Effects of the presence of grounded shield in the proximity of high-voltage corona electrodes collection plates

Abstract

Corona discharge generated by various electrode arrangements is commonly employed for several electrostatic applications, such as charging of insulating materials in electrostatic separators. The aim of the present paper is to analyze the effects of the presence of a grounded metallic shield in the proximity of a high-voltage corona electrode facing a grounded plate electrode. The experimental study is first performed using a wire-plane configuration, with the dual corona electrode consisting in a thin ionizing wire parallel with a metallic cylindrical support, at same high voltage supply. The assembly is placed inside a rectangular box made of aluminum and opened in the lower portion facing the plate collecting electrode. The metallic grounded shield is expected to increase the current intensity and decrease the inception voltage of corona discharge. For the second set of experiments, a layer of insulating polymer is placed on the surface of the electrode plate to investigate the influence of the shield on charging current intensity. In other experiments the current density repartition at the surface of the plate electrode is measured, to show the efficiency of shielding on the development of corona discharge. Finally, these experiments are discussed in relation with the results of the numerical analysis of the electric field generated by the wire-plate configuration with and without shield.