Design And Research Of Less-Rare-Earth Permanent Magnet Brushless Motor With Hybrid Permanent Magnet Material

Recently,with the development of environment-friendly energy,based on the concept of intellectualization,electrification,e-commerce,and sharing,a type of new energy electric vehicles(EVs)have been obtained close concerns of many automobile enterprises and research scholars in the global scale and promoted rapidly.Considering the complex requirements of the driving cycles,the excellent performance demands are required for the driving motor of the EVs.Due to the high power density,high efficiency and high reliability,permanent magnet(PM)brushless motors have been widely applied in driving motor field of EVs.However,duo to the crisis of rare-earth resource resulted from increasing market demand and unreasonable exploitation,non-rare-earth or less-rare-earth PM brushless motors is becoming one of the hot issues in the driving field of EVs.To decrease the dependence of rare-earth resource,by integrating with the multiple excitation resource,this paper proposes a less-rare-earth permanent magnet brushless(LRE-PMBL)motor with hybrid permanent magnet material.And,the systematical optimization design method and experiments of the LRE-PMBL motor are deeply studied.Firstly,the backgrounds of EVs and researches of non-rare-earth or less-rare-earth PM brushless motors are introduced.Based on the motor performance requirements of EVs,a new LRE-PMBL motor is proposed,where the rare-earth PM NdFeB and non-rare-earth PM ferrite are adopted.Then,through the comparisons of several feasible topologies with two kinds of PM material,the initial topology of the LRE-PMBL motor is determined.Based on the proposed principle of excitation sources equivalence,the usage ranges of the rare-earth and non-rare-earth PMs in the LRE-PMBL motor are deduced and the initial design of the LRE-PMBL motor is realized.Moreover,to obtain the optimal performances of the LRE-PMBL motor,a multi-objective stratified optimization strategy is proposed.According to the sensitivity analysis results of output torque,PM cost,torque ripple,cogging torque,and efficiency with respect to some key design parameters,the five optimization objectives are divided into two priority levels.The proposed optimization method can realize the trade-off optimization among multiple optimization objectives,which can provide an efficient optimization design method for PM motors.Next,the electromagnetic performances of the LRE-PMBL motor are analyzed in detail and compared with the rare-earth PM brushless(RE-PMBL)motor by finite element method,which include no-load flux distribution,no-load back-EMF,inductance,torque,PM operating point,demagnetization,etc.The validation and feasibility of design and optimization method of the LRE-PMBL motor are verified.Finally,the prototypes of the two motors are manufactured and the experiment platform is built.Based on the measured results of no-load and load characteristics of the two motors,the validation and feasibility of design and optimization method of the LRE-PMBL motor are further verified.