ARMATURE WINDINGS. 441 



the commutator pitch is 2 ; and all of the conditions necessary 

 for duplex lap windings as given in Art. 5 1 are satisfied. This 

 winding presents 12 paths in parallel between the brushes, 6 

 paths through each constituent simplex winding, and it requires 

 6 brush sets, each brush being thick enough to always touch at 

 least two adjacent commutator segments. 



Fig. 59 shows a six pole drum duplex wave winding having 

 64 inductors. The dotted lines and shaded commutator seg- 

 ments represent a complete simplex wave winding having 32 in- 

 ductors, and the full lines and blank commutator segments repre- 

 sent another identically similar simplex wave winding. These 

 two simplex windings when sandwiched together, as shown in 

 Fig. 59, form a duplex wave winding. This duplex winding is 

 of course doubly reentrant according to Art. 47, inasmuch as 

 each of the constituent simplex windings reenters itself. In this 

 winding the back pitch is -f 1 1 , the front pitch is + 9, the aver- 

 age pitch is 10, and the commutator pitch is 10; and all the 

 conditions necessary for duplex wave windings as given in Art. 

 5 1 are satisfied. This winding presents four paths in parallel be- 

 tween the brushes, two paths through each constituent simplex 

 winding, and two brush sets are sufficient as shown in Fig. 59. 



Fig. 60 shows a six-pole drum duplex wave winding which 

 is singly reentrant. This duplex winding cannot be looked upon 

 as two simplex windings sandwiched together. In this winding 

 the back pitch is -f- 1 1 , the front pitch is -f- 1 1 , the average pitch 

 is -f n and the commutator pitch is -f n. This winding pre- 

 sents four paths in parallel between the brushes, two paths each 

 way from each of the two broad brushes, as may be seen by 

 tracing through the windings from brush to brush in Fig. 60. 

 Two brush sets are sufficient for this winding as shown in Fig. 60. 



It will be noticed that the inductors of the simplex windings 

 shown in Figs. 56 and 57 are grouped in pairs which are drawn 

 very close together. The same is true of the constituent simplex 

 windings in Figs. 58 and 59. This is intended to show the com- 

 mon arrangement in slotted armatures where the even numbered 



