Last Answer : The leakage flux in a transformer depends upon load current.
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Mar 19, 2018
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anonymous
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27] In a transformer, the leakage flux of each winding is proportional to the current in that winding because A. Ohm's law applies to magnetic circuits B. Leakage paths do no saturate C. the two windings are electrically isolated D. mutual flux is confined to the core
Last Answer : B. Leakage path do not saturate
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Last Answer : The use of higher flux density in the transformer design reduces weight per kVA.
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126 views
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Mar 19, 2018
by
anonymous

Last Answer : Power on primary and secondary side of transformer A. Remains Approximately constant B. Are always different C. Is always 100kVA D. None of these
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686 views
2 answers
asked
Mar 19, 2018
by
anonymous

The path of magnetic flux in a transformer should have?
Last Answer : The path of magnetic flux in a transformer should have low reluctance.
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368 views
1 answer
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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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324 views
1 answer
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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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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
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Mar 19, 2018
by
anonymous
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In a transformer the resistance between its primary and secondary should be?
Last Answer : In a transformer the resistance between its primary and secondary should be infinity.
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254 views
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Mar 19, 2018
by
anonymous

38] In a transformer the energy is conveyed from primary to secondary? A. Through cooling coil B. Through air C. By the flux D. None of the above
Last Answer : C. By the flux
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12] Which is not the basic element of the transformer? A. core B. primary winding C. secondary winding D. mutual flux
Last Answer : D. Mutual flux
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29.In transformer terminology, the ratio 20:1 indicates that A. there are 20 turns on primary one turn on secondary B. secondary voltage is 1/20th of the primary C. primary current is 20 times greater than the secondary current D. for every 0 turns on primary, there is one turn on secondary
Last Answer : A. there are 20 turns on primary one turn on secondary
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2 answers

28.In a two winding transformer, the emf /turn in secondary winding is always......the induced emf power turn in primary A. equal to k times B. equal to 1/k times C. equal D. greater than
Last Answer : C. equal
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The frequency of the secondary voltage of a transformer will be..... A. less than frequency of the primary voltage B. equal to the primary voltage C. greater than the frequency of the primary voltage D. much greater than the frequency of the primary voltage
Last Answer : B. Equal to the primary voltage
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241 views
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How is magnetic leakage reduced to a minimum in commercial transformers?
Last Answer : By interleaving the primary and secondary windings.
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1 answer

How the leakage reactance of the transformer is reduced?
Last Answer : In transformers the leakage reactance is reduced by interleaving the high voltage and low voltage winding.
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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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127 views
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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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148 views
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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
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May 22, 2020
by
anonymous
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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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270 views
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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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2 answers
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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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159 views
1 answer
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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
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Even at no-load, a transformer draws current from the mains. Why?
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114 views
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Apr 28, 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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179 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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asked
Jul 26, 2019
by
anonymous
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Last Answer : No-load current in a transformer lags behind the voltage by about 75°.
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90 views
1 answer
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Mar 19, 2018
by
anonymous

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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203 views
1 answer
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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
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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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344 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
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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
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Mar 19, 2018
by
anonymous

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

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

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

Last Answer : Transformer breaths in when load on it decreases.
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90 views
1 answer
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Mar 19, 2018
by
anonymous
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Last Answer : No-load current of a transformer has small magnitude and low power factor.
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1 answer
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Mar 19, 2018
by
anonymous

Last Answer : Spacers are provided between adjacent coils to provide free passage to the cooling oil.
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238 views
1 answer
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Mar 19, 2018
by
anonymous

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
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Mar 19, 2018
by
anonymous

Last Answer : The power transformer is a constant main flux device.
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63 views
1 answer
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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
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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 : The chemical used in breather is silica gel.
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87 views
1 answer
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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
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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
