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Transformers - General Questions
Transformers - General Questions 1
Transformers - True or False
  1. The magnetising current of a transformer is usually small because it has

    2. A.

     small air gap
    B.

     large leakage flux
    C.

     laminated silicon steel core
    D.

     fewer rotating parts

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  2. Which of the following insulating materials can withstand the highest temperature safely?

    3. A.

     Cellulose
    B.

     Asbestos
    C.

     Mica
    D.

     Glass fibre

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  3. In case of 3-phase induction motors, plugging means

    4. A.

     pulling the motor directly on line without a starter
    B.

     locking of rotor due to harmonics
    C.

     starting the motor on load which is more than the rated load
    D.

     interchanging two supply phases for quick stopping

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  4. The main reason for generation of harmonics in a transformer could be

    5. A.

     fluctuating load
    B.

     poor insulation
    C.

     mechanical vibrations
    D.

     saturation of core

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  5. When secondary of a current transformer is open-circuited its iron core will be

    6. A.

     hot because of heavy iron losses taking place in it due to high flux density
    B.

     hot because primary will carry heavy current
    C.

     cool as there is no secondary current
    D.

     none of above will happen

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  6. Spacers are provided between adjacent coils

    7. A.

     to provide free passage to the cooling oil
    B.

     to insulate the coils from each other
    C.

     both (A) and (B)
    D.

     none of the above

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  7. A shell-type transformer has

    8. A.

     high eddy current losses
    B.

     reduced magnetic leakage
    C.

     negligibly hysteresis losses
    D.

     none of the above

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  8. In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be

    9. A.

     Ns
    B.

     s.N.
    C.

     (l-s)Ns
    D.

     (Ns-l)s

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  9. Distribution transformers are generally designed for maximum efficiency around

    10. A.

     90% load
    B.

     Zero load
    C.

     25% load
    D.

     50% load

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  10. Power transformers are generally designed to have maximum efficiency around

    11. A.

     no-load
    B.

     half-load
    C.

     near full-load
    D.

     10% overload

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