Re: Problem with a UPS unit and an Antec Power Supply

On Thu, 3 Dec 2009 19:20:10 -0600, "GlowingBlueMist"
<GlowingBlueMist@xxxxxxxxxxxxxx> wrote:

Bryce wrote:
Charlie Hoffpauir wrote:

On Thu, 03 Dec 2009 16:33:29 -0500, Bryce
<none@xxxxxxxxxxxxxxx> wrote:

Charlie Hoffpauir wrote:

First, this is a home-built computer, with an Antec case
and PS. The 3rd Antec case I've used for a homebuilt.
The PS is a 500w Antec unit that came with the case.
(The PS is labeled as Antec Earthwatts 500w max, model
EA 500D.)


Problem description...

My UPS unit (APC 1250) failed to keep the computer
running when we had a severe power dip, so I concluded
that the UPS was bad... (I had used this same UPS with
my previous computer, but since it seemed to be working
fine, I kept it when I built the new computer).

So I got a new APC 1500 (figuring bigger is better).
Then another power blip, and again the UPS failed to
keep the computer on-line. So I disconnected everything
except the computer itself from the UPS unit and ran a
test by unplugging the UPS.... The UPS fired up but the
computer shut down.... but not immediately.

So I phoned APC support and they had me do a few more
tests, including unplugging the UPS with a normal
resistive load connected (a lamp), and the UPS worked
fine, not a blink of the lamp. Another test with the
computer connected, and this time me watching the
display on the UPS, and the output voltage actually went
crazy, varying quickly from 120 to less than 60 then
immediately up to as high as 250 and back down again,
over and over until we unplugged the computer.... the
voltage then stabilized at 120.

The APC tech said that some power supplies needed a
special UPS that produced pure sine waves, rather than
square waves.... and that they were available from APC
but were rather expensive. An alternative would be to
change the PS in the computer.

So, I exchanged the PS with an old one from another
Antec case (Antec TruePower 2, 480 w) and the computer
seems to be once more in sync with the UPS, that is I
tested the setup by unplugging the UPS and it powered up
the computer just fine. Is there something fundamentally
different between the Earthwatt and the TruePower series
of Antec PS?

Has anyone else heard of this, or was the tech just
blowing me off?

If this is plausable, what would be a good replacement
PS? I can continue to use the 480w TP2 I suppose, but
then what to use for that computer?

Since I now seem to have 2 workable UPS units, would it
"help" to have both units connected, in series, so that
power failure the unit that the computer was connected
to would get the square wave from the first UPS, and
perhaps filter it enough to keep the computer on-line?

I'll appreciate any insight.

Cascading ("in series") the two UPS units will not help
and is a bad idea in general.

Antec's Earthwatt uses active power factor correction to
improve electrical efficiency. Electronics added to the
supply switches back and forth between charging a
capacitor from the rectified AC line and then discharging
into the DC storage capacitor in the UPS. The switch
points must match certain thresholds in the (normally)
sinusoidal AC voltage input waveform.

I suspect the active power factor correction used in the
Earthwatt is behaving very badly when it sees the square-
wave produced by the UPS operating on battery. As APC
indicated, a sine-wave UP$ $hould $olve the problem.
Hopefully, Antec will build power supplies that won't
misbehave this way.

Until then, avoid the Earthwatt series.

Bryce

Bryce,

Thanks for that information. I'll look for another PS, and
hopefully it will specify whether it uses active power
factor correction. Until then the old Antec 480w unit
seems do be doing fine... we had another power blip this
afternoon, and the computer didn't falter.

Antec ought to be interested in your experience. Lots of
desktop computers are powered from square-wave UPS units.
If their APFC circuit is incompatible, they have a problem
that needs addressing. It's also possible that your unit
might be defective. Perhaps they would be willing to swap
it for another: you get a (hopefully) useful unit and
they get one for quality control to look at.

Give them a call.

Bryce

Good suggestion Bryce, any company that wants to pursue business computers
will need to be compatible with the existing base of UPS machines.
Expecting a company to upgrade all UPS's to "pure sine wave" technology
would be cost prohibitive, making the power supply company the cheapest to
replace...

With luck it is just a defective power supply and not an entire line of them
being sold by a company that does not have a clue...


Thanks for the suggestions.

I submitted a problem report to customer support, describing what has
happened, and asked specifically if the Earthwatts series were
incompatible with UPS units. Since the PS is only 10 months old, it
should be covered under warranty (if indeed it is defective). However,
I guess it depends on how they define defective.... since it is
effectively powering my old computer, and it powered my new computer
since Feburary (except for when I had a power failure).
.

Relevant Pages

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