How can we calculate the cable size???
plz give the formula !!!!!

Answer Posted / 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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