Testing of a 50 kA, 50 kV current interrupter with I2t preheating and long recovery voltage

The Confinement Physics Research Facility (CPRF) is a reversed field pinch (RFP) plasma experiment. An inductive energy transfer system using a 50-kA, 50-kV DC current interrupter is being utilized for initiating the plasma current. The performance requirements had yet to be realized in a reliable switching system, so development of this current-interrupter system was initiated. A switch test bay with a 50-kA battery bank has been built to test the interrupter in conditions which will exist in the CPRF experiment. Many switch parameters were measured to provide information on the current-interrupting characteristics and reliability. Some of these diagnostics include voltage, current, pre- and post-I²t contact resistance, opening speed and position, arc voltage, and stem temperature. To determine any long-term changes, all shots and data channels are computer indexed and may be easily recalled for review. Extensive testing was performed on Siemens D-10 vacuum interrupters. Test parameter space included 55 kA, 40 kV (per bottle); di/dt of 2250 A/μs, I² t of 5×10⁹ A²; and 20-kV, 500-ms RC recovery decay. Circuit parameters affect opening reliability. Circuit data and the associated testing results are presented along with long-term trends of switch performance under normal conditions