Power Transformer MCQs Part 09

81. When a transformer operate under no load conditions the current
a. will lag the applied voltage by 90
b. will lag the applied voltage by about 90 and 75
c. will lead the applied voltage by about 75 degree
d. will be in phase with the applied voltage

82. The useful flux of a transformer is 1.2 weber . when the transformer is loaded at 0.8 p.f lagging the mutual flux will be closer to
a. 1.5 webers
b. 1.28 webers
c. 1.2 weber
d.1.1 weber

83. In an auto transformer a break occurs at the point P . The value of V2 will be
a. 200 V
b. 100 V
c. 50 V
d. Zero

84. Which of the following condition should be fulfilled for the parallel operation of two transformers
a. Ratio of equivalent resistance and equivalent reactance should be the same
b. Turn ratio should be the same
c. percentage impedance should be the same
d. All of the above

85. If a transformer core is made up of copper and coils are made up of steel wire then.
a. magnetising current will be reduced
b. copper losses in the winding will be more
c. eddy current losses will be less
d. all of the above

86. Which of the following loss in a transformer is zero even at full lord?
a. eddy current loss
b. hysteresis loss
c. core loss
d. friction loss

87. The copper losses are represented by which curve?
a. A
b. B
c. C
d. E

88. 1 tesla is the same as
a. 1 weber
b. 1 benry
c. 1 weber / m square
d. 100 weber / m square

89. As a general rule, the KVA rating ratio of transformers operating in parallel should be with int
a. 2 : 1
b. 3 : 1
c. 4 : 1
d. 5 : 1

90. If two transformers not having the same percentage impedance are connected it parallel for sharing a load then
a. one of the transformer will be always fully loaded
b. one of the transformers is likely to get burnt
c. load shedding of the transformer will not be proportional to KVA ratings
d. power factor of both the transformer will be lagging