| In recent years,with the problem of energy shortage and environmental pollution becoming more and more serious,people’s awareness of environmental protection has been gradually strengthened,and the development and research of new energy vehicles have attracted more and more attention.Because of its small size,light weight,high power factor and high transmission efficiency,hub motor has become the research object of many automobile manufacturers and designers.Compared with the traditional fuel vehicles,the hub motor reduces the number of parts in the power transmission system and improves the power transmission efficiency of the drive system.However,due to the narrow and closed working space and poor air circulation of the hub motor,the heat generated by the hub motor can not be discharged in time;at the same time,reducing the volume of the hub motor,although improving the torque and power density of the drive motor,but also increasing the loss density of the motor,resulting in the high temperature rise of the motor.High temperature rise may lead to high temperature failure of motor insulation,decrease of permanent magnet magnetic density,and even lead to irreversible demagnetization,which seriously affects the safety and stability of new energy vehicles.Therefore,it is of great significance to analyze and calculate the temperature distribution of the hub motor,to study the serious part of its heating,and to design the cooling structure reasonably for improving the performance of the whole vehicle and prolonging the service life of the motor.In this dissertation,75 kW outer rotor permanent magnet synchronous hub motor is taken as the research object.Based on its electrical parameters,a threedimensional physical model is established,and the loss of each part under the rated working condition of the hub motor is analyzed and calculated.According to the thermal performance parameters of the material,the temperature distribution of each part under the natural cooling of the hub motor is calculated.For the part with serious heat generation,two kinds of models are designed The cooling structure iscompared with the results of natural cooling,and the cooling performance of the two schemes is analyzed.According to the basic theory of heat transfer,combined with the special structure of the research object,the heat transfer form between the parts of the hub motor is analyzed,and the physical model and temperature field attribute model of the hub motor are established.At the same time,in order to facilitate the calculation,on the premise of ensuring the calculation accuracy,the equivalent treatment of the motor winding and other parts is carried out,and the values of various thermal parameters in the calculation of temperature field are determined.Based on the basic theory of electromotor and electromagnetic field,the loss of each part of hub motor is calculated,and the heat generation rate of each part is calculated according to the loss and the corresponding volume of each part.Based on the obtained heat source and all kinds of thermal parameters,the temperature field distribution of the hub motor is obtained by simulation,and its temperature distribution law is analyzed.Several characteristic points are selected along the axis in the part with serious heat,which provides effective comparative data for the cooling optimization of the hub motor.According to the structure of the outer rotor of the hub motor,the basic theory of hydrodynamics,and the temperature distribution of the hub motor under natural cooling,two cooling schemes are designed: spiral water cooling and graphene composite cooling.The results show that the two cooling schemes can reduce the temperature rise of the hub motor to a certain extent,so that the hub motor can work normally within the required insulation level. |
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