[ale] OT: U.P.S. Recommendations
Dan Lambert
danlambert at bellsouth.net
Thu Apr 12 11:42:55 EDT 2007
APC has a bunch of dual conversion UPS models out there. It just depends
on what size device you need. Voltage requirements are important, too.
There are very few dual conversion single phase UPS models out there,
and virtually none that only provide 120 V AC. There are several out in
the market that have AVR (Auto Voltage Regulation) built in, and good
surge protection.
Needless to say, the odds of finding a good quality 120 volt UPS with
good AVR and double conversion at a low price are pretty slim. In fact
I'd say that there are probably two chances, and slim is on vacation
right now.
What you might find is that a good UPS that has AVR can be set to accept
a wide enough voltage window to allow your generator to work adequately
well with it. I would not even think if attempting this with a UPS
without a really good AVR, though.
Dan
On Thu, 2007-04-12 at 10:47 -0400, Step wrote:
> 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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