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.Management Sciences
Category: Transformers
Reduction in core losses and increase in permeability are obtained with transformer employing__________?
A. core built-up of laminations of cold rolled grain oriented steel
B. core built-up of laminations of hot rolled sheet
C. either of the above
D. none of the above
Power transformers are generally designed to have maximum efficiency around__________?
A. no-load
B. half-load
C. near full-load
D. 10% overload
Harmonics in transformer result in___________?
A. increased core losses
B. increased I2R losses
C. magnetic interference with communication circuits
D. all of the above
Which of the following acts as a protection against high voltage surges due to lightning and switching ?
A. Horn gaps
B. Thermal overload relays
C. Breather
D. Conservator
The function of conservator in a transformer is___________________?
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 temperature of sur-roundings
In a transformer routine efficiency depends upon_____________?
A. supply frequency
B. load current
C. power factor of load
D. both B. and (c)
Which winding of the transformer has less cross-sectional area?
A. Primary winding
B. Secondary winding
C. Low voltage winding
D. High voltage winding
During open circuit test of a transformer:
A. primary is supplied rated voltage
B. primary is supplied full-load current
C. primary is supplied current at reduced voltage
D. primary is supplied rated kVA
Helical coils can be used on___________?
A. low voltage side of high kVA transformers
B. high frequency transformers
C. high voltage side of small capacity transformers
D. high voltage side of high kVA rating transformers
Efficiency of a power transformer is of the order of________________?
A. 100 per cent
B. 98 per cent
C. 50 per cent
D. 25 per cent
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