CONTINUOUS-CURRENT WINDINGS 147 



Then we may take 



y& = 15 and *//=15 (Fig. 174), 

 or 



3/6 = 17 and y/=13 (Fig. 175), 



as both of these comply with our formula, which merely requires 

 that y (mean) shall be equal to 15. 



The use of such a small number of conductors, while it aids in 

 the study of windings, is in some respects very misleading. Thus 

 with the far larger numbers of conductors generally occurring in 

 actual practice, these differences in the choice of pitch have a far 

 smaller percentage effect on the winding ; and hence may be 

 employed when useful purposes are thereby served, as we shall 

 soon show to occasionally be the case. 



WINDINGS WITH MORE THAN ONE TURN PER SEGMENT. 



In the diagrams so far drawn, we have only had instances of 

 windings with one turn per commutator segment ; and we have 

 represented the two face conductors, constituting the two sides of 

 a turn, by numbered radial lines. When, as is necessary in many 

 designs, instead of a single turn between two segments there is a 

 coil of two, three, or more turns, we may still retain the same 

 general scheme of constructing and numbering the winding 

 diagram. In these cases we need merely make the mental reser- 

 vation that each pair of radial lines, instead of representing the 

 two conductors forming the two sides of a single turn, represents 

 the two groups of conductors forming the two sides of a coil. 

 Were we to represent the entire number of conductors by radial 

 lines, the enormous number of lines and connections would not 

 only require, in preparation, a large amount of time and labour, 

 but the result would be a very confusing diagram. 



In Figs. 176 and 177 are shown respectively a single three- 

 turn coil and the corresponding commutator segments for a 

 multiple-circuit winding (Fig. 176), and a two-circuit winding (Fig. 

 177). Below these, in Figs. 178 and 179, are shown the corre- 

 sponding diagrammatic representation which, in complete diagrams, 

 it is preferable to adopt, and in which the group of three face 

 conductors is in each case replaced by a single line ; the lines 

 corresponding to the front end connections of the unrepresented 

 turns being suppressed. 



In Fig. 330, p. 278, is shown a section through the slot of- a 

 four-turn-per-coil winding, with three segments per slot. Such 



