| 摘要 |
PROBLEM TO BE SOLVED: To improve a circuit breaker so as to be able to alleviate the abnormal wear of contacts by moving an arcing point of a movable contact from its surface to the tip side of a movable contactor with high interrupting performance secured by effectively exerting a narrow-gap effect by a narrow-gap arc-extinguishing plate, by suppressing an excessive internal pressure rise by lowering a total volume of thermal decomposition gas generated at current interruption, and by a tactful use of a gas flow of the thermal decomposition gas. SOLUTION: In the circuit breaker with a pair of narrow-gap arc-extinguishing plates 9 formed of insulating materials arranged at right and left sides of fixed and movable contacts along a pole-opening movement path of a rotating movable contactor 3 paired with a fixed contactor 2, and with a narrow-gap arc-extinguishing space formed between opposed wall faces, the narrow-gap arc-extinguishing plates are arranged along the whole length of the pole-opening movement path, and at the same time, with the narrow-gap arc-extinguishing space between the opposed wall faces divided into an area near the fixed contact and an open-pole side area ahead of it, the narrow-gap interval in the area near the fixed contact is set narrow, a lateral stepped part 9a and a longitudinal stepped part 9b are formed on a plate face at the open-pole side area, and a narrow-gap-enlarged face 3c is formed at a narrow-gap interval enlarged at a surface area ahead of the movable contact 3a. COPYRIGHT: (C)2008,JPO&INPIT
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