SWITCH GEAR QUIZ

The speed of a squirrel-cage induction motor can be controlled by all of the following except

Reducing supply voltage

Changing winding resistance

Changing supply frequency

Changing number of poles

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If any two phases for an induction motor are interchanged

The motor will not run

The motor will run at reduced speed

The motor will run in reverse direction

The motor will burn

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Insertion of resistance in the rotor of an induction motor to develop a given torque

Decreases the rotor current

Rotor current remains same

Rotor current becomes zero

Increases the rotor current

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

Short circuited

None of the listed here

Open circuited

Supplying a variable resistive load

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

No load current is decreased

Leakage reactances are increased

None of the listed here

Leakage reactances are decreased

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The complete circle diagram of induction motor can be drawn with the help of data found from

Stator resistance test

All of these

Blocked rotor test

No-load test

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When the rotor of a 3-phase induction motor is blocked, the slip is _____

0.1

0.5

1

0

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The advantage of wound rotor motor is that _______

External resistance can be inserted in the rotor circuit

None of the listed here

It is inexpensive

It requires less maintenance

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In an induction motor, the ratio of rotor cu loss and rotor input is given by

S/1-S

S

1/S

1-S

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The good power factor of an induction motor can be achieved if the average flux density in the air gap is

Absent

Large

Small

Infinity

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