An arc striking structure of a miniature circuit breaker

Abstract

The utility model discloses an arc leading structure of small circuit breaker relates to circuit breaker accessory technical field, solves the problem such as poor arc leading performance. The arc leading piece includes conducting part and arc leading part, and the conducting part is made of iron, and the arc leading part is made of copper, and the conducting part and arc leading part are fixed through the welding of electron beam welding layer between, and the arc leading piece is the shape of the horizontal bent hook. Through the composite material design of arc leading piece, the synergic optimization of the magnetic conductivity and the electric conductivity is realized, wherein, the iron quality conducting part can enhance the adsorption of coil magnetic field to electric arc, and the copper quality arc leading part can reduce the current loss, and avoid the overheat fuse under the large current, and the electron beam welding layer is the electron welding fixed, compared with the simple lap joint or ordinary welding, and the electron beam welding enhances the connecting strength of the composite part, and the connecting strength and the conductivity of the composite part are improved.

Description

Technical Field

[0001] This utility model relates to the technical field of circuit breaker accessories, specifically an arc-starting structure for a miniature circuit breaker. Background Technology

[0002] In low-voltage power distribution systems, miniature circuit breakers (MCBs) are core components for circuit protection, and their breaking capacity directly determines the safety and reliability of the circuit system. When a short circuit or overload fault occurs, the rapid separation of the moving and stationary contacts of the circuit breaker generates an electric arc. If the arc is not promptly introduced into the arc-extinguishing chamber and extinguished quickly, the high-temperature arc will not only burn the contacts but may also cause serious safety accidents such as switchgear explosions. The arc-initiating structure, as a crucial bridge connecting the contacts and the arc-extinguishing chamber, plays a decisive role in the generation, transfer, and extinguishing efficiency of the arc due to its magnetic permeability, electrical conductivity, and structural rationality. Currently, the arc-ignition structure commonly used in miniature circuit breakers often employs an integrated metal sheet design, typically made of pure iron or pure copper. While pure iron arc-ignition sheets possess good magnetic permeability, effectively attracting the arc through the magnetic field generated by the coil, their poor conductivity makes them prone to overheating under high current, leading to deformation or even melting. Pure copper arc-ignition sheets exhibit excellent conductivity, reducing current loss, but their weak magnetic permeability results in insufficient arc attraction, making it difficult to quickly guide the arc to the arc-extinguishing chamber, thus prolonging the arcing time and reducing the circuit breaker's breaking speed.

[0003] From a structural layout perspective, existing arc-starting plates are mostly straight or simply bent, and their relative positions and fit with the coil are not well designed. The welding positions of some arc-starting plates to the coil are off-center from the magnetic field center, resulting in low magnetic field utilization and insufficient arc driving force. Furthermore, the bending angle and extension direction of some arc-starting plates do not match the inlet position of the arc-extinguishing chamber, causing the arc to travel a tortuous path during transfer, leading to arc dispersion and significant energy loss. Utility Model Content

[0004] The purpose of this utility model is to overcome the defects of the prior art by providing an arc-starting structure for a miniature circuit breaker, thus solving problems such as poor arc-starting performance.

[0005] The technical solution of this utility model includes an arc-starting plate, an arc-extinguishing chamber, and a coil. The arc-starting plate is located above the arc-extinguishing chamber and is welded to the coil. The arc-starting plate includes a conductive part and an arc-starting part. The conductive part is made of iron, and the arc-starting part is made of copper. The conductive part and the arc-starting part are fixed by welding through a bonding layer. The arc-starting plate is in the shape of a horizontally placed hook. The conductive part includes a straight section and an upwardly bent section. The straight section is located below the coil body and is spaced apart from the coil. The upwardly bent section bends towards the coil. The arc-starting part includes a welding section, a downward turning section, and a curved arc section. The bonding layer is located between the upwardly bent section and the welding section. The welding section is straight and welded to the coil. The downward turning section is formed by bending away from the coil from the end of the downward turning section. The curved arc section forms a hook shape and is located on the side of the arc-extinguishing chamber near the top.

[0006] By adopting the above technical solution and through the composite material design of the arc-starting plate, the synergistic optimization of magnetic and electrical properties is achieved. The iron conductive part enhances the attraction of the coil's magnetic field to the arc, while the copper arc-starting part reduces current loss and prevents overheating and melting under high current, effectively solving the problem of single-material arc-starting plates having outstanding single performance but insufficient overall performance. The beam welding layer is fixed by electronic welding. Compared to existing simple lap joints or ordinary welding, electron beam welding has advantages such as high energy density, high welding precision, and a small heat-affected zone. It can achieve metallurgical bonding of two dissimilar metals, iron and copper, improving the connection strength of the composite part, avoiding loosening problems during long-term use, and improving the connection strength and conductivity of the composite part, reducing contact resistance, preventing loosening and oxidation problems during long-term use, and ensuring the stability of the arc-starting structure. Furthermore, the relative position of the arc-starting plate and the coil matches the center of the magnetic field, improving magnetic field utilization and arc driving force. At the same time, the hook shape allows the arc to form a smooth transfer path from the coil area through the downward turning section and the curved arc angle section, accurately connecting to the arc-extinguishing chamber inlet, solving the defects of the existing structure's tortuous arc path and high energy loss, and improving arc guiding efficiency.

[0007] In one possible design, the arc-starting plate is provided with a raised stationary contact, which is fixed to the connection between the downward turning section and the curved arc section by welding.

[0008] With the above design, when the circuit breaker is closed, the transmission mechanism drives the moving contact to contact the stationary contact of the convex block. The welding fixing method ensures that the connection between the two is reliable. The convex block structure is adapted to the movement trajectory of the moving contact, effectively reducing contact resistance, avoiding current concentration and overheating, and ensuring smooth circuit conduction. When the circuit breaker is opened, the electric arc generated at the moment the moving contact leaves can initially adhere to the stationary contact of the convex block. The electric field concentration effect formed by the convex block makes the arc stable and does not drift, realizing seamless transmission of the arc from the contact point to the arc ignition part, and then efficiently guiding it to the arc extinguishing chamber through the arc ignition part. This not only improves the arc extinguishing speed and the circuit breaker's breaking capacity, but also simplifies the overall structure by eliminating the independent stationary contact component, reduces production and assembly costs, and improves product reliability.

[0009] In one possible design, the downward turning segment is arranged as a vertical bend.

[0010] With the above design, the vertical bend forms the shortest path from the horizontal welding section to the vertical arc-extinguishing chamber grid, reducing unnecessary bends and ensuring that the curved arc segment at the end of the arc-initiating section can be aligned with the arc-extinguishing chamber inlet, so that the electric arc can be directly introduced into the arc-extinguishing chamber downwards with the highest efficiency.

[0011] In one possible design, the distance between the straight segment and the coil body is 0.5-2mm.

[0012] By adopting the above design, the interval range can balance the contradiction between electromagnetic interference and magnetic field force. It avoids electromagnetic interference between the coil and the arc-starting plate caused by the interval being too close, and prevents the magnetic field from weakening the arc attraction force caused by the interval being too far. It ensures that the magnetic field of the coil can act stably on the conductive part, providing a continuous driving force for the arc and improving the stability of the arc-starting process.

[0013] In one possible design, the bending angle of the upward bending segment is 120°-150°.

[0014] By adopting the above design, this angle allows the current and magnetic field to smoothly transition from the horizontal straight section to the welded section that is welded to the coil, reducing the distortion of magnetic flux and current, and ensuring the efficiency of energy transmission and conversion.

[0015] In one possible design, the curvature of the curved arc segment is 90°-120°.

[0016] With the above design, the arc range ensures that the end shape of the arc-initiating plate can match the upper outer contour of the arc-extinguishing chamber, forming a tapered guide port. This shape can catch the arc and guide it into the depth of the arc-extinguishing chamber, avoiding the problems of arc obstruction caused by sharp bends due to too small an angle, or unclear guiding direction caused by flatness due to too large an angle. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the miniature circuit breaker of this utility model; Figure 2 This is a schematic diagram of the structure of the present invention. Figure 1 ; Figure 3 This is a schematic diagram of the structure of the present invention. Figure 2 ; Among them, 1. Arc-starting plate; 11. Conductive part; 111. Straight section; 112. Upward bending section; 12. Arc-starting part; 121. Welding section; 122. Downward turning section; 123. Bending arc angle section; 13. Bundled welding layer; 14. Protrusion stationary contact; 2. Arc extinguishing chamber; 3. Coil; 4. Moving contact. Detailed Implementation

[0018] like Figures 1 to 3 The arc-starting structure of a miniature circuit breaker shown includes an arc-starting plate 1, an arc-extinguishing chamber 2, and a coil 3. The arc-starting plate 1 is generally shaped like a horizontal hook and is located directly above the arc-extinguishing chamber 2, with one end welded to the coil 3. The arc-starting plate 1 is composed of a conductive part 11 and an arc-starting part 12 connected by an electron beam welding layer 4, which is about 1.5 mm thick. The conductive part 11 is made of pure iron, and the arc-starting part 12 is made of copper to balance magnetic and electrical conductivity.

[0019] The conductive part 11 includes an integrally formed straight segment 111 and an upwardly bent segment 112. One end of the upwardly bent segment 112 is bent in a predetermined direction using a device, with the bending angle controlled between 120° and 150°, preferably 150°. The straight segment 111 has a horizontally extending structure, its length matching the axial length of the coil 3 body. After assembly, the straight segment 111 is located directly below the coil 3 body, and the distance between them is between 0.5 and 2 mm, preferably 1 mm.

[0020] The arc-starting section 12 includes an integrally formed welding section 121, a downward turning section 122, and a curved arc section 123. The welding section 121 is a horizontal straight structure; the downward turning section 122 is formed by bending vertically downward from the end of the welding section 121, with the verticality deviation of the bend controlled within ±3°; the curved arc section 123 bends from the end of the downward turning section 122 towards the arc-extinguishing chamber 2, forming a hook-shaped structure with an arc angle in the range of 90°-120°, preferably 120°, and the orientation of the hook-shaped end corresponds to the inlet position of the arc-extinguishing chamber 2, ensuring that the curved arc section 123 is located on the side of the arc-extinguishing chamber 2 near the top.

[0021] The connection between the conductive part 11 and the arc-starting part 12 is achieved by welding the end of the upwardly bent section 112 of the conductive part 11 to the starting end of the welding section 121 of the arc-starting part 12 using an electron beam welding device, forming a dense beam weld layer 13 to ensure a reliable connection between the conductive part 11 and the arc-starting part 12. In actual processing, before the arc-starting piece 1 is formed, the parts to be welded on the iron plate and the copper plate are aligned and placed in the electron beam welding device for welding. After welding is completed, the plates are stamped and cut to achieve the final forming of the arc-starting piece 1.

[0022] A raised stationary contact 14 is welded at the connection between the downward turning section 122 and the curved arc section 123 of the arc-initiating part 12. The raised stationary contact 14 is made of silver alloy and processed into a sheet structure with a thickness of 1mm. It is fixed to the outer surface of the connection by brazing. In actual use, when the circuit breaker is in the closed state, the moving contact 4 of the transmission mechanism of the miniature circuit breaker will contact the raised stationary contact 14 under the drive of the transmission mechanism. When it is necessary to open, the moving contact 4 moves backward under the drive of the transmission mechanism and disengages from the raised stationary contact 14. The arc generated by the opening of the moving contact 4 can be led from the arc-initiating part 12 to the arc-extinguishing chamber 2, and finally the arc is extinguished.

[0023] The working principle of this application is as follows: When the circuit breaker generates an arc due to contact separation caused by short circuit or overload, the iron conductive part 11 generates a strong magnetic attraction force under the action of the magnetic field, which quickly attracts the arc and conducts it to the arc ignition part 12; the beam welding layer 4 formed by electron beam welding ensures stable current conduction and avoids energy loss caused by excessive contact resistance; the arc is smoothly transmitted along the welding section 121 and the vertical downward turning section 122 of the arc ignition part 12, and the electric field concentration area formed by the convex stationary contact 14 makes the arc quickly converge and stabilize the arc root, preventing drift; finally, it is introduced into the arc extinguishing chamber 2 through the curved arc corner section 123 to achieve rapid arc extinguishing.

Claims

1. An arc-starting structure for a miniature circuit breaker, comprising an arc-starting plate, an arc-extinguishing chamber, and a coil, wherein the arc-starting plate is located above the arc-extinguishing chamber and is welded to the coil; characterized in that: The arc-starting plate includes a conductive part and an arc-starting part. The conductive part is made of iron, and the arc-starting part is made of copper. The conductive part and the arc-starting part are welded and fixed together by a bonding layer. The arc-starting plate is in the shape of a horizontally placed hook. The conductive part includes a straight section and an upwardly bent section. The straight section is located below the coil body and is spaced apart from the coil. The upwardly bent section bends towards the coil. The arc-starting part includes a welding section, a downward turning section, and a curved arc section. The bonding layer is located between the upwardly bent section and the welding section. The welding section is straight and welded to the coil. The downward turning section bends away from the coil from the end of the downward turning section. The curved arc section forms a hook shape and is located on the side of the arc-extinguishing chamber near the top.

2. The arc-starting structure of the miniature circuit breaker according to claim 1, characterized in that: The arc-starting plate is provided with a raised stationary contact, which is fixed to the connection between the downward turning section and the curved arc section by welding.

3. The arc-starting structure of the miniature circuit breaker according to claim 1 or 2, characterized in that: The downward turning segment is arranged with a vertical bend.

4. The arc-starting structure of the miniature circuit breaker according to claim 1 or 2, characterized in that: The distance between the straight segment and the coil body is 0.5-2mm.

5. The arc-starting structure of the miniature circuit breaker according to claim 1 or 2, characterized in that: The bending angle of the upward bending section is 120°-150°.

6. The arc-starting structure of the miniature circuit breaker according to claim 1 or 2, characterized in that: The curvature of the curved arc segment is 90°-120°.

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