Field weakened axial-gap surface permanent magnet traction motor design for constant power speed ratio

An axial flux permanent magnet brushless motor is designed with selectable stator alignment of independent stators, thus allowing a controllable and variable generated-EMF constant. This feature has particular value in vehicle traction motors with large constant power speed ratios, where there is also a strong desire to eliminate gear changes and keep the overall size of the motor drive small. The advantages of high pole count as applied to this technique are discussed and a general purpose optimum implementation of the field weakening is presented.