Effect of Relative Slot-Opening Shift on Cogging Torque and Performance of an Axial Flux Permanent Magnet Machine

Abstract

Cogging torque in permanent magnet machines is a source of acoustic noise, vibrations and one of the reasons behind output torque ripple. Its reduction is of prime importance in automotive and positioning applications. Several techniques are available in the literature for cogging torque reduction in both radial and axial flux machines. This paper presents the effect of relative displacement of consecutive slot-openings on cogging torque of an axial flux permanent magnet machine. In addition, its influence on several performance parameters such as stator flux linkage, no-load induced emf, emf harmonics and rated electromagnetic torque of the machine is also analysed and compared. A 3-D finite element model of the machine is simulated to obtain various analysis results. A maximum reduction of 51.67% in cogging torque is obtained for 0 or 1 displacement factor. However, the rms-induced emf and average torque showed deterioration by 4.05% and 5.8%, respectively.