INDUCTION MOTORS 89 



so that the terminal voltage is 6400 volts at all loads. The 

 speed of the induction generator is adjusted so that when the 

 synchronous machine is delivering no power the load on the 

 induction generator is 500 kw. What is the division of the load 

 when 3500 kw. is required? What is the frequency at this 

 time At what speed should the induction generator be driven 

 so that both will deliver their rated loads, viz., 2000 kw., at the 

 same time? 



72. A 500-kw., 3-phase induction generator is operated with 

 a synchronous motor floated across its terminals.. At no load, 

 when running as an induction motor, it takes a line current of 31 

 amperes at 2000 volts. The resistance of the rotor winding be- 

 tween terminals is 0.0228 ohm, and the ratio of transformation 

 from stator to rotor is 16 to 5. Neglect the resistance and 

 reactance of the stator and the reactance of the rotor windings 

 of the induction generator, and all of the losses in both machines. 

 The excitation of the synchronous motor is adjusted so that the 

 terminal voltage is 2000 volts. The load supplied by these 

 machines is 450 kw. at a power factor of 85 per cent. What is 

 the line current supplied by the induction generator? What is 

 the frequency of this system if the induction generator is 

 wound for 44 poles and is driven at 165 rev. per min.? If the 

 synchronous motor has a synchronous reactance of 6.2 ohms 

 between terminals what is its necessary excitation voltage? 



73. An induction generator supplies power to a load and to 

 an over-excited synchronous motor. At no load as an induction 

 motor it takes a line current of 98 amperes at 2200 volts. The 

 resistance of the rotor winding between terminals i< 0.058 ohm 

 and the ratio of transformation from stator to rotor is 22 to 15. 

 Neglect the resistance and reactance of the stator winding and 

 the reactance of the rotor winding of the induction generator 

 and all of its The rotational losses of the synchronous 

 motor are 23.3 kw. and the resistance and synchronous reactance 

 are respectively 0.26 ohm and 3.04 ohm between terminals. 

 The induction tor delivers 1150 kw. of which the syn- 

 chronous motor receives 450 kw. The excitation of the latter 

 is adjusted so that the terminal voltage is 2200 volts. The power 

 factor of the load exclusive of the synchronous motor is 0.83. 

 The indu< aerator is wound for 12 poles and is dri\- 



a -peed of 254 rev. per min. 



What is the frequency of the system. At what power fa -tor 



