Temperature Dependence of Self-Healing in BOPP Metallized Film Capacitors under Rising Voltage

Self-healing (SH) plays as a unique property to benefit biaxially oriented polypropylene (BOPP) metallized film capacitors (MFCs) for high operation reliability in applications needing high volumetric energy property. However, massive heat could be accumulated inside BOPP MFCs upon long-term operation owing to the poor thermal conductivity of BOPP. The resulting temperature rise inside MFCs could bring seriously orientation to SHs considering the SHs a temperature-dependent progress. This study employs a mesoscopic and microscopic view to elucidate the temperature dependence of SHs with multiple Weibull subpopulation distributions aided by the examination of the morphology of demetallized area on BOPP layer after SH. As the couple of evidence, the variation of free volume and mean-square-displacement (MSD) of polypropylene (PP) with temperature are evaluated to illustrate the mechanism of temperature-dependent properties of SH. The findings reveal that moderate temperature increases can enhance SH inception voltage (SHIV), but excessively high temperatures have a detrimental effect. Furthermore, expected capacitor voltage (ECV) decreases with rising temperatures. The study also observes that both SHIV and ECV increase and then decrease with the voltage ramp rate, peaking at 300 V/s within the range of 50-900 V/s.