ARMATURE WINDINGS. 431 



there are Z\2 inductors in series between the positive and the 

 negative brushes, in the wave winding. 



In a multipolar machine, with a given total number of induc- 

 tors Z y the lap winding gives many more paths in parallel between 

 brushes, and fewer inductors in series in each path, than the wave 

 winding Therefore the use of lap winding is sometimes called 

 parallel grouping of the inductors, and the use of wave winding 

 is sometimes called series grouping of the inductors. 



Furthermore, on account of the fact that the simplex lap wind- 

 ing has / paths in parallel between brushes, this winding is some- 

 times called a multiple -circuit winding, and on account of the fact 

 that the simplex wave winding has only two paths in parallel be- 

 tween brushes (independently of the number of poles) this wind- 

 ing is sometimes called a two-circuit winding. 



Combining simplex windings to give a multiplex winding al- 

 ways multiplies the number of paths in parallel between brushes. 

 Thus a duplex winding multiplies the number of paths by 2, a 

 triplex winding multiplies the number of paths by 3 and so on. 

 Combining simplex windings to give a multiplex winding does 

 not alter the number of inductors in series between brushes, and 

 hence does not alter the electromotive force of one of the com- 

 ponent simplex windings namely the electromotive force between 

 the brushes. 



The number of inductors in series between brushes (and hence 

 the electromotive force of the machine) may be multiplied by 

 using a coil of many turns, instead of two inductors, in forming 

 an element of the winding. Thus in Figs. 52 and 53, the ele- 

 ment terminating in segments I and 2 may be made into a coil 

 as follows : Let each inductor shown in the figure represent a 

 slot in the armature core. Then starting from segment No. i we 

 may wind a wire up slot No. I and down slot No. 6 any number 

 of times before connecting to segment No. 2. This group of 

 turns constituting one winding element is called a coil or section 

 of the armature winding. 



