A novel technique of cogging torque reduction in mass-produced surface-mounted permanent magnet motor using tooth notching pairing

Surface-mounted permanent magnet (SPM) motors have been increasingly favored due to smaller volume, higher power density, higher efficiency, and higher positioning accuracy, widely applied in many applications such as textile machinery, robot, and packaging machinery. The interaction between permanent magnet (PM) and the slotted iron produces the cogging torque. For SPM motor with high-performance sintered Nd-Fe-B, cogging torque is more serious, which causes torque ripple, vibration, and noise of PM motor. For PM motor design, one of the most significant tasks is to make the cogging torque as small as possible. Up to now, there have been a few researches about the conventional tooth notching only involved in its shape and number, which are uniform both in the axial and circumferential directions. Due to this structural characteristic, the effect of the conventional notching on reducing the cogging torque is not very effective. In addition, we are not able to find any study in the literatures which were related to notching position and the nonuniform structure. The purpose of this paper is to present a practical method to reduce cogging torque and minimize torque ripple using tooth notching pairing. The results illustrate that the cogging torque is reduced greatly and the torque ripple is suppressed effectively with this method.