| 摘要 |
<p>Medium-voltage circuit-breaker comprising a leaktight insulating envelope (1) filled with a gas with good dielectric properties, a semi-fixed arc contact (3) connected electrically to a first current intake (2) and a moving contact (10) connected to an operating mechanism and connected up electrically to a second current intake (11), characterised in that the semi-fixed arc contact (3) is linked to a piston (4) which can move in a blast volume (VI) delimited in particular by the inner wall of an insulating cylinder (8) inside the said envelope and a first face (7A) of a blast nozzle (7), the said piston being thrust by a spring (9) kept taut when the circuit-breaker is in the engaged position, the said circuit-breaker comprising a thermal expansion volume (V2) delimited in particular by the inner wall of the said insulating cylinder (8), a second face (7B) of the nozzle and a transverse partition (11) through which the moving contact (10) slides, means being provided so that when a high-intensity current is cut, the piston (4), after having accomplished its travel in the direction of compression of the blast volume (V1), cannot move in the opposite direction.
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