SYNCHRONOUS MOTORS QUIZ

In a 3-phase synchronous motor, the negative phase sequence exists when the motor is

under-loaded

None of these

supplied with unbalanced voltage

over-loaded

TRUE ANSWER : ?
YOUR ANSWER : ?

In a synchronous motor which loss varies with load ?

Core loss

Copper loss

Bearing friction loss

Windage loss

TRUE ANSWER : ?
YOUR ANSWER : ?

While running, a synchronous motor is compelled to run at synchronous speed because of _______

Induced emf in rotor field winding by stator flux

Magnetic locking between stator and rotor poles

Damper winding in its pole faces

Compulsion due to lenz's law

TRUE ANSWER : ?
YOUR ANSWER : ?

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

it continues to run at the same speed

it runs at a very high speed

the motor stops

it runs at a slower speed

TRUE ANSWER : ?
YOUR ANSWER : ?

The pull out torque of a practical synchronous motor will occur when the torque angle is about _____

30°

45°

0°

75°

TRUE ANSWER : ?
YOUR ANSWER : ?

Dust and dirt accumulation on motor winding will result in

Increased core losses

Shorting of coils

Rise in winding temperature

Eddy current flow

TRUE ANSWER : ?
YOUR ANSWER : ?

An under excited synchronous motor behaves as_______

An inductor

A resistor

None of the listed here

A capacitor

TRUE ANSWER : ?
YOUR ANSWER : ?

The efficiency of a properly designed synchronous motor will usually fall in range

75 to 80%

85 to 95%

99 to 99.5%

60 to 70%

TRUE ANSWER : ?
YOUR ANSWER : ?

A synchronous motor can develop synchronous torque

only at synchronous speed

when under loaded

below or above synchronous speed

while over-excited

TRUE ANSWER : ?
YOUR ANSWER : ?

If the field of a synchronous motor is underexcited, the power factor will be

leading

zero

lagging

unity

TRUE ANSWER : ?
YOUR ANSWER : ?

↑