THERMAL-MAGNETIC TRIPPING MECHANISM

摘要

The invention relates to a thermal-magnetic tripping mechanism for an electrical cut-off device such as a circuit-breaker, including: a magnetic actuator made up of a solenoid (10) connected in series in the circuit, surrounding a stationary core and a mobile core and driving the mobile core between two positions that embody two states of the actuator — inoperative and operative, respectively — in the event of a short-circuit; a thermal actuator including a deformable bimetallic strip (21) made of heat-sensitive material capable of passing from an initial form to a final form that embodies two states of the actuator — inoperative and operative, respectively — when exposed to the heating generated in the thermal actuator in the event of an overload; and means for increasing the impedance of the circuit. Said tripping mechanism is characterised in that said means for increasing the impedance of the circuit consist of a magnetic armature (1) connected in series with the current path of the tripping mechanism between the solenoid (10) and the bimetallic strip (21).