30 electrical engineering interview questions and answers

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Electrical Engineering interview questions and answers


Part 1   Part 2   Part 3   Part 4   Part 5   Part 6

1.Why star delta starter is preferred with induction motor?
2. State the difference between generator and alternator
3. Why AC systems are preferred over DC systems?
4. How can you relate power engineering with electrical engineering?
5. What are the various kind of cables used for transmission?
6. Why back emf used for a dc motor? highlight its significance.
7. What is slip in an induction motor?
8. Explain the application of storage batteries.

Why star delta starter is preferred with induction motor?

Star delta starter is preferred with induction motor due to following reasons:
• Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses.
• Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused.
• In addition, starting torque is increased and it prevents the damage of motor winding.

State the difference between generator and alternator

Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced emf into dc current for external load whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used.

Why AC systems are preferred over DC systems?

Due to following reasons, AC systems are preferred over DC systems:
a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution.
b. Plant cost for AC transmission (circuit breakers, transformers etc) is much lower than the equivalent DC transmission
c. From power stations, AC is produced so it is better to use AC then DC instead of converting it.
d. When a large fault occurs in a network, it is easier to interrupt in an AC system, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt.

How can you relate power engineering with electrical engineering?

Power engineering is a sub division of electrical engineering. It deals with generation, transmission and distribution of energy in electrical form. Design of all power equipments also comes under power engineering. Power engineers may work on the design and maintenance of the power grid i.e. called on grid systems and they might work on off grid systems that are not connected to the system.

What are the various kind of cables used for transmission?

Cables, which are used for transmitting power, can be categorized in three forms:
• Low-tension cables, which can transmit voltage upto 1000 volts.
• High-tension cables can transmit voltage upto 23000 volts.
• Super tension cables can transmit voltage 66 kV to 132 kV.

Why back emf used for a dc motor? highlight its significance.

The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the armature rotates, is called back emf. Its value depends upon the speed of rotation of the armature conductors. In starting, the value of back emf is zero.

What is slip in an induction motor?

Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol ‘S’.

Explain the application of storage batteries.

Storage batteries are used for various purposes, some of the applications are mentioned below:

• For the operation of protective devices and for emergency lighting at generating stations and substations.
• For starting, ignition and lighting of automobiles, aircrafts etc.
• For lighting on steam and diesel railways trains.
• As a supply power source in telephone exchange, laboratories and broad casting stations.
• For emergency lighting at hospitals, banks, rural areas where electricity supplies are not possible.

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Discussion Board
electrical engg

why rating of transformer in KVA and for motor rating isi n hp or KW.

gaurav singh rajwar 10-21-2014 01:53 AM

Electrical outlets

We have an electrical fireplace. Whenever it is on one of my outlets get hot in the kitchen. Can you give me some answers? Thank you. 8

Pat 10-13-2014 04:19 PM

Neural

This is a very good for an electrical engineer

i have question
what will happen if i am using ground as a return path instead of neutral

Rahul prajapat 10-12-2014 09:49 PM

EE

Thanks Sir. It isvery much usefull.

Priya Ranjan Panigrahi 10-12-2014 12:27 PM

nice

Sir it is very usefull.i need many q&a from u.

kasinath rout 10-3-2014 06:21 AM

eee

its very knowledgeful

satyendra kumar 09-30-2014 07:42 AM

Qfactor

What is a Qfactor?

Er.vijay nayee 09-6-2014 11:45 PM

electrica maintenance

sensitivity of elcb pwr.
about mcb ratings pwr.
earth resistance and earth compounds pwr.
what is earth ldr pwr?
transformer and related formulas pwr.
what is the nature of electrons pwr?
use of ballast tube light pwr.
cable size and ampere ratings pwr.

lesole kabo modise 08-29-2014 06:07 AM

Electrical

How can we know supply line is ac or dc?????

Pragnesh 08-16-2014 02:37 AM

hi

Plz explain the protections of alternator

Pramod 07-4-2014 09:41 AM

electrical eng

why use earthig and neutral use for earthing replace neutral.

gajendra 06-25-2014 08:02 AM

Electrical Eng.

Why a single -phase induction motor not an
inherently self -starting machine?

indrajeet 06-15-2014 01:48 AM

eee

Pls give a quastions as per topic.like circuits basics t/f induction motors power system

syam 06-8-2014 01:19 PM

eee

Pls give a quastions as per topic.like circuits basics t/f induction motors power system

syam 06-8-2014 01:19 PM

electricl engnearing

vpo bhadwar teh nurpur distt kangra hp

manoj kumar 02-9-2014 02:05 AM

commentment of the interview question

this type of question can easily solved by the 1st year student. plz give a hard question



ok tata.

amiya 06-27-2013 03:40 PM

 

 
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