Transformer MCQ Questions and Answers

121. 2 transformers, each having iron loss of P_i watts and full-load copper loss of P_e, are put to the back-to-back test and the full-load current is allowed to flow through the secondaries, the total input power (P_in) will be

1. 2P_i
2. P_e
3. P_i +P_e
4. 2(P_i+P_e)

122. The inrush current of a transformer at no load is maximum if the supply voltage is switched on

1. At peak voltage value
2. At zero voltage value
3. At half voltage value
4. At 0.866 time voltage value

123. Open circuit test and short circuit test does not determine

1. parameters of an equivalent circuit
2. constant losses 
3. voltage regulation
4. efficiency

Incorrect amongst the given is/are

1. 1, 2, 3 and 4
2. Only 1
3. Only 3
4. None

124. A 60 KVA transformer at full load the copper losses 1000 W while the core losses 500 W. What is the proportion of full load at maximum efficiency?

1. 70.71 %
2. 63.40 %
3. 50 %
4. 41.50 %

125. For an ideal transformer, the incorrect statement is

1. Transformer core has infinity permeability
2. Primary winding has zero resistance
3. Infinite resistive voltage drop
4. Zero magnetic leakage flux

126. A shell-type transformer has _______ limbs and ________ yoke.

1. 2, 1
2. 2, 2
3. 3, 2
4. 2, 3

127. T-T Scott connection is suitable for

1. Large HV transformers
2. Small HV transformers
3. Supply networks
4. AC motor starting

128. Short circuit test is conducted at ________side while _______ side is ________

1. HV, LV, short-circuited with thick conductor
2. LV, HV, short-circuited with thick conductor
3. HV, LV, open-circuited
4. LV, HV, open-circuited with thin conductor

129. Voltage regulation in a transformer is always positive at all

1. Lagging p.f. load
2. Zero p.f.
3. Lagging and unity p.f. loads
4. Leading p.f. loads

130. If the frequency of a transformer is increased 3 times, maximum flux density in the core

1. Increases 3 times
2. Decreases 3 times
3. Increases 9 times
4. Decreases 9 times

131. In a transformer, variable losses = 600 W, hysteresis loss = 20 W and iron loss = 500 W. what is the magnitude of eddy current losses?

1. 1120 W
2. 100 W
3. 480 W 
4. 1080 W

132. Power transformed from primary to secondary in a transformer depends upon

1. Number of primary turns
2. Transformation ratio
3. Number of secondary turns
4. Magnetic coupling between windings

133. The core in a large power transformer is a unit of

1. Mild steel
2. Ferrite
3. Cast iron
4. Silicon steel

134. The 25 KVA transformer has a voltage ratio of 3300/400V. Find the primary current.

1. 6.25 A
2. 75.8 A
3. 62.5 A
4. 7.58 A

135. The power transformer is a constant ________ device.

1. Current
2. Voltage
3. Main flux
4. Power

136. A transformer may have two or more ratings depending upon the type of

1. Insulation used
2. Winding
3. Core used
4. Cooling used

137. The two winding of a transformer are

1. Conductively linked
2. Inductively linked
3. Not linked at all
4. Electrostatically linked

138. The Varnish protects the insulating materials against

1. Moisture, dust and oil
2. Moisture and fire hazards
3. Dust and oil
4. None of the above

139. In which type of following windings extra insulation between layer is required in addition to the insulation of conductors

1. Helical windings
2. Continuous disc windings
3. Cross over windings
4. Sandwich windings

140. Hysteresis loss in a transformer depends upon

1. Frequency
2. Supply voltage
3. Square of the frequency alone
4. Square of the voltage alone