Answer Posted / abdool

3pahse power is P(in KiloWatt)=I.V.PF.(root 3).....
I=1.74 x P(KW)
EXAMPLE:
so, assume 3ph 400V 15KW motor, In=1.74x15=26.1 A,
& 15KW=20HP.....so 2xIn=Breaker rating= 52.2A
...choose 63A MCB

Cable size normally 20-25% higher than breaker to avoid
cable heat/burn accident in overcurrent fault. so, 1.25xIn=
62.64A so choose 80A Cable rating of 25mm2.

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