Characteristics of a corona system under negative direct and pulsed voltage

The characteristics of a clean electrode system energised in clean atmospheric air are studied when the applied voltage is negative direct and negative pulsed respectively. The discharge patterns along the wire electrode are measured by means of an optical system which includes a photomultiplier. A linear relationship is found to exist between the average photon current and the corona current. When the photon currents are the same, the discharge patterns are similar for both types of applied voltage. The Trichel current waveshapes are also similar at low voltage levels. However, at high pulsed voltage values, the Trichel current amplitude and frequency are affected by the space charge conditions.