An Opening Displacement Curve Characteristic Determined by High-Current Anode Phenomena of a Vacuum Interrupter

Abstract

A vacuum interrupter reaches its interruption limit once high-current anode phenomena occur. In order to increase the interrupting capability of vacuum interrupters, extensive research work has been done which included consideration on the contact geometry, contact material, and magnetic field in order to avoid the formation of high-current anode phenomena. However, an opening displacement curve characteristic of a movable contact should be another contributor to the formation of high-current anode phenomena. The objective of this paper is to propose an opening displacement characteristic that is determined by high-current anode phenomena of a vacuum interrupter. Butt-type contacts were used in the test vacuum interrupters and the contact diameters were 12 mm and 25 mm, respectively. The contact materials were microcrystalline CuCr25 and nanocrystalline CuCr25, respectively. Two different opening velocities were tested which were 1.1 m/s and 2.0 m/s, respectively. In the tests, the arcing time was adjusted from ~ 1 ms to 10 ms at each velocity. Test results showed that each type of vacuum interrupter has its own anode discharge diagram which is irrespective of the opening velocities. Based on each anode discharge diagram, an opening displacement curve can be proposed in order to avoid the regions of an intense arc mode and an anode spot mode. With the proposed opening displacement curve, high-current anode phenomena have less of an impact on the arcing period, which is expected to improve the interrupting performance of the vacuum interrupter.