DC corona charging and its surface charge decay on acrylic disc in atmospheric air

摘要

The decay of surface charge on dielectric material in atmospheric air was studied. A dielectric disc with a thickness of 0.1 cm placed on the plane electrode in a rod to plane room air gap of 2.0 cm long was charged by DC corona discharges with the positive and negative polarities. The dielectric disc made of acryl PMMA has 16.0 cm in diameters. The surface potentials induced from the accumulated surface charges were measured by an electrostatic voltmeter which can be controlled automatically by computer at 0.5 cm intervals in the direction of X and Y. In the measurement, it was observed that the bell shaped initial surface potential distribution was decayed into a crater like shape with time. In order to make clear the mechanism of surface charge decay, we compared the measured charge decay characteristic with calculated decay result. The simulation model assumes that the ions generated by natural ionizing process in the air move along the line of electric force emitted from surface charge distribution, and then these attracted ions neutralize with surface charges. The performed simulation model could evaluate the measured result well.