Numerical simulation of arc splitting process in a LV switching device considering thermo-field emission mechanism

The need for simulation of arc dynamics in a low voltage switching device has been widely felt in the industry. The movement of the arc plasma in the 3D model is governed by venting and magneto-hydrodynamic interaction. A Coupled Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) solver approach is adopted to enhance the accuracy of the solutions. The Arc root effect is modeled using a thin shell layer having non-linear voltage resistance characteristics. Lookup tables for arc root voltages are created as a function of the surface temperature of electrode and adjacent plasma temperatures considering the thermo-field emission mechanism and are integrated with the global CFD solution. The effect of secondary electron emission has been accounted for. The arc splitting phenomenon is modeled for a single splitter plate and extended for multiple splitter plates. Integrating arc root physics helps in understanding the arc root formation, arc bending and lengthening, and subsequent root movement along the splitter plates. Presence of multiple splitter plates also produces blockage to the gas flow which further modifies the arc parameters. The study helped in understanding the effect of splitter plate configurations on arc behavior.