High-Current Vacuum Arc Phenomena of Nanocrystalline CuCr25 Contact Material

Copper-chromium contact material is widely used in vacuum interrupters. In recent years, the nanocrystalline CuCr contact material has presented some excellent performances in high withstand voltage, low chopping current, and so on. Therefore, it has a big potential for high-current interruption with vacuum interrupters. The objective of this paper is to investigate the high-current vacuum arc phenomena of a nanocrystalline CuCr25 (Cr 25 wt%) contact material. Vacuum interrupters with 12- and 25-mm-diameter butt-type contacts were used in the tests. The vacuum interrupters were designed in a glass envelope without main shield for vacuum arc observation by a high-speed charge-coupled device camera. The test vacuum interrupters were operated by a permanent-magnet mechanism. The opening velocities were 1.1 and 2.0 m/s, respectively. The arc current frequency was 50 Hz, and the arcing time was nearly 10 ms. For comparison, vacuum interrupters with microcrystalline CuCr25 contact material were also prepared. The experimental results showed that both the arc energy and the mean value of the arc voltage of the nanocrystalline CuCr25 contact material were lower than those of the microcrystalline one under the same experimental conditions. The carrying current per cathode spot of the nanocrystalline contact material (about 34 +/- 10 A) is about one-third of that of the microcrystalline one (about 107 +/- 30 A). However, the diameters of the anode spots of the nanocrystalline CuCr25 contact material were significantly larger than those of the microcrystalline CuCr25 contact material under the same conditions. Moreover, the durations of the anode spots of the nanocrystalline CuCr25 contact material were longer than those of the microcrystalline one.