Interview Questions Answers in Electrical Engineering

what is impedence voltage

Answer

It is the voltage drop at the terminals, at the rated current due to impedance of the transformer = IZ

Is This Answer Correct ?

2 Yes

0 No

two TG running in parallel at equal load.one TG CB tripped
in reverse power relay.after tripping found its excitation
was on & turbine running at rated speed.Please clearify why
that TG tripped in reverse power ?

Answer

You have not mentioned whether there was increase in speed of the tripped TG. If not, at the time of tripping the load on it was zero or it was running as a motor .

Is This Answer Correct ?

0 Yes

0 No

Question { KSEB, 5312 }

Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on
External earth fault REF relay trips along with earth fault
relay.The REF relay has no complant as we tested relay.Why is
it happening?

Answer

Also may be due to 1 .reverse connection of NCT leads ( Unbalanced current of lines and NCT current add to each other ). 2. Low saturation point of NCT as Kv of bushing NCT is usually less than that of line CTs

Is This Answer Correct ?

0 Yes

0 No

Question { 96980 }

1 Kva = How many HP

Answer

KVA is apparent power . It is equal to zero HP if the pf is zero. KVA X pf / 0.736 = HP

Is This Answer Correct ?

17 Yes

9 No

Question { GE, 3420 }

why trip circuit supervision is taking through breaker contact? what happen if takendirectly?

Answer

TSR is for beaker trip circuit

Is This Answer Correct ?

0 Yes

0 No

Question { 4783 }

A 40 kva transformer has a core loss of 400W and a full load
copper loss of 800W. What is The proportion of full load at
maxmimum efficiency?

Answer

1 /root 2

Is This Answer Correct ?

5 Yes

1 No

Question { TNEB Tamil Nadu Electricity Board, 9496 }

in one substation we have two power transformers of
100mva,75mva capacity.statoin load is155mva.how much each
tranformers share the load????

Answer

The load sharing will be in the inverse ratio of percentage
impedances. Lower the % impedance higher the load ,so that
the voltage drops are equal. .

Is This Answer Correct ?

0 Yes

0 No

Question { MEIL, 4672 }

how to find the ballast lost from the actual wattage? for
example i am going to buy decorative type 2x36watts
fluorescent light fitting for this lamp how to find the
ballast lost? is there any formula?

Answer

Equal to I^2xR ( resistance of ballast )

Is This Answer Correct ?

0 Yes

0 No

Question { 2086 }

what is ten delta test? what is the significanse of it

Answer

When the insulation is perfect ,only capacitive ( Ic) current is present . Due to deterioration of insulation ,there will be resistance and hence resistive current( Ir ). Ir/ Ic is tan delta

Is This Answer Correct ?

0 Yes

1 No

Question { 2028 }

WHICH SUPPLY IS BETTER FOR 4 MW LOAD.
1)TO TAKE NEARER AVAILABLE 11 KV SUPPLY OR
2)TO TAKE 33 KV SUPPLY WHICH IS AVAILABLE AT 10 KM DISTANCE
BY INVESTING NEARLY 50-60 LACKHS

Answer

Availing supply from nearby 11 KV line ,does not make it a dedicated supply as there are many dist trs on it and VR may exceed the limit for 4 MW. You can expect frequent power failures . Reconductoring may also be necessitated

Is This Answer Correct ?

0 Yes

0 No

Question { DLF, 1983 }

in three 3.5 core aluminium ug cable. one cable is used for
one phase by shrting R,Y and B wires and other 2 cables
used for Y and b phases. balace 3 neutral wires are made
common and connected to load. suddenly neutral current was
more than line current what is the reason behind this?

Answer

The neutral current becomes more than the line current when the voltages applied to balanced 3 phase load , are not equal

Is This Answer Correct ?

0 Yes

0 No

Question { 3687 }

In directional earth fault protection for generator, one
core balance CT is for residual current, what other CT is
for, which is placed on neutral?

Answer

For balancing the unbalanced current of the phases . If
there is balancing ,there is no earth fault within the gen

Is This Answer Correct ?

0 Yes

1 No

Question { TNEB Tamil Nadu Electricity Board, 4028 }

for a slip ring induction motor if the stator is short
circuited and rotor is given supply? how does the rotor
rotate?

Answer

Just like squirrel cage induction motor with armature as stator

Is This Answer Correct ?

3 Yes

1 No

Question { 3875 }

why names such like dog ,rabbit, osprey,ant are used for
conductors.

Answer

According to normal size

Is This Answer Correct ?

2 Yes

0 No

Question { Accenture, 19430 }

if a 3 point starter is not available, how can a dc motor be
started?

Answer

Use a rheostat of correct rating

Is This Answer Correct ?

51 Yes

0 No

k.prakashchandra