Active Harmonic Filters

These are electronic devices which can be suitably installed at selected points in a building or industrial plant electrical distribution system which will approximately cancel harmonics. Harmonics are normally caused by loads such as printers, computers, variable speed drives, MRI units, and other nonlinear operational devices. In some cases the harmonics can lead to large circulating currents, reduced transformer and electric cable capacity for normal loads, and the cause of nuisance breaker trippings. In extreme cases, harmonics can burn up the neutral of power distribution systems, leading to unscheduled outages of power. Energy cost savings can vary substantially, depending on the level of harmonics, which must be measured; KWH savings can vary from 1-2% up to 10-15% in extreme situation.