Control of a variable-winding brushless motor with the application in electric scooters

This paper presents the drive control of a variable-winding brushless DC motor for electric scooters. The approach is based on changing the winding connection on the motor's stator where the two sets of motor windings are controlled alternately to achieve both high starting torque and high operating speeds. The series connection is used at low speed operation for high torque and gives smooth acceleration from a standing start, and the parallel connection is used mainly for high-speed operation. A closed-loop torque control scheme is employed such that the torque-speed characteristics of the drive output have a function similar to that of continuously variable transmissions (CVT). By combining the motor winding connection control and the torque control, this 2-state-CVT is able to improve the overall efficiency and reduce the weight of electric scooters.