Contact assembly for switch filled with pressurised gas - has bore of stationary contacts coated with graphite to minimise erosion during arcing at switch=off

摘要

The switch or circuit breaker contains two stationary, coaxial, tubular contacts, each with a graphite nozzle. The contacts are located in a bridging contact with spring-loaded contact fingers. Two switch off, one contact (5) is moved together with a blowing cylinder, so that the gas is compressed in a cavity. In each contact is a tube made of ferromagnetic material, esp. steel, with a conical bore coated with a layer of graphite. In similar conventional switches, the arcing which occurs at switch-off causes the burning and erosion of the steel tube. The graphite layer used in the present arrangement reduces the burning-off, so that the switch can be used for higher electric currents and/or its working life increased.