Multi-Physics Finite Element Model of Relay Contact Resistance and Temperature Rise Considering Multi-Scale and 3D Fractal Surface

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.