INDUCTION MOTORS 91 



per phase refered to the stator. The magnetizing current is 33 

 amperes per phase and the core loss is 2.8 kw. Neglect the 

 resistance and reactance of the stator winding. Data concern- 

 ing the synchronous generator are: 850 kw., 2000 volts, 32 poles, 

 Y wound. The effective resistance and synchronous reactance 

 are respectively 0.064 ohm and 2.40 ohms per phase. The 

 induction generator is driven at 85.0 rev. per min. and the syn- 

 chronous generator, at 94.0 rev. per min. What is the division 

 of the load if the excitation of the synchronous generator is 

 adjusted so that the terminal voltage is 2000 volts? What is 

 the necessary excitation voltage of the synchronous generator? 



77. 1 The induction motor No. G is operated as a generator on a 

 60-cycle circuit in parallel with synchronous apparatus. What 

 are the slip, the power factor and t he efficiency when it re- 

 ceives 150 h.p. from the prime mover and the voltage generated 

 in the stator winding by the air-gap flux is 460 volts? Assume 

 that the ratios of effective to ohmic resistance are respectively 

 1.4 and 1.6 for the stator and rotor windings, and that the 

 ratio of the leakage reactances at the rated frequency is the same 

 as ratio of the effective resistances. 



78. l The induction motor No. H is operated as a generator on 

 a 2200-volt, 25-cycle circuit in paralled with synchronous appa- 

 ratus. What are the output, the power factor and the efficiency 

 when the slip is 1.86 per cent, and the voltage generated in the 

 stator winding by the air-gap flux is assumed to be 93 per cent, 

 of the terminal voltage? Assume that the ratios of effective to 

 ohmic resistance are the same at 25 Centigrade, and that the 

 ratio of the ohmic resistances is equal to the ratio of the leakage 

 reactances of the two windings at the rated frequency. The 

 temperature under the running condition is 65 C. 



79. * The induction motor No. / is operated as a generator 

 on a 25-cycle circuit in parallel with syncrohnous apparatus. 

 What are the slip, the power factor and the efficiency when it re- 

 ceives 1000 h.p. from the prime mover and the voltage generated 

 in tho stator winding by the air-gap flux is 2040 volts? Assume 

 that the ratios of the ohmic resistances, the effective resistances 

 and the leakage reactances of the stator and rotor windings are 

 equal at the rated frequency and a temperature of 25 C. 

 The running temperature is 70 C. 



80. l The induction motor No. J is operated as a generator 



See page 83. 



