Arc running behaviour between parallel rails of different metals and compounds used in miniature circuit breakers

Low voltage circuit breakers in modern AC and DC networks should be capable of cut off operational as well as fault currents. An important influence factor for a successful current interruption is determined by the arc-attachment at the electrodes, supporting or limiting a quick arc-movement to the running-rails and towards the extinction chamber. This work presents experimental results of the investigation of the arc behaviour between parallel rails made of different Ag/SnO₂ compounds, copper and steel. The arc behaviour was observed with a high speed CCD-camera. The results of the experiments show different attachment characteristics of the arc spots depending on material of the rail and polarity. The mean arc-speed was determined for the different materials. The structure characterization of the arc caused damages on the rails shows typical polarity dependent microstructure formations.