ALLInterview.com :: Home Page            
 Advertise your Business Here     
Browse  |   Placement Papers  |   Company  |   Code Snippets  |   Certifications  |   Visa Questions
Post Question  |   Post Answer  |   My Panel  |   Search  |   Articles  |   Topics  |   ERRORS new
   Refer this Site  Refer This Site to Your Friends  Site Map  Bookmark this Site  Set it as your HomePage  Contact Us     Login  |  Sign Up                      
Google
   
 
Categories >> Engineering >> Electrical Engineering
 
 


 

 
 Civil Engineering interview questions  Civil Engineering Interview Questions (3131)
 Mechanical Engineering interview questions  Mechanical Engineering Interview Questions (3300)
 Electrical Engineering interview questions  Electrical Engineering Interview Questions (13442)
 Electronics Communications interview questions  Electronics Communications Interview Questions (2386)
 Chemical Engineering interview questions  Chemical Engineering Interview Questions (420)
 Aeronautical Engineering interview questions  Aeronautical Engineering Interview Questions (77)
 Bio Engineering interview questions  Bio Engineering Interview Questions (17)
 Metallurgy interview questions  Metallurgy Interview Questions (80)
 Industrial Engineering interview questions  Industrial Engineering Interview Questions (165)
 Instrumentation interview questions  Instrumentation Interview Questions (2402)
 Automobile Engineering interview questions  Automobile Engineering Interview Questions (107)
 Mechatronics Engineering interview questions  Mechatronics Engineering Interview Questions (38)
 Marine Engineering interview questions  Marine Engineering Interview Questions (45)
 Power Plant Engineering interview questions  Power Plant Engineering Interview Questions (80)
 Engineering AllOther interview questions  Engineering AllOther Interview Questions (1204)
Question
how to choose the cable size for 100A(is there any formula 
please update)
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
According to NEC , i want to reduced grounding cable from
4mm2 to 2.5 mm2 ,can u give me technical sheet to depend it
from NEC
 
Is This Answer Correct ?    1 Yes 2 No
Jamil
 
Answer
# 2
In usual practice, the carrying capacity of copper is taken
as 2.5 A/sq mm and 1.5 for Al.If the load is steady and
continuous 60 % of these values are adopted.
 
Is This Answer Correct ?    2 Yes 3 No
K.prakashchandra
 
 
 
Answer
# 3
Cable size should be 25 Sq.mm

For Ex: 1000A MCCB
For Al - We have to Consider 0.8/Sq.mm
For Cu - We have to Consider 1.6/Sq.mm

For 1000A = 1000*0.8
= 800A
We have to go for (100X10)mm Bus Bar
 
Is This Answer Correct ?    3 Yes 5 No
Hari
 
Answer
# 4
There is no formula for calculating the cable size. Usually
the cables are sizing based on standards like NEC,BEC.,
etc. if you want to size the cable you first choose the
std, which is using in ur location.as per NEC std just
multiply the 100*1.25=125A, choose the cable ( table-
310.16) for that size. after you choose the cable you have
to derate the cable for your laying location & way of
laying.
 
Is This Answer Correct ?    1 Yes 3 No
Balraj.gabriel
 
Answer
# 5
Theory for Cable Sizing.
From Ohms law, the voltage drop in an electrical conductor is
V = I R
where
I = Current, amps
R = Resistance, Ohms

The electrical resistance can be derived from the properties of the conductor material.
R = ρ L / A
where
ρ = Resistivity, Ω mm2 /m
L = Length, m
A = Cross sectional area, mm2
Watch the units in the above equation.

The resistance can also be expressed in terms of the material conductivity (ψ) which is just the reciprocal of the resistivity.
R = L / (ψ A)

Table 1. Typical material electrical conductivity
Material Conductivity, ψ
Copper 58
Aluminium 36
Mild Steel 7.7

Combining Ohms law with the resistance expression, we get.
V = (I L) / (ψ A)

Now, we can define an acceptable voltage drop in a conductor. I have calculated the voltage drop that was used in several published tables and get around 5.5 Volts.
We could therefore re-arrange this equation to give the cable size. But cables come in standard sizes measured in mm2. In addition, you also need to consider the maximum current for each cable size.

Table 2. Conductor sizes and maximum currents
Cable Size, mm2 1.5 2.5 4 6 10 16 25 35 50 70 95 120 150 185 240 300
Maximum current, A 13 21 28 36 46 61 81 99 125 160 195 220 250 285 340 395
So, the theory is relatively simple, let us now see how to use the program.
 
Is This Answer Correct ?    0 Yes 2 No
Shirish
 
Answer
# 6
there is no funda or formula to get size of conductor wrt
to load. just calculate the ampere of the load, and then as
per ampere ,,, as per the cross sectional area of the
conducter like 1.5mmsq can bear the 4-6amp load,,,so on..
 
Is This Answer Correct ?    4 Yes 16 No
Amrish Sharma
 

 
 
 
Other Electrical Engineering Interview Questions
 
  Question Asked @ Answers
 
Why we transmit the power at the voltage in the multiple of 11 or 1.1 like 11kv, 22kv, 66kv, 132kv...... some one told me that it is due to fomr factor 1.1 of sine wave. its fine but while transforming we can choose any voltage, so why only multiple of 1.1 there also.......? plz tell me.   5
How to calulate the NGR resistance ?   1
why in electric train we can't feel current & generally we have get socked in our normal electricity ?   2
What is the breakdown voltage?   13
what is the use of Antipumping in HT breakers.   8
what is the need of representing AC power in sinusoidal waveform? why not in square or rectangular etc... Lanco 8
what is the working principle of contactor and conditions of normal open and normal close on it? EEE 3
definition of fault level in powersystems?   4
what is the difference between RTD & TERMO COUPLE?   1
what is the function of commutator in dc motor? CTS 10
WHAT IS THE MEANING OF 'UPF'&'LPF'.... HOW CAN WE DEFINE IT? WHAT IS THE VALUE/RANGE OF EARTH WIRE RESISTANCE USED PARTICULARLY IN HOME....   2
what is the problem in manufacturing transformer with 0 degree phase displacement.???why alwasys go for DYn11 or DY5?Whys not DY0 i.e zero degree displacement between primary and secondary side vectors? Bhel 3
 
For more Electrical Engineering Interview Questions Click Here 
 
 
 
 
 


   
Copyright Policy  |  Terms of Service  |  Articles  |  Site Map  |  RSS Site Map  |  Contact Us
   
Copyright 2013  ALLInterview.com.  All Rights Reserved.

ALLInterview.com   ::  KalAajKal.com