UPS Capacity Sizing

[BillP]

We have an APC UPS which has power 120kW/120kVA. This means that UPS has unity power factor. We need UPS to supply the computer load 110kW, power factor 0.8. Is it possible or not to use the UPS? Anyway what is the power factor range of the computer?. Could anyone tell me? Very appreciate in advanced.

[BillP]

We have an APC UPS which has power 120kW/120kVA. This means that UPS has unity power factor. We need UPS to supply the computer load 110kW, power factor 0.8. Is it possible or not to use the UPS? Anyway what is the power factor range of the computer?. Could anyone tell me? Very appreciate in advanced.

[Techie_apc]

If the UPS VA and Watts ratings are same, It means that 100% of the power is being used for useful work.
Click on the below link to know the difference between VA and Watts:
http://nam-en.apc.com/cgi-bin/nam_en.cfg/php/enduser/std_adp.php?p_faqid=1503

I have found the below details in one of the APC K-bases..

Power Factor Corrected (PFC) power supplies are becoming increasingly popular in desktop PC’s in North America. Contributing to this trend is the fact that Energy Star 4.0 compliance as of July 2007, requires the use of PFC in desktop PC’s.

Please see reference to the Energy Star 4.0 compliance Tier 1 at www.energystar.gov/

What is Power Factor and Power Factor Correction?
Power factor is the percentage of electricity that is being used to do useful work. It is expressed as a ratio. For example, a power factor of 0.72 would mean only 72% of your power was being used to do useful work. Perfect power factor (which in this case is being achieved by the computer’s PFC power supply) is 1.0 (unity), meaning 100% of the power is being used for useful work. Power Factor Correction is a circuit design technique to increase the power factor of a device so that it approaches 1, or unity power factor.

You can use the UPS to power the equipment which has got the Power Factor of .8. Please make sure that the equipment you plug in does not exceed the UPS output power capacity.

I hope that this helps.

[voidstar_apc]

Your UPS must satisfy both the kVA and the kW requirements of your computer. You know the kW requirement of your computer. Knowing the power factor (Watts/VA) allows you to calculate the kVA requirement:

        UPS   Computer
kW      120   110
kVA     120   kW * 1/pf = 110*1/0.8 = 137.5

It doesn't look like your UPS meets the kVA requirement.

edit Are you sure your numbers are correct? 120 kVA/kW is a very large UPS and many computer loads. If you're dealing with more than one load, you could move some of your loads to other UPSes.

[BillP · Accepted solution]

Yes, the building has 5 stories and each floor has alot of computers. Thanks for your help.