Torque Ripple Reduction of an Axial-Flux Permanent Magnet Motor with Distributed Winding

This study investigated the reduction in torque ripple of an axial-flux permanent magnet synchronous machine (AFPMSM). To reduce the cogging torque, permanent magnets with a sinusoidal boundary shape were used. To reduce the harmonic torque, distributed winding with different fill numbers in the stator slots was used. This AFPMSM is intended to apply a small servo-motor with precise angular positioning. It has a single-stator/single-rotor structure with 8-pole/36-slot combination. The outer diameters of the stator and rotor cores are both 60 mm. The rated torque with a current density of 6 A/mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is 0.2 Nm. The winding ratio was theoretically and numerically investigated to reduce the harmonic torque. A prototype machine was fabricated and tested, and the measured torque ripple, the ratio of peak-to-peak value divided by the average, was approximately 1%.