Patent ID: 6768626
Filing Date: 2004-07-27
Classification: H01H

Abstract:
Trip system for an electrical switch, comprising a yoke of magnetic material, consisting of a yoke base part, a first yoke leg and a second supporting yoke leg, said first and second yoke legs extend in a mutual spaced relation and in the same direction from the yoke base part and transversally thereto, an armature from magnetic material bridging the free ends of the yoke legs and pivotably supported by the supporting yoke leg, a permanent magnet provided such that its magnetic field lines extend through a first magnetic circuit formed by the yoke and the armature, a coil mounted on the yoke and spring means engaging the armature, in which the armature is held in a first position under influence of the magnetic field of the permanent magnet against the spring force of the spring means, in which the armature lies against the free end of the first yoke leg and in which the armature can assume a second position under influence of the magnetic field developed by a current flowing through the coil and exceeding a predetermined limit value, in which the surfaces facing to each other of the armature and the free end of the first yoke leg are at a first air gap distance from each other, characterised in that the magnet is included in a second magnetic circuit formed by the yoke and the armature and which in the first position of the armature has a magnetic resistance being higher than that of the first magnetic circuit and is decreasing when the armature moves from the first to the second position.