Circuit breaker

Abstract

To provide a circuit breaker that can improve current limiting performance by quick opening action performed by the movable contact even when the electromagnetic repulsive force weakens during current limiting interruption, thereby, suppressing the closing action of the movable contact.SOLUTION: A circuit breaker includes: a fixed contactor 2 having a fixed contact 2a; a movable contactor 3 having a movable contact 3a that moves to contact with or separate away from the fixed contact; and a U-shaped magnetic yoke 5 having a yoke opening 5e that opens toward the fixed contact and is supported by the housing such that the movable contactor, which performs the opening operation, moves into the yoke opening. Therein the movable contactor performs the opening operation by electromagnetic repulsive force when an overcurrent occurs, and passes through the yoke opening 5e when the electromagnetic repulsive force weakens and the opening operation is performed by inertia.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a circuit breaker that is applied to a molded case circuit breaker, an earth leakage breaker, or the like. [Background technology]

[0002] For example, Patent Document 1 discloses a current-limiting circuit breaker that includes a fixed contactor having a fixed contact and a movable contactor having a movable contact that makes contact with and separates from the fixed contact, and when an overcurrent occurs, an electromagnetic repulsive force is generated between the fixed contact and the movable contact, causing the movable contactor to open. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-220610 Summary of the Invention [Problem to be solved by the invention]

[0004] In the circuit breaker of Patent Document 1, as the moving contact moves away from the fixed contact, the electromagnetic repulsive force suddenly weakens, and the magnetic flux generated in the internal space of the magnetic body, which is a closed magnetic circuit, is also small, so the Lorentz force acting on the moving contact in the opening direction, which is caused by the current and magnetic flux flowing through the moving contact, becomes small. As a result, the moving contact moves in the closing direction, causing the moving contact to approach the fixed contact again and re-forming an arc, or there is a risk that the arc voltage will drop due to the moving contact and the fixed contact re-contacting, which could degrade the current limiting performance.

[0005] Therefore, the present invention has been made by focusing on the problems of the conventional example described in the above Patent Document 1, and aims to provide a circuit breaker in which the movable contact performs a quick opening operation even when the electromagnetic repulsive force weakens during current-limiting interruption, and the closing operation of the movable contact is suppressed, thereby improving current-limiting performance. [Means for solving the problem]

[0006] In order to achieve the above object, the circuit breaker of the present invention comprises a fixed contactor having a fixed contact, a movable contactor having a movable contact that moves towards and away from the fixed contact, and a U-shaped magnetic yoke whose yoke opening opens towards the fixed contact and is supported by a housing so that the movable contactor, which performs an opening operation, moves into the yoke opening, and the movable contactor performs an opening operation using electromagnetic repulsive force when an overcurrent occurs, and passes through the yoke opening when the electromagnetic repulsive force weakens and performs an opening operation due to inertia. [Effects of the Invention]

[0007] According to the circuit breaker of the present invention, even if the electromagnetic repulsive force weakens during current-limiting interruption, the movable contactor performs a quick opening operation, and the closing operation of the movable contactor is suppressed, thereby improving current-limiting performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a perspective view showing a waist portion of the circuit breaker according to the present invention. [Figure 2] FIG. 2 is a front view showing the circuit breaker during current-limiting tripping. [Figure 3] 10A and 10B are diagrams illustrating positions where the electromagnetic repulsive force acting on the movable contact is weakened during current-limiting interruption of the circuit breaker. [Figure 4] 10 is a diagram showing a state in which a Lorentz force acts to push up the movable contact in the opening direction at a position where the electromagnetic repulsive force acting on the movable contact is weak. FIG. [Figure 5] This figure shows the state in which a Lorentz force acts, moving the arc toward the grid, due to the current of the arc generated between the fixed contact and the movable contact and the magnetic flux generated in the magnetic grid of the arc extinguishing device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc., may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios.

[0010] Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, arrangements, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[0011] A circuit breaker 1 according to one embodiment of the present invention, which is applicable as a molded case circuit breaker or an earth leakage circuit breaker, will be described with reference to Figures 1 to 5. In each drawing, the configuration of each component will be described with specific directions such as up, down, front, back, left, and right.

[0012] 1 and 2, the circuit breaker 1 of this embodiment includes a fixed contactor 2 having a fixed contact 2a, a movable contactor 3 having a movable contact 3a that moves in and out of contact with the fixed contact 2a, an arc extinguishing device 4 disposed on the left side of the fixed contact 2a at a distance, and a magnetic yoke 5 that opens toward the fixed contact 2a. These components of the circuit breaker 1 are housed in a housing (not shown) made of an insulating resin material.

[0013] 2, the fixed contact 2 includes a flat substrate portion 2b and a contact side plate portion 2c that is bent upward from the right end of the substrate portion 2b and then further bent toward the left, with the fixed contact 2a provided on the upper surface of the contact side plate portion 2c. An arc runner 6 is provided on the upper surface of the contact side plate portion 2c to the left of the fixed contact 2a.

[0014] The movable contactor 3 is a conductor having a movable contact 3a on the underside of the left end and a support shaft portion 3b extending in the front-to-rear direction at the right end, and is arranged to be freely rotatable via the support shaft portion 3b so that the movable contact 3a moves toward and away from the fixed contact 2a along a moving trajectory T.

[0015] As shown in FIGS. 1 and 2, the arc extinguishing device 4 includes a plurality of grids 4a made of a magnetic material formed in a U-shape or a V-shape, and a pair of side plates 4b and 4c that support the plurality of grids 4a in a stacked state, and the plurality of grids 4a are arranged so as to surround the movement locus T of the movable contact 3a.

[0016] As shown in Fig. 3, the magnetic yoke 5 is a component in which a pair of side plates 5a, 5b and a top plate 5c made of a soft magnetic material such as iron are insert-molded into a resin material. That is, the pair of side plates 5a, 5b are arranged parallel to each other, and the top plate 5c is arranged perpendicular to one end of the pair of side plates 5a, 5b. The outer peripheries of the pair of side plates 5a, 5b and top plate 5c are covered with side plate insulating portions 5d1, 5d2 and top plate insulating portion 5d3 made of a resin material to form a U-shaped component. The magnetic yoke 5 also has an opening 5e between the lower ends 5a1, 5b1 of the pair of side plates 5a, 5b.

[0017] The magnetic yoke 5 is incorporated into the housing with the opening 5e facing the fixed contact 2a and the pair of side plates 5a, 5b arranged opposite each other along the movement locus T of the movable contact 3a.

[0018] When an overcurrent flows through the circuit breaker 1, an electromagnetic repulsive force is generated between the fixed contact 2a and the movable contact 3a, causing the movable contactor 3 to open, resulting in a current-limiting interruption. As shown in Fig. 3, when the movable contactor 3a moves away from the fixed contact 2a to a predetermined opening position 3L, the electromagnetic repulsive force of the opened movable contactor 3 suddenly weakens, causing an opening operation due to inertia. In this embodiment, the movable contactor 3 is set to pass through the opening 5e of the magnetic yoke 5 at the position where the electromagnetic repulsive force suddenly weakens and an opening operation due to inertia occurs (predetermined opening position 3L).

[0019] Note that the grid described in the present invention corresponds to grid 4a, the pair of side plate yokes described in the present invention correspond to the pair of side plates 5a and 5b, the top plate yoke described in the present invention corresponds to the top plate 5c, and the yoke opening described in the present invention corresponds to opening 5e.

[0020] Next, the current-limiting opening operation of the circuit breaker 1 of this embodiment will be described.

[0021] When a short-circuit current or an overcurrent such as an overload current flows through the circuit breaker 1 configured as described above, an electromagnetic repulsive force acts between the fixed contact 2a and the movable contact 3a, causing the movable contactor 3 to open. At the same time, an arc 8 occurs between the fixed contact 2a and the movable contact 3a, causing a current to flow from the fixed contact 2a to the movable contact 3a.

[0022] 4, a self-magnetic flux φ1 is generated by the current (flowing from the front to the back of the page) flowing through the movable contact 3. This self-magnetic flux φ1 of the movable contact 3 forms a magnetic path for magnetic flux φ2 in the magnetic yoke 15. At this time, the magnetic flux φ2 is concentrated in the region indicated by the two-dot chain line in the opening 5e between the lower ends 5a1 and 5b1 of the magnetic yoke 5 (hereinafter, this region will be referred to as the opening 5e where the magnetic flux φ2 is concentrated).

[0023] When the movable contact 3L is opened to a position where the electromagnetic repulsive force suddenly weakens, it passes through the opening 5e where the magnetic flux φ2 is concentrated, and according to Fleming's left-hand rule, a Lorentz force F1 acts on the movable contact 3L in the opening direction (upward).

[0024] Furthermore, when the movable contactor 3L passes through the opening 5e where the magnetic flux φ2 is concentrated, an eddy current corresponding to the magnetic flux density gradient is generated on the surface of the movable contactor 3L, and the magnetic poles caused by the eddy currents cause an acceleration in the movable contactor 3L in the opening direction.

[0025] Furthermore, even if the movable contactor 3, which has moved to the maximum open position, collides with the top plate insulating portion 5d3 of the magnetic yoke 5, the top plate 5c made of metal inside the top plate insulating portion 5d3 receives the impact force of the movable contactor 3, so the collision of the movable contactor 3 does not affect the housing arranged around the movable contactor 3.

[0026] Meanwhile, as shown in Fig. 5, a self-magnetic flux φ3 is generated in the arc 8, forming a magnetic path of magnetic flux φ4 in the grid 4a of the arc extinguishing device 4. Due to the direction of current flow in the arc 8 and the magnetic flux φ4, a Lorentz force F2 acts on the arc 8 in the direction toward the grid 4a according to Fleming's left-hand rule. As shown in Fig. 5, the arc 8, on which the Lorentz force F2 acts, is extended as the arc end on the fixed contact 2a side is driven toward the arc runner 6, and is broken when it comes into contact with the grid 4a, and the arc voltage is increased by the electrode drop voltage.

[0027] Next, the effect of the current-limiting opening operation of the circuit breaker 1 of this embodiment will be described.

[0028] In the circuit breaker 1 of this embodiment, when the movable contact 3L moves to a position where the electromagnetic repulsive force is weak, the Lorentz force F1 acts in the opening direction as it passes through the opening 5e where the magnetic flux φ2 is concentrated, and the magnetic pole caused by the eddy current generated on the surface of the movable contact 3L generates acceleration of the movable contact 3L in the opening direction. Therefore, the movable contact 3L performs a quick opening operation, thereby improving the current limiting performance.

[0029] Furthermore, even if the movable contactor 3, which has moved to the maximum open position, collides with the top plate insulating portion 5d3 of the magnetic yoke 5, the top plate 5c of the magnetic yoke 5 receives the impact force of the movable contactor 3, thereby preventing damage caused by the collision of the movable contactor 3 to the housing arranged around the movable contactor 3.

[0030] Furthermore, even after the contact is opened, the magnetic flux φ2 generated by the magnetic yoke 5 acts on the movable contact 3, and the Lorentz force F1 in the opening direction continues to act on the movable contact 3, so the movable contact 3 does not move in the closing direction and the opening operation of the movable contact 3 can be maintained. Therefore, the current limiting performance can be further improved.

[0031] Furthermore, the generation of arc 8 forms a magnetic path through which magnetic flux φ4 flows in grid 4a of arc extinguishing device 4, and a Lorentz force F2 acts in the direction toward grid 4a due to the current and magnetic flux φ4 of arc 8. As a result, arc 8 is extended by driving the arc end on the fixed contact 2a side toward arc runner 6, and the arc voltage is increased by the electrode drop voltage. Therefore, the current limiting performance can be improved by the rapid arc extinguishing operation. [Explanation of symbols]

[0032] 1 Circuit Breaker 1 2 Fixed contact 2a fixed contact 2b Board part 2c Contact side plate 3 Moving contact 3a Movable contact 3b Support shaft part 3L The moving contact has moved to a position where the electromagnetic repulsive force is weaker. 4 Arc extinguishing device 4a Grid 4b,4c side plate 5 Magnetic Yoke 5a,5b side plate 5a1, 5b1 Lower end of side plate 5c Top plate 5d1, 5d2 Side plate insulation 5d3 Top plate insulation 5e opening 6 Arc Runner 5d1, 5d2 Side plate insulation 5d3 Top plate insulation T Moving contact movement path

Claims

1. a fixed contactor having a fixed contact; a movable contactor having a movable contact that moves in contact with and separates from the fixed contact; a U-shaped magnetic yoke having a yoke opening that opens toward the fixed contact, and the movable contact that performs a contact opening operation is supported by a housing so as to move into the yoke opening, The movable contact performs an opening operation by electromagnetic repulsive force when an overcurrent occurs, and passes through the yoke opening when the electromagnetic repulsive force weakens and the movable contact performs an opening operation by inertia.

2. the magnetic yoke comprises a pair of side plate yokes arranged opposite to each other across the moving locus of the movable contact, and a top plate yoke connecting one end of the pair of side plate yokes to form a magnetic path, 2. The circuit breaker according to claim 1, wherein said movable contactor, when moved to a maximum open position, comes into contact with said top plate yoke.

3. 3. The circuit breaker according to claim 2, wherein the pair of side plate yokes and the top plate yoke are insert-molded in an insulating resin material.

4. 4. The circuit breaker according to claim 1, wherein a grid made of a magnetic material is arranged in the vicinity of the fixed contact, and when an arc occurs between the fixed contact and the movable contact, a current flowing in the arc and a magnetic flux caused by the self-magnetic flux of the arc flow in the grid, thereby acting a Lorentz force in the direction away from the grid.

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