Re: [SLUG] UPS recommendations?

[Stephen Robert Norris <srn@xxxxxxxxx>]

On Thu, Aug 02, 2001 at 05:03:06PM +1000, DaZZa wrote:
> On Thu, 2 Aug 2001, Stephen Robert Norris wrote:
> 
> > > > I've got 4 PCs, a scanner and a few bits of network hardware that need
> > > > to run on it, plus at least one monitor (21"). My rough estimate would
> > > > be that that's about 600-700VA.
> > > Not even close.
> >
> > Really? Why? The compliance plate maximum draws for the power supplies
> > are in the order of 200W each, and the monitor is 120W, so that's less
> > then 1KVA.
> >
> > At work we have 20 machines with similar power supplies and their total load
> > is less than 5A at 240V... That includes a 15" monitor.
> 
> Watts drawn != VA rating on UPS.
> 
> Check out the following page.
> 
> http://home.earthlink.net/~davefmy/FAQs/UPS_VA_Config/ups_va_config.html
> 
> DaZZa
> 
> 
> -- 
> SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/
> More Info: http://lists.slug.org.au/listinfo/slug

Good point.

Sadly, for these items it's within the error on the UPS's 
loading graph - the machines draw about 60% of it's 3kVA capacity,
or about 1.8kVA. The batteries last about 2x the 3kVA load time,
so that's about 1.5kVA. In either case, each machine is still drawing
less than 100VA each.

So, to restate my second question - why do people think PC power
supplies draw many hundreds of VA?

Ignore the lifetime question; that's a matter of sizing the
batteries; I'm interested in the power electronics here.

	Stephen
-- 
Stephen Norris	  srn@xxxxxxxxx
Farrow Norris Pty Ltd	+61 417 243 239

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