Splashing Characteristics of Microparticles From Electrode Erosion for Copper, Molybdenum, and Tungsten-Copper

Microparticles from electrode erosion would lead field distortion, microdischarge, or impact damage, which are convinced to be mainly responsible for degradation of insulation performance in switches. To investigate the splashing characteristics of microparticles from electrode erosion, this paper performs the discharge experiments between two cylinder electrodes, made of copper, molybdenum, or tungsten-copper. A statistical method based on laser confocal microscopy is introduced to visualize the distribution of microparticles on the electrode surface. Experimental results indicate that the number of microparticles increases and the acceleration tendency gets mild as the discharge shots accumulate. The Cu surface would lead more production of the
$> 2~\mu \text{m}$
microparticles than other two materials after hundreds of shots, which would provide an explanation for its relative poor reliability and insulation performance. The electrode surface has formed two distinct zones for distribution of these microparticles: inner zone and outer zone after hundreds of discharge shots. Estimation of inner zone radius and splashing angles of microparticles indicates that the larger the microparticles are, the smaller the angle they would be splashed out with. Finally, the evolution of arc column in the first quarter discharge cycle is captured by a high-speed camera and its relation with the concentration of microparticles is discussed.