Influence Of Space Pressure On Dielectric Properties Of Pulsed Power Insulation

The influence of low atmospheric pressure on the dielectric properties of three pulsed power insulating materials, Polyimide (PI, Kapton), Polypropylene (PP) and Polyvinylidene Fluoride (PVDF, K-film) is investigated. This pressure approached the critical pressure x distance,(pd), on the Paschen curve. Three layers of the dielectric films, with and without an artificial void in the middle layer, and sandwiched between two measuring electrodes connected to a high precision high voltage capacitance bridge were used. The dielectric constant and the dissipation factor were measured for the insulating materials for different pressures ranging from 760 torr to 4 torr as a function of the applied voltage. The results of the first configuration (three layers of a single dielectric material without an artificial void in the middle layer) showed that as the pressure is reduced, slight increase in the dissipation factor occurred. In the second configuration (three layers with an artificial void in the center layer), the increase in the dissipation factor was greater than in the previous case, particularly for the high dielectric constant PVDF film. There was no appreciable change in the dielectric constant and dielectric strength of both configurations.