Contact arrangement for a circuit breaker using magnetic attraction for

Abstract

A contact arrangement for a circuit breaker utilizes magnetic attraction between parallel conductors in the movable contacts to open the contacts during a short circuit, high current condition. An elongated, pivotable, main contact arm includes a movable main contact at a first end that engages a fixed main contact in a closed circuit position. An elongated, arcing contact arm, pivotable in the same plane as the main contact arm, includes a movable arcing contact at a first end that engages a fixed main contact in a closed circuit position. The contact arms are spring biased in the closed circuit position such that a gap is defined between the arms. An attractive electromagnetic force tends to keep the first end of the arcing contact arm in contact with the fixed arcing contact until after the main contact arm has lifted. A hinge assembly for the main contact arm and the arcing contact arm assists in opening the contacts during the high current condition. The hinge assembly includes elongated first and second hinge members defining a gap therebetween and providing a second pair of parallel conduction paths for the circuit. The hinge members support the main and arcing contact arms at their second ends distal from the fixed main contacts. The attractive electromagnetic force generated by the parallel currents in the hinge members levers the first ends of the contact arms up from their closed circuit position, thus helping to open the contacts and trip the breaker. The first end of the main contact arm can lift from the fixed main contact with such speed that it knocks the arcing contact arm into the open circuit position.