Transformer MCQ Questions and Answers

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

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

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

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

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

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

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

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

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

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

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

170. Transformer oil should have

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

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

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

173. Merz-price protection is used to protect

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

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

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

176. Transformer oil is used as

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

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

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

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

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