84 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



voltage generated in the stator winding by the air-gap flux is 

 the same as at no load? 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 equal to the ratio of the effective 

 resistances. 



53. l What are the power factor, the torque and the efficiency 

 of the induction motor No. H when the slip is 1.86 per cent., and 

 the voltage generated by the air-gap flux in the stator winding 

 is 93 per cent, of the rated impressed voltage? Assume that 

 the ratios of effective to ohmic resistance are the same for the 

 stator and rotor windings at 25 C., 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. 



54. l What are the power factor, the slip, and the efficiency 

 of the induction motor No. / when it delivers a torque of 22,000 

 pound-feet, and the voltage generated by the air-gap flux in 

 the stator winding is 2040 volts? Assume that the ratios of 

 the ohmic resistance, 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 tempera- 

 ture is 70 C. 



55. l What are the power factor, the slip, and the efficiency 

 when the induction motor No. J delivers 2750 h.p. and the 

 voltage generated by the air-gap flux in the stator winding is 

 92 per cent, of the rated impressed voltage? Assume that the 

 ratio of the effective to the ohmic resistance of the rotor is 

 20 per cent, greater than for the stator, and that the ratios 

 of the leakage reactances and of the effective resistances are 

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

 running temperature is 70 C. 



56. What are the power factor, the torque and the efficiency 

 for the induction motor No. / when the slip is 1.6 per cent, 

 and the impressed voltage has its rated value? Make the same 

 assumptions in regard to the resistances and reactances as were 

 made in problem 54. 



57. What are the power factor, the slip and the efficiency 

 when the induction motor No. J delivers a torque ^of 164,000 

 pound-feet and the impressed voltage is 6400 volts? Make 



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



