REQ: Schematic for APC Model 1200RM UPS

[Mark & Mary Ann Weiss]

I need to determine if this UPS can be modified to tolerate minor swings in
line frequency (as from a generator) without switching to and staying on
battery power.

We have a situation where the power goes out, the generator comes on, but
the UPS continues to stay on battery with 'input power fault' displayed on
its panel. Occasionally, the generator, under load, drops to 60hz and the
UPS will switch to line power until the loads that have slowed it slightly
have been removed. It runs at 62 hz with only a couple of kilowatts of load.
I think that the generator is spec'd at 60hz when at half to 2/3 load, which
is a lot more than our continuous load.

At any rate, a schematic for this 1992-vintage UPS would help me determine
if the frequency sensing circuit can be modified to increase its tolerance.
Right now, if the line isn't exactly 60.0hz, it will switch to battery power
and stay there.

Does anyone have any ideas about modifying this particular (1200RM) UPS for
the above requirements?

Another option is to spend $1200 on a new APC SmartUPS, with no garantee
that it will tolerate generator power (although we do have an APC SmartUPS
650 VA in another office that seems perfectly happy with the 62hz generator
frequency). I'd like to avoid that gamble, if I can modify this unit with
the help of documentation.

The recent power blackout necessitated bypassing the big UPS and running a
network 'barefoot' off the generator output, a practice I do not like.

--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . AUDIO RESTORATION
Hear my Kurzweil Creations at: http://www.dv-clips.com/theater.htm
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-

 

[David]

APC schematic, not available at any cost except for APC's own service
centers.
Been down this road regarding APC many times before.

David

 

[Mark & Mary Ann Weiss]

There seems to be a conspiracy among UPS manufacturers to keep service
information under wraps. I don't know of a single UPS manufacturer that
allows their service data out of their money-grubbing mitts. Sorry if that
sounds harsh, but that's the way it is.
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Time is what keeps everything from happening all at once.

Very interesting... that explains the fact that I got zero hits on a Google
search, other than leads to buy refurbished UPSes.

So I guess that presumes too that no one here has any idea how to increase
the frequency tolerance of my 1200RM?

I may have to bite the bullet and get a real generator (a Caterpillar
diesel-powered 3-phase monster that produces a clean sine wave at precisely
60hz).


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . AUDIO RESTORATION
Hear my Kurzweil Creations at: http://www.dv-clips.com/theater.htm
Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-

 

[Steven G.]

Not totally correct. A company here in Australia recently sent me (free of
charge) the schematic to an UPS of theirs I have. The model is about 9 years
old, so well out of typical service life.

 

[Mike Berger]

Have you checked the voltage output? We've found that to be more critical
than minor frequency differences. If it's not pretty stable, the UPS won't
switch back to line.

 

[Mark & Mary Ann Weiss]

Yes, I have checked the voltage. It was in the 122v range. At first I
thought it was harmonics. But then I discovered that when the frequency
dropped to 60hz under load, the UPS was happy.
This model is about 10-11 years old, but works very well under typical
conditions of brief outages. The alternative is to spend $1200 on a new
SmartUPS that has a +/- 3hz tolerance.


--
Take care,

Mark & Mary Ann Weiss

VIDEO PRODUCTION . FILM SCANNING . AUDIO RESTORATION
Hear my Kurzweil Creations at: http://www.dv-clips.com/theater.htm
Business sites at:
www.dv-clips.com
www.mwcomms.com
www.adventuresinanimemusic.com
-