New Stator Tooth for Reducing Torque Ripple in Outer Rotor Permanent Magnet Machine

Abstract

Torque ripple has been a major problem for the permanent magnet (PM) machine. It is discussed focusing on the magnetic circuit of the PM machine. Since it is known the relationship between the torque ripple and the magnetic energy that is stored in the magnetic field along the air gap of the PM machine, fluctuation in the magnetic energy was initially revealed. New tooth geometry was obtained by drilling holes into stator tooth to modify this variation in the magnetic energy and the fluctuation in torque. Thus, a new stator tooth design in outer rotor surface-mounted permanent magnet (OR-SPM) machine was proposed to minimizing the torque ripple in this study. Improvement in torque ripple value was performed in excess of 50% thanks to new stator tooth design. In addition, improvements have been carried out at the average torque and total harmonic distortions (THD) of back EMF (electromotive force).