Evaluation of a Phase-Unit Axial-Modular Permanent Magnet Vernier Machine With U-Core Stators for eVTOL Distributed Electric Propulsion

This article proposes a novel phase-unit axial-modular permanent magnet Vernier machine with multiple U-core stators (PUAM-PMVM-UCS) for distributed electric propulsion (DEP) in electric vertical takeoff and landing (eVTOL) aircraft. The machine topology and operating principle are first introduced, followed by a detailed analysis of key design parameters such as slot-pole combinations and winding configurations. Based on the DEP system requirements, the proposed PUAM-UCS machine is designed and optimized with respect to critical parameters such as the module number and dimensions of UCS. Following, the theoretical models are developed to highlight the distinctions between the PUAM-UCS machines and conventional machines. A comprehensive performance evaluation, e.g., no-load back EMF, output torque, power factor, losses, and efficiency, is carried out by both analytical approaches and finite-element analysis (FEA). Finally, two prototypes of PUAM-UCS and PUAM machine with split-pole stators (PUAM-SPSs) are fabricated and experimentally tested, demonstrating strong agreement with theoretical and FEA predictions. The results can confirm that this proposed machine can achieve improved torque density and better fault tolerance, making it a promising future candidate for the eVTOL DEP system.