Cp. Cho et al., DETENT TORQUE AND AXIAL FORCE EFFECTS IN A DUAL AIR-GAP AXIAL-FIELD BRUSHLESS MOTOR, IEEE transactions on magnetics, 29(6), 1993, pp. 2416-2418
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 conclu
sions of a finite element analysis (FEA) that focused on the detent to
rque and axial force effects in the motor. Design options and manufact
urability issues such as magnet skewing, staggering of the two stators
, and axial misalignment of the rotor are examined. Detent torque is r
educed by magnet skewing, and to an even greater extent by stator stag
gering. However, axial force variations on the rotor are aggravated by
stator staggering. In addition, it is found that axial misalignment o
f the rotor has a deleterious effect on both detent torque and axial f
orce variations.