120 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



resistance of 16.4 ohms and a reactance of 17.2 ohms per con- 

 ductor to a 1340-h.p. synchronous motor. Both generator and 

 motor have their armatures connected in Y. This motor is 

 rated for 11,000 volts and has an effective armature resistance of 

 0.94 ohms and a synchronous reactance of 46 ohms per phase. 

 The effective resistance and synchronous reactance of the 

 generator are respectively 2.18 ohms, and 82 ohms per phase. 

 The rotation losses of the motor are 22 kw. and may be assumed 

 constant. For certain excitations of generator and motor the 

 line current and power factor at the motor are respectively 48 

 amperes and 0.92 (lagging) when the motor delivers 1140 h.p. 



If the excitations are unchanged what will be the line current 

 and the terminal voltages of the generator and motor if the load 

 on the motor is thrown off? 



67. A 1500-kv.-a., 5500-volt alternator delivers energy to 

 a high-tension transmission line through step-up transformers, 

 the low-tension windings of which are connected in delta and the 

 high-tension windings in Y. The neutrals of the generator and of 

 the high-tension transformer windings are grounded. The 

 transformers have a ratio of transformation of 6.3 to 1.0. 



GENERATOR CHARACTERISTICS 



The effective resistance of the armature is 0.36 ohm per phase. 

 The resistance of the field circuit is 0.386 ohm. The power 

 required to drive the generator on open circuit with a terminal 

 voltage of 5500 volts is 28.6 kw. 



TRANSFORMER CHARACTERISTICS 



With the high-tension winding short-circuited and 170 volts 

 impressed on the low-tension winding the current supplied to a 

 transformer is 91 amperes and the power is 4.26 kw. At no load 

 and with 5500 volts impressed on the low-tension winding the 

 power is 3.12 kw. 



With a balanced load of 1360 kw. at 0.83 power factor delivered 



