Answer / prashant

The basic equation is

P = 1.732VIcosA, where CosA can be taken as 0.85
V = 415 V
P = load
From this u have to find the current I and then using the
table select a suitable cable and cable size which can
withstant the current.

Answer / shirish prajapati

r=v/i and r=&l/a where &=specific resistance of conductor,
now v/i=&l/a then i=va/&l
i=current.v=voltage ,a=area of conductor. &=specific
resistance of condutor ,l=length of condutor

Answer / bob

first you should know permitted voltage drop U0% then calculate the cable size
A= 1.73 × I × l× P.F / 56 × U × U0% mm2 ( 3 phase load )
I: load current
L:distance
p.f: power factor
56: specific conductivity of CU and 34 for AL
then compare the result with table to make sure voltage drop and current withstand is Ok
make enough reservation for load current by multiply the load current by 1.25

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