【作者】 李晨；

【导师】 花为； 章恒亮；

【作者基本信息】 东南大学 ， 电气工程， 2024， 硕士

【摘要】 轮毂电机驱动将驱动电机直接集成于轮毂内,独立驱动各车轮,具有车内空间余量大、整车质量轻、车辆控制多元化等优势,是电动汽车发展的重要方向,具有广阔的应用前景。然而,由于轮毂电机工作环境恶劣、结构集成度高,使得电机发热严重,这可能导致绝缘老化和永磁体不可逆退磁等风险,显著影响轮毂电机的使用寿命和整车的可靠运行。在此背景下,本文对轮毂电机的温度场特性与冷却设计进行了深入研究。传统电机热模型中,损耗往往被认为均匀分布的发热源,这与实际的损耗分布并不相符,会导致电机热分析中不可避免地产生误差。为了提高轮毂电机温升预测的精度,首先分析了损耗空间分布的规律,特别揭示了定子铁耗切向分布不均衡的现象。其次,基于气隙磁场调制理论分析了气隙磁场的时空分布,阐明了定子铁耗切向分布不均衡的机理。然后,基于损耗分布的实际情况提出了轮毂电机单元齿离散损耗分布集总参数热模型,准确地预测了温度场中的局部热点,提高了稳态温升估计的准确度。最后,提出了一种新型轮毂电机定子冷却设计方案,有效改善了电机散热效果,提高了功率密度。本文主要研究内容与创新点如下:(1)阐述了永磁轮毂电机损耗计算方法,分析了不同工况下轮毂电机损耗分布规律,尤其是定子铁耗的空间分布,特别地,揭示了定子铁耗切向分布不均衡现象。总结归纳了永磁轮毂电机损耗分布规律,提升了轮毂电机热分析中热源模型的准确度。(2)基于气隙磁场调制理论,建立了轮毂电机磁场解析模型,分析了气隙磁场的时空分布。着重从位置角与永磁/电枢磁势相位差关系,以及永磁/电枢磁势相位差与气隙合成磁密幅值关系,分析了轮毂电机每个定子齿气隙区域合成磁密幅值分布规律,系统地阐明了定子铁耗切向分布不均衡的机理,并利用有限元方法进行了验证。(3)提出了一种单元齿离散损耗分布集总参数热模型,在兼顾损耗分布的基础上,简化了轮毂电机热模型。着重针对电机的主要发热部件,以定子齿损耗分布周期为单元建立轮毂电机热模型。分析了轮毂电机定子、机壳与空气间的对流边界。所提出的模型与传统模型相比,稳态温升计算准确度高,并可精确预测温度场中的局部热点。(4)提出了一种新型的轮毂电机定子冷却设计,定子绕组端部插入T形高导热模块并配合定子壳体水套冷却。这种配合散热模块的轮毂电机壳体冷却设计,不仅高度集成了轮毂电机拓扑与冷却结构,而且有效改善了轮毂电机定子绕组端部的散热条件,提高了轮毂电机的功率密度。(5)搭建了一台12槽10极轮毂电机样机温升测试实验平台,完成了空载、不同负载率、不同转速、正反转等稳态温升实验,实验结果验证了轮毂电机损耗分布规律,证明了单元齿离散损耗分布集总参数热模型的准确性和可预测局部热点的优势。更多还原

【Abstract】 In-wheel motor drive,which integrates the drive motor directly into the hub,independently drives each wheel,and possesses advantages such as ample interior space,light vehicle weight,and diversified vehicle control,represents an important direction for the development of electric vehicles,with broad application prospects.However,due to the harsh working environment and high structural integration of in-wheel motors,severe motor heating occurs,which may lead to risks such as insulation aging and irreversible demagnetization of permanent magnets,significantly impacting the service life of in-wheel motors and the reliable operation of the entire vehicle.In this context,an in-depth study on the temperature field characteristics and cooling design of in-wheel motors is conducted.In traditional motor thermal models,losses are often considered as uniformly distributed heat sources,which does not correspond to the actual distribution of losses,inevitably resulting in errors in motor thermal analysis.To enhance the accuracy of temperature-rise prediction for in-wheel motors,firstly,the regularity of loss spatial distribution is analyzed,particularly revealing the phenomenon of uneven tangential distribution of stator iron losses.Secondly,based on the theory of air gap magnetic field modulation,an analytical model of the magnetic field of in-wheel motors is established and the spatial and temporal distribution of the air gap magnetic field are analyzed.The mechanism of the uneven tangential distribution of stator iron losses is elucidated systematically.Subsequently,based on the actual distribution of losses,a parameterized thermal model for in-wheel motor unit tooth discrete loss distribution is proposed,accurately predicting local hotspots in the temperature field and improving the accuracy of steady-state temperature rise estimation.Finally,a novel stator cooling design for hub motors is proposed,effectively improving motor heat dissipation and increasing power density.The main research contents and innovations of this paper are as follows:(1)Elaboration of the calculation method for permanent magnet in-wheel motor losses and analysis of the distribution regularity of hub motor losses under different operating conditions,especially the spatial distribution of stator iron losses,with a special emphasis on revealing the phenomenon of uneven tangential distribution of stator iron losses.The summary and induction of the distribution regularity of permanent magnet hub motor losses enhance the accuracy of the heat source model in in-wheel motor thermal analysis.(2)Based on the theory of air gap magnetic field modulation,an analytical model of in-wheel motor magnetic field is established,and the spatial and temporal distribution of the air gap magnetic field is analyzed.The distribution regularity of the air gap composite magnetic flux density corresponding to each stator tooth surface of the in-wheel motor is analyzed from the relationship between position angle and phase difference between permanent magnet/armature magnetic potentials,as well as the relationship between phase difference between permanent magnet/armature magnetic potentials and air gap composite magnetic flux density amplitude,systematically elucidating the mechanism of uneven radial distribution of stator iron losses and verifying it using finite element method.(3)A parameterized thermal model for unit tooth discrete loss distribution of in-wheel motors is proposed,which simplifies the thermal model of hub motors based on considering loss distribution.Focusing on the main heating components of the motor,the thermal model of in-wheel motors is established based on the periodicity of stator tooth loss distribution.The convection boundaries between in-wheel motor stator,casing,and air are analyzed.Compared with traditional models,the proposed model has high accuracy in steady-state temperature rise calculation and can accurately predict local hotspots in the temperature field.(4)A novel stator cooling design for in-wheel motors is proposed,where the stator winding ends are inserted into T-shaped high thermal conductivity modules and combined with stator casing water jacket cooling.This cooling design,combined with the heat dissipation module of the in-wheel motor casing,not only highly integrates the topology and cooling structure of the in-wheel motor but also effectively improves the heat dissipation conditions of the stator winding ends of the in-wheel motor,thereby increasing the power density of the in-wheel motor.(5)A test platform for steady-state temperature rise experiments of a 12-slot/10-pole in-wheel motor prototype is constructed,and experiments are conducted under no-load,different load rates,different speeds,forward and reverse rotations.The experimental results verify the regularity of in-wheel motor loss distribution,demonstrating the accuracy of the parameterized thermal model for unit tooth discrete loss distribution and the advantages of predicting local hotspots.更多还原