【作者】 张旭；

【导师】 任万滨；

【作者基本信息】 哈尔滨工业大学 ， 电气工程， 2021， 博士

【摘要】 电磁继电器作为最基础的自动控制元件,应用遍及航空航天、信息通讯、电力能源等众多领域。电磁继电器在工作过程中不可避免地会发生触点回跳、金属熔桥和电弧放电等现象,由此引发的触点熔焊失效已成为制约电磁继电器电寿命与可靠性提高的关键。电磁继电器触点熔焊问题涉及材料物理性能退化、电弧侵蚀和机械动作等行为的相互作用,物理现象复杂多变。迄今为止,触点材料熔焊特性的相关理论分析与实验研究还不深入,还无法明确电磁继电器机械动作和负载类型等因素对触点熔焊的影响,对于电磁继电器触点在电寿命实验中发生熔焊失效的机理认识不足。针对以上问题,本文分别从触点材料熔焊特性、电磁继电器触点熔焊特性和电磁继电器触点熔焊失效机理三方面开展研究。首先,建立了触点材料在电阻热和电弧热作用下的熔焊特性传热分析模型,并提出了触点材料熔焊模拟方法,进而确定了影响触点材料熔焊特性的物理性能参数。然后,提出了电磁继电器触点熔焊特性的原位测试分析方法,实现了电磁继电器动作特性的模拟和触点电性能参数的在线测试,阐明了电磁继电器分合动作、机械参数和负载类型对触点熔焊特性的影响。最后,分析了电寿命实验中电磁继电器触点熔焊失效过程和失效模式,揭示了回跳电弧和熔桥的熔焊能力与触点材料的抗熔焊能力竞争机制下的熔焊失效机理。首先,建立了电磁继电器触点材料熔焊特性的传热分析模型,确定了影响触点材料熔焊力的关键物理性能参数。针对电阻热作用下的传热问题,提出了弹性接触条件下触点材料熔焊阈值电流、熔焊面积和熔焊系数的计算方法,并应用熔焊系数理论分析了典型材料的抗熔焊能力。在此基础上,分析了电弧热作用下的触点材料熔焊特性,建立了熔焊力与电气参数和材料物理性能参数之间的函数关系,确定了电弧电压、电弧电流、热导率、抗拉强度和熔焊比例系数是影响触点材料熔焊力的关键参数,为分析触点材料熔焊特性提供了理论依据。其次,提出了电磁继电器触点材料在电阻热和电弧热作用下的熔焊模拟方法,实验观测了触点材料熔焊力、熔焊面积和焊核抗拉强度。设计开发了触点材料熔焊模拟实验装置,实现了接触压力、负载电流、负载电压、回跳时间和回跳能量等参数的精确控制。进一步,采用熔焊模拟方法观测了Ag、Cu、AgSnO₂和AgNi触点材料在不同负载电流下的熔焊力和熔焊面积,进而拟合得到了焊核抗拉强度,并验证了触点材料熔焊特性的传热分析模型。结合触点电侵蚀区域的微观形貌和元素成分结果,阐明了触点材料在电阻热和电弧热作用下抗熔焊能力存在差异的原因,为测试评价触点材料抗熔焊能力提供了技术手段。再次,提出了电磁继电器触点熔焊特性的原位测试分析方法,实现了电磁继电器动作特性的模拟和触点电气参数、力学参数、表面轮廓信息的在线测试。为了探究电磁继电器分合动作、机械参数和负载类型对熔焊特性的影响,采用原位测试分析方法研究了电磁继电器闭合过程、分断过程和全过程带电条件下,回跳能量、接触电阻、熔桥能量和燃弧能量等电性能参数与熔焊力的关系,发现闭合回跳电弧和分断熔桥是引起触点熔焊的主要原因。建立了电磁继电器触簧系统机械特性分析模型,研究了不同开距、超程和空程条件下的熔焊力分布特征。理论分析了触点切换负载过程中的电气特性,明确了负载类型对熔焊力分布的影响,发现触点闭合回跳与容性浪涌电流的叠加作用可显著加剧触点熔焊现象。最后,阐明了电寿命实验中电磁继电器触点熔焊失效过程和失效模式,揭示了熔焊失效机理。通过开展阻性、容性和感性负载条件下的电寿命实验,研究了回跳能量、接触电阻、接触压力、燃弧能量、触点开距和触点动程等电性能参数的退化规律。应用扫描电子显微镜、金相显微镜和能量色散X射线光谱仪分析了失效触点的表面形貌、组织结构和元素成分,结合电性能参数退化规律阐明了触点熔焊失效过程并定义了三类熔焊失效模式,揭示了电磁继电器触点熔焊失效是电弧侵蚀、材料劣化和机械动作耦合作用的结果,电寿命实验中触点在电弧和熔桥的反复侵蚀下发生材料转移和元素偏聚,而材料劣化又会导致触点开距和触点动程减小,使得电弧对触点材料的侵蚀更加严重,当回跳电弧和熔桥的熔焊能力强于触点材料的抗熔焊能力时,电磁继电器触点熔焊失效。更多还原

【Abstract】 Electromagnetic relays,which are widely used in aerospace,communication and electric energy,are the most basic automatic control component.There are inevitable occurrences of contact bounce,molten metal bridge and arc discharge during the switching process of electromagnetic relay.Contact welding failure has become the key restrictions for longer electrical life and better reliability of electromagnetic relays.The contact welding,which involves the interaction of material deterioration,arc erosion and mechanical behavior,are complex and variable.So far,the theoretical and experimental researches on the welding characteristics of contact materials are still insufficient,and it is still unclear for the effects of mechanical parameters and load types on contact welding characteristics.Therefore,the understanding of the contact welding mechanism in the electrical endurance test of electromagnetic relays is far from reaching.In this paper,the welding characteristics of contact materials and the failure mechanism of electromagnetic relay contact are studied.First,the heat transfer model of the welding characteristics for contact materials under the conditions of resistance heat and arc heat is established,and the simulation method of contact welding is proposed.Then,the in-situ test and analysis method of contact welding characteristics is proposed,the influence of operation modes,mechanical parameters and load types on the contact welding are clarified explicitly.Finally,the welding failure process and failure modes of contacts are analyzed,and the failure mechanism of contact welding based on the competition of welding ability of bounce arc and molten bridge and the anti-welding ability of contact materials is revealed.First,the heat transfer model of the welding characteristics for contact materials is established,and the key parameters to determine the welding force are obtained.Then a mathematical model for calculating the threshold welding current,welding area and welding coefficient is proposed based on elastic contact conditions,and the anti-welding ability of contact materials is analyzed by welding coefficient.Furthermore,the relationship between the electrical parameters,the physical properties of material and the welding force is explored,and the key parameters to determine the welding force are obtained,including arc voltage,arc current,thermal conductivity,tensile strength and proportion coefficient,which lays a theoretical foundation for analyzing the welding characteristics of contact materials.Second,the method of simulating welding phenomenon under the conditions of resistance heat and arc heat is proposed,and the welding force,welding area and nugget tensile strength of contact materials are tested.A novel test rig which can control contact force,load current,load voltage,bounce time and bounce energy is designed.Then,the welding force and welding area of Ag,Cu,AgSnO₂ and AgNi contact materials under different load currents are observed,and the nugget tensile strength is calculated.Meanwhile,the heat transfer model of welding characteristics for contact materials is verified.The roles of resistance heat and arc heat in welding are clarified by analyzing the morphology and element composition of the contact erosion area,which provides a way for evaluating the anti-welding ability of contact materials.Next,the in-situ test and analysis method of contact welding characteristics for electromagnetic relay is proposed,which realizes the simulation of switching process of electromagnetic relay and the online testing of electrical parameters,mechanical parameters and surface profile information for contacts.In order to clarify the influence of operation modes,mechanical parameters and load types on contact welding characteristics,the effects of bounce energy,contact resistance,molten bridge energy and arc energy on contact welding for different operation modes are discussed respectively with the using of the in-situ test and analysis method,and it’s found that the bounce arc and molten bridge are the root reason of contact welding.The mechanical characteristics of spring system are analyzed theoretically,and the effects of the contact gap,over travel and free travel on the contact welding force are investigated experimentally.The influence of electrical load on the electrical characteristics in the contact switching process is studied,and it is confirmed that the contact bounce behavior and the inrush current in the making process could aggravate the contact welding phenomenon.Finally,the welding failure process and failure modes of contacts for electromagnetic relay in electrical endurance test are clarified,and the welding failure mechanism is revealed.The degradation processes of electrical characteristic parameters such as bounce energy,contact resistance,contact force,arc energy,contact gap and sliding distance in the electrical endurance test are analyzed respectively.The scanning electron microscope,metallographic microscope and energy dispersive X-ray spectrometer are used to analyze the surface morphology,microstructure and element composition of the failed contacts.Then,the contact failure process of electromagnetic relay has been clarified,and three types of welding failure modes have been defined.The contact welding failure is the result of the coupling of arc erosion,material degradation and mechanical parameter changes,when the welding ability of bounce arc and molten bridge is stronger than the anti-welding ability of the contact material,the contact welding fail ure occurs.更多还原