Patent ID: 6023110
Filing Date: 2000-02-08
Classification: H01H

Abstract:
Switching equipment with an electromagnetic contactor and a circuit breaker located ahead of the contactor, the contactor having an operating magnetic circuit with a magnetic core, an operating coil, an armature which moves in dependence on the current through the operating coil, and a number of contacts which are influenced by the armature, the switching equipment further comprising detection circuits for sensing the reluctance of the operating magnetic circuit and, in dependence on the measured reluctance, generating a signal which indicates an incomplete opening of the contactor caused by welded-together contacts, said signal being supplied to the circuit breaker so that, upon detection of welded-together contacts, the contactor is disconnected by opening of the circuit breaker, wherein the detection circuits measure the reluctance of the operating magnetic circuit by sensing the inductance of an inductance measuring coil surrounding the magnetic core, and wherein the detection circuits apply to the inductance measuring coil a voltage pulse and detect the inductance of the coil on the basis of the current response of the coil.