A passive or active filter installed on the elevator power supply to reduce harmonic distortion generated by variable frequency drives.
Full Definition
The elevator harmonic filter is a power quality device that attenuates current harmonics (primarily 5th, 7th, 11th, 13th) generated by the non-linear loads of variable frequency drives in the elevator system. Unfiltered harmonics cause transformer overheating, neutral conductor overloading, interference with sensitive equipment, and voltage distortion that may violate grid utility connection agreements (EN 50160, IEEE 519). Passive harmonic filters use tuned LC circuits for specific harmonic orders. Active harmonic filters (AHF) inject counter-phase currents to cancel a wide spectrum of harmonics in real time. Installation is typically at the main supply distribution board serving multiple elevators. THD (Total Harmonic Distortion) measurements before and after filter installation document effectiveness. Filter sizing is based on drive kW ratings and number of drives.
