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VFD harmonic mitigation filters

Generally, VFD manufacturers do not make filters and vice versa. Now you have a finger pointing situation between manufacturers in the warranty period. A packaged solution always turns out to be the most cost effective solutions there is one point of responsibility if a problem occurs. A properly sized product that is most suitable for the application is always better.

Today's active filters are constantly monitoring the equipment and only inject enough corrective current to cancel out the harmonic current in the system. So there is no opportunity to ever see a leading power factor. With passive filters, there is a contactor that is controlled by the VFD to turn on and off the filter to prevent a leading power factor condition. You have 2 devices but as far as function goes, a VFD preforms work and a filter preforms harmonic mitigation. As far as who to blame is simple. No work bad drive. No filtering bad Harmonic device. Remember, you can run a variable frequency drive without a filter, you can't work without a VFD. The bottom line is supply the best solution at the most economical price without sacrificing performance.

I would also like to throw SVC product into the ring here. This uses any manufacturers VFD and monitors the BUS voltage regenerating the energy back into the mains via a Harmonic filter. They have solutions from 7kW up to 1MW and we have been supplying them into a number of industries for many years. On the plus side, it also means you can use an existing installed VFD and retrofit the unit should you be using resistors for the braking power.

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