Investigation and Regulation of High-Efficiency Region Boundary of Variable Magnetic Flux Permanent Magnet Motor

With the increasing complexity of electrical vehicles (EVs), the wide-speed-range high-efficiency characteristics of EV drive motors are in strict demand. In this study, the variable magnetic flux effect is introduced into a permanent magnet (PM) motor, and a variable magnetic flux permanent magnetic (VMF-PM) motor is proposed. First, the flux is adjusted flexibly to synchronously broaden the speed regulation range and high-efficiency region. Subsequently, an efficiency analytical model is developed considering the motor speed, current, and flux variations. It is indicated that by the purposeful design of the variable flux leakage topology, the efficiency under high speed can be improved based on a theoretical investigation of the high-efficiency boundary. In addition, based on finite element analysis, the performances before and after optimization of the key parameters of the VMF-PM motor are investigated, including the flux variable characteristics and efficiency characteristics. Finally, a prototype motor is built and tested. Both theoretical analysis and experimental results confirm that based on the assistance of the variable magnetic flux effect, the motor high-efficiency region is broadened effectively, providing a potential research path for designing a wide-speed-range high-efficiency motor.