Electrical Top 20 mcq

1➤ The short circuit test in a transformer is carried out:

Al half load currentAt full load currentAt very small load currentAt Greater than full load current

2➤ A small ______ in poly phase induction motor helps to reduce the magnetizing current.

Alter gapYokeInsulatorAir gap

3➤ Number of phases used for a load above 4 kW is:

4321

4➤ The Δ connection has the advantage of restricting the third harmonic components current to:

Within star connectionWithin both star and delta connectionsWithin delta connectionNeither star nor delta connections

5➤ In a transformer the leakage flux:

contributes to transfer of energy from primary to secondary contributes to transfer of energy from secondary to primarycontributes to transfer of energy between both coils simultaneously does not contribute to transfer of energy from primary to secondary

6➤ The current transformer’s used in differential protection of a star/delta transformer will be connected in the configuration of: A. B. C. D.

Delta connection on star side and star connection on delta side transformerDelta connection on both sides of transformerStar connection on both sides of transformerStar connection on star side and delta connection on delta side of transformer

7➤ The flux density affects:

Only core loss Neither hysteresis no eddy current lossOnly eddy current lossOnly hysteresis loss

8➤ Which of the following part of a transformer consists of a small vessel which contain a drying agent?

Oil tankConservatorBreatherWindings

9➤ The voltage regulation of a transformer having copper loss 1% of output and percentage reactance drop of 5% and power factor 0.9 lagging is _______:

3.08%3%-4.084.8%

10➤ Centrifugal Methods of reconditioning transformer oil is effective for removal of___

All options are correctdissolved gasessolid impurities water

11➤ Which of the following is not routine test on transformers?

Radio interference testPolarity testImpedance voltage test Core insulation voltage test

12➤ Which of the following is most likely source of harmonic in a transformer?

Loose connections Core saturationsOverloadPoor insulation

13➤ The ____ generator has poorest voltage regulation

ShuntSeriesCompoundOver-compound

14➤ The break test for the determination of efficiency of a D. C. machine is ____ :

a regenerative method None of thesea direct methodan indirect method

15➤ Inter-poles are used in ____

Both lap and wave wound machinesLap wound machinesWave wound machinesNone of these

16➤ A salient pole synchronous motor is running at no load. Its excitation is reduce to zero:

It will stopIt will loose synchronismIt will remain running at synchronous speed It is uncertain

17➤ When the synchronous motor is ________ it operates with leading power factor current

over-excitedcritically excited under-excitedheavily loaded

18➤ The regulation of a synchronous motor is

0.0101All of these

19➤ For 100% excitation in synchronous motor, the relationship between back emf E and applied voltage V is

E > VE≠VE = VE < V

20➤ A synchronous motor may fail to pull into synchronism owing to_____

Any of the optionshigh frictionlow excitationexcessive load

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