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Can Active and Passive Harmonic Filters be combined in the same system?

If a passive harmonic filter is located upstream in the power system from an active harmonic filter, there is no issue with compatibility.

If a passive harmonic filter is located downstream from the active harmonic filter, the the AHF and the harmonic loads, then there needs to be substantial inductance on the input to the passive harmonic filter to avoid interaction with the capacitor in the filter. Most passive harmonic filters in use today are termed as broadband filters and do have significant inductance on the input so there should be no issue with operating together with an active harmonic filter. This input inductance avoids resonance with the power system. This broadband filter topology is illustrated below.

Broadband type passive harmonic filter wiring diagram

It is not recommended to have a LC type shunt filter downstream from an active harmonic filter. The capacitor in the LC shunt filter can negatively interact with the active harmonic filter. The LC type shunt filter topology is shown below.

LC Type Passive Harmonic Filter Wiring Diagram

Learn more about harmonic filters

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