Electrostatic discharges between charged insulators and grounded spheres

A commercially available electrostatic field solver enables the accurate calculation of the field distribution existing within the air gap between a charged insulating sheet with a grounded backing and a grounded conducting sphere. These data are input to a computer program which uses a breakdown criterion to determine if the field conditions are sufficient to initiate a discharge between the sphere and the insulator. The program decreases the sphere-to-insulator separation until the breakdown strength of the gap is exceeded. The paper presents results for a range of sphere sizes approaching insulators of different thickness. In addition to this, experimental data on the charge transferred by discharge are discussed in terms of the simulated breakdown field strengths. The reported data should be of interest in some specialist areas of electrostatic technologies such as the manufacture and processing of insulating film and sheet.