428 ELEMENTS OF ELECTRICAL ENGINEERING. 



is on account of this wave-like appearance that this winding is 

 called the wave winding. 



In Figs. 54 and 55 it may be seen that the back pitch is +5, 

 that the front pitch is +5, and that the commutator pitch is 

 also + 5. The resultant pitch is 



f =$ 4-5 = 10 

 and the average pitch is 



y m = ( s + s )/2 = 5 



Figs. 54 and 5 5 show a /b&r-pole winding, and it may be seen 

 that starting from commutator segment No. I we come to the 

 next commutator segment No. 2, after passing through two con- 

 secutive elements of the winding. Any wave winding which 

 brings one from a given commutator segment to an adjacent seg- 

 ment after passing through pJ2 winding elements, where p is the 

 number of field magnet poles for which the winding is made, is 

 called a simplex or single wave winding. 



In what is called a duplex or double wave winding, pJ2 winding 

 elements lead from a given commutator segment to the next seg- 

 ment but one ; in what is called a triplex or triple wave winding, 

 pJ2 winding elements lead from a given commutator segment 

 to the third following segment, and so on. 



47, Reentrancy. A winding which closes on itself, i. e. t forms 

 a closed (or complete) electrical circuit, is called a closed coil 

 winding ; and because such a closed coil winding reenters itself, 

 it is called a reentrant winding. 



Armature windings may be singly, doubly, triply, or in gen- 

 eral, multiply reentrant. The number of times a winding reen- 

 ters, is called the degree of reentrancy. A singly reentrant 

 winding is one in which if one starts at inductor No. I and 

 traces through the successive inductors in the order of winding, 

 the whole winding has to be traced through before conductor 

 No. I is reached or reentered. 



