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Spacers are provided between adjacent coils to provide free passage to the cooling oil.

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Description : State any four characteristics of core type transformer.

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Description : Explain construction and working of single phase Auto transformer.

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Answer : The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.

Answer : In the transformer low voltage winding has got more cross-sectional area.

Answer : A transformer cannot raise or lower the voltage of a D.C. supply because Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero.

Answer : Primary winding of a transformer could either be a low voltage or high voltage winding.

Answer : High voltage winding in a transformer has more number of turns.

Answer : The efficiency of a power transformer is of the order of 98 percent.

Answer : The no load current in a transformer lags behind the applied voltage by an angle of about 75°.

Answer : In a transformer, routine efficiency depends upon load current and power factor of load.

Answer : The maximum efficiency of a distribution transformer is at 50% full load.

Answer : Transformer breaths in when load on it decreases.

Answer : No-load current of a transformer has small magnitude and low power factor.

Answer : Greater the secondary leakage flux less will be the secondary induced e.m.f.

Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.

Answer : The power transformer is a constant main flux device.

Answer : The use of higher flux density in the transformer design reduces weight per kVA.

Answer : The chemical used in breather for transformer should have the quality of cleansing the transformer oil.

Answer : The chemical used in breather is silica gel.

Answer : An ideal transformer has infinite values of primary and secondary inductances. The statement is false.

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Answer : The thickness of laminations used in a transformer is usually 0.4 mm to 0.5 mm.

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Answer : The main reason for generation of harmonics in a transformer could be saturation of core.

Answer : Star/star transformers work satisfactorily when load is balanced .

Answer : Delta/star transformer works satisfactorily when on balanced as well as unbalanced loads.

Answer : The magnetising current of a transformer is usually small because it has small air gap.

Answer : The leakage flux in a transformer depends upon load current.

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