Computer-Aided Design of a Brushless DC Motor with Exterior-Rotor Configuration

AbstractThe aim of this paper is to evaluate the magnetic field and motor performance of an exterior-rotor brushless DC (BLDC) motor based on two approaches, i.e., the magnetic circuit method and the finite-element analysis (FEA). An equivalent magnetic circuit model is applied to analytically estimate the magnetic field of a BLDC motor, while the validity is verified by the two-dimensional FEA. Due to the restriction of the simplified mathematical model, the FEA is further employed to be an assistant tool for the detailed design of the pole shoe of this BLDC motor. Four design cases with different pole shoe dimensions are proposed, and the one that possesses the largest electromagnetic torque as well as the smallest cogging torque and torque ripple is further prototyped for electric bicycle applications.