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

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

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Helical coils can be used on low voltage side of high kVA transformers.

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In a transformer the resistance between its primary and secondary should be?

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In a transformer the resistance between its primary and secondary should be infinity.

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The transformer ratings are usually expressed in terms of kVA.

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During short circuit test iron losses are negligible because?

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During short circuit test iron losses are negligible because the voltage applied on primary side is low.

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The transformer laminations are insulated from each other by thin coat of varnish.

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Reduction in core losses and increase in permeability are obtained with transformer employing?

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Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

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597 views 1 answer
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In a power or distribution transformer about 10 percent end turns are heavily insulated to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns.

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79 views 1 answer
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In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?

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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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126 views 1 answer
Description :

Explain the effect of Harmonics on the Transformer.

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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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60 views 1 answer
Description :

List two special feature of welding transformer.

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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42 views 1 answer
Description :

State two applications of isolation transformer

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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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28 views 1 answer
Description :

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

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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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35 views 1 answer
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Equivalent circuit of transformer

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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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265 views 2 answers
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Single phase transformer

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Single phase Transformer Transformer

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239 views 1 answer
Description :

What is the use of transformer?

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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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147 views 1 answer
Description :

Write about transformer on DC.

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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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237 views 1 answer
Description :

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

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Description :

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

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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117 views 1 answer
Description :

State any four characteristics of core type transformer.

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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82 views 1 answer
Description :

Explain construction and working of single phase Auto transformer.

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

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

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

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

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

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

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Description :

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

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

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

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Transformer breaths in when load on it decreases.

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

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

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

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The power transformer is a constant main flux device.

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

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

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The chemical used in breather is silica gel.

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

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Material used for construction of transformer core is usually silicon steel.

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

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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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A transformer oil must be free from moisture.

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Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds 150°C.

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

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Star/star transformers work satisfactorily when load is balanced .

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

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

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The leakage flux in a transformer depends upon load current.

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