THREE PHASE INDUCTION MOTORS QUIZ

A 3 phase 440 v, 50 Hz induction motor has 4% slip. The frequency of rotor emf will be

50 Hz

2 Hz

20 Hz

200 Hz

TRUE ANSWER : ?
YOUR ANSWER : ?

In a squirrel cage induction motor, the number of rotor bars is generally ________

Even number

Prime number

None of the listed here

Equal to stator poles

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For the same kVA rating, the leakage flux in induction motor is _______ that of transformer.

More than

None of the listed here

Less than

About the same

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The rotor of an induction motor runs at

Above synchronous speed

Any of the above

Below synchronous speed

Synchronous speed

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If the air gap between the rotor and stator of a 3-phase induction motor is increased, then_______

None of the listed here

Leakage reactances are decreased

No load current is decreased

Leakage reactances are increased

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A wound rotor motor is mainly used in applications where ______

Less costly motor is not required

Speed control is required

High rotor resistance is required during running

High starting torque is required

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The term cogging is associated with

Induction motors

Compound generators

Three phase transformer

Dc series motors

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Reduced voltage starter can be used with

Squirrel cage induction motor only but not with slip ring motor

None of these

Squirrel cage as well as slip ring induction motor

Slip ring motor only but not with squirrel cage induction motor

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For higher efficiency of 3-phase induction motor, the slip should be

As small as possible

Large

Very large

1

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The approximate efficiency of a 3-phase , 50 Hz, 4 pole induction motor running at 1350 rpm is ______

None of the listed here

65%

40%

90%

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