I want formula to calculate cable size as per load given in
kw & amp.I searched many sites but didn't right answer.Plz
reply me asap.

Answer Posted / bala

Hai
The formula is delda v =
rt3 x I X Z X L/ 1000 x no OF runs
% OF VOLTAGE DROPS = Deta v
------ X 100
APPLIED VOLTAGE
The % of voltage voltage drops should be below 3 %
I = Requird current
Z = Cable impedance
L = cABLE LENGTH

First how many Amp you required
Example - 80
then you go to cable catalouge find out suitable cable
size
then calculate original current carring capacity of that
cable and multifly with 0.72 ( derating factor )
example in catalouge may be 35 sq mm cable and current
carring capacity may be 125 A
125 X 0.72 = 90
The carring carring capacity point of view this cable will
be ok
next you will check voltage drop with help of above said
fomula

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