THE LEAKAGE FACTOR. 



ductors must be proportional to the number of poles ; in other words, 

 if the eight-pole motor has, for instance, 720 conductors, or ten con- 

 ductors in each of 72 slots, then the four-pole motor must have 360, 

 and the two-pole motor 180, in order to get the same induction in 

 the air-gap. To calculate the relative value of the magnetizing cur- 

 rent we need only know the number of active conductors per pole, 



720 

 see equation (6). We have for n in the eight-pole motor s- = 90; 



360 



^i 



180 



in the four- pole motor = =90; and in the two-pole motor = 90. 

 4 2 . 



Hence, as ($> and n are the same in each of the three cases, it 



follows that the magnetizing current also remains the same. As the 



Two Poles 



FIG. 20. 



shape and size of the slots are the same in all three cases, the factor 

 in equation (12) for the leakage coefficient also remains the same. 

 Hence, as the leakage factor is proportional to the quotient of the air- 

 gap divided by the pole-pitch, we find the short-circuit current to 

 be inversely proportional to the number of poles. This is graphically 

 represented in Fig. 20. A glance at the diagram teaches us that the 

 maximum energy that can be impressed upon the motor, and, there- 



37 



