SYNCHRONOUS MOTORS 



53 



This motor receives 760 kw. at its rated voltage and 0.83 power 

 factor. The excitation is less than normal. 



(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. 



3. A 3-phase, 5500-volt, 50-cycle synchronous motor has a 

 full-load capacity of 2000 h.p. The field structure has 72 

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

 has one slot per pole per phase with 12 inductors per slot. The 

 armature winding is connected in Y. The armature resistance 

 measured between any two terminals is 0.536 ohm, and the ratio 

 of effective to ohmic resistance is 1.35. In calculating the 

 leakage reactance assume 67 leakage lines per inductor per 

 ampere. The data for the open- and short-circuit characteristics 

 are: 



This motor receives 960 kw. at its rated voltage and 0.68 power 

 factor. The excitation is greater than normal. 



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



Calculate the field current by the synchronous-! in pe< lance 

 method. 



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

 method. 



4. A :i 'JOO-volt, 50-cycle synchronous motor is rated 



to deliver 1000 h.p. when operating at unit power factor. The 



