Experimental study of corona discharge generated by a triode electrode system

摘要

The triode electrode system is frequently employed for accurately controlling the corona charging of insulating materials. It consists of a high-voltage corona electrode, a grounded plate electrode, and a grid electrode between them. The aim of the present paper is to analyze the characteristic features of a particular type of such an electrode system, and formulate a few recommendations on its design and use, in order to increase the efficiency of the charging process. The experiments were performed with a high-voltage wire-type dual electrode, located at a distance 20 to 45 mm above a grounded plate electrode (Aluminium; 165 mm × 115 mm). The distance between the metallic grid and the ground could be varied between 10 and 30 mm. The corona electrode consisted of a tungsten wire (diameter 0.2 mm) supported by a metallic cylinder (diameter 26 mm) and distanced at 34 mm from its axis. The wire and the cylinder were energized from the same adjustable high-voltage supply 100 kV, 3 mA. A well-defined potential was imposed between the grid and the grounded plate. In some experiments, a non-woven Polyester medium (sheet thickness: 400 μm, average fiber diameter: 20 μm) was placed on the surface of the grounded plate, to be charged by the corona discharge. The current-voltage characteristics of this type of electrode system were obtained for different values of the inter-electrode spacing and grid to ground distances, with and without the Polyester medium. Decreasing the distance between the electrode and the grid caused the increase of the corona current density, but the discharge zone was concentrated in a narrower zone at the surface of the collecting electrode.