# The transformer ratings are usually expressed in terms of?

The transformer ratings are usually expressed in terms of kVA.

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Description : The rating of transformer may be expressed in ____________.  (A) kVAR (B) kW (C) kVA (D) Horse power

Answer : The rating of transformer may be expressed in kVA .

Description : Why Transformer rating is given in kVA?

Answer : 1) The output of transformer is limited by heating due to the losses. Two types of losses in the transformer (i) Iron loss, (ii) Copper loss. 2) Iron loss depends on the transformer voltage (V). ... by load power factor. - Hence the transformer output is expressed in VA or kVA and not in kW.

Description : Define kVA rating of transformer.

Answer : kVA rating of transformer is defined as the product of voltage (V) and current (I) on primary side of transformer or secondary side of transformer divided by 1000. On both side the VA rating remains ... Mathematically kVA rating is given by, kVA rating of transformer = V1I1/1000 =V2I2/1000

Description : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be :  (A) 34.64 kVA (B) 75 kVA (C) 20 kVA (D) None of the above

Answer : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be : 34.64 kVA

Answer : The fuse rating is expressed in terms of current.

Description : Boiler rating is usually defined in terms of  (1) Maximum temperature of steam in Kelvin (2) Heat transfer rate in KJ/hr (3) Heat transfer area in metre2 (4) Steam output in kg/hr

Answer : Boiler rating is usually defined in terms of Steam output in kg/hr

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

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

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

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

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

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

Answer : 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.

Description : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?

Answer : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses.

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

Answer : The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a two-phase winding.

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

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

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

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

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

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

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

Answer : Noise level test in a transformer is a type test.

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

Description : In an actual transformer the iron loss remains practically constant from no load to full load because?

Answer : In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.

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

Answer : The function of breather in a transformer is to arrest flow of moisture when outside air enters the transformer.

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 : If a transformer is continuously operated the maximum temperature rise will occur in?

Answer : If a transformer is continuously operated the maximum temperature rise will occur in windings.

Description : The hum in a transformer is mainly attributed to?

Answer : The hum in a transformer is mainly attributed to magnetostriction.

Description : In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of?

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.

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

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

Description : what do not change in transformer?

Answer : Frequency and power are constant in transformers. Suppose we apply 50 Hz input frequency then the output frequency will also be 50 Hz whether the transformer is step up or step down. Similar ... is decreased on secondary side and hence power on primary side and secondary side remains constant.

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?

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