Rapid electromagnetic trip for low-voltage switchgear contacts - ensures positive tripping without rebound when overcurrent in coil augments force of spring opposing permanent magnet

摘要

A tubular ferromagnetic trip element (14) is seated on a permanent magnet (2) which holds it against the force of an energy-storage spring (13). One ferromagnetic portion (14a) of the sleeve (14) projects into a coil (12) through which the load current flows. A short-circuit adds the force exerted by the coil (12) to that of the spring (13), lifting the sleeve (14) swiftly and irreversibly into the tripped position and preventing reclosure. ADVANTAGE - Operates irrespective of direction of current, and without any auxiliary control, to prevent welding by currents which just attain trip threshold.