Answer Posted / chintan patel

It can be different for DC , 1phase AC , 3 phase AC , systems,

Lets calculate for all ,

1 ) For DC ( you have not mentioned Voltage but considering 230 V )

100 kw means 100000 watt

formula for DC power p= vi

100000= 230xi

i=100000/230= 434 amp

we always use current rating of the mccb is 1.5 times of full load current so we can use 434x1.5= 652 amp.
( if system is not running on full load select 630 Amp MCCB, if its on full load select 800A )


2 ) For 1phase AC,

Power: P = V I cos phi ( cos phi is power factor is not known assume 0.8 )

100000 W = 230 x I x 0.8
I = 543 Amp

we always use current rating of the mccb is 1.5 times of
full load current.
mccb required 543 Amp X 1.5 = 815 Amp
select 800 Amp MCCB

3)

If load is 3 phase AC ,

Power P = sqrt(3) x V x I x cos phi

100000 w = 1.73 x 415 x I x 0.8
I = 174

we always use current rating of the mccb is 1.5 times of
full load current.
mccb required 174 Amp X 1.5 = 261 Amp

( if system is not running on full load select 250 Amp MCCB,
if its on full load select 315 A )

hi i will D.E.E.E.is completed pls send rrb diploma old qustion papaer sent in my e mail. i.d.

1959

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