An Analysis of the Instability Mechanism of a Low-Current Metal Vacuum Arc for Silver Based Cathode Material

The purpose of this research was to investigate instability phenomena in low-current metal vacuum arc using the calculation data comparison with the experimental data. The instability phenomena are characterized by noise on the current trace prior to the actual current chopping. The instability Current was investigated for various electrode materials. To study the parameters affecting the stability arc factors, the parameter scan of cathode materials and ion current fraction by numerical analysis, it was found that the critical current of the stable current is highly dependent on the thermal conductivity of the cathode material. However, the thermal conductivity effect on the instability phenomena of low-current metal vacuum arc was important for low surge switching electrode material development. Therefore, the experiment of major commercial switching electrode such as Ag-Pd is performed in this study. The arc during time and the maximum arc current were fixed to 8 ms and 100 A. respectively. The vacuum was maintained to about 1*10(-6) Pa. The observed waveforms, instability current, chopping current are measured by the oscilloscope. As a result, the critical current of the stable current is inversely dependent on the thermal conductivity of the cathode material. This is very important result for the development of cathode materials for low-surge vacuum interrupters.