Effect of additional harmonics of driving current on torque ripple and unbalanced magnetic force of the BLDC motors with stator and rotor eccentricities

Abstract

This paper investigates the characteristics of the torque ripple and UMF in the BLDC motor with stator and rotor eccentricities due to additional harmonics of the driving current. Torque ripple can be divided into cogging torque due to the interaction between poles and slots, and commutation torque ripple due to driving current. Additional harmonics of driving current affect the characteristics of torque ripple. UMF is not generated in rotational symmetric motors with respect to pole, slot and winding configurations. However, stator and rotor eccentricities of BLDC motors generate additional harmonics on cogging torque and UMF. This research theoretically and numerically investigates the effects of driving current on the torque ripple and UMF of a BLDC motor with rotor and stator eccentricities. It shows that additional harmonics of the driving current, the stator eccentricity, and the rotor eccentricity independently affect the torque ripple. It also shows that additional harmonics of the driving current generate additional harmonics in UMF if BLDC motors have the stator or rotor eccentricities.