36 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



(b) Calculate the regulation of this generator for the specified 

 load by the synchronous impedance method. What is the field 

 current calculated by this method? 



(c) Calculate the regulation of this generator for the specified 

 load by the magnetomotive force method. What is the field 

 current calculated by this method? 



53. A 3-phase, Y-connected, 1500-kv.-a., 5500-volt alternating- 

 current generator is driven by a 2000-h.p. reciprocating engine 

 that runs at 83 rev. per min. at full load. The field structure 

 has 72 poles each of which is wound with 35 turns. The armature 

 core has 1 slot per pole per phase with 12 inductors in series per 

 slot. Each inductor is 9 in. long. The armature winding has 

 an effective resistance of 0.36 ohm per phase. In calculating 

 the leakage reactance assume 7.5 equivalent leakage lines per 

 ampere per inch of inductor. The data for the open- and short- 

 circuit characteristics are: 



(a) Calculate the regulation of this generator by the general 

 method for 20 per cent, overload current at 0.85 power factor 

 (induction load). What is the field current calculated by this 

 method? 



(b) Calculate the regulation of this generator for the specified 

 load by the synchronous impedance method. What is the field 

 current calculated by this method? 



(c) Calculate the regulation of this generator for the specified 

 load by the magnetomotive force method. What is the field 

 current calculated by this method? 



54. A 3750-kv.-a. alternating-current generator delivers energy 

 at 2200 volts to a 2-phase, 30-cycle system. The field structure 

 has 20 poles, each of which is wound with 60 turns. The arma- 

 ture has 360 slots with one inductor per slot. Each inductor is 

 20.5 in. long. The armature resistance by direct-current measure- 

 ment is 0.0196 ohm per phase at 25 C. Assume that the ratio 

 of effective resistance to ohmic resistance is 1.3 at 25 C. In 



