The Effect of Contact Material on Particles Behavior in High-Current Vacuum Arcs

Micro particles produced by high-current vacuum arcs significantly reduce the insulation performance of vacuum interrupters. The objective of this paper is to observe the effect of contact materials on the behavior of micro particles during the arcing and post-arcing period, and to reveal possible reason for the late breakdown triggered by them. A plasma diagnosis system based on laser-shadow technique was established to measure the particles in a demountable vacuum chamber. The results illustrate that the patterns of particles generation have significant difference due to the contact materials. CuCr10 contacts tended to present obvious flowing liquid metal on the surface, forming protrusions on it which became to be particles source. On the contrary, CuCr50 contacts scarcely produced obvious molten clumps and particles were ejected directly from erosion area the electrode surface, furthermore, particles ejection could sometimes be restrained by the arc pressure. Moreover, the residual particles after the current zero between the electrode gap dramatically decreased the insulation performance and played a significant role in the re-ignition. A delayed breakdown could be initiated by the micro particle existed several milliseconds after arc extinction.