INDUCTION MOTORS % 85 



the same assumptions in regard to the resistances and reactances 

 as were made in problem 55. 



58. What arc the power factor, the slip and the efficiency when 

 the induct im motor No. H delivers 560 h.p. and the impressed 

 voltage has its rated value? Make the same assumption in regard 

 to t he resistances and reactances as were made in problem 53. 



59. Two 3-phase, 220-volt. 60-cycle induction motors are con- 

 nected in concatenation across a 220-volt circuit. Each is rated 

 to deliver 10 h.p. and is wound for 6 poles. What is the no-load 

 >pcc<l? When they deliver 10 h.p. what is the torque developed 

 by each motor? 



60. Two 3-phase. 220-volt. 60-cycle induction motors are con- 

 nc.-tcd in concatenation across a 220-volt circuit. Each is rated 

 to deliver 10 h.p. but one iswound for 6 poles and the other for 

 8 poles. What is the no-load speed? When they deliver 10 h.p. 

 what is the torque developed by each motor? What per cent, 

 of its full-load current does each motor carry? 



61. Two 3-phase, 220-volt, 60-cycle induction motors are con- 

 nected in concatenation across a 220-volt circuit. One is rated 

 to deliver 10 h.p. and the other 15 h.p., but both are wound for 

 6 poles. What is the no-load speed? * What load is delivered 

 when the 15-h.p. motor takes its full-load current? What per 

 cent, of its full-load value is the current in the 10-h.p. motor? 

 What is the torque developed by each? 



62. Two 3-phase, 220 volt 60-cycle induction motors are con- 

 nected in concatenation across a 220-volt circuit. One is rated 

 to deliver 10 h.p. and is wound for 6 poles, and the other is rated 

 to deliver 15 h.p. and is wound for 4 poles. What is the no-load 

 speed? What is the greatest load that can be delivered and 

 have neither motor take more than its full-load current? When 

 they deliver \?> h.p. what torque does each develop? 



63. The two induction motors, M and P, are connected in 

 concatenation. The stator of the first receives power at its 

 rated voltage and frequency, and the stator of the second i< 

 short -circuited. Neglect the no-load component of the current 

 and the core loss due to the leakage flux. 



(a) What is the total output when the slip of the first motor 

 is 51.3 per oent.? 



What is the power developed by each motor? 



(c) What are the copper losses in the stator and rotor of each 

 motor? 



