# Required Power Supply Formula

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• #10262
jj
Participant

Hi Guys, I'm new here. Please help me out. I hv a 1 no. Exhaust Air Fan of 25kW with Full Load Current of 43.5A -400v.  What is the required power/current rating should I supply? (i.e. isolator/socket outlet rating)

Can any of you guys out there, show me how can I calculate this and what is the formula?

Thanks.

#11696
Keymaster

power=i^2*r

#11746
erickench
Participant

If you know the power factor then you divide into the KW rating which in this case is 25 KW. If you don't know the power factor then assume that it is unity. Your KVA would be the same, 25 KVA. That full load current value is probably obtained from the NEC tables in article 430.

#11747
Keymaster

rahul patil said:

power=i^2*r

u can use 63 Amps 3pole isolater

#12151
Spir Georges GHALI
Participant

jj said:

Hi Guys, I'm new here. Please help me out. I hv a 1 no. Exhaust Air Fan of 25kW with Full Load Current of 43.5A -400v.  What is the required power/current rating should I supply? (i.e. isolator/socket outlet rating)

Can any of you guys out there, show me how can I calculate this and what is the formula?

Thanks.

Dear ;

If you want to install an Isolater or Socket, the nimonal current should be ” 63A “, But if you want to protect the fan's motor, it's better to use a ” Motor Circuit Breaker ” that should be adjusted around 43A.

Regards.

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