426 ELEMENTS OF ELECTRICAL ENGINEERING. 



winding are connected to every third commutator segment, and 

 so on. The interval between the terminals of a winding element, 

 expressed in terms of the number of commutator segments, is 

 called the commutator pitch. Thus in Figs. 5 2 and 5 3 the com- 

 mutator pitch is, let us say, -f i.* In a duplex winding the 

 commutator pitch is 2, plus or minus, in a triplex lap winding 

 the commutator pitch is d= 3, and so on. 



The resultant pitch, y, is the algebraic sum of the front pitch 

 and the back pitch. Thus in Figs. 52 and 53 the resultant pitch 

 is 



5 + (-3) = + 2 



The average pitch is half the arithmetical sum of the front pitch 

 and the back pitch. Thus in Figs. 52 and 53 the average pitch 

 is 



46. Wave winding. Starting at commutator segment No. i 

 in Figs. 54 and 55, if we proceed by front end connection to in- 

 ductor No. i, then along inductor No. I towards the back (or 

 pulley end) of the armature, then across the back (by dotted line 

 in Fig. 54) to inductor No. 6, then along inductor No. 6 towards 

 the front (or commutator end), then by front end connection to 

 commutator segment No. 6, we shall have completed one element 

 of the winding. The next element of the winding is connected 

 similarly from segment No. 6 through inductors No. 1 1 and No. 

 1 6 to segment No. 2 as shown by the heavy lines in Figs. 54 

 and 55. The rest of the winding is merely a repetition of the 

 steps just described for the first two elements of the winding. 



It is evident from Figs. 54 and 55 that two consecutive wind- 

 ing elements have the appearance of two successive waves or 

 zig-zags. This is shown with especial distinctness in Fig. 55. It 



* If front and back pitches are interchanged, the commutator pitch is reversed in 

 sign, that is the first element of the winding (in Figs. 52 and 53) would terminate at 

 segment No. I and segment No. 9. 



