In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on___________?

A. Load on the motor
B. D.c. excitation only
C. Both the speed and rotor flux
D. None of the above

Hunting in a synchronous motor cannot be due to___________?

A. Windage friction
B. Variable load
C. Variable frequency
D. Variable supply voltage

A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have_____________?

A. No change of power factor
B. Lagging power factor with over-excitation
C. Leading power factor with under-excitation
D. Leading power factor with over-excitation

A synchronous motor develops maximum power when load angle is____________?

A. 45°
B. 60°
C. 90°
D. 120°

The armature current of the synchronous motor

A. Has large values for low excitation i niy
B. Has large values for high excitation only
C. Has large values for low and high excitation
D. Any of the above

Exciters of synchronous machines are______________?

A. D.c. series machines
B. D.c. shunt machines
C. D.c. compound machines
D. Any of the above

The duration of sudden snort-circuit test on a synchronous motor is usually about_____________?

A. One hour
B. One minute
C. One second
D. None of the above

The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as_____________?

A. Slip torque
B. Pull-out torque
C. Breaking torque
D. Synchronising torque

Which of the following motors is non-self starting ?

A. D.c. series motor
B. Synchronous motor
C. Squirrel cage induction motor
D. Wound round induction motor

The magnitude of field flux in a 3-phase synchronous motor?

A. Varies with power factor
B. Varies with speed
C. Varies with the load
D. Remains constant at all loads