Study on the erosion characteristics of copper-carbon electrode pairs by DC air arc

Abstract

As common electric contact materials, copper-carbon electrode pairs are widely used in the field of electric contact such as in high-speed railways, motor collector rings and grounding brushes. They play a key role in energy transmission in the above-mentioned systems. Arc erosion has become a key issue threatening system safety. In this work, a dedicated arc erosion platform was built to study the polarity effect of copper-carbon electrode pairs. It was found that arc dynamics and electrodes erosion behaviours were significantly different under different polarities, which could be understood from the mechanism of heat transfer, cooling and electron emission of the electrode. Then, when the carbon material was used as an anode, the arc caused carbon transfer: the carbon material sublimated quickly due to electron condensation and thermal conduction and quickly condensed on the low-temperature metal electrode, while the carbon material transfer could partly inhibit the oxidation of the cathode metal electrode. In addition, the rapid sublimation of the carbon material produced high-temperature airflow, which would make the arc impedance fluctuate and cause the arc voltage to jump. Finally, the anode heat transfer and cathode cooling mechanism directly affected the material state, and the erosion of the anode material was more serious.