Influence of supply and load circuit parameters on the chopping phenomena of vacuum interrupters

Vacuum interrupters are the state of the art technology for breaking short-circuit currents and load currents in medium-voltage systems. Consequently, further applications may be established for vacuum switchgear technology. For each new application, the characteristics of vacuum interrupters have to be observed. One of these is current chopping that results in high overvoltages when switching off inductive loads. It is well known from literature that this behavior is strongly dependent on the contact material of the interrupter contacts. For example, copper-chromium has been established for the most circuit breaker applications in medium and high voltage levels. To compare the different materials and their properties, a test circuit is necessary which helps to measure the chopping current strictly according to the test circuit parameters. In this research project, it was possible to show that the measured chopping currents are influenced by inductivities and capacities both in the load and in the supply circuit. This result is of high importance for the interpretation of phenomena in practical applications. Also, the impact of the supply voltage level was investigated to validate the measurements that were performed at lower voltages.