CHAPTER III 

 SYNCHRONOUS MOTORS 



1. A 3-phase, 60-cycle, A-connected alternating-current 

 generator is rated to deliver 15 kv.-a. at 230 volts. The field 

 structure has 6 poles each of which is wound with 398 turns. 

 The armature core has 4 slots per pole per phase with 8 inductors 

 in series per slot. Each inductor is 5 in. long. The hot resist- 

 ance of the armature measured between any two terminals is 

 0.126 ohm. The effective resistance is 1.6 times the ohmic 

 resistance. In calculating the leakage reactance assume 8 

 leakage lines per ampere per inch of inductor. The open- and 

 short-circuit characteristics are given by the following data: 



This generator is running as an overexcited synchronous motor 

 and receives 15 kw. at its rated voltage and 0.8 power factor. 



(a) Calculate the field current by the general method. 



(b) Calculate the field current by the synchronous-impedance 

 method. 



(c) Calculate the field current by the magnetomotive-force 

 method. 



2. A 3-phase, 5000-volt, 25-cycle synchronous motor has a 

 full-load capacity of 1100 h.p. The field structure consists of 32 

 poles each of which is wound with 79.5 turns. The armature 

 core has 192 slots with 14 inductors in series per slot. The 

 armature winding is Y-connected. The effective resistance of 

 the armature winding is 0.38 ohm per phase. In calculating the 

 leakage reactance, assume 75 leakage lines per ampere per 

 inductor. The open- and short-circuit characteristics are given 

 by the following data: 



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