Pneumatically operated switch - uses pressurised gas to extinguish arc and has parallel circuit containing resistor switched in before engagement

摘要

The pneumatically operated switch uses pressurised gas to extinguish arcing, and has a fixed cylinder and a mobile piston. An isolating nozzle, in which is mounted one contact piece, is situated in the cylinder. A corresponding contact piece is mounted on the mobile piston, and includes a ratchet mechanism which is released on activation of the switch, so that the moving contact is driven by a spring towards its resilient end stop. A parallel auxiliary resistance may be introduced by the circuit breaker 8 to 10 milliseconds before the engagement, and it remains in circuit until the release of the switch, at which point both auxiliary and main contacts break simultaneously.