VSG-12 vacuum circuit breaker is an indoor power distribution device in a three-phase AC system with a rated voltage of 12kV and 50Hz. As a protection and control unit for power equipment, industrial and mining enterprises, it is suitable for various natures switching loads and frequent operation, multiple breaking short-circuit currents. The vacuum circuit breaker uses a new operating mechanism and embedded pole (the vacuum interrupter and main electric circuit parts enclosed into a whole), to protect the vacuum interrupter from the effects of collision, dust and condensation, environment adaptable, greatly reduces the operation maintenance cost, realize the product free maintenance, operation mechanism less maintenance. Unibody design, operating mechanism and circuit breaker ontology through the type test, with E2 level electrical life, 2 level mechanical life can be used as the fixed unit installation, also can match feed mechanism, form a handcart unit, fixed type circuit breaker can increase the corresponding interlocking, to meet the requirements of match XGN2, GG1A fixed switchgear.