Harmonic and Non-linear Effects on the Parameters and Performance of a Vernier Machine with Flux Concentrating Spoke Rotor

This paper presents a systematic study on the MAGNUS machine, which is an innovative dual-stator axial flux permanent magnet vernier machine (AFPMVM). The MAGNUS machine features a novel single-wound dual-stator design with minimal slots and an exceptionally high-polarity spoke-type permanent magnet rotor, which enables a very high flux concentration ratio. The operating principle of vernier machines is derived, showing the possible slot-pole combinations. Inductance components are introduced, and multiple methods are employed to determine the direct and quadrature axis inductances, revealing that despite its spoke-type rotor, due to a high harmonic content and a high differential leakage inductance, the MAGNUS machine has no saliency. Additionally, the effects of non-linearity due to open circuit field of permanent magnets is shown. Further analysis demonstrates the enhanced power factor enabled by the unique topology of the MAGNUS machine and using a passive stator. Experimental tests conducted on a prototype, which serves as a laboratory concept demonstrator, validate the computational model and the analysis results throughout this paper.