Optimization of the PM array of brushless DC motor for minimum cogging torque

This paper deals with magnetic field calculations and model-based prediction of electromagnetic torque pulsations in a brushless DC (BLDC) motor. The impact of a multipolar excitation of permanent magnets is analyzed. It is shown that the cogging torque in the motor with the multipolar excitation of permanent magnets is reduced six times as compared with the conventional BLDC motor. For the computation of an optimal magnetic circuit shape a 3D finite element program was used and an evolutionary algorithm was implemented. In the evolutionary algorithm used for optimization, two parameters were taken into account.