In a Circuit how the MCB and Fuse ratings are calculated.
And shall the fuse follws the MCB or it is otherwise?

Answer Posted / daher

Use this formula for 3 phase: P=3*Vph*Iph*COSphi then
I= P/3*V*COSphi for example p=3000wat, Vph=220vac and
COSphi=0.9 so Iph= 3000/3*220*0.9= 5Amp now you shoose from
the manufacturers cataloque which circuit breakers is
nearest and suitable for your circuit for example 6Amps.

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