 
 1.97 
 2.48 
 3.13 
 
 1 
 
 2 
 3 
 4 
 5 
 
 289.300 
 257.630 
 229.420 
 204.310 
 181.940 
 
 83694.5 
 66373.2 
 52633.5 
 41742.6 
 33102.2 
 
 65733.5 
 52129.4 
 41338.3 
 32784.5 
 25998.4 
 
 253.43 
 200.98 
 159.38 
 126.40 
 100.23 
 
 1338.10 
 1061.17 
 841.50 
 667.38 
 529.23 
 
 3.95 
 4.98 
 6.28 
 7.91 
 9.98 
 
 6 
 7 
 8 
 9 
 10 
 
 162.020 
 144.280 
 128.490 
 114 430 
 101.890 
 
 26250.5 
 20816.7 
 16509.7 
 13094.2 
 10381.6 
 
 20617.1 
 16349.4 
 12966.7 
 10284.2 
 8153.67 
 
 79.49 
 63.03 
 49.99 
 39.65 
 31.44 
 
 419.69 
 332.82 
 263.96 
 209.35 
 165.98 
 
 12.58 
 15.86 
 20.00 
 25.22 
 31.81 
 
 11 
 
 12 
 13 
 14 
 15 
 
 90.742 
 80.808 
 71.961 
 64.084 
 57.068 
 
 8234.11 
 6529.94 
 5178 39 
 4106.76 
 3256.76 
 
 6467.06 
 5128.60 
 4067.09 
 3225.44 
 
 2557.85 
 
 24.93 
 19.77 
 15.68 
 12.44 
 9.86 
 
 131.65 
 104.40 
 
 82.792 
 65.658 
 52.069 
 
 40.11 
 
 50.58 
 63.78 
 80.42 
 101.40 
 
 16 
 17 
 
 18 
 19 
 20 
 
 50.820 
 45.257 
 40.303 
 35.890 
 31.961 
 
 2582.67 
 2048.20 
 1624.33 
 1288.09 
 1021.44 
 
 2028.43 7.82 
 1608.65 6.20 
 1275.75 4.92 
 1011.66 3 90 
 802.24 3.09 
 
 41.292 
 32.746 
 25.970 
 20.594 
 16.331 
 
 127.87 
 161.24 
 203.31 
 256.39 
 323.32 
 
 21 
 22 
 23 
 24 
 25 
 
 28.462 
 25.347 
 22.571 
 20.100 
 17.900 
 
 810.09 
 642.47 
 509.45 
 404.01 
 320.41 
 
 636.24 
 504.60 
 400.12 
 317.31 
 251.65 
 
 2.45 
 1.95 
 1.54 
 1.22 
 .97 
 
 12.952 
 10.272 
 8.1450 
 6.4593 
 5.1227 
 
 407.67 
 514.03 
 648.25 
 817.43 
 1030.71 
 
 26 
 27 
 28 
 29 
 30 
 
 15.940 
 14.195 
 12.641 
 11.257 
 10.025 
 
 254.08 
 201.50 
 159.80 
 126.72 
 100.50 
 
 199.56 
 158.26 
 125.50 
 99.526 
 78.933 
 
 .77 
 .61 
 .48 
 .38 
 .30 
 
 4.0623 
 3.2215 
 2.5548 
 2.0260 
 1.6068 
 
 1299.77 
 1638.97 
 2066.71 
 2606.13 
 3286.04 
 
 31 
 32 
 33 
 34 
 35 
 
 8.928 
 7.950 
 7.080 
 6.304 
 5.614 
 
 79.71 
 63.20 
 50.13 
 39.74 
 31.52 
 
 62.603 
 49.639 
 39.369 
 31.212 
 24.753 
 
 .24 
 .19 
 .15 
 .12 
 .10 
 
 1.2744 
 1.0105 
 .8014 
 .6354 
 .5039 
 
 4143.18 
 5225.26 
 6588.33 
 8310.17 
 10478.46 
 
 36 
 37 
 38 
 39 
 40 
 
 5.000 
 4.453 
 3.965 
 3.531 
 3.144 
 
 25.00 
 19.83 
 15.72 
 12.47 
 
 9.88 
 
 1JK635 
 15.574 
 12.347 
 9.7923 
 7.7635 
 
 .08 
 .06 
 .05 
 .04 
 .03 
 
 .3997 
 .3170 
 .2513 
 .1993 
 
 .1580 
 
 13209.98 
 16654.70 
 21006.60 
 26427.83 
 33410.05 
 
 1 mile pure copper wire 1-16 in. diam.=13.59 ohms at 15.5C or 59.9F. 
 
AKMATUKE AND FIELD-MAGNET WINDING. 
 
 63 
 
 Table of Dimensions and Resistances of Pure 
 Copper Wire.* 
 
 REVISED. 
 
 No. 
 B. 
 
 & 
 S. 
 
 Resistance at 75F. 
 
 Ibs p. 1000 
 ft. ins'd 
 H.B.&H. 
 line wire. 
 
 Feet per 
 Ib. ins'd 
 H.B.&H. 
 line wire. 
 
 R 
 
 ohms per 
 1000 feet. 
 
 Ohms 
 per 
 mile. 
 
 Feet 
 per 
 
 ohm. 
 
 Ohms 
 per 
 pound. 
 
 4-0 
 3-0 
 00 
 
 
 .04904 
 .06184 
 .07797 
 .09827 
 
 .25891 
 .32649 
 .41168 
 .51885 
 
 20392.9 
 16172.1 
 12825.4 
 10176.4 
 
 .00007653 
 .00012169 
 .00019438 
 .00030734 
 
 800 
 666 
 500 
 363 
 
 1.25 
 1.50 
 2.00 
 2.75 
 
 1 
 2 
 3 
 4 
 
 5 
 
 .12398 
 .15633 
 .19714 
 .24858 
 .31346 
 
 .65460 
 .82543 
 1.04090 
 1.31248 
 1.65507 
 
 8066.0 
 6396.7 
 5072.5 
 4022.9 . 
 3190.2 
 
 .00048920 
 .00077784 
 .0012370 
 .0019666 
 .0031273 
 
 313 
 250 
 200 
 144 
 125 
 
 3.20 
 4.00 
 5.00 
 6.9 
 8.0 
 
 6 
 
 7 
 8 
 9 
 10 
 
 IT 
 
 12 
 13 
 14 
 15 
 
 .39528 
 .49845 
 .62849 
 .79242 
 .99948 
 
 2.08706 
 2.63184 
 3.31843 
 4.18400 
 5.27726 
 
 2529.9 
 2006.2 
 1591.1 
 1262.0 
 1000.5 
 
 .0049728 
 .0079078 
 .0125719 
 .0199853 
 .0317946 
 
 105 
 
 87 
 69 
 
 50 
 
 9.5 
 11.5 
 14.5 
 
 20.0 
 
 1.2602 
 1.5890 
 2.0037 
 2.5266 
 3.1860 
 
 6.65357 
 8.39001 
 10.5798 
 13.3405 
 16.8223 
 
 793.56 
 629.32 
 499.06 
 395.79 
 313.87 
 
 .0505413 
 .0803641 
 .127788 
 .203180 
 .323079 
 
 31 
 
 22 
 
 32.0 
 45.0 
 
 16 
 17 
 18 
 19 
 20 
 
 4.0176 
 5.0660 
 6.3880 
 8.0555 
 10.1584 
 
 21.2130 
 26.7485 
 33.7285 
 42.5329 
 53.6362 
 
 248.90 
 197.39 
 156.54 
 124.14 
 98.44 
 
 .513737 
 .816839 
 1.298764 
 2.065312 
 3.284374 
 
 14 
 11 
 
 70.0 
 
 90.0 
 
 21 
 
 22 
 23 
 24 
 25 
 
 12.8088 
 16.1504 
 20.3674 
 25.6830 
 32.3833 
 
 67.6302 
 85.2743 
 107.540 
 135.606 
 170.984 
 
 78.07 
 61.92 
 49.10 
 38.94 
 30.88 
 
 5.221775 
 8.301819 
 13.20312 
 20.99405 
 33.37780 
 
 
 
 26 
 27 
 28 
 29 
 30 
 
 40.8377 
 51.4952 
 64.9344 
 81.8827 
 103.245 
 
 215.623 
 271.895 
 342.854 
 432.341 
 545.133 
 
 24.49 
 19.42 
 15.40 
 12.21 
 9.686 
 
 53.07946 
 84.39916 
 134.2"05 
 213.3973 
 339.2673 
 
 
 
 31 
 
 32 
 33 
 34 
 35 
 
 130.176 
 164.174 
 207.000 
 261.099 
 329.225 
 
 687.327 
 866.837 
 1092.96 
 1378.60 
 1738.31 
 
 7.682 
 6.091 
 4.831 
 3.830 
 3.037 
 
 539.3404 
 857.8498 
 1363.786 
 2169.776 
 3449.770 
 
 
 
 36 
 37 
 38 
 39 
 40 
 
 415.047 
 523.278 
 660.011 
 
 832.228 
 1049.718 
 
 2191.45 
 2762.91 
 3484.86 
 4394.16 
 5542.51 
 
 2.409 
 1.911 
 1.515 
 1.202 
 .9526 
 
 5482.766 
 8715.030 
 13864.51 
 22043.92 
 35071.11 
 
 
 
 1 mile pure copper wire 1-16 in. diam.=13.59 ohms at 15.5C. or 59.9F. 
 
64 ABMATURE AND FIELD-MAGNET WINDING. 
 
 CHAPTER VIII. 
 
 DYNAMOS. 
 
 WE will now take a brief survey of some of the 
 dynamo electric machines manufactured by the 
 leading companies of the United States. 
 
 The Thomson-Houston Arc Dynamo. In this 
 machine the field magnets are cup shaped, they 
 consist of two cast iron tubes, furnished at their 
 inner ends with hollow cups, cast in one with the 
 tubes, and accurately turned to receive the arma- 
 ture ; upon these tubes are wound the coils ; after- 
 wards the magnets are united by means of a num- 
 ber of wrought iron bars, which constitute the 
 yoke of the magnet, and at the same time protect 
 the coils. The magnets are carried on a frame- 
 work, which also supports the bearings for the 
 armature shaft. 
 
 All late machines have ring armatures (see Figs. 
 3132), which are a great improvement over the old 
 style (spherical armature) in the way of better ven- 
 tilation, higher insulation, greater freedom from 
 burning out, and the ease with which faulty coils 
 can be removed and new ones substituted. 
 
ARMATURE AND FIELD-MAGNET WINDING. 
 
 65 
 
ARMATURE AND FIELD MAGNET WINDING. 
 
 COMMUTATOR END 
 
 FIGURES 31 AND 32. 
 
AKMATURE AND FIELD-MAGNET WINDING. 67 
 
 These armatures are interchangeable with the 
 old style armature, and can be used in any M. D. or 
 L. D. machine. The commutator has only three 
 segments in contact with which are four brushes. 
 Regulation is obtained by an electro-magnet reg- 
 ulator, which controls the amount of current by 
 automatic shifting of the brushes, in such a way 
 that they short circuit one of the armature coils 
 for a greater or less period of time as the occasion 
 may require, when from a reduction of resistance 
 in the lamp circuit, by the extinguishing of a lamp, 
 or otherwise, the current feeding the other lamps 
 becomes liable to abnormal increase; this increase 
 of current is made to flow through the coils of wire 
 surrounding the iron core of the regulator magnet. 
 The core becomes magnetized, causing the yoke 
 to which the brushes are attached to be drawn up 
 towards the regulator magnet which changes the 
 position of the brushes upon the commutator, so 
 that they draw away from the maximum point, 
 decreasing the potential, when more lights are 
 turned on the reverse action takes place. The 
 current governing the regulator is cut in and out 
 by means of a pair of electro-magnets termed the 
 controler magnets, and are connected with the reg- 
 ulator magnet of the dynamo. 
 
 Sparking at the commutator is reduced by a 
 blower, being so placed that it sends a current of 
 air directly on to the point of contact of the brushes 
 
68 AKMATUKE AND FIELD-MAGNET WINDING. 
 
 and the commutator which blows out the spark. 
 The largest machines have an electro-motive force 
 of 3000 volts, and will maintain 63 arc lights in a 
 single circuit. 
 
 The Edison Direct Current Dynamo. The field 
 magnets consist of vertical cylinders with large 
 wrought-iron cores, which rest upon cast-iron pole 
 pieces, and nearly enclose the armature. The 
 armature is drum shaped. (See Figs. 33 and 34.) 
 
 The core consists of a number of sheet-iron discs, 
 insulated from each other by sheets of thin paper. 
 The core is mounted on an iron shaft, but insulated 
 from it by an interior cylinder of lignum vitae, 
 while an external covering of paper insulates it 
 from the coils. The coils consist of cotton covered 
 copper wire, stretched longitudinally and grouped 
 together in parallel, a number of wires in a group, 
 all of the group being so connected as to form a 
 continuous closed circuit. The groups are ar- 
 ranged in concentric layers, and are of the same 
 number as the segments of the commutator, the 
 ends of the wires in each group being attached to 
 arms connecting with the commutator segments, 
 a spiral arrangement being adopted in making the 
 connections between the straight portion of the 
 wire and the arms. The object of grouping is to 
 secure flexibility for winding by the use of small 
 wire and low electrical resistance, by having 
 
ABMATUKE AND FIELD-MAGNET WINDING. 69 
 
 EDISON DIRECT CURRENT DYNAMO. 
 
70 
 
 ARMATURE AND FIELD-MAGNET WINDING. 
 
 SPl 
 
ARMATUUE AND FIELD-MAGXET WINDING. 71 
 
 several wires in parallel, the effect as to the resist- 
 ance being practically the same as if the several 
 wires were combined in one. At the ends the 
 wires are insulated from the core by discs of vul- 
 canized fibre with projecting teeth. The discs* of 
 the core are bolted together by insulated rods, and 
 the coils are confined by brass bands surrounding 
 the armature. The brushes are composed of 
 several layers of copper wires, combined with flat 
 copper strips, two layers of wire being placed 
 between each two strips. This arrangement is to 
 give a more perfect connection, and to prevent 
 sparking by furnishing numerous points of contact, 
 the copper strips confining the wire and making 
 the brush more compact. 
 
 The Westinghouse Alternating Current Dynamo, 
 for generating the alternating current, is repre- 
 sented by the accompanying illustration. The field 
 is composed of a series of radial pole pieces having 
 alternate polarity, the cores of which are cast solid 
 with the base and cap respectively. The field coils 
 are a series of bobbins each independent of all the 
 others which are wound on shells, slipped over the 
 pieces and held up by bolts at the periphery. 
 The bobbins being supplied with a feeble current 
 from the exciter are of course subject to no natural 
 deterioration and are not liable to accident. They 
 can only be damaged by extraneous carelessness, 
 
72 
 
 AKMATUKE AND FIELD- MAGNET WINDING. 
 
 and, when such is the case, the cap of the dynamo 
 is removed and any bobbin taken out and replaced 
 in a few moments. The armature is removed in 
 the same manner, as the whole structure of the 
 dynamo, including the pole pieces and the bearings, 
 parts along a horizontal plane through the shaft. 
 The engraving shows the side of the dynamo 
 which carries the collecting ring ; the other side 
 
 WESTINGHOUSE ALTERNATING CURRENT DYNAMO. 
 
 has a similar bearing, beyond which is an over- 
 hung pulley. This pulley is of compressed straw- 
 board, which in experience is found to exceed all 
 other material for belt traction. The dynamo 
 rests upon a cast iron base and is adjustable by 
 means of a belt tightener. The dynamo can run 
 
ARMATURE AND FIELD-MAGNET WINDING. 73 
 
 in either direction and stand either way around on 
 the base. This of course adapts it universally to 
 any situation. 
 
 The armature is a structure of great directness 
 and simplicity. The body of the armature is of lam- 
 inated iron plates freely perforated for ventilating 
 purposes. A single layer of wire is wound in flat 
 coils back and forth across the face of the armature 
 in a direction parallel to the shaft, being retained 
 by stops on the ends of the armature. Mica and 
 other adequate insulation is provided and the 
 whole is wrapped with binding wire. A ventilator 
 is attached to each end of the armature and draws 
 a strong current of air through it. 
 
 The observer will be struck by the simplicity of 
 the winding on an alternating current armature as 
 compared with that necessary in the direct current 
 machines. The total weight of copper on a 750 
 light armature is 16 Ibs., disposed in a single layer, 
 which being on the surface is readily kept cool, 
 and which can be inspected for deterioration or 
 flaws of any character. A direct current armature 
 of type most generally in use of 750 lights capacity 
 on the other hand carries more than 10 times this 
 amount of wire. 
 
 The armatures are uniformly wound to deliver 
 1,000 volts, and a higher voltage than this, for 
 special circuits, is obtained by raising through a 
 special converter. 
 
74 ARMATURE AND FIELD-MAGNET WINDING. 
 
 The New Multipolar Generator, Made by the 
 Westinghouse Electric & Manufacturing Com- 
 pany, of Pittsburg, Pa., see illustration. In this 
 machine the pole pieces project radially from the 
 interior of the cylindrical yoke pieces, and by the 
 peculiar construction ready access may be had to 
 the field coils and armature. The machines are all 
 wound for 500 volts, E. M. F., but by means of 
 a rheostat this can be raised to 550 or 600 volts. 
 They are self-exciting and compound wound ma- 
 chines. The armature is a distinctive feature. It 
 is of the Siemens' type, the core of which is built 
 up in the usual way, of a large number of thin iron 
 discs which are rigidly keyed to the shaft. The 
 wires are not placed on the exterior of the core, as 
 is usually done, but are placed in insulating tubes 
 which are embedded in the iron of the core. This 
 construction obviates the use of binding wires. A 
 special method of winding is used, and the amount 
 of wire necessary is reduced to a minimum. The 
 commutators are long and massive. The brush 
 holders are composed of independent holders, thus 
 allowing each carbon brush to be removed without 
 disturbing the others. The machine is carefully 
 regulated, designed for railway use and to require 
 a minimum amount of attention. 
 
AKMATURE AND FIELD-MAGNET WINDING. 75 
 
 WESTINGHOUSE MULTIPOLAR GENERATOR. 
 
76 ARMATURE AND FIELD-MAGNET WINDING. 
 
 CHAPTER IX. 
 
 MOTORS. 
 
 THE dynamo generates electricity, and is driven 
 by mechanical means. The electric motor fur- 
 nishes power, and is actuated by electricity gene- 
 rated from a dynamo or an electric battery. The 
 field winding of a motor is adapted to the work, 
 which it is to perform. Series winding is used 
 when a variable speed is required and where the 
 regulation may be attended to by hand, its chief 
 advantage being in its great starting power. Shunt 
 winding is used where constant speed is required. 
 Compound winding is theoretically more correct, 
 but a shunt winding will regulate the machine 
 closely enough for all practical purposes, and is 
 the one most commonly used. A brief description 
 of some of the machines manufactured by the lead- 
 ing electrical companies will give the reader 
 a general understanding of their different styles 
 of mechanical and electrical construction. 
 
 The Crocker-Wheeler Electric Motor, of which 
 two illustrations are given, on pages 78 and 80, 
 
ARMATURE AND FIELD-MAGNET WINDING. 77 
 
 possess some special features of merit which are 
 as follows : 
 
 The field magnets are composed entirely of the 
 best wrought-iron, each magnet being forged in a 
 single piece, and set deeply into the base in order 
 to secure solidity and ample magnetic contact. 
 The space for wire on these magnets is perfectly 
 cylindrical, in the form of an ordinary spool, there- 
 by insuring smooth and perfect winding of the 
 wire, and is short in length, permitting the shaft 
 of the machine to be low enough to free it from 
 vibration. By this construction the neutrality or 
 freedom of the base from magnetism is secured, 
 and there is no tendency to leakage. This is 
 claimed to make the machine much superior to 
 those in which the base is made to serve as one of 
 the pole pieces, as the bearings then become mag- 
 netized and make the shaft bind. 
 
 The armatures contain several improvements. 
 They are sufficiently large in diameter to obtain 
 slow speed, and are so designed that the wire 
 winding is entirely embedded below the surface of 
 the iron core, thus protecting it from all injury, 
 holding it rigidly in position, and rendering it 
 possible for the magnets to approach very closely 
 to the core, so that an intense magnetic effect is 
 produced. The armature is mounted upon a brass 
 face-plate, which is first turned perfectly true, and 
 after completion the armature is very carefully 
 
78 ARMATURE AND FIELD-MAGNET WINDING. 
 
 CROCKER-WHEELER ELECTRIC MOTOR. 
 
ARMATURE AND FIELD -MAGNET WINDING. 79 
 
 balanced, so that when run at full speed the motion 
 is hardly perceptible. 
 
 The bearings are all of the self -oiling type, which 
 do not require attention oftener than once in two 
 to four weeks. 
 
 The base of the pillow-block is hollow, and con- 
 tains a supply of oil, which is carried over the shaft 
 by two rings which travel upon the latter, and are 
 caused to revolve by its motion. They dip in the 
 oil and carry it continuously to the upper side of 
 the shaft. 
 
 The bushings in which the shaft runs Vest in turn 
 in universal or ball joints in seats of babbit metal 
 in pillow-blocks, so that the bearings are sure to 
 assume perfect alignment when the shaft is intro- 
 duced. After the motor has run a month, the 
 old oil containing the grit, etc., [should be drawn 
 off from the pet cock at the base of the pillow 
 block. This cock should then be closed and fresh 
 oil introduced by removing the thumb screw in 
 the pillow block cap on top. 
 
 The brushes are held by rocker arms which can 
 revolve freely around the entire circle, without fear 
 of the brass connecting parts "grounding" against 
 the frame, a great advantage in special work where 
 motors are to be adapted for use in unusual positions. 
 
 With this form of armature core which reaches 
 close to the field magnets, and the high grade of 
 wrought-iron used for the latter, it is claimed they 
 
80 ARMATURE AND FIELD-MAGNET WINDING. 
 
 SKELETON VIEW, SHOWING INTERNAL CONSTRUCTION OF 
 CROCKER-WHEELER ELECTRIC MOTOR. 
 
ARMATURE AND FIELD-MAGNET WINDING. 81 
 
 are enabled to maintain the magnetism and there- 
 fore the power of these motors, with only about 
 one-third as much wire as is used on the fields of 
 ordinary standard machines. This great saving of 
 wire not only reduces the weight of the machine, 
 but materially increases its efficiency, or the amount 
 of power that can be obtained from a given amount 
 of electricity, for with less wire less electricity is 
 required. 
 
 The speed of motors is very low, which in many 
 cases makes counter-shafting, etc., unnecessary. 
 
 The proximity of the armature core to the field 
 magnets renders a high magnetic pressure un- 
 necessary, therefore the magnetism escaping from 
 the fields is very much reduced. 
 
 Double insulated wire is used throughout for the 
 windings, the cores being first wrapped with oiled 
 paper and heavy canvas saturated with shellac. 
 
 The rocker arm is provided with a heavy insula- 
 ted handle to enable all adjustments to be made 
 without touching the conducting parts, and the en- 
 tire machine is heavily japaned and baked at a high 
 temperature, thus securing a polished surface which 
 resists dirt and oil. 
 
 In connection with their incandescent motors, 
 they furnish fire-proof and indestructible regulating 
 boxes or rheostats for starting, stopping and vary- 
 ing the speed of the machines. These are built 
 entirely of slate, china and iron. The arrangement 
 
82 AKMATURE AND FIELD-MAGNET WINDING. 
 
 of contacts in the switch on top of the regulator 
 is such that both the field and armature of the mo- 
 tor are charged by the single operation of turning 
 the knob, making it impossible to put the current 
 on the armature before the field is charged, which 
 has so often been the cause of the accidental burn- 
 ing out of many motors by the use of ordinary 
 regulators. 
 
 The field is first charged through a small resist- 
 ance coil which is put in for the purpose of prevent- 
 ing a too sudden change in the magnetic strength 
 of the latter, as well as to divide the spark when 
 the motor is disconnected. The coils used for start- 
 ing the armature are all of the same size wire 
 carefully tried for carrying the full current of the 
 machine at all speeds. With the fire-proof regu- 
 lator, the motor can therefore be slowed down and 
 left running at any desired speed, indefinitely, and 
 the usual caution "never to leave the box half turned 
 on for fear of overheating and fire" is unnecessary. 
 
 The Thomson-Houston Stationary Motor. The 
 15 horse-power motor shown in the illustration on 
 next page has an average commercial efficiency 
 when fully loaded of 91 per cent. This high effi- 
 ciency is obtained by paying careful attention to 
 the electric and magnetic proportioning of the 
 motor. 
 
 The magnetic circuit is very short and of ample 
 
ARMATURE AND FIELD-MAGNET WINDING. 83 
 
 THOMSON-HOUSTON STATIONARY MOTOR. 
 
84 ARMATURE AND FIELD-MAGNET WINDING. 
 
 section, and therefore of low resistance, and the 
 magnetic poles are so formed as to convey the mag- 
 netism into the armature with the least possible 
 loss. As will be noted in the engraving, the poles 
 of the field-magnets, the bodies or cores of which 
 are round in section, project upward, enclosing the 
 armature. The armature is nearly square in long- 
 itudinal section and relatively large in diameter. 
 
 This gives a high peripheral velocity and a. rapid 
 cutting of the lines of force. In consequence of 
 this construction, also, the armature is capable of 
 exerting a powerful rotative force. The armature 
 being short, avoids the use of a long and conse- 
 quently less rigid shaft. The coils of the motor- 
 magnet are wound on bobbins which are slipped 
 over the cores ; it is therefore easy to change a 
 coil or to replace it for any purpose whatever. 
 
 The field is wound in shunt to the armature, and 
 is relatively of a very high resistance. 
 
 This reduces the amount of electrical energy re- 
 quired to energize the field-magnet to a very small 
 fraction of the total electrical energy absorbed by 
 the motor. The armature bore is thoroughly well 
 built and is a very solid and substantial structure. 
 
 At the same time the perfect lamination of the 
 core reduces the loss by Foucault currents to a 
 small amount. 
 
 The winding on the armature, which is a modifi- 
 
ARMATURE AND FIELD-MAGNET WINDING. 85 
 
 cation of the well-known Siemens' type, is of very 
 low resistance. 
 
 The copper wire on the armature is held in place 
 by means of bands, which are made of such strength 
 that it is impossible for them to yield from the 
 centrifugal force, even when the motors are run at 
 abnormal speed. 
 
 The Ford & Washburn Electric Motor oi Cleveland, 
 is shown in the illustration. The special improve- 
 ment, they claim, puts their motor far in advance 
 of many others and places the use of electricity for 
 lighting within the reach of the smallest plants, is 
 its self-ventilating feature ; but the motor itself 
 possesses many points of superiority. The bed 
 plates and brackets are one complete casting. 
 
 The magnet yokes are wrought iron fastened to 
 the bed plate, and the pole pieces are separate cast- 
 ings bolted to magnet yokes. The field cores are 
 wound on separate shells, and are interchangeable 
 for all machines of same size. The armature shaft 
 is steel and of extra large size. 
 
 The especial feature of their motor, as above 
 stated, is the armature, which is self-ventilating. 
 
 It draws a current of air from both ends and 
 along the line of shaft and out through the discs,, 
 which are separated, and through the winding, with 
 openings to let the air pass out. The rapid rotary 
 motion of the armature sends out the current of air,. 
 
ARMATURE AXD FIELD-MAGXET WIXIHXG. 
 
 FIG. 35. 
 
 FIG. 36. 
 
ARMATURE AND FIELD-MAGNET WINDING. 87 
 
 which keeps the armature and pole pieces cool and 
 therefore more effective than the old style which 
 is so liable to heat up. This self- ventilating feature 
 it is claimed, is found in no other motor at present 
 manufactured. It is adapted to both motors and 
 dynamos. Fig. 35 shows the motor; Fig. 36 shows 
 the armature. 
 
 The Neiv Mather Motors and Power Generators. 
 Recognizing the demand for power transmission 
 by means of electric current, the Mather Electric 
 Company has bought out a series of machines for 
 that purpose, which, while embodying the essential 
 features of the well-known Gramme ring type, can 
 be more readily insulated against the high potentials 
 required for power service. 
 
 One of the essential features of the old type of 
 Mather machines was a field magnet having the 
 form approximately of the magnetic lines of force 
 and consisting of one piece. In the new type the 
 cores of the field magnet are straight, permitting 
 the use of coils of wire that can be wound separate- 
 ly on a machine, while the rest of the magnetic 
 circuit is practically a ring, and the whole, includ- 
 ing the cores and pole pieces, is cast in one piece 
 without a joint. 
 
 The motors are built in sizes of I, 3, 6 and 10 
 h. p. with two poles and 20, 30 and 40 h. p. with 
 four poles. The generators are built up to 30,000, 
 
88 ARMATURE AND FIELD-MAGNET WINDING. 
 
 NEW MATHER MOTOR. 
 
ARMATURE AND FIELD-MAGNET WINDING. 89 
 
 50,000 and 75,000 watts with four poles, and 180,- 
 ooo watts with six poles. Drum armatures are used 
 in all the machines. In the four-pole machines the 
 winding is such that the current -has but two paths 
 through the armature wires, and by a special meth- 
 od, devised by Prof. Anthony, no two wires having 
 any great difference of potential are brought near 
 each other. 
 
 The illustration represents the /5,ooo-watt gen- 
 erator, with the field magnet in one casting. In 
 the i8o,ooo-watt six-pole machine the field magnet 
 is cast in two halves, but divided through the mid- 
 dle of two opposite poles instead of across the mag- 
 netic circuit. The small motors are wound and 
 kept in stock for 220 volts, but can easily be wound 
 for no or 500 volts, when desired. The winding 
 is such that in no case is there a loss in the arma- 
 ture of more than four per cent, and the speeds run 
 from 1,500 revolutions for the 10 h. p. to 2,500 for 
 the i h. p. The variation in speed from full load 
 to no load is never more than four per cent. 
 
 TJie Thomson-Houston W. P. Raihvay Motor. 
 The following description was taken from the 
 Electrical World: 
 
 One of the most interesting exhibits at the Pitts- 
 burgh Street Railway Convention was a new slow 
 speed railway motor of the Thomson-Houston com- 
 pany, of which the accompanying illustrations give 
 
90 AKMATUKE AND FIELD-MAGNET WINDING. 
 
 an excellent idea. It has been in process of evolu- 
 tion for six months or more and has been worked up 
 under the careful superintendence of Mr. Walter 
 Knight. The new machine embodies some decided- 
 ly novel features acnd its excellent performance on 
 the special car equipped with it was very favorably 
 commented upon. It is known to the trade a's the 
 W. P. motor, which being interpreted means water- 
 proof, and it well deserves the name, because of 
 the particularly complete iron-clad character of the 
 field magnets. 
 
 Fig. 37 gives a perspective view of the motor, 
 and from it the arrangement of the iron is at once 
 obvious. Singularly enough, it is a two-pole machine 
 so arranged on the theory that the comparatively 
 slight gain in weight efficiency that could be ob- 
 tained with a mutipolar type is more than offset by 
 the increased complication of the windings. The 
 only portions of the machine open to the outside 
 air are exposed at the two oval openings at the ends 
 of the armature shaft, and even these can be easily 
 fitted with covers should such a course prove de- 
 sirable. The whole magnetic circuit is composed 
 of two castings bolted together and free to swing 
 apart by a hinge allowing ready access to the ar- 
 mature. 
 
 Fig. 38 gives an excellent idea of the internal 
 arrangements. The armature itself is very nearly 
 twenty inches in diameter, a very powerful Pacinotti 
 
A.K.MATUBE AXI> FIELD-MAGNET WINDING. 91 
 
 FIG. 37. 
 
 FIG. 38. 
 
92 ARMATURE AND FIELD-MAGNET WINDING. 
 
 ring nearly six inches on the face and of about the 
 same depth. It is wound with comparatively coarse 
 wire in sixty-four sections, with fourteen turns to 
 the section. Each coil is tightly placed in the 
 space between two of the projecting teeth, and 
 about the interior space the separate coils are 
 closely packed, leaving only sufficient room for the 
 four-armed driving spider. 
 
 As will be seen, the armature takes up most of 
 the full height of the machine, the pole pieces be- 
 ing but trifling projections and the requisite cross- 
 section of iron being obtained by extending the 
 poles to form a closely fitting iron box that appears 
 in the exterior view. An unusual feature is the 
 use of but a single magnetizing coil wound not di- 
 rectly about the upper pole piece but on the casing 
 immediately surrounding it. The lower pole is but 
 slightly raised and both pole pieces are of the 
 greatest extent permissible with the dimensions of 
 the machine. The use of a single magnetizing 
 coil produces naturally an unbalanced field and a 
 strong upward pull on the armature tending to re- 
 lieve the pressure on the bearings. The iron-clad 
 form, however, tends to distribute the lines of 
 force so as to avoid the sparking and change of 
 lead that might otherwise have to be feared. The 
 single coil is wound with quite coarse wire and its 
 position insures the maximum magnetic effect 
 from the current. 
 
ARMATURE AND FIELD-MAGNET WINDING. 93 
 
 The speed of the new motor is about the same 
 as that of the older S. R. G. form, but its general 
 working efficiency is somewhat better, owing not 
 so much to a greater maximum of efficiency as to 
 a better working curve at both heavy and light 
 loads. The brush holders are shown in the cut, 
 and the slots in which they fit render their position 
 evident. The brushes are of the ordinary carbon 
 description and are readily accessible through the 
 opening at the end of the shaft. 
 
 In operation the W. P. motor has been highly 
 satisfactory. It runs with but trifling sparking and 
 no heating to speak of, gives a very powerful 
 torque, and is singularly free from liability to dam- 
 age of the armature, for which its careful insula- 
 tion and the Pacinotti form adopted are responsi- 
 ble. It is now being regularly manufactured at the 
 Thomson-Houston works, and it is expected to 
 take with great advantage the place in popular fa- 
 vor of the S. R. G, motor that has made so good a 
 reputation for itself during the past summer. It is 
 an interesting departure, both electrically and me- 
 chanically, and aside from its special features its 
 general qualities of iron-clad field, gears running 
 in oil, and the ease of access to the working parts 
 will commend it to the practical street railway 
 man. 
 
 TJie Porter Electric Motor is shown by the ac- 
 companying engraving. It is an extremely effi- 
 
94 ARMATURE AND FIELD-MAGNET WINDING. 
 
 PORTER ELECTRIC MOTOR. 
 
ARMATURE AND FIELD-MAGNET WINDING. 95 
 
 cient battery motor and is very simple in its con- 
 struction. It has but one field winding and its 
 armature is of the Siemens type. 
 
 Three sizes are made, viz., No. I, 52 h. p. No. 
 2, ^ h. p., and No. 3, ^ The No. 3, or largest 
 size, will run a 6-inch ventilating fan or a family 
 sewing machine. It has no dead centre and there- 
 fore starts instantly upon the application of the 
 current, which may be furnished by a storage cell 
 or a bicromate battery. The Taylor battery will 
 be found an excellent battery for running this ma- 
 chine when one does not wish to use a storage 
 cell. 
 
 The No. 3 motor weighs six pounds. Is 5^ 
 inches long, 4^ inches high and 4^ inches wide. 
 
 The Ferret Motor. The chief distinctive feature 
 of this machine is the lamination of the field mag- 
 net. Instead of casting or forging this in several 
 solid pieces, as is usually done, it is built of thin 
 plates of soft charcoal iron, which are stamped di- 
 rectly to their finished form and clamped together 
 by bolts in such a manner as to secure great me- 
 chanical strength. 
 
 The advantages of such a construction are, in 
 brief, a magnetic field of great intensity and the 
 entire prevention of all wasteful induced currents 
 in magnets and pole-pieces. 
 
 The armature core is also laminated, and the 
 
ARMATURE AND FIKI.D-M AftNET WINDING. 
 
 THE FERRET MOTOR. 
 
ARMATUIIE AND FIELD-MAGNET WINDING. 97 
 
 plates have teeth, which form longitudinal chan- 
 nels on its periphery, in which the coils are wound. 
 
 The plates in both field and armature are in the 
 same plane, and are of soft charcoal iron, with its 
 grain running in the direction of the line of mag- 
 netic force, and there is the least possible break in 
 the continuity of the circuit, there being no air 
 gap between the iron of the field and the iron 
 teeth of armature, except that required for clear- 
 ance in rotation. Thus we have a magnetic circuit 
 of lowest possible resistance, and it follows from 
 well-known laws that we secure the maximum of 
 effective magnetism with a minimum expenditure 
 of magnetizing power. 
 
 The armature coils being practically imbedded 
 in the armature, receive the highest inductive ef- 
 fect from the intensely magnetized iron. * 
 
 The high efficiency which such construction 
 should give theoretically is practically demon- 
 strated by the machines in actual work, and ranges 
 from 70^) in the smaller to 93^ in the larger. 
 
 Attempts have been made by many since the 
 days of Pacinotti to use toothed armatures, but 
 with the result that very troublesome and wasteful 
 heating effects were produced in the solid magnets 
 and pole pieces commonly used. With laminated 
 field magnets these disadvantages are avoided, and 
 we are able to secure the advantages enumerated, 
 as well as others, among which may be mentioned 
 
98 
 
 ARMATUKE AND FIELD-MAGNKT WI.VDING. 
 
 FIG. 39. 
 
ARMATURE AND FIELD-MAGNET WINDING. 99 
 
 the important ones, positive driving of the arma- 
 ture coils and less liability of winding out of bal- 
 ance. 
 
 It will be seen that the armature is a ring of 
 comparatively large diameter, with longitudinal 
 channels on its periphery, in which the conductors 
 are wound, and thus embedded in the iron, which 
 is in such close proximity to the iron pole pieces 
 that there is practically no gap in the magnetic 
 circuit. 
 
 The field consists of three separate magnets 
 arranged at equal distances around the armature, 
 each magnet having two pole pieces. See Fig. 39. 
 The winding is such as to produce alternate North 
 and South poles. The magnets are built up of 
 plates of soft charcoal iron, which are shaped as 
 shown in the diagram, and the magnet thus pro- 
 duced is of such a form that it may be readily 
 wound in a lathe. A non-magnetic bolt passes 
 through a hole in each pole piece and the plates 
 are clamped together between washers and nuts on 
 the same. These bolts also serve to attach the 
 magnets to the two iron end frames, which are of 
 ring shape and are bolted to the bed plates of the 
 machine. 
 
 The magnetic circuit is of unusally low resist- 
 ance by reason of its shape, its shortness, which is 
 shown by the diagram, and the superior quality of 
 iron used. 
 
100 ARMATURE AND FIELD-MAGNET WINDING. 
 
 There is no magnetism whatever in the frame, 
 bed or shaft of the machine, as the magnets are 
 supported at some distance from the frame by 
 means of the non-magnetic bolts, and the armature 
 is mounted on the shaft by spiders of non-mag- 
 netic metal. 
 
 There is therefore no opportunity for magnetic 
 leakage, and, furthermore, the whole is enclosed 
 by a shield or case of sheet metal, as shown in the 
 illustration on page 96. 
 
 The practical advantages of low speed machines 
 are many. For instance, in ordinary machine 
 shops, wood-work shops, printing offices, etc., the 
 shaft is commonly run 200 to 300 revolutions per 
 minute, and it is a simple matter to belt direct to 
 it from a motor running 500 to 600 revolutions, 
 thus saving the first cost of a counter-shaft and 
 one belt) and saving, also, considerable power 
 which would be lost in transmitting through the 
 counter-shaft and additional belt, which would be 
 used necessarily with a motor of high speed. The 
 advantage is equally as great in case of elevators 
 operated by a belt from the motor, and indeed, it 
 is possible to gear direct from the motor to the 
 elevator. 
 
 The Excelsior Motor. The engraving on page 
 101 illustrates the arc light circuit or constant cur- 
 rent motor of the Excelsior Electric Co. This 
 
ARMATTJKE AND FIELD-MAGNET WINDING. 101 
 
 THE EXCELSIOR MOTOR. 
 
102 ARMATURE AXD FIELD-MAGXET WINDING. 
 
 motor has its armature and field-magnet coils con- 
 nected in series. As it is supplied with current by 
 a generator whose electro-motive force is varied by 
 an automatic regulator to suit the demands of the 
 motors on its circuit, it would run at a constantly 
 increasing speed, when lightly loaded, were it not 
 regulated and the speed kept uniform by a govern- 
 ing device. This consists of a centrifugal gov- 
 ernor which controls the strength of the field-mag- 
 nets by cutting out the successive layers of wire 
 in the coils as the load decreases, and cutting them 
 in when it increases. 
 
 The two main bearings of the motor-shaft and 
 the ball and socket bearings of the governor are 
 provided with oil chambers, from which the oil is 
 led to the wearing surfaces by means of felt strips. 
 
 The Wightman Single-Reduction Railway Motor. 
 Among the very first to recognize the desira- 
 bility of as well as the possibility of eliminating 
 one set of transmission gears in electric street 
 railway cars was Mr. Merle J. Wightman, who, as 
 electrician of the Wightman Electric Manufactur- 
 ing Co., of Scranton, Pa., over a year ago com- 
 menced experiments towards the development of a 
 slow-speed single-reduction motor. The results of 
 this work are embodied in the motor shown in the 
 accompanying engraving, Fig. 40, from which 
 it will be seen that the " Kennedy" type 
 
AHMATUISK AM) FI1- I.D-MAGXtT WINDING. 
 
 103 
 
104 ARMATURE AND FIELD-MAGNET WINDING. 
 
 of field-magnet is employed. This form of field- 
 magnet has the advantage of almost completely 
 covering the field coils and producing an "iron 
 clad" moton It gives a very strong and efficient 
 field and all four poles are excited by two field 
 windings. 
 
 The armature is of the Gramme type, and the 
 commutator is cross-connected so that but two 
 brushes are used, placed at an angle of 90 degrees 
 and on top of the commutator. 
 
 The cross-connecting of the commutator is ac- 
 complished in a remarkably simple way. All the 
 crossing cables are formed symmetrically into a 
 flat disc which is firmly bolted to the head of the 
 commutator and becomes an integral part of it. In 
 this way all possibility of vibration and risk of 
 breakage is overcome. The commutator lead-wires 
 are all of flexible cable, after the Wightman Com- 
 pany's well-known method of armature winding. 
 These lead-wires are fastened to the commutator 
 without screws and in such a way that they can be 
 detached in a few minutes, when it becomes neces- 
 sary to remove a commutator. The armature is 
 mounted within a strong, continuous frame form- 
 ing part of the field magnets. The bearings are 
 self -oiling and dust-proof, and are designed to be 
 used with grease, oil, or both. 
 
 Either field winding is removable without dis- 
 turbing the other or the armature, each winding 
 
ABMATUKE AND FIELD MAGNET WINDING. 105 
 
 FlG. 41. FIELD WINDING OF WIGHTMAN SINGLE 
 REDUCTION RAILWAY MOTOR. 
 
 ARMATURE OF WIGHTMAN SINGLE REDUCTION 
 RAILWAY MOTOR. 
 
106 ARMATURE AND FIELD- MAGNET WINDING. 
 
 being made up of separate coils, one of which is 
 shown in Fig 41. The removal of two bolts at one 
 end makes it possible to lift out one of the fields, 
 after which the armature can be taken out. The 
 top field pole is hinged at one end for convenience 
 in removing the fields or armature. 
 
 The ratio of the reduction of the gearing is 4.4 
 to i, the armature pinion having fifteen teeth and 
 a diameter of five inches. This ratio gives about 
 480 revolutions of the armature at a car-speed of 
 10 miles an hour. 
 
 The aim of the designer of the Wightman mo- 
 tor has been to attain as great an efficiency as pos- 
 sible with the wide variation of speed and load met 
 with in street railway practice. This has been ob- 
 tained by means of large field magnets of a great 
 number of turns of wire. In fact, speed regula- 
 tion is obtained without the use of any external 
 resistance above three or four miles an hour. On a 
 level, cars equipped with two 2O-h. p. Wightman 
 motors have frequently attained a speed above 
 twenty-five miles an hour. 
 
 Mr. Wightman's experience has led him to the 
 belief that there is no economy in operating mo- 
 tors of small capacity. Many roads are operated 
 in such a way that cars are barely maintained on 
 schedule time by dangerous and reckless running 
 on down grades. A little calculation will show 
 that by the expenditure of a little more power, 
 
ARMATURE AND FIELD-MAGNET WINDING. 107 
 
 grades may be climbed rapidly, and as a result, 
 much more service can be gotten from a given ex- 
 penditure in wages for conductors and motor-men 
 and interest on plant ; and the cost of the extra 
 coal will be comparatively insignificant. It is 
 much safer to climb grades rapidly rather than to 
 descend them at a high rate of speed, not to men- 
 tion the greater satisfaction of patrons. When 
 climbing a grade a stoppage of power and applica- 
 tion of brakes will bring a car to a standstill within 
 surprisingly short distance. Since the wear and 
 tear of ample-sized motors is obviously less than 
 those overworked, all consideration of economy 
 and safety would therefore point to the use of the 
 former. 
 
 While in the Wightman motor electrical per- 
 fection has not been sought for at the expense of 
 simplicity and durability, a very high efficiency is 
 obtained. The armature resistance of the 20 h. p. 
 motor is .75 ohm, and that of the main field coils 
 .15 ohm, with a load of 40 amperes, or over 26 
 electrical horse power ; this would give a loss of 
 potential in the motor of 36 volts, or an electrical 
 efficiency of 92.8. Even with this excessive load 
 the commercial efficiency has been found to be as 
 high as 87 per cent. The large field, referred to 
 above, makes possible a high efficiency at low 
 speed and light loads. These qualities are synony- 
 mous with powerful torque or starting force. 
 A loaded car equipped with Wightman motors 
 requires not more than from 15 to 20 amperes to 
 start on a level. 
 
108 ARMATURE AND FIELD-MAGNET WINDING. 
 
 APPENDIX A. 
 
 ELECTRICAL AND MAGNETIC UNITS. 
 
 AMPERE. The unit of current strength. It is 
 the flow of electricity produced by the pressure 
 of one volt on a resistance of one ohm. 
 
 COULOMB. The unit of electric quantity. It 
 is the amount of electricity which flows past a 
 given point in one second on a circuit conveying 
 one ampere. 
 
 FARAD. The unit of capacity. A condenser 
 that will hold one coulomb at a pressure of one 
 volt has a capacity of one farad. 
 
 OHM. The unit of electrical resistance. Ohms 
 law states that the current in any circuit is 
 equal to the E. M. F. acting on it divided by its 
 resistance. 
 
 VOLT. The unit of electro-motive force or pres- 
 sure analogous to the head of water in hy- 
 draulics. 
 
ARMATURE AND FIELD-MAGNET WINDING. 109 
 
 WATT. The unit of work. ^ of a horse 
 power, i.e. 746 Watts equal i horse power. We 
 may find the Watts used in a circuit by three 
 formulae, thus : 
 
 Watts=Amperes (squared) X ohms. 
 Watts=Amperes X volts. 
 Watts=Volts (squared) -4- by ohms. 
 
 DYNE. The absolute unit of force. It is that 
 force which if it acts on one gramme for one 
 second gives to it a velocity of one centimetre 
 per second. In the *C. G. S. system the unit 
 of magnetism is the force of a magnetic pole, 
 which repels an equal pole at the distance of 
 one centimetre with a force of one dvne. 
 
 *C. G. S. The abbreviation of centimetre, gramme, second, 
 and used to designate the so-called absolute system of meas- 
 urement, viz. : The (Centimetre) the unit of length. The 
 (Gramme) the unit of mass. The (Second) the unit of time. 
 
110 AKMATUKE AND FIELD-MAGNET WINDING. 
 
 SIGNIFICATIONS 
 
 OF SIGNS USED IN CALCULATIONS. 
 
 = signifies equality, thus 5-1-2=7. 
 
 -f- signifies addition, thus 3-)- 2=5. 
 
 signifies substraction, thus 8 6=2. 
 
 X signifies multiplication, thus 5X315- 
 
 -f- signifies division, thus i8-f-3=6. 
 
 : : : : signifies proportion, thus 2 is to 3 . 
 
 y signifies square root thus \ =4. 
 ty signifies cube root, thus -3/64=4. 
 
 3 2 signifies 3 is to be squared 3 2 =9- 
 
 3 3 signifies 3 is to be cubed 3 3 =27. 
 
ARMATUKE AND FIELD-MAGNET WINDING. 
 
 Ill 
 
 APPENDEX B. 
 
 USEFUL TABLES. 
 TABLE OF ELECTRICAL UNITS. 
 
 UNIT OF 
 
 NAME 
 
 DERIVATION. 
 
 Dimen- 
 sions in 
 C. G. S. 
 Units. 
 
 Electromotive 
 force 
 
 Resistance 
 
 Volt 
 Ohm . . 
 
 Ampere X Ohm. . 
 Volt ~=~ Ampere. . . . 
 
 I0 8 
 I0 9 
 
 Current . 
 
 Ampere 
 
 Volt Ohm 
 
 I0 1 
 
 Quantity.. . 
 
 Coulomb 
 
 Ampere X Second 
 
 I0 1 
 
 Capacity 
 
 Farad 
 
 Coulomb Volt. . . 
 
 I0 9 
 
 
 
 
 
112 
 
 ARMATURE AND 'FIELD-MAGNET WINDING. 
 
 TABLE SHOWING THE DIFFERENCE BETWEEN WIRE GAUGES. 
 
 
 New 
 
 
 
 Brown & 
 
 No. 
 
 British. I 
 
 London. 
 
 Stubs'. , 
 
 Sharpens. 
 
 0000 .... 
 
 .400 .... 
 
 .454 .... 
 
 .454 .... 
 
 .460 
 
 000 .... 
 
 .372 .... 
 
 .425 .... 
 
 .425 .... 
 
 .40964 
 
 00 .... 
 
 .348 .... 
 
 .380. . . . 
 
 .380 .... 
 
 .36480 
 
 
 
 .324 .... 
 
 .340 .... 
 
 .340 .... 
 
 .32495 
 
 1 
 
 .300 .... 
 
 .300 .... 
 
 .300 .... 
 
 .28930 
 
 2 
 
 .276 .... 
 
 .284 .... 
 
 .284 .... 
 
 .25763 
 
 3 
 
 .252 .... 
 
 .259 .... 
 
 .259 .... 
 
 .22942 
 
 4 
 
 .232 .... 
 
 .238 .... 
 
 .238 .... 
 
 .20431 
 
 5 
 
 .212 .... 
 
 .220 .... 
 
 .220 .... 
 
 .18194 
 
 6 
 
 .193 .... 
 
 .203 .... 
 
 .203 .... 
 
 .16202 
 
 7 
 
 .176 .... 
 
 .180 .... 
 
 .180 .... 
 
 .14428 
 
 8 
 
 .160 .... 
 
 .165 .... 
 
 .165 .... 
 
 .12849 
 
 9 
 
 .144 .... 
 
 .148 .... 
 
 .148 .... 
 
 .11443 
 
 10 
 
 .128 .... 
 
 .134 .... 
 
 .134. . . . 
 
 .10189 
 
 11 
 
 116 
 
 .120 . . 
 
 .120 .... 
 
 .09074 
 
 12 
 
 .10J .... 
 
 .109 .... 
 
 .109 .... 
 
 .(,8081 
 
 13 
 
 .092 .... 
 
 .095 .... 
 
 .095 ..,. 
 
 .07196 
 
 14 
 
 .080 .... 
 
 .083 .... 
 
 .083 .... 
 
 .06408 
 
 15 .. 
 
 .072 .... 
 
 .072 .... 
 
 .072 .... 
 
 .05706 
 
 16 
 
 .064 .... 
 
 .065 .... 
 
 .065 .... 
 
 .05082 
 
 17 . . . . 
 
 .056 .... 
 
 .058 .... 
 
 .058 .... 
 
 .04525 
 
 18 
 
 .048 .... 
 
 .049 .... 
 
 .049 .... 
 
 .04030 
 
 i9 
 
 .040 .... 
 
 .040 .... 
 
 .042 .... 
 
 .03589 
 
 20 
 
 .030 .... 
 
 .035 . . . 
 
 .035 .... 
 
 .03196 
 
 21 
 
 .032 .... 
 
 .0315 . . . 
 
 .032 .... 
 
 .02846 
 
 22 
 
 .028 . . 
 
 .0295 . . . 
 
 .028 .... 
 
 025347 
 
 23 
 
 .024 .... 
 
 .027 .... 
 
 .025 .... 
 
 .022571 
 
 24 
 
 .022 .... 
 
 .02'> .... 
 
 .022 .... 
 
 .0201 
 
 25 
 
 .020 .... 
 
 .023 .... 
 
 .023 .... 
 
 .0179 
 
 26 
 
 018 
 
 .0105 . . . 
 
 .018 .... 
 
 .01594 
 
 27 
 
 .0164 . . . 
 
 .01875 . . . 
 
 .016 .... 
 
 .014195 
 
 28 
 
 .0148 . . . 
 
 .0165 . . . 
 
 .014 .... 
 
 .012641 
 
 29 
 
 .0136 . . . 
 
 .0155 . . . 
 
 .013 .... 
 
 .011257 
 
 30 
 
 .0124 . . . 
 
 .01375 . . . 
 
 .012 .... 
 
 .010025 
 
 31 . . 
 
 .0116 . . . 
 
 .01225 . . . 
 
 .010 .... 
 
 .008928 
 
 09 
 
 Oi 
 
 .0108 . . . 
 
 .01125 . . . 
 
 .009 .... 
 
 .00795 
 
 33 
 
 .0100 . . . 
 
 .01025 . 
 
 .008 .... 
 
 .00708 
 
 34 
 
 .0092 . . . 
 
 .009) . . . 
 
 .007 .... 
 
 .0063 
 
 35 
 
 .0084 . . . 
 
 .009 .... 
 
 .005 .... 
 
 .00561 
 
 36. 
 
 .0075 . 
 
 .0075 . 
 
 .004. 
 
 .005 
 
AKMATURK AND FIELD-MAGNET WINDING. 
 
 113 
 
 Table of Different Ganges, with their Diameters and Areas in Mils. 
 
 1 
 
 STANDARD 
 
 
 i 
 
 AMERICAN 
 
 
 a 
 
 RMINGHA 
 
 M. 
 
 No of 
 Gauge. 
 
 Diameter 
 in Mils. 
 
 Area In 
 CM=d 
 
 No. of 
 Gauge. 
 
 Diameter 
 in Mils. 
 
 Area in 
 CM=d2 
 
 No. of 
 Gauge. 
 
 Diameter 
 in Mils 
 
 Area in 
 CM=d 
 
 7-0 
 
 500 
 
 250000 
 
 
 
 
 
 
 
 6-0 
 
 464 
 
 21o296 
 
 4-0 
 
 4600 
 
 211600 
 
 4-0 
 
 454 
 
 206116 
 
 6-0 
 
 A J 32 
 
 
 
 
 
 3-0 
 
 425 
 
 180625 
 
 4-0 
 
 
 160000 
 
 3-0 
 
 4096 
 
 167805 
 
 
 
 
 3-0 j 
 
 rJ 372 
 
 138384 
 
 2-0 
 
 3648 
 
 133079 
 
 2-0 
 
 380 
 
 144400 
 
 3-0 J 
 
 '/ 348 
 
 121104 
 
 
 
 
 
 
 340 
 
 1156(10 
 
 
 ' 324 
 
 104976 
 
 
 
 3249 
 
 105592 
 
 
 
 
 IM 
 
 300 
 276 
 
 90000 
 76176 
 
 
 2893 
 
 83694 
 
 
 300 
 384 
 
 90000 
 80656 
 
 JT 
 
 262 
 
 63504 
 
 
 2576 
 
 66373 
 
 
 259 
 
 67081 
 
 9 
 
 232 
 
 6S824 
 
 
 2294 
 
 62634 
 
 
 238 
 
 
 
 312 
 
 44944 
 
 
 
 
 
 220 
 
 48400 
 
 6 
 
 7 
 
 192 
 
 176 
 
 36864 
 30976 
 
 
 2043 
 1819 
 
 41742 
 8Si02 
 
 
 HI 
 180 
 
 41309 
 32400 
 
 8 
 
 160 
 
 26600 
 
 
 162 
 
 26244 
 
 
 165 
 
 37225 
 
 9 
 
 141 
 
 20736 
 
 
 1443 
 
 20822 
 
 
 148 
 
 21904 
 
 10 
 
 128 
 
 16384 
 
 
 1285 
 
 16613 
 
 1 
 
 134 
 
 179T6 
 
 Table of Different Gauges, with their Diameters and Areas in Mils, 
 
 STANDARD 
 
 AMERICAN. 
 
 BIRMINGHAM 
 
 No. of 
 
 Diameter 
 
 Area In 
 
 No. of 
 
 Diameter 
 
 Area In 
 
 NO Of 
 
 Diameter 
 
 Area tn 
 
 Gauge. 
 
 111 MllB. 
 
 M=d* 
 
 Gauge. 
 
 lu Mils. 
 
 CM=d* 
 
 Gauge. 
 
 in Mils. 
 
 CM=dt 
 
 11 
 
 llrt 
 
 13456 
 
 9 
 
 11* \ 
 
 13110 
 
 11 
 
 120 
 
 14400 
 
 12 
 
 
 10816 
 
 10 
 
 1019 
 
 10381 
 
 12 
 
 109 
 
 11881 
 
 13 
 
 IN 
 
 MM 
 
 11 
 
 01107 
 
 8*26 
 
 13 
 
 095 
 
 90% 
 
 
 on 
 
 6400 
 
 12 
 
 0808 
 
 R.V28 
 
 14 
 
 083 
 
 6889 
 
 15 
 
 072 
 
 8181 
 
 13 
 
 073 
 
 5184 
 
 16 
 
 072 
 
 5184 
 
 16 
 
 061 
 
 4096 
 
 14 
 
 UMI 
 
 4110 
 
 16 
 
 065 
 
 4229 
 
 17 
 
 056 
 
 S1S6 
 
 15 
 
 0571 
 
 3260 
 
 17 
 
 (168 
 
 3364 
 
 18 
 
 048 
 
 23U4 
 
 16 
 
 0508 
 
 2581 
 
 18 
 
 049 
 
 2401 
 
 
 
 
 17 
 
 .0*52 
 
 2044 
 
 19 
 
 042 
 
 1764 
 
 19 
 
 040 
 
 1600 
 
 18 
 
 0403 
 
 1624 
 
 
 
 
 90 
 
 036 
 
 1296 
 
 19 
 
 0359 
 
 1253 
 
 20 
 
 035 
 
 1325 
 
 i 
 
 032 
 028 
 
 1024 
 784 
 
 20 
 21 
 
 032 
 0286 
 
 1024 
 
 M 
 
 i 
 
 032 
 028 
 
 1024 
 784 
 
 93 
 
 024 
 
 576 
 
 93 
 
 0253 
 
 626 
 
 33 
 
 025 
 
 635 
 
 84 
 96 
 
 023 
 
 5 
 
 484 
 400 
 
 93 
 34 
 
 0226 
 0301 
 
 MO 
 404 
 
 
 033 
 030 
 
 484 
 400 
 
 
 
 IS 
 
 M4 
 
 
 
 179 
 
 330 
 
 5 
 
 U18 
 
 Stt 
 
BUBIER'S 
 POPULAR ELECTRICIAN. 
 
 A SCIENTIFIC ILLUSTRATED MONTHLY, 
 
 FOB TUB II1TEUR MB PUBLIC AT URGE. 
 
 Containing descriptions of all the new inventions as fast as 
 they are patented, also lists of patents filed each month at the 
 Patent Office in Washington, D. C. Interesting articles by 
 popular writers on scientific subjects written in a way that 
 the merest beginner in science can understand. 
 
 Price, Postpaid, 5O Cents a Year. 
 
 SAMPLE COPY FIVE CENTS. 
 
 it. You will be more than pleased. ^^ffl 
 
 Mer Publishing Company, - Lp, Mass. 
 
JUST PUBLISHED. 
 
 A - PRACTICAL - TREATISE 
 
 ON THE 
 
 BY J. E. RANDALL, 
 
 Electrician of the Incandescent Lamp Dept. 
 of the Thomson-Houston Co. 
 
 ILLUSTRATED. 
 
 This is the only work that explains in a practical manner the 
 
 manufacture of the Incandescent Lamp, and should be 
 
 owned by every Electrician and Student 
 
 interested in this subject. 
 
 PRICE, 5O CENTS, CLOTH. POSTPAID. 
 
 BUSIER PUBLISHING COMPANY, 
 
 LYNN, : : MASS. 
 
New and Practical Book. 
 
 Dynamos and Electric Motors, 
 
 And All About Them. 
 By EDWARD TREVERT. 
 
 Nearly 1OO Illustrations. 
 
 This volume not only gives practical directions for building 
 Dynamos and Electric Motors, but also contains a large quantity 
 of information about them. 
 
 It is particularly adapted to beginners in this absorbing 
 science. 
 
 CHAP. I. What is a dynamo ? What is a motor ? 
 
 CHAP. II. Some different types of dynamos. 
 
 CHAP. III. How to construct a dynamo. 
 
 CHAP. IV. Some different types of electric motors. 
 
 CHAP. V. How to build an electric motor. 
 
 CHAP. VI. A cheaply constructed electric motor. 
 
 CHAP. VII. How to make an electric battery for run- 
 ning electric motors. 
 
 PRICE, CLOTH, 5O CENTS. 
 
 POSTAGE PAID. 
 
 Bubier Publishing Company, 
 
 LYNN, - MASS. 
 
-AN IMPORTANT WORK-s 
 
 A BOOK FOR EVERYBODY. 
 
 NOW READY. 
 
 "Experimental * Electricity," 
 
 BY EDWARD TREYERT. 
 
 AUTHOR OF "EVERYBODY'S HAND-BOOK OF ELECTRICITY,'* 
 
 AND "HOW TO MAKE ELECTRIC BATTERIES AT HOME." 
 
 This book contains about 200 pages, and is fully illus- 
 trated with about 50 engravings. 
 
 It will give practical information upon the following 
 subjects : 
 
 CHAP. 1. Some Easy Experiments in Electricity and 
 
 Magnetism. 
 
 2. How to Make Electric Batteries. 
 3. How to Make a Galvanometer. 
 4. How to Make an Electric Bell. 
 5. How to Make an Induction Coil. 
 6. -'How to Make a Magneto Machine. 
 7. How to Make a Telegraph Instrument. 
 8. How to Make an Electric Motor. 
 9. How to Make a Dynamo. 
 10. Electric Gas Lighting and Bell Fitting. 
 
 Some practical directions for amateurs. 
 11. Some information in regard to Electric Lamps. 
 
 JUST THE BOOK FOR AMATEURS. 
 Price, Cloth Bound, $1.OO. Postage Paid. 
 
 Send in your orders at once and they will be 
 promptly filled. 
 
 BUSIER PUBLISHING CO., LYNN, MASS. 
 
Practical Directions 
 
 FOR 
 
 AND- 
 
 field-Magnet (flinding. 
 
 BY ED WARD TREVERT. 
 
 ILLUSTRATED with nearly 50 Engravings and contains a 
 vast amount of valuable information, both in theory and 
 practice upon this subject. It also contains working 
 directions for Winding Dynamos and Motors, with addi- 
 tional Descriptions of some of the apparatus made by the 
 several leading Electrical Companies in the U. S. 
 
 CONTENTS. 
 
 INTRODUCTION. 
 
 CHAPTER 1. The Armature in Theory. 
 
 CHAPTER 2. Forms of Armatures. 
 
 CHAPTER 3. Drum Winding. 
 
 CHAPTER 4. Field Winding. 
 
 CHAPTER 5. Field Formulae. 
 
 CHAPTER 6. General Methods of Winding. 
 
 CHAPTER 7. Field Winding concluded. 
 
 CHAPTER 8. Dynamos. 
 
 CHAPTER 9. Motors. 
 
 PRICE, S1.5O, Postpaid. 
 
 BUBIER PUBLISHING COMPANY, 
 
 LYNN, - MASS. 
 
A PRACTICAL BOOK! 
 
 PRICE, 25 CENTS. 
 
 NOW READY. 
 
 "How to JMe Electric Bat- 
 teries at Home." 
 
 By EDWARD 
 
 ILLUSTRATED. 
 
 This little volume will contain just the information needed 
 to make Simple, yet Practical Electric Batteries (both open 
 and closed circuit), by which you can run Electric Motors, In- 
 candescent Lamps, or operate Telegraph Lines, ring Electric 
 Bells, etc. It will inform you of the necessary articles required 
 for their manufacture, giving price of the same as near as pos- 
 sible the expense of making such batteries being so small 
 that any schoolboy may afford them. Most of the articles re- 
 quired can be obtained at home or at the neighboring drug 
 store. 
 
 YOU CANNOT AFFORD TO BE WITHOUT THIS BOOK. 
 
 Sent Postpaid on Receipt of Price. 
 
 Send in Your Orders at Once and They Will 
 be Filled Promptly. 
 
 Bubier Publishing Co., Lynn, Mass. 
 
A NEW BOOK! 
 
 BY EDWARD TREVERT. 
 
 f Everybody's Hand-Book of Electricity. 
 
 ZHITrTnR HF 1 How ^ Make Electric Batteries at Home. 
 JrlU 1 llUlv UT | Experimental Electricity. 
 
 ( Dynamos and Electric Motors. 
 
 "Electricity and its Recent Applications." 
 
 Containing nearly 350 pages and about 250 Illus. 
 
 This work is printed on extra fine heavy paper, is bound in a, 
 neat cloth binding, and lettered in gold. It is particu- 
 larly adapted to the use of Students. 
 
 CONXKNTS. 
 
 CHAP. 1. Electricity and Magnetism. 
 
 CHAP. 2. Voltaic Batteries. 
 
 CHAP. 3. Dynamos, and How to Build One. 
 
 CHAP. 4. The Electric Arc, and The Arc Lamp. 
 
 CHAP. 5. Electric Motors and How to Build One. 
 
 CHAP. 6. Field Magnets. 
 
 CHAP. 7. Armatures. 
 
 CHAP. 8. The Telegraph and Telephone. 
 
 CHAP. 9. Electric Bells. How Made, How Used. 
 
 CHAP. 10. How to Make an Induction Coil. 
 
 CHAP. 11. The Incandescent Lamp. 
 
 CHAP. 12. Electrical Mining Apparatus. 
 
 CHAP. 13. The Modern Electric Railway. 
 
 CHAP. 14. Electric Welding. 
 
 CHAP. 15. Some Miscellaneous Electric Inventions of the 
 
 Present Day. 
 
 CHAP. 16. Electro-Plating. 
 CHAP. 17. Electric Gas Lighting Apparatus. 
 CHAP. 18. Electrical Measurement. 
 CHAP. 19. Resistance and Weight Table for Cotton and Silk 
 
 Covered and Bare Copper Wire. 
 CHAP. 20. Illustrated Dictionary of Electrical Terms and 
 
 Phrases. 
 
 PRICE $2.OO. 
 
 BUSIER PUBLISHING CO., Lynn, Mass. 
 
THIS BOOK IS DUE ON THE LAST DATE 
 STAMPED BELOW 
 
 AN INITIAL FINE OF 25 CENTS 
 
 WILL BE ASSESSED FOR FAILURE TO RETURN 
 THIS BOOK ON THE DATE DUE. THE PENALTY 
 WILL INCREASE TO SO CENTS ON THE FOURTH 
 DAY AND TO $1.OO ON THE SEVENTH DAY 
 OVERDUE. 
 
 
 
 
 APR Itf 1935 
 
 
 
 
 
 
 4 *T.lG 
 
 
 JUI i> ^ 
 
 = 
 
 iPM 
 
 
 
 MP,V 1_13S..&J7. 
 
 Rc.C t 1 - - 
 
 JAN 2 fe '66- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 T TI 01 i nn Q to A 
 
 

 UNIVERSITY OF CALIFORNIA LIBRARY