Field weakened axial-gap surface permanent magnet motor for automobile traction use without gear ratio change

An axial flux permanent magnet brushless motor is designed with variable stator alignment of independent stators, thus allowing field-weakening via a controllable and variable generated-voltage constant. This feature is particularly valuable in vehicle traction motors with large constant-power speed-ratio, where there is also a strong desire to eliminate gear changes and keep the overall size of the motor drive small. The advantage of high pole count as applied to this technique is discussed and the impact on efficiency over typical driving cycles is shown.