118 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



the resistance and reactance of the line per conductor so that 

 the efficiency of transmission will be 90 per cent, and the voltage 

 regulation, 12 per cent? 



62. A 1640-kv.-a., 13,500-volt, 3-phase generator delivers 

 power directly to a transmission line which has a resistance of 

 30.2 ohms and a reactance of 24 ohms per conductor. With the 

 far end of the line short-circuited and with a field excitation of 150 

 amperes the line current is 138 amperes. With the same field 

 excitation the open-circuit terminal voltage of the generator is 

 14,700 volts. The effective resistance of the armature is 1.52 

 ohms per phase. The generator is Y-connected. 



What is the combined electrical efficiency of the armature of 

 the generator and the transmission line for a load of 1500 kw. 

 at 0.90 power factor if the line voltage at the load is 13,200 volts? 

 To what value will the line voltage rise if this load is removed and 

 the field excitation of the generator is unchanged? 



63. A 1000-kv.-a., 11,000-volt, 3-phase generator delivers 

 power directly to a transmission line which has a resistance of 

 8.42 ohms and a reactance of 6.8 ohms per conductor. 



The armature has an effective resistance of 0.94 ohm per phase, 

 and the windings are connected in Y. The field current is supplied 

 at 260 volts. With the far end of the line short-circuited 

 and with a field current of 40 amperes the line current is 115 

 amperes . 



If the load at the end of the line requires 940 kw. at 0.92 power 

 factor what must be the excitation of the generator in order that 

 the line voltage at the load shall be 11,000 volts? 



64. A 1000-kw., 13,800-volt, 3-phase alternating-current 

 generator delivers power over a transmission line to a synchronous 

 motor load. The resistance and reactance of the line are 16.5 

 and 17.1 ohms per conductor respectively. The armature of 

 the generator has an effective resistance of 2.18 ohms per phase. 

 The field current is supplied with 120 volts. 



