Self-Healing Probability in Metallized Film Capacitors: Device-Level Comparison of Polypropylene and Polyethylene Terephthalate Dielectrics

Self-healing (SH) is a critical feature of metallized film capacitors (MFCs), since it ensures MFCs’ operational stability under extreme conditions. While SH depends not only on applied voltage and environmental factors but also strongly on the dielectric material. Despite this, current research on SH behaviors primarily examines metallized dielectric films rather than complete MFC devices, there remains a lack of systematic device-level comparative analyses for different dielectrics. Therefore, this paper investigates the SH probability of polypropylene (PP) and polyethylene terephthalate (PET) MFCs at the device level under varying voltage ramp rates. Results reveal that PET exhibits higher SH propensity, with SH probability exceeding 90% across all rates—nearly twice that of PP. SH process becomes less severe with rising ramp rates for both materials, but PET remains higher SH severity: it more readily triggers related-SH (RSH) events with peak energies up to 1080.44 mJ (vs. PP’s 769.92 mJ), causing greater damage and inferior voltage withstand level. Density functional theory (DFT) analysis explains these disparities by identifying differences in polarization and conductivity between them. PET demonstrates a higher molecular polarity index (MPI), along with broader electrostatic potentials and narrower orbital energy gaps. These attributes facilitate charge accumulation and enhance the severity of SH events in PET relative to non-polar PP.