ARMATURE WINDINGS. 429 



A doubly reentrant winding is one in which if one starts at 

 inductor No. I and traces through the successive inductors in the 

 order of winding, only one-half of the whole winding has to be 

 traced through before inductor No. I is reached or reentered ; 

 the other half being exactly like this first half. 



A triply reentrant winding, in a similar manner, is a winding 

 which on being traced through from conductor No. I and back 

 to the starting point still leaves two thirds of the total inductors 

 to be traced through. 



In tracing through the successive inductors of the winding, 

 one may pass around the armature once, twice, or any number 

 of times before reaching the starting point. The number of times 

 one passes around the armature in tracing through a reentrant 

 set of inductors has no essential relation to the degree of reen- 

 trancy. For example, in tracing through a singly reentrant drum 

 winding, one may pass around the armature as many as twenty- 

 five or more times. 



48. Simplex and multiplex windings. Consider two similar 

 drum simplex lap windings like Figs. 52 and 53. Let these 

 windings with their commutators be designated as A and B. 

 Imagine the winding B to have its inductors sandwiched between 

 the inductors of winding A on the same core, and imagine the 

 commutator segments of winding B to be likewise sandwiched 

 between the commutator segments of winding A. We now have 

 an armature core upon which there are 36 inductors and a com- 

 mutator having 1 8 segments ; odd numbered segments belong- 

 ing to winding A and even numbered segments to winding B. 

 If the original brushes in Figs. 52 and 53 are made thick 

 enough to touch always at least two segments of this doubled 

 commutator, then windings A and B are in parallel between 

 the brushes, and the number of paths in parallel through the 

 armature winding between positive and negative brushes is 

 doubled. The winding here described is called a duplex lap 

 winding and it is doubly reentrant. 



