The sinusoidal air-gap magnetic field design of axial flux permanent magnet synchronous motors

The axial flux permanent magnet synchronous motors have features of short axial length, high energy density and great torque. They have found applications in computer peripherals, electric vehicles in-wheel drive and flywheel energy storage devices. The paper research analytically three methods for forming sinusoidal air-gap magnetic field, and put forward that the method with magnets of uniform magnetization, equal thickness and unequal width is the optimum choice. In the numerical analysis of air-gap magnetic field, the authors propose making magnets of equal thickness and unequal width equivalent to that of unequal thickness and equal width, and taking section at average radius as computation plane. The results of finite element analysis with ANSYS software validate the analytical design.

I. Introduction

The axial flux permanent magnet synchronous motors have features of short axial length, high energy density and great torque, it is suitable for cases that the installation space is special (the axial space is limited) and high torque is required. The axial flux permanent magnet synchronous motors have been applied to computer peripherals, electric vehicles in-wheel drive, flywheel energy storage devices ^[1]–[4] and so on. In these applications, operation smoothness is important, so the air-gap magnetic field of axial flux permanent magnet motors should be designed sinusoidally.