Analytical Modeling of Static Eccentricities in Axial Flux Permanent-Magnet Machines with Concentrated Windings

Yunkai Huang,Ahmed Hemeida,Baocheng Guo,Peter Sergeant

doi:10.3390/en9110892

Abstract

The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the axial and circumferential magnetic flux densities are obtained using a coupled solution of Maxwell’s equations and Schwarz-Christoffel (SC) mapping. The magnetic flux densities under SE conditions are calculated afterwards using a novel bilinear mapping. Some important electromagnetic parameters, e.g., back electromotive force (EMF), cogging torque and electromagnetic (EM) torque, are calculated for both SE and healthy conditions, and compared with the finite element (FE) model. As for the double rotor AFPM, SE does not contribute much effect on the back EMF and EM torque, while the cogging torque is increased. At each calculated section, FE models were built to validate the analytical model. The results show that the analytical predictions agree well with the FE results. Finally, the results of analytical model are verified via experimental results.

Highlights

Axial flux permanent magnet machines (AFPMMs) have a number of distinct advantages over radial flux permanent magnet machines (RFPMMs)
Because of the disc shaped rotor and stator structure, an AFPM is smaller in size than its RFPMMs counterparts
Back-EMFand andtorque, torque, will presented and compared. Since these characteristics under different static eccentricity (SE) conditions only differ in presented andcompared. Since these these characteristics characteristics under different conditions only differ in in presented and under different conditions only differ magnitude, the 40% eccentricity is chosen to carry out the analysis

Summary

Introduction

Axial flux permanent magnet machines (AFPMMs) have a number of distinct advantages over radial flux permanent magnet machines (RFPMMs). Because of the disc shaped rotor and stator structure, an AFPM is smaller in size than its RFPMMs counterparts. This particular structural characteristic makes it easy to address the space limitation in some applications such as electric vehicles (EV) [2], hybrid electric vehicles (HEV) [3], wind turbos [4] and flywheel storage systems [5], etc. Due to the smaller contact surface between the rotor and the shaft, it is more difficult to design a rotor-shaft mechanical joint with a high mechanical integrity [6], which makes AFPMMs more susceptible to imperfect assembly issues such as static eccentricities (SEs), dynamic angular misalignment [7] and static/dynamic eccentricity misalignment [8]. The rotor is inclined and the air gap is asymmetric.

Objectives

Results

Conclusion