Electric-Field-Dominated Partial Discharge in Medium Voltage SiC Power Module Packaging: Model, Mechanism, Reshaping, and Assessment

Benefiting from the high breakdown voltage of the silicon carbide (SiC) material, the medium voltage SiC power module has made an unprecedented breakthrough, which is regarded as a promising route for the high voltage converter. However, partial discharge (PD) challenges the reliability and safety of the medium voltage SiC power module, which limits its massive applications in industrial fields. In this article, insightful models are proposed to reveal the mechanism of the electric-field-dominated PD in the medium voltage power module. Furthermore, it is found that the distorted electric field at the triple point of the power packaging is caused by the edge effect. Besides, the low-cost equipotential ring concept and structure are proposed to dramatically decrease the distorted electric field at the triple point. Additionally, the experiment platform with ultra-low interferences is presented to assess and localize the PD. With the aid of the proposed test bench, the PD principles in conditions of different ceramic thicknesses, electrode distances, and copper lengths of the copper plates of the DBC are measured. Comparative experiments ensure the feasibility and effectiveness of the proposed equipotential ring structure, which can significantly decrease the PD issue and promote the isolation level of the medium voltage SiC power module.