A harmonic filter is a device that mitigates harmonics to tolerable levels. They are commonly used to lower harmonic distortion of the harmonics to the levels detailed in G5/4-1 / G5/5, IEEE519, IEC61000 and the standards on ship and land installations.
Types of harmonic filtering
There are three types of harmonic filters, active, passive and hybrid Filter
Active filters monitor the current and inject currents to mitigate harmonics. The single active filter can be used for filtering of many VSDs of varying sizes. Active filters can also used to compensate for other power quality such as power factor.
Passive filters mainly used to filter a single drive, that is a separate filter is required for each VSD in a multiple VSD system. Passive filters are most effective when used at close to their rated capacity, therefore need to be sized carefully to suit the load.
Hybrid filters combine a number of passive and/or active filters and their structure may be of series or parallel topology or a combination of the both.