Transformers

121. Which of the following is not the standard voltage for power supply in India?

1. llkV
2. 33kV
3. 66 kV
4. 122 kV

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122. Which of the following is the main advantage of an auto-transformer over a two winding transformer?

1. Hysteresis losses are reduced
2. Saving in winding material
3. Copper losses are negligible
4. Eddy losses are totally eliminated

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123. Which of the following is the most likely source of harmonics in a transformer?

1. poor insulation
2. Overload
3. loose connections
4. Core saturation

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124. Which of the following loss in a transformer is zero even at full load?

1. Core loss
2. Friction loss
3. Eddy current loss
4. Hysteresis loss

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125. Which of the following parts of a transformer is visible from outside?

1. Bushings
2. Core
3. Primary winding
4. Secondary winding

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126. Which of the following properties is not necessarily desirable for the material for transformer core?

1. Low hysteresis loss
2. High permeability
3. High thermal conductivity
4. Adequate mechanical strength

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127. Which of the following property is not necessarily desirable in the material for transformer core?

1. Mechanical strength
2. Low hysteresis loss
3. High thermal conductivity
4. High permeability

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128. Which of the following protection is normally not provided on small distribution transformers?

1. Overfluxing protection
2. Buchholz relay
3. Overcurrent protection
4. All of the above

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129. 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?

1. Its secondary current is 5 A
2. Its secondary voltage is 400 V
3. Its rating is 2 kVA
4. Its secondary current is 20 A

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130. Which type of winding is used in 3phase shell-type transformer?

1. Circular type
2. Sandwich type
3. Cylindrical type
4. Rectangular type

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