| 摘要 |
A minimum-fluid circuit-breaker includes a quenching chamber in which the fixed and movable contacts are located, a pump of the piston-cylinder type, the piston being rigidly connected to the movable contact and serving to force arc-quenching fluid from the pump cylinder into a pressure chamber and thence from the latter through non-return valving into the quenching chamber to facilitate arc extinction as the contacts disengage. The rate-of-flow of the arc quenching fluid into the quenching chamber is varied during movement of the pump piston. By utilizing a row of bypass ports in the pump cylinder which are progressively cut out by the piston during its movement in the contact opening direction, the flow rate is progressively increased. By utilizing a double concentric pump piston arrangement both pistons act conjointly on the fluid during the initial part of the piston movement to provide a high flow rate while thereafter only the smaller of the two pistons is effective thus providing a correspondingly lower flow rate. When the contacts reclose, the pressure chamber and pump cylinder refill with fresh fluid from a reservoir. |
