A device for joining a bimetal strip and a component that acts as a support for the bimetal strip in a current breaking unit, the bimetal strip being electrically connected by a free end, to a input connection area, and by another end, by way of which the bimetal strip is fixed to the support, to a output connection area. The bimetal strip is mounted to pass through the support to be fixed at different locations along the length of the bimetal strip, the bimetal strip having a first part and a second part that are situated respectively on one side and the other of the support, the first part being on the side of the free end, corresponding to the usable surface of the bimetal strip, the length of the usable surface being variable depending on the insertion length of the bimetal strip in the support, the insertion length being determined depending on the calibre of the unit to obtain a constant thermal profile, regardless of the calibre, and to an electrical protection unit with same.

Disclosed is a molded case circuit breaker including a case configured to accommodate an element for trip, an upper cover detachable attached to the case, a dial configured to include a fixing plate, which is provided to protrude along an outer circumference surface thereof, and a first stopper disposed under the fixing plate, a crossbar moved by the dial, a first dial fitting hole provided in the upper cover for the dial to be fitted into the first dial fitting hole, and a dial rotation adjusting unit provided in the first dial fitting hole and fitted between the fixing plate and the first stopper to guide a rotation of the dial, the dial rotation adjusting unit including a plurality of fitting grooves arranged at certain intervals. The first stopper is fitted into and fixed to the plurality of fitting grooves according to the rotation of the dial.

A device for joining a bimetal strip and a component that acts as a support for the bimetal strip in a current breaking unit, the bimetal strip being electrically connected by a free end, to a input connection area, and by another end, by way of which the bimetal strip is fixed to the support, to a output connection area. The bimetal strip is mounted to pass through the support to be fixed at different locations along the length of the bimetal strip, the bimetal strip having a first part and a second part that are situated respectively on one side and the other of the support, the first part being on the side of the free end, corresponding to the usable surface of the bimetal strip, the length of the usable surface being variable depending on the insertion length of the bimetal strip in the support, the insertion length being determined depending on the calibre of the unit to obtain a constant thermal profile, regardless of the calibre, and to an electrical protection unit with same.

A trip device for a circuit breaker comprises a first terminal; a second terminal; and a bimetal in which a slot with one side opened is formed at one end of the bimetal, the one end is divided into a first end portion and a second end portion, the first end portion is connected to the first terminal, and the second end portion is connected to the second terminal, wherein the bimetal generates heat with a current which flows between the first end portion and the second end portion, and a heating amount of the bimetal is changed based on a length of the slot. Accordingly, a desired rated current can be set, the bimetal can be prevented from being damaged by a fault current, and the fault current can be effectively detected by obtaining a sufficient amount of heat and a bending amount of the bimetal.