| The electric wheel has been widely concerned in the field of electric vehicle due to many advantages,such as simplified chassis structure,high space utilization and operation efficiency,shorter vehicle development cycle,and so on.The electric wheel still in development by our team is selected as the subject of this text,which adopting multi motor parallel working mode.When dealing with different working conditions,one rotor or multi rotor can be chosen to work for higher efficiency.But in certain extreme working conditions,especially in full load and low speed working conditions for a long time,the temperature of the working motor will increase due to the efficiency of the working rotor reducing considerably and the motor may fail to work normally.If we can make an analysis for the temperature rise of the motor working in different working conditions and put forward an efficient cooling measure,it will be easier to improve the working efficiency and thermal stability of the motor.This study is started from the problem.(1)A flow model applicable to the hub motor is established,then the flow model is confirmed by the experimental results of the sample motor.In consideration of the model complexity and the experimental sample,only the third stage motor is modeled and analyzed.Basing on the analysis results,a new structure named “Radial Hole Rotor” is put forward,in which the radial holes play the role of air flow source and partial air cycle channel.Through air circulation in the motor,the temperature of the air will be better-distributed and then the overall thermal transfer efficiency of the motor will be improved.In the meantime,the volume of the motor will not be increased.(2)Several flow models are established calculated for the hub motor with different radial holes.Through comparative analysis on the results,it is found that,the wall heat transfer coefficient of the rotor and air flow state around the rotor are extremely dependent on the configuration parameter of the radial holes.After the analysis,the optimal one among the radial holes structures mentioned above is picked out.Then for the defined structure,a study is conducted,that how the clearance between rotor and casing and the motor speed influence on the air flow state in the motor,and then some meaningful suggestions can be put forward for the preliminary structural design and the power allocation of the motor.(3)In the basis on the flow model,two thermal model of the hub motor with common rotor and radial holes rotor are established individually.Through the comparison between the results of the temperature rise,it is found that the temperature rise of the casing and air in the latter motor is better-distributed.Better-distributed air temperature rise can improve the effective utilization rate of heat exchanging pipelines embedded in the casing.Especially for the multi motor structure of the electric wheel,the effective heat transfer surface area between casing and air in the motor will be greatly increased.After the spoke structure is optimized,the spoke rotor can solve the problem well of extreme temperature rise of hub motor in extreme working condition.It's beneficial to further improve the power density of the motor. |
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