Optimal design of a three-phase 540V/70kVA SiC inverter for aircraft applications

Abstract

This paper presents the design procedure to minimize loss and weight of a three-phase 540V/70kVA SiC inverter used to drive a 50kW motor for modern aircraft applications. This design procedure is validated by experimental results. Different SiC power modules are evaluated concerning conduction and switching losses. Efficiency and power density are evaluated for different switching frequencies and PWM (Pulse Width Modulation) techniques, which have a significant impact on the size of DC bus capacitors and cooling system. Precise calculation of losses in the SiC power module is done using the datasheet data as well as data from precise characterization of SiC module. The optimization process to determine the minimum weight of DC bus capacitors and forced air aluminum fin heat sinks is presented in detail. Experimental results on a first assembled converter show small deviations from the estimated losses. However, the total weight of this first version significantly exceeds the calculated one, which leaves a significant path for improvement for the final version of the inverter.