Abstract: A molded case houses switching parts and includes a case main body and a cover placed on an upper portion of the case main body. The case main body includes a bottom portion case that forms a bottom portion of a circuit breaker and an intermediate case, placed on an upper portion of the bottom portion case, having a dividing wall that blocks off a space between the intermediate case and the bottom portion case. A power source side terminal block and second movable contact are fitted inside the bottom portion case, and a first movable contact, the load side terminal block, the contact portion, and the arc extinguishing chamber are fitted inside the intermediate case.

Abstract: A molded case housing each part is configured of a case main body (54) and a cover (55) placed on an upper portion of the case main body, the case main body (54) is configured of a bottom portion case (56) that forms a bottom portion of a circuit breaker and an intermediate case (57), placed on an upper portion of the bottom portion case, having a dividing wall that blocks off a space between the intermediate case and the bottom portion case. A power source side terminal block (3) and second movable contact (4) are fitted inside the bottom portion case, and a first movable contact (5), the load side terminal block (9), the contact portion (52), and the arc extinguishing chamber (6) are fitted inside the intermediate case.

Abstract: A circuit breaker includes a main case containing a contactor section, an arc-extinguishing device and an overcurrent tripping device; a middle cover laid on the main case, the middle cover having in a central section thereof a recess partitioned with a bottom wall for containing a switching mechanism and at least one interior attachment; and a top cover covering the top side of the recess in the middle cover. The main case, the middle cover and the top cover are arranged to be dividable from one another. The middle cover has an auxiliary cover, covering the switching mechanism, and the auxiliary cover has the top cover mounted thereon.