| 摘要 |
PROBLEM TO BE SOLVED: To prevent a hinge structure from being damaged even when large amount of current such as short-circuit current blows by providing one end of an auxiliary cover with an engagement tongue piece formed so as to engage with a case inner wall surface near a hinge portion when the auxiliary cover is fixed. SOLUTION: When large amount of current such as short-circuit current flows, arc A generates between contacts by repulsing and separating a movable contact 40 from a fixed contact 31. This arc A rapidly expands gas around it to fill with the gas as arc gas in a breaker. Part of this arc gas is ejected from a discharge hole, but the arc gas in the breaker moves in the B and C directions and pressures P1, P2 arc to an auxiliary cover 25. As a result, a bearing portion 31 is pressed up via a pin 30, and the pressure in the P2 direction acts to an engagement tongue piece 25c and the inner wall surface 22b of a main cover 22. Therefore, because a large surface of the engagement tongue piece 25c can hold the auxiliary cover 25 without relying on only the bearing portion 31, it is available even when the large amount of current flows.
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