50 IMPORTANT MCQ ON TRANSFORMER
1.Oil is provided in an oil filled transformer for
A. Insulation
B. cooling
C. both cooling and insulation.
D. Lubrication
2) The basic function of transformer is to change?
A. the level voltage
B. the level frequency
C. power factor level
D. power level
3) Transformer is used for—
A. to step down voltage
B. to step up and step down primary voltage
C. to step up voltage
D. None of above
4) Breather is provided in a transformer to
A. Absorb moisture of air during breathing.
B. filter of transformer oil
C. provide cold air in transformer
D. None of above
5) The leakage flux in a transformer depends upon
A. the load current.
B. the frequency.
C. the mutual flux.
D. the applied voltage.
6) What kVA rating is required for a transformer
that must handle a maximum load current of 8 A
with a secondary voltage of 2 kV?
A. 32kv
B. 16kv
C. 4kv
D. 8kV
7) The copper loss of a transformer at full load is
40W. What would be at half load-
A. 20W
B. 80W
C. 40W
D. 10W
8) When a 6 V battery is connected across the
primary of a transformer with a turns ratio of 8,
the secondary voltage is
A. 48v
B. 6v
C. 8v
D. 0
9) The main purpose of performing open circuit
test in a transformer is to measure its–
A. core loss
B. copper loss
C. insulation resistance
D. total loss
10) When a 400Hz transformer is operated at 50
Hz, its KVA ratings is–
A. unaffected
B. reduced to 1/8
C. Increased by 8 times
D. None of above
11) What is the condition for maximum efficiency
of a transformer?
A. when copper loss = core loss
B. When transformer run by unity power
factor
C. when copper loss = eddy current loss
D. when copper loss = hysteresis loss
12) Lamination of transformer core is made of
A. cast iron
B. silicon steel.
C. cast steel
D. aluminium
13) Which of the following is minimized by
laminating the core of a transformer?
A. Eddy current loss.
B. Hysteresis loss.
C. Copper loss
D. Stray loss
14) Does the transformer draw any current when
secondary is open?
A. Yes
B. No
15) When the turns ratio of a transformer is 20
and the primary ac voltage is 12 V, the secondary
voltage is
A. 24v
B. 120v
C. 240v
D. 440v
16) The input power under no load condition of
transformer consists of
A. core losses and very small amount of
copper loss in primary.
B. copper loss in transformers.
C. core loss in transformers.
D. None of above.
17) Transformers operating in parallel will share
the load depending upon their-
A. rating
B. Percentage impedance.
C. Leakage reactance.
D. None of above
18) Which of the following is not a basic element
of a transformer?
A. primary winding
B. secondary winding
C. mutual flux
D. core
19) At relatively light load, transformer efficiency
is low because-
A. transformer losses are high
B. secondary output is low
C. fixed loss is high in proportion to the
output
D. Cu loss is small
20) A transformer transform-
A. voltage and currrent
B. voltage
C. current
D. frequency
21) When AC supply is given to the transformer,
the flux will depend on…….
A. Current
B. Voltage
C. Frequency
D. Voltage and Frequency
22) No-load test on a transformer is carried out to
determine-
A. copper loss
B. magnetising current and no-load current
C. magnetising current
D. all of above.
23) Which of the following losses varies with load
in transformer?
A. Copper loss.
B. Core loss
C. Transfomer all losses
D. None of above
24) A transfomer has negative voltage regulation
when its load power factor is–
A. lagging
B. leading
C. unity
D. None of above
25) The essential condition for parallel operation of
two single-phase transformer is that they should
have the same–
A. polarity
B. KVA ratings
C. voltage ratio
D. None of abobe
26) Which one is used for constant street light
load?
A. current transformer
B. Constant current transformer
C. power transformer
D. potential transformer
27) Which of the following losses remain constant
during normal operation of transformer?
A. Copper loss
B. Transformer all losses
C. Core loss
D. None of above
28) Iron loss in transformer can be determined
by…..
A. open circuit test.
B. short circuit test.
29) Transformer core are laminated in order to-
A. simplify it's construction
B. minimize eddy current loss
C. reduce cost
D. reduce hysteresis loss
30) The main purpose of performing short circuit
test in a transformer is to measure its–
A. Copper Loss
B. Core Loss
C. Total Loss
D. Insulation resistance
31) The path of a magnetic flux in a transformer
should have
A. low resistance
B. low reluctance
C. high resistance
D. high reluctance
32) No-load current in a transformer
A. lags behind the voltage by about 75°
B. leads the voltage by about 75°
C. lags behind the voltage by about 15°
D. leads behind the voltage by about 25°
33) Which of the following is not a part of
transformer?
A. Breather
B. Conservator
C. Exciter
D. Buchholz relay
34) While conducting short-circuit test on a
transformer the following side is short circuited
A. Low voltage side
B. High voltage side
C. Primary side
D. Secondary side
35) Which winding in a transformer has more
number of turns ?
A. Primary winding
B. Secondary winding
C. High voltage winding
D. Low voltage winding
36) In a given transformer for given applied
voltage, losses which remain constant irrespective
of load changes are
A. core losses
B. copper losses
C. both A and B
D. none of the above
37) Power transformers are designed to have
maximum efficiency at
A. 80% full load
B. 50% full load
C. nearly full load
D. no load
38) The maximum efficiency of a distribution
transformer is
A. at full load
B. at 70% full load
C. at 50% full load
D. at no load
39) Flash point of transformer insulating oil should
be more than
A. 100°C.
B. 140°C.
C. 45°C.
D. 35°C
.
40) Noise of transformer mainly due to
A. noise generated by cooling fans.
B. magnetostriction in iron core.
C. mechanical vibration.
D. all of above
41) The tap changer in an electrical power
transformer is provided on
A. LV winding.
B. HV winding.
C. either LV or HV winding.
D. both LV and HV winding.
42) The transformer ratings are usually expressed
in terms of
A. KVA
B. KW
C. KVAR
D. Volts
43) A Buchholz relay can be installed on-
A. welding transformers
B. air cooled transformers
C. oil cooled transformers
D. all of above
44) In a transformer the resistance between its
primary and secondary is
A. zero
B. infinite
C. 1 ohm
D. 10000 ohm
45) If the supply frequency to the transformer is
increased, the iron loss will
A. remain same
B. decrease
C. increase
D. any of the above
46) Which type of winding is used in 3phase shelltype
transformer ?
A. Cylindrical type
B. Circular type
C. Rectangular type
D. Sandwich type
47) The secondary winding of which of the
following transformers is always kept closed ?
A. CT
B. PT
C. Step-up transformer
D. Step-down transformer
48) The efficiency of two identical transformers
under load conditions can be determined by
A. back-to-back test
B. short circuit test
C. open circuit test
D. none of above
49) Which of the following loss in a transformer is
zero even at full load ?
A. Hysteresis loss
B. Eddy current loss
C. Core loss
D. Friction loss
50) If supply frequency of a transformer increases,
the secondary output voltage of the transformer -
A. remains same.
B. increases.
C. decreases.
D. any of the above
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