CURRENT OVERLOAD MODE INFLUENCE  ON ELECTRICAL CAPACITORS PARAMETRS

We have experimentally studied the operation of metallized film capacitors in high current overload mode. We have detected changes in the frequency dependencies of capacitance and dissipation factor were found. It was found that effective capacitance rapidly decreases in the high frequency region (more than 1 kHz). Moreover, an increase in the dissipation factor increasing and the appearance of maxima in the frequency dependence were found. The degradation of contact edges was numerically modelled. The results of numerical modeling showed that the changes in the frequency dependencies of capacitance and dissipation factor is due to the degradation of contact edges and the subsequent non-uniform distribution of electric potential in capacitor electrodes. Based on the experimental and calculated data, we have suggested an equivalent circuit of a metallized film capacitor. This circuit takes into account the degradation of electrodes during operation in overload mode.