MCQs on Transformer 101-120

101. A shell-type transformer has
(a) high eddy current losses
(b) reduced magnetic leakage✔
(c) negligibly hysteresis losses
(d) none of the above

102. A transformer can have regulation closer to zero
(a) on full-load
(b) on overload
(c) on leading power factor✔
(d) on zero power factor

103. A transformer transforms
(a) voltage
(b) current
(c) current and voltage
(d) power✔

104. Which of the following is not the standard voltage for power supply in India ?
(a) llkV
(b) 33kV
(c) 66 kV
(d) 122 kV✔

105. Reduction in core losses and increase in permeability are obtained with transformer employing
(a) core built-up of laminations of cold rolled grain oriented steel✔
(b) core built-up of laminations of hot rolled sheet
(c) either of the above
(d) none of the above

106. In a power or distribution transformer about 10 per cent end turns are heavily insulated
(a) to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns✔
(b) to absorb the line surge voltage and save the winding of transformer from damage
(c) to reflect the line surge and save the winding of a transformer from damage
(d) none of the above

107. For given applied voltage, with the increase in frequency of the applied voltage
(a) eddy current loss will decrease
(b) eddy current loss will increase
(c) eddy current loss will remain unchanged✔
(d) none of the above

108. Losses which occur in rotating electric machines and do not occur in trans formers are
(a) friction and windage losses✔
(b) magnetic losses
(c) hysteresis and eddy current losses
(d) copper losses

109. In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are
(a) hysteresis and eddy current losses✔
(b) friction and windage losses
(c) copper losses
(d) none of the above

110. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect ?
(a) Its secondary current is 5 A
(b) Its secondary voltage is 400 V
(c) Its rating is 2 kVA
(d) Its secondary current is 20 A✔

111. The secondary of a current transformer is always short-circuited under operating conditions because it
(a) avoids core saturation and high voltage induction✔
(b) is safe to human beings
(c) protects the primary circuit
(d) none of the above

112. In a transformer the resistance between its primary and secondary should be
(a) zero
(b) 10 Q
(c) 1000 Q
(d) infinity✔

113. A good voltage regulation of a transformer means
(a) output voltage fluctuation from no load to full load is least✔
(b) output voltage fluctuation with power factor is least
(c) difference between primary and secondary voltage is least
(d) difference between primary and secondary voltage is maximum

114. For a transformer, operating at constant load current, maximum efficiency will occur at
(a) 0.8 leading power factor
(b) 0.8 lagging power factor
(c) zero power factor
(d) unity power factor✔

115. Which of the following protection is normally not provided on small distribution transformers ?
(a) Overfluxing protection
(b) Buchholz relay✔
(c) Overcurrent protection
(d) All of the above

116. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
(a) Horn gaps✔
(b) Thermal overload relays
(c) Breather
(d) Conservator

117. The efficiency of two identical transformers under load conditions can be determined by
(a) short-circuit test
(b) back-to-back test✔
(c) open circuit test
(d) any of the above

118. Which of the following insulating materials can withstand the highest temperature safely ?
(a) Cellulose
(b) Asbestos
(c) Mica✔
(d) Glass fibre

119. Which of the following parts of a transformer is visible from outside ?
(a) Bushings✔
(b) Core
(c) Primary winding
(d) Secondary wwinding

120. The noise produced by a transformer is termed as
(a) zoom
(b) hum✔
(c) ringing
(d) buzz