DETENT TORQUE AND AXIAL FORCE EFFECTS IN A DUAL AIR-GAP AXIAL-FIELD BRUSHLESS MOTOR

A permanent magnet brushless motor having a dual air-gap, axial-field configuration has been designed and constructed to achieve high power and energy density. Reported here are the modeling approach and conclusions of a finite element analysis (FEA) that focused on the detent torque and axial force effects in the motor. Design options and manufacturability issues such as magnet skewing, staggering of the two stators, and axial misalignment of the rotor are examined. Detent torque is reduced by magnet skewing, and to an even greater extent by stator staggering. However, axial force variations on the rotor are aggravated by stator staggering. In addition, it is found that axial misalignment of the rotor has a deleterious effect on both detent torque and axial force variations.