If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to
A. increase in both armature current and power factor angle
B. increase in back e.m.f. but decrease in armature current
C. increase in both armature current and power factor which is lagging
D. increase in torque angle but decrease in back e.m.f.
Answer: Option A
The maximum power developed in a synchronous motor occurs at a coupling angle of
A. 30°
B. 60°
C. 90°
D. 180°
A. remains same as the original value
B. decreases to half the original value
C. tends to becomes zero
D. increases to two times the original value
The speed of a synchronous motor
A. increases as the load increases
B. decreases as the load decreases
C. always remains constant
D. none of the above
In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
A. Universal motor
B. Synchronous motor
C. Induction motor
D. Reluctance motor
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