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

Ali Mohammadi, University of Kentucky
Yaser Chulaee, University of Kentucky
Aaron M. Cramer, University of Kentucky
Ion G. Boldea, Universitatea Politehnica Timisoaraand Romanian Academy, Romania
Dan M. Ionel, University of Kentucky

Abstract

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.