【作者】 陈博；

【导师】 王晓远；

【作者基本信息】 天津大学 ， 电气工程， 2014， 硕士

【摘要】 随着人类社会的发展,人们财富的日益增多,生活水准的不断提高,汽车产销量逐年递增。在为人类带来便利的同时,也产生了诸多的问题,如环境污染和能源危机一直困扰着人们的生活。电动汽车的使用既节约能源,又减少了污染,有利于人类社会的可持续发展。轮毂电机凭借其体积小,可采用复杂的驱动方式来实现电机整体性能效率提高的优点被广泛用于电动汽车。而轮毂电机最常用的永磁同步电机由于内部永磁体和绝缘材料的特性会受温度变化的影响。在过高温度下会造成绝缘老化、永磁体退磁等不良后果。因此如何有效移除轮毂电机所产生的热量就成为本文的研究重点。本文采用内油冷却的散热方式对电机散热系统主要做了如下研究工作:首先,在电机电磁场理论与流体力学理论的基础上,通过磁热耦合的方式利用有限元方法对比研究了内油冷却和自然冷却两种方法的散热效果。通过有限元仿真软件建立电机模型,应用传热学理论与流体力学公式推导定转子间在不同流体介质和不同转速情况下的对流传热系数。根据所得系数进行仿真,根据仿真结果研究不同冷却方式电机的温度分布情况,研究两种冷却方式的散热效果。其次,对电机转速、超载电流对于内油冷却方式散热能力的影响进行了研究,得出不同转速、超载电流运行情况下电机的各热源分布、电机稳定运行后的温度分布及运行稳定温度。建立了在采用内油冷却散热方式情况下,电机转速与热源、温升的关系;以及电机的超载能力、超载电流与温升的关系。再次,讨论了采用内油冷却方式时油量与散热能力的关系。分析了使用较少油量情况下转速与散热的关系。通过流体力学理论推导,得出在使用较少油量情况下,冷却油在电机内部随转速的变化而处于不同的运动状态,从而推导出不同的转速情况下的散热能力。并用1/3油量与满油量通过仿真分析油量对电机散热能力的影响。同时,通过对电机本体端盖的优化进一步改进电机的整体散热能力。最后,对轮毂电机采用内油冷却散热方式进行温升实验,通过对比实验结果与仿真结果证明本文所建立的模型在通过磁热耦合有限元仿真所得到结果的正确性。证明了基于各仿真结果所得出的结论适用于实际情况。更多还原

【Abstract】 Nowadays, the production and sales of private cars increase rapidly with the social development and the increase of living standard. It makes people’s life convenient, but suffers from serious environmental and energy problems. Fortunately, electric vehicles were successfully developed to saves energy and reduce pollution. The in-wheel motor is widely used in electric vehicle by virtue of its small in size and nice efficiency presented by complex control strategies. Normally, permanent magnet synchronous motor(PMSM) is the best choice for in-wheel motor. But the characteristics of permanent magnet and insulating materials are affected by the temperature of motor. In fact, the high temperature caused by the heat generated from motor could lead to insulating materials aging and permanent magnet demagnetizing, and even motor burning. Thus, the efficient removal of the generated heat by cooling is the goal of this study. In this paper, the method of closed oil cooling is employed to study on the motor cooling system as following:Firstly, the cooling efficiency of oil cooling and natural cooling methods has been comparatively researched by Finite Element Method(FEM) on the basis of electromagnetic field theory and hydrodynamics theory. The motor model is established by finite element simulation software. The convective heat transfer coefficient between the stator and rotor is deduced by the heat transfer theory and hydrodynamics equations at different speeds or in different fluid media. According to the coefficients obtained from the two cooling methods,the simulating experiments were carried out. The temperature distribution of motor and the cooling efficiency of the two cooling methods were then discussed with the simulating results.Secondly, the influences of motor speed and overload current to the efficiency of oil cooling method were investigated. The distribution of heat sources at different speed or overload current, the temperature distribution of motor at steady-state operation were analyzed. The relationship among temperature rise, heat and speed, and the relationship among overload capacity of motor, overload current and temperature rise were established.Thirdly, the relationship between the oil amount and the cooling efficiency was investigated. The relationship between speed and temperature rise in the case of less oil cooling was examined. The motion state of oil was studied by hydrodynamic theory in the case of less oil. The cooling efficiency at different speed was obtained. The conclusions were verified by simulation. Comparison study on the cooling efficiency between 1/3 and full oil amount was carried out.Finally, the temperature rising experiments of full oil cooling were carried out.Comparing the experimental results and the simulating results demonstrated that the results from the model and magnet-thermal coupling FEM simulation are correct in this paper.更多还原