Test circuit for switching behavior analysis of a model vacuum switch for DC applications

While vacuum circuit breakers are state-of-the-art at medium-voltage AC level, they are also focus of current research projects for DC circuit breakers. To get a deeper understanding of the change in switching behavior of a vacuum interrupter between AC and DC interruption, a test setup that simulates a DC interruption is necessary. Simultaneously, it is impossible to investigate the high current plasma of a commercially available vacuum interrupter optically due to the ceramic housing. A model vacuum switch, on the other hand, has viewing ports that allow optical measurements of the high current plasma that forms during switching attempts. Additionally, magnetic as well as electrical analysis of the vacuum arc during current interruption are still possible like they are with the commercially available vacuum interrupters. Thus, a model vacuum switch is implemented in a test setup for switching behavior analysis. Furthermore, to extend the inherent capability as zero-crossing switch to DC applications the model vacuum switch is coupled with a resonance circuit. Superimposing the high DC current that needs to be interrupted with an oscillating current from a resonance circuit generates an artificial zero current crossing in the primary current path. Hence, allowing the model vacuum switch to interrupt a DC load. This interruption capability is strongly dependent on the rate of change of the current at zero crossing. Which is why current interruption attempts must be performed with oscillating currents of different frequencies. This work presents the experimental test setup of a model vacuum switch integrated in a test circuit with variable rate of change of the oscillating current.