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

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Answer : The leakage flux in a transformer depends upon load current.

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

Answer : The value of flux involved in the e.m.f. equation of a transformer is maximum value.

Description : The path of magnetic flux in a transformer should have?

Answer : The path of magnetic flux in a transformer should have low reluctance.

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

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

Answer : The secondary of a current transformer is always short-circuited under operating conditions because it avoids core saturation and high voltage induction.

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 : Increasing the number of turns of wire on the secondary of a transformer will  (A) Decrease the secondary current (B) Increase the primary current (C) Have no effect on the secondary current (D) Increase the secondary current

Answer : Increasing the number of turns of wire on the secondary of a transformer will Decrease the secondary current 

Description : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary?  (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts

Answer : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary?  (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts

Description : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then  (A) zero sequence currents are present on both sides of the transformer  (B) ... side  (D) zero sequence currents are present on the primary side but not on the secondary side

Answer : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer 

Answer : The efficiency of transformer is Greater than electrical Machine because there is no rotational losses in transformer and there is no air gap losses in transformer so losses is less in transformer compare to electrical machine so efficiency is higher in case of 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 : 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 : 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. https://youtu.be/TVp_0fIfxqY

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

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

Answer : The power transformer is a constant main flux device.

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

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 : The transformer ratings are usually expressed in terms of kVA.

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 : 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.

Answer : A transformer oil must be free from moisture.

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

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

Answer : Star/star transformers work satisfactorily when load is balanced .

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