| Axial flux Permanent Magnet Synchronous Motor(PMSM)has a good application prospect in new energy vehicles due to its high-power density and wide efficient operating range.Due to the limited on-board battery capacity,improving the motor operating efficiency within the whole operating range has become one of the key issues to increase the vehicle driving mileage.However,3D magnetothermal characteristics of the axial flux PMSM lead to the difficulties to optimize the efficiency within a wide speed range by using accurate finite element method.Therefore,the combination of the precise magnetic circuit model and the thermal network model is adopted to optimize the design and analysis of the electromagnetic parameters and temperature rise distribution which affect the motor efficiency,so as to improve the vehicle driving distance.The main works of the thesis are as follows.Firstly,according to the magnetic circuit characteristics of axial flux PMSM,the magnetic circuit model is established by the split loop method.And then,parameters such as back electromotive force,terminal voltage and various losses are calculated,and the influence of PWM power supply on iron loss is also considered.According to the established magnetic circuit model,the operating characteristics of the vehicle motor in full operating domain are obtained.The accuracy of the model was simply verified by finite element method.Secondly,the steady and transient lumped parameter thermal network models of axial flux PMSM are analyzed and established.And then,the steady state and transient state temperature rises of the motor are calculated,the influences of cooling water flow velocity and loss distribution on the steady temperature rise at motor rated power and the transient temperature at motor peak power are analyzed.Thirdly,considering the effect of temperature rise on electromagnetic performance,the magnetothermal coupling model of axial flux PMSM is established.Furthermore,the influences of the main design parameters,such as the number of conductors per slot,the polar arc coefficient,the length of magnetization direction of the permanent magnet,the length of the air gap and the size of the slot,on the motor efficiency are analyzed.These parameters are analyzed and optimized with the aim of having a large proportion of high-efficiency zones in the whole operation interval and high comprehensive operation efficiency in different vehicle cycle conditions,and the main design parameters of the motor are selected according to the different design objectives.Finally,the finite element method is used to optimize the design of the permanent magnet of the motor,and then a prototype is designed and manufactured according to the optimized results.The results of the analysis and calculation are compared with the test data of the prototype,which verify the correctness of the analysis and design method and the calculation results. |
PDF Full Text Request