Are you saying that Jim might be in danger of making an ash of himself?

Kind regards,

Denys. . .

Denys Beauchemin
Hicomp America, Inc.
[log in to unmask]        www.hicomp.com/hicomp
(800) 323-8863   (281) 288-7438  fax: (281) 355-6879



-----Original Message-----
From:   John D. Alleyn-Day [SMTP:[log in to unmask]]
Sent:   Sunday, June 08, 1997 2:17 AM
To:     [log in to unmask]
Subject:        110 from 220 UPS

Clever idea, Jim, to get the neutral from the ground - just don't let your
local electrical inspector find out!  You are defeating an important safety
feature and, under certain circumstances, you can back-feed 110V on the
ground connection.

Wirt is dead right about there being a transformer with a center tap - it's
out on the utility pole!

The problem you are experiencing has nothing to do with three-phase
connections.  Obviously what is happening in the UPS is that it is
generating 220 volts with one leg grounded - I'll bet this is exactly what
HP sells in Europe where the supply is 220 volts with one live wire and one
neutral.

(For those interested, three-phase in Europe, or at least in England, is
always "star-connected" - even when it's delta!.  I.e., phase-to-phase
voltage is always 416 and live-to-neutral is always 220. There is no
equivalent to the American "delta-connected" 120/240 with a stinger leg -
and this is going out in the US.  It's a vicious combination for
high-powered electronic equipment as the stinger leg usually has a higher
impedance and, under load, the stinger leg voltage can differ significantly
from the voltage on the other two legs.  This introduces 120 Hz ripple, the
elimination of which is a significant reason for using three-phase. Been
there, done that!)

You said that you had measured 220V from one live wire to ground.   I'll
bet you got zero volts to the other leg (because it's grounded).

Yes, you can definitely solve this problem with a step-down transformer.
However, since a 110V UPS can be had for under $100 these days, I'd just
buy one and plug it in for your 110V equipment.  Quick and easy, and should
cost less than a step-down transformer.

John D. Alleyn-Day
Alleyn-Day International
408-286-6421   408-286-6474 (Fax)
[log in to unmask]       http://www.Alleyn-Day.com