Magneto-Thermal Coupling Analysis And Cooling Re-Search Of U-Shaped Built-in Permanent Magnet In-Wheel Motor

In recent years,new energy electric vehicles have been widely used in the world due to the advantages of no pollution and zero emission.As the core drive component of new energy vehicles,permanent magnet in-wheel motors are widely used in the electric vehicle industry due to their small size,high efficiency and high torque density.However,the high power density of permanent magnet in-wheel motors generates more heat during operation;at the same time,the working environment of permanent magnet in-wheel motors is usually located in a relatively confined space with difficult air circulation,which makes it difficult to transfer the heat generated during operation to the outside world for effective heat dissipation;in addition,the high temperature may cause thermal aging of insulation materials,decrease of remanent magnetic density of permanent magnet materials,and even cause irreversible demagnetization of permanent magnet materials.This will not only shorten the running time of new energy electric vehicles,but also pose a great threat to the safety of the vehicles.Therefore,it is important to study the thermal performance of the permanent magnet in-wheel motor,focus on the analysis of its serious heat generation parts and design a suitable cooling system to realize the safe operation of electric vehicles.In this paper,a U-shaped built-in permanent magnet in-wheel motor(UBPMIWM)is investigated to address the heat dissipation difficulties of permanent magnetin-wheel motors,which use a U-shaped arrangement of permanent magnets in the rotor slot to enhance the magnetic field and achieve high torque output by using the aggregation effect.In this paper,the topology,electromagnetic performance,temperature field analysis and cooling system design of this motor are investigated in the following aspects:1.the structural parameters of the U-shaped built-in permanent magnet in-wheel motor are optimized,and the topology of the motor is determined based on the optimization results.On this basis,the electromagnetic performance(magnetic field distribution,permanent magnet chain and no-load counter potential,air gap magnetic density,electromagnetic torque)and the thermogenic source of the U-shaped built-in permanent magnet in-wheel motor under rated operating conditions are analyzed and calculated using the finite element method to provide a basis for the magneto-thermal coupling analysis.2.to carry out the research on the influence of temperature rise on the electromagnetic performance of the motor.According to the basic theory of heat transfer,the three-dimensional temperature field analysis model of the in-wheel motor is established.On this basis,the steady-state temperature field distribution of the in-wheel motor under natural cooling conditions was analyzed by using the magneto-thermal coupling method,and the parts of the motor that generate more serious heat were identified,and the changes of the electromagnetic performance of the in-wheel motor before and after considering the temperature were analyzed.3.The cooling structure design of the in-wheel motor is studied.Considering the difficulty of cooling the in-wheel motor under natural cooling conditions,the temperature rise is high.Based on the basic theory of fluid dynamics and the temperature field distribution of the in-wheel motor under natural cooling conditions and the structural characteristics of the motor,two types of axial waterway structures,single Ushaped and double parallel U-shaped,are designed to cool the in-wheel motor.At the same time,the two waterway structures are compared from several angles and the best cooling solution is selected.According to the analysis of magneto-thermal-bidirectional coupling method,the selected cooling solution reduces the influence of motor temperature rise on the electromagnetic performance of the motor.4.The prototype of the in-wheel motor was fabricated and the related experimental platform was built.The electromagnetic performance,dynamic response performance,and temperature variation curve of the prototype were tested,and the experiments verified the rationality of the prototype.