Reducing the Cogging Torque of BLDC Motors with the Proposed Firefly Optimization Algorithm

The mechanical vibration of BLDC Motors during the rotation of the rotor due to torque ripple and radial forces, makes them difficult to use. Thus, in this paper, the factors affecting this problem, such as the combination of the number of poles and slots, shape of the magnet and magnetization method, slot opening in the stator laminations, geometric symmetry of the rotor and air-gap are analyzed for three different structures (integer-slot with symmetric air-gap, fractional-slot with symmetric air-gap and fractional-slot with asymmetric air-gap) of BLDC Motors using finite- element (FE) analysis. Based on the analysis results, the fractional-slot motor with symmetric winding is chosen as a suitable structure with minimum mechanical vibration level. Finally, in order to reduce the cogging torque, the Proposed Firefly Algorithm is used to optimize the pole arc and slot opening.