Planar Common-Mode EMI Filter Design and Optimization in a 100-kW SiC-based Generator-Rectifier System for High-Altitude Operation

Silicon-Carbide (SiC) devices are receiving popularity for high-power converter systems in aircrafts due to many advantages over silicon counterparts. However, the electro-magnetic interference (EMI) problems are more serious with the SiC devices operating at higher switching speed and higher switching frequency. The common-mode (CM) EMI filter design of the high-power SiC converter is especially challenging for high-altitude application due to the harsher requirements of insulation and heat dissipation. The optimization of the CM EMI filter design in a 100-kW SiC generator-rectifier system operating at 50,000 ft is conducted in this paper to obtain the highest power density of the EMI filter and the rectifier system. A PCB-based planar CM choke is designed with the consideration of partial discharge (PD) and heat dissipation at the altitude of 50,000 ft. The structure of the CM choke is optimized with embedded electric-field shielding plates, which controls E-field stress in air below 300 V/mm by considering the Paschen's effect. The large surface area of PCB windings improves the efficiency of heat dissipation at high altitudes and reduce the profile of the CM choke. A Pareto optimization is conducted to minimize the size of the choke and the volume of the final design is only 155 cm(3). The experimental results show that the CM noise is reduced effectively with the CM EMI filter. PD is not observed even at the altitude of 50,000 ft and the thermal performance is excellent with a current of 190 A.