Temperature Effect on Space Charge Behavior of Polyimide Films under DC High Electric Field

As an excellent insulating material, polyimide (PI) film has advantages of low dielectric loss, good thermal stability and high insulation performance. At present, researchers mainly focus on discrete space charge distribution in the polarization process of polyimide at a certain temperature, and those studies cannot illustrate the dynamic process of space charge intuitively. In this paper, dynamic process of space charge was measured through PEA method in both polarization and depolarization process under electric field of l00kV/mm at 30, 50, 70, 80°C for 30 minutes, respectively. The internal trap distribution of polyimide films was measured through isothermal relaxation current method at 30°C to assist the understanding of dynamic process of space charge. The consequences indicate that temperature affects the formation rate of space charge distribution in polyimide film. Below 70°C, if the temperature gets increased, time caused by space charge to get stable decreases. If continue to heat up, the acceleration is not obvious. During the polarization process, the temperature affects the final space charge distribution in PI films. During depolarization process, the charge dissipation rate in polyimide films gets faster if temperature gets boosted.