Interview Questions Answers in Electrical Engineering

Question { Ericsson, 5287 }

if the supply voltage increased by N times, the x-section of
conductor will be.........

Answer

X-sectional area depends only on current ,not voltage

Is This Answer Correct ?

1 Yes

0 No

Question { 3939 }

what is the benift of HT metering & LT metering

Answer

HT metering includes transformer losses also

Is This Answer Correct ?

0 Yes

1 No

Question { 4237 }

current cyring capacity of .75sqmm copper cable

Answer

current capacity of copper can be taken as 2.5 A/sq mm but
for generators it is taken as 1.5 A/sq mm.For duration of
less than 4 hours 6A/sq mm

Is This Answer Correct ?

1 Yes

1 No

Question { 7646 }

if we increase the frequency given to a transformer then wat
will happen to the transformer size, whether it will increase?

Answer

It will reduce as less flux is required to build the same back emf which is equal to 4.44 x flux x frequency x turns

Is This Answer Correct ?

0 Yes

0 No

Question { 2487 }

what is V=4.44FBN, THIS 4.44 ONLY U GOT the voltage in
term sof 11, 22 etc this 4.44 u will get from form factor
which has a value of 1.11

Answer

Average voltage is converted to peak value by multiplying by the form factor

Is This Answer Correct ?

0 Yes

0 No

Question { 3924 }

Why Earthin is not required in Xformer primary side when it
is in Star / star?

Answer

Eatrthing primary neutral of star/star Tr at the receiving
end is of no use for protection and safety . At sending end
neutral is earthed and it is sufficient.

Is This Answer Correct ?

1 Yes

1 No

Question { 4080 }

Why ELCB trip, when neutral touch with ground?

Answer

It is RCCB . when neutral touches the ground , a portion of
neutral current flows through the ground also,creating
current imbalance in RCCB

Is This Answer Correct ?

1 Yes

0 No

Question { 3310 }

directional relay is typically used to respond in fault
condition who it can be used just as reverse power
protection which purely senes direction reversal to operate
a circuit breaker?

Answer

In other words ,directional relay is employed for
tranmission lines when there are two or more parallel
feeders ,so that the heathy feeder does not trip due to the
fault in another feeder.It is also used when the
tranformers are in parallel operation to prevent reverse
power ,when the secondaries are in prallel

Is This Answer Correct ?

0 Yes

1 No

Question { Schneider, 4174 }

Why the meters sonnected to metering core of CT are not
damagedon event of a fault??? Explain the phenomena??

Answer

The iron core of metering CT is smaller compared to that of
protection scheme, for accuracy. Its core reaches magnetic
saturation , if the current exceeds the rated value by a
certain value. After the saturation is reached, the
secondary current wii not incease with the primary
current .

Is This Answer Correct ?

3 Yes

0 No

Question { APGenco, 2903 }

why the transformer is not operates on two phase?

Answer

You can use another phase for neutral as in welding machine .

Is This Answer Correct ?

0 Yes

1 No

Question { Bhel, 5358 }

what is relay multiplier

Answer

It is an auxliary relay to have multiple make or break or
both contacts on operation of a single relay.

Is This Answer Correct ?

2 Yes

3 No

Question { 3054 }

Please describe HT and LT?

Answer

LT means voltage up to 250 V (medium 650V) HT -up to 33000V
as per IE Rules 1956

Is This Answer Correct ?

1 Yes

1 No

Question { Siemens, 5217 }

why anti pumping relay is not given to tripping coil of the
breaker? why only to closing coil?

Answer

Closing is on command and tripping is either on command or
auto .You are testing the circuit by closing the CB using
the control switch

Is This Answer Correct ?

0 Yes

0 No

Question { 3017 }

What is the advisble power factor to be maintained in grid
connecting power generation plnats without any effecting
the generator.

Answer

0.95 to 0.98 lag

Is This Answer Correct ?

1 Yes

1 No

Question { 3024 }

Genreally distribution transformers are having Star/delta
connections to provide phase and neutral to the consumers.
Is the neutral of the star conncted secondary grounded in
these transformers?

Answer

Yes. To prevent neutral shifting,to provide protection and
to make earth wire useful

Is This Answer Correct ?

0 Yes

1 No

k.prakashchandra