1. Current transformers for meters and relays usually have
a) 10-A secondaries
b) 5-A secondaries
c) 10:1 ratio
d) 1:1 ratio
ans. b
2. The main purpose of using an inter-phase transformer with a multi-anode rectifier is to
a) permit only one anode to fire at a time.
b) cause the anodes to overlap in firing.
c) shorten the period of firing of each anode.
d) act as an insulating transformer between the power transformer and load
ans. b
3. Dust should never be allowed to accumulate on the windings and are of a dry-type transformer because
a) may short-circuit the windings
b) tends to corrode metal surface
c) reduces dissipation of heat
d) absorbs oil and grease
ans. c
4. The relative polarity of the windings of a tranformer may be determined by
a) short-circuit test
b) open-circuit test
c) phasing out
d) back-to-back test
ans. c
5. The most common cause of contamination by water of oil used in transformers located indoors is
a) condensation of moisture from air in the upper part of the tank
b) decomposition of organic matter in the oil.
c) leaky bushings
d) use of filter blotters that have absorbed moisture from the air
ans. b
6. Part of the transformer which is most subject to damage from overheating is
a) winding insulation
b) frame or case
c) iron core
d) copper winding
ans. a
7. In general , the most important point to keep under constant watch during the operation of a transformers is its
a) primary voltage
b) core loss
c) exciting current
d) temperature
ans. d
8. The most essential feature of an auto-transformer is that it
a) is more suited for single-phase supply
b) is completely automatic in its operation
c) uses only one winding
d) none of the above
ans. c
9. When secondary of the transformer is loaded , the primary current will
a) not be effected
b) draw more current
c) draw less current than the secondary current
d) be the vector sum of no load current and excessive current drawn due to the secondary current.
ans. d
10 shell type transformer is commonly used because
a) it has more magnetic flux leakage
b) it has less magnetic flux leakage
c) it has two magnetic paths
d) both b and c are correct
ans. d
a) 10-A secondaries
b) 5-A secondaries
c) 10:1 ratio
d) 1:1 ratio
ans. b
2. The main purpose of using an inter-phase transformer with a multi-anode rectifier is to
a) permit only one anode to fire at a time.
b) cause the anodes to overlap in firing.
c) shorten the period of firing of each anode.
d) act as an insulating transformer between the power transformer and load
ans. b
3. Dust should never be allowed to accumulate on the windings and are of a dry-type transformer because
a) may short-circuit the windings
b) tends to corrode metal surface
c) reduces dissipation of heat
d) absorbs oil and grease
ans. c
4. The relative polarity of the windings of a tranformer may be determined by
a) short-circuit test
b) open-circuit test
c) phasing out
d) back-to-back test
ans. c
5. The most common cause of contamination by water of oil used in transformers located indoors is
a) condensation of moisture from air in the upper part of the tank
b) decomposition of organic matter in the oil.
c) leaky bushings
d) use of filter blotters that have absorbed moisture from the air
ans. b
6. Part of the transformer which is most subject to damage from overheating is
a) winding insulation
b) frame or case
c) iron core
d) copper winding
ans. a
7. In general , the most important point to keep under constant watch during the operation of a transformers is its
a) primary voltage
b) core loss
c) exciting current
d) temperature
ans. d
8. The most essential feature of an auto-transformer is that it
a) is more suited for single-phase supply
b) is completely automatic in its operation
c) uses only one winding
d) none of the above
ans. c
9. When secondary of the transformer is loaded , the primary current will
a) not be effected
b) draw more current
c) draw less current than the secondary current
d) be the vector sum of no load current and excessive current drawn due to the secondary current.
ans. d
10 shell type transformer is commonly used because
a) it has more magnetic flux leakage
b) it has less magnetic flux leakage
c) it has two magnetic paths
d) both b and c are correct
ans. d
