SHORT-CIRCUIT CURRENT AND LEAKAGE FACTOR. 



the total e. m. f., induced in the 100 conductors by the 5 leakage fields, 

 is proportional to 20 X 20 X 5 = 2000. 



33. Now, let us arrange the 100 conductors in 10 slots. Each slot, 

 then, contains 10 conductors, the leakage field per slot being propor- 

 tional to 10. The e. m. f. induced by the leakage field in the 10 con- 

 ductors in each slot is proportional to 10 times 10. Hence the total 

 e. m. f. induced in all the conductors in the 10 slots is proportional to 

 10 X 10 X 10 = looo. In other words, the counter e. m. f. of leakage 

 is twice as large in the case of 5 slots as in the case of 10 slots. 



The above calculation rests upon the assumption that the reluctance 

 of the leakage path of each slot is the same in the two cases under 

 consideration. Though this is true only with some qualifications, yet 

 the argument clearly shows the superiority of many over few slots, as 

 far as leakage is concerned. 



34. A general rule for the most favorable number of slots can hardly 

 be given. To take more than 5 slots per pole and phase in the field is 



FIG. 12. 



hardly advisable unless the pole-pitch be very large, as in motors for 

 low frequencies. As the maximum of ampere-conductors per slot 600 



23 



