POLYPHASE CIRCUITS 1 17 



59. A 1000-kw., 11,000-volt, 3-phase generator delivers power 

 to a transmission line at the end of which is a 1200-h.p. induction 

 motor. With the induction motor running at no load the exci- 

 tation of the generator is adjusted so that the terminal voltage, 

 the line current and the total power measured at the motor are 

 10,600 volts, 20.2 amperes and 20.4 kilowatts respectively. At 

 the same time the terminal voltage and the total power measured 

 at the generator are 10,980 volts and 29.8 kw. The field excita- 

 tion of the generator is adjusted so that, when the mo tor is deliver- 

 ing full load, its terminal voltage is 11,000 volts. The efficiency 

 and power factor of the motor at full load are 0.921 and 0.906 



actively. 



What is the terminal voltage of the generator when the motor 

 delivers full load? What is the efficiency of transmission at this 

 time? 



60. A l()()()-k\v., 13,800-volt, 3-phase generator delivers power 

 directly to a transmission line at the end of which is an induction 

 motor load. The resistance and reactance of the tran<ini i.n 

 line are 16.8 ohms and 17. 2 ohms per conductor. The generator 

 has an effective armature reactance of 2.18 ohms per phase. The 

 field current is supplied at 120 volts. 



On open circuit the rotational losse* are hi.ii kw. and 25.4 kw. 

 when the terminal voltages are 13,000 and 15,600 volts respec- 

 tively. 



What >hould le the field exeitation of the general. >r so 

 that the line voltage at the motor load will l.e lil.'joo v<.lt< when 

 the moton take 928 kw. at o.\>\ power factor? What is the ,-ifi- 

 eimcy of the generator and the lin< '.' 



61. At the mil of a ii-phase t raiiMni>sioM line U ;t motor load 



rnjuirinnSOOOkw. The line voltage at the load should he 32,000 



md the power factor of the load What should \n> 



1 Tin' K<-nerator is Y-connected. 



