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

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

Answer : Iron loss of a transformer can be measured by low power factor wattmeter.

Description : Can a Single Phase Transformer be used on a Three Phase source?

Answer : Yes. Any single phase transformer can be used on a three phase source by connecting the primary leads to any two wires of a three phase system, regardless of whether the source is three phase 3-wire or three phase 4-wire. The transformer output will be single phase.

Answer : A transformer can have regulation closer to zero on leading power factor.

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

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

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

Answer : The chemical used in breather is silica gel.

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

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

Answer : The core used in high frequency transformer is usually air core .

Answer : Silicon steel used in laminations mainly reduces hysteresis loss.

Answer :  Sandwich type winding is used in 3 phase shell-type transformer.

Description : Explain the effect of Harmonics on the Transformer.

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.

Description : Write about transformer on DC.

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.

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

Description : The size of a transformer core will depend on?

Answer : The size of a transformer core will depend on frequency and area of the core.

Description : An open-circuit test on a transformer is conducted primarily to measure?

Answer : The open-circuit test in a transformer is used to measure

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

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

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

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

Description : Sumpner's test is conducted on transformer to determine?

Answer : Sumpner's test is conducted on transformer to determine temprature.

Answer : A transformer oil must be free from moisture.

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

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

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

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.

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

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

Description : The dielectric strength of transformer oil is expected to be?

Answer : The dielectric strength of transformer oil is expected to be 33 kV.

Description : Can transformers be used in parallel?

Answer : Single phase transformers can be used in parallel only when their impedances and voltages are equal. If unequal voltages are used, a circulating current exists in the closed network between ... listed above, plus the angular displacement and phasing between the two transformers must be identical.

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

Description : State two applications of isolation transformer

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.

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

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%.

Description : Equivalent circuit of transformer

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

Description : Single phase transformer

Answer : Single phase Transformer Transformer

Description : What is the use of transformer?

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

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

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.

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.

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

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

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

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

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.

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

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

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

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

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

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

Answer : Transformer breaths in when load on it decreases.

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

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

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