Design And Analysis Of Direct-drive Permanent-magnet BLDCM For Electric Vehicle

Along with the rapid development of industry automobile, the negative effects，such asthe shortage of oil resources and environmental pollution and climate warming, start toappear prominently. As a type of new energy vehicles, electric vehicle (EV) will be the maindirection of the improvement of vehicles. The performance of driving motor has a directinfluence on dynamic property, stability and driving range of EV. So designing a drivingmotor which can meet the driving safety and has wide range and high efficiency is of greatsignificance.In order to determine the technical indicator of motor, such as the rated power, voltageand current, analyzed the requirements of motor for EV; The equation of permanent magnetBLDCM provided the theoretic foundation for the method of winding switching; Accordingwith the analysis of the characteristic of the car and the motor, mechanical structure model ofdirect-drive motor was build by SolidWorks, including the water cooling system; The theorythat winding of series-parallel connection can improve the torque and the range of speed wasanalyzed and the overall design schemes was provided; And the installation method of Hallposition sensors (HPS) was also provided.In the initial design of motor, the magnetic circuit method and related empiricalformula were used to calculate parameters, and Ansoft Maxwell was applied to carry out thefinite element analysis and simulation of main parameters, such as the main dimensionsmagnetic, electrical and magnetic load, slot-pole combinations, type of plot, size ofpermanent magnetic, circuit structure, to accomplish the optimization design of theelectromagnetism.Based on mechanical structure and electromagnetic scheme, the performance of themotor were simulated under both unload state and rated-load state. The change regular anddistribution of electromagnetism was got, such as electromagnetic torque, winding current, voltage waveform, speed, winding flux linkage, induced electromotive force and core loss,and the magnetic field distribution also can be observed. Analyzing the impact of motordesign parameters on the cogging torque to weaken the cogging torque for the motor’s furtheroptimizationThe winding switching of brushless DC was presented to improve the motor speed range.The series-wound mode can be used in low-speed and hill-climbing driving conditions toincrease output torque of the motor; while the parallel-wound mode can be used inhigh-speed and light-load conditions to widen the speed range of the motor. Series-woundand parallel-wound mode was simulated in Matlab/Simulink environment. The result showsthat series-wound mode can satisfy the demands of starting-acceleration and hill-climbingdriving conditions perfectly.