Analysis of Cathode Surface State and Cathode Temperature Distribution After Current Zero of AMF-Contacts

The aim of this work is to compare the state of cathode surface of different AMF contact systems during arcing and after arc extinction. The arcs were ignited by opening of electrodes and were fed by half-sine current pulses with duration of 10 ms. CuCr electrodes were used. Investigations were performed in the range of arc currents from successfully interrupted ones by the contact system up to the levels of guaranteed interruption failure when transient recovery voltage was applied. The measurements were done by a high-speed Phantom M310 video camera equipped with a Carl Zeiss 100/2 macro lens. The cathode surface temperature distribution just after current zero was obtained by comparison of results of cathode surface recording and the results of calibrated band-lamp recording in identical conditions. Reflection of anode radiation from cathode surface was taken into account. The recording was carried out using an interference filter. The cathode surface state during arcing was studied using the set of dense neutral filters. Obtained results show the difference between the cathode and anode condition during arcing with the same currents. It was found that switching failure can be provoked by the cathode and by the anode processes depending on contact system construction.