KR200382138Y1 - A Mould Cased Circuit Breaker - Google Patents

Abstract

The present invention discloses a current-limiting trip device for a circuit breaker. Disclosed is a current-type fixed contactor, a movable contactor which is movable to a position in contact with or separated from the fixed contactor, and includes a plurality of single-pole blocking units provided for each phase of the circuit; and a movable contactor in the single-pole blocking unit. An opening / closing mechanism for driving the to the contact or disconnection position; A trip bar rotatably installed at an upper position of the single pole blocking unit to operate the opening and closing mechanism in a trip position; A plurality of shafts provided for each of the single pole blocking units, the shafts rotatably supporting the movable contactors, and rotatable to a position of on, off or trip according to the driving of the opening / closing mechanism, wherein the movable contacts are on, off or Driveable by the shaft during tripping and independently rotatable regardless of the shaft during current-limiting operation; A circuit breaker having a shaft pin which is commonly driven to be connected to the plurality of shafts in order to simultaneously drive the plurality of shafts according to the driving of the opening / closing mechanism, the circuit breaker being rotatable with the movable contact of the single pole blocking unit. A current-limiting trip pin connected to the movable contactor and capable of relative rotation with respect to the shaft that is stopped in the current-limiting operation according to the rotation of the movable contactor, and capable of rotating together with the shaft when on, off or tripping; The shaft pin has one end portion rotatably coupled to the shaft pin with the rotational center axis, and a lever portion extending from the one end portion and rotatable about the shaft pin. The shaft pin is turned on, off or tripped. A first lever which is rotatable with the shaft by the lever, and the lever part is pressed by the current-limiting trip pin to rotate relative to the shaft which stops during the current-limiting operation; A second lever mounted on a rotation path of the first lever that rotates relative to the shaft that stops in the current-limiting operation, and pressed by the first lever that rotates in the current-limiting operation to rotate; It is installed on the rotation path of the second lever that rotates during the current-limiting operation, and is located at a position where one end receives the rotational force from the second lever and the trip bar to press the trip bar during the current-limiting operation. And a third lever having the other end for driving.

According to the present invention, the current-limiting trip pin is assembled to move together in the movable contact by using the movement according to the current-limiting motion of the shaft lever pin assembled to the shaft having the current-limiting structure assembled inside the single-pole blocking unit when the current flows; The first lever pressurized by the current-limit trip pin, the second lever pressurized by the first lever, and the third lever pressurized by the second lever and the trip bar pressurized by the second lever are interlocked. By tripping the switchgear to trip the circuit breaker to keep the movable contactor separated from the fixed contactor, the tripping time of the circuit breaker can be shortened to improve the breaking performance and prevent fusion between the contacts. .

Description

Circuit Breaker {A Mold Cased Circuit Breaker}

The present invention relates to a circuit breaker, and more particularly, to a circuit breaker having a current-limiting trip mechanism that trips a circuit in a short time when an accident current flows on the circuit.

In general, a circuit breaker is an electrical device that protects a circuit and a load by automatically cutting off a circuit in the event of an electrical overload or a short circuit or ground fault current.

As shown in FIG. 1, the conventional circuit breaker includes a magnetic core that protects a mechanism and a magnetic core that is assembled inside the enclosure 1 and generates an electromagnetic force in proportion to the amount of current flowing into the circuit breaker. (5), an armature (6) drawn by the magnetic core (5) due to the electromagnetic force from the magnetic core (5) when a large current flows, and a crossbar (7) driven by the driving of the armature (6) , The trip shooter 8 driven by the crossbar 7, the spring 9 causing the driving force of the trip shooter 8, and the trip bar 4 which trips the opening and closing mechanism by rotating by the trip shooter 8. It is configured to include.

In the conventional circuit breaker, when the normal current flows, as shown in FIG. 2A, the trip shooter 8 is constrained by the crossbar 7 so that the trip bar 4 maintains the reset position, but when a large current flows. As shown in 2b, the electromagnetic force of the magnetic core 5 attracts the armature 6 so that a part of the armature 6 is constrained by the crossbar 7 by rotating the crossbar 7. The restraint is released by releasing the engaging portion of the) and the trip shooter 8 rotated by the elastic force of the assembled spring 9 rotates the trip bar 4 so that the trip bar 4 is out of the reset position. Tripped.

However, since the current-limiting tripping device of the conventional circuit breaker trips the mechanism through multiple stages of operation when a short circuit current flows, a large amount of breaking energy is generated due to time delay, and fusion between the movable contact and the stator contact is prevented. There is a problem that can occur and eventually burn out the circuit and load.

Therefore, the present invention has been devised to solve all the problems of the prior art, the object of the present invention is to improve the breaking performance by shortening the trip time of the circuit breaker, and tripping the opening and closing mechanism immediately when the current-limiting operation occurs It is to provide a circuit breaker that can prevent the fusion between the contacts by making it.

An object of the present invention is to include a current-limiting fixed contactor, a movable contactor which is movable to a position contacting or separating the fixed contactor, a plurality of single pole blocking units provided for each phase of the circuit;

An opening / closing mechanism for driving the movable contact in the single pole blocking unit to the contact or disconnection position;

A trip bar rotatably installed at an upper position of the single pole blocking unit to operate the opening and closing mechanism in a trip position;

A plurality of shafts provided for each of the single pole blocking units, the shafts rotatably supporting the movable contactors, and rotatable to a position of on, off or trip according to the driving of the opening / closing mechanism, wherein the movable contacts are on, off or Driveable by the shaft during tripping and independently rotatable regardless of the shaft during current-limiting operation;

In the circuit breaker having a shaft pin that is commonly connected to drive the plurality of shafts in order to drive the plurality of shafts simultaneously in accordance with the drive of the opening and closing mechanism,

It is connected to the movable contactor so as to be rotatable together with the movable contactor of the single pole blocking unit, and can be rotated relative to the shaft which stops during the current-limiting operation in accordance with the rotation of the movable contactor. A current-limiting trip pin that is rotatable with the shaft;

The shaft pin has one end portion rotatably coupled to the shaft pin with the rotational center axis, and a lever portion extending from the one end portion and rotatable about the shaft pin. The shaft pin is turned on, off or tripped. A first lever which is rotatable with the shaft by the lever, and the lever part is pressed by the current-limiting trip pin to rotate relative to the shaft which stops during the current-limiting operation;

A second lever mounted on a rotation path of the first lever that rotates relative to the shaft that stops in the current-limiting operation, and pressed by the first lever that rotates in the current-limiting operation to rotate;

It is installed on the rotation path of the second lever that rotates during the current-limiting operation, and is located at a position where one end receives the rotational force from the second lever and the trip bar to press the trip bar during the current-limiting operation. It can be achieved by providing a circuit breaker according to the present invention, characterized in that it comprises a third lever having the other end to drive.

The object of the present invention and the configuration of the means for achieving the same will be understood more clearly by the following detailed description of the preferred embodiment of the present invention with reference to the drawings.

Figure 3 is a view showing the main portion of the circuit breaker according to an embodiment of the present invention, Figure 3a is a perspective view, Figure 3b is a front sectional view, Figure 3c is an excerpt perspective view of the shaft portion.

Referring to Figure 3, the circuit breaker according to an embodiment of the present invention, the current-type fixed contactor 11, and the movable contactor (10) which is movable in contact with or separated from the fixed contactor 11, A plurality of single pole blocking units (2) provided for each phase of the circuit; An opening / closing mechanism (3) for driving the movable contactor (10) in the single pole blocking unit (2) to the contact or disconnection position; A trip bar 4 rotatably installed at an upper position of the single pole blocking unit 2 to operate the opening and closing mechanism 3 in the trip position; A plurality of shafts 10a provided in each of the single pole blocking units 2 and rotatably supporting the movable contactor 10, and rotatable to the on, off or trip position according to the driving of the opening and closing mechanism 3; Wherein the movable contactor 10 can be driven by the shaft 10a when on, off or trip and independently rotates independently of the shaft 10a during the current-limiting operation; In the circuit breaker for wiring provided with the shaft pin 12 which is drive-connected in common with the several shaft 10a, in order to drive several shaft 10a simultaneously by the opening / closing mechanism 3,

It is connected to the movable contactor 10 so as to be rotatable together with the movable contactor 10 of the single pole blocking unit 2, and rotates relative to the shaft 10a which stops during the current-limiting operation in accordance with the rotation of the movable contactor 10. A current-limiting trip pin 13 which is rotatable with the shaft 10a when it is on, off or tripped; One end coupled to the shaft pin 12 to be rotatable with the shaft pin 12 as the center of rotation, and a lever part extending from the one end to be rotatable about the shaft pin 12, on, off or It is possible to rotate together with the shaft 10a by the shaft pin 12 at the time of trip, and the lever part is pressed and rotated by the current-limit trip pin 13 relative to the shaft 10a which is stopped during the current-limiting operation. A first lever 14; A second lever that is provided on a rotation path of the first lever 14 that rotates relative to the shaft 10a that stops in the current-limiting operation, and is pressed and rotated by the first lever 14 that rotates in the current-limiting operation. 15; It is installed on the rotation path of the second lever 15 that rotates during the current-limiting operation, and is located at a position where the trip bar 4 can be brought into contact with one end portion receiving the rotational force from the second lever 15. It further comprises a third lever 16 which has the other end which rotates and drives the sea trip bar 4 further.

As shown in FIG. 3B, the current-limiting fixed contactors 11 are two fixed contactors respectively provided at the power supply side or the load side, and each end thereof is a terminal portion to which an electrical line on the power supply side or the load side is connected, and the other end portion thereof. The contact is attached and the other end to which the contact is attached is composed of a substantially "U" shaped conductive material member bent toward the terminal portion. Therefore, since the direction of the current flowing into the movable contactor 10 through the fixed contactor 11 on the power supply side and the direction of the current flowing out to the fixed contactor 11 on the load side through the movable contactor 10 are reversed, a short circuit current or ground fault When a large fault current such as a current occurs on the circuit, an electromagnetic repulsive force is generated between the movable contactor 10 and the current-limiting fixed contact 11, so that the movable contactor 10 is a current-limiting fixed contact 11. Rotate as shown in Figure 3b in a direction to separate from). This is called the current-limiting motion.

The movable contactor 10 is a double contact type movable contactor having contacts attached to both ends thereof.

The single-pole breaking unit 2 is provided for each phase of the circuit (line) between the power supply and the load where the circuit breaker is installed in a manner that three circuit breakers are provided, for example, when the circuit breaker is used for a three-phase AC line. Except for some external exposed ends, such as the terminal portion of the fixed contact 11, the outside is manufactured to be sealed with an insulating material case.

The opening and closing mechanism 3 drives the movable contactor 10 in the single pole blocking unit 2 to the position of the contact or disconnection on the upper part of the central main pole blocking unit 2 of the plurality of single pole blocking units 2. It is provided in order to provide a user with an unsigned handle for manually operating the circuit breaker in the on, off position, and is installed between the handle and the shaft (10a) to drive the driving force of the handle or the elastic driving force of the trip spring shaft ( 10a) has an unsigned upper and lower links, a link shaft connecting upper and lower links, one end supported by the link shaft and the other end supported by the handle, and the elastic energy is stored in the on state. The tripping spring which prevails the stored elastic energy at the time of tripping, and is coaxially connected with the link axis, and can be rotated by the preserving elastic energy of the trip spring at the time of tripping. It consists of a latch (latch) and the like, the position of which is constrained by the tch holder, and the detailed configuration and illustration of the opening and closing mechanism of such a configuration are already well known and thus omitted.

When the trip bar 4 further describes the process of operating the opening and closing mechanism 3 in the trip position, when the trip bar 4 rotates, the latch holder is rotated through an intermediate power transmission member called a nail, for example. Therefore, the latch is released, thereby restoring the elastic energy from the state in which the trip spring is compressed (tensioned state) (returning to a reduced original state), and rotating the link by folding the linking elastic energy by the shaft 10a. The circuit breaks the circuit by disconnecting the movable contactor 10 from the fixed contactor 11, which is called a tripping operation, which is distinguished from an off operation, which is a passive circuit blocking by a handle.

The movable contactor 10 can be driven by the shaft 10a when it is on, off or trips because the movable contactor 10 is supported by the shaft 10a, but is independent of the shaft 10a during the current-limiting operation. The independent rotation is possible because the shaft 10a has both openings opened to both end portions to which the contact of the movable contactor 10 is attached, thereby allowing independent rotation during the current-limiting operation of the movable contactor 10. Therefore, during the current-limiting operation, the shaft 10a does not move because there is no power from the link, whereas the movable contactor 10 is within the predetermined opening angle range of both openings by the electromagnetic repulsive force with the fixed contactor 11. Rotate clockwise at.

Two shaft pins 12 are commonly connected to drive through a plurality of shafts 10a in common, and one of the shaft pins 12 is drive-connected to an unsigned lower link of the opening / closing mechanism 3. Therefore, as the opening / closing mechanism 3 provided in the upper part of the main circuit single pole blocking unit 2 of the single pole blocking unit 2 is driven to an on, off or trip position, Since the shaft 10a is driven in common, the movable contactor 10 in the other end special blocking unit 2 is also driven to an off or trip position separated from the on or fixed contactor 11 contacting the fixed contactor 11.

In the configuration in which the current-limiting trip pin 13 is connected to the movable contactor 10 so as to be rotatable together with the movable contactor 10 of the single-pole breaking unit 2, a preferred embodiment configuration will be described below.

One or two springs, not shown, called contact springs, are provided on one side of the movable contactor 10 for the purpose of strengthening the contact pressure between the contacts at the on-contact position of the movable contactor 10 and the fixed contactor 11. Is provided in the shaft (10a), one end of the contact spring is supported by a first spring support pin (not shown) fixed to the movable contactor 10 and the upper and lower outer peripheral surface of the movable contactor 10 or the wall surface or shaft of the shaft (10a) It rides on the outer circumferential surface of the pin support member separately installed between the 10a and the movable contactor 10 and is supported by the second unsupported spring support pin which can be rotated together with the movable contactor 10. The first spring support pin and the second spring support pin may be connected to each other by an unsigned link. In order to accelerate the opening speed of the movable contactor 10 during the current-limiting operation and to prevent the moving contactor 10 from returning to the fixed contactor 11 again, the upper and lower outer peripheral surfaces of the movable contactor 10 or the wall surface of the shaft 10a or the like. The outer circumferential surface of the pin support member separately installed between the shaft 10a and the movable contactor 10 includes a plurality of cam surface portions in which the groove portion and the center point are opposite to each other. According to a preferred embodiment, the current-limiting trip pin 13 of the present invention extends from the lower one of the second spring support pins to protrude to the outside of the shaft 10a.

 Therefore, since the movable contactor 10 is supported on the shaft 10a and the current-limiting trip pin 13 is connected to the movable contactor 10 through a link with a first spring pin fixed to the movable contactor 10. When the shaft 10a rotates to the on, off or trip position at the time of on, off or trip, the current-limit trip pin 13 also rotates together. However, the current-limiting operation rotates only the movable contactor 10 independently and relatively with respect to the shaft 10a that is stopped independently of the shaft 10a. At this time, the current-limiting trip pin 13 is directed to the stationary shaft 10a. It rotates with the movable contactor 10.

The first lever 14 is a substantially one-shaped member, one end of which is fitted to another shaft pin 12 other than the shaft pin 12 of the two shaft pins 12 to which the lower link is connected, and thus the other shaft. One end portion is rotatably coupled to the shaft pin 12 with the pin 12 as the center of rotation, and a lever portion extending from the one end portion and rotatable about the shaft pin 12. Accordingly, the first lever 14 is rotatable with the shaft 10a by the shaft pin 12 when it is turned on, off or tripped, and the current-limiting trip pin is relatively relative to the shaft 10a which stops during the current-limiting operation. The lever unit is pressed to rotate by (13).

The second lever 15 is a substantially "L" shaped member, the center portion of which is supported by a rotating shaft supported by the opening and closing mechanism, and the first lever that rotates relative to the shaft 10a that stops during the current-limiting operation. A pillar portion which is installed on the rotation path of 14) and is pressed by the first lever 14 to rotate during the current-limiting operation, and extends integrally from the one pillar portion in a substantially perpendicular direction, so that the rotation force of the pillar portion To another third lever 16.

The third lever 16 is also an approximately "L" shaped member, the center portion of which is supported by a rotating shaft supported at an upper position of the outer wall of the single pole blocking unit 2, and the second lever 15 which rotates during the current-limiting operation. At one end of the columnar shape which is installed on the rotation path of the second lever 15 and receives the rotational force from the second lever 15, and extends integrally from the one end in a substantially perpendicular direction to contact the trip bar 4. It is positioned and has the other end to rotate the drive by pressing the trip bar (4) during the current-limiting operation. The other end of the third lever 16 is also a columnar lever part, but a portion of the other end of the third lever 16 that contacts the trip bar 4 is close to the trip bar 4 and the trip bar 4 is closed. It has a shape bent toward the trip bar (4) to reduce the stroke (stroke) that can be rotated.

Meanwhile, the operation of the circuit breaker according to the present invention configured as described above will be described with reference to the accompanying drawings.

4 is a diagram illustrating an operation state of a current-limiting trip device of a circuit breaker according to an embodiment of the present invention, and FIG. 4A is a state diagram during ON operation when a steady current flows, and FIG. 4B is turned off when a steady current flows. OFF) is a state diagram at the time of operation, and FIG. 4C is a state diagram when the current-limiting current flows.

If the user grips the handle to connect the circuit as shown in Fig. 4A in the off position for disconnecting the circuit between the power supply and the load, the circuit breaker according to the present invention shown in Fig. 4B is operated in the on position on the left side of the drawing. The shaft 10a is connected by the upper link connected to the handle included in the opening / closing mechanism 3 together with the handle, and the lower link to which the upper part is connected to the shaft pin 12 of the shaft 10a. It rotates counterclockwise by a predetermined angle from the off-position as shown in the right side view of FIG. At this time, as the counterclockwise predetermined angle of the shaft 10a rotates, the movable contactor 10 supported by the shaft 10a also rotates by the same angle in the same direction. Therefore, the current-limiting trip pin 13 connected to the movable contact 10 to rotate together also rotates by the same angle in the same direction. Therefore, considering that the shaft pin 12 is rotated by the same angle in the same direction and the shaft 10a is rotated, the shaft pin 12 and the current-limit trip pin 13 rotate together by the same angle in the same direction. The first lever 14 supported by the shaft pin 12 also rotates in the same direction as the current-limiting trip pin 13. Rotational pressure of the current-limiting trip pin 13 prevents the first lever 14 from rotating in the clockwise direction about the shaft pin 12 where it is stopped. Accordingly, the second lever 15 is also shown in FIG. 4B. From the state of the left side of FIG. 4A to the state of the left side of FIG. 4A, without stopping, the third lever 16 also stops without displacement from the state of the left side of FIG. 4B to the state of the left side of FIG. 4A. Since the trip bar 4 does not rotate.

On the other hand, if the user in the on state of Figure 4a to move the handle to the right of the off position as shown in Figure 4b to block the circuit, the upper link and the upper link connected to the handle included in the opening and closing mechanism (3) with the handle The lower link is connected to the shaft pin 12 of the shaft 10a, the upper portion of which is rotated by a predetermined angle clockwise from the on position as shown in the right side of FIG. 4B. It will be in a state as shown in the drawing. At this time, the movable contact 10 supported by the shaft 10a also rotates by the same angle in the same direction as the clockwise predetermined angle of the shaft 10a rotates. Therefore, the current-limiting trip pin 13 connected to the movable contact 10 to rotate together also rotates by the same angle in the same direction. Therefore, considering that the shaft pin 12 is rotated by the same angle in the same direction and the shaft 10a is rotated, the shaft pin 12 and the current-limit trip pin 13 rotate together by the same angle in the same direction. The first lever 14 supported by the shaft pin 12 also rotates in the same direction as the current-limiting trip pin 13. Rotational pressure of the current-limiting trip pin 13 prevents the first lever 14 from rotating in the clockwise direction about the shaft pin 12 where it is stopped. Accordingly, the second lever 15 is also shown in FIG. 4A. From the state of the left side of FIG. 4B to the state of the left side of FIG. 4B, it stops without displacement, and the 3rd lever 16 also stops without displacement from the state of the left side of FIG. 4A to the state of the left side of FIG. Since the trip bar 4 does not rotate.

On the other hand, if an accident current such as a short circuit current occurs on the circuit while the circuit is connected, an electromagnetic repulsion force is generated between the movable contactor 10 and the fixed contactor 11 in the single-pole breaking unit 2 in the fault current generation phase. Therefore, the movable contactor 10 rotates in the direction in which the movable contactor 10 is separated from the fixed contactor 11 without imposing an external artificial operating force, that is, clockwise in FIG. 4C. At this time, since the shaft 10a has no driving force due to the link, the shaft 10a maintains the on position. At this time, the current-limiting trip pin 13, which is connected to rotate with the movable contactor 10, also rotates clockwise with the movable contactor 10, and thus the first lever 14 supported by the shaft pin 12 that is stopped. The pillar portion is pressed by the current-limiting trip pin 13 and rotates clockwise around the shaft pin 12. The rotating first lever 14 also presses the second lever 15 disposed on the rotation path to rotate clockwise, so that the second lever 15 presses the third lever 16 to 3 The lever 16 rotates counterclockwise while its other end presses the trip bar 4 to rotate. Then, the nail is rotated by the rotating trip bar 4, and the latch holder rotates accordingly to release the latch, so that the spring spring pulls the link shaft upward by precipitating the elastic force, and thus the upper link and the lower link are pulled. The shaft pin 12 and the shaft 10a are rotated in the clockwise direction in the drawing while pulling the shaft pin 12 connected to the lower link while the movable contact 10 and the fixed contact 11 are completely separated. The trip state is maintained. At this time, the handle is also located in the center position as shown in FIG. 4C. Since the single pole blocking units 2 of the other poles are commonly connected to each other through the shaft pins 12, the movable contactor 10 and the fixed contactor 11 in the single pole blocking units 2 of the other poles at the same time. The circuit between the power supply and the load where the fault current has been separated is completely disconnected. This trip state is returned to the trip state as long as the fault current flows in the circuit even if the user turns the handle on again. If the cause of the fault current is removed and the handle is turned on again, the user maintains the connected state of the circuit unless the user operates the handle to turn it off or the fault current on the circuit occurs again. do.

On the other hand, the present invention has been described with reference to the embodiment shown in the drawings, but this is only an example, those skilled in the art will understand that various modifications and equivalent embodiments are possible from this. However, the true technical protection scope of the present invention should be defined only in the appended utility model registration claims.

As described above, the circuit breaker according to the present invention is a current-limiting trip pin assembled to move together with the movable contactor by using the movement according to the current-limiting motion of the movable contactor assembled inside the single-pole breaking unit when an accident current flows. The opening and closing mechanism is interlocked by interlocking a first lever pressurized by a pin, a second lever pressurized by a first lever, a third lever pressurized by a second lever, and a trip bar pressurized by a second lever. The circuit breaker is tripped to maintain the position of the movable contactor separated from the fixed contact by tripping the circuit breaker, thereby shortening the trip time of the circuit breaker, improving the breaking performance, and immediately tripping the opening / closing mechanism when a current-limiting action occurs. It is effective to prevent liver fusion.

1 is a view showing a conventional circuit breaker, FIG. 1A is a front view thereof, and FIG. 1B is a perspective view of a main portion thereof.

FIG. 2 is a diagram illustrating an operation state of a main part of a conventional circuit breaker, and FIG. 2A is a diagram of main parts in an on state when a normal current flows, and FIG. 2B is a diagram of main parts in a state where an accident current flows and trips.

Figure 3 is a view showing the main portion of the circuit breaker according to an embodiment of the present invention, Figure 3a is a perspective view, Figure 3b is a front sectional view, Figure 3c is an excerpt perspective view of the shaft portion.

4 is a diagram illustrating a main operation state of a circuit breaker according to an exemplary embodiment of the present invention, and FIG. 4A is a state diagram during an ON operation when a steady current flows, and FIG. 4B is an OFF operation when a steady current flows. It is a state diagram of a time, and FIG. 4C is a principal state diagram of a state where an accident current flowed and tripped.

<Description of the symbols for the main parts of the drawings>

2: single pole blocking unit 3: mechanism

4: trip bar 10: movable contactor

10a: shaft 11: fixed contactor

12: shaft pin 13: Hallyu trip pin

14: first lever 15: second lever

16: third lever

Claims (1)

A plurality of single pole blocking units each having a current-limiting fixed contactor and a movable contactor movable in contact with or separated from the fixed contactor and provided for each phase of the circuit; An opening / closing mechanism for driving the movable contact in the single pole blocking unit to the contact or disconnection position; A trip bar rotatably installed at an upper position of the single pole blocking unit to operate the opening and closing mechanism in a trip position; A plurality of shafts provided for each of the single pole blocking units, the shafts rotatably supporting the movable contactors, and rotatable to a position of on, off or trip according to the driving of the opening / closing mechanism, wherein the movable contacts are on, off or Driveable by the shaft during tripping and independently rotatable regardless of the shaft during current-limiting operation; In the circuit breaker having a shaft pin that is commonly connected to drive the plurality of shafts in order to drive the plurality of shafts simultaneously in accordance with the drive of the opening and closing mechanism, It is connected to the movable contactor so as to be rotatable together with the movable contactor of the single pole blocking unit, and can be rotated relative to the shaft which stops during the current-limiting operation in accordance with the rotation of the movable contactor. A current-limiting trip pin that is rotatable with the shaft; The shaft pin has one end portion rotatably coupled to the shaft pin with the rotational center axis, and a lever portion extending from the one end portion and rotatable about the shaft pin. The shaft pin is turned on, off or tripped. A first lever which is rotatable with the shaft by the lever, and the lever part is pressed by the current-limiting trip pin to rotate relative to the shaft which stops during the current-limiting operation; A second lever mounted on a rotation path of the first lever that rotates relative to the shaft that stops in the current-limiting operation, and pressed by the first lever that rotates in the current-limiting operation to rotate; It is installed on the rotation path of the second lever that rotates during the current-limiting operation, and is located at a position where one end receives the rotational force from the second lever and the trip bar to press the trip bar during the current-limiting operation. And a third lever having the other end for driving.