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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: UPS's that aren't
Message-ID: <1924@kitty.UUCP>
Date: Mon, 10-Aug-87 13:25:46 EDT
Article-I.D.: kitty.1924
Posted: Mon Aug 10 13:25:46 1987
Date-Received: Tue, 11-Aug-87 04:33:13 EDT
References: <161@tmsoft.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 43
Summary: Try a ferroresonant regulator; may also be uneconomical

In article <161@tmsoft.UUCP>, mason@tmsoft.UUCP (Dave Mason) writes:
> So, I thought, I'll just go out & buy an Uninterruptible Power System.
> So I did: a Sendon UPS-400W (400 watts, 5 millisecond max switchover).
> 
> Problem: the wave-form that comes out is positively ugly, and while switching
> power supplies don't seem to care, tmsoft has a linear supply.  It will run on
> the battery and when the power comes back, it seems to switch OK; but when the
> power goes away power drops long enough to be a problem (i.e. system crash 1/2
> way through vacation)
> 
> The wave form looks like a bad cross between a sin wave & a square wave,
> switching between the two about the top of the crest & bottom of the trough.
> There are also ugly transients when it's switching between mains power and
> the battery.  I added a Radio Shack "Voltage Spike Protector with Broadband
> Noise Filter" to the output with no discernable difference.
> 
> What I would like is something I can add on after the UPS that will clean
> things up so the power supply works and I get rid of the nasty transients
> (which mess up a terminal I use).

	Unfortunately, one gets what one pays for, and the plethora of
low-cost UPS devices flooding the market generally have poor quality standby
power characteristics.
	The only altermative which _may_ help is to place a ferroresonant
voltage regulating transformer on the output, such as those made by Sola
Electric.  I can't answer for certain if a Sola will help since I don't
know the exact nature of your power waveform.  Unfortunately, the cost of
a 400-watt Sola regulator ($ 350.00) is probably close to the same money
that you paid for the UPS in the first place.
	Good quality sine-wave UPS systems are not cheap. A 400-watt Sola
UPS (p/n 26-00-50400-3001) is around $ 1,400.00.
	Vendors with good-quality UPS systems include Sola, Superior Electric,
Elgar and Lorain.  We have used Elgar for our industrial process control
systems because they offer rack-mounted units.  As an example, we have an
Elgar p/n 172-1 for our site `kitty'; this is a 1.75 kva sine-wave UPS
with solid-state reverse-transfer option.  It gives a picture-perfect
sine-wave with less than 5% THD; however, this nice waveform cost us
close to $ 4K with batteries. :-(

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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