[ale] OT: U.P.S. Recommendations

[Step]

We supply a UPS with each Laser Radar system we sell at my company.  Our
devices are VERY sensitive, partly because the power is supplied across a
10m antenna - err, cable - to the instrument.  The most sensitive power is
to the embedded QNX PC.  Of course our power input is from factory grids,
that often have a lot of noise when they start up other large machinery.

We have gone through 4 different models of UPS, with some extensive testing,
but again we are in more demanding situations than I assume is needed here.
We started with an APC, went through a few different models, but as someone
pointed out they are not true dual-conversion (that is, they are not
constantly converting to DC and back to AC).  We tried a Minuteman, which
was more sensitive and sold as double-conversion - but as it turned out,
still not sensitive enough for us and not "true" double-conversion.  What we
use now is more expensive, but has worked well - the MGE UPS.  This is
sensitive enough that we actually needed to insert some thermistors to
handle the  inrush of current at startup of our Power Box.

If you have more questions, I'd be glad to share what I know as well.  Dan
Lambert undoubtedly has a great deal more technical knowledge on the
subject, but I can share our experience as a customer and having supported
over 100 UPS / systems in the last several years if you need.

Cheers,
Step

On 4/12/07, Dan Lambert <danlambert at bellsouth.net> wrote:
>
> On Wed, 2007-04-11 at 23:15 -0400, James P. Kinney III wrote:
> > On Wed, 2007-04-11 at 22:45 -0400, Jim Popovitch wrote:
> > > On Wed, 2007-04-11 at 22:02 -0400, Jeff Hubbs wrote:
> > > > Aaron -
> > > >
> > > > What you probably want are "true online" UPSses - marketroidese for
> > > > UPSses that run the load off their inverters all the time.  This is
> > > > distinct from the typical APC/Belkin stuff that still has a "burp"
> when
> > > > they switch over from direct to inverter, relying to some extent on
> > > > systems' power supplies' tolerance for burps and perhaps even
> > > > ferroresonant transformers (meaning that they use transformers whose
> > > > electromagnetic circuit is designed with a built-in 60Hz "tuning
> fork"
> > > > effect.
> > >
> > > Be warned, "true online" equals full time noise.  Modern home
> > > electronics can handle the "burp" USPes without problems, plus you
> > > wallet will appreciate it in addition to your ears.
> >
> > Hmm. I was drooling over those when I though about the noise factor.>
> > > _______________________________________________
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> > However, I have a backup generator that at the low end of the AC cycle
> > it generates some serious crud that a large APC that powers my server
> > stack doesn't like. At all. These system appear to be battery backed
> > power conditioners. One would handle my issue nicely and it's in a
> > closet anyway. Wife made some very unlady-like comments about the sound
> > out put from the 1U server. The comments got worse when I explained it
> > was one of 4. :)
> > >
> > > -Jim P.
>
> If that's the case, James, then your generator needs to be adjusted. It
> should come up to speed and stabilize at 60Hz, +/- 1HZ to be correct.
> What is generally more of a problem with generators is the AVR
> (Automatic Voltage Regulator) sensitivity. Some generators have to have
> a minimum of double the capacity of the UPS just to have enough
> available energy to handle the inrush when the UPS tries to synch with
> their output and return to "normal" mode.
>
> Conversely, some of the different UPS designs are more sensitive to the
> fluctuations in frequency that smaller generators produce under load.
>
> There are several different philosophical camps regarding UPS'. Each
> brand or design has it's own proponents. Each design has it's own
> strengths and weaknesses, too. Some are better in some situations than
> others. It's just like anything else, in that there is no panacea.
> Everything is a tradeoff.
>
> I have worked in the critical power industry for over 25 years, and have
> worked on MGE (and EPE before they were MGE), MPL, Emerson, Gould,
> Lortec, Powerware (And Exide before that), Socomec, Best, Liebert, APC,
> and probably 20 more brands, and I can tell you for a fact that some of
> them are great designs, and some are real junk. The good ones survive
> and thrive. The not so good ones, well, they aren't around any more.
>
> I now work for APC/MGE in their 3 phase power systems division. I have
> very good friends that work for Powerware, Liebert, and several other
> companies. I know their technologies very well, and they know mine. If
> chosen wisely, any name brand UPS on the market will do quite well for
> 99.997% of the situations they are made to deal with. Where the rub is,
> is in the fact that more often than not, when someone has problems with
> a UPS, it is due to poor selection rather than poor design.
>
> A number of people will give anecdotal evidence based on a limited
> number of instances in certain circumstances, and while those are valid
> case studies, for every one that someone describes for a given brand or
> model of system, I can probably dig up 25 where the same system
> performed perfectly.
>
> If you want straight talk about UPS', I'll be happy to help out.
> Naturally, if my company makes a UPS that fits your needs, I'll tell you
> about it. If something else fits your needs better, though, I'll tell
> you that, too.
>
> Dan
>
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