Answer / s. patel

the equation of Power:

P=VICos (phi)
for single phase:- if load is 128 kw for single phase
then...Iph=(p/vph Cos(phi)(assume:p.f=1)
= 128000/(240x1)
=533Amp so this need 400-500sq mm 1 core of copper ok...

and if 3 phase is there
then

p=1.73xVLxILxCOS(phi)
IL=128000/(1.73x415x1)
=178Amp

if it may p.f is down up to 0.85 then current rating will increase by 200 to 210 Amps

so we have to select the cable as per their current carrying capacity up to 210 amp for three phase connection.
So we have to select 95 sq mm x 3 core...ok

Answer / s.patel

means for 3 phase connection
95-120 sq mm x3c of copper or for aluminium 150-185 sq mm x3c is required...

Answer / charan

Pl. Exp me how to Calculate the size.. i mean i want the
formula for that..

Answer / s. patel

if you are using 1 phase with 128 kw then you need to select the 500 sq. mm or if you are using 3 ph. then you have to select 4x120 sq mm of copper pvc cable armored or unarmored
and fro alluminium 4Cx185 sq. mm pvc cable is require.....

Answer / k.prakashchandra

Diversity factor can be taken as 1.5 to 2.5 depending upon
the simultaneous similar loads.You can use 4x50 sq mm copper
cable or 4x70/95 sq mm Al cable.

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