Performance Comparison of Two Modular Permanent Magnet Machines With E-Core Stators for eVTOL Hovering Propulsion System

This paper proposes and investigates two novel phase-unit modular (PUM) permanent magnet machines with E-core stators (ECS) for electric vertical takeoff and landing (eVTOL) aircraft propulsion. First, the propulsion requirements of eVTOL aircraft are identified, and two representative ECS topologies are introduced, with detailed analyses of operating principles, slot-pole combinations, and winding configurations. Subsequently, the analytical models of the proposed two PUM machines are developed, e.g., armature magnetomotive force (MMF), inductance, back electromotive force (EMF), and torque characteristic. Based on these models, the two machines are designed and optimized, with emphasis on the effects of stator module number, magnet configuration, and geometric parameters. For overall performance benchmarking and validation, a series of conventional machine models are also established for comparison, which can demonstrate the pros and cons of two PUM machines. Eventually, two prototypes of PUM machines are fabricated and experimentally tested, and the results exhibit a good agreement with previous analytical predictions and finite element analysis (FEA). This paper aims to evaluate a series of modular machine topologies as a promising alternative for eVTOL propulsion systems.