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EEE :: D.C. Generators

  1. Laminations of core are generally made of

  2. A.

     Case iron

    B.

     Carbon

    C.

     Silicon steel

    D.

     Stainless steel

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  3. In D.C. generators on no-load, the air gap flux distribution in space is

  4. A.

     Sinusoidal

    B.

     Triangular

    C.

     Pulsating

    D.

     Flat topped

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  5. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave

  6. A.

     will be zero

    B.

     will be of 5 Hz

    C.

     will be of 5 xiVHz

    D.

     will be of v Hz 5

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  7. The essential condition for parallel operation of two D.C. generators is that they have

  8. A.

     Same kW rating

    B.

     The same operation r.p.m.

    C.

     The same drooping voltage characteristics

    D.

     Same percentage regulation

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  9. Which of the following could be lamina proximately the thickness of laminations of a D.C. machine?

  10. A.

     0.005 mm

    B.

     0.05 mm

    C.

     0.5 m

    D.

     5 m

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  11. The rapid wear of brushes takes place due to

  12. A.

     Abrasion from dust

    B.

     Excessive spring pressure

    C.

     Rough commutator bars

    D.

     All of the above factors

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  13. In case of D.C. machine winding, number of commutator segments is equal to

  14. A.

     Number of armature coils

    B.

     Number of armature coil sides

    C.

     Number of armature conductors

    D.

     Number of armature turns

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  15. The insulating material used between the commutator segments is normally

  16. A.

     Graphite

    B.

     Paper

    C.

     Mica

    D.

     Insulating varnish

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  17. The bearings used to support the rotor shafts are generally

  18. A.

     Ball bearings

    B.

     Bush bearings

    C.

     Magnetic bearings

    D.

     Needle bearings

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  19. If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to

  20. A.

     reverse the field connections

    B.

     increase the field resistance

    C.

     increase the speed of primemover

    D.

     check armature insulation resistance

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