Sensitivity Comparison of Open-Circuit Airgap Flux Between Surface-Mounted Permanent Magnet and Spoke-Type Permanent Magnet Machines Considering Manufacturing Tolerances

Cha-Seung Jun,Byung-Il Kwon,Ohbong Kwon

doi:10.1109/access.2019.2953224

Abstract

The study compares the sensitivities of open-circuit airgap flux (OCAF) between a surface-mounted permanent magnet (SPM) machine and a spoke-type PM machine based on variations in airgap length including additional airgaps between permanent magnets and rotor core and between segmented stator cores to achieve high quality electric machines. Analytical equations deduced from magnetic equivalent circuits (MECs) are used to directly compare natural-born characteristics of the OCAF of the two machines. First, the MEC of each machine is modeled by considering two additional airgaps between the PMs and rotor core and between the segmented stator cores. Second, the OCAF equation of each machine is derived from the MEC to analyze the effects of the design variables on the OCAF. Subsequently, the partial derivative equation of the OCAF equation with respect to the airgap length is obtained for sensitivity analysis. A comparison of the equations of the two machines indicates that the spoke-type PM machine exhibits inherently higher sensitivity and average value of the OCAF when compared to that of the SPM machine. Finally, the results are validated via a two-dimensional finite element method (FEM) by considering the variations in airgap lengths.

Highlights

High efficiency of electric machines corresponds to the most important performance metric to satisfy increased energy regulations and standards in all application fields
Flux-concentrating structures, such as spoke-type permanent magnet (PM) machines or V-shaped PM machines, are continuously developed [6]–[12] because they can provide higher open-circuit airgap flux (OCAF) when compared to the conventional PM machines
surfacemounted permanent magnet (SPM) machines are widely used for many applications with the exception of high-speed applications that normally adopt SPM machine [13]–[16]

Summary

INTRODUCTION

High efficiency of electric machines corresponds to the most important performance metric to satisfy increased energy regulations and standards in all application fields. Only a few studies compare tolerance sensitivities of the OCAF between different types of machines such as spoke-type PM machines and SPM machines. The study compares tolerance sensitivities and magnitudes of the OCAF between SPM and spoke-type PM machines with manufacturing tolerances to compare their relatively inherent tolerance sensitivity and the magnitude of the OCAF and to analytically investigate the effect of design variables such as airgap length, PM thickness, and PM width. The partial differential OCAF equation with respect to the variation in design variables of each machine is deduced from the OCAF equation for the sensitivity analysis. Tolerance sensitivities of the two machines are directly compared using the equations to verify inherently different OCAF characteristics with an example study. The analysis results are validated by an example study performed via a two-dimensional (2D) finite element method (FEM) and Monte-Carlo simulation (MCS) to visualize distributions of the OCAFs with variations in design variables

SENSITIVITY ANALYSIS USING MEC EQUATIONS

Findings

CONCLUSION