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EEE :: D.C. Motors

  1. Which of the following method of speed control of D.C. machine will offer minimum efficiency?

  2. A.

     Voltage control method

    B.

     Field control method

    C.

     Armature control method

    D.

     All above methods

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  3. A D.C. series motor is that which

  4. A.

     Has its field winding consisting of thick wire and less turns

    B.

     Has a poor torque

    C.

     Can be started easily without load

    D.

     Has almost constant speed

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  5. Sparking at the commutator of a D.C. motor may result in

  6. A.

     Damage to commutator segments

    B.

     Damage to commutator insulation

    C.

     Increased power consumption

    D.

     All of the above

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  7. For which of the following applications a D.C. motor is preferred over an A.C. motor?

  8. A.

     Low speed operation

    B.

     High speed operation

    C.

     Variable speed operation

    D.

     Fixed speed operation

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  9. Which D.C. motor has got maximum self relieving property?

  10. A.

     Series motor

    B.

     Shunt motor

    C.

     Cumulatively compounded motor

    D.

     Differentially compounded motor

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  11. In a manual shunt motor starter

  12. A.

     Over load relay is connected in series and no volt relay in parallel with the load

    B.

     Over load relay is connected in parallel and no volt relay in series with the load

    C.

     Over load relay and no volt relay are both connected in series with the load

    D.

     Over load relay and no volt relay are both connected in parallel with the load

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  13. In Ward-Leonard control the lower limit of speed is imposed by

  14. A.

     Residual magnetism of the generator

    B.

     Core losses of motor

    C.

     Mechanical losses of motor and generator together

    D.

     All of the above

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  15. Which motor should not be started on no-load?

  16. A.

     Series motor

    B.

     Shunt motor

    C.

     Cumulatively compounded motor

    D.

     Differentially compounded motor

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  17. The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by

  18. A.

     Reducing the field current

    B.

     Decreasing the armature current

    C.

     Increasing the armature current

    D.

     Increasing the excitation current

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  19. D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this

  20. A.

     Series motor

    B.

     Shunt motor

    C.

     Compound motor

    D.

     Any of the above

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