title: Design improvement and experimental verification of the Axially Stacked three-phase Flux Reversal Machine for Electric Vehicles
title: Entwurfverbesserung und experimentelle Verifizierung der axial gestapelten dreiphasigen Flux Reversal Machine für Elektrofahrzeuge
Creators: name: Ryu, Jaeho
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2025

description: This work aims to introduce an electrical machine with high torque density and low torque ripple. Unlike conventional electrical motors such as the Permanent Magnet Synchronous Motor (PMSM) and Switched Reluctance Motor (SRM), this work adopts the Flux Reversal Machine (FRM) as the basic electrical motor. The FRM operates on the principle of flux reversal within its basic structure. Specifically, the placement of Permanent Magnets (PMs) on the tips of the stator’s teeth generates high torque density. However, the inherent design of the FRM, with its alternating flux direction, can contribute to torque ripple. This undesirable feature can lead to detrimental effects such as vibration, noise, and a reduced lifespan of the machine. To mitigate these harmful effects, this thesis proposes a stacked type design and perform design optimization accordingly. Each layer in the stacked type consists of a stator and a rotor with excited current. In this thesis, each layer operates with a single-phase current, resulting in a machine with three stacked layers forming a three-phase system. By stacking the single-phase FRMs, the pulsation of torque in the machine can be reduced. This motor is named the Axially Flux Stacked Flux Reversal Machine (ASFRM). Since stacked type machines have rarely been studied, this thesis analyzes the ASFRM using the airgap magnetic flux density analytic method based on Fourier Series and the Finite Element Method (FEM). After investigating ASFRM numerically and analytically, design optimization is executed using a Multi-Objective Genetic Algorithm (MOGA). Noteworthy in this optimization process is that it is accomplished through both electromagnetic and thermal analysis. The thermal analysis is critical because high temperatures in the machine can lead to demagnetization of the PMs and damage the coil insulation during the electrical motor operation. Consequently, it potentially causes serious adverse effects on the entire motor. The FEMM used in this paper as an FEM software is capable of both electromagnetic and thermal analysis, but it does not have a built-in coupling function between the two. Therefore, in this thesis, the coupling between the data from the two analyses is achieved manually using MATLAB. Through this process, an optimized ASFRM design can be derived, ensuring the stability of the design from a thermal perspective. Finally, the manufactured ASFRM is introduced and appropriate experiments are performed. In order to manufacture a motor suitable for the Institute's safety standards, a process for reducing the size of the proposed motor is developed and its justification is proven. As part of the motor experiment, a no-load test and a load test are conducted, and the validity of the experimental results is confirmed through comparison with the FEM and equivalent circuit model for the ASFRM. The feasibility of the proposed ASFRM is proven through all these experiments, and suggestions for further research needed in the future are also provided in this thesis.