Carbon Electrode in Electroic Spark Discharge

I-Electro-Discharging Properties in Air and Physical Properties of Carbons

Abstract

The electro-discharging tests in air under repeating, continuous and impulsive discharges have been examined respectively on the carbon electrode made of the commercial carbon brush materials. Although the photomicrographs of the carbon electrode exposed to the stable discharge show a rather smooth fine surface, those of the carbon electrode exposed to the unstable discharge show an uneven rough surface and large craters.
The larger the electric conductivity, the flexibility (flexural strength/Young's modulus), and the thermal shock resitivity (thermal conductivity x flexural strength/Young's modulus x thermal expansion coefficient) of the carbon electrode are, the smaller the consumption rate due to continuous discharge, the voltage change and the degree of stiort-circuit due to impusive discharge.
It seems that the above mentioned physical properties of carbon electrode do not contribute separately but in combined form to the electro-discharging properties. These relations are discussed by using the dimensional analysis and the consumption resitivity has been deduced from thermal eqilibrium equation assuming that the consumption of electrode is due to only the thermal effect of electric discharge. The larger the consumption resitivity of carbon electrode is the smaller the consumtion rate due to continuous discharge and the degree of short-circuit due to impulsive discharge.