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Active Contributor

Join Date: May 2012
Posts: 14

### Harmonics in PF Correction Capacitors

09/21/2012 3:52 AM

Dear all.
As we all know that in PF correction we use bank of capacitors to keep the power factor value nearly around 1.
But considering harmonic currents in mind we use an inductor in series with capacitor.

my question is how to calculate the the value of inductor to be connected in series with capacitor.?
Or Kindly let me know how to calculate the harmonic current flowing.?

Thank you.

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Guru

Join Date: Oct 2007
Location: India
Posts: 1272
#1

### Re: Harmonics in PF Correction Capacitors

09/21/2012 4:19 AM
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#6

### Re: Harmonics in PF Correction Capacitors

09/22/2012 2:43 AM

Read more than once. GA Joshi.

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Guru

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing. Kettle's on.
Posts: 19628
#2

### Re: Harmonics in PF Correction Capacitors

09/21/2012 4:33 AM

Use the equations for tuned circuits in radio frequency work, with the frequency set to 50 or 60Hz as applicable. The principle is to alter and match the characteristic frequency of the [cable and the load] to the frequency of the supply.

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Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#7

### Re: Harmonics in PF Correction Capacitors

09/22/2012 3:53 AM

Yes on the tuned circuit theory. But not as a band pass filter. Be careful here.

The tank circuits would be for 100 or 120Hz, 150 or 180Hz, 200 or 240Hz.......depending on which harmonic is dominant in the application.

If you tune it for 50 or 60Hz you will create a short circuit at the line frequency. Not good.

It needs to be resonant at the harmonic to be eliminated.

That frequency is determined by measurement of the harmonics. More than 1 harmonic may need elimination, and therefore more than one resonant filter may be required.

Joshi's references explain this clearly and very well with worked examples.

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Difficulty is not an obstacle it is merely an attribute.
Guru

Join Date: Oct 2009
Posts: 1866
#3

### Re: Harmonics in PF Correction Capacitors

09/21/2012 9:56 AM

Are you interested in a tuned filter or in a de-tuned filter?

Power-User

Join Date: Nov 2011
Posts: 170
#4

### Re: Harmonics in PF Correction Capacitors

09/21/2012 3:56 PM
Guru

Join Date: Jan 2008
Posts: 1627
#5

### Re: Harmonics in PF Correction Capacitors

09/22/2012 12:48 AM

The question in its original form CANNOT be answered in a meaningful sense.

How much harmonics (Frequency, power, phase) is to be reduced by how much?

What is the circuit's description?

By the time you learned enough to specify, you barely know enough to go back to the manufacturer's engineering department with.

By the way, the bank of capacitor IS NOT the answer.

On the other hand, since you pay the bill, you can experiment, and pay and pay.