What is power factor, anyhow?

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In a more-or-less recent thread up yonder (the one about LED lighting that evolved into a discussion/argument about CFLs vs incandescents and power factor, among other things), a technical term and concept (power factor) was argued at length. I wonder how many folks actually were able to follow those arguments.
Myself, I really didn't know just what this mysterious "power factor" was. I did know that values lower than 1 were bad and caused power distribution inefficiencies that resulted in real losses of energy and money.
I now know what power factor is--sort of. The best explanation I ran across on the web was this really simple one. Instead of taking the mealy-mouthed Wikipedia approach of jumping in all cosines and formulae phase angles and other fancy stuff and *then* explaining just what the hell it *is*, this explanation is for the layperson:
Power factor in electricity is like efficiency. The best power factor is 100%.
Consider a child on a swing. If you push them when they are going backwards you will actually slow them down. In order to push with maximum efficiency the motion of the swing and and your push must be "in phase".
Similarly in electricity, voltage and current must be in phase for optimum performance. Equipment such as motors, ballasts and variable speed drives tends to move voltage and current out of phase with each other.
[see at http://www.carleton.ca/energy/powfac.htm ]
Now that's the kind of explanation I like; simple and to the point. Of course, the picky purist might object to the "best power factor is 100%" thing (the best power factor is actually 1), but who cares? Now I understand the concept.
So it turns out that PF is actually computed as the absolute cosine of the phase angle, which also makes sense if one thinks about it. But I still don't really have a handle on the meaning of this number. How low does PF have to get before it's considered really bad? 0.8? 0.5? Don't have much of a handle on that yet. (That's the problem with them dimensionless numbers.)
I still don't know exactly how PF losses work in the real world, though I can take an educated guess that they result mostly in heating in transformers, transmission lines, etc.
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David Nebenzahl wrote: ...

Precisely...
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In typed:

Power factor is simply the phase relationship between voltage and current. In a resistive load they are perfectly in phase. If the load is reactive (capacitive or inductive) then you begin to get a lead or lag between them. Wikipedia.com has a good down to earth description if you're interested. And a lot of good reference links, too.
Twayne
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From a power consumption discussion standpoint, the important thing is; the offset phase may not turn the electric meter as much as a resistive load, resulting in a reduced electric bill. Its not that you are necessarily using less, just not reporting as much.
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Actually, you are "using" less, and that is why the electric meter is spinning more slowly. The meter measures actual power.
Cheers, Wayne
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It's been a long while since electronics school (40 years) & things change or perhaps my instructors were wrong, but I was taught that a wildly inductive or capacitive load would trick the meter into delivering unmetered power.
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I go back 57 years since bachelors degree in EE, and I've never seen or heard of what you said unless the meter was defective.
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On Wed, 30 Dec 2009 18:52:19 -0800, Eric in North TX wrote:

The way I'd always heard it*, the older electro-mechanical meters generally got it right, the digital ones that replaced them didn't, but the current generation of digital meters do measure correctly.
* just FYI. I'm quite possibly wrong ;-)
cheers
Jules
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Now, a prior piece of this thread said it'd generate heat, the "missing" power, and the next one agreeded with that.
How does that assertion jibe with it's "using" less?
(Sorry for the delayed followup.)
David
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On Jan 29, 11:08pm, snipped-for-privacy@panix.com (David Combs) wrote:

They are two seperate but related issues. If the voltage and current are not perfectly in phase you are in fact delivering less power into the loads in the house than you would if they were in phase. That means to get the same amount of useful power into the house, it takes more current. Since wires, switches, etc all have some small but finite amount of resistance, using more current to deliver the same amount of power results in more loss that doesn't do any useful work. If you were an electric utility with miles of wire, this becomes a real issue. However for residential users, the effect is so small that it's insignificant, hence power factor correction isn't an issue.
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Got it.
Thanks,
David
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Twayne wrote:

And to the degree that the load is reactive - or can be made reactive - the KWH meter slows. With a big enough capacitor in parallel with your ac compressor, you get cooling for free.
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In proportion to the reduction in power delivered.

That is completely false. The meter measures the actual power delivered. Those boxes with capacitors are snake oil.
Cheers, Wayne
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On 12/30/2009 6:27 PM Wayne Whitney spake thus:

Well, while I'm sure "Bub" made that remark with tongue firmly lodged in cheek, it's true that capacitors *are* used to correct (raise) PF. See http://www.psnh.com/Energy/ReduceBill_Business/PowerFactor.asp for one reference. So not necessarily snake oil.
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Oh, I see, I missed that.

Absolutely. But as far as I know residential customers are not billed for PF. So if the capacitors are installed near the meter, they won't change your bill at all.
Cheers, Wayne
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On 12/30/2009 7:04 PM Wayne Whitney spake thus:

Well, if installed at the motor (or other inductive load), I guess they could actually *increase* the bill, as by increasing PF they would increase the measurable amount of power metered.
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On 12/30/2009 23:04, David Nebenzahl wrote:

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No, power meters measure the real power, so that won't happen.
Installing power factor correction at the load will actually give you a small reduction in power used. That is because it will reduce current for a given power delivered, so the resistive losses (I^2 R) in the wiring will go down.
Cheers, Wayne
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Wayne Whitney wrote:

Around here, all business get a demand meter and that reading can be as much as half the power bill. A business with a lot of electric motors can definitely benefit from some sort of power factor correction.
TDD
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On 12/31/2009 07:50, The Daring Dufas wrote:

Demand meters record peak real power used over some interval defined by the power company and has nothing to do with PF for billing purposes.
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