Interview Questions Answers in Electrical Engineering

how to caculate cable size for given amperes

Answer

Mr. Virendra this formula is applicable for busbar only
not for cables . as per your statment 10 sq mm cu cable
suitable for 16 A only . PLEASE GO AND CHECK with cable
manufacture catalouge. the 10 sq mm Al cable suitable for
+_ 40A .

Is This Answer Correct ?

3 Yes

0 No

Question { 8411 }

what is synchronizing panel & its working.

Answer

if we have two no of D.G Sets u can take supply seperately
with help of buscoupler in open condition and also u can
take combination supply with help of buscoupler closed
condition in a single panel

Is This Answer Correct ?

7 Yes

0 No

Question { 6538 }

what happen when generator neutral supply and transformer neutral supply linked

Answer

some noise will be created in transformesr side and some
hundding will be created in d.g side

Is This Answer Correct ?

0 Yes

4 No

Question { 53837 }

how much current does 3ph. 10 hp ac motor draw.

Answer

Laod = 10 HP = 10 * 0.746 =7.46 KW
= 7.46 * 1000 / RT 3 * 415= 10.38 A
Consider 1.6 Time for starting current = 10.38 * 1.6 =
16.06 A

Is This Answer Correct ?

10 Yes

14 No

Question { 16979 }

what is distribution board and panel board

Answer

Panel board will be with MCCB and erected with floor/wall
for medium voltage distribution
But distribution board will erected on wall and it is using
for low voltage distribution

Is This Answer Correct ?

9 Yes

4 No

Question { 17363 }

what are iron and copper losses

Answer

No load losses and load losses

Is This Answer Correct ?

2 Yes

3 No

Question { 19160 }

what is the formula to calculate the fault level current for
any substation?

Answer

Hai
we are using two method for find fault level.
1 - based on the supply voltage level
2. Based on the T/F capacity , Impedance, cable and
distance .

The first methios iS very simple but you will follow as
per TNEB standard. TNEB standard

11 KV - 350 mva
22 KV - 500 mva
33 KV -750 MVA

SO based on the aove standard

for 11 KV = 350 / RT 3 * 11 =18.39 KA

i.e = 11= Applied voltage or system voltage

Is This Answer Correct ?

18 Yes

7 No

Question { 15439 }

in 5 mva transformer 33/11 kv s/s what rating of capacitor
bank is required & what is the fourmula for rating

Answer

Generally we are using capacitor bank at down stream
only . ( consumer end ) so will provide capacitor bank only
for 11/ .433 KV T/R

Is This Answer Correct ?

4 Yes

4 No

Question { 32113 }

How many 2 ton window A/c can runs on a 125 KVA generator?

Answer

Mr.das
yourmconversion is wrong bec 1 ton = 3.51 KW is too high ,
generally all the people recommended 1 ton A/C = 1 TO 1.5
kw so please take this type of conversion .

Is This Answer Correct ?

7 Yes

5 No

Question { 10175 }

from 33kv to 440v 2mva transformer how much full load
current will be at ht side and lt side and which range of
ctpt will be used?

Answer

35 A on HT Side 2625 A on LT Side nd requiired CT on HT
side will be 50A and LT side 3200A (because the standard
breaker rating is 3200 A )

Is This Answer Correct ?

7 Yes

4 No

Question { 6250 }

How to select busbar?

Answer

Consider 1.6 A for Cu Bus and 0.8 A for Al bus .
Example
consider 50mm x 6mm Busbar
50 x 6 = 300sq mm
so
300 x 1.6 = 480A
This size Cu bus suitable up to 480 A

300 X 0.8 =240 A
This size Al bus suitable up to 240 A

Is This Answer Correct ?

11 Yes

1 No

Question { 37932 }

why we use Bus earth truck and Cable earth truck

Answer

for saftey point of view and reduced to time for providing
Individual earthing system.

Is This Answer Correct ?

1 Yes

8 No

Question { 38372 }

how to claculate earth strip size for 1500kVA transformer
for neutral and body

Answer

you will follow as per State electricity board norms - 50
x 6 mm Cu for Nu and 50 x 6 mm GI FOR body 0r
you will calculate as per short circuit calculation
Formula 0.0054 x root t x I
Where
t =1 second
I = SHORT CIRCUIT CURRENT
example
Fault current- 33kA( assumed )
0.0054 x root 1 x 33000= 178.2 mm
so you will recommended 50 x 4 mm Cu

Is This Answer Correct ?

14 Yes

9 No

Question { Garware, 27754 }

Why charcoal and salt add in earthing pit.

Answer

Hai
go and Ask your GM and DGM , THEY NO VERY WELL

Is This Answer Correct ?

11 Yes

23 No

Question { Alchemist, 5306 }

give me list of material for wiring of 20hp motor?

Answer

1. one stardelta starter
2. Cable
3. ONE suitable FEEDER FROM MCC Panel
Earth strip ( 25 x 3 cu/ GI )

Is This Answer Correct ?

3 Yes

0 No

balasubramanaian