Design and Qualification of a 100-kW Three-Phase SiC-Based Generator Rectifier Unit Rated for 50 000-Ft Altitude

Featuring higher blocking voltage, smaller parasitic elements, faster switching speed, and a more compact package, wide-bandgap semiconductor devices like Silicon Carbide devices (SiC), can enable compact aircraft generator-rectifier units (GRUs) thus making them highly desirable. Yet, the combination of the increased voltages, high power density, and the lower pressure environment associated with aircrafts can pose a significant threat to the converter operation due to the increased sensitivity to electric field (E-field) intensity inside the GRU components and their assembly. To this end, a comprehensive design and qualification of a 100 kW three-phase SiC-based GRU rated for a flight altitude of 50,000 ft (11.6 kPa) is presented in this paper. First, an insulation coordination that based on Paschen-curve is proposed to improve the power density. High E-field areas of the GRU are determined and preemptively solved with the use of an E-field control methodology to prevent partial discharge (PD) under normal operating conditions. Second, the gate-driver and EMI filter components are optimized for operation at 70 kHz. Lastly, the insulation design is qualified through low-pressure PD tests, and it is verified that the unit successfully operates at rated conditions to achieve 33.3 kW/l power density, 99.2 % efficiency, and PD-free operation at 50,000 ft.