The impact of capacitive switching condition on vacuum breakdown phenomena

In the case of switching capacitive loads, breakdown electric field of vacuum interrupter tends to decrease because contacts of vacuum interrupter are damaged by large making current. In this paper, the authors investigated the decreased breakdown electric field from the following two viewpoints. First, the relation between breakdown electric field and condition of opening operation was investigated. The breakdown electric field was invariant regardless of whether mechanical impact of opening operation was applied. On the other hand, the breakdown electric field tended to increase when opening operation was carried out with long arc time. These results indicate that the field emission mainly determine the breakdown phenomena. Secondly, the relation between breakdown electric field and making current was investigated. On the whole, the larger the amplitude of making current became, the lower breakdown electric field tended to be. However, the breakdown electric field was exceptionally high when the generation time of making current arc was long. This is because arc of making current diffused rapidly.