Arc erosion characteristics of DC contactor contacts

Abstract

The arc is generated upon contact breaking-off resulting in surface erosion in the terminals and affecting the performance of electrical contact. As there is no natural zero crossing point in the DC power supply system, the erosion caused by arcs is often more severe in DC contactors than that in AC contactors. The arc erosion effect on the contact terminals is analyzed in this paper. Based on the theory of magnetohydrodynamics, a dynamic coupling model of arc and contact terminals considering energy coupling is established. Then, the impacts of the electric current level and breaking speed on the arc erosion in contact terminals are studied by using the model. Simulation results show that the arc temperature near the anode is higher than that near the cathode. It can be noted that the arc temperature and arcing time rise significantly by increasing the current from 20 A to 30 A, which improves the arcing energy by 75.93% and thus worsening the contact erosion. Simulation results also indicate that increasing the breaking-off speed from 0.1 m/s to 0.2 m/s, results in an increase of voltage and current variation rates, an reduction of the arcing time and molten pool volume, a decrease of the arcing energy by 47.83%, and an reduction of the impact of arc erosion on the contact terminal. The experimental results are consistent with the simulations confirming the accuracy of the simulation model.

Keywords

• dc contactor
• magnetohydrodynamic
• arc erosion
• dynamic process
• current rating
• breaking speed