During open circuit test of a transformer

Which of the following does not change in a transformer ?

In a transformer the energy is conveyed from primary to secondary

A transformer core is laminated to

The degree of mechanical vibrations produced by the laminations of a transformer depends on

The no-load current drawn by transformer is usually what per cent of the full-load current ?

The path of a magnetic flux in a transformer should have

No-load on a transformer is carried out to determine

The dielectric strength of transformer oil is expected to be

Sumpner’s test is conducted on trans-formers to determine

The permissible flux density in case of cold rolled grain oriented steel is around

The efficiency of a transformer will be maximum when

No-load current in a transformer

The purpose of providing an iron core in a transformer is to

Which of the following is not a part of transformer installation ?

While conducting short-circuit test on a transformer the following side is short circuited

In the transformer following winding has got more cross-sectional area

A transformer transforms

A transformer cannot raise or lower the voltage of a D.C. supply because

Primary winding of a transformer

Which winding in a transformer has more number of turns ?

Efficiency of a power transformer is of the order of

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

A common method of cooling a power transformer is

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

In a transformer routine efficiency depends upon

In the transformer the function of a conservator is to

Natural oil cooling is used for transformers up to a rating of

Power transformers are designed to have maximum efficiency at

The maximum efficiency of a distribution transformer is

Transformer breaths in when

No-load current of a transformer has

Spacers are provided between adjacent coils

Greater the secondary leakage flux

The purpose of providing iron core in a step-up transformer is

The power transformer is a constant

Two transformers operating in parallel will share the load depending upon thei

If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be

What will happen if the transformers working in parallel are not connected with regard to polarity ?

If the percentage impedances of the two transformers working in parallel are different, then

In a transformer the tappings are generally provided on

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

The chemical used in breather is

The transformer ratings are usually expressed in terms of

The noise resulting from vibrations of laminations set by magnetic forces, is termed as

Material used for construction of transformer core is usually

The thickness of laminations used in a transformer is usually

The function of conservator in a transformer is

In a transformer the resistance between its primary and secondary is

A transformer oil must be free from

A Buchholz relay can be installed on

Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds

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

Distribution transformers are generally designed for maximum efficiency around

Star/star transformers work satisfactorily when

Delta/star transformer works satisfactorily when

Buchholz’s relay gives warning and protection against

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

Which of the following does not change in an ordinary transformer ?

Which of the following properties is not necessarily desirable for the material for transformer core ?

The leakage flux in a transformer depends upon

The path of the magnetic flux in transformer should have

Noise level test in a transformer is a

Which of the following is not a routine test on transformers ?

A transformer can have zero voltage regulation at

Helical coils can be used on

Harmonics in transformer result in

The core used in high frequency transformer is usually

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

4. The value of flux involved m the e.m.f. equation of a transformer is

5. Silicon steel used in laminations mainly reduces

Which winding of the transformer has less cross-sectional area ?

Power transformers are generally designed to have maximum efficiency around

. Which of the following is the main advantage of an auto-transformer over a two winding transformer ?

During short circuit test iron losses are negligible because

Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in

The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer

An ideal transformer is one which has

When a given transformer is run at its rated voltage but reduced frequency, its

In an actual transformer the iron loss remains practically constant from noload to fullload because

An ideal transformer will have maximum efficiency at a load such that

If the supply frequency to the transformer is increased,”the iron loss will

Negative voltage regulation is indicative that the load is

Iron loss of a transformer can be measured by

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

Which type of winding is used in 3phase shell-type transformer ?

Open circuit test on transformers is conducted to determine

Short circuit test on transformers is conducted to determine

For the parallel operation of single phase transformers it is necessary that they should have

The transformer oil should have _____ volatility and _____ viscosity.

The function of breather in a transformer is

The secondary winding of which of the following transformers is always kept closed ?

The size of a transformer core will depend on

. N atural air coo ling is generally restricted for transformers up to

. A shell-type transformer has

. A transformer can have regulation closer to zero

. A transformer transforms

. Which of the following is not the standard voltage for power supply in India ?

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

. In a power or distribution transformer about 10 per cent end turns are heavily insulated

. For given applied voltage, with the increase in frequency of the applied voltage

. Losses which occur in rotating electric machines and do not occur in trans formers are

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

. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect ?

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

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

. A good voltage regulation of a transformer means

. For a transformer, operating at constant load current, maximum efficiency will occur at

. Which of the following protection is normally not provided on small distribution transformers ?

. Which of the following acts as a protection against high voltage surges due to lightning and switching ?

. The efficiency of two identical transformers under load conditions can be determined by

. Which of the following insulating materials can withstand the highest temperature safely ?

. Which of the following parts of a transformer is visible from outside ?

. The noise produced by a transformer is termed as

. Which of the following loss in a transformer is zero even at full load ?

. Which of the following is the most likely source of harmonics in a transformer ?

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

. The hum in a transformer is mainly attributed to

. The maximum load that a power transformer can carry is limited by its

. The efficiency of a transformer, under heavy loads, is comparatively low because

. An open-circuit test on a transformer is conducted primarily to measure (f) none of the above

. A no-load test is performed on a transformer to determine

. The voltage transformation ratio of a transformer is equal to the ratio of

. Part of the transformer which is most subject to damage from overheating is

. If a transformer is switched on to a voltage more than the rated voltage

. Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is

. Minimum voltage regulation occurs when the power factor of the load is

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

. The efficiencies of transformers compared with that of electric motors of the same power are (6) much smaller