At least in any commercial operation I have worked in, this is the way
that it worked:
* power comes in from the wall to the unit
* the unit then supplies power to the computer via the battery
This way, when there is a power failure, there is no loss of power to
the device. Generally most UPS units I have worked with, have protected
and unprotected ports. Therefore, if anything is plugged into the
unprotected ports, those devices will simply shut down on power loss.
On loss of power from the wall, power is continued to be supplied to the
protected devices until the battery power level drops below some value.
On higher end units, this value is configurable, on cheaper units, it is
prefixed at time of manufacture. Once the power level drops to the
critical level, it will then signal the protected device that its
shutdown is eminent, allowing the software to begin an orderly shutdown
of its own.
I have even seen some high end units, have a two level protection, where
it will first signal that it is on battery allowing for dropping of cpu
power levels, dimming displays, and stuff like that. It does that in an
attempt to extend the battery life as long as possible.
Only on the cheapest of units should a UPS begin an immediate shutdown,
and that is because it does not have the AMPs to last very long, so any
loss of wall power puts the unit into a critical configuration
immediately.
Hope that helps
Kevin Fries
On Wed, 2011-12-21 at 11:03 -0700, Dazed_75 wrote:
>
>
> On Wed, Dec 21, 2011 at 10:47 AM, Lyle Tuttle <l.tuttle@cox.net>
> wrote:
> At 10:36 AM 12/21/2011, Dazed_75 wrote:
> > The manufacturer states rather strongly that unplugging the
> > UPS is a BAD way to test it since that also removes the
> > ground circuit. So far, my best idea is to go out to the
> > electrical box and flip the relevant circuit breaker off.
> >
> > The point though, is even that only tests the UPS. I would
> > need to leave it off long enough for the UPS to request (via
> > that USB cable) that the computer do an orderly shutdown
> > which could take 30 minutes or more.
>
>
> Whoa!
>
> My understanding is that when a power failure occurs, the UPS
> takes over supplying power immediately - and also signals the
> system to shut down in an orderly fashion....the 30 minutes
> you mention, IMHO, deals with the amount of time the UPS would
> run the system if it did not shut down
>
> Good point although I don't think it should immediately tell the
> computer to shut down either. What the manual says is "can connect
> your UPS to a computer in order to automatically save open files and
> shut down the computer if it is left unattended during an extended
> power failure" (emphasis added). This makes me think the notification
> would be issued by the UPS after battery power dropped to some level
> or estimated time remaining since the OS would have no clue how much
> battery time remained.
>
> - on my system, by utilizing various power outlets on the UPS,
> I can somewhat control WHAT components shut down right away.
>
> What if you plug the UPS into a switchable power strip - then
> turn it off?
>
>
> Another good point, that should retain the ground connection. Eric
> made the same suggestion.
>
>
> > And worse, I would not know if a non-event meant a failure
> > on the part of the UPS signaling system or the Linux side
> > not making use of the signal event since I still have no
> > idea what to check for.
> >
> > I bring all this up because my last UPS failed to protect
> > the computer so now I am paranoid about it.
> >
> > On Wed, Dec 21, 2011 at 8:27 AM, Alex Dean
> > <alex@crackpot.org> wrote:
> >
> >
> >
> > On Dec 21, 2011, at 2:06 AM, Dazed_75 wrote:
> >
> > > I just put in a replacement UPS (Tripp-Lite
> > G1010USB) and connected the USB cable. I see that
> > Ubuntu 10.04 does see it but I have no idea how to
> > tell if it will actually pay attention if the UPS
> > ever tells it to shut down. Short of a power
> > failure, how can one know?
> >
> > Unplug the UPS from the wall?
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