THREE PHASE INDUCTION MOTORS QUIZ

The power factor of an induction motor under no load conditions will be closer to

0.2 leading

Unity

0.2 lagging

0.5 leading

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A 3 phase induction motor is running at 2% slip. If the input to rotor is 1000 W, then mechanical power developed by the motor is _______

20 W

980 W

500 W

200 W

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In an induction motor if air gap increased

Bearing friction will reduce

The power factor will be low

Windage losses will be more

Copper loss will reduce

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5 H.P., 50Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest?

2880 rpm

1000 rpm

1440 rpm

730 rpm

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The starting torque of a squirrel cage induction motor is

Negligible

Slightly more than full load torque

Low

Same as full load torque

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The frame of an induction motor is usually made of

Aluminium

Silicon steel

Bronze

Cast iron

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If an induction motor is running at slip S, then rotor output is ______

(S-1) × rotor input

(1+S) × rotor input

(1-S) × rotor input

S × rotor input

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At no load the rotor core loss of a 3 phase induction motor is

Small

Practically zero

Large

None of the listed here

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The condition of induction motor on load resemble those of a transformer whose secondady is _______

Supplying a variable resistive load

Short circuited

None of the listed here

Open circuited

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A high starting torque can be obtained in a 3phase induction motor by _______

None of the listed here

Decreasing rotor resistance

Increasing rotor resistance

Increasing rotor reactance

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