Hi friends, this post is about transformer objectives. These are some of the questions asked in previous question papers of Gate, IES and other competitive exams. check out and comment if you have any doubts.....
1) The harmonic currents in a power transformer does not cause increase in
A) secondary voltage
B) core loss
C) copper loss
D) magnetic interference with protective relays
Ans:A
2) The magnetizing current in a transformer is rich in
A) 3rd harmonic
B) 5th harmonic
C) 7th harmonic
D) 13th harmonic
Ans:A
3) Scott connections are used for
A) single phase to three phase transformation
B) three phase to single phase transformation
C) three phase to two phase transformation
D) any of the above
Ans:C
4) For successful parallel operation of two single phase transformers, the most essential condition is that their
A) percentage impedances are equal
B) polarities are properly connected
C) turn-ratios are exactly equal
D) KVA ratings are equal
Ans:B
5) Two transformers operating in parallel will share the load depending upon their
A) ratings
B) leakage reactance
C) efficiency
D) per unit impedance
Ans:D
6) Two transformers of identical voltages but of different capacities are operating in parallel, For satisfactory load sharing
A) impedance must be equal
B) per unit impedance must be equal
C) per unit impedance and X/R ratio must be equal
D) impedance and X/R ratio must be equal
Ans:C
7) In scott-connections, teaser transformer operates on 0.866 of its rated
A) impedance
B) current
C) voltage
D) power
Ans:C
8) In which transformer,tertiary winding is used
A) star-delta
B) Delta-delta
C) star-star
D) Delta-star
Ans:C
9) Zero sequence currents can flow from a line into a transformer bank if the winding are
A) grounded star/delta
B) delta/star
C) star/grounded star
D) delta/delta
Ans:C
10) In a transformer fed from a fundamental frequency voltage source, the source of harmonics is the
A) overload
B) poor insulation
C) iron loss
D) saturation of core
Ans:D
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