Interaction between arc root stagnation-transition and contact erosion during direct current air circuit breaker interruption

The contact erosion during the arc duration affects the attachment position of arc roots, directly determining the arc motion speed. In this paper, a two-way coupling model is proposed to study the interaction between contact edge erosion and arc root stagnation-transition during direct current air arc interruption. A two-dimensional transient model for contact erosion and droplet splashing is established using an improved level-set method, combined with the magnetohydrodynamic model of arc plasma and contact energy transfer, considering the mass transfer, heat transfer, and fluid flow during the arc root stagnation-transition comprehensively. The model's accuracy is verified through experiments. The results show that the arc root stagnation forms molten pool or even droplet splashing. Vortices below the moving contact interfere favorably with arc root transition. However, contact deformation induced by erosion affects heat dissipation at the arc root, weakens the vortices' aerodynamic performance, hastens vortex bubble rupture, and delays arc root transition. Increasing breaking speed and arc-blowing magnetic induction intensity shortens stagnation time and reduces edge erosion. However, the breaking speed more than 5 m/s or the magnetic induction intensity more than 50 mT shows no significant improvement on the arc root transition speed, while erosion intensifies when magnetic induction intensity exceeds 50 mT.