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Polyphase Induction Motors - section-1
  1. The purpose of using short-circuit gear is

    2. A.

     To short circuit the rotor at slip rings
    B.

     To short circuit the starting resistances in the starter
    C.

     To short circuit the stator phase of motor to form star
    D.

     None of the above

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  2. Insertion of reactance in the rotor circuit

    3. A.

     Reduces starting torque as well as maximum torque
    B.

     Increases starting torque as well as maximum torque
    C.

     Increases starting torque but maximum torque remains unchanged
    D.

     Increases starting torque but maximum torque decreases

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  3. The maximum torque in an induction motor depends on

    4. A.

     Frequency
    B.

     Rotor inductive reactance
    C.

     Square of supply voltage
    D.

     All of the above

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  4. The shaft of an induction motor is made of

    5. A.

     High speed steel
    B.

     Stainless steel
    C.

     Carbon steel
    D.

     Cast iron

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  5. The number of slip rings on a squirrel cage induction motor is usually

    6. A.

     Two
    B.

     Three
    C.

     Four
    D.

     None

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  6. A squirrel cage induction motor is not selected when

    7. A.

     Initial cost is the main consideration
    B.

     Maintenance cost is to be kept low
    C.

     Higher starting torque is the main consideration
    D.

     All above considerations are involved

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  7. Slip ring motor is recommended where

    8. A.

     Speed control is required
    B.

     Frequent starting, stopping and reversing is required
    C.

     High starting torque is needed
    D.

     All above features are required

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  8. If a 3-phase supply is given to the stator and rotor is short circuited rotor will move

    9. A.

     In the opposite direction as the direction of the rotating field
    B.

     In the same direction as the direction of the field
    C.

     In any direction depending upon phase sequence of supply
    D.

     None of these

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  9. Lubricant used for ball bearing is usually

    10. A.

     Graphite
    B.

     Grease
    C.

     Mineral oil
    D.

     Molasses

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  10. For which motor the speed can be controlled from rotor side?

    11. A.

     Squirrel-cage induction motor
    B.

     Slip-ring induction motor
    C.

     Both (A) and (B)
    D.

     None of the above

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