1.With increase in supply frequency of a transformer, there is
a) decrease in rating
b) increase in rating
c) no change in rating
d) none of these
ans. b
2. The essential condition for parallel operation of two single phase transformers is that they should have same
a) polarity
b) phase sequence
c) voltage ratio
d) percentage impedances
ans. a
3. Two transformers operating in parallel will share the load depending upon their
a) rating
b) leakage reactance
c) efficiency
d) per-unit impedance
ans. a
4. Which of the following method is used for cooling of transformer up-to a capacity of 10 MVA ?
a) oil natural cooling
b) Air blast cooling
c) Forced oil cooling
d) none of these
ans. a
5. Out of the following choices for polyphase transformer connections which one will you select for 3 to 2 phase conversion?
a) scott
b) star/star
c) double scott
d) star/double-delta
ans. a
6. When two identical transformers are available , then the best method to find their efficiency under load condition is
a) short-circuit test
b) back to back test
c) open-circuit
d) phase sequence test
ans. b
7. The open-circuit test on a transformer is meant for measuring its
a) copper losses
b) iron losses
c) insulation resistance
d) equivalent resistance
ans. b
8. Oil is invariably used in large transformers in order to
a) insulate the coils
b) insulate the core
c) lubricate the core
d) lubricate the coils
ans. a
9. The secondary winding if a current transformer whose primary is carrying current should
a) not be open circuited
b) not be short circuited
c) always be open circuited
d) not be connected to the current coil of a wattmeter
ans. a
10. Before disconnecting an ammeter from an energised current transformer circuit, the current tranformer
a) primary should be opened
b) secondary should be opened
c) primary should be shorted
d) secondary should be shorted
ans. d
a) decrease in rating
b) increase in rating
c) no change in rating
d) none of these
ans. b
2. The essential condition for parallel operation of two single phase transformers is that they should have same
a) polarity
b) phase sequence
c) voltage ratio
d) percentage impedances
ans. a
3. Two transformers operating in parallel will share the load depending upon their
a) rating
b) leakage reactance
c) efficiency
d) per-unit impedance
ans. a
4. Which of the following method is used for cooling of transformer up-to a capacity of 10 MVA ?
a) oil natural cooling
b) Air blast cooling
c) Forced oil cooling
d) none of these
ans. a
5. Out of the following choices for polyphase transformer connections which one will you select for 3 to 2 phase conversion?
a) scott
b) star/star
c) double scott
d) star/double-delta
ans. a
6. When two identical transformers are available , then the best method to find their efficiency under load condition is
a) short-circuit test
b) back to back test
c) open-circuit
d) phase sequence test
ans. b
7. The open-circuit test on a transformer is meant for measuring its
a) copper losses
b) iron losses
c) insulation resistance
d) equivalent resistance
ans. b
8. Oil is invariably used in large transformers in order to
a) insulate the coils
b) insulate the core
c) lubricate the core
d) lubricate the coils
ans. a
9. The secondary winding if a current transformer whose primary is carrying current should
a) not be open circuited
b) not be short circuited
c) always be open circuited
d) not be connected to the current coil of a wattmeter
ans. a
10. Before disconnecting an ammeter from an energised current transformer circuit, the current tranformer
a) primary should be opened
b) secondary should be opened
c) primary should be shorted
d) secondary should be shorted
ans. d
