Tuning Filter For Harmonics
Posted 17 November 2007 - 02:00 PM
I have genral question about the tunig of filters for filtering of various harmonics present.
What shall be tuning frequency for 3rd, 5th & other odd harmonics.
I understand the to filter 5th & 7th harmonics, tuning frequency of detuned filter will be 210 Hz.
How to determin this frequency?
Posted 20 November 2007 - 09:08 AM
Welcome to the forum
I presume that you are referring to detuning reactors.
The usual process is to specify the detuning reactor by the percentage (5% or 7%) and the KVAR of the capacitor that it will be connected to. - You do not normally specify the inductance or the tuned frequency.
If you are going to develop your own detuning reactors, you need to be very careful of the tuned frequency and how that shifts with current. As the current through the reactor increases, the reactance will change and the resonant frequency will shift.
The objective of the detuning reactor is to provide a high frequency at higher order harmonics and thereby reduce the harmonic current through the capacitors.
The 5% and 7% figures indicate the reactance relative to the capacitive reactance. The 7% has a lower resonant frequency than the 5% reactor.
Harmonics above the resonant frequency will be attenuated. If the resonant frequency was too low, there would be significant 50Hz current increase due to the effective bandwidth of the resonant circuit.
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