Abstract: A circuit breaker includes a molded case comprised of a case and a cover. Terminal parts to be connected to a power supply and a load are provided respectively at front and rear ends of the molded case. A control mechanism for switching a movable contact is disposed between the front and rear terminal parts. The cover is divided into three parts for covering the control mechanism and the terminal parts disposed at front and rear of the control mechanism, respectively. The front and rear parts of the cover covering the terminal parts are detachably mounted on the molded case as terminal covers.

Abstract: A circuit breaker includes a molded case comprised of a case and a cover. Terminal parts to be connected to a power supply and a load are provided respectively at front and rear ends of the molded case. A control mechanism for switching a movable contact is disposed between the front and rear terminal parts. The cover is divided into three parts for covering the control mechanism and the terminal parts disposed at front and rear of the control mechanism, respectively. The front and rear parts of the cover covering the terminal parts are detachably mounted on the molded case as terminal covers.

Abstract: In a circuit breaker, a power source current transformer (2) comprises: a secondary coil (6) arranged between two legs (1a and 1b) of a U-shaped part of a main circuit conductor (1), and an iron core (7) including an iron core leg (7a) which penetrates the secondary coil, and yokes (7b and 7b) which embrace the two legs (1a and 1b) of the U-shaped part of the main circuit conductor, the power source current transform supporting the current detecting means. As a result, the power source current transformer (2) is arranged compact inside the main circuit conductor (1), and the main circuit current, when flowing in each of the legs (1a and 1b) of the U-shaped part, produces the magnetic flux output acting on the secondary coil. Hence, even if the main circuit current is small, a great power source output can be obtained.

Abstract: An arc quenching device for a circuit breaker having a stationary contact member and a moving contact member includes a magnetic element formed of an arc quenching core and a base plate. The arc quenching core includes a back wall, and two side walls extending from lateral sides of the back wall. The base plate extends substantially perpendicularly from a lower side of the back wall in a direction as in the side walls, and is fixed to the stationary contact member. The base plate includes a U-shaped magnetic driving core situated near a stationary contact point and extending upwardly from the base plate to surround the stationary contact point, and an arc horn integrally formed with the base plate and obliquely extending toward the back wall from a portion near the stationary contact point. Arc formed between the stationary contact member and the moving contact member is moved by magnetic driving force formed by the magnetic driving core to the arc quenching core to be quenched therein through the arc horn.

Abstract: There is disclosed an arc extinction chamber unit for assembly into a multipolar circuit breaker. This chamber unit is composed of arc extinction chambers provided one for each pole, and coupling arms for connecting the chambers to each other. The chambers and coupling arms are molded into one unitary body. Each chamber can contain a generated arc gas pressure, preventing the arc gas pressure being vented to the outer box of the circuit breaker, thereby reducing the stress on the outer box. The arc extinction chamber unit includes restraining arms which connect to the walls of the circuit breaker outer box, further strengthening the box. Each arc extinction chamber contains grooves in the inner wall for easy insertion of grids. The grids are configured with V-shaped indentations. The integral construction of the chamber units and coupling arms provides for assembly into the circuit breaker in a single assembly step.

Abstract: Individual movable contactors of a circuit breaker are made up of a pair of conductors. The first conductor has one end bifurcated to form a pair of legs separated by a slit. At the open end each leg has a curved inner portion the opposed curved portions of the two legs defining a receptor space which is substantially circular in cross section. The second conductor has one end whose cross section is substantially circular and which fits within the receptor space and makes a good slidable contact therewith, and the other end which supports the main contact. Provision is made for rotating the second conductor about its circular end for opening or closing connection to the main contact.