An Improved Black-Box Model for Low-Current AC Arcs in Vacuum Interrupters

The miniaturization and cost reduction of vacuum interrupters have gradually led to their increased utilization in power systems, particularly for low-current breaking. However, such applications are hampered in part by the lack of an accurate black-box model for low-current ac vacuum arcs. In this article, a two-stage black-box model is established according to the characteristics of the arc structure and morphology. Specifically, the vacuum arc is spatially divided into the near-electrode region and interelectrode plasma region, while its temporal evolution is divided into the expansion stage and extinction stage. Meanwhile, the effects of variations in physical factors such as arc length, density, and diameter on the arc conductance are accounted for. Furthermore, sophisticated experiments on low-current vacuum arc drawing have been carried out utilizing a 50 Hz ac power supply and a demountable vacuum chamber. The materials studied for the contacts include CuCr45 and WCu20. Direct comparisons between the experimental and simulated results under various arc conditions verify the correctness and generalization ability of the developed model.