290 ELEMENTS OF ELECTRICAL ENGINEERING. 



represents the effect of magnetic leakage, R f is the resistance of 

 one phase of the stator winding, E r is the voltage acting on one 

 stator winding, the circuit r^ represents the effect of magnetiz- 

 ing current (the resistance r v and the reactance x^ being such 

 that the current in the circuit r^ is equal to the actual mag- 

 netizing current M\ R" is the equivalent resistance of the rotor 

 per stator circuit. Let A represent the voltage across ab, Fig. 

 250, then from the figure we have, using complex-quantity 

 notation, 



Tt 

 1 =jjT, 00 



E' = A + (M+ /') (R r +JX) (iii) 



Furthermore, the total power delivered to the rotor per stator 

 phase is (R" /s)f f2 , the electrical power developed in the rotor 

 per stator phase is R"I f , and the mechanical power developed 

 in the rotor per stator phase is the difference between (R 11 js)P 

 and R"l' z . Therefore the total mechanical power developed in 

 the rotor is 



P. l -~-K>I>"-q (iv) 



in which q is the number of stator phases, and P is the total 

 mechanical power in watts developed by the motor. (The letter 

 P has been also used for magnetic leakage inductance.) 



The torque T which is developed by the motor produces the 

 power P (expressed, in watts of course) at the actual rotor speed 

 n' , and is convenient to express the value of the torque in 

 terms of the power (Px )/' which the same value of torque 

 would produce at synchronous speed n. That is we may 



write n i 



T =tf' PiS T=~s' P (v) 



This equation expresses torque in "synchronous watts." 



