ARMATURE WINDINGS. 435 



front and back pitches would connect both terminals of a wind- 

 ing element to the same commutator segment. 



(c) In simplex lap windings front and back pitches differ by 2, 

 so that the average pitch is an even number, and the commutator 

 pitch is i. 



(rf) In a multiplex lap winding front and back pitches differ by 

 2m where m is the number of component simplex windings, and 

 the commutator pitch is m. 



(e) The total number of inductors Z may be any even num- 

 ber, except in case of slotted armature cores, in which case Z 

 must be a multiple of the number of slots. (The number of 

 slots may be even or odd.) 



Wave windings. (a) Front and back pitches are alike in sign. 



(&) Front and back pitches may be equal or they may differ 

 by any multiple of 2. When one pitch, the front pitch for ex- 

 ample, is made considerably greater than Zjp then the other 

 pitch must be made considerably smaller than Zjp. The average 

 pitch of a wave winding is always very nearly equal to Zip 

 according to (c). 



(c) In simplex wave windings / x average pitch must be equal 

 to Z 2. Therefore 



in which y av is the average pitch. 

 (d) In multiplex wave windings 



Z=py m 2m 



in which m is the number of component simplex windings. 

 In the following table 



/ = number of field magnet poles. 

 Z = number of armature inductors. 

 y = average pitch of winding. 

 K= number of commutator segments. 



For detailed treatment of armature windings see E. Arnold's 

 Die GleicJistrommaschine , Vol. I., Julius Springer, Berlin, 1902 ; 

 and Parshall and Hobart's Armature Windings, D. Van Nostrand 

 Co., New York, 1895. 



