A molded case circuit breaker with a current limiting contact system

Abstract

The utility model discloses a kind of plastic shell circuit breaker with current-limiting contact system, including operating mechanism, current-limiting contact mechanism, arc extinguishing mechanism, release, shell composition, operating mechanism is connected with current-limiting contact system, current-limiting contact mechanism is composed of conducting plate, static contact, shaft, contact spring, spring seat, arc separation piece, insulating gasket, contact spring one end is cooperated with static contact, the other end is on spring seat, arc separation piece is installed in static contact lower portion, the upper portion of conducting plate, insulating gasket is arranged in static contact lower portion, the upper portion of conducting plate, static contact one end and contact spring elastic contact, the other end is hinged and connected on shaft.The utility model contact spring provides certain contact pressure, can ensure good electrical contact between moving and static contact during normal operation, reduce contact resistance, reduce heating.When fault large current appears in circuit, the counterforce of contact spring helps to quickly separate contact, improve the breaking speed of contact, thereby enhance the breaking capacity to large current, realize current-limiting function.

Description

Technical Field

[0001] This utility model relates to the field of electrical equipment technology, specifically to a plastic-cased circuit breaker with a current-limiting contact system. Background Technology

[0002] A molded case circuit breaker (MCCB) is a switching structure that automatically cuts off the current when the current exceeds the trip setting. Existing MCBs with current-limiting contact mechanisms have several drawbacks: In terms of current-limiting performance, under extreme short-circuit faults, such as excessively large short-circuit currents or short-circuit points close to the power source, they may not effectively limit the current peak, providing insufficient protection for downstream equipment. Furthermore, the stability of the current-limiting effect is poor under different operating conditions. Arc-extinguishing capacity is limited; when interrupting large currents, the arc may exceed the arc-extinguishing system's handling capacity, causing arc reignition, and the resulting high-temperature, high-pressure gases may damage components. Mechanical components of the operating mechanism are prone to wear, deformation, or jamming; the electric operating mechanism is susceptible to control failure due to power fluctuations, affecting the normal opening and closing of contacts. In addition, the plastic casing has poor heat dissipation; during high-current operation, internal heat accumulates, accelerating component aging, reducing insulation performance, and affecting the overall performance and lifespan of the circuit breaker. Utility Model Content

[0003] The technical problem to be solved is to address the problems existing in the prior art. The purpose of this utility model is to provide a plastic-cased circuit breaker with a current-limiting contact system.

[0004] Technical solution: To solve the above problems, the present invention adopts the following technical solution.

[0005] A plastic-cased circuit breaker with a current-limiting contact system comprises an operating mechanism, a current-limiting contact mechanism, an arc-extinguishing mechanism, a trip unit, and a housing. The operating mechanism is connected to the current-limiting contact system and achieves the closing and opening of the contacts through operation. The arc-extinguishing system is located adjacent to the current-limiting contact mechanism. The trip unit is connected to the operating mechanism. The housing serves as an integral protective component, encapsulating the operating mechanism, the current-limiting contact system, the arc-extinguishing system, and the trip unit. The current-limiting contact mechanism consists of a conductive plate, a stationary contact, a shaft, a contact spring, a spring seat, an arc-blocking plate, and an insulating gasket. One end of the contact spring engages with the stationary contact, and the other end rests against the spring seat. The arc-blocking plate is installed at the lower part of the stationary contact and the upper part of the conductive plate. The insulating gasket is arranged at the lower part of the stationary contact and the upper part of the conductive plate. One end of the stationary contact is in elastic contact with the contact spring, and the other end is hinged to the shaft.

[0006] The conductive plate and stationary contact described in this utility model are horizontally arranged "U" shaped structures. The conductive plate is disposed at the lower part of the stationary contact and is in contact with the end of the stationary contact.

[0007] The present invention provides two stationary contacts, which are arranged in parallel and fixed together.

[0008] The working principle of this utility model is as follows: During normal operation, the operating mechanism actuates, driving the current-limiting contact mechanism to close the moving and stationary contacts, thus completing the circuit. At this time, the contact spring is compressed, providing contact pressure to the moving and stationary contacts to ensure good conductivity. The three stationary contacts are connected by a shaft, stably transmitting current in the three-phase circuit. The trip unit does not operate if the circuit parameters are normal. When a short-circuit fault occurs, the short-circuit current generates a strong magnetic field. Due to the special structure of the three stationary contacts connected by a shaft, the magnetic field causes the moving and stationary contacts to separate in advance, breaking the circuit before the current reaches its peak value, thus achieving the current-limiting function. An electric arc is generated at the moment the contacts break, and the adjacent arc-extinguishing mechanism comes into play. The arc-isolating plate first isolates and guides the arc, and the components in the arc-extinguishing mechanism divide the arc into short arcs to accelerate its extinguishing, preventing the arc from damaging the components. At the same time, the trip unit detects an abnormally large current (exceeding the set threshold) and quickly triggers the action, acting on the operating mechanism to keep it in the open state and prevent the contacts from closing on their own. The outer casing provides mechanical protection and electrical insulation for all internal components throughout the entire process. After the fault is cleared, the operable mechanism is reset to prepare for the next circuit switching and protection.

[0009] The beneficial effects of this invention are as follows: The contact spring provides a certain contact pressure, ensuring good electrical contact between the moving and stationary contacts during normal operation, reducing contact resistance and heat generation. When a large current fault occurs in the circuit, the reaction force of the contact spring helps to quickly separate the contacts, increasing the breaking speed and thus enhancing the breaking capacity for large currents, achieving current limiting. For example, when a short-circuit current occurs, the contacts can quickly separate, limiting the magnitude of the short-circuit current and protecting the circuit and equipment.

[0010] This utility model relates to an arc-blocking plate installed near the contacts. It effectively confines the electric arc within a certain space, preventing it from spreading and damaging other components. Simultaneously, the arc-blocking plate can segment and cool the arc, accelerating its extinguishing and improving the reliability of the contact mechanism. For example, in AC circuits, the arc-blocking plate can divide the arc into multiple short arcs, utilizing the near-cathode effect of these short arcs to make them easier to extinguish. Attached Figure Description

[0011] Figure 1 is a schematic diagram of the structure of this utility model.

[0012] The components in the diagram are named as follows: 1. Conductive plate; 2. Stationary contact; 3. Shaft; 4. Contact spring; 5. Spring seat; 6. Arc blocking plate; 7. Insulating pad. Detailed Implementation

[0013] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0014] A plastic-cased circuit breaker with a current-limiting contact system comprises an operating mechanism, a current-limiting contact mechanism, an arc-extinguishing mechanism, a trip unit, and a housing. The operating mechanism is connected to the current-limiting contact system and achieves the closing and opening of the contacts through operation. The arc-extinguishing system is located adjacent to the current-limiting contact mechanism. The trip unit is connected to the operating mechanism. The housing serves as an integral protective component, encapsulating the operating mechanism, the current-limiting contact system, the arc-extinguishing system, and the trip unit. The current-limiting contact mechanism consists of a conductive plate 1, a stationary contact 2, a shaft 3, a contact spring 4, a spring seat 5, an arc-blocking plate 6, and an insulating gasket 7. One end of the contact spring 4 engages with the stationary contact 2, and the other end rests against the spring seat 5. The arc-blocking plate 6 is installed at the lower part of the stationary contact 2 and the upper part of the conductive plate 1. The insulating gasket 7 is arranged at the lower part of the stationary contact 2 and the upper part of the conductive plate 1. One end of the stationary contact 2 is in elastic contact with the contact spring 4, and the other end is hinged to the shaft 3.

[0015] The contact spring 4 of this utility model is pre-compressed to a set length by the spring seat to provide contact pressure when the contacts are closed; when the short circuit current generates an electric repulsive force, the spring must meet the dynamic characteristic requirements (such as stiffness coefficient and compression stroke) to ensure that the contacts can separate quickly and limit the rate of current rise.

[0016] In this invention, the stationary contact 2 is hinged to the shaft via a copper alloy bushing. Both ends of the shaft 3 are fixed to the side wall of the outer casing. High-temperature resistant grease is applied to the hinge joint to ensure that the stationary contact can rotate flexibly around the shaft and that the contact resistance is stable during the opening and closing process. The arc-extinguishing chamber of this invention is located directly above the opening and closing path of the stationary contact, and the top of the arc-isolating plate extends to the entrance of the arc-extinguishing chamber to ensure that the electric arc can be quickly introduced into the arc-extinguishing grid plate group when the circuit is opened; the bottom plate of the arc-extinguishing chamber has a flow guide groove, which forms a coordinated airflow channel with the arc-isolating plate to accelerate the extinguishing of the electric arc.

[0017] The armature of the thermomagnetic trip unit of this utility model is connected to the locking assembly of the operating mechanism through an insulated push rod. When there is an overload or short circuit, the trip unit drives the locking to release, and the operating mechanism quickly disconnects the contact system through a four-bar linkage.

[0018] In this invention, current flows into the conductive plate from the inlet end, passes through the stationary contact, the moving contact, and the flexible connection to the outlet end; during a short circuit, the electric repulsion force causes the stationary contact to rotate upward around the axis, separating it from the moving contact, and the electric arc enters the arc-extinguishing chamber under the guidance of the arc-isolating plate.

Claims

1. A plastic-cased circuit breaker with a current-limiting contact system, comprising an operating mechanism, a current-limiting contact mechanism, an arc-extinguishing mechanism, a trip unit, and a housing, wherein the operating mechanism is connected to the current-limiting contact system and achieves the closing and opening of the contacts through operation; the arc-extinguishing system is disposed adjacent to the current-limiting contact mechanism; the trip unit is connected to the operating mechanism; and the housing, as an integral protective component, encapsulates the operating mechanism, the current-limiting contact system, the arc-extinguishing system, and the trip unit within it, characterized in that: The current-limiting contact mechanism consists of a conductive plate, a stationary contact, a shaft, a contact spring, a spring seat, an arc-blocking plate, and an insulating gasket. One end of the contact spring engages with the stationary contact, and the other end rests against the spring seat. The arc-blocking plate is installed at the lower part of the stationary contact and the upper part of the conductive plate. The insulating gasket is arranged at the lower part of the stationary contact and the upper part of the conductive plate. One end of the stationary contact is in elastic contact with the contact spring, and the other end is hinged to the shaft.

2. A plastic-cased circuit breaker with a current-limiting contact system according to claim 1, characterized in that: The conductive plate and the stationary contact are horizontally arranged in a "U" shape. The conductive plate is located at the bottom of the stationary contact and is in contact with the end of the stationary contact.

3. A plastic-cased circuit breaker with a current-limiting contact system according to claim 1, characterized in that: Two stationary contacts are provided, which are arranged in parallel and fixed together.

4. A plastic-cased circuit breaker with a current-limiting contact system according to claim 1, characterized in that: The arc-blocking plate is made of high thermal conductivity insulating ceramic material and is fixed in the U-shaped groove of the conductive plate by a slot.

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