Answer :
The transformer laminations are insulated from each other by thin coat of varnish.
asked
Mar 19, 2018
by
anonymous
Answer :
The core used in high frequency transformer is usually air core .
asked
Mar 19, 2018
by
anonymous
Answer :
Silicon steel used in laminations mainly reduces hysteresis loss.
Answer :
Material used for construction of transformer core is usually silicon steel.
asked
Mar 19, 2018
by
anonymous
Answer :
The transformer ratings are usually expressed in terms of kVA.
asked
Mar 19, 2018
by
anonymous
Answer :
The magnetising current of a transformer is usually small because it has small air gap.
asked
Mar 19, 2018
by
anonymous
Answer :
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds 150°C.
asked
Mar 19, 2018
by
anonymous
Answer :
The chemical used in breather for transformer should have the quality of cleansing the transformer oil.
asked
Mar 19, 2018
by
anonymous
Answer :
Sandwich type winding is used in 3 phase shell-type transformer.
asked
Mar 19, 2018
by
anonymous
Answer :
The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a two-phase winding.
asked
Mar 21, 2018
by
anonymous
Answer :
No-load current in a transformer lags behind the voltage by about 75°.
asked
Mar 19, 2018
by
anonymous
Answer :
The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.
asked
Mar 19, 2018
by
anonymous
Answer :
High voltage winding in a transformer has more number of turns.
asked
Mar 19, 2018
by
anonymous
Answer :
The no load current in a transformer lags behind the applied voltage by an angle of about 75°.
asked
Mar 19, 2018
by
anonymous
Answer :
In a transformer, routine efficiency depends upon load current and power factor of load.
asked
Mar 19, 2018
by
anonymous
Answer :
The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.
asked
Mar 19, 2018
by
anonymous
Answer :
In a transformer, the tappings are generally provided on low voltage side.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
Answer :
The main reason for generation of harmonics in a transformer could be saturation of core.
asked
Mar 19, 2018
by
anonymous
Answer :
The leakage flux in a transformer depends upon load current.
asked
Mar 19, 2018
by
anonymous
Answer :
Noise level test in a transformer is a type test.
asked
Mar 19, 2018
by
anonymous
Answer :
The value of flux involved in the e.m.f. equation of a transformer is maximum value.
Answer :
The function of breather in a transformer is to arrest flow of moisture when outside air enters the transformer.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
Description : The hum in a transformer is mainly attributed to?
Answer :
The hum in a transformer is mainly attributed to magnetostriction.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
Description : The path of magnetic flux in a transformer should have?
Answer :
The path of magnetic flux in a transformer should have low reluctance.
asked
Mar 19, 2018
by
anonymous
Answer :
In the transformer low voltage winding has got more cross-sectional area.
asked
Mar 19, 2018
by
anonymous
Answer :
Transformer breaths in when load on it decreases.
asked
Mar 19, 2018
by
anonymous
Answer :
The use of higher flux density in the transformer design reduces weight per kVA.
asked
Mar 19, 2018
by
anonymous
Answer :
In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
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%.
asked
May 22, 2020
by
anonymous
Description : Even at no-load, a transformer draws current from the mains. Why?
asked
Apr 28, 2020
by
anonymous
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.
asked
Jul 27, 2019
by
anonymous
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.
asked
Mar 19, 2018
by
anonymous
Answer :
Primary winding of a transformer could either be a low voltage or high voltage winding.
asked
Mar 19, 2018
by
anonymous
Answer :
The efficiency of a power transformer is of the order of 98 percent.
asked
Mar 19, 2018
by
anonymous
Answer :
The maximum efficiency of a distribution transformer is at 50% full load.
asked
Mar 19, 2018
by
anonymous
Answer :
No-load current of a transformer has small magnitude and low power factor.
asked
Mar 19, 2018
by
anonymous
Answer :
The power transformer is a constant main flux device.
asked
Mar 19, 2018
by
anonymous
Answer :
A transformer oil must be free from moisture.
asked
Mar 19, 2018
by
anonymous
Answer :
The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be 400 W.
asked
Mar 19, 2018
by
anonymous
Answer :
When a given transformer is run at its rated voltage but reduced frequency, its core flux density is increased.
asked
Mar 19, 2018
by
anonymous
Answer :
An ideal transformer will have maximum efficiency at a load such that copper loss equal to iron loss.
asked
Mar 19, 2018
by
anonymous
Answer :
Iron loss of a transformer can be measured by low power factor wattmeter.
asked
Mar 19, 2018
by
anonymous