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MCQ of Transformer page-27


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161. The inductive reactance of a transformer depends on

A) electromotive force
B) magnetomotive force
C) magnetic flux
D) leakage flux.

Ans : (D)

162. Which of the following prevents the damage to a transformer due to lightning and switching ?

A) Horn gap
B) Conservator
C) Breather
D) Buchholz relay.

Ans : (A)

163. Which of the following connection of transformer will given the highest secondary voltage ?

A) Delta primary, delta secondary
B) Delta primary, star secondary
C) Star primary, star secondary
D) Star primary, delta secondary.

Ans : (B)

164. In a dry-type transformer, accumulation of dust on the winding and core is likely to cause

A) corrosion of core material
B) short circuiting of primary winding
C) short circuiting of secondary winding
D) reduction in heat dissipation.

Ans : (D)

165. The magnetizing current of a transformer is usually small because it has

A) large leakage flux
B) fewer rotating parts
C) small airgap
D) laminated silicon steel core.

Ans : (C)

166. The characteristics of a voltage transformer are

A) current and voltage both vary with load
B) voltage remaining constant, current varies with load
C) current remaining constant, voltage varies with load
D) current and voltage remain constant, power factor varies with load.

Ans : (B)

167. The operation of an ideal voltage transformer is on which of the following assumptions (s) ?

A) Negligible resistance
B) No leakage flux
C) Non-saturation of core
D) All of the above.

Ans : (D)

168. The efficiency of a transformer at full load 0.85 pF lag is 90%. Its efficiency at full load 0.85 pF lead is

A) less than 90%
B) 90%
C) more than 90%
D) none of above.

Ans : (B)

169. In an ideal transformer, impedance transformers from one side to other

A) In direct ratio of turns
B) In direct square ratio turns
C) In inverse ratio of turns
D) In inverse square ratio of turns.

Ans : (B)

170. In the parallel operation of transformers, which statement is false

A) Transformers transformation ratios same
B) Transformers voltage ratings same
C) Transformers kVA rating equal
D) None of the above.

Ans : (C)

171. When the impedance triangles of two transformers operating in parallel are not identical in shape and size, the two transformers will

A) Get heated unequally
B) Share the load unequally
C) Run with different power factors
D) None of the above.

Ans : (B)

172. The essential condition for parallel operation of two single-phase transformers is that they should have the same

A) voltage ratio
B) kVA rating
C) polarity
D) percentage impedance.

Ans : (A)


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