Imbalanced Force in Permanent Magnet Brushless Motors With Magnetic and/or Electric Asymmetries

In a permanent magnet brushless (PMBL) motor, any special structural design in the stator lamination may induce asymmetry in the magnetic circuit to result in intrinsic imbalanced force. Likewise, an asymmetrical phase winding arrangement may also induce imbalanced force in the motor when the armature currents are flowing. This paper presents the analysis of the imbalanced forces of two PMBL motors in an electric coolant pump system with magnetic and/or electric asymmetries using both numerical simulation and prototyping test. The results confirm the validity of force calculation method and illustrate the contributions of magnetic and electric asymmetries to the imbalanced forces in PMBL motors.