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'[EE]: Power Factor'
2002\05\07@134150 by

Hello piclist,

Anyone can suggest a method to measure power factor in AC lines.
Specially considering noisy enviroments and poli-harmonics
conditions.

--

This company makes an embedded pic meter to measure power factor among
other things.
Pricey but excellent quality and specs.
http://www.brandelectronics.com/specs1.htm
Rick

Digiled dot com wrote:

{Quote hidden}

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I suspect that if that "stuff" is on the power line, then it is

Take many samples of volts and amps.
For each sample, calculate rms volts, rms amps, and rms watts.
After you have enough samples, multiply rms volts times rms amps.
It (rms VA) will be larger then rms watts.  That's your power
factor, which I think (anyone?) is just (rms watts)/(rms VA)

Barry

At 02:40 PM 5/7/02 -0300, you wrote:
{Quote hidden}

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Hi,

maybe a simpler approach:

- do a lowpass filtering of current and voltage (it changes phase angle,
but do not mind as both change in the same way)
- detect the zero-crossing point for both, regarding only voltage increase
- measure the time between them (lag)

power_factor = cos(tlag / tper * 2 * pi)

(there is a divisor of 4 in both side but disappears).

I hope this helps.

Regards,

Imre

On Tue, 7 May 2002, Barry Gershenfeld wrote:

{Quote hidden}

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Hello System,

SA> - do a lowpass filtering of current and voltage (it changes phase angle,
SA> but do not mind as both change in the same way)
SA> - detect the zero-crossing point for both, regarding only voltage increase
SA> - measure the time between them (lag)
SA> power_factor = cos(tlag / tper * 2 * pi)
SA> (there is a divisor of 4 in both side but disappears).

Yes, but i supossed that in poli harmonics measurements you must
consider all the the frecuencies, so It might no be possible to
filter V and I. Actually, I'm using this way but I browsing into another
alternatives. thanks anyway.
--
Best regards, Gus

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