Interview Questions Answers in Electrical Engineering

How we Use DC Power in Transformers? is it possible ?

Answer

basically, transformer consists of primary and secondary
windings of some turns.this winding can b compared vid an
inductor of some turns.so inductor vil allow dc to flow
through.if the input is closed ckt,current vil be flowing
which finally leads to core saturation.

Is This Answer Correct ?

1 Yes

5 No

Question { L&T, 9665 }

WHY R USE IN BRUSH IN THE MOTOR?

Answer

the main use of brush is to collect the current from
commutator

Is This Answer Correct ?

23 Yes

2 No

Question { 3582 }

I want to know the principle of rotating flux transformer.

Answer

u vil be giving 3 phase supply to 3 phase stator winding,a
rotating magnetic field is produced.now rotor is
stationary. i.e, it has not started rotating.only the field
is rotating.now there is flux variation in rotor due to tis
rotating field n hence emf vil be induced in the rotor
bars.becoz of this current vil b flowing in rotor.now main
principle is current carrying conductor placed in a
magnetic field vil experience a torque.n thus rotor
rotates. this much only i kno.

Is This Answer Correct ?

2 Yes

0 No

Question { 4559 }

how can we run the induction motor at 9000 rpm ,by keeping
frequency constant??

Answer

u gotta increase the frequency from 50Hz to greater than
150Hz. am telling for 2 pole.but i dont think this is
practically possible.

Is This Answer Correct ?

4 Yes

1 No

Question { Tanfac, 43179 }

Three phase alternators are connected in star connection
why?

Answer

i feel the answer given by $$$ and ajay is correct.in delta
its closed loop, so it allows the parasitic current to
circulate in the loop which is an undesirable one.

Is This Answer Correct ?

6 Yes

5 No

Question { L&T, 19638 }

Why indian power system in 11kv,22kv,33kv,66kv,110kv,220kv ?
2) Why ups required dedicated earth?

Answer

for every 100V ,we gotta add 10V in order to compensate the
transmission loss.hence its in this series. its actual
story goes like this.... thomas alva edisn introduced the
first dc distribution systm..i.e, manhatten dc system.he
wanted to make one incandescent lamp glow.for that he tried
with 100V n found the lamp to glow brightly.but when this
lamp was fixed in a street corner, it did not glow with the
xpected brightness.so he made it as 110V and tried the same
n he found the lamp to glow with that original
brightness.from that time, it became a std to add 10V for
the trans loss compensation.

Is This Answer Correct ?

11 Yes

39 No

Question { 7981 }

WHAT IS THE USE OF TERTIARY WINDING IN A STAR/DELTA
TRANSFORMER ?

Answer

tertiary winding is basically a low kva rating one
connected in delta which is used for getting a sinusoidal
flux by allowing a triple frequency component to flow.for
the output to be sinusoidal, flux must contain the triple
frequency component.
source: theraja

Is This Answer Correct ?

6 Yes

1 No

Question { 3806 }

Reversal of corrent feature in MCCB- What is reversalof
current -explain broadly.

Answer

am not getting ur question properly. but still, i wanna
mention one thing that i kno. Basically, there are two
kinds of mccb...conventional and current limiting...in
current limiting, there will be two contacts, lower contact
n upper contact which vil be in the form of strip.current
in lower n upper contact are opposite in direction. when a
heavy fault current flows, there vil b more repulsive
force.thus the contcts comes apart.this is one part in
working of that mccb.but am not sure whether this the
answer what u r expecting.

Is This Answer Correct ?

0 Yes

1 No

Question { IIT, 34939 }

Why we use Capacitor in Single
Phase Induction Motor?

Answer

there vil b two windings. they are main winding n starter
winding of two different inductances.i.e, one with low
inductance n another with higher value. so ther vil be a
phase shift of q1 and q2(say some angle)in accordance with
inductance value. NOW, IN ORDER TO INCREASE THE PHASE
DIFFERENCE BETWEEN Q1 N Q2, WE EMPLOY A CAPACITOR OER
HERE,WHICH MAINLY HELPS IN STARTING.

Is This Answer Correct ?

15 Yes

2 No

Question { 3449 }

what is the minning of propotional, integral, derivative ?

Answer

types of controller.

Is This Answer Correct ?

0 Yes

0 No

Question { 5388 }

what will be the difference on output when 3phase I.M. is
given a delta or star supply?

Answer

if its gonna b star connected,it vil be difficult to pick
up the load, bcoz output power delivered by star is 3 times
less than delta.so star connection is advisable to b used
during starting purposes.

Is This Answer Correct ?

0 Yes

0 No

Question { 4211 }

what is the type of motor that is used in emu units in india

Answer

DC TRACTION MOTOR WITH RHEOSTATIC CONTROLFOR VARYING THE
SUPPLY

Is This Answer Correct ?

1 Yes

1 No

Question { 3987 }

what you mean swtchgear(electrical)

Answer

its a device or combination of devices which is mainly
intended for the purpose of making,carrying and breaking of
electric current in a circuit under normal condition or
also under abnormal(faulty)condition.

Is This Answer Correct ?

7 Yes

0 No

Question { 4706 }

as ac supply is given 2 the transformer why it doesnot
depends upon powerfactor????

Answer

transformer basically acts as a source.so it doesnt depend
on power factor.whereas motors vil act as a load vil depend
on power factor

Is This Answer Correct ?

2 Yes

0 No

Question { 6426 }

Wtat is mean by GHOAST VOLTAGE?

Answer

Stray or ghost voltages occur from capacitive coupling,
which takes place between energized circuits and non-
energized non-connected adjacent wiring.
practical occurance : When facilities or buildings are
built and wired, it's very common for the electricians to
pull extra wire thru the conduit for future use. These
wires are typically left unconnected until needed.at this
situation coupling effect takes place as explained above.

Is This Answer Correct ?

3 Yes

0 No

meenakshi