Medium-Voltage SiC-Based Converter Laminated Bus Insulation Design and Assessment

Laminated bus has been widely used in power converters for decades. Thicker insulation increases parasitic inductance, weight, and size of the bus and decreases cooling performance and power density. Thus, it is desired to have thinner insulation for achieving the desired lifetime. The emerging medium-voltage (MV) SiC-based converters require fast switching transients and high power density, which make the optimal laminated bus design challenging. Since the internal partial discharges (PDs) can significantly degrade insulation, they should be eliminated in the design stage to ensure optimal performance. However, insulation overdesign does not necessarily help remove PD from internal defects and air pockets in the laminated bus. In order to obtain a PD-free laminated bus with thin insulation, this article uses representative structures to show a path for removing internal PDs. This paper presents a systematic approach to remove air pockets and reduce the impact of the unavoidable defects in adhesive layers through theoretical and experimental studies. In addition, a proper material selection and processing method are derived to reduce the size and number of internal defects while leading to a more favorable electric field distribution. The PD experimental results suggest the effectiveness of the proposed approach.