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Study the background and significance of electric contact arc invasion

Electrical contact materials are the core components of electrical motors and appliances, and their performance directly affects the quality stability and service life of these products, which is called the “heart” of electrical appliances. Electrical contact materials are subject to mechanical wear, environmental chemical corrosion and arc erosion in the process [1], of which arc erosion has the greatest impact on electrical contact materials [2].

Arc erosion of electrical contact material is the process in which the electrode surface is subjected to arc heat flow input and arc force, causing the electrical contact material to detach from the contact body in the form of evaporation or liquid spattering, solid shedding, etc. [3].

The electrical contacts are subjected to arc erosion, which can cause undesirable consequences such as reduced contact reliability and shortened electrical life. Therefore, the study of arc erosion of electrical contacts has been an important direction in the field of electrical contact theory and electrical contact applications.

Arc erosion is a complex physical phenomenon related to many factors, such as electrical factors (voltage, current and load), material factors (physicochemical properties, manufacturing process and additives), mechanical factors (contact shape and size, electrode spacing, breaking speed and arc motion) and environmental factors (temperature, humidity, ambient medium and pressure).
Therefore, the study of arc erosion mechanism and the search for the main factors that determine the arc erosion process is of great practical significance to the design of electrical and electronic products, not only to provide a basis for the reasonable selection of electrical contact materials to improve the life and reliability of electrical contacts, but also to provide technical support and theoretical basis for the development of new electrical contact materials.
So far, a lot of research work has been carried out at home and abroad on the arc erosion process, and four types of arc erosion mechanisms (dissolution precipitation effect of Ag/Ni system electrical contacts [4], porous sponge effect of Ag/C system electrical contacts [5], skeleton effect of Ag/W system electrical contacts [6], and kinetic property effect of Ag/MeO system electrical contacts [7]) and various arc erosion models have been proposed (such as erosion models based on the number of operations and arc energy tests [8] short-circuit arc enthalpy change erosion model [9], erosion model based on microscopic particle motion [10] inductive circuit arc erosion model [11], one-dimensional high-current arc erosion model [12], three-dimensional contact heating arc erosion model [13] and sputtering erosion model [14], etc.). In the study of numerical simulation of arc erosion, the earliest research conducted abroad was Robertson [15], Nied et al [16], and in recent years Swingler [17] Borkowski [18] established an image-only model of arc action. In China, mainly Xi’an Jiaotong University, Huazhong University of Science and Technology, Central South University, Kunming University of Technology and Beijing University of Posts and Telecommunications are engaged in this area of research. Wang Qiping and Rong Mingzhe of Xi’an Jiaotong University used the finite difference method to solve the temperature field generated by Joule heat of contact resistance, and the calculated results were in good agreement with the experimental results [19]; Wu Xiexiu of University of Science and Technology used the finite element method for calculation and analysis, and established a better model of arc action [20]
Because the arc erosion of electric contact material is the result of multi-process, multi-variable and multi-physical field coupling, the existing arc erosion model can explain the arc erosion law under specific conditions well, but there are still some limitations, such as the one-dimensional high-current arc erosion model considers the heating effect of the arc on the electric contact, but does not consider the effect of the force on the electric contact; the short-circuit arc enthalpy change erosion model can reveal the thermodynamic properties of the electrical contact material, but not for spattering erosion or partial evaporation erosion; and the three-dimensional electrical contact heating arc erosion model calculates only the melting amount of the electrical contact material rather than the spattering amount. It is well known that the most direct effect of arc erosion on the electric contact forest material is to make the electric contact material surface structure and electrical contact physical phenomenon changes, and the electric contact material surface structure and electrical contact physical phenomenon changes will in turn react to the subsequent arc erosion and electrical contact physical phenomenon. Therefore, the arc erosion simulation test is used to study the interaction between the electrical contact physical phenomena, surface structure and arc erosion of electrical contacts, and to analyze the nature of the arc erosion process, which will be beneficial to establish a more consistent arc erosion model with the actual arc action. The arc erosion models in the literature [9~20] are based on numerical simulation modeling, although the arc erosion model based on the number of operations and arc energy test is based on the arc erosion test modeling, but only gives the relationship between the number of operations and arc energy and the amount of arc erosion, and does not consider the relationship between the influence of arc erosion and the surface structure of the electrical contact material and the characteristics of the arc melt pool, and so far has not been found based on the So far, no arc erosion mechanism model based on the surface structure and arc melt pool characteristics of the electrical contact material has been found.
In addition, the arc erosion mechanism of the existing silver metal oxide (Ag/MeO) system electrical contacts is mainly reflected in two aspects: first, the decomposition and sublimation of the metal oxide (Me) consumes a large amount of arc energy to cool the silver matrix, which reduces the arc erosion; second, because MeO is suspended in the form of particles on the surface, it increases the viscosity of the liquid metal and increases the interfacial wettability between silver and MeO, which reduces the loss caused by liquid metal spattering. losses caused by liquid metal sputtering. It can be seen that the existing arc erosion mechanism is mainly established based on the interaction relationship between MeO phase and liquid silver, and fails to elaborate the interaction relationship between arc erosion and the surface structure of the contact material. Therefore, the systematic study and analysis of the arc erosion mechanism of silver-based electrical contact materials from the number of operations, electrical contact material system, electrical contact material components, electrical contact material preparation process, etc. will be a research work with important theoretical value and practical application.

 

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