# Power Factor Correction With Detuned Reactor

### #1

Posted 24 October 2007 - 05:26 PM

### #2

Posted 24 October 2007 - 06:16 PM

Welcome to the forum.

Detuning reactors are strongly recommended in environments where there are high harmonic currents.

The issue is that the capacitor appears as a very low impedance to the higher frequencies and therefore carries a higher current if there are harmonic voltages present. The impedance of the capacitor reduces with the inverse of the frequency, so the higher the harmonic, the lower the impedance and the higher the harmonic current through the capacitor.

For example if we have a capacitor that carries 10 Amps at 230V 50 Hz, and we have 2.3 volts at 500Hz (1%), then the current due to the 500Hz will be 1 Amp (10%).

The detuning reactors are put in series to ensure that the total impedance does not fall for increasing frequencies and therefore reduces the harmonic current that flows through the capacitors.

When you have a series reactor capacitor circuit, you have a resonant circuit. It is important that the reactors match the capacitors. These are specially sized to ensure that the series resonant circuit is well away from any likely harmonic frequencies.

Because of the resonance, transients will cause ringing voltages in the capacitors and these can be well above the supply voltage. It is recommended that the capacitors should be capable of withstanding 525 volts for an average supply or even higher for a bad supply.

When the KVAR rating for a capacitor is given, it is given at a particular voltage and frequency. This is because the current through the capacitor changes with voltage and frequency. The KVAR for a fixed frequency, increases with the square of the voltage.

Many manufacturers of power factor correction capacitors manufacture a range of capacitors for use with detuing reactors. These capacitors are designed for the higher voltage, but are given KVAR ratings at the nominal supply voltages.

Best regards,

Mark Empson | administrator

Skype Contact = markempson | phone +64 274 363 067

LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | Soft Starters

### #3

Posted 09 November 2007 - 01:09 PM

1. The actual measured capacitor terminal voltage is higher. How much

higher depends on the size of the reactor. The 440 V you were recommended

might be a conservative capacitor rating.

2. Adding a detuned reactor does make the apparent size of the capacitor bank

increase. See my earlier post on "Detuned Reactors".

Thanks,

Submonkey

### #4

Posted 16 December 2008 - 04:16 PM

why 7% reactors are used ? how harmonics are improved in single phase loads ? what is a low pass filter ?

waiting for ur reply

thanking you

bt pagar

### #5

Posted 18 December 2008 - 05:29 AM

Welcome to the forum.

Connecting an inductor in series with a capacitor creates a series tuned circuit.

It important to ensure that the series resonant circuit does not resonate at the line frequency or harmonics of it.

Using a 7% reactor ensures that the resonant frequency is well away from supply harmonics.

The use of detuning reactors reduces the harmonic currents flowing into the capacitors if the supply voltage is disorted.

Detuning reactors do not improve the haromincs in the connected load.

Best regards,

Mark.

Mark Empson | administrator

Skype Contact = markempson | phone +64 274 363 067

LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | Soft Starters

### #6

Posted 25 February 2010 - 05:15 PM

Why %7 why not %14 or 5,6 what is criteria of choosing harmonic filter ?

Thanks.

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