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Polyphase Induction Motors - section-1
  1. Which is of the following data is required to draw the circle diagram for an induction motor?

    2. A.

     Block rotor test only
    B.

     No load test only
    C.

     Block rotor test and no-load test
    D.

     Block rotor test, no-load test and stator resistance test

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  2. Slip rings are usually made of

    3. A.

     Copper
    B.

     Carbon
    C.

     Phosphor bronze
    D.

     Aluminium

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  3. The starting torque of a three phase induction motor can be increased by

    4. A.

     Increasing slip
    B.

     Increasing current
    C.

     Both (A) and (B)
    D.

     None of the above

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  4. Rotor rheostat control method of speed control is used for

    5. A.

     Squirrel-cage induction motors only
    B.

     Slip ring induction motors only
    C.

     Both (A) and (B)
    D.

     None of the above

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  5. The stating torque of the slip ring induction motor can be increased by adding

    6. A.

     External inductance to the rotor
    B.

     External resistance to the rotor
    C.

     External capacitance to the rotor
    D.

     Both resistance and inductance to rotor

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  6. A double squirrel-cage induction motor has

    7. A.

     Two rotors moving in opposite direction
    B.

     Two parallel windings in stator
    C.

     Two parallel windings in rotor
    D.

     Two series windings in stator

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  7. The term 'cogging' is associated with

    8. A.

     Three-phase transformers
    B.

     Compound generators
    C.

     D.C. series motors
    D.

     Induction motors

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  8. In medium sized induction motors, the slip is generally around

    9. A.

     0.04 %
    B.

     0.4 %
    C.

     4 %
    D.

     14 %

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  9. Blocked rotor test on induction motors is used to find out

    10. A.

     Leakage reactance
    B.

     Power factor on short circuit
    C.

     Short-circuit current under rated voltage
    D.

     All of the above

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  10. A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor

    11. A.

     Will continue running burning its one phase
    B.

     Will continue running burning its two phases
    C.

     Will stop and carry heavy current causing permanent damage to its winding
    D.

     Will continue running without any harm to the winding

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