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.Management Sciences
Category: Transformers
Buchholz’s relay gives warning and protection against_________________?
A. electrical fault inside the transformer itself
B. electrical fault outside the transformer in outgoing feeder
C. for both outside and inside faults
D. none of the above
Star/star transformers work satisfactorily when________________?
A. load is unbalanced only
B. load is balanced only
C. on balanced as well as unbalanced loads
D. none of the above
Distribution transformers are generally designed for maximum efficiency around________________?
A. 90% load
B. zero load
C. 25% load
D. 50% load
The leakage flux in a transformer depends upon______________?
A. load current
B. load current and voltage
C. load current, voltage and frequency
D. load current, voltage, frequency and power factor
For given applied voltage, with the increase in frequency of the applied voltage?
A. eddy current loss will decrease
B. eddy current loss will increase
C. eddy current loss will remain unchanged
D. none of the above
If a transformer is continuously operated the maximum temperature rise will occur in_______________?
A. core
B. windings
C. tank
D. any of the above
A transformer cannot raise or lower the voltage of a D.C. supply because_______________?
A. there is no need to change the D.C. voltage
B. a D.C. circuit has more losses
C. Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero
D. none of the above
The secondary winding of which of the following transformers is always kept closed?
A. Step-up transformer
B. Step-down transformer
C. Potential transformer
D. Current transformer
The core used in high frequency transformer is usually___________?
A. copper core
B. cost iron core
C. air core
D. mild steel core
Open circuit test on transformers is conducted to determine____________?
A. hysteresis losses
B. copper losses
C. core losses
D. eddy current losses
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