Abstract
Contact resistance of the main circuit is an important parameter for measuring the performance and reliability of relay products. The contact resistance value interacts with the stress and temperature of the contact surface during the relay's operation, and it will change with the ambient temperature and load current. Therefore, it is difficult to calculate the contact resistance when the relay is in the working environment. However, the finite element model used to predict contact resistance in previous studies does not consider the effect of current and temperature on the contact surface stress at the microscopic level. In this paper, based on the fractal theory, we established three-dimensional electrical contact finite element models in micrometer-scale and nano-scale to solve the contradiction between the computational efficiency and accuracy of the finite element model containing fractal surfaces. In the microscopic electrical contact model, the multi-physics coupling process of electric-temperature-stress at the conductive spot is analyzed, to improve the accuracy of the calculation of the local contact resistance at the conductive spot. Through the data transfer between the macroscopic finite element temperature rise model of the relay and the microscopic electrical contact model, the temperature rise and contact resistance of the relay under different load currents are calculated more accurately. The feasibility of the simulation method is proved by comparison with experimental measurement results.
Highlights
The relay is a commonly used switching device, and its main circuit contact resistance is an important parameter
This paper presents a multi-scale and multi-physics calculation method of contact resistance by using a fractal function to establish three-dimensional micro-scale finite element models of irregular contact surfaces and combining with a macro-scale model of relay temperature rise
By comparison with experimental measurements, it can be seen that the calculation error of the contact resistance calculation method proposed in this paper is within an acceptable range and has certain application value
Summary
The relay is a commonly used switching device, and its main circuit contact resistance is an important parameter. R. Li et al.: Multi-Physics Finite Element Model of Relay Contact Resistance and Temperature Rise and plastic deformation during the contact process of micro convex spots, and the concept of plastic index was introduced [1], [2]. L. Pei et al Established a three-dimensional finite element model of the fractal surface to analyze the relationship between the actual contact area and the load [10]. The contact resistance of the relay contacts under different load currents is calculated through the data exchange between the micro electrical contact model and the macro relay temperature rise finite element model. After repeatedly measuring the contact surface contours at different sampling positions and calculating by the structure function method, the fractal parameter is D = 2.3, G = 1.28 × 10−9m. The main purpose of establishing the macroscopic temperature rise model of the relay is to calculate the temperature field of the relay and the temperature Tu of the contact surface of contacts when the relay works until the temperature rise reaches a steady state
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