System Weight Comparison of Electric Machine Topologies for Electric Aircraft Propulsion

TLDR

Aircraft electrification research prioritizes propulsion electrification, demanding high specific power, power density, and efficiency to surpass conventional systems. This study compares electric machine topologies for aircraft propulsion, evaluating tradeoffs among power electronics, fault response equipment, and gearbox components. The authors model five machine topologies—PMSM, BLDC, SRM, BDFRM, and IM—using a parametric FEM design tool, scale them with analytical sizing equations, and predict component weights for gearbox, power electronics, circuit breaker, clutch, thermal management, and energy storage. Results show that PMSMs retain a weight advantage over other topologies even after accounting for additional drive and fault response components.

Abstract

An important thrust in current aerospace research is aircraft electrification, including propulsion system electrification. For an electrified propulsion system to provide net benefit over conventional propulsion, high specific power, power density, and efficiency requirements of the electrical system must be met. This paper expands on previous work by comparing electric machine topologies for electric aircraft propulsors while considering tradeoffs in the power electronics, fault response equipment, and gearbox components. Permanent magnet synchronous machine (PMSM), brushless DC machine (BLDC), switched reluctance machine (SRM), brushless doubly-fed reluctance machine (BDFRM), and induction machine (IM) topologies are explored. A parametric design tool including finite element analysis is used to create a viable design for each machine type. Next, analytical sizing equations are used to scale the designed machines to varying operating speeds and aspect ratios. In addition, gearbox, power electronics, circuit breaker, clutch, thermal management system, and energy storage weights are predicted based on current power densities of research designs. It is well established that PMSMs have outstanding power density and this study shows that when considering additional drive and fault response components, PMSMs still maintain the weight advantage.