Interview Questions Answers in Electrical Engineering, Power Plant Engineering

Question { L&T, 4526 }

why dc motor runs slowly when dc supply is given?

Answer

If the voltage is normal ,the shunt motor runs slowly as the field current is kept at maximum value while starting .

Is This Answer Correct ?

2 Yes

1 No

Question { 3194 }

What is slip in induction motor?

Answer

It is the difference between the synchronous speed ( Ns) and actual speed of the rotor or rotor speed (Nr). It can be expressed in per minute ( Ns - Nr ,both being rpm ),per second or percentage ( Ns - Nr)x 100 /Ns .

Is This Answer Correct ?

2 Yes

0 No

Question { 2391 }

What is the multiplying factor if line ct ratio is 1000/1 and meter ct ratio is -/5 ?

Answer

You mean the meter is designed to give full / actual reading for CT ratio 1000/5 ? Then multiply by 5

Is This Answer Correct ?

0 Yes

2 No

Question { MRF, 3733 }

Why neutral shows voltage with earth ?

Answer

If it is in your house ,may be due to voltage drop in neutral conductor . It happens owing to unbalanced current or single phase line or current in neutral and neutral resistance is high

Is This Answer Correct ?

8 Yes

2 No

Question { International Mega Food Park Limited, 5503 }

what's interlock relay ?

Answer

It is a multi-armature relay with positions of armatures dependent on positions of other armatures i.e positions are interconnected

Is This Answer Correct ?

0 Yes

0 No

Question { 1907 }

how to find the transformer neutral copper earthing size

Answer

Should be able to take at least the full load current continuously

Is This Answer Correct ?

0 Yes

1 No

Question { KEC, 6142 }

According to ohms law voltage proportional to current, then why should current rating is low with high voltage rating in transformer?

Answer

Ohms law applies only to ' only resistance ' circuits . The ' No- load current' of a transformer is not equal to Voltage / impedance , but only a fraction

Is This Answer Correct ?

0 Yes

1 No

Question { 4032 }

Why current transformer is earthed??

Answer

To prevent probable electrical shock

Is This Answer Correct ?

3 Yes

0 No

Question { Torrent Power, 7068 }

(1) From the following option, which option is correct for largest size transformer.?
a)1KVA,25Hz , b)1KVA,50HZ , c)1KVA,60Hz , d)1KVA,100Hz

Answer

Back emf is equal to 4.44 flux x frequency x turns . For the given voltage if the frequency is reduced , flux should be increased and hence the larger core or more number of turns

Is This Answer Correct ?

10 Yes

0 No

Question { Physical Research Laboratory (PRL), 2897 }

Why induction motor overheated?

Answer

Inter turn short , over voltage , overload , bad cooling , bearing friction, unbalanced voltage ,....

Is This Answer Correct ?

2 Yes

0 No

Question { TATA, 8295 }

What is broken wire condition in transmission line?

Answer

Conductor is open or no continuity without earth fault

Is This Answer Correct ?

5 Yes

1 No

Question { Aurobindo, 3450 }

What happens if ac excitation is given to the field of an alternator

Answer

You get distorted wave form ,instead of sinusoidal

Is This Answer Correct ?

0 Yes

1 No

Question { 2605 }

What is the meaning of transformer 16 / 20 mva.

Answer

Normal cooling 16 MVA , better cooling 20 MVA

Is This Answer Correct ?

4 Yes

1 No

Question { 2977 }

under which situation or why restricted earth fault protection operates in out side its zone that is external fault

Answer

This may happen when bushing neutral ct is used for REF , as it is usually not identical to the line ct s

Is This Answer Correct ?

0 Yes

0 No

Question { 2655 }

explain(why) with circuit for pick up of restricted earth fault protection due to external fault

Answer

It may happen when NCT is not identical to line CTs

Is This Answer Correct ?

0 Yes

0 No

k.prakashchandra