Design Analysis And Optimization Of Fractional-slot Concentrated Winding Permanent-magnet Motor

New energy electric vehicles have been recognized by the society and favored by users for their clean and environmentally friendly properties.As the core power unit of electric vehicle,the performance of motor has a profound impact on the performance evaluation and actual operation of the whole vehicle.Compared with other types of permanent magnet synchronous motor,fractional-slot concentrated winding permanent magnet synchronous motor has the advantages of simple structure,low copper loss and high efficiency.It is these advantages that make it widely used in the power plant of new energy vehicles.Therefore,the study of fractional-slot concentrated winding permanent magnet synchronous motor is the key step to solve the problem of energy shortage and environmental pollution.In order to meet the requirements of high efficiency,energy saving,small volume,low noise and vibration,the fractional-slot concentrated winding permanent magnet motor is proposed as the power unit of new energy vehicles.However,the inherent cogging torque of the permanent magnet motor will increase the torque ripple of the motor,and the fractional slot concentrated winding will increase the content of harmonic magnetic field,which will increase the eddy current loss of the permanent magnet,these problems will interfere with the normal operation of the motor.Aiming at these problems,this thesis proposes measures that can reduce cogging torque and eddy current loss of permanent magnets,as well as optimization methods of motor optimization.Firstly,based on the theory of fractional-slot concentrated winding,the pole slot matching of motor is studied in detail.Combined with the design principle of permanent magnet motor,a 40 k W 12 slot 8-pole fractional-slot concentrated winding permanent magnet motor for new energy vehicles is designed.On this basis,the magnetic field performance of the motor under no-load condition is analyzed.According to the analysis of the magnetic field performance,the electromagnetic design scheme of the motor is proved to be reasonable.Secondly,the calculation formula of cogging torque is analyzed based on the energy method.In addition,the influence of the auxiliary slot on the stator surface,unequal slot opening cooperate and unequal-thickness permanent magnet on the cogging torque are studied.Moreover,the calculation formula of unequal slot opening of stator,the influence of the depth,width and number of auxiliary slots and the eccentricity of permanent magnet on the cogging torque are studied in detail.It is verified by the finite element method that the above three methods can effectively reduce the cogging torque.Then,the influence of the uniform segmentation of the permanent magnet in the circumferential and axial directions,the width of the stator slot and skewed slots on the eddy current loss of the permanent magnet is studied in detail.It is verified that the eddy current loss of the permanent magnet can be effectively reduced by uniform segmentation of the permanent magnet,changing slot width and skewed slots.Finally,based on the Taguchi experiment method,the air gap length,permanent magnet thickness,pole arc coefficient,stator tooth width and slot width are taken as the five optimization factors of the Taguchi experiment.The motor efficiency,cogging torque and torque generated by unit permanent magnet are taken as the three optimization goals of the Taguchi experiment,and the optimization scheme is determined by orthogonal experiment.The electromagnetic performance of the optimized motor is calculated by two-dimensional finite element method,and the feasibility of the Taguchi optimization method is verified by comparative analysis.