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RE: 120V from 250V 3 phase?

To: <shop-talk@autox.team.net>
Subject: RE: 120V from 250V 3 phase?
From: "Randall Young" <Ryoung@navcomtech.com>
Date: Wed, 1 Oct 2003 23:33:22 -0700
> Thinking a 3 phase system needs 3 "hot" lines leads me to believe I
> either have a neutral or ground as the 4th wire. While I know neutral
> and ground are probably connected at the breaker box, I'm not going to
> chance a bunch of expensive computer equipment on a poor power supply.
> So as it is now, I don't think this will work.

I agree, you've got a problem.  The main issue is that your computer
equipment wants both a safety ground and a neutral, and you don't know which
is in your outlet.  The easiest "quick & dirty" solution might be to get a
220/110 isolation transformer, and connect one leg of the output to a
separate safety ground, to create a new neutral for your computer equipment.

Or just run an extension cord down the hall ... <g>

> I've done enough electrical work to understand what I'm doing, but would
> like confirmation from one of the smarter people about this idea. I
> looked for a UPS to go into the outlet, but didn't find any with a 3
> phase input.

Such things are available, but you don't want to know what they cost !
http://www.cdw.com/shop/products/default.asp?EDC=410676
And it still requires 5 wires for it's input, 3ph + N + G.

Randall





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