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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.

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Last Answer : If the supply frequency to the transformer is increased, the iron loss will increase.

Description : In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of?

Last Answer : In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of less than 15A.

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

Description : In an actual transformer the iron loss remains practically constant from no load to full load because?

Last Answer : In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.

Description : The secondary of a current transformer is always short-circuited under operating conditions because it?

Last Answer : The secondary of a current transformer is always short-circuited under operating conditions because it avoids core saturation and high voltage induction.

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Last Answer : The efficiency of a transformer, under heavy loads, is comparatively low because copper loss becomes high in proportion to the output.

Description : State and justify which of the following two transformers is better:  Transformer A = 4% voltage regulation  Transformer B = 6% voltage regulation

Last Answer : Transformer A with 4% voltage regulation is better.  Justification: Voltage regulation refers to the percentage change in secondary voltage when load is changed from no-load to full-load with primary voltage ... 4% voltage regulation, which is less as compared to 6% of transformer B, it is better.

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

Last Answer : When a given transformer is run at its rated voltage but reduced frequency, its core flux density is increased.

Description : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?

Last Answer : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses.

Description : A good voltage regulation of a transformer means?

Last Answer : A good voltage regulation of a transformer means output voltage fluctuation from no load to full load is least.

Description : The voltage transformation ratio of a transformer is equal to the ratio of?

Last Answer : The voltage transformation ratio of a transformer is equal to the ratio of secondary induced e.m.f. to primary induced e.m.f.

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Last Answer : If a transformer is switched on to a voltage more than the rated voltage its power factor will deteriorate.

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Last Answer : C. Stall

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Last Answer : B. Flux produced is a small fraction of the normal flux

Description : 52 A transformer has 1000 primary turns, connected to 250V ac supply. To get 400V secondary voltage the no of secondary turns should be A. 1600 B. 250 C. 400 D. 1250

Last Answer : A. 1600

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Last Answer : At 0.866 time voltage value

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Last Answer : C) the voltage applied on primary side is low

Description : During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer

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Last Answer : As transformer is static device with no moving parts, the losses due to friction & windage are completely absent. Hence transformer has efficiency of more than 90%.

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Last Answer : Single phase Transformer Transformer

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Description : Write about transformer on DC.

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Description : Even at no-load, a transformer draws current from the mains. Why?

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

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Last Answer : No-load current in a transformer lags behind the voltage by about 75°.

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

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

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

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

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

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

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

Last Answer : Transformer breaths in when load on it decreases.

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

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

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

Last Answer : In a transformer, the tappings are generally provided on low voltage side.

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

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

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

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