TRIP SYSTEM FOR AN ELECTRICAL SWITCH HAVING A FAVOURABLE FORCE-PATH-CHARACTERISTIC

摘要

Trip system for an electric 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 extending at a mutual spaced relation and in the same direction from the yoke base part, an armature from magnetic material bridging the free ends of the yoke legs and supporting pivotably by the supporting yoke leg, a permanent magnet provided such that its magnetic field lines extend through the yoke and the armature, a coil mounted on the yoke and spring means engaging the armature. The armature is held in a first position under influence of a magnetic field of the permanent magnet in opposite direction of the spring force of the spring means, in which the armature engages the free end of the first yoke leg. The armature may 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 surfaces facing to each other of the armature and the free end of the first yoke leg are spaced by a first air gap distance. The magnet is included in a second magnetic circuit formed by a yoke and the armature and having in the first position of the armature a magnetic resistance higher than that of the first magnetic circuit and which increases when the armature moves from the first to the second position.