A closing resistor contact assembly for a circuit breaker and a circuit breaker.

Abstract

This invention relates to the field of circuit breaker technology, and more particularly to a closing resistor contact assembly for a circuit breaker and a circuit breaker itself. The closing resistor contact assembly for a circuit breaker includes a stationary contact assembly and a moving contact assembly. The stationary contact assembly includes a stationary resistor contact and a stationary contact rod connected to the stationary resistor contact. The moving contact assembly includes a moving resistor contact and a moving contact rod connected to the moving resistor contact. The front ends of both the stationary and moving resistor contacts are arc-shaped surfaces, with one having an arc-shaped protrusion at its center and the other having a groove at its center for the arc-shaped protrusion to insert into and make conductive contact with during closing. The center of the front ends of the moving and stationary resistor contacts adopts a convex-concave structure. During the circuit breaker closing process, the resistor break point with the convex-concave structure reaches the breakdown field strength earlier than the main break point, thus ensuring that the resistor break point breaks down before the main break point, and the closing resistor is effectively connected to the main circuit.

Description

Technical Field

[0001] This invention relates to the field of circuit breaker technology, and in particular to a closing resistor contact assembly for a circuit breaker and a circuit breaker. Background Technology

[0002] A circuit breaker with a closing resistor consists of a main circuit and a resistor circuit connected in parallel. When the circuit breaker closes, the resistor contact is connected to the main circuit in advance, so that the energy of the overvoltage can be dissipated in the closing resistor, thereby limiting and eliminating the line overvoltage. To ensure that the closing resistor can be effectively connected to the line and achieve the purpose of limiting and eliminating overvoltage, the closing resistor contact must be connected to the main circuit before the main contact.

[0003] Chinese invention patent application CN116313618A discloses a closing resistor contact assembly and a circuit breaker. The closing resistor stationary contact assembly and the closing resistor moving contact assembly have the same structure, both including a contact rod, a contact, and a shield. The contact is threaded onto the contact rod, and a preload is press-fitted between the contact and the contact rod. A shield is also press-fitted between the contact and the contact rod to shield the electric field at the contact and contact rod. The contact has an arc-shaped side and a smooth side, with the edge of the arc-shaped side connecting to the edge of the smooth side. The center of the front end of the arc-shaped side is a small plane, which forms a conductive contact surface. When the circuit breaker closes, the moving resistor contact moves with the moving contact of the main circuit. The moving resistor contact connects with the stationary resistor contact before the moving contact of the main circuit connects with the stationary contact of the main circuit, so that the energy of the overvoltage is dissipated on the closing resistor, preventing the main circuit contact from burning out.

[0004] Because the resistive contact device shares a transmission system with the main contact, and the opening distance of the main contact is greater than that of the resistive contact, ideally, breakdown should occur first at the resistive contact, and the moving and stationary resistive contacts should connect first. However, in practical applications, it has been found that during circuit breaker closing, the main contact may break down first and prematurely connect to the main circuit. Under this condition, the closing resistor cannot effectively limit overvoltage. Simulations of the electric field strength at the main and resistive contacts during circuit breaker closing revealed that, based on the current resistive contact structure (i.e., the front end of the resistive contact is planar), the electric field strength at the main contact remains higher than that at the resistive contact until the gas breakdown threshold is reached. This indicates that the main contact will break down first. Therefore, a resistive contact needs to be designed to ensure that the electric field strength at the resistive contact reaches the breakdown strength before the main contact during circuit breaker closing, thus ensuring that the resistive contact connects to the main circuit before the main contact. Summary of the Invention

[0005] The purpose of this invention is to provide a closing resistor contact assembly for a circuit breaker to solve the problem that the main contact of the existing circuit breaker is broken down first during the closing process and connected to the main circuit in advance, resulting in the closing resistor being unable to effectively limit overvoltage; the purpose of this invention is also to provide a circuit breaker to solve the aforementioned problems.

[0006] The closing resistor contact assembly for the circuit breaker of the present invention adopts the following technical solution: A closing resistor contact assembly for a circuit breaker includes a stationary contact assembly and a moving contact assembly. The stationary contact assembly includes a stationary resistor contact and a stationary contact rod connected to the stationary resistor contact. The moving contact assembly includes a moving resistor contact and a moving contact rod connected to the moving resistor contact. The front end faces of both the stationary and moving resistor contacts are arc-shaped, and one of them has an arc-shaped protrusion at the center of its front end. The other has a groove at the center of its front end for the arc-shaped protrusion to be inserted into and make conductive contact with the arc-shaped protrusion when the circuit is closed.

[0007] Furthermore, the groove depth is greater than the height of the arc-shaped protrusion.

[0008] Furthermore, the arc-shaped protrusion and the front end face of the contact it belongs to, as well as the groove and the front end face of the contact it belongs to, are all transitioned by arc surfaces.

[0009] Furthermore, the stationary contact assembly also includes a guide cylinder and a damping structure. The stationary contact rod is guided and movably inserted into the guide cylinder, and the stationary resistance contact is connected to the front end of the stationary contact rod. The damping structure includes a piston cylinder and a piston disposed in the piston cylinder. The piston is fixedly connected to the stationary contact rod. A guide rod parallel to the piston cylinder axis and fixedly connected to the piston cylinder is provided in the piston cylinder. The piston is movably inserted on the guide rod and has an air gap between it and the guide rod. The guide rod is fixedly connected to the rear end of the guide cylinder. The end of the piston cylinder near the guide cylinder is an open structure. The stationary contact assembly also includes a return spring for applying an elastic force to the stationary resistance contact to force it to reset.

[0010] Furthermore, a stationary end shield is sandwiched between the stationary end resistor contact and the stationary end contact rod, and the reset spring is a compression spring disposed between the stationary end shield and the guide cylinder.

[0011] Furthermore, the compression spring is fitted onto the stationary contact rod, and the front end of the guide cylinder is provided with a receiving groove. The rear end of the compression spring extends into the receiving groove and presses against the bottom surface of the receiving groove.

[0012] Furthermore, the tail of the stationary contact rod has a reduced diameter section, forming a rearward stepped surface on the stationary contact rod. The piston is fitted onto the reduced diameter section, and a clamping nut is threaded onto the reduced diameter section to press the piston against the stepped surface.

[0013] Furthermore, the piston cylinder has a clearance groove on the bottom of the cylinder to avoid the tail of the stationary contact rod.

[0014] Furthermore, a shielding component is provided at the rear end of the piston cylinder.

[0015] Beneficial Effects: This invention is an improved invention. The front ends of both the stationary and moving resistor contacts are arc-shaped, with one having an arc-shaped protrusion at its center and the other having a groove at its center for the arc-shaped protrusion to insert into and make conductive contact with during closing. The front ends of the stationary and moving resistor contacts employ a convex-concave structure. During circuit breaker closing, the resistor break point with the convex-concave structure reaches the breakdown field strength earlier than the flat resistor break point at the center of the moving and stationary resistor contacts, and also earlier than the main break point. This ensures that the resistor break point breaks down before the main break point, effectively connecting the closing resistor to the main circuit.

[0016] The circuit breaker of this invention adopts the following technical solution: The circuit breaker includes an arc-extinguishing chamber, which contains a main circuit and a resistance circuit connected in parallel. The main circuit includes a moving main contact and a stationary main contact. The resistance circuit includes a closing resistor contact assembly and a closing resistor. The closing resistor contact assembly includes a stationary contact assembly and a moving contact assembly. The stationary contact assembly includes a stationary resistor contact and a stationary contact rod connected to the stationary resistor contact. The moving contact assembly includes a moving resistor contact and a moving contact rod connected to the moving resistor contact. The front end faces of both the stationary and moving resistor contacts are arc-shaped, and one of them has an arc-shaped protrusion at the center of its front end. The other has a groove at the center of its front end for the arc-shaped protrusion to insert into and make conductive contact with the arc-shaped protrusion when the circuit is closed.

[0017] Furthermore, the groove depth is greater than the height of the arc-shaped protrusion.

[0018] Furthermore, the arc-shaped protrusion and the front end face of the contact it belongs to, as well as the groove and the front end face of the contact it belongs to, are all transitioned by arc surfaces.

[0019] Furthermore, the stationary contact assembly also includes a guide cylinder and a damping structure. The stationary contact rod is guided and movably inserted into the guide cylinder, and the stationary resistance contact is connected to the front end of the stationary contact rod. The damping structure includes a piston cylinder and a piston disposed in the piston cylinder. The piston is fixedly connected to the stationary contact rod. A guide rod parallel to the piston cylinder axis and fixedly connected to the piston cylinder is provided in the piston cylinder. The piston is movably inserted on the guide rod and has an air gap between it and the guide rod. The guide rod is fixedly connected to the rear end of the guide cylinder. The end of the piston cylinder near the guide cylinder is an open structure. The stationary contact assembly also includes a return spring for applying an elastic force to the stationary resistance contact to force it to reset.

[0020] Furthermore, a stationary end shield is sandwiched between the stationary end resistor contact and the stationary end contact rod, and the reset spring is a compression spring disposed between the stationary end shield and the guide cylinder.

[0021] Furthermore, the compression spring is fitted onto the stationary contact rod, and the front end of the guide cylinder is provided with a receiving groove. The rear end of the compression spring extends into the receiving groove and presses against the bottom surface of the receiving groove.

[0022] Furthermore, the tail of the stationary contact rod has a reduced diameter section, forming a rearward stepped surface on the stationary contact rod. The piston is fitted onto the reduced diameter section, and a clamping nut is threaded onto the reduced diameter section to press the piston against the stepped surface.

[0023] Furthermore, the piston cylinder has a clearance groove on the bottom of the cylinder to avoid the tail of the stationary contact rod.

[0024] Furthermore, a shielding component is provided at the rear end of the piston cylinder.

[0025] Beneficial Effects: This invention is an improved invention. The front ends of both the stationary and moving resistor contacts are arc-shaped, with one having an arc-shaped protrusion at its center and the other having a groove at its center for the arc-shaped protrusion to insert into and make conductive contact with during closing. The front ends of the stationary and moving resistor contacts employ a convex-concave structure. During circuit breaker closing, the resistor break point with the convex-concave structure reaches the breakdown field strength earlier than the flat resistor break point at the center of the moving and stationary resistor contacts, and also earlier than the main break point. This ensures that the resistor break point breaks down before the main break point, effectively connecting the closing resistor to the main circuit. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the closing resistor contact assembly. Figure 2 This is a schematic diagram showing the separation of the moving and stationary resistor contacts. Figure 3 This is a schematic diagram showing the contact of the moving and stationary resistor contacts when the circuit is closed. In the diagram: 1. Shielding component; 2. Piston; 3. Guide rod; 4. Piston cylinder; 4-1. Clearance groove; 5. Stationary contact rod; 6. Guide cylinder; 7. Return spring; 8. Stationary shielding cover; 9. Stationary resistor contact; 9-1. Arc-shaped protrusion; 10. Compression nut; 11. Moving resistor contact; 11-1. Groove; 12. Moving shielding cover; 13. Moving contact rod. Detailed Implementation

[0027] This invention primarily addresses the problem that in existing circuit breakers, the main contact breaks down first during the closing process, prematurely connecting to the main circuit and causing the closing resistor to fail to effectively limit overvoltage. The basic inventive concept is to design the center of the front end of both the stationary and moving resistor contacts as a convex-concave structure. Through electric field simulation and experimental verification, during circuit breaker closing, the convex-concave resistor contact reaches the breakdown field strength earlier than the main contact, thus ensuring that the resistor contact breaks down before the main contact, and the closing resistor is effectively connected to the main circuit.

[0028] Based on the above inventive concept, the embodiments of the present invention will be described in detail below.

[0029] The circuit breaker includes an arc-extinguishing chamber, which contains a main circuit and a resistance circuit connected in parallel. The main circuit includes a moving main contact and a stationary main contact. The resistance circuit includes a closing resistor contact assembly and a closing resistor. The closing resistor contact assembly includes a stationary contact assembly and a moving contact assembly arranged opposite to each other. The stationary contact assembly is on the same side as the stationary main contact, and the moving contact assembly is on the same side as the moving main contact and shares a common drive system.

[0030] like Figure 1 As shown, the stationary contact assembly includes a stationary resistive contact 9, a stationary contact rod 5, a stationary shield 8, a guide cylinder 6, a damping structure, and other components. The stationary resistive contact 9 is fixedly connected to the front end of the stationary contact rod 5. The stationary shield 8 is clamped between the stationary resistive contact 9 and the stationary contact rod 5. The stationary contact rod 5 is guided and movably inserted into the guide cylinder 6. The guide cylinder 6 guides the movement of the stationary contact rod 5, preventing the stationary resistive contact 9 from becoming eccentric during the opening and closing process, thereby ensuring the accuracy and reliability of opening and closing. The moving contact assembly includes a moving resistive contact 11, a moving contact rod 13, and a moving shield 12. The moving resistive contact 11 is fixedly connected to the front end of the moving contact rod 13. The moving shield 12 is clamped between the moving resistive contact 11 and the moving contact rod 13. The moving contact rod 13 is connected to the transmission system. The front end faces of both the stationary resistor contact 9 and the moving resistor contact 11 are arc surfaces. The stationary resistor contact 9 has an arc-shaped protrusion 9-1 at the center of its front end, and the moving resistor contact 11 has a groove 11-1 at the center of its front end. When the circuit is closed, the arc-shaped protrusion 9-1 is inserted into the groove 11-1 and forms a conductive contact with the groove 11-1.

[0031] like Figure 2As shown, the groove depth of groove 11-1 is greater than the height of arc-shaped protrusion 9-1. During closing, the moving end resistor contact 11 moves rapidly toward the stationary end resistor contact 9, causing an impact. The groove depth of groove 11-1 is designed to be greater than the height of arc-shaped protrusion 9-1 to provide some protection for the arc-shaped protrusion 9-1 during contact impact, preventing misalignment between the arc-shaped protrusion 9-1 and groove 11-1 due to component tolerances, assembly tolerances, and arc-extinguishing chamber vibration, thus avoiding deformation of the arc-shaped protrusion 9-1 caused by a violent impact. The arc-shaped protrusion 9-1 and the front end face of the stationary end resistor contact 9, as well as the groove 11-1 and the front end face of the moving end resistor contact 11, are transitioned by arc surfaces to ensure that the groove opening of groove 11-1 is not easily deformed during contact impact. During closing, if... Figure 3 As shown, the arc-shaped protrusion 9-1 at the front end of the stationary resistor contact 9 is inserted into the groove 11-1 at the front end of the moving resistor contact 11, forming a conductive contact between the two resistor contacts. The contact area is the transition point of the arc surfaces of the two resistor contacts. This structural design ensures stable and reliable contact between the two resistor contacts, reduces the risk of eccentricity and lateral stress, and minimizes the generation of metallic foreign objects. Both the stationary resistor contact 9 and the moving resistor contact 11 have threads machined at their tails, and both the stationary contact rod 5 and the moving contact rod 13 have threaded holes at their front ends. The stationary resistor contact 9 and the moving resistor contact 11 are respectively threaded into the threaded holes at the front ends of the stationary contact rod 5 and the moving contact rod 13.

[0032] like Figure 1As shown, the damping structure includes a piston cylinder 4 and a piston 2 disposed within the piston cylinder 4. The piston 2 is fixedly connected to the stationary contact rod 5. A closed air chamber is formed inside the piston cylinder 4 behind the piston 2. The front end of the piston cylinder 4, near the guide cylinder 6, is an open structure. Multiple guide rods 3 are provided inside the piston cylinder 4, parallel to its axis and fixedly connected to it. All guide rods 3 are evenly spaced circumferentially. The piston 2 is movably mounted on each guide rod 3, with an air gap between it and each guide rod 3. The front end of each guide rod 3 is fixedly connected to the rear end of the guide cylinder 6. Both ends of each guide rod 3 are threaded. The front end of each guide rod 3 is threaded to the guide cylinder 6, and the rear end passes through the bottom of the piston cylinder 4 and is screwed with a nut to achieve a fixed connection with the piston cylinder 4. The guide rods 3 guide the piston 2, ensuring reliable sealing between the piston 2 and the piston cylinder 4, and also further enhancing the guiding effect on the stationary contact rod 5. The stationary contact assembly also includes a return spring 7 for applying an elastic force to the stationary resistor contact 9 to force it to reset. During the closing process, after the moving resistor contact 11 strikes the stationary resistor contact 9, it continues to move forward. The stationary resistor contact 9 is subjected to the pressing force of the moving resistor contact 11. The stationary resistor contact 9, together with the stationary contact rod 5 and the piston 2, moves backward. The return spring 7 is compressed and stores elastic force. The pressure inside the sealed air chamber increases due to compression and is then balanced through the air gap. During the opening process, the moving resistor contact 11 moves backward rapidly with the transmission system. The pressing force of the moving resistor contact 11 on the stationary resistor contact 9 disappears. The stationary resistor contact 9 and the stationary contact rod 5 are reset under the action of the return spring 7. The damping structure can slow down the reset action of the stationary contact rod 5, so that the moving resistor contact 11 and the stationary resistor contact 9 separate more quickly, and the resistor break opens before the main break.

[0033] The stationary end shield 8 is clamped between the stationary end resistor contact 9 and the stationary end contact rod 5. The return spring 7 is a compression spring located between the stationary end shield 8 and the guide cylinder 6. The compression spring is fitted onto the stationary end contact rod 5. The front end of the guide cylinder 6 has a receiving groove, and the rear end of the compression spring extends into the receiving groove and presses against the bottom surface of the groove. This design has several advantages: first, the compression spring is easy to install, as it can be directly fitted onto the stationary end contact rod 5; second, the stationary end contact rod 5 limits the compression spring in the circumferential direction, preventing it from tilting during extension and retraction, thus ensuring that it applies a uniform return elastic force to the stationary end resistor contact 9; and third, the rear end of the compression spring extending into the receiving groove and pressing against the bottom surface of the groove reduces the overall length and size of the stationary end contact assembly.

[0034] The stationary contact rod 5 has a reduced-diameter section at its tail, forming a rearward-facing stepped surface. The piston 2 is fitted onto the reduced-diameter section, which has an external thread. A clamping nut 10 is threaded onto the portion of the reduced-diameter section extending beyond the piston 2, pressing the piston 2 against the stepped surface, thus achieving relative fixation between the piston 2 and the stationary contact rod 5. The piston 2 and the stationary contact rod 5 are detachably connected, facilitating replacement of the piston 2 after prolonged use. The piston cylinder 4 has a clearance groove 4-1 on its inner bottom to allow the rear end of the stationary contact rod 5 to pass. When the stationary contact rod 5 moves backward, its tail end can extend into the clearance groove 4-1. Utilizing the space in the clearance groove 4-1, the overall length of the piston cylinder 4 and the stationary contact rod 5 can be reduced while maintaining the same movement distance, further minimizing the size of the stationary contact assembly.

[0035] A shielding component 1 is also provided at the rear end of the piston cylinder 4. The piston cylinder 4 has a threaded hole, and the shielding component 1 is fixedly connected to the piston cylinder 4 by bolts. The stationary contact assembly is electrically connected to the stationary main contact. The purpose of the shielding component 1 here is to shield the electric field at the left end of the stationary contact assembly to ensure the overall insulation performance of the arc-extinguishing chamber.

[0036] This invention designs the structure of the resistor contacts, with the front center of the stationary resistor contact 9 and the moving resistor contact 11 designed as a convex-concave structure. In the prior art, the front center of the stationary resistor contact 9 and the moving resistor contact 11 are both planar structures. Electric field simulation analysis and experimental verification were performed on the two contact structures during the circuit breaker closing process. It was found that the resistor break point of the convex-concave structure reaches the breakdown field strength earlier than that of the resistor break point of the existing resistor contacts. Moreover, the resistor break point of the convex-concave structure reaches the breakdown field strength earlier than the main break point, thereby ensuring that the resistor break point can break down before the main break point, and the closing resistor is effectively connected to the main circuit, limiting overvoltage.

[0037] In this invention, the front center of the stationary and moving resistor contacts has a convex-concave structure. When the circuit is closed, the resistor contacts are not easily deformed and are less likely to produce metal foreign objects. The resistor contacts are less likely to experience lateral stress during the closing process, making them more stable and reliable under electrical contact and mechanical operation.

[0038] Of course, the present invention is not limited to the embodiments described above.

[0039] For example, in another embodiment, the groove at the front end of the moving end resistor contact has the same shape and size as the arc-shaped protrusion at the front end of the stationary end resistor contact, and after the circuit is closed, the outer surface of the arc-shaped protrusion fits perfectly with the groove wall.

[0040] For example, in another embodiment, a simpler stationary contact assembly is provided. The stationary contact assembly includes a contact seat with a mounting cavity. The rear end of the contact seat is closed. A stationary contact rod is sealed and movably mounted in the mounting cavity. A piston is provided on the stationary contact rod. The piston is sealed and cooperates with the cavity wall of the mounting cavity to form an air cavity behind the piston.

[0041] For example, in another embodiment, the reset spring is fitted onto the stationary contact rod, the front end of the guide cylinder does not have a receiving groove, and the rear end of the compression spring is directly pressed against the front end surface of the guide cylinder.

[0042] For example, in another embodiment, the stationary contact rod does not have a necking section at the tail end. A limit ring is welded to the stationary contact rod near the rear end. The piston is fitted onto the stationary contact rod. An external thread section is provided on a section of the rod at the tail end of the stationary contact rod. A clamping nut is screwed onto the external thread section to press the piston against the limit ring.

[0043] For example, in another embodiment, there is no clearance groove on the inner bottom of the piston cylinder to avoid the tail of the stationary contact rod. In this case, under normal conditions, the tail of the stationary contact rod needs to leave a sufficient distance between itself and the inner bottom of the piston cylinder, and the overall length of the stationary contact assembly will increase slightly.

[0044] The present invention also provides an embodiment of a closing resistor contact assembly for a circuit breaker, the specific structure of which is the same as that of the closing resistor contact assembly in the circuit breaker embodiment described above, and will not be repeated here.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A closing resistor contact assembly for a circuit breaker, comprising a stationary contact assembly and a moving contact assembly, wherein the stationary contact assembly includes a stationary resistor contact and a stationary contact rod connected to the stationary resistor contact, and the moving contact assembly includes a moving resistor contact and a moving contact rod connected to the moving resistor contact, characterized in that: Both the stationary and moving resistor contacts have rounded front faces, with one of them having an arc-shaped protrusion at the center of its front end, and the other having a groove at the center of its front end for the arc-shaped protrusion to be inserted and make conductive contact with it when the circuit is closed.

2. The closing resistor contact assembly for a circuit breaker according to claim 1, characterized in that: The groove depth is greater than the height of the arc-shaped protrusion.

3. The closing resistor contact assembly for a circuit breaker according to claim 1, characterized in that: The arc-shaped protrusion and the front face of the contact it belongs to, as well as the groove and the front face of the contact it belongs to, are all transitioned by a circular arc surface.

4. The closing resistor contact assembly for a circuit breaker according to any one of claims 1-3, characterized in that: The stationary contact assembly also includes a guide cylinder and a damping structure. The stationary contact rod is guided and movably inserted into the guide cylinder. The stationary resistance contact is connected to the front end of the stationary contact rod. The damping structure includes a piston cylinder and a piston disposed in the piston cylinder. The piston is fixedly connected to the stationary contact rod. The piston cylinder has a guide rod that is parallel to the piston cylinder axis and fixedly connected to the piston cylinder. The piston is movably inserted into the guide rod and has an air gap between it and the guide rod. The guide rod is fixedly connected to the rear end of the guide cylinder. The end of the piston cylinder near the guide cylinder is an open structure. The stationary contact assembly also includes a return spring for applying an elastic force to the stationary resistance contact to force it to reset.

5. The closing resistor contact assembly for a circuit breaker according to claim 4, characterized in that: A stationary end shield is sandwiched between the stationary end resistor contact and the stationary end contact rod, and the reset spring is a compression spring disposed between the stationary end shield and the guide cylinder.

6. The closing resistor contact assembly for a circuit breaker according to claim 5, characterized in that: The compression spring is mounted on the stationary contact rod. The front end of the guide cylinder is provided with a receiving groove, and the rear end of the compression spring extends into the receiving groove and presses against the bottom surface of the receiving groove.

7. The closing resistor contact assembly for a circuit breaker according to claim 4, characterized in that: The stationary contact rod has a reduced diameter section at its tail, forming a rearward stepped surface on the stationary contact rod. The piston is fitted onto the reduced diameter section, and a clamping nut is threaded onto the reduced diameter section to press the piston against the stepped surface.

8. The closing resistor contact assembly for a circuit breaker according to claim 7, characterized in that: The piston cylinder has a clearance groove on the bottom of the cylinder to avoid the tail of the stationary contact rod.

9. The closing resistor contact assembly for a circuit breaker according to claim 4, characterized in that: A shield is provided at the rear end of the piston cylinder.

10. A circuit breaker, comprising an arc-extinguishing chamber, wherein the arc-extinguishing chamber is provided with a main circuit and a resistance circuit connected in parallel, the main circuit comprising a moving main contact and a stationary main contact, and the resistance circuit comprising a closing resistor contact assembly and a closing resistor, characterized in that: The closing resistor contact assembly is the circuit breaker closing resistor contact assembly as described in any one of claims 1-9.

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