Torque characteristics of a BLDC motor with multipolar excitation

Purpose - This paper deals with magnetic field calculations and model-based prediction of electromagnetic torque pulsations in a brushless DC (BLDC) motor.Design methodology approach - The impact of a Halbach-like magnetization and a multipolar excitation of permanent magnets are analysed. The measurement results from the prototype motors are well-compared with those obtained from the model calculations. 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.Findings - The proposed method provides high accuracy of the analysis of coupled electromagnetic phenomena. The comparison between measured and calculated values of electromagnetic torque, cogging torque and EMF shows a very good agreement.Practical implications - Reduction of the machine cogging torque is essential for practical applications of DC motors, in particular in the robotics industry.Originality value - This paper shows that multipolar excitation contributes to essential reduction of the cogging torque in a BLDC motor. This is confirmed by high-quality numerical models of the motor, positively verified in experiments with motor prototypes.