1. Slip-rings in a synchronous motor carry ?

direct current

alternating current

no current

all of the above

Answer: direct current


2. If the field circuit of an unloaded salient pole synchronous motor gets suddenly open-circuited, then ?

it runs at a slower speed

the motor stops

it continues to run at the same speed

it runs at a very high speed

Answer: the motor stops


3. Which of the following motors is non self starting ?

D.C. series motor

Synchronous motor

Squirrel cage induction motor

Wound round induction motor

Answer: Synchronous motor


4. Which of the following losses, in a synchronous motor, does not vary with load ?

Windage loss

Copper losses

Any of the above

None of the above

Answer: Windage loss


5. Asynchronous motor which works on a leading power factor and does not drive a mechanical load is called as ?

static condenser


synchronous condenser

none of the above

Answer: synchronous condenser


6. The angle between the rotor poles and stator poles, in a synchronous motor, is known as ?

power factor angle

torque angle

synchronizing angle

angle of retardation

Answer: torque angle


7. The coupling angle or load angle of synchronous motor is defined as the angle between the ?

rotor and stator teeth

rotor and the stator poles of opposite polarity

rotor and the stator poles of the same polarity

none of the above

Answer: rotor and the stator poles of opposite polarity


8. The construction of a synchronous motor resembles ?

a series motor

an induction motor

an alternator

a rotary converter

Answer: an alternator


9. By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?

By changing the supply frequency

By interchanging any two phases

By changing the applied voltage

By changing the load

Answer: By changing the supply frequency


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

load on the motor

d.c. excitation only

both the speed and rotor flux

none of the above

Answer: d.c. excitation only