Simulation on dwell stage of arcs in bridge type contacts for high-voltage DC relay

Bridge-type contacts co-operated with permanent magnet are widely used in 270V/200A DC power relays. The permanent magnet helps to drive the arc out of contact gaps as soon as possible, and also helps to bend and quench the arc rapidly. Arc dwell stage is the first stage between arc ignition and the arc root moves out of the gap. This paper is focused on numerical investigation of dwell stage behaviors in bridge-type contacts in a 270V/200A DC power relay. A 2-D nitrogen arc model based on magneto-hydrodynamics theory is built and calculated. Basic dwell stage parameters are described by a set of coupled equations, including Navier-Stokes equation, energy equations and Maxwell equations. By adopting a floating potential, the voltage drop between movable contact and stationary contacts is solved. The detailed dwell stage behaviors are presented and preliminarily discussed according to the calculated temperature and arc current density distributions. Furthermore, experiments are carried out to validate the simulation results. The simulated arc voltage shows good agreement with that of acquired by experiments.