Low Surge Vacuum Circuit Breakers

Low surge vacuum circuit breakers were developed which used a new electrode material cobalt-silver-selenium alloy. Their chopping current level was below 1.0 A and their high frequency current interruption ability was about 24 Aús. These levels were much lower than those of conventional electrode materials and did not change after load current interruption lifetime and short circuit current interruption tests. From switching tests with motors and no-load transformers, safe operation of these vacuum circuit breakers, without any surge absorber, was confirmed ; the surge level caused by current chopping and the multiple reignition surge level caused by high frequency current interruption were far below the apparatus insulation levels. Furthermore, the new material showed good interruption ability.