ARMATURE WINDINGS AND SLOT INSULATION 87 



The two kinds of winding are shown diagrammatically in 

 Figs. 28 and 29. The former shows a simplex lap-wound 

 multipolar drum armature, while the latter represents in a 

 similar diagrammatic manner a simplex wave-wound multipolar 

 drum armature. In practice there would ordinarily be a greater 

 number of coils and commutator bars, and the conductors would 

 be in slots. This is indicated by the grouping of the conductors 



FlG 28. Diagram of simplex multiple winding. 



in pairs, the even-numbered inductors being (say) in the bottom 

 of the slot, with the odd-numbered inductors immediately 

 above them in the top of the slot. 



It should particularly be noted that the lap or multiple win 

 ing provides as many electrical circuits in parallel as there are 

 poles, and the number of brush sets required is the same as 

 number of poles. Thus if I is the current in the external cir nt, 

 plus the small component required for the shunt field excitation, 

 the current in the armature windings is I/p and the current 



27 

 collected by each set of brushes is 



