| 1. | Which of the following is the main advantage of an auto-transformer over a two winding transformer ? | |
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Hysteresis losses are reduced
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Saving in winding material
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Copper losses are negligible
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Eddy losses are totally eliminated
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Report Question| 2. | Harmonics in transformer result in ? | |
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increased core losses
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increased I2R losses
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magnetic interference with communication circuits
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all of the above
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| 3. | The magnetising current of a transformer is usually small because it has ? | |
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small air gap
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large leakage flux
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laminated silicon steel core
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fewer rotating parts
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| 4. | Buchholz's relay gives warning and protection against ? | |
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electrical fault inside the transformer itself
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electrical fault outside the transformer in outgoing feeder
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for both outside and inside faults
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none of the above
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| 5. | Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds ? | |
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50ºC
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80ºC
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100ºC
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150ºC
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| 6. | A Buchholz relay can be installed on ? | |
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auto-transformers
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air-cooled transformers
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welding transformers
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oil cooled transformers
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| 7. | The chemical used in breather is ? | |
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asbestos fibre
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silica sand
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sodium chloride
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silica gel
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| 8. | The use of higher flux density in the transformer design ? | |
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reduces weight per kVA
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reduces iron losses
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reduces copper losses
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increases part load efficiency
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| 9. | What will happen if the transformers working in parallel are not connected with regard to polarity ? | |
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The power factor of the two transformers will be different from the power factor of common load
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Incorrect polarity will result in dead short circuit
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The transformers will not share load in proportion to their kVA ratings
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none of the above
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| 10. | Spacers are provided between adjacent coils ? | |
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to provide free passage to the cooling oil
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to insulate the coils from each other
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both (a) and (b)
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none of the above
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