power factor correction

[marley821]

Hi guys, I was wondering if anyone could explain power factor correction to me. I have been asked to go to a job next week to fit pfc to two screw compressor machines. Am I right in thinking it is something to do with the 3 phase cycle frequency (ie up and down) and trying to keep this more constant rather than up and down? I suspect there may be more to it though, anyone be of help with this?

Thanks

[Peter_1]

No, it isn't that.
You have reactive power and active power.

If you divide active power by reactive power (apparent power sometimes named ) and take the tangent of it, then you have the power factor.
1 is perfect 0.93 is satisfactory, 0.8 is bad.

Reactive power is something bad for the company who delivers the energy to you.
They penalise you very high for the difference between active and reactive power.

So, you have to install a condensator battery so that the power factor becomes 0.93 or more. I think that there's a difference by country ow low you can go before they penalise you.

As load varies aon the screws I suppose, so may also the power factor.
So the best is if you install a self regulating correction capacitor battery.

Try to measure once this power factor how low it goes when it's running on its lowest capacity step. It's possible that you can install a fixed capacitor pack.

http://www.energyideas.org/documents...ducing_pwr.pdf

http://www.bchydro.com/rx_files/psbu...siness1531.pdf

http://www.lambda-emi.com/pdfs/appli...93008513rA.pdf

http://en.wikipedia.org/wiki/Apparent_power

Practical
http://www.lmphotonics.com/pwrfact.htm

[marley821]

Thanks for that Peter I will read the links you have provided and hopefully it will make a bit more sense!

[The MG Pony]

Erf A/C harmonics is a head ach, look at it as a 3d wave kinda helps. Still makes your brain impload though!

[Peter_1]

Don't mix both: power factor and harmonics are something completely different.
The first is solved with capacitors and the second with LC filters.

VFD's can cause serious harmonics on the net which disturbs electronic equipment.