THE INDUCTION MOTOR. 



(7) -^- = ~' 2 



r r, 



r, signifying the internal and external resistance of the secondary of 

 the transformer. Under this condition the same diagram represents the 

 currents in size and phase in the transformer as well as in the motor. 

 That this must be so becomes clear as soon as we remember that the 

 impedance of the motor is equal to V V 2 3 -f- A (~ x ~ 2 ) *, A being 

 a constant. The impedance of the transformer is equal to 



Vr* + A . ~! 2 , 

 hence 



~i r i = (~i ~a) r > 



which equation is identical with (7). Credit is due to Dr. Behn- 

 Eschenburg, Oerlikon, for having first prominently put forth this 

 relation. 



25. The Torque. Imagine the armature to be turned against the 

 magnetic field, which is supposed to stand still, with an angular velocity 

 equal to ^ 2 - If D is the torque in mkg, then we have 



9.81 . D . (! ,) = 3 z 2 * r,, 

 it being the current in, and r t the resistance of, each phase. 



We have 



' p ' 



if /> is the number of north or south poles. And also 



9.81 . D . u 2 = P watts. 

 From these equations follows 



9.81 . D mkg .(27T. -^ w 2 ) = 3 z 2 . 



9.81 . 2 n . D mk s -^p P 3 *2 * 

 16 



