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Q&A Issue in Cable Sizing and control cable selection

200 HP is 147.1 kW. At 480 V, it takes 306 A to transfer that much power. You didn't say, but your 480 V power feed is probably three-phase, and the motor is three-phase too. I don't remember ho...

posted 2mo ago by Olin Lathrop‭

Answer
#1: Initial revision by user avatar Olin Lathrop‭ · 2024-09-07T16:12:54Z (2 months ago)
200 HP is 147.1 kW.  At 480 V, it takes 306 A to transfer that much power.

You didn't say, but your 480 V power feed is probably three-phase, and the motor is three-phase too.  I don't remember how exactly that reduces the current requirements in each of the three conductors, so let's just say you need to support 200 A per line.  You will have to scale the result according to the real current requirement.

A 5% voltage drop starting at 480 V is 24 V.  That's the total out and back drop, so 12 V per line.  That means the resistance of each line can't be more than (24 V)/(200 A) = 120 m&Omega;.  That's going to require absurdly thick cables.

I'm not going to go further because this makes no sense.  For that much power over that much distance, you really need to use higher voltage.  Find the 480 V transformer and maybe you can tap into whatever is driving its primary.

Another possibility is to use a transformer to increase the 480 V to a few kV or something, then convert back down at the other end.  At 150 kW, you will need a fork lift to move them around.

This is the kind of thing you need to get the power company involved in.  Anyone that has to ask here shouldn't be anywhere near this project.  There are serious safety concerns, and most likely regulatory ones too.  Get someone qualified and certified to work on this.