| 摘要 |
<p>Electric switching device comprises two fixed contacts (1, 2) and one movable contact (3), forming together the main contact system, which is located in an oil-insulated cavity (13) enclosed in a housing (10). In its direction of movement, the movable contact has an extension in the form of a shaft (14). The shaft is formed with a hydraulic piston by which the movable contact is operated. The hydraulic piston is surrounded by a cavity in which a piston cavity (15, 16) is formed on each side of the hydraulic piston. The piston cavities are oil-filled. The movement of the shaft is determined by an electrically controlled directional valve (21). The directional valve receives signals as to whether the electric switching device is to be opened or closed. At a given signal, the directional valve distributes a high pressure to the piston cavity that is to be enlarged. The electric switching device can be provided with an auxiliary contact mechanism which can be placed either in the fixed contacts and/or in the movable contact. The electric switching device may be provided with a bistability mechanism comprising wedge pistons (45, 46) biased by means of springs (47, 49), said wedge pistons, in case of a pressure drop, locking the movable contact in the existing position via the shaft. <IMAGE></p> |
