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From: chen@gt-stratus.UUCP (Ray Chen)
Newsgroups: sci.electronics
Subject: Re: UPS's that aren't
Message-ID: <845@gt-stratus.UUCP>
Date: Wed, 19-Aug-87 00:26:20 EDT
Article-I.D.: gt-strat.845
Posted: Wed Aug 19 00:26:20 1987
Date-Received: Sat, 22-Aug-87 00:46:21 EDT
References: <161@tmsoft.UUCP> <1924@kitty.UUCP> <654@neoucom.UUCP> <1932@kitty.UUCP> <1182@weber.munsell.UUCP>
Sender: news@gt-stratus.UUCP
Reply-To: chen@gt-stratus.UUCP (Ray Chen)
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Organization: The Clouds Project, School of ICS, Georgia Tech
Lines: 63
Summary: a transformer question


I have a question for you folks.

A combination of old age and flakey Georgia Power finally killed my
old computer.  In an attempt to prevent a repeat of this sitation, a
friend of mine found me what seems to be a 2500 watt isolation
transformer.

It's black, *heavy*, and made by Freed Transformers of Brooklyn, NY.
Dimensions are 10" long X 6" wide X 7" high (or so).  The thing weighs
a ton.  We managed to put it inside an industrial strength milk crate.
So now 2 people can lift it and not get hernias if they're careful.
There are 2 sides with terminals.  One side says "Input 115 V/50 60 Hz".
The other side says "Output 25KVA".  We think that's a misprint that
should read "Output 2.5KVA" as the concept of a 1 cubic foot
25,000 watt transformer boggles the mind.

There are some numbers on the top that read "5950-856-1800" and
"37076".

First, anyone know anything about this beastie?  We think it's
your standard lots-of-coils transformer just because the thing weighs
so much.

Second questions -- how to safely connect it?  It's got +/- input
and output terminal.  I'm assuming that you connect the + and -
input terminals to the wall socket (via a plug and cable) and
the + and - output transformers to a power strip.  The real
question is what to do about grounding.  I'm assuming that you
don't ground either side and you just let the ground float.  So
the hookup looks like --

	Output	    Xformer	Wall
	+ ---------- +|+ -------- +
	GND --        |        -- GND
	- ---------- -|- -------- -

Is this the right way to do it?

Third, anyone got any idea on how much E&M (RFI, whatever) this
thing will put out?  I wasn't planning on keeping diskettes or
tapes near it, but if screws with the microwave oven (which will
be within 6 feet of the thing) or the neighbor's TV, I'm going
to have problems.

Fourth, any ideas on heat output?

Fifth (just to make sure), from my vague memories of my (one)
analog circuits course, even though the transformer is rated
at 2.5 KVA, it shouldn't draw the full load.  The load it draws
should depend on the load on the transformer.  But I'd hate to hook
the thing up and blow every circuit breaker in the apartment to
find out that I was wrong.

Sixth (just for fun), how bad do you think the noise might be?

As you may have gathered, I an *not* an EE-type and any help you
can give me would be much appreciated.

Thanks.

	Ray Chen
	chen@gatech