Optimization of Electric-Field Grading Plates in a PCB-Integrated Bus Bar for a High-Density 10 kV SiC MOSFET Power Module

A finite element method (FEM) driven, automated numerical optimization technique is used to design field grading structures in a PCB-integrated bus bar for a 10 kV wirebondless silicon-carbide (SiC) MOSFET power module. Due to the ultra-high-density of the power module, and close proximity of the high-voltage power terminals, PCB embedded field grading structures are used to manipulate the high intensity electric field and reduce field crowding. Two PCBs are designed and built, one using a conventional, manual design approach, where design parameters are swept individually and the impact is assessed graphically, and one with the proposed optimization technique. The PCB developed with the proposed technique achieved a 30% higher partial discharge inception voltage (PDIV) and reduced the design cycle time from a few weeks to a few days. The problem formulation and cost function are scalable to allow for wide applicability in the design of other high-voltage, high-density systems.