Even at no-load, a transformer draws current from the mains. Why?
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115 views
0 answers
asked
Apr 28, 2020
by
anonymous

Last Answer : No-load current in a transformer lags behind the voltage by about 75°.
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90 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The no load current in a transformer lags behind the applied voltage by an angle of about 75°.
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188 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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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?
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.
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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?
Last Answer : In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.
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113 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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124 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be 400 W.
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149 views
1 answer
asked
Mar 19, 2018
by
anonymous
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Last Answer : An ideal transformer will have maximum efficiency at a load such that copper loss equal to iron loss.
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204 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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152 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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133 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The magnetising current of a transformer is usually small because it has small air gap.
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78 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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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?
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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107 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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130 views
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asked
May 22, 2020
by
anonymous

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
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154 views
1 answer
asked
May 22, 2020
by
anonymous

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.
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54 views
1 answer
asked
May 22, 2020
by
anonymous

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%.
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279 views
1 answer
asked
May 22, 2020
by
anonymous

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
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381 views
2 answers
asked
May 17, 2020
by
anonymous

Single phase transformer
Last Answer : Single phase Transformer Transformer
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261 views
1 answer
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May 16, 2020
by
anonymous

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.
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160 views
1 answer
asked
May 15, 2020
by
anonymous

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
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248 views
1 answer
asked
May 10, 2020
by
anonymous

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.
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181 views
1 answer
asked
Jul 27, 2019
by
anonymous

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.
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132 views
1 answer
asked
Jul 27, 2019
by
anonymous

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
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347 views
1 answer
asked
Jul 26, 2019
by
anonymous
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Last Answer : The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.
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205 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : In the transformer low voltage winding has got more cross-sectional area.
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256 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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351 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Primary winding of a transformer could either be a low voltage or high voltage winding.
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86 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : High voltage winding in a transformer has more number of turns.
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363 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The efficiency of a power transformer is of the order of 98 percent.
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100 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : In a transformer, routine efficiency depends upon load current and power factor of load.
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133 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The maximum efficiency of a distribution transformer is at 50% full load.
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141 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Transformer breaths in when load on it decreases.
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90 views
1 answer
asked
Mar 19, 2018
by
anonymous
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Last Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.
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546 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The power transformer is a constant main flux device.
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63 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : In a transformer, the tappings are generally provided on low voltage side.
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92 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The use of higher flux density in the transformer design reduces weight per kVA.
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126 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The chemical used in breather for transformer should have the quality of cleansing the transformer oil.
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187 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : An ideal transformer has infinite values of primary and secondary inductances. The statement is false.
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327 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The transformer ratings are usually expressed in terms of kVA.
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318 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Material used for construction of transformer core is usually silicon steel.
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241 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The thickness of laminations used in a transformer is usually 0.4 mm to 0.5 mm.
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98 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : conservator or a reservoir tank for insulating oil in transformer which used for balanced the onload oil level with help of oil level indicator which mount on middle part of reservoir tank.
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177 views
3 answers
asked
Mar 19, 2018
by
anonymous

Last Answer : A transformer oil must be free from moisture.
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68 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds 150°C.
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197 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The main reason for generation of harmonics in a transformer could be saturation of core.
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128 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Delta/star transformer works satisfactorily when on balanced as well as unbalanced loads.
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283 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The leakage flux in a transformer depends upon load current.
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316 views
1 answer
asked
Mar 19, 2018
by
anonymous
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Last Answer : Noise level test in a transformer is a type test.
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102 views
1 answer
asked
Mar 19, 2018
by
anonymous
