KR20090023015A - Circuit breaker - Google Patents

Abstract

A circuit breaker having high current limiting performance is provided to isolate a magnetic yoke from a contact point by easily assembling a yoke cover in a unit assembly frame of a current blocking part. A magnetic yoke(6) of U shape is arranged in an end part of a first fixed contactor(1) and a second fixed contactor(2). A right side part and a left side part of the magnetic yoke are vertically formed, and surround a fixed contact(1a, 2a). An insulating barrier(8a) and a yoke cover(9) are formed in a unit assembly frame(8). A bottom part of the insulating barrier is upwardly extended between the first fixed contactor and the second fixed contactor. A rear end part of the insulating barrier is extended to an opening moving path region of a movable contactor. The yoke cover is arranged in both sides of the insulating barrier, and covers the right side part and the left side part of the magnetic yoke.

Description

Circuit breaker {CIRCUIT BREAKER}

SUMMARY OF THE INVENTION The present invention is a two-point cutting circuit that cuts off overcurrent by combining two pairs of open / close contacts in series in a current breaker of each pole for a circuit breaker applied to a low voltage distribution circuit. It relates to a circuit breaker, and more particularly, to the unit structure of the current interruption unit.

2. Description of the Related Art A circuit breaker of a two-point cutting method is known in which an overcurrent is blocked by combining two pairs of open / close contacts in series with a current interruption part of each pole (see Patent Document 1, for example).

The current interruption portion of the two-point cut-off circuit breaker is fixed to the first and second fixed contactors which are fixed to the front and rear ends of the two-point cutting circuit breaker, and the movable contact which is folded to the fixed contact at the front end of the U-shaped arm. It is comprised by the rotation type entanglement movable contactor, and the 1st and 2nd fixed contactor separately, and the extinguishing apparatus arrange | positioned in front of the opening movement path of a movable contactor. Next, the two-point cut-off circuit breaker is shown in Fig. 7, and the conventional structure of the current interrupting part is shown in Fig. 8.

First, in FIG. 7, 10 is a main body case of a circuit breaker, 11 is an operation handle, 12 is an opening / closing mechanism part, 13 is a current interruption part, and 14 is an overcurrent external device. Here, the current interruption unit 13 includes a pair of left and right fixed contacts connected to a power supply side and a load side terminal as described later, and a toggle link mechanism (screwed with an opening / closing spring) facing the fixed contactor. ) Is composed of an entanglement-type movable contactor associated with (12) and an arc extinguishing device.

Fig. 8 is a configuration diagram of the above-described current interruption unit 13, in which 1 is a first fixed contact unit integrated with a power supply terminal, 2 is a load side via an operating element of an overcurrent external device 14 (see Fig. 7). The second fixed contact, 1a, 2a, which is connected to the terminal, is a fixed contact fixed to the tip of the fixed contact 1, 2, and 3 is a movable contact that is in contact with the fixed contact 1a, 2a at the tip of the U-shaped arm. Interlock type movable contactor which fixed (3a, 3b), 4 is an arc extinguishing apparatus which corresponded with the fixed contact 1a, 2a individually, and was arrange | positioned in front of the opening movement path of the movable contact 3, and 4a is an arc extinguishing apparatus ( A sub-grid plate arranged at an upper and lower end across the left and right side walls of 4), 5 is a contact holder of the movable contact 3, 5a is its support shaft, and the contact holder 5 Is linked to the opening / closing mechanism part 12 of FIG. In addition, the fixed contactors 1 and 2 and the arc extinguishing device 4 are mounted on a unit assembly frame (made of a molded resin) (not shown) to form a unit, and the unit is mounted on a main body case 1 of a circuit breaker (FIG. 6). Reference). On the other hand, the movable contact 3 is assembled to the main body case of the circuit breaker via the support shaft 5a.

The overcurrent protection operation of the circuit breaker having the above-described configuration is well known, and when an overcurrent (short circuit current, etc.) flows in the distribution path, an electromagnetic repulsive force acts between the fixed contactors 1 and 2 and the movable contactor 3 to move the movable contactor 3. ) Starts to open, and the movable contacts 3a and 3b open from the fixed contacts 1a and 2a. At the same time, the open / close mechanism 12 trips to drive the movable contact 3 toward the open end position.

Moreover, in this opening operation process, as shown in FIG. 9, between the fixed contact 1a, 2a of the 1st, 2nd fixed contact 1, 2, and the movable contact 3a, 3b of the movable contact 3; The two arcs arced in the drawing extend from I to II in the drawing, and are press-fitted into the arc extinguishing device 4 under an electromagnetic driving force. Thus, it is well known that the arc is divided by the grid plate 4a of the arc extinguishing device 4, the arc voltage is increased, the cooling effect is also applied, the arc is extinguished, and the overcurrent is blocked. In addition, since the series two-point cutting method has a high arc voltage (doubled) of the generated arc as compared with the normal one-point cutting method, high current-limiting breaking performance can be obtained.

On the other hand, apart from the circuit breaker of the two-point cutting method described above, as a magnetic drive means for increasing the electromagnetic repulsive force acting on the movable contactor when energizing overcurrent, the movable contactor surrounds the main portion of the contact portion of the fixed contactor ( The circuit breaker of the structure which provided the U-shaped magnetic yoke standing up and extending in the opening direction of 3) is known (for example, refer patent document 2).

With this configuration, when an overcurrent flows to the fixed contact due to a short circuit accident in the converter, magnetic flux is generated in the magnetic yoke, and the magnetic flux acts on the movable contact to increase the electron repelling force. As a result, the opening speed of the movable contact is increased to improve the breaking performance.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-273536

Patent Document 2: Japanese Patent Application Laid-Open No. 6-283090

In the circuit breaker of the two-point cutting method described in Figs. 7 and 8, the magnetic yoke disclosed in Patent Document 2 is combined with the first and second fixed contacts disposed in the current interruption unit, so that the tripping operation is performed. As the initial contact speed of the movable contactor is increased, further improvement of the breaking performance is expected.

Therefore, the inventors have established magnetic yokes on the first and second fixed contacts of the current interruption unit to verify the breaking performance. It turned out that the same subject as a base material arises. That is, in the conventional current interrupter (no magnetic yoke) shown in Fig. 8, in order to configure the circuit breaker compactly and compactly, the first fixed contactor 1 and the second fixed contactor arranged side by side at each pole are arranged. The fixed contact 2 is set to the minimum space | interval which is necessary for ensuring insulation.

In this case, if the insulation distance (space distance, creepage distance) between the 1st fixed contact 1 and the 2nd fixed contact 2 is not fully secured, the opening movement of the movable contact 3 will be performed. On the way, between the first and second fixed contacts flashes over a path having a short insulating distance, and immediately after the start of the opening operation, between the contacts of the fixed contacts 1 and 2 and the contacts of the entanglement movable contact 3. The two arcs which are extended by the call to the electric current flow between the fixed contactors, and are not connected via the movable contactor 3 but between the contacts of the first fixed contactor 1 and the second fixed contactor 2. Is directly connected to the arc. In this state, the arc cannot be driven by the arc extinguishing device 4 to be divided and cooled, and the series two-point cutting function also does not work, so that the predetermined breaking performance cannot be exhibited.

By the way, when the U-shaped magnetic yoke is assembled to the fixed contactor so as to surround the contact portion from side to side with respect to the first and second fixed contactors 1 and 2, the side edges of the magnetic yoke are separated from the side edges of the fixed contactor. Since it extends from side to side, the distance between the fixed contacts 1 and 2 is further narrowed as it is in the conventional structure, and the insulation distance is reduced. As a result, the arc current is easily generated between the fixed contacts. In addition, when a large distance (insulation distance) is set between the fixed contacts 1 and 2 arranged on the left and right to prevent such an arc current, the width dimension occupied by the current interrupting portion of each pole increases, resulting in miniaturization of the circuit breaker. It becomes difficult.

In addition, the magnetic yoke (magnetic material) needs to be insulated and isolated from the fixed contact so that the arcing point of the arc called between the fixed / movable contacts does not current with the magnetic yoke in order to exhibit the function of enhancing the electromagnetic repulsive force. In this regard, the above-described Patent Document 2 forms a concave recessed portion surrounded by an insulating wall in the main body case of the circuit breaker, and accommodates and arranges a magnetic yoke therein to insulate the insulation between the fixed contacts. In addition to the complicated shape of the circuit breaker, the number of assembly circuit breakers also increases, so that an improvement in place of the conventional structure is desired.

In addition, in the two-point cut-off circuit breaker of FIG. 8, with the opening of the movable contact 3, the arc extended between the fixed contacts 1a and 2a and the movable contact 3a and 3b of the entanglement movable contact 3 ( The two arc voltages are applied in series between the fixed contact 1a of the fixed contact 1 and the fixed contact 2a of the fixed contact 2. This arc voltage increases with the elongation of the arc, with the longest arc length near all open positions of the movable contact 3. For this reason, when the arc voltage of the arc which extends between fixed / movable contacts becomes more than the insulation strength between the fixed contacts 1 and 2 arranged to the left and right, between the fixed contacts will be insulated-breakdown, and the 1st fixed contact 1 ) And the contact point of the second fixed contactor 2 are directly connected by an arc, and as a result, there is a problem that the breaking performance of the two-point cut-off circuit breaker cannot be exhibited.

Therefore, in order to prevent the arc current between the fixed contacts as described above, before the arc generated between the fixed and movable contacts extends beyond the arc length necessary for blocking the current limit, the arc is current-limited by the current to the extinguishing device side. There is a need.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object thereof is to provide a circuit breaker in which the unit structure of the current interrupting unit is improved to solve the above problems, to obtain a compact and compact configuration, and to obtain a high current-limiting breaking performance. do.

In order to achieve the above object, according to the present invention, the first and second fixed contactors in which the current interrupting units are arranged in parallel to the left and right and fixed to the front end thereof, and the movable contacts are fixed to the front end of the U-shaped arm. A rotation type entangled movable contactor opposed to the fixed contact, and an arc extinguishing device disposed in front of the opening movement path of the movable contact corresponding to each of the first and second fixed contacts; In the circuit breaker of the two-point cutting method which mounted the to the unit assembly frame made of mold resin,

At the distal end of the first and second fixed contactors, a fixed contact conductor and a fixed contact are enclosed from the left and right, and a U-shaped magnetic yoke in which the side portions stand up in the opening movement direction of the movable contact is disposed, and the unit is assembled with the fixed contact. Mount on the frame. In addition, the unit assembly frame includes an insulating barrier that separates between the first fixed contact and the second fixed contact by splitting between the first fixed contact and the second fixed contact and extending throughout the opening movement path of the movable contact. And a yoke cover of an insulating material disposed on both left and right sides of the insulating barrier to cover the left and right side edge portions of the magnetic yoke provided at the front ends of the first and second fixed contacts (claim 1).

In addition, in the unit structure described above, the yoke cover and the arc extinguishing device are specifically configured in the following state.

(1) The yoke cover is composed of an inverted U-shaped insulating wall covering the region from side to side along the opening movement path of the movable contact, and the front end portions of the left and right side walls are fitted inside the left and right side portions of the magnetic yoke. Then, the front end is connected to the extinguishing device on the inlet side and mounted on the unit assembly frame (claim 2).

Moreover, this yoke cover is comprised from the organic polymer material which receives the heat | fever of the arc which called between the fixed / movable contact points, and elutes ablation gas (claim 3).

(2) On the open end side of the arc extinguishing device, an arc current plate is provided on the left and right arc extinguishing chambers corresponding to the first and second fixed contacts separately (claim 4). The plate forms a pair of left and right arc runners projecting toward the arm tip of the movable contact that has moved to the open end position, and an arc generated between the fixed / movable contacts causes an arc current near all open positions of the movable contact. Allow the plate to current (claim 5).

By the above structure, the effect of the following description can be obtained.

(1) Interlocking type movable contactor which sandwiches the insulation barrier provided in the unit assembly frame, between the 1st, 2nd fixed contactor arranged to the left and right, and the magnetic yoke attached to each fixed contactor, and each fixed contactor. By isolating the opening movement path of the insulated arc, the arc that is fired between the fixed and movable contacts during the overcurrent breaking operation causes the current to move to the fixed contact side during the opening movement of the movable contact, so that the first fixed contact and the second fixed contact are By interfering with the direct arc between the can be secured high insulation strength. Moreover, by providing an insulation barrier, the mutual space | interval of the fixed contacts arrange | positioned at both sides can be set small.

(2) Furthermore, the yoke cover is composed of an inverted U-shaped insulating wall extending upward along the opening movement path of the movable contact, and the lower end of the side wall is inserted into the magnetic yoke, The yoke cover can be simply assembled to the unit assembly frame of the current interrupter to isolate the magnetic yoke from the contacts.

In addition, the yoke cover is made of an organic polymer material that receives arc heat and evaporates the ablation gas, so that the yoke cover functions as a slit-small arc wall at the time of current interruption, further enhancing the current-limiting breaking performance. Can be.

(3) In addition, in the arc extinguishing device corresponding to the 1st and 2nd fixed contactor, the arc current board which spreads to the left and right arc-extinguishing chambers is provided in the opening end side, and the arc which generate | occur | produced between the fixed / movable contacts is moved from a movable contactor. By current flows toward the arc current plate side of the arc extinguishing device, arcs extending between the first and second fixed contacts can be divided into grid current arcs by using the arc current plate as a relay point.

In addition, since the arc current does not flow to the movable contact after the arc current, the amount of wear of the movable contact due to arc arcing can be reduced.

As described above, according to the configuration of the present invention, it is possible to provide a circuit breaker having a totally compact and compact configuration and high breaking performance.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on the Example shown to FIGS. 1-6. 1 is an exploded perspective view showing the assembling unit structure of the current interrupting unit, FIG. 2 is an external view of the unit assembling state, and FIGS. 4A and 4D are a side view, a plan view, a sectional view, and an XX cross-sectional view as seen from an arrow, in a state in which a extinguishing device, a magnetic yoke and a yoke cover are assembled into a unit assembly frame. 5 is a perspective view of arrangement of the first and second fixed contacts and the entanglement movable contacts, FIG. 6 is an operation explanatory diagram showing a process in which an arc extending between the fixed / movable contacts and the current flows to the arc extinguishing device side when the current is interrupted; The same reference numerals are given to members corresponding to FIG. 8, and description thereof is omitted.

First, in Fig. 1, 8 is a unit assembly frame made of mold resin, and the unit assembly frame 8 is provided with the first and second fixed contacts 1 and 2, the arc extinguishing device 4, and the fixed contacts 1, Each component of the magnetic yoke 6 and the yoke cover 9 attached to the contact portion of 2) is mounted, and the unit 7 of the current interruption unit as shown in FIG. 2 is assembled.

Here, the magnetic yoke 6 is formed by bending a magnetic plate in a U shape, and the bottom surface of the fixed contacts 1 and 2 so as to surround the fixed contacts 1a and 2a from side to side with the side portions standing up on the left and right sides upward. Overlap on the side. As shown in FIG. 3, the fixed contactors 1 and 2 are mounted on the unit assembly frame 8, and are held between the fixed contacts 1 and 2 and the unit assembly frame 8 to be held at a predetermined position. I support it. In the figure, 1b and 2b are arc runners formed at the ends of the fixed contacts 1 and 2, and 1c is a power supply side terminal.

Moreover, the filling barrier insulating barrier 8a extended in the front-back direction is formed in the center of the said unit assembly frame 8. The insulating barrier 8a has a movable contact having a lower end portion of the wall splitting between the first fixed contact 1 and the second fixed contact 2 and extending upward as shown in FIG. It extends to the area | region of the opening movement path of 3).

On the other hand, the extinguishing device 4 is partitioned into the left and right arc extinguishing chambers corresponding to the first fixed contact 1 and the second fixed contact 2 separately, and between the side walls of the grid plate 4a. ) And an arc current plate 4b that extends between the left and right arc-extinguishing chambers at the top end. In addition, the arc current plate 4b is provided with a pair of left and right arc runners 4b-1 which project toward the opening movement path of the movable contactor 3 to be described later.

This arc extinguishing device 4 is assembled so that the insulation barrier 8a of the unit assembly frame 8 may be extended from above, and the arc runner which formed the left and right arc-extinguishing chamber at the front-end | tip of the fixed contactors 1 and 2, respectively. It is located opposite to (1b, 2b).

Next, the structure of the yoke cover 9 and the assembly procedure will be described. As shown in the figure, the yoke cover 9 is formed of a molded resin molded article having a cross-sectional inverted U-shape in which the left and right side walls extend in the vertical direction, and the magnetic yoke 6 is formed on the outer surface of the front end portion (lower end side) of the left and right side walls. The recessed part 9a of the shape corresponding to the side edge part of is formed. In addition, the height dimension of the yoke cover 9 corresponds to all the opening positions of the movable contact 3, and the short-length dimension is set so that the opening movement path of the movable contact may be covered by the side wall of the yoke cover from left and right. have.

This yoke cover 9 is attached to the unit assembly frame 8 in the same order as the following description. That is, in the assembling step in which the fixed contacts 1, 2, the magnetic yoke 6, and the arc extinguishing device 4 are attached to the unit assembly frame 8, two sets are provided on the left and right sides of the insulating barrier 8a. The yoke cover 9 of (iii) is attached from above. At this time, the concave portion 9a formed at the end of the side wall of the yoke cover 9 is aligned with the position of the magnetic yoke 6, and the side wall of the cover is inserted into the side of the yoke side that stands up, and the unit assembly frame 8 Support it mounted on.

In this assembled state (refer to FIG. 4 (a)-(d)), the left and right side walls of the yoke cover 9 cover the side part of the magnetic yoke 6 from the inside, and the fixed contacts 1 and 2 arrange | positioned here, and The insulation between the contacts of the movable contact 3 is insulated. Moreover, the front end of the yoke cover 9 opposes the entrance side of the extinguishing device 4, and is arrange | positioned so that the left-right extinguishing chamber and the inner space of the yoke cover 9 may go back and forth.

The assembling unit 7 of the current interruption unit having the above-described configuration is mounted on the bottom side of the main body case 1 in the same manner as the conventional circuit breaker shown in FIG. One movable contact 3 is disposed above the fixed contact 1, 2. FIG. 5 shows the arrangement of the fixed contacts 1 and 2 and the movable contacts 3 in this assembled state.

The current interruption operation according to the above configuration is basically the same as the conventional structures described with reference to Figs. 8 and 9, and when an overcurrent (short circuit current, etc.) flows through the distribution path, the fixed contactors 1 and 2 and the movable contactor 3 The electromagnetic repulsive force acts in between, and the movable contact 3 starts to open, and the movable contacts 3a and 3b open from the fixed contacts 1a and 2a. At the same time, the open / close mechanism 12 trips to drive the movable contact 3 toward the open end position.

In this case, in the illustrated embodiment, the magnetic yoke 6 is additionally equipped at the contact portions of the movable contacts 1, 2. Thereby, when overcurrent flows to the fixed contactors 1 and 2, the magnetic flux which generate | occur | produced in the magnetic yoke 6 acts on the movable contactor 3, reinforces an electromagnetic repulsive force, and raises the opening speed of the movable contactor 3. As shown in FIG.

Moreover, with the opening of the movable contactor 3, an arc arcs between the stationary contact 1a, 2a of the stationary contactor 1, 2, and the movable contact 3a of the entanglement movable contactor 3, and a movable contactor The arc expands with the opening movement of (3), and the arc voltage also increases. In this case, in the configuration of the illustrated embodiment, the opening movement path of the first fixed contactor 1 and the second fixed contactor 2 and the movable contactor 3 arranged on the left and right sides is the unit assembly frame 8. It is insulated and isolated by the insulating barrier 8a formed in (). In addition, the opening movement path of the movable contact 3 is also covered with the yoke cover 9 of the insulating material from side to side, and between the fixed contacts 1 and 2, sufficient insulation strength is provided in the region including the movement path of the movable contact 3. It is secured. Therefore, the arc extended between the fixed / movable contacts can flow to the fixed contact side in the middle of the opening movement of the movable contact 3, so that the fixed contacts 1 and 2 can be prevented from being directly connected by the arc.

And when the movable contactor 3 moves to the vicinity of all the opening positions, the arc extended between the fixed / movable contacts will be transferred to the extinguishing device 4 from the arm tip of the movable contactor 3 as shown in FIG. Current is supplied to the provided arc current plate 4b. In this case, since the arc runner 4b-1 protrudes toward the opening movement path of the movable contactor 3 in the arc current plate 4b, the arc arcs from the movable contactor 3 to the arc current plate 4b. Current smoothly). Further, on the fixed contact side, the arcing point of the arc moves from the fixed contact 1a to the arc runner 1b at the tip.

As a result, the arc is drawn into the arc extinguishing device 4 from the opening movement path side of the movable contact 3, and relays the arc current plate 4b disposed at the uppermost end over the left and right arc extinguishing chambers, so that the first fixed contact 1 ) And the arc extending between the second stationary contactor 2 are divided between the grid plates 4a and reach arc extinguishing by the current-limiting action.

Thus, the arc current plate of the arc-extinguishing device 4 from the movable contact 3a from the movable contact 3a near the opening end position of the movable contact 3 is extended and arced between the fixed / movable contacts by the opening operation of the movable contact 3. By carrying out the electric current by (4b), two arcs extend in the left-right arc extinguishing chamber between the 1st, 2nd fixed contact 1 and 2, using this arc current board 4b as a relay point, and It is divided by the grid plate 4a of the apparatus and receives a current-limiting action. In addition, since the arc length converges in the distance range between the arc current plate 4b and the fixed contacts 1 and 2, the increase in the arc voltage naturally becomes a value suitable for the current-limiting breaking capability.

Therefore, there is no possibility that the breakdown of insulation between the fixed contacts will occur due to excessive rise of the arc voltage. In addition, since the arc current does not flow to the movable contact 3 by this arc current, the amount of wear of the movable contact 3a is reduced and the life of a contact improves.

In addition, as an application embodiment of the present invention, when the yoke cover 9 is made of an organic polymer material such as polyamide resin, the yoke cover is received by arc heat extended and extended between the fixed and movable contacts when the current is interrupted. An arc-extinguishing ablation gas is generated from the wall surface of (9). Thereby, the yoke cover 9 functions as a slit-pole arc wall, and can further improve the current-limiting breaking performance of a circuit breaker.

1 is an exploded perspective view showing the unit assembly structure of the current interrupting unit;

2 is an external view of a unit assembled state of FIG.

3 is a view showing an assembled state in which the fixed contactor and the parts of the magnetic yoke are assembled to the unit assembly frame of FIG. 1, wherein (a) and (b) are side views and plan views, respectively;

FIG. 4 is a view showing an assembled state in which the extinguishing device, the magnetic yoke and the yoke cover are assembled to the unit assembly frame of FIG. XX section view as arrow of

5 is a perspective view showing the arrangement of the first and second fixed contacts and the entanglement movable contacts in the unit of FIG.

FIG. 6 is an operation explanatory diagram showing a process in which an arc extended between a fixed / movable contact and a current from the movable contact to the extinguishing device at the time of interrupting the current of FIG.

7 is an overall configuration diagram of a conventional two-point cutting circuit breaker

FIG. 8 is a perspective view of a configuration of the current blocking unit of FIG. 7; FIG.

9 is an explanatory diagram of a current-limiting breaking operation showing the behavior of an arc generated between the fixed and movable contacts in the current interrupting portion of FIG. 8;

(Explanation of symbols for the main parts of the drawing)

1: the first fixed contact

1a: fixed contact

2: the second fixed contact

2a: fixed contact

3: entanglement movable contactor

3a: movable contact

4: arc extinguishing device

4: SOHO grid plate

4b: arc current plate

4b-1: Arc Runner

6: magnetic yoke

7: assembly unit of current interrupting unit

8: unit assembly frame

8a: insulation barrier

9: yoke cover

9a: recess

Claims (5)

The first and second fixed contacts in which the current interruption unit is arranged in parallel to the left and right, and the fixed contact is fixed to the distal end thereof, and the rotational entangled movable contact in which the movable contact is fixed to the distal end of the U-shaped arm to face the fixed contact. And an arc extinguishing device disposed in front of the opening movement path of the movable contact in correspondence with each of the first and second fixed contacts, wherein the fixed contactor and the arc extinguishing device are mounted on a unit resin frame made of a molded resin. In the circuit breaker of the cutting method, The U-shaped magnetic yoke, in which the side edge portions stand up in the opening movement direction of the movable contactor, is disposed on the front end portions of the first and second fixed contactors from the left and right sides, and the first unit assembly frame includes a first yoke. An insulating barrier extending between the fixed contact of the fixed contact and the second fixed contact and extending throughout the opening movement path of the movable contact, and the magnetic yoke disposed on the left and right sides of the insulating barrier and disposed at the front ends of the first and second fixed contacts. Circuit breaker, characterized in that the yoke cover of the insulating material for covering the left and right side portions of the inside. The method of claim 1, The yoke cover is an inverted U-shaped insulating wall covering the opening movement path of the movable contact from left and right, and the front end portion of the side wall is inserted inside the left and right side portions of the magnetic yoke, and the front end is connected to the inlet side of the extinguishing device. Circuit breaker, characterized in that attached to the assembly frame. The method according to claim 1 or 2, A circuit breaker comprising the yoke cover made of an organic polymer material. The method of claim 1, The circuit breaker characterized by providing the arc current board which extends to the left-right arc extinguishing chamber which respond | corresponds to a 1st, 2nd fixed contactor separately at the open end side of the said arc extinguishing apparatus. The method of claim 4, wherein And a pair of left and right arc runners protruding toward the arm tip of the movable contact that has moved to the open end position.

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