90 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



is the synchronous motor operating? What is the excitation 

 voltage of the synchronous motor? What is the power output 

 of the synchronous motor? 



74. A 2000-kw. induction generator is operated in parallel 

 with a synchronous generator of the same capacity. At no load, 

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

 90 amperes at 6400 volts. The resistance of the rotor winding 

 between terminals is 0.0766 ohm and the ratio of transformation 

 from stator to rotor is 6400 to 2076. Neglect the resistance 

 and reactance of the stator and the reactance of the rotor winding 

 and all of its losses. The resistance and synchronous reactance 

 of the synchronous generator between terminals are respectively 

 0.65 ohm and 14.2 ohms. The induction generator delivers 

 1800 kw. and the synchronous generator 1200 kw. The excita- 

 tion of the latter is adjusted so that the terminal voltage is 6400 

 volts, and the power factor of the load is 0.85. The induction 

 generator is wound for 36 poles and is driven at a speed of 82.4 

 rev. per min. 



What is the frequency of the system? At what power factor 

 does the synchronous generator operate? What is the excita- 

 tion voltage of the synchronous generator? 



75. An induction generator and a synchronous generator are 

 operated in parallel and supply a load of 700 kw. at 0.86 power 

 factor. Data concerning the induction generator are: 370 kw., 

 2000 volts, 44 poles, Y wound. The rotor resistance is 0.166 

 ohm per phase refered to the stator. The magnetizing current 

 is 23 amperes at the rated voltage, and the core loss is 2.47 kw. 

 Neglect the resistance and reactance of the stator winding. 

 Data concerning the synchronous generator are: 500 kw., 2200 

 volts, 64 poles, Y wound. The effective resistance and synchron- 

 ous reactance of the armature winding are respectively 0.224 

 ohm and 2.76 ohms per phase. The induction generator is 

 driven at 166.4 rev. per min. and the synchronous generator 

 at 113.0 rev. per min. What is the division of the load if the 

 excitation of the synchronous machine is adjusted so that the 

 terminal voltage is 2200 volts? What is the necessary excitation 

 voltage of the synchronous generator? 



76. An induction generator and a synchronous generator are 

 operated in parallel and supply a load of 950 kw. at 0.83 power 

 factor. Data concerning the induction generator are: 450 kw., 

 2000 volts, 36 poles, A wound. The rotor resistance is 0.50 ohm 



