Interview Questions Answers in Electrical Engineering

what is the difference between earthing and grounding of electric circuits

Answer

Earthing means connecting to earth ,grounding means connecting to large conducting main body / frame as in self propelled vehicles ,ships ....and also connecting to earth

Is This Answer Correct ?

3 Yes

0 No

Question { KSEB, 7034 }

What is burden of ct,explain very simple

Answer

As burden is expressed in VA ,take the above answer as voltage across ct secondary x current

Is This Answer Correct ?

0 Yes

0 No

Question { KSEB, 7419 }

Impedance relay is directional relay or non directional relay?

Answer

It is directional ,having both separate forward and reverse reaches

Is This Answer Correct ?

10 Yes

4 No

Question { AZ Engineering, 11656 }

What is difference between Electrical & Electronic Device?

Answer

Flow of electrons in electronics is current in electrical

Is This Answer Correct ?

2 Yes

6 No

Question { 3653 }

Why capacitor is blow when I am starting motor ?

Answer

Probably you are using starting capacitor or of less voltage/ current . Use the one of ' continuous (time) rating '

Is This Answer Correct ?

3 Yes

1 No

Question { 5302 }

why Square root 3 used for three phase?

Answer

It is vector sum , the resultant = root3 /2 + root3 /2= root3

Is This Answer Correct ?

0 Yes

0 No

Question { 5302 }

why Square root 3 used for three phase?

Answer

It is vector sum . The length of diagonal is root3/2 + root3/2

Is This Answer Correct ?

0 Yes

0 No

Question { Central Moloney, 7029 }

I have 3 1000 kva single phase transformers and I wish to replace them with one three phase transformer. What is he kva rating of the new three phase, is it 1000 kva also or 3000 kva.

Answer

Your total requirement is 3000 kva

Is This Answer Correct ?

7 Yes

1 No

Question { 5113 }

If cvt is most advance & effective(economically & stability)so why not use instead of VT(11 kv & 33 kv)?

Answer

The accuracy of cvt is more than 1.0 , hence not very suitable for measurement and distance relay

Is This Answer Correct ?

0 Yes

0 No

Question { Coca Cola, 8732 }

I have a transformer 3phase 11kv/410v and its name plate missing. now how can I judge its rated kva?

Answer

Almost all dist transformers have similar cooling , compare the quantity of tr oil with known one to get appx rating

Is This Answer Correct ?

0 Yes

3 No

Question { TATA, 8145 }

My load is 15 kw,i want to improve power factor from 0.8 to 0.9,how select capacitor

Answer

Using formula KVA^2= KW^2 + KVAr^2 ,find the values KVAr at 0.8 and 0.9 pfs. The difference is the required KVAr of the capacitor

Is This Answer Correct ?

4 Yes

5 No

Question { 3572 }

can we use ac ameter as dc ameter with ct

Answer

Normally No , as AC meters are of moving iron type , and DC are of moving coil type .

Is This Answer Correct ?

1 Yes

0 No

Question { L&T, 5773 }

How will you calculate the correct KWH value if your CT is 600/5 and your KWH meter is rated for 100/5

Answer

If the load is 100 A ,the meter records correctly if the CT ratio is 100/5 as the meter gets 5A current . If the CT ratio is 600/5 the current in the meter will be 5/6 A for the same load current . Hence to get the correct reading ,multiply by 6.

Is This Answer Correct ?

8 Yes

2 No

Question { 4033 }

What is the basic difference between directional and non directional over current protection?

Answer

Potential coil, as in the energy meter

Is This Answer Correct ?

0 Yes

3 No

Question { 2100 }

why conductors of low tensile strength
1)produce greater sag and
2)can not be used for larger spans

Answer

More elongation due to tension

Is This Answer Correct ?

0 Yes

0 No

k.prakashchandra