| 1. | In a transformer over currents affect ? | |
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mechanical stress
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temperature rise
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insulation life
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all of the above
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Report Question| 2. | Which of the following materials is suitable for the manufacture of transformer and large turbo-alternator ? | |
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Cast iron
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Cast steel
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Cold rolled grain oriented steel
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Hot rolled grain oriented steel
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| 3. | When secondary of a current transformer is open-circuited its iron core will be ? | |
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hot because of heavy iron core losses taking place in it due to high flux density
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hot because primary will carry heavy current
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cool as there is no secondary current
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none of above will happen
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| 4. | Greater the secondary leakage flux ? | |
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less will be the secondary induced e.m.f.
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less will be the primary induced e.m.f.
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less will be the primary terminal voltage
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none of the above
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| 5. | Which value of flux is involved in the e.m.f. equation of the transformer ? | |
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R.M.S. value
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Critical value
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Average value
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Maximum value
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| 6. | The maximum efficiency of a distribution transformer is ? | |
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at no load
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at 50% full load
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at 50% full load
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at full load
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| 7. | The efficiency of a transformer will be maximum when ? | |
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copper losses = hysteresis losses
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hysteresis losses = eddy current losses
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eddy current losses = copper losses
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copper losses = iron losses
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| 8. | An open-circuit test on a transformer is conducted primarily to measure ? | |
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insulation resistance
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copper loss
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core loss
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total loss
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| 9. | If the supply frequency to the transformer is increased the iron loss will ? | |
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not change
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decrease
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increase
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any of the above
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| 10. | The secondary of a current transformer is always short-circuited under operating conditions because it ? | |
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avoids core saturation and high voltage induction
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is safe to human beings
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protects the primary circuit
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none of the above
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