Interview Questions Answers in Electrical Engineering

Questions / { vikramsenareddy }

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Answers / { vikramsenareddy }

Question { 3174 }

Upto what extend the powerfactor of a supply system can be
improved to be cost effective?

Answer

we can increase upto 0.988

Is This Answer Correct ?

8 Yes

0 No

Question { 6499 }

How i can identify the 220V and 110V power supply equipment?
No tag number.

Answer

for blind if equipment is made in USA, JAPAN, KOREA that
should operate on 110/220v.

Is This Answer Correct ?

2 Yes

14 No

Question { 11213 }

I have installed capacitor bank at secondary transformer.
cos phi is increase. but on load (far from transormer), it
still poor. Can anybody explain it??

Answer

first a fall caluclate the reactive power. after that
according to reactive power caluclate requied capacitor to
be arrange then u will increase power factor.

kVAr = KW {tan(cos^-1 Phi e) - tan(Cos^-1 Phi d)}

Where - Phi e = existing Power Factor.
Phi d = Desired Power Factor.

Is This Answer Correct ?

2 Yes

4 No

Question { Jindal, 41469 }

What happen if LV supply is fed to a HT motor?

Answer

motor winding will fail under low voltage.

Is This Answer Correct ?

16 Yes

58 No

Question { 18590 }

Wat wil happen if Transformer is operated at 100 HZ
Frequency?

Answer

as per EMF equation of the trasformer frequency is directly
proportional to winding voltage. if we double the frequency
the sinusoidal root mean winf=ding voltage also doubled.

E=4.44 * f*b*n*a*b

Is This Answer Correct ?

21 Yes

9 No

Question { 5450 }

what are the type of motors

Answer

classification of motors according to voltage

1) dc motors- series, shunt, cumulative, compound motors.
2) ac motors- single phase, three phase motors.

single phase motors- split phase,capacitor start,capacitor
start/run,shaded pole motors.

three phase induction motors - squirrel cage, slip ring
induction motors.

synchronus motor.

Is This Answer Correct ?

19 Yes

1 No

Question { 6216 }

how dc ct works?

Answer

A direct current transformer in which the primary consists
of an elongated strip of superconductive material, across
the ends of which is applied a direct current potential.
Parallel and closely spaced to the primary is positioned a
transformer secondary consisting of a thin strip of
magnetoresistive material.

Is This Answer Correct ?

0 Yes

10 No

Question { 6096 }

what is the difference between inverter and ups & what is
the earth resistance for ups , if its high why so

Answer

inverter means it converts dc source in to ac.

ups means unniteraptuble power supply.

inverter is the part of ups. in ups battery will charge
while its getting power. if power failed this battery
discharges dc voltage, this voltage is convrted to ac source
by innverter.

the earth resistance should be 4ohms. if not the power will
chose least resistance path and there may be a chance to
equipment failure.

Is This Answer Correct ?

11 Yes

2 No

Question { ITC Infotech, 21453 }

What is the difference between AC Drive and VFD?

Answer

both are same

Is This Answer Correct ?

17 Yes

10 No

Question { HP, 25702 }

star delta connection used in reduce the starting current
at 3 times . how its reduce the current please explian .

Answer

Ans: in star connection line current is 1.732times of phase
current. while taking the phase current we are reducing the
line current. at the same time phase voltage is equal to
line voltage.

Is This Answer Correct ?

51 Yes

108 No

Question { HP, 25457 }

if AVR fails in alternator. what will be the effect.

Answer

Ans: From my real experience the voltage may not come to
zero, the volltage will fluctuate from one value to another
it may not constant at any time period. with this frequency
also increases drastically. due to this there is chance of
blown down of ACB fuses and coils.

Is This Answer Correct ?

32 Yes

8 No

Question { IOCL, 8835 }

Input power is 380 - 450 V but with 45 - 55 Hz frequency -
desired output is 415 V and 50hz with 1% variation
permissible. CVT / Servo dont stabilize the Frequency -
what is best solution??

Answer

please arrange AVR( autometic voltage regulator)

Is This Answer Correct ?

1 Yes

2 No

Question { Wipro, 11558 }

what is general test conduted by transformer

Answer

open circuit and short circuit test.
impulse test.
Megger test.

Is This Answer Correct ?

18 Yes

4 No

Question { 8388 }

why nearly all voltages are in the multiples of 11?

Answer

As the form factor has the value of 1.1 , all the
electrical generation values are in multiples of 11 only

Is This Answer Correct ?

12 Yes

8 No

Question { BEL, 20513 }

On what basis no of earth pits are to be decided either for
transformers or for equipment?

Answer

Ans: Transformer secondaty sholud have neutal point. This
we brought from earth. neutral point is earthed and
connected to T/F. for this we required one earh pit. and
for body earthing we should have another earh pit.
structure earthing for this another earth pit.

For an equipment we required only one earth pit for body
earthing and electrical accessories earthing( like
motors,switch gear, electronic instruments).

Is This Answer Correct ?

23 Yes

13 No