Design and Analysis of Axial-Flux Modular Spoke-Type Permanent Magnet Machines With Segmented Stators for Traction Applications

As one of the most competitive axial-flux permanent magnet machine (AFPMM) topologies, the dual-rotor modular-stator construction of the yokeless and segmented armature (YASA) features extreme compactness and significant power and torque densities. The conventional surface-mounted PM (SPM) rotor used in YASA machines makes it challenging to satisfy the requirements of various scenarios. This paper proposes a novel AFPMM with the modular spoke-type PM (AFMSTPM) rotor combined with the segmented stator structure. The air-gap flux density is calculated by the analytical model based on the simple magnetic equivalent circuit and the relative air-gap permeance mapping methods. The influences of critical design parameters on the no-load and load conditions of the AFMSTPM are studied using the 3-D finite-element method. By comparing the AFMSTPM machine with the YASA-SPM machine, the advantages of the proposed machine with respect to PM eddy-current loss, PM irreversible demagnetization, and constant power speed range are revealed. A prototype machine was manufactured and tested to validate the predictions of the analytical and FEM results.