Transformer MCQ Questions and Answers

161. The efficiency of ________ is more than 90%.

  1. Motor 
  2. Transformer
  3. Generator
  4. None of these

Answer
Answer. b

162. Ferrite cores are used in high-frequency transformer because it has

  1. Average permeability
  2. Low hysteresis
  3. Low impedance
  4. High resistance

Answer
Answer. d

163. A transformer having 1000 primary turns is connected to a 250 V ac supply. For a secondary voltage of 400V, the number of secondary turns should be

  1. 1600
  2. 250
  3. 400
  4. 1250

Answer
Answer. a

164. If a transformer has hysteresis loss of 10 watts on AC and is changed to DC supply of the same magnitude, then the hysteresis loss will be

  1. Double
  2. Half
  3. Zero
  4. None of these

Answer
Answer. c

165. Two transformers when operating in parallel will share the load depending upon their

  1. Alternating current
  2. Inductive reactance
  3. Per unit impedance
  4. Efficiency

Answer
Answer. c

166. What is the energy efficient transformer core made up of?

  1. Silicon alloyed iron (grain oriented)
  2. Iron
  3. Amorphous core- metallic glass alloy
  4. None of these

Answer
Answer. a

167. As compared to an amplifier, a transformer can not

  1. Decrease the output voltage
  2. Increase the input current
  3. Increase the output power
  4. None of these

Answer
Answer. c

168. Distribution transformers have core losses

  1. More than full load copper losses
  2. Equal to full load copper losses
  3. Less than full load copper losses
  4. Negligible compared to full load copper

Answer
Answer. c

169. In star-star connected transformer

  1. Line voltage is equal to phase voltage
  2. Line voltage is equal to \sqrt{3} phase voltage
  3. There is no line current
  4. There flows no phase current

Answer
Answer. b

170. Transformer oil should have

  1. High flash point
  2. High viscosity
  3. High sludging tendencies
  4. None of the above

Answer
Answer. a

171. The cold rolled grain oriented steel has _________ permeability in the direction of the grain orientation.

  1. Minimum
  2. Maximum
  3. Nil
  4. None of these

Answer
Answer. b

172. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in

  1. Short-circuiting of the secondaries
  2. Power factor of one of the transformers is leading while that of the other is lagging
  3. Loading of the transformers not in proportion to their KVA ratings
  4. Transformers having higher copper losses will have negligible core losses

Answer
Answer. c

173. Merz-price protection is used to protect

  1. Transformers only
  2. Motors only
  3. Transformers and generators
  4. Transmission line and transformer

Answer
Answer. c

174. A three ring synchronous converter supplying a D.C. 3-wire system must have the secondary of its transformer connected as

  1. Delta only
  2. Delta or star
  3. Zig-zag only
  4. Star or zig-zag

Answer
Answer. c

175. Out of following choices for poly-phase transformer connections which one will you select for three-to-two phase

  1. Scott
  2. Star/star
  3. Double Scott
  4. Star/double Scott
Answer
Answer. a

176. Transformer oil is used as

  1. Instant only
  2. Coolant only
  3. Inert medium
  4. Both insulant and coolant
Answer
Answer. d

177. Under heavy loads, transformer efficiency is comparatively low because

  1. Voltage drop both in primary and secondary becomes large
  2. Secondary output is much less as compared to the primary input
  3. Copper loss becomes high in proportion to the output
  4. Iron loss increases considerably
Answer
Answer. c

178. In Merz price percentage differential protection of Δ-Y transformer, the CT secondary connection in the primary and secondary windings of the transformer would be in the form of

  1. Δ-Y
  2. Y-Δ
  3. Δ-Δ
  4. Y-Y
Answer
Answer. b

179. Which one of the following relay has the capability of anticipating the possible major fault in a transformer

  1. Buchholz relay
  2. Over-current relay
  3. Differential relay
  4. Overfluxing relay
Answer
Answer. a

180. With core type transformers, the limbs are stepped to

  1. Reduce the zinc material and therefore, zinc loss
  2. Reduce the conductor material and, therefore I2R loss
  3. Produce better cooling
  4. Supply more mechanical strength to the core
Answer
Answer. b
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