Better interpretation of vacuum interruptor tests

In this article, we step through the development process, from fundamental investigations of the arc-contact interaction to performance and precertification testing of manufactured vacuum interrupters (VI). We also describe how VI models are tested above their arc-contact interaction to performance and rated current to monitor the quality of their materials and processing. The present work began with movies of arcs between spiral-type VI contacts, which generate a radial magnetic field to drive the high-current arc column along the spiral arms. The end-of-life condition of identical contacts and shields from manufactured VIs tested repeatedly under the corresponding conditions, was also systematically studied, along with the arc voltage traces. From the integration of these experimental results, guidelines have been developed for using the arc voltage waveforms of spiral-contact VIs to determine when in a high power arcing cycle the arc is stationary, moving, breaking up, diffuse or causing melting of the arc-contacts. In particular, anchoring of a high-current arc, and the resultant intense localized heating of the contacts, can increase the probability of long VI arcing times. Inspection of arc voltage traces is thus a method to monitor for contact damage and reduced internal performance during testing. The results are applicable to analysis of arc voltages and contact travel records from breaker certification tests