CHAP. XII] 



INDUCTANCE OF WINDINGS 



227 



when the stator tooth-pitch and the rotor tooth-pitch are equal 

 to each other; otherwise the paths become too complicated for 

 mathematical analysis. Since the position of the secondary teeth 

 varies with respect to the primary teeth, the permeance of the 

 zigzag leakage also varies, and it is necessary to take its average 

 value over one-half of the tooth-pitch Jl, that is, between the posi- 

 tions (1) and (2) in Fig. 23. In some intermediate position (Fig. 

 55), determined by the overlap y, the reluctance of the path /, 

 per unit of semi-net axial length of the iron, is a/(fiy) rels. 



i 



Fia. 55. The notation used in the calculation of the slot and zigzag leakage 



Thc> reluctance of the path g is a/p(t 2 s l y) rels. The com- 

 bined reluctance of / and g is equal to the sum of the foregoing 

 expressions. The penm -;m< <>f f and g in series, being the 

 reciprocal of the combined reluctance, is 



The permeance in question varies according to this law, for the 

 positions of the secondary tooth between j/-J(^-*i) and y-0, 

 the tooth moving to the left. From y-0 to y-4(*2 i A) the 

 permeance is practically equal to zero, because the secondary tooth 

 bridges over the primary slot no more. The student is advised 



