Electrical Engineering · Question Bank

Transformers

110 of 258 questions match · page 5 of 6. Answer in your head first, then check the solution.

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#81📘 EE Pocket Reviewer RojasEasy

Which one is a method of cooling used in a transformer rated 5 kVA or less?

AOil cooled

BNatural air cooled

CHydrogen cooled

DWater cooled

#82📘 EE Pocket Reviewer RojasEasy

Tappings in a transformer are provided where?

AAt the phase end of the high voltage side

BAt the middle of the high voltage side

CAt the neutral end of the high voltage side

DAt the phase end of the low voltage side

#83📘 EE Pocket Reviewer RojasEasy

Which of the following is defined as the “voltage transformation ratio”of a transformer?

ARatio of secondary induced emf to primary induced emf

BRatio of secondary terminal voltage to primary applied voltage

CRatio of primary turns to secondary turns

DRatio of secondary current to primary current

#84📘 EE Pocket Reviewer RojasEasy

At no load, the primary input is approximately equal to the iron loss. Why?

AThe primary current is small

BThe secondary current is small

CBoth the primary and secondary currents are small

DThe transformer has no output

#85📘 EE Pocket Reviewer RojasEasy

If the impedance triangle of two transformers operating in parallel are not identical in shape and size, which of the following is true?

AThe two transformers will share the load equally

BThe two transformers will get overheated

CThe two transformers will run with different pf

DThe two transformers will have a circulating current even when unloaded

#86📘 EE Pocket Reviewer RojasEasy

What is an ideal transformer?

AA transformer that does not work

BA transformer that has only one winding

CA transformer whose primary and secondary windings are equal in turns

DA transformer that has no losses and leakage reactance

#87📘 EE Pocket Reviewer RojasEasy

What is the normal range of the efficiency of a transformer?

A90 to 98%

B80 to 90%

C70 to 80%

D60 to 70%

#88📘 EE Pocket Reviewer RojasEasy

Which one is a purpose of cooling transformers?

ATo reduce the humming sound

BTo reduce the losses

CTo increase the efficiency

DTo dissipate the heat generated in the windings

#89📘 EE Pocket Reviewer RojasEasy

During the short circuit test, which winding is short circuited?

APrimary windings

BLow voltage windings

CSecondary windings

DHigh voltage windings

#90📘 EE Pocket Reviewer RojasEasy

Under what type of load pf will a transformer have a negative voltage regulation?

AUnity pf

BLagging pf

CLeading pf

DZero pf

#91📘 EE Pocket Reviewer RojasEasy

Which one will reduce the eddy current loss in a transformer?

ABy increasing the thickness of core laminations

BBy decreasing the thickness of core laminations

CBy using higher gage wires in the windings

DBy decreasing the air gap in the magnetic circuit

#92📘 EE Pocket Reviewer RojasEasy

What is the usual secondary current rating of a current transformer used for meters and relays?

A5 A

B10 A

C1 A

D100 A or more

#93📘 EE Pocket Reviewer RojasEasy

What is common to the two windings in a transformer?

AMagnetic circuit

BNumber of turns

CElectric current

DVoltage induced

#94📘 EE Pocket Reviewer RojasEasy

During the short circuit test, the iron loss of a transformer is negligible. Why?

AThe entire input power is just enough to meet the copper losses

BThe iron losses becomes totally saturated

CSupply frequency is held constant

DThe flux produced is only a small fraction of the normal flux

#95📘 EE Pocket Reviewer RojasEasy

Which one is a reason why dust particles should never be allowed to accumulate on the windings and core on a dry-type transformer?

AIt will tend to corrode the metal surface

BIt will reduce dissipation of heat

CIt will absorb oil and grease

DIt may short circuit the windings

#96📘 EE Pocket Reviewer RojasEasy

In an autotransformer, how does the primary and secondary windings coupled?

AMagnetically coupled only

BElectrically coupled only

CBoth magnetically and electrically coupled

DNo coupling necessary

#97📘 EE Pocket Reviewer RojasEasy

What will happen to the eddy current loss of a transformer when its load is increased?

AIt will increase

BIt will decrease

CIt will remain the same

DNone of these

#98📘 EE Pocket Reviewer RojasEasy

Which of the following can be altered by a transformer?

AFrequency

BPower

CDemand factor

DVoltage

#99📘 EE Pocket Reviewer RojasEasy

What is the most common method of cooling a power transformer?

ANatural air cooling

BForced-air cooling

COil cooling

DSpecial gas cooling

#100📘 EE Pocket Reviewer RojasEasy

The core of a transformer are made from laminations of which of the following metal sheets?

ALow carbon steel

BSilicon steel

CChrome steel

DMedium carbon steel

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