Transformers

11. The transformer laminations are insulated from each other by

mica strip
thin coat of varnish
paper
any of the above

Detailed SolutionThe transformer laminations are insulated from each other by

12. No-load current of a transformer has

has high magnitude and low power factor
has high magnitude and high power factor
has small magnitude and high power factor
has small magnitude and low power factor

Detailed SolutionNo-load current of a transformer has

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

friction and windage losses
copper losses
hysteresis and eddy current losses
none of the above

Detailed SolutionIn a given transformer for given applied voltage, losses which remain constant irrespective of load changes are

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

short-circuiting of the secondaries
power factor of one of the transformers is leading while that of the other lagging
transformers having higher copper losses will have negligible core losses
loading of the transformers not in proportion to their kVA ratings

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

15. Which of the following acts as a protection against high voltage surges due to lightning and switching?

Horn gaps
Thermal overload relays
Breather
Conservator

Detailed SolutionWhich of the following acts as a protection against high voltage surges due to lightning and switching?

16. In a transformer the resistance between its primary and secondary is

zero
1 ohm
1000 ohms
infinite

Detailed SolutionIn a transformer the resistance between its primary and secondary is

17. Which of the following parts of a transformer is visible from outside?

Bushings
Core
Primary winding
Secondary winding

Detailed SolutionWhich of the following parts of a transformer is visible from outside?

18. Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds

50°C
80°C
100°C
150°C

Detailed SolutionGas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds

19. Primary winding of a transformer

is always a low voltage winding
is always a high voltage winding
could either be a low voltage or high voltage winding
none of the above

Detailed SolutionPrimary winding of a transformer

20. The core used in high frequency transformer is usually

copper core
cost iron core
air core
mild steel core

Detailed SolutionThe core used in high frequency transformer is usually

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