Electrode erosion of high-current pseudospark switches

The lifetime of pseudospark switches is mainly limited by electrode erosion. For microsecond pulses and peak currents of about 100 kA, the measured erosion rates show distinct differences, varying between 20 and 500 /spl mu/g/C for molybdenum electrodes. Up to now there is no clear correlation with parameters like peak current and pulse length, to which erosion is normally related. For peak currents exceeding 40 kA the discharge is statistically distributed on the plane electrode during current maximum, the main erosion takes place in the bore-hole region where the discharge is located after triggering. In this paper, various experimental data obtained for different discharge parameters and electrode materials are compared and the influence of the high resistance commutation phase on electrode bore hole erosion are discussed with the help of a simple model considering evaporation of electrode material. Depending on discharge parameters, the main electrode erosion can either be related to parameters determining erosion during the commutation phase like charging voltage, current rise and voltage breakdown, or parameters which cause erosion during the main discharge like peak current, voltage drop, pulse length and total charge transfer.