RAIL ARCS: INTERACTION OF MAGNETIC AND FLUID DYNAMIC FORCES.

The motion of arcs driven along rail electrodes is predicted by balancing the driving magnetic force and the resisting fluid dynamic force. High-current (2 to 14 kA) arcs in ambient-pressure air are driven along enclosed copper rails by the self-induced magnetic field. Arc velocities and pressures along the travel length are obtained with sensors mounted in the side wall. The use of wave diagrams for non-steady flow demonstrates that the arc velocity can change abruptly. Future arc motion studies must define parameters such as travel length, channel inlet and exit conditions. The application of wave analysis can similarly predict the arc motion existing in circuit breakers and advantageously affect design changes of electrode and flow configurations accordingly.