Unbalanced magnetic pull induced by drive current in PM-BLDC motor operation

In the applications of high performance permanent-magnetic brushless DC (PM-BLDC) motor, the effects of unbalanced-magnetic-pull (UMP) is very concerned. Besides the intrinsic and extrinsic reasons, the motor drive current may also be an UMP source if the armature winding design is not reasonable. This paper presents an analytic model for analyzing the UMP induced by electromagnetic (EM) structure and drive current of the PM-BLDC motor, and the model can simplify effectively the analysis procedure. The analysis shows that, the UMP induced by the drive current can be avoided by using the reasonable winding structure, magnetic pole-pairs and stator slot number. For verifying the effectiveness of the analytic method proposed, several PM-BLDC motors are analyzed with the numerical method to confirm the effectiveness of the UMP model presented.