Simulation of Switching Arcs Under Transverse Magnetic Fields for DC Interruption

The importance of low-voltage devices to interrupt dc currents under load and fault conditions has been considerably growing recently. From experimental work, it is known that arcs in strong transverse magnetic fields are able to generate arc voltages high enough to interrupt such circuits. To study the mechanisms behind this process, 2-D simulations of the plasma fluid flow in arc chambers, coupled with current flow and magnetic field, were carried out with a Multiphysics FEM program. For arc chambers, where the arc is pressed against a wall, it could be shown that the power removal that determines directly the arc voltage per unit length occurs predominantly by convection in the J × B force field (electromagnetic pump). In this sense, hydrogen is much more effective than air. In a similar way, this mechanism can also explain the effect of strong magnetic blow fields in arcs with free environment.