Effects of discharge channels on field distribution in polymer film capacitors

Summary form only given. For most polymer film power capacitors, the electrodes are made of a thin metallic film evaporated on the polymer film and the electrode metallization is usually segmented to isolate breakdown discharges within the localized breakdown area. Various electrode segmentation patterns have been considered and reported in the literature in order to optimize their capability to isolate individual breakdown discharge plasmas locally and to maintain the nominal performance of the power capacitor as a unit. As an essentially empirical approach, these experimental efforts have seen a significant progress of the polymer film capacitor technology in terms of the improvement of their energy density. In this contribution, an equivalent circuit model is developed to address the above issue. The thin film metallic electrodes are treated as an army of surface resistors, and the formulation of the discharge channel is considered as a parallel resistor to nearby capacitor elements. The resistance of the discharge channel is calculated using a low pressure and low temperature plasma model. A parametric numerical study is then carried out to study the field distribution with different combinations of surface resistance, capacitance, plasma resistance. And the number of segments. With these numerical results the effects of different segmentations and discharge channels on the field distribution are identified. This provide an additional consideration for the design of electrode segmentation.