Modelling evaporating metal droplets in ablation controlled electric arcs

A complete set of equations is proposed to model droplets of molten metal ejected from the contacts in a high voltage circuit breaker of the SF₆ filled gas-blast type. The initial speed and diameter of the droplets are varied to characterize their behaviour and study the distribution of the metal vapour. A relation is derived that can be used in simplified arc models such as integral or two-zone models to take the effect of the droplets into account. It is found that, although the influence on usually measured quantities such as pressure and voltage is small, droplets affect velocity and temperature fields in the electric arc significantly and should not be neglected.