Effect of a magnetically blown arc on cumulative electrical erosion of contacts

Abstract

Cumulative electrical erosion during repeated interruption is a key factor limiting the service lifetime of low-voltage direct current switching devices. In this work, the cumulative erosion behavior of air-switch contacts under magnetically blown arcs was investigated through experiments and numerical simulations. The effects of arc-root migration on molten-pool evolution, surface morphology, and the erosion resistance of Cu–Ni contacts were analyzed. An arc erosion experimental platform was established to perform repeated interruption tests under different magnetic flux densities, and a dynamic cumulative erosion model with a moving heat source was developed. The results show that the transverse magnetic field drives directional arc migration through the Lorentz force, resulting in continuous heating in the leading region and rapid solidification in the trailing region of the contact molten pool. This leads to significant asymmetries in the flow characteristics, force states, and splashing behavior of the molten metal. Compared with stationary heat-source erosion, the crater depth decreases by 25.8%, while the width increases by 12.5%, exhibiting an overall ‘bowl-shaped’ morphology. After repeated interruptions, the initial crater and resolidified layer modify the local thermal boundary conditions, promoting molten-pool spreading, which results in increases in crater width and depth by approximately 12% and 13.2%, respectively. Meanwhile, groove and step-like accumulated structures gradually form along the magnetic blow direction, further aggravating local electrical erosion. Simulations of Cu–Ni contacts indicate that 10% Ni content effectively reduces crater dimensions and improves erosion resistance, whereas 30% Ni content causes heat localization, leading to an 86% increase in crater depth and deterioration of erosion resistance. These findings provide a theoretical basis for lifetime prediction, structural optimization, and material selection of air-switch contacts.