Gear variable switched reluctance motors and winding changeover strategy

For electric vehicles, in order to meet complex operating conditions of high torque at low speed and constant power at high speed, a concept of gear variable motor was proposed. Online winding changeover method was adopted to obtain the equivalent output characteristic of ordinary motors integrated with the gearbox. The motor windings were connected in series at low speed to increase the number of turns in each phase to achieve high torque output. When the motor speed rises, the windings are changed to parallel, the number of turns in each phase is reduced, and the back electromotive force (EMF) of the motor is decreased so as to broaden the speed range of the motor. The simulation and experiments based on a 150W, three-phase 12/8-pole switched reluctance motor (SRM) were carried out. The simulation model was constructed by two-dimensional look-up table method, and the dynamic analysis of the winding changeover process was realized. Combined with rotor position of the motor, a safe switching control strategy under zero current was proposed based on the current characteristic of SRM. The topology of the switching circuit was designed. In order to verify effectiveness and viability of the strategy, an experimental platform was built. The results show that the proposed scheme can achieve fast and safe changeover of motor windings under zero phase current. © 2022, Harbin University of Science and Technology Publication. All right reserved.