Abstract Metalized film capacitors are widely used in many power electronics fields due to their high stability, large capacity, and good self-healing properties. Studying the self-healing micro mechanism of metalized film under complex stress can help optimize the manufacturing process of metalized film capacitors, improve product lifespan, and stability. This article constructs a self-healing characteristic test platform for metalized film under multiple physical fields, conducts self-healing experiments under different electro-thermal environments, characterizes the self-healing area and morphology, In the experiments, a Nanyang MDP5.8 micrometer-thick polypropylene metalized film with an aluminum metal layer was used. The applied voltages on the samples were 1.8 kV, 2.3 kV, 2.8 kV, 3.3 kV, and 3.8 kV. The temperatures were set at 30, 40, 50, 60, and 70°C, and the pressures were 1.8 MPa, 2.3 MPa, 8 MPa, 11 MPa, and 15 MPa. The self-healed samples were observed for morphology using an SOPTOP-SZN71 optical microscope.This article uses COMSOL MULTIPHYSICS 6.2 to build a self-healing model under multiple physical fields to explore the micro and macro characteristics of self-healing in metalized film. The article first used a bipolar carrier transport model to simulate the phenomenon of charge concentration in weak spots under continuous voltage stress during capacitor operation, calculating the distribution of charges within the material at different times. As charges accumulate, the equivalent current in the weak spot region gradually increases. Once it reaches a certain value, impurities within the metalized film first break down, leading to filamentary discharge within the region. At this point, the discharge channel transitions from solid-state to gaseous, and the simulation model shifts from a solid intrinsic carrier transport model to a gas discharge model. This model is constructed using the plasma model in COMSOL to investigate the effects of different electro-thermal environments on the formation and development of discharge channels. Finally, the electromagnetic coupled thermal module is used to simulate the effects of Joule heating on vaporization and ionization of the metal layer, as well as carbonization of the dielectric layer during the self-healing process of the metalized film under various electro-thermal environments. The model's accuracy is validated by comparing it with previous experimental results. From the experimental and simulation results, the following conclusions can be drawn: (1) The formation time of the discharge channel is on the order of nanoseconds, and its development is similar to electron avalanche. The time required for the discharge channel to fully penetrate is inversely proportional to the voltage and temperature, and directly proportional to the pressure. (2) During the self-healing process, the temperature of the metal layer can exceed 5 600 K. The ionized region of the metal layer is positively correlated with voltage and temperature, and negatively correlated with pressure. However, the proportion of the ionized region to the self-healing area remains around 43% under different electro-thermal environments. (3) The carbonization of the dielectric layer is minimal during the self-healing process. The carbonized region of the dielectric layer is slightly larger than the self-healing area of the metal layer, but the carbonization depth is only about 0.4 micrometers, roughly 7% of the film thickness. The radius and depth of carbonization are directly proportional to the applied voltage level and temperature, and inversely proportional to the pressure. However, the ratio between the carbonization radius and the self-healing radius remains around 1.6 under different electro-thermal environments.
Wang Ze,Liu Jingzhou,Wang Wei等. Numerical Simulation of Self-Healing in Metallized Films under Electro-Thermo-Mechanical Coupling[J]. Transactions of China Electrotechnical Society, 2024, 39(zk1): 127-140.
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2024, Vol. 39 
