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Transformers

Study 132 Electrical Engineering MCQs with correct answers and explanations.

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111Electrical EngineeringMedium

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?

AIt is a step-up transformer

BIts rating is 2 kVA

CIts secondary voltage is 400 V

DIts secondary current is 5 A

EIts secondary current is 20 A

Correct answer

E. Its secondary current is 20 A

Explanation

The correct answer is Its secondary current is 20 A.

112Electrical EngineeringMedium

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

AOvercurrent protection

BBuchholz relay

CAll of the above

DOverfluxing protection

Correct answer

B. Buchholz relay

Explanation

The correct answer is Buchholz relay.

113Electrical EngineeringMedium

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________?

AR2IK2

BR22!K2

CR22/K

DR2/VK

Correct answer

A. R2IK2

Explanation

The correct answer is R2IK2.

114Electrical EngineeringMedium

No-load on a transformer is carried out to determine________?

Aefficiency of the transformer

Bmagnetising current

Cmagnetising current and loss

Dcopper loss

Correct answer

C. magnetising current and loss

Explanation

The correct answer is magnetising current and loss.

115Electrical EngineeringMedium

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

Asecondary voltage remains constant

Bpermeability of transformer core remains constant

Cvalue of transformation ratio remains constant

Dcore flux remains practically constant

Eprimary voltage remains constant

Correct answer

D. core flux remains practically constant

Explanation

The correct answer is core flux remains practically constant.

116Electrical EngineeringMedium

Primary winding of a transformer________?

Ais always a low voltage winding

Bcould either be a low voltage or high voltage winding

Cnone of the above

Dis always a high voltage winding

Correct answer

B. could either be a low voltage or high voltage winding

Explanation

The correct answer is could either be a low voltage or high voltage winding.

117Electrical EngineeringMedium

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?

AConservator

BBuchholz relay

CBreather

DBushings

Correct answer

A. Conservator

Explanation

The correct answer is Conservator.

118Electrical EngineeringMedium

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

Aeddy current loss will remain unchanged

Bnone of the above

Ceddy current loss will increase

Deddy current loss will decrease

Correct answer

A. eddy current loss will remain unchanged

Explanation

The correct answer is eddy current loss will remain unchanged.

119Electrical EngineeringMedium

The hum in a transformer is mainly attributed to________?

Aoil in the transformer

Bmagnetostriction

Cmechanical vibrations

Dload changes

Correct answer

B. magnetostriction

Explanation

The correct answer is magnetostriction.

120Electrical EngineeringMedium

Material used for construction of transformer core is usually________?

Aaluminium

Bsilicon steel

Cwood

Dcopper

Correct answer

B. silicon steel

Explanation

The correct answer is silicon steel.

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

Asecondary voltage remains constant

Bpermeability of transformer core remains constant

Cvalue of transformation ratio remains constant

Dcore flux remains practically constant

Eprimary voltage remains constant

Correct answer

D. core flux remains practically constant

Explanation

The correct answer is core flux remains practically constant.