Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

A. High field current
B. Low short circuit ratio
C. High core losses
D. Low field current

A rotory converter can also be run as a___________?

A. d.c. shunt motor
B. d.c. series motor
C. d.c. compound motor
D. induction motor

In which of the following motors the stator and rotor fields rotate simultaneously?

A. D.c. motor
B. Reluctance motor
C. Universal motor
D. Synchronous motor

If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then

A. It runs at a slower speed
B. The motor stops
C. It continues to run at the same speed
D. It runs at a very high speed

A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because

A. Speed of the motor is reduced
B. Power factor is decreased
C. Eb (back e.m.f.) becomes less than v (applied voltage)
D. Er (net resultant voltage) in armature is increased

If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor

A. Will become more
B. Will become less
C. Will remain unchanged
D. None of the above.

Stability of a synchronous machine:

A. Decreases with increase in its excitation
B. Increases with increase in its excitation
C. Remains unaffected with increase in excitation
D. Any of the above

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.

While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by_____________?

A. induction motor torque in field winding
B. induction motor torque in damper winding
C. eddy current and hysteresis torque in pole faces
D. rehetance motor torque due to saliency of the rotor

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will___________?

A. Remain same
B. Go down
C. Improve
D. None of the above