No-Load P.F. in Static UPS Systems

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jinxnao Power-User Join Date: Mar 2007 Posts: 310	No-Load P.F. in Static UPS Systems 03/04/2013 2:27 PM
	hello, what happens when a static UPS (say,big ones like 200-1000 KVA ) lightly loaded ? I mean there are many capacitors such as input/output filter capacitors, and DC. busbars capacitors.. embedded in these systems , so if we have a pfc circuit in the rectifier side, does it mean we have always a p.f near 1.0 ? Or do we have an exception in no/light load conditions? __________________ jinxnao
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#1 Re: No-Load P.F in STATIC UPS systems 03/04/2013 5:42 PM
	I assume that you are asking how the UPS looks to the power system that is feeding it. If so then it will depend upon its age, price and design. Age, because older designs didn't care about the power factor they presented. Price, because not every buyer wanted to pay for PFC circuitry. Design, because again PFC wasn't an essential design criteria. More modern designs have PFC built-in or as an option, and will use circuitry to regulate how it appears to its AC supply independent of the load that it is supplying. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#2 Re: No-Load P.F. in Static UPS Systems 03/05/2013 3:14 AM
	The power factor in a circuit with no load is zero, by definition. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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cuba_pete Guru Join Date: Dec 2010 Posts: 1895 Good Answers: 44	#3 Re: No-Load P.F. in Static UPS Systems 03/07/2013 3:11 PM
	PF at the input, or PF at the output? PF at the input (as seen by the utility) should be as near to 1.0 as is achievable by the UPS taking into account several factors (as delineated by other posters here). PF as seen by the UPS would be maintained as near to 1.0 as possibly by properly balancing your panels/loads. Efficiency is ultimately up to the end-user.
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