Design and Implementation of SiC-Based 200-kW High-Density High-Speed High-Altitude Electric Propulsion AC Drive System

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Abstract
In this paper, a 200-kW SiC-based high-speed motor drive system for electric aircraft propulsion is investigated. The focus is on maximizing power density while conforming to stringent aerospace electromagnetic interference (EMI) standards, fitting the special load characteristics of high-speed propeller, addressing the challenges posed by low air pressure conditions, and mitigating motor bearing current. To achieve this goal, a comprehensive set of weight models and design tools is developed, considering the impact of voltage, switching frequency, and topologies on system density. To mitigate EMI noise and bearing current issues, a three-level (3-L) T-Type inverter is employed, and a 200-kW (300 Arms ac torque current) prototype is designed. A seamless integration of short-circuit protection, gate driver, commutation loop and sensors is proposed while ensuring insulation integrity and optimal heat transfer capability, even in challenging conditions of altitudes up to 25,000 ft. Furthermore, the challenge posed by breakaway torque of propeller on low-speed operation is solved by introducing a novel loss-balance modulation for the 3-L T-Type inverter to reduce the weight and cost of power devices. The hardware achieves a thermally verified power density of 19.7 kW/kg, meeting DO-160 EMI emission and motor bearing current requirements, making it suitable for operation at 25,000 ft altitude.

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