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Harmonic filter

Harmonic filter

Harmonic filter

(OP)
hello, i wonder why is a harmonic filter  designed as a series reactor with pfc capacitors and this reactor filters at one frequency (189, 215 hz). what if we design reactors and connect them as shunts to the common pfc busbar and they filter only unwanted and dominant ones? can u explain pls..

RE: Harmonic filter

Simple to think of it as just a filter.  In power systems it is typical for harmonic distortion to usually be worse at a specific order.  Perhaps it is simply cheaper doing it the more conventional way you mentioned.  In theory what you suggest should work, but there could be other issues that come into play when shunting a reactor, such as limiting ground fault current for relaying?

One speicific reason I can think of for using a notch filter (typical harmonic filter for power systems) is to not interfere with possible power line carrier.  It is interesting to note, however, that power line carrier systems also have filters to keep their signals out of where they're not supposed to be (wavetraps).

RE: Harmonic filter

Trying to understand what you propose. So you are saying have 2 or more reactors at different inductances each with one end on the mains bus and the other end at a bank of PF caps?  If this is the proposal, then effectively it looks like a single reactor at the new inductance of the paralleled inductors.

Basically the series reactor  in a harmonic trap detunes the parallel circuit containing the caps with respect to the source. So source harmonics are not loading the trap circuit. The trap circuit (parallel reactor and caps are tuned relatively close to the dominant harmonic of the harmonic load (drive or similar). Usually eliminating the dominant harmonic is enough to relieve significant distortion.

Neil

RE: Harmonic filter

(OP)
what i tell about is that we have caps for pfc and mount the inductors series with them and resonant frequency is for example 189 hz. this is what we do, But i ask you what if mount inductors separately on the bus  for each harmonics so that every order will be filtered. Yes in fact it seems that they act like only one inductor but what will be the harmonic currents if they have a convenient inductor on the bus wont they flow over them separately? it seems a bit paradoxal.

RE: Harmonic filter

(OP)
i am wrong, there cant be any filter with only inductance, disregard this question pls..

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