Abstract: In a make-and-break mechanism for use in a circuit breaker, an alarm output plate 56, which is disposed so as to be slidable in the vertical direction along the frame (cover plate) 27 of the make-and-break mechanism, is secured to the engaging projection 27d of the cover plate 27 through a pair of right and left guide holes 57 formed therein. At the same time, one end of a handle spring 59, which, in the trip operation, is used to rotate an operation handle 26 to a trip display position, is caught on the alarm output plate 56.

Abstract: A switching mechanism for a circuit breaker includes a frame; a latch rotatably supported on the frame; a holder rotatably supported on the frame and having a movable contact; a handle lever rockably supported on the frame by lever shafts; a toggle link formed of first and second links rotationally connected by a toggle shaft; and a switching spring. A free end of the first link is rotatably connected to the latch, and a free end of the second link is rotatably connected to the holder. The first and second links generally overlap each other to reduce the movement range of the toggle link to miniaturize a switching mechanism. The switching spring is situated between the toggle shaft and the handle lever at a side opposite to a switching handle with respect to the lever shaft.

Abstract: A circuit breaker includes a current path for first and second contacts connected in series in an insulative container. When an overcurrent occurs by over load, the second contact is opened based on a command from a time delay trip portion of an overcurrent trip device. When a short-circuit current occurs, the first and second contacts are opened based on a command from an instantaneous trip portion of the overcurrent trip device. Since the first and second contacts are contained in a common container, the wiring works between the first contact and the second contact is unnecessary. Since the first and second contacts are opened in the instantaneous trip, interruption of a high short-circuit current is facilitated.

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 overcurrent trip device includes a capacitor 13 that stores power for driving a trip electromagnet 7, and a charging current generating means 18 that starts charging the capacitor 13 upon detection of an overcurrent and that completes the charging of the capacitor 13 until a trip control circuit 5 outputs a trip signal. The operation of the trip electromagnet 7, which is driven with the charges of the capacitor 13 by causing a thyristor 12 to be turned on by the trip signal, is continued until the charges of the capacitor 13 are lost, and even after the power supply from a rectifying circuit 4 is stopped due to the opening of a circuit breaker 8, it is made impossible to reset and re-close the circuit breaker 8 for a predetermined time.