The no load current in a transformer lags behind the applied voltage by an angle of about?

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The no load current in a transformer lags behind the applied voltage by an angle of about?

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asked Mar 19, 2018 by anonymous

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65)No-load current in a transformer A. Lags behind the voltage by about 75 deg B. leads the voltage by about 75 C. lags behind the voltage by about 15 D. leads the voltage by about 15

21 views 0 answers

asked Jul 21, 2021 by jyoti kurekar

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

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.

152 views 1 answer

asked Mar 19, 2018 by anonymous

No load current in a transformer: (A) lags the applied voltage by 90° (B) lags the applied voltage by somewhat less than 90° (C) leads the applied voltage by 90° (D) leads the applied voltage by somewhat less than 90°

No load current in a transformer: (A) lags the applied voltage by 90° (B) lags the applied voltage by somewhat less than 90° (C) leads the applied voltage by 90° (D) leads the applied voltage by somewhat less than 90°
Last Answer : Ans: B The primary input current under no load conditions has to supply (i) iron losses in the core i.e hysteresis loss and eddy current loss (ii) a very small amount of Cu loss in the primary (there being no Cu loss in secondary as it is open)

6 views 1 answer

asked Jul 20, 2021 by itszee

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

114 views 0 answers

asked Apr 28, 2020 by anonymous

No-load current in a transformer?

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

90 views 1 answer

asked Mar 19, 2018 by anonymous

No-load current of a transformer has?

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

72 views 1 answer

asked Mar 19, 2018 by anonymous

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

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

51 views 1 answer

asked Jul 19, 2021 by jyoti kurekar

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

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

4 views 1 answer

asked Jul 18, 2021 by jyoti kurekar

7 The main advantage of auto transformer over a two winding transformer is A. Hysteresis losses are reduced B. Saving in winding material C. Copper losses are negligible D. Eddy losses are totally eliminated 8 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

7 The main advantage of auto transformer over a two winding transformer is A. Hysteresis losses are reduced B. Saving in winding material C. Copper losses are negligible D. Eddy losses are totally ... voltage applied on primary side is low D. Full-load current is not supplied to the transformer

21 views 0 answers

asked Jul 17, 2021 by jyoti kurekar

For a transformer, operating at constant load current, maximum efficiency will occur at?

For a transformer, operating at constant load current, maximum efficiency will occur at?
Last Answer : For a transformer, operating at constant load current, maximum efficiency will occur at unity power factor.

124 views 1 answer

asked Mar 19, 2018 by anonymous

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

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.

156 views 1 answer

asked Mar 19, 2018 by anonymous

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

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.

113 views 1 answer

asked Mar 19, 2018 by anonymous

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

A no-load test is performed on a transformer to determine?
Last Answer : A no-load test is performed on a transformer to determine magnetizing current and loss.

124 views 1 answer

asked Mar 19, 2018 by anonymous

The full-load copper loss of a transformer is 1600 W At half-load, the copper loss will be?

Last Answer : The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be 400 W.

149 views 1 answer

asked Mar 19, 2018 by anonymous

An ideal transformer will have maximum efficiency at a load such that?

Last Answer : An ideal transformer will have maximum efficiency at a load such that copper loss equal to iron loss.

204 views 1 answer

asked Mar 19, 2018 by anonymous

The maximum load that a power transformer can carry is limited by its?

The maximum load that a power transformer can carry is limited by its?
Last Answer : The maximum load that a power transformer can carry is limited by its voltage ratio.

133 views 1 answer

asked Mar 19, 2018 by anonymous

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

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.

179 views 1 answer

asked Jul 27, 2019 by anonymous

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

Last 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.

344 views 1 answer

asked Mar 19, 2018 by anonymous

When a given transformer is run at its rated voltage but reduced frequency, its?

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

110 views 1 answer

asked Mar 19, 2018 by anonymous

A good voltage regulation of a transformer means?

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.

98 views 1 answer

asked Mar 19, 2018 by anonymous

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

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.

166 views 1 answer

asked Mar 19, 2018 by anonymous

If a transformer is switched on to a voltage more than the rated voltage?

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

97 views 1 answer

asked Mar 19, 2018 by anonymous

A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and

A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are (A) 140 W (B) 180 W (C) 240 W (D) 480 W
Last Answer : A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are 240 W

95 views 1 answer

asked Apr 28, 2018 by anonymous

The magnetising current of a transformer is usually small because it has?

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

78 views 1 answer

asked Mar 19, 2018 by anonymous

When secondary of a current transformer is open-circuited its iron core will be?

When secondary of a current transformer is open-circuited its iron core will be?
Last Answer : When secondary of a current transformer is open-circuited its iron core will be hot because of heavy iron losses taking place in it due to high flux density.

165 views 1 answer

asked Mar 19, 2018 by anonymous

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

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.

107 views 1 answer

asked Mar 19, 2018 by anonymous

The inrush current of a transformer at no load is maximum if the supply voltage is switched on

The inrush current of a transformer at no load is maximum if the supply voltage is switched on (1) at peak voltage value (2) at zero voltage value (3) at half voltage value (4) at 0.866 time voltage value
Last Answer : At 0.866 time voltage value

114 views 2 answers

asked Apr 30, 2018 by anonymous

In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.

In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.
Last Answer : Ans: C This is vector group and has +30° displacement. Therefore, delta side leads by +30°.

32 views 1 answer

asked Jul 19, 2021 by itszee

Explain the effect of Harmonics on the Transformer.

Explain the effect of Harmonics on the Transformer.
Last Answer : Effect of Harmonics on the Transformer: 1. Core loss: Harmonic voltage increases the hysteresis and eddy current losses in the lamination. The amount of the core loss depends on ... small core vibrations. 5. Saturation problem: Sometimes additional harmonic voltage causes core saturation.

127 views 1 answer

asked May 22, 2020 by anonymous

List two special feature of welding transformer.

List two special feature of welding transformer.
Last Answer : Special features of welding transformer: i) It is a step down transformer that reduces the source voltage to a voltage desired according to the demands of the welding process. ii) Having large primary turns and less ... V ii) Secondary voltage - 40 to 60 V iii) Secondary current - 200 to 600 A

148 views 1 answer

asked May 22, 2020 by anonymous

State two applications of isolation transformer

State two applications of isolation transformer
Last Answer : Applications of isolation transformer: i) Isolates the load equipment from supply ground: ii) Reduction of voltage spikes iii) It acts as a decoupling device. iv) Protects loads from harmonic distortion.

54 views 1 answer

asked May 22, 2020 by anonymous

State why a transformer always have an efficiency of more than 90%.

State why a transformer always have an efficiency of more than 90%.
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%.

270 views 1 answer

asked May 22, 2020 by anonymous

Equivalent circuit of transformer

Equivalent circuit of transformer
Last Answer : Equivalent Circuit Diagram of Transformer Referred to Primary: V1 -Primary Input voltage I1 - Input Current I0- Exciting current/ No load current Im- Magnetizing component ... equivalent of secondary terminal voltage ZL- Load impedance ZL ′- Primary equivalent of load impedance

381 views 2 answers

asked May 17, 2020 by anonymous

Single phase transformer

Single phase transformer
Last Answer : Single phase Transformer Transformer

261 views 1 answer

asked May 16, 2020 by anonymous

What is the use of transformer?

What is the use of transformer?
Last Answer : The use of transformer is to do lower or raise the voltage or currents in an electrical circuit. That's quite so simple.

159 views 1 answer

asked May 15, 2020 by anonymous

Transformer on DC

Write about transformer on DC.
Last Answer : Transformer on DC : Transformer cannot work on DC. Transformer works on electromagnetic induction principle. Electromagnetic induction principle means when flux linking with coil changes and EMF induced in it ... winding insulation will burn. https://youtu.be/TVp_0fIfxqY

248 views 1 answer

asked May 10, 2020 by anonymous

State any four characteristics of core type transformer.

State any four characteristics of core type transformer.
Last Answer : Characteristics of core type transformer: i) It has one window. ii) It has one magnetic circuit. iii) Core surrounds the winding. iv) Average length of core is more. v) Area of cross ... Better cooling for winding. vii) Mechnical strength is comparatively less. viii) Repair and maintenance is easy.

132 views 1 answer

asked Jul 27, 2019 by anonymous

Explain construction and working of single phase Auto transformer.

Explain construction and working of single phase Auto transformer.
Last Answer : Construction of single phase auto transformer: (i) It has only one winding wound on a laminated circular magnetic core. (ii) The core is made of silicon steel stampings. (iii) The two terminals of the ... help of handle. 5) The same transformer can be used as step-up or step down auto-transformer

345 views 1 answer

asked Jul 26, 2019 by anonymous