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EEE :: Transformers

  1. The no-load current drawn by transformer is usually what per cent of the full-load current?

  2. A.

     0.2 to 0.5 per cent

    B.

     2 to 5 per cent

    C.

     12 to 15 per cent

    D.

     20 to 30 per cent


  3. The chemical used in breather for transformer should have the quality of

  4. A.

     ionizing air

    B.

     absorbing moisture

    C.

     cleansing the transformer oil

    D.

     cooling the transformer oil


  5. The function of conservator in a transformer is

  6. A.

     to project against internal fault

    B.

     to reduce copper as well as core losses

    C.

     to cool the transformer oil

    D.

     to take care of the expansion and contraction of transformer oil due to variation of temper-ature of sur-roundings


  7. The function of breather in a transformer is

  8. A.

     to provide oxygen inside the tank

    B.

     to cool the coils during reduced load

    C.

     to cool the transformer oil

    D.

     to arrest flow of moisture when outside air enters the transformer


  9. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in

  10. A.

     short-circuiting of the secondaries

    B.

     power factor of one of the transformers is leading while that of the other lagging

    C.

     transformers having higher copper losses will have negligible core losses

    D.

     loading of the transformers not in proportion to their kVA ratings


  11. The value of flux involved m the e.m.f. equation of a transformer is

  12. A.

     average value

    B.

     r.m.s. value

    C.

     maximum value

    D.

     instantaneous value


  13. In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are

  14. A.

     friction and windage losses

    B.

     copper losses

    C.

     hysteresis and eddy current losses

    D.

     none of the above


  15. The changes in volume of transformer cooling oil due to variation of atmospheric tem-perature during day and night is taken care of by which part of transformer

  16. A.

     Conservator

    B.

     Breather

    C.

     Bushings

    D.

     Buchholz relay


  17. Star/star transformers work satisfactorily when

  18. A.

     load is unbalanced only

    B.

     load is balanced only

    C.

     on balanced as well as unbalanced loads

    D.

     none of the above


  19. Delta/star transformer works satisfactorily when

  20. A.

     load is balanced only

    B.

     load is unbalanced only

    C.

     on balanced as well as unbalanced loads

    D.

     none of the above