Experimental Investigation on Anode Spots and Anode Plumes in High-Current Vacuum Arc Under Different Contact Materials

The objective of this article is to investigate the effect of contact material on the formation and transition of high-current anode spots and anode plumes. A series of experiments are carried out in a demountable vacuum chamber at three current levels of 3, 4, and 6.5 kA. Plate contacts made of CuCr30 and CuCr40 with a diameter of 10 mm are adopted. Arc images are captured by a high-speed camera and synchronized with measurements of the arc current and voltage. The experimental results show that the three typical anode discharge modes, namely footpoint, anode spot type 1, and anode spot type 2, are formed at a smaller gap distance as the experimental current increases, and this tendency is independent of the contact material. The arc voltage is higher and the anode spot appears earlier and lasts longer under the CuCr40 contact than under the CuCr30 contact. As a result, the footpoint is formed at a smaller gap distance, whereas anode spot type 2 is formed at a larger gap distance. As a special anode discharge mode, an anode plume usually occurs between anode spot type 2 and arc current zero in various shapes at different locations on the anode surface. The anode plume of the CuCr40 contact appears at a larger gap distance and the corresponding threshold current and accumulated arc energy are also larger. Due to a stronger anode activity, the anode plume lasts a longer time under the CuCr40 contact than under the CuCr30 contact.