INDUCTION MOTORS 



83 



reactance of the stator winding are 0.342 ohm and 1.08 ohms re- 

 spectively. The ohmic resistance and leakage inductance of the 

 rotor winding referred to the stator are 0.141 ohm and 5.1 rail- 

 In -nr vs. The motor is wound for 24 poles and both the stator and 

 rotor windings are connected in delta. At no load the motor 

 takes a line current of 39.4 amperes and absorbs 6680 watts when 

 the impressed voltage has its rated value. The friction and wind- 

 age loss is 4.0 kw. 



If the air-gap flux is assumed to be constant the maximum 

 torque occurs when the slip equals the ratio of the resistance of the 

 rotor winding to its leakage reactance at the rated frequency. 

 In this case how much must the impressed voltage be increased 

 in order that the air-gap flux will have its no-load value when the 

 torque is a maximum.' 



51. ' What are the power factor, the output, and the efficiency 

 of the induction motor No. F when the slip is 1.55 per cent 

 and the voltage generated by the air-gap flux in the stator wind- 

 - 2060 volts? Assume that the ratios of effective to oh i me 

 resistance are respectively 1.1 and 1.20 for the stator and rotor 

 windings and that the leakage reactances are equal when reduced 

 to the same side. 



52. ' What are the slip, the power factor, and the HIieienev 

 of the induetioii motor No. G when it delivers full load and the 



1 Use the transformer diagram in the solution of this problem. 



