Patent ID: 7804198

Claim:
A device for substantially eliminating harmonic currents in supply lines of a 3-phase electrical distribution system with a Phase A line, a Phase B line, and a Phase C line for supplying power from an AC source to an adjustable-speed drive, the device comprising: a completely-passive parallel resonant circuit having three passive electrical branches connected in parallel; wherein the completely-passive parallel resonant circuit having an almost infinite impendence at a third harmonic frequency of a fundamental frequency of the AC source to prevent the formation of only the third harmonic frequency so that there is no third harmonic current to remove or dissipate as heat, wherein the three passive electrical branches comprise a first branch including a capacitor, a second branch including a reactor, and a third branch including a resistor, and wherein the completely-passive parallel resonant circuit being electrically connected in a single phase manner near the adjustable-speed drive to a supply line connected to the AC source, wherein the supply line comprises a pair of phase lines selected from the group consisting of a Phase A line/Phase B line pair, a Phase B line/Phase C line pair, and a Phase A line/Phase C line pair, whereby the device renders the electrical distribution system free of the third harmonic frequency both toward the drive and back to the AC source.