High-Speed Visualization of Evaporation Phenomena from Tungsten Based Electrode in Multi-Phase AC Arc

A multi-phase AC arc has been developed for applications in various fields of engineering because it possesses unique advantages such as high energy efficiency. However, understanding of fundamental phenomena in the multi-phase AC arc is still insufficient for practical use. Purpose of this study is to investigate electrode erosion mechanism by high-speed visualization of the electrode metal vapor in the arc. Results indicated that the electrode mainly evaporated at anodic period, leading to the arc constriction. Moreover, evaporation of W electrode with 2wt{\%} La$_{\mathrm{2}}$O$_{\mathrm{3}}$ at the anodic period was much higher than that with 2wt{\%} ThO$_{\mathrm{2}}$. This can be explained by different properties of these oxide additives. Evaporation of the oxide additive resulted in the arc constriction, which accelerated the evaporation of W electrode. Therefore, addition of La$_{\mathrm{2}}$O$_{\mathrm{3}}$ with lower melting and boiling point than ThO$_{\mathrm{2}}$ lead to stronger arc constriction, resulting in severer evaporation of W electrode.