Optimization Design And Flux-weakening Capability Analysis Of Consequent-pole Interior Permanent Magnet Synchronous Machines

Interior Permanent Magnet Synchronous Machines(IPMSM)have the advantages of small size,light weight,high power density,high torque density,and high efficiency.They are currently widely used in aerospace,defense,and electric vehicles.As a drive motor for electric vehicles,the IPMSM also needs to have a good flux-weakening speed-expansion capability.The traditional pole IPMSM can meet the above requirements,but rare earth permanent magnets are extremely expensive,rare earth resources are scarce and non-renewable worldwide.Therefore,in order to save permanent magnets,this paper proposes that the consequent-pole IPMSM that can maintain or even improve the output torque and flux-weakening speed-expansion capability and other electromagnetic properties under the condition of saving the permanent magnets.The main analysis contents are as follows:The classification and common structure of permanent magnet synchronous motors are introduced,the research statue of IPMSM and consequent-pole IPMSM motors with different structures at home and abroad is discussed and the importance of the flux-weakening speed-expansion capability to the drive motors that require accelerated operation is pointed out.The research history of flux-weakening speed-expansion is demonstrated in detail.12-slot 10-pole IPMSM with low cogging torque and high winding factor is selected as the research object.The finite element software is used to establish a parametric two-dimensional simulation model of five common IPMSM: traditional-pole bar-type and consequent-pole bar-type,V-type,U-type and▽-type IPMSM.Taking the output torque and torque ripple as the optimization targets,multi-objective optimization is performed on the permanent magnet installation position.Non-inferior solutions of five IPMSMs on Pareto Front are selected for subsequent analysis and the rationality of the design is initially verified.The analysis focuses on the torque characteristics under low-speed MTPA control and the fluxweakening characteristics under high-speed flux-weakening control.Under two control strategies,the salient pole ratio that determines reluctance torque of the motor is the maximum in the traditional-pole bar-type and the minimum in the U-shape.However,the characteristic current that determines the flux-weakening capacity changes under different operating conditions.U-shaped and V-shaped structures with larger direct-axis inductance and smaller characteristic current at higher speeds have a stronger flux-weakening capacity.Therefore,it is concluded that the reluctance torque is related to the salient pole ratio,the flux-weakening characteristic is related to the characteristic current and has little relationship with the salient pole ratio.The anti-demagnetization capacity and overload capacity of the five motors are analyzed and compared.Taking the U-type motor as an example,the power factor,loss and efficiency of all operating conditions within double overload and triple base speed are analyzed.It is concluded that the consequent-pole IPMSM can obtain higher output torque,better flux-weakening speed-expansion capability and similar efficiency while saving permanent magnets compared to traditional IPMSM.The output torque at low of the ▽-type consequent-pole IPMSM is the largest and the U-type consequent-pole IPMSM has the best flux-weakening speed-expansion capability.The U-type consequent-pole IPMSM is processed and the experiments of the motor are carried out.The experimental contents include the back electromotive force(Back-EMF),cogging torque,average torque,overload capacity,and flux-weakening speed-expansion capability.The experimental results are compared with the finite element results to verify the correctness of the finite element simulation and the conclusions obtained.