Transformers

21. A shell-type transformer has

high eddy current losses
reduced magnetic leakage
negligibly hysteresis losses
none of the above

Detailed SolutionA shell-type transformer has

22. Power transformers are designed to have maximum efficiency at

nearly full load
70% full load
50% full load
no load

Detailed SolutionPower transformers are designed to have maximum efficiency at

23. The efficiency of a transformer will be maximum when

copper losses = hysteresis losses
hysteresis losses = eddy current losses
eddy current losses = copper losses
copper losses = iron losses

Detailed SolutionThe efficiency of a transformer will be maximum when

24. Which of the following is not the standard voltage for power supply in India?

llkV
33kV
66 kV
122 kV

Detailed SolutionWhich of the following is not the standard voltage for power supply in India?

25. Reduction in core losses and increase in permeability are obtained with transformer employing

core built-up of laminations of cold rolled grain oriented steel
core built-up of laminations of hot rolled sheet
either of the above
none of the above

Detailed SolutionReduction in core losses and increase in permeability are obtained with transformer employing

26. Harmonics in transformer result in

Increased core losses
Increased I2R losses
Magnetic interference with communication circuits
All of the above

Detailed SolutionHarmonics in transformer result in

27. Minimum voltage regulation occurs when the power factor of the load is

unity
lagging
leading
zero

Detailed SolutionMinimum voltage regulation occurs when the power factor of the load is

28. Open circuit test on transformers is conducted to determine

hysteresis losses
copper losses
core losses
eddy current losses

Detailed SolutionOpen circuit test on transformers is conducted to determine

29. The function of conservator in a transformer is

to project against internal fault
to reduce copper as well as core losses
to cool the transformer oil
to take care of the expansion and contraction of transformer oil due to variation of temper-ature of sur-roundings

Detailed SolutionThe function of conservator in a transformer is

30. What will happen if the transformers working in parallel are not connected with regard to polarity?

The power factor of the two transformers will be different from the power factor of common load
Incorrect polarity will result in dead short circuit
The transformers will not share load in proportion to their kVA ratings
none of the above

Detailed SolutionWhat will happen if the transformers working in parallel are not connected with regard to polarity?

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