Magnet Segmentation for Commutation Torque Ripple Reduction in a Brushless DC Motor Drive

We present a new brushless DC motor (BDCM) design based on a model elaborated from a finite-element method associated to controller circuit equations represented in a Matlab-Simulink environment. The simulation model takes into account the commutation period effect and is based on the true system design implementation. The simulation results show that there is an effect between this commutation (a major source of torque ripple) and appropriate permanent-magnet segmentation design, particularly when the angle of advance between the back-electromotive force (EMF) and the current is adequately set. Current control strategies are found limited and may require complex implementation. Concentration on back-EMF and ultimately on permanent-magnet design are interesting aspects of torque ripple as well as rotor losses over wide speed range. After validation of the simulation model using an experimental kit set for the purpose, we perform an optimization procedure based on an indirect coupled field circuit approach that has led to an optimal design for which the torque ripple is minimal (less than 6%). An analytical design provided support for the study. The new design shows a lower cogging torque. Overall, the new design helps to provide a low-cost BDCM system for many applications using a simple square wave circuit controller.