MODELING OF AN ABLATION CONTROLLED ARC

A combination and further development of well known isothermal two-zone models for ablation-controlled arcs is presented. With this new model it is possible to simulate the pressure in the stagnation point and the voltage inside cylindrical tubes in the high-current phase of a 50 Hz half-cycle. All necessary parameters can be determined from the measurements. The time-resolved ratio of arc cross section and nozzle cross section, the transparently radiated fraction of the arc power as well as the arc and the vapour temperature are recalculated from the measurements of arc current, pressure, voltage and mass loss. The distinction of the ablated nozzle material in a surface part and in a part in the depth of the wall is qualitatively explainable by integrating the Kirchhoff-Planck function in two sections. The results of computations for measurements with polyethylene (PE), white, black and optimized polytetrafluorethylene (PTFE) are shown.