Circuit interrupter with an improved magnetically-induced automatic trip assembly

Abstract

A circuit interrupter including a housing, separable main contacts disposed in the housing, and an operating mechanism disposed in the housing and interconnected with the contacts. A trip mechanism is disposed in the housing and includes a rotatable trip bar assembly that, when selectively rotated, generates a tripping operation that causes the contacts to open. The trip mechanism further includes an automatic trip assembly for selectively rotating the trip bar assembly upon a predetermined current threshold. The automatic trip assembly includes a magnetic yoke having two arms with a pivot support on the top of each. Each of the pivot supports includes a pivot surface, and one of the pivot supports includes a rear retaining protrusion adjacent its pivot surface. The other of the pivot supports includes a front retaining member adjacent its pivot surface. The automatic trip assembly further includes an armature having pivot portions positioned on the pivot surfaces which provides for rotation of the armature between a first position away from the arms and a second position closer to the arms. A magnetic field is generated upon the predetermined current threshold which causes the armature to rotate from the first position to the second position and to rotate the trip bar assembly. One of the pivot supports also includes a downwardly facing stop. The downwardly facing stop is positioned to abut the armature when the armature is rotated away from the arms, thereby defining the first position.