Patent ID: 7309973

Claim:
A power controller system for controlling the amount of electrical power supplied to the windings of an AC induction motor that is coupled to a mechanical load, the AC induction motor having at least one motor phase winding, and the controller system including supply input terminals for receiving AC voltage at a fundamental power distribution frequency from one or more selected phases of an AC power source, and supply output terminals for applying AC voltage to one or more motor phase windings of the AC induction motor, comprising in combination: an electronic controller including AC power input terminals for receiving AC voltage at a fundamental power distribution frequency from one or more selected phases of the AC power source, and power output terminals connected to the supply output terminals, and switching means coupled between the power input terminals and power output terminals for controlling the conduction of AC current through each phase; a low pass filter connected in series between the AC power source and the electronic controller, the low pass filter including an input terminal for receiving AC supply voltage from the AC power source and an output terminal for delivering filtered AC supply voltage to one of the controller power input terminals, the low pass filter bring characterized by low attenuation from DC up through the fundamental power distribution frequency to a cutoff frequency, and substantially attenuates current flow at frequencies above the cutoff frequency; and KVAR capacitors connected in shunt from phase to neutral across one or more output terminals of the electronic controller terminal, wherein the capacitance value of each KVAR capacitor is selected and coordinated with the inductance values of the stator phase windings to provide a secondary low pass filter that has low attenuation from DC up through the fundamental power distribution frequency to a cutoff frequency, and substantially attenuates current flow at frequencies above the cutoff frequency.