Interview Questions Answers in Electrical Engineering

Questions / { binay agarwal }

Questions Answers Category Views Company eMail

what happen ,if generator will generate leading power factor?

CD, NTPC,

6 Electrical Engineering 15273

WHY WE DO NOT TAKE THE POWER FACTOR MORE NEARER TO UNITY IN AC GENERATOR?

1 Electrical Engineering 3531

Answers / { binay agarwal }

Question { GAIL, 24177 }

In step down transformer (415/200V),mistakenly secondary
side is connected to 415V for some hours, what would be
result of this condition?

Answer

if Secondary puts 415v, than primary wants to take the
voltage upto 850v, & it can burn the winding of the
transformer.

Is This Answer Correct ?

3 Yes

1 No

Question { L&T, 60276 }

what is the difference between power and distribution
transformer?

Answer

power trafo is generally step up transformer,
distribution trafo is step down.

Is This Answer Correct ?

4 Yes

27 No

Question { 8388 }

why nearly all voltages are in the multiples of 11?

Answer

It has been assumed initially that the generating voltage
will reduce there voltage during transmission by nearly 10%,
so we started the generation in multiple of 11, but it was
not so large amount of losses, but it was being a trend, &
it is continue.

Is This Answer Correct ?

5 Yes

4 No

Question { IOCL, 8497 }

WHAT IS THE DIFFERENCE B/WDYNAMO&ALTERNATOR?

Answer

i wd like to say to "ranga" that, its not necessary that
alternator is independent of load,
in generator side ,there
is two mode- 1st is speed mode,
another- load mode.
in speed mode, at constant input, speed is fixed,
in load mode, load is constant at fixed input.
rest of all is true.

Is This Answer Correct ?

0 Yes

1 No

Question { Toyota, 26540 }

How does MCB operate without relay..?

Answer

MCB contains metallic conductor, which expand during over
curren or voltage, so the nc becomes no, & the MCB operates.

Is This Answer Correct ?

1 Yes

5 No

Question { Nesma, 17656 }

How to select the Cable size for 550 Amps Load without
seeing the cable Catalogue?

Answer

generally, for low rating full load current should be 3
times for aluminium cable, & 4 times for copper cable.
so, here 550/4=137.5 sq mm,
also 550/3=183.33 sq mm.
but this is for low rating, in high rating ratio is
decrease,
i.e. for copper 550/3= 183.33 sqmm
& for aluminium 550/2= 275 sq mm.

Is This Answer Correct ?

5 Yes

11 No

Question { 5072 }

how electronic energy meter works?

Answer

Energymeter uses by the transducer, as itis change energy
one form to another.

Is This Answer Correct ?

2 Yes

1 No

Question { 4330 }

In generation,transmission and distribution voltage
frequency is either 50HZ or 60 HZ;why are only these
frequencies?

Answer

if we give approx 1500rpm to stator, only that case good
induction is covered, & the winding is of genetrally 4 pole.
so according to N=120f/P,
Frequency should be around 50-60HZ.

Is This Answer Correct ?

9 Yes

4 No

Question { 12386 }

Why Parallel operation of two Transformer are Required?

Answer

after parallisation of trafo.,we can give a stable voltage
to the load, also if there is any probelem in any trafo. ,
than we can transfer all the the load to the another .

Is This Answer Correct ?

8 Yes

7 No

Question { 9241 }

What is the function of induction motor when low voltage is
apply.

Answer

motor speed will gradually down, but at below half of the
full voltage, winding can burn.

Is This Answer Correct ?

17 Yes

11 No

Question { CTS, 38628 }

why the tapping of transformer on ht side??????

Answer

in hv side, current will be less; so if we vary the
rheostate, than thetre is less arcing with respect to lv
side, so we always put the tap changer in hv side.

Is This Answer Correct ?

41 Yes

2 No

Question { NTPC, 16574 }

In a Synchronous generator, Can AC voltage be used instead
of DC voltage in field winding of rotor to produce AC power?

Answer

no, if we supply the ac current in rotor side, then non-
uniform ac will generate, which is not good.

Is This Answer Correct ?

5 Yes

11 No

Question { 9182 }

what is meant by VFD ?where its useful ?

Answer

VFD stands for 'variable frequency drive'.
Generally its speed is control by the input frequency,
For example in induction motor, VFD used.

Is This Answer Correct ?

6 Yes

0 No

Question { 7734 }

How to calculate the cable size in sq. mm. when the load is
given in KW?

Answer

For LT motors,
For copper,current carring capacity is 4 times of there
cross section area,
For aluminium,current carring capacity is 3 times of area.
This ratio will continuously decrease as we will go to HT
side motors.

Is This Answer Correct ?

0 Yes

8 No