Transmissionless Selectively Aligned Surface-Permanent-Magnet BLDC Motor in Hybrid Electric Vehicles

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 the need for gear changes and keep the overall size of the motor drive as small as possible. The advantage of high pole count as applied to this technique is discussed, and the simulation impact on motor drive kilovoltampere, efficiency, gradability, acceleration, and maximum speed over typical driving cycles is shown.