Study Of Fractional-slot Concentrated-winding Permanent-magnet Machine With Enhanced Reluctance Torque

As one of the key components of the electric vehicle,the driving motor determines the quality of electric vehicle.Recently,the fractional-slot concentrated-winding permanent-magnet(FSCW-PM)machines have been gaining interest due to their advantages of short end winding,low copper loss,high slot fill factor and good fault-tolerant performance.Moreover,increasing the reluctance torque has been a major challenge for FSCW-PM machines.In order to improve the reluctance torque of FSCW-PM machines,firstly,the reluctance torque with different winding structure are compared,revealing the reason that why the reluctance torque of FSCW-PM machine is low.Then,the permeance of air-gap and the reactance of d-and q-axis are derived out by using the slot and pole.Furthermore,analyze the influence of different rotor structure on reluctance torque and propose a general rule for improving the reluctance torque from the aspect of slot pole combinations and the rotor structure.Finally,the FSCW-PM machine with enhanced reluctance torque is designed.The investigations of this paper can lay the foundation for the further study of the reluctance torque for FSCW-PM machines.The main contents of the study are as follows:1.Based on the reluctance torque,the structure characteristics of the FSCW-PM machines are expounded.The different operating states of machine are discussed.Aiming at the reluctance torque,the phasor diagram of demagnetization state is mainly analyzed.At the same time,the equivalent magnetic circuits of d-and q-axis are also investigated.Finally,the influence of the winding structure on reluctance torque is analyzed,and find out the reason that why the reluctance torque of FSCW-PM machine is low.2.The permeance of air-gap and the reactances of d-and q-axis are derived out by using the slot and pole and the correctness of the theoretical derivation is verified by using the finite element simulation.Then,the reluctance torque of different slot pole combinations are compared and analyzed.Thus,a general rule for improving the reluctance torque is summed up.Finally,the general rule is validated by using the existing machine.3.Analyze the method of increasing the reluctance torque from the rotor structure.Including the type of PMs,the layers of PMs and the flux barriers on rotor core.Then,a new split rotor structure is proposed to improving the reluctance torque effectively.Based on these studies,the slot pole combination and rotor structure of the prototype are selected,and the model of reluctance torque enhanced machine is determined initially.4.According to the design requirements of the machine,the electrical load and magnetic load of the machine are selected,and the size parameters of the machine are calculated by using the power size equation.Then,the machine is optimized,including the stator structure parameters and the PMs parameters,thus the final scheme of the machine is determined.5.The performance of the existing machine and the proposed machine is compared,including the inductances,the reluctance torque and the flux weakening capability.Furthermore,the correctness and the superiority of the proposed machine are proved.Finally,the temperature of the proposed machine is analyzed based on Motor CAD,and the temperature distribution of each part of the motor is obtained,the practicability of the proposed machine is validated.