Influence of number of poles on the torque of DC brushless motors with auxiliary salient poles

The influence of the number of poles and inside or outside field structure on the torque of brushless DC motors with auxiliary salient poles has been investigated. Nonlinear finite-element-method analysis, associated with the integration of Maxwell's stress tensor, has shown that, for some structures, especially those with outside field, this influence can be significant and that four-pole outside-field motors are the most advantageous.<>