Cryogenically-Cooled Power Electronics for Long-Distance Aircraft

Abstract

New aerodynamic aircraft concepts enable the storage of volumetric liquid hydrogen (LH2). Additionally, the low temperatures of LH2 allow technologies such as the superconductivity of electrical components. An increased power density of the onboard wiring harness and the electrical machine can be expected. Nevertheless, the power electronic drive inverter has to deliver high power and high switching frequencies ( f {PWM}s ) under challenging conditions. Therefore, knowledge of the electric behaviour of different semiconductor materials under cryogenic temperatures is essential to answer the question: 'Are modern power electronics a technology enabler or a system bottleneck?' This publication shows a comprehensive novelty study for cryogenic power electronics based on experimental-driven semiconductor investigations, mission profile-based considerations, requirement analyses of superconducting electrical machines, and studies of the cooling concepts. All aspects are discussed within one interdisciplinary publication. A cryogenic system cannot be considered without a feasible cooling concept. Different semiconductor structures based on various materials (silicon (Si), silicon carbide (SiC) and gallium nitride (GaN)) are evaluated for their suitability. The collected data and the literature review draw a technology feasibility studies supported by detailed cooling system analyses and superconducting electrical machine requirements. The power demand and high f {PWM} lead to a SiC non-cryogenic inverter approach. Due to the detailed cooling system assessment, a loss reduction is achieved by optimising the junction temperature ( T {J} ) under various load cases (LCs) out of the mission profile.