156 TREATISE ON ALTERNATING CURRENTS. 



Again, the E.M.F. induced in each stator circuit due to the 

 rotating field is given by 



tii = Nie (10) 



Also, the current i\ in the stator circuit consists of two parts, 

 the function of one part, i\, being to excite the stator and produce 

 the rotating field, and that of the other part, i'\, to transmit energy 

 to the rotor. 



But 



which, by (8) 



The power transmitted per circuit to the rotor is, therefore, the 

 scalar product of the vectors 



- NIC 

 and 



" Ni(rf 4- 

 that is 



Power transmitted to rotor =' . . (12) 



?*2 + *V 



The output, P, of the motor is then obtained by subtracting 

 (9) from (12). That is 



r= KX& 



- K) 



To find the torque, T, exerted per rotor circuit, we must divide 

 P by the angular velocity 0)2, but 



therefore 

 that is 



(14) 



