Transformers Archives

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

pulling the motor directly on line without a starter

locking of rotor due to harmonics

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

interchanging two supply phases for quick stopping

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12. The purpose of providing iron core in a step-up transformer is

To provide coupling between primary and secondary

To increase the magnitude of mutual flux

Detailed SolutionThe purpose of providing iron core in a step-up transformer is

13. The chemical used in breather is

asbestos fiber

silica sand

sodium chloride

silica gel

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button" href="https://exam.pscnotes.com/mcq/the-chemical-used-in-breather-is/#more-58150">Detailed Solution

14. The noise produced by a transformer is termed as

zoom

hum

ringing

buzz

Detailed

Solution

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

0.2 to 0.5 per cent

2 to 5 per cent

12 to 15 per cent

20 to 30 per cent

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16. The power factor of an induction motor under no-load conditions will be closer to

0.2 lagging

0.2 leading

0.5 leading

unity

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

s.Ns

(1 - s)Ns

(Ns - 1)s

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will be" class="read-more button" href="https://exam.pscnotes.com/mcq/in-ns-is-the-synchronous-speed-and-s-the-slip-then-actual-running-speed-of-an-induction-motor-will-be/#more-57635">Detailed Solution

18. If a transformer is continuously operated the maximum temperature rise will occur in

core

windings

tank

any of the above

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

ionizing air

absorbing moisture

cleansing the transformer oil

cooling the transformer oil

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for transformer should have the quality of" class="read-more button" href="https://exam.pscnotes.com/mcq/the-chemical-used-in-breather-for-transformer-should-have-the-quality-of/#more-57512">Detailed Solution

20. Buchholz’s relay gives warning and protection against

electrical fault inside the transformer itself

electrical fault outside the transformer in outgoing feeder

none of the above

Detailed SolutionBuchholz’s relay gives warning and protection against

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