The UPS is rated for a resistive load of 3kW.  The PC is a reactive load
of 200W so you use the power factor correction to equate it to a
resistive load of 280W.  Now everything is resistive so you divide 3kW
by 280W to get 10.7 PCs, round to 11 or more unless everybody is going
to spin up their hard drives at the same time.

Sherpa Doug

> -----Original Message-----
> From: Micro Eng [mailto:micro_eng@HOTMAIL.COM]
> Sent: Friday, December 07, 2001 12:46 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: UPS's, powerfactors, and computers
>
>
> ok...smart folks...
>
> You have a 200Watt (as rated by the manufacture) powersupply for your
> computer. UPS's come in various sizes, say a 3KVa, so thats 3000 VA of
> power. But its rated for pure resistive circuits.  Backed off
> for a power
> factor correction of .7 roughly, you get 2000 watts of power
> avaiable to
> your devices.  Now, do you account for the power factor for
> the power supply
> against the 2000 watts? ie...200 watts is PF corrected to
> around 280 watts.
> So does that mean that you can hook up only 7 computers? Or
> do you use the
> non PF of 200 watts and lets you hook up 10 computers.  Or do
> you use the PF
> of 280 against the non corrected UPS value of 3000 watts?
> None of them seem
> to add up the same.  I believe that you use the PF of the UPS
> and the non PF
> of the power supply?  Need to figure this out rather soon.
>
> thanks a bunch
>
>
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