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MCQ of Transformer page-24


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131. If the transformer core is made of copper

A) copper losses will be less
B) eddy current losses will be more
C) hysteresis losses will be more
D) none of the above.

Ans : (B)

132. If the secondary of a 5:1 step down transformer is connected to the primary of a 10:1 step down transformer, the total step down ratio of transformation will be

A) 5 : 1
B) 10 : 1
C) 50 : 1
D) 2500 : 1.

Ans : (C)

133. The efficiency of the identical transformers under load conditions can be determined by

A) back to back test
B) open circuit test
C) short circuit test
D) any of the above.

Ans : (A)

134. Which of the following condition should be fulfilled for the parallel operation of two transformers ?

A) Ratio of equivalent resistance and equivalent reactance should be the same
B) Turn ratio should be the same
C) Percentage impedance should be the same
D) All of the above.

Ans : (D)

135. If two transformers not having the same percentage impedances are connected in parallel for sharing a load, then

A) one of the transformers will be always fully loaded
B) one of the transformers is likely to get burnt
C) load sharing of the transformers will not be proportional to kVA ratings
D) power factor of both the transformer will be lagging.

Ans : (C)

136. We can find _ of the transformer with open-circuit test

A) copper losses
B) total equivalent resistances
C) turns ratio
D) total equivalent leakage reactance.

Ans : (C)

137. Harmonic currents in a transformer cause

A) magnetic interference with protective relays
B) increased core loss
C) increased I2R loss
D) all of the above.

Ans : (A)

138. Which of the following is the most likely source of harmonics in a transformer ?

A) Over load
B) Core saturation
C) Poor insulation
D) Loose connections.

Ans : (B)

139. In Scott connections, the main transformer has centre tap on

A) primary windings
B) secondary windings
C) both primary and secondary windings
D) none of the above.

Ans : (A)

140. In Scott connections, the teaser transformer operates on 0.866 of its

A) rated current
B) rated voltage
C) rated power
D) rated impedance.

Ans : (B)


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