Objective Transformers Questions and Answers pdf

71.    Harmonics in transformer result in
(a)    increased core losses
(b)    increased I2R losses
(c)    magnetic interference with communication circuits
(d)    all of the above
Ans: d

72.    The core used in high frequency transformer is usually
(a) copper core     
(b) cost iron core
(c) air core 
(d) mild steel core
Ans: c

73. The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be
(a) 6400 W 
(b) 1600 W
(c) 800 W 
(d) 400 W
Ans: d

74.   The value of flux involved m the e.m.f. equation of a transformer is
(a)     average value
(b)     r.m.s. value
(c)    maximum value
(d)    instantaneous value
Ans: c

75. Silicon steel used in laminations mainly reduces
(a)    hysteresis loss
(b)    eddy current losses
(c)    copper losses
(d)    all of the above
Ans: a

76. Which winding of the transformer has less cross-sectional area ?
(a)    Primary winding
(b)    Secondary winding
(c)    Low voltage winding
(d)    High voltage winding
Ans: d

77. Power transformers are generally designed to have maximum efficiency around
(a) no-load 
(b) half-load
(c) near full-load  
(d) 10% overload
Ans: c

.78. Which of the following is the main advantage of an auto-transformer over a two winding transformer ?
(a)    Hysteresis losses are reduced
(b)    Saving in winding material
(c)    Copper losses are negligible
(d)    Eddy losses are totally eliminated
Ans: b

79. During short circuit test iron losses are negligible because
(a)    the current on secondary side is negligible
(b)    the voltage on secondary side does not vary
(c)    the voltage applied on primary side is low
(d)    full-load current is not supplied to the transformer
Ans: c

80. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in
(a)     short-circuiting of the secondaries
(b)     power factor of one of the trans¬formers is leading while that of the other lagging
(c)    transformers having higher copper losses will have negligible core losses
(d)    loading of the transformers not in proportion to their kVA ratings
Ans: d

Read More Questions:
Transformers MCQs Part1
Transformers MCQs Part2

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