Transformers

1. A Buchholz relay can be installed on

1. auto-transformers
2. air-cooled transformers
3. welding transformers
4. oil cooled transformers

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2. A common method of cooling a power transformer is

1. natural air cooling
2. air blast cooling
3. oil cooling
4. any of the above

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3. A good voltage regulation of a transformer means

1. output voltage fluctuation from no load to full load is least
2. output voltage fluctuation with power factor is least
3. difference between primary and secondary voltage is least
4. difference between primary and secondary voltage is maximum

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4. A no-load test is performed on a transformer to determine

1. core loss
2. copper loss
3. efficiency
4. magnetising current
5. magnetising current and loss

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5. A shell-type transformer has

1. high eddy current losses
2. reduced magnetic leakage
3. negligibly hysteresis losses
4. none of the above

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6. A transformer can have regulation closer to zero

1. on full-load
2. on overload
3. on leading power factor
4. on zero power factor

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7. A transformer can have zero voltage regulation at

1. leading power factor
2. lagging power factor
3. unity power factor
4. zero power factor

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8. A transformer cannot raise or lower the voltage of a D.C. supply because

1. there is no need to change the D.C. voltage
2. a D.C. circuit has more losses
3. Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero
4. none of the above

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9. A transformer core is laminated to

1. reduce hysteresis loss
2. reduce eddy current losses
3. reduce copper losses
4. reduce all above losses

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10. A transformer oil must be free from

1. sludge
2. odour
3. gases
4. moisture

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