Abstract: A circuit breaker having the overcurrent tripping characteristic, which is capable of detecting an overcurrent flowing through main circuit between an ac source and a load. The circuit breaker comprises a pre-alarm circuit having a pre-alarm characteristic, a pre-alarm signal output circuit for producing an alarm in response to the output of the pre-alarm circuit and a photocoupler for controlling the data transmission between the circuits. The circuit breaker can detect the main circuit current before it becomes an overcurrent and generate the alarm accurately.

Abstract: A multi-pole circuit interrupter comprising an electrically insulating housing having two side walls and at least two partition walls defining therebetween a central compartment and at least two side compartments. A central pole unit is disposed within the central compartment and a side pole unit is disposed within each of two side compartments. Each of the units includes a stationary contact element, a movable contact arm, an arc extinguisher and terminals for the external connection. The distance between a center line passing through the centers of the stationary contact element, the movable contact arm and the arc extinguisher of each of the pole units is smaller than the distance between the center lines passing through the terminals of each pole unit, so that the thickness of the housing side wall can be increased without increasing the overall width dimension of the housing.

Abstract: In a circuit breaker having electromagnetic tripping device (55), thermal tripping device (56,57), and adjusting device (59-64), the adjusting device (59-64) is disposed above the thermal tripping device (56,57) in perpendicular direction to power source side-load side direction, and the adjusting device (59-64) has an arm (69) for transmitting adjusting actions from an adjusting dial (24) to a movable iron core (55a) of the electromagnetic tripping device (55), and such constitution enables to shorten a configuration in the power source side-load side direction, and enables to compensate loose-assembly or deformations of the adjusting device (59-64), and thereby initial setting for the adjusting device (59-64) becomes correct.

Abstract: A circuit interrupter comprises, in a housing, a movable contact assembly having a movable contact carrier and a contact arm supporting the movable contact carrier, and a cross bar secured to the movable contact assembly for allowing the movable contact assembly to rotate thereabout. The circuit interrupter also comprises a bearing assembly secured to the housing for rotatably supporting the cross bar, and the bearing assembly has a stop surface capable of being engaged by the movable contact assembly for determining the OFF position of the movable contact assembly.

Abstract: A circuit interrupter comprises a toggle link having an upper toggle link and a lower toggle link pivotally connected by a knee pin to each other, a movable contact arm having a movable contact element secured thereon and connected to the lower toggle link of the toggle link, and a toggle link stopper capable of contacting the upper toggle link for preventing the bouncing back of the movable contact arm during tripping of the movable contact arm. The toggle link stopper is provided with a first stop surface which is brought into engagement with the upper toggle link when the movable contact arm is being tripped open and a second stop surface which is brought into engagement with the upper toggle link at a position closer to the knee pin than to the first stop surface when the movable contact arm is bouncing back. Thus, the toggle link is engaged by two stop surfaces at two stages, enabling the preventing of the bouncing of the movable contact arm.

Abstract: A circuit interrupter comprising a stationary contact assembly having a stationary contact element securely attached to a stationary conductor, and a movable contact assembly having a movable contact element secured on a movable contact arm and operable in response to an overcurrent between ON and OFF positions relative to the stationary contact assembly. An arc runner is attached to the stationary conductor by a single rivet and includes an elongated main body extending along the stationary conductor for expanding an electric arc generated between the movable and the stationary contact elements upon current interruption. The circuit interrupter further comprises a pair of tabs mounted to the arc runner for defining a pair of sloped engagement surfaces for receiving and positioning therebetween the stationary conductor when the stationary contact assembly is assembled.

Abstract: To prevent a separation arc from migrating along the movable contact arm 12 of a circuit breaker and welding its biasing spring 14, the arm is protected by an insulating shield 22 underlying its lower face, flanking its sides, and having outwardly extending tabs 22c underlying the spring halves.