Study of the impact of asymmetrical stator pole arc on the cogging torque for single phase Permanent Magnet BLDC Motor

摘要

This paper presents an investigative study on the effect of an asymmetrical stator pole arc length and its relationship with the rotor pole width in single phase Permanent Magnet Brushless DC (PM BLDC) Motors. Employing an asymmetrical stator pole design influences the shape of the trapezoidal back EMF. This paper presents the work done in determining the optimum stator/rotor pole arc ratio that will produce a low cogging torque and maintaining a trapezoidal back EMF shape. The study is performed on a generic four pole single phase surface mounted PM brushless DC motor. An accurate 2D finite element modelling (FEM) software was employed to numerically analyse the magnetic field distribution inside the motor. The results show that there is only one stator/rotor arc length ratio combination that produces a flat trapezoidal back EMF shape with reduced cogging torque.