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Polyphase Induction Motors - section-1
  1. 5 H.P., 50Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest?

    2. A.

     730 r.p.m.
    B.

     960 r.p.m.
    C.

     1440 r.p.m.
    D.

     2880 r.p.m.

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  2. In the squirrel-cage induction motor the rotor slots are usually given slight skew

    3. A.

     To reduce the magnetic hum and locking tendency of the rotor
    B.

     To increase the tensile strength of the rotor bars
    C.

     To ensure easy fabrication
    D.

     None of the above

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  3. Temperature of the stator winding of a three phase induction motor is obtained by

    4. A.

     Resistance rise method
    B.

     Thermometer method
    C.

     Embedded temperature method
    D.

     All above methods

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  4. In case of the induction motors the torque is

    5. A.

     Inversely proportional to (V-slip)
    B.

     Directly proportional to (slip)2
    C.

     Inversely proportional to slip
    D.

     Directly proportional to slip

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  5. An induction motor is

    6. A.

     Self-starting with zero torque
    B.

     Self-starting with high torque
    C.

     Self-starting with low torque
    D.

     Non-self starting

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  6. The torque of an induction motor is

    7. A.

     Directly proportional to slip
    B.

     Inversely proportional to slip
    C.

     Proportional to the square of the slip
    D.

     None of the above

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  7. The 'crawling' in an induction motor is caused by

    8. A.

     High loads
    B.

     Low voltage supply
    C.

     Improper design of machine
    D.

     Harmonics developed in the motor

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  8. The crawling in the induction motor is caused by

    9. A.

     Low voltage supply
    B.

     High loads
    C.

     Harmonics developed in the motor
    D.

     Improper design of the machine

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  9. In case the air gap in an induction motor is increased

    10. A.

     The magnetizing current of the rotor will decrease
    B.

     The power factor will decrease
    C.

     Speed of motor will increase
    D.

     The windage losses will increase

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  10. For driving high inertia loads best type of induction motor suggested is

    11. A.

     Slip ring type
    B.

     Squirrel-cage type
    C.

     Any of the above
    D.

     None of the above

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