Our emergency generator now is a 20KW diesel. The UPS's like that one
just fine.
I've wondered sometimes if it's not about how many Watts it could make,
but about the number of cylinders. If you have a 2 cylinder engine then
it seems like all the power for one side of the stator would end up
coming from one cylinder. That would seem to account for the engine
running rougher when the load was uneven. A 2 cylinder 4-stroke is also
coasting on momentum half of the time, so the resitance on the stator
must be slowing the rotation between power strokes and then it must
burst back to full speed during the power stroke. That would also seem
to lead to rough running and fluctuating frequency.
That's speculation on my part, but Incidentally the 20KW diesel is 4
cylinders.
On 9/21/2020 1:56 PM, Jason Wilson wrote:
Some UPS don't care for an unregulated AC. Either run your current
generator through a line conditioner or go with inverter generators.
The latter would be my choice and is what I use. Way back in the day I
had cisco t1 routers that would not run on a 6kw portable generator. I
had to use my truck inverter to power the site.
On Mon, Sep 21, 2020, 10:49 Adam Moffett <dmmoff...@gmail.com
<mailto:dmmoff...@gmail.com>> wrote:
Ken's answer of "use an inverter generator" is probably the
simplest thing. You'll have way fewer problems than with any
other portable generator. Also "dramatically oversize the
generator" would be a good solution too.
Half the windings on the generator give you a 110v phase. The
other half give you the other 110v phase. Both together gives you
the 220v.
Are both UPS's about 5-6 amps, or is one much heavier loaded than
the other? Are they both on the same phase or are they on
opposite phases? A wiring diagram for the Troy-Bilt 6250 shows
two separate circuit breakers feeding two separate duplexes, so
you'd want to distribute load across them both.
If one phase has more load than the other, then there's more
resistance on one side of the stator. That'll make the engine run
rough and that'll make the frequency unstable. Lights and power
tools won't care, but UPS's will. If that was the issue, then the
engine would run better with a 220v UPS. If the imbalance is real
bad you can even stall the engine. A bigger engine won't care so
much, and an inverter generator doesn't have this issue at all.
At one time when the server room had to run on a 6KW generator I
had lots of problems until I carefully balanced the loads....so
there's my anecdotal/experimental evidence.
There might also be a sensitivity setting on the UPS. I'm not sure
about that specific model, but on some of them you can get into
the management software and change them to be less sensitive about
the AC input.
-Adam
On 9/21/2020 10:22 AM, Josh Luthman wrote:
So Friday we have another 3 phase go down in the building. They
unplugged it all so that wing had nothing.
As a precaution I start up the generator. When they're cutting
the other phases we are using I move it to the generator. The
generator complains and the UPS units don't switch over. I drop
it to say 90% open choke and the UPS switches over - but it's
only 110v. I'd like to know what's going on here.
I have 175 feet of 10 gauge (times 2). Two circuits on the
generator, two runs of copper, two UPS. UPS is doing about 5-6
amps each.
What can I do better? Should I? It runs but I'd like to keep it
as simple as possible to avoid "teaching someone" to lower it
from full open choke.
Josh Luthman
24/7 Help Desk: 937-552-2340
Direct: 937-552-2343
1100 Wayne St
Suite 1337
Troy, OH 45373
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