Three dimensional analysis of magnetic force and torque in a BLDC motor due to the axial variation of yoke and pole

The magnetic field in a brushless DC motor not only produces toque as the output of a motor, but also plays a major role as a source of vibration in the machine. Vibration is produced by the rotating magnetic forces. Jang et al [1,2] investigated the existence of unbalanced radial magnetic force for the rotationally asymmetric motor as well as the characteristics of magnetic force and torque.