... coal mine contains explosive gas (methane) mixture, as main switch or branch switch in the power supply system, with the frequency of ... .3 The vacuum circuit breaker is mainly composed of vacuum switch tubes, operating mechanism, protection plug-ins and other components, ... -ins.3. Main technical characteristica)Rated working voltage;1140 (660)V,660(380)Vb)Rated working current;200,400Ac)Rated working ...