Modelling of arc-gas flow interaction in magnet blast switching devices

摘要

With respect to the switching arc in low voltage circuit breakers the arc-gas flow interaction between straight arc runners densely enclosed by lateral walls in an external magnetic field was investigated theoretically. A mathematical model was developed for predicting the arc motion and the gas flow parameters, such as pressure, density, and temperature. Plausible assumptions allowed simplifications of the fundamental differential equations for electrical potential, mass, momentum, and energy. The arc model accounts for the interaction between arc and cold gas, making use of an analogy to a bubble rising in a liquid filled tube known as a slug flow. Based on this model the mathematical effort, as well as the computational effort, are significantly less compared to a numerical procedure for solving the basic differential equations, e.g. by a finite volume method. Despite the relative simplicity of the arc model, good agreement between the predictions and the experimental data was obtained. Thus the model has a high potential for becoming a valuable tool for developing low voltage circuit breakers.