Patent ID: 7378754

Claim:
A three-phase filter for mitigating harmonic currents in a power distribution system, said filter comprising: a first power source connector, a second power source connector, an a third power source connector each for connection to a different phase line from a three-phase power source; a first load connector, a second load connector and a third load connector for connection to a power consuming apparatus; a magnetic core of a magnetically permeable material; a first phase filter comprising a first line winding connected between the first power source connector and the first load connector and wound on the magnetic core in an orientation that produces magnetic flux having a first polarity, a first shunt winding wound on the magnetic core in an orientation that produces magnetic flux having a second polarity opposite to the first polarity, a first resistor and a first capacitor connected in series with the first shunt winding between the first load connector and the second load connector; a second phase filter comprising a second line winding connected between the second power source connector and the second load connector and wound on the magnetic core in an orientation that produces magnetic flux having one polarity, a second shunt winding wound on the magnetic core in an orientation that produces magnetic flux having a opposite polarity to the one polarity, a second resistor and a second capacitor connected with the second shunt winding between the second load connector and the third load connector; and a third phase filter comprising a third line winding connected between the third power source connector and the third load connector and wound on the magnetic core in an orientation that produces magnetic flux having a given polarity, a third shunt winding having one end wound on the magnetic core in an orientation that produces magnetic flux having an opposite polarity to the given polarity, a third resistor and a third capacitor connected in series with the third shunt winding between the third load connector and the first load connector.