Circuit protection device integrating current limiting and backup fusing functions and short circuit protection method

Abstract

The invention provides a circuit protection device integrating current limiting and backup fusing functions and a short circuit protection method. The protection device comprises a circuit breaker body; the current limiting protection structure is connected in series with the circuit breaker body; the current-limiting protection structure comprises a current-sensitive current-limiting element made of a conductive material with a positive temperature coefficient characteristic; the resistance value of the current-sensitive current-limiting element is nonlinearly increased within a preset time range under the action of short-circuit current so as to limit the current, so that the circuit breaker body is protected, and when the circuit breaker body is not broken, the current-sensitive current-limiting element is physically fused due to overheating so as to cut off the circuit. Through series connection of the current sensitive type current limiting element, a dual protection mechanism of first current limiting protection and then fusing backup is constructed, so that the miniature circuit breaker with low cost and low breaking capacity can reliably break an extremely large short-circuit current which is far beyond its own capacity.

Description

Technical Field

[0001] This application relates to the field of electrical protection equipment technology, and in particular to a circuit protection device and short-circuit protection method that integrates current limiting and backup fuse functions. Background Technology

[0002] Circuit breakers are one of the most important protective devices in power systems. One of their core parameters is rated short-circuit breaking capacity, which is the maximum short-circuit current that can be safely interrupted. In traditional cabinet power distribution systems, the transformer capacity is relatively small (e.g., 50kW), the system impedance is relatively large, and the short-circuit current is usually below 10kA. Conventional miniature circuit breakers (with breaking capacities typically ranging from 6kA to 10kA) are sufficient to handle this.

[0003] However, with the rapid development of high-power applications such as artificial intelligence and big data centers, the power density of single cabinets has increased dramatically, and transformer capacity can reach 200kW or even higher. With the system voltage (e.g., 220V) remaining constant, this increased capacity means a decrease in system impedance, leading to a sharp increase in potential short-circuit current, reaching 25kA to 50kA. This far exceeds the breaking capacity of ordinary miniature circuit breakers.

[0004] Currently, there are two main solutions to this problem: one is to use high breaking capacity circuit breakers. Circuit breakers with a breaking capacity of 50kA or more are bulky and expensive, which contradicts the trend of miniaturization and cost reduction in server racks. The other is to use fuses. Although fuses have high breaking capacity and low cost, they have disadvantages such as needing to be manually replaced after activation, troublesome maintenance, and potential delays in protection characteristics. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a circuit protection device and short-circuit protection method that integrates current limiting and backup fuse functions. By connecting a circuit breaker in series with a special current limiting protection structure, rapid current limiting and backup fuse protection can be achieved under extreme short-circuit conditions.

[0006] To achieve the above objectives, this application provides a circuit protection device integrating current limiting and backup fuse functions, comprising: Circuit breaker body; A current-limiting protection structure is connected in series with the circuit breaker body; The current limiting protection structure includes a current-sensitive current limiting element made of a conductive material with a positive temperature coefficient. Under the action of short-circuit current, the resistance value of the current-sensitive current-limiting element increases nonlinearly within a preset time range to limit the current, thereby protecting the circuit breaker body. If the circuit breaker body fails to disconnect, the current-sensitive current-limiting element will physically melt due to overheating to cut off the circuit.

[0007] Furthermore, it also includes: a power input terminal and a load output terminal, wherein the power input terminal, the current limiting protection structure, the circuit breaker body, and the load output terminal are connected in series to form a protection branch of the main circuit; The power input terminal is used to connect to the power distribution power supply, and the load output terminal is used to connect to the power system or equipment that needs protection, so that the current limiting protection structure and the circuit breaker body are connected in series in the protected circuit.

[0008] Furthermore, the conductive material is aluminum or an aluminum alloy.

[0009] Furthermore, the aluminum alloy is 5052 aluminum alloy.

[0010] Furthermore, the current-sensitive current-limiting element is a metal wire with a length of 4.74m and a diameter of 2.1mm.

[0011] Furthermore, the current-sensitive current-limiting element has a heat generation power of less than 50W under rated operating current.

[0012] Furthermore, the current-sensitive current-limiting element is configured to limit the current to below 2000A within 0.01 seconds after a short circuit occurs.

[0013] Furthermore, the current-sensitive current-limiting element is configured to melt within 0.05 seconds if the circuit breaker fails to trip.

[0014] Furthermore, the current-sensitive current-limiting element is arranged in a coiled, bent, or spiral shape within the insulating housing of the circuit breaker body or in an insulating module independent of the circuit breaker body.

[0015] On the other hand, this application also provides a short-circuit protection method, including the following steps: A current-sensitive current-limiting element is connected in series in the circuit of the circuit breaker; By utilizing the characteristic of the current-sensitive current-limiting element that rapidly heats up and increases resistance when a short circuit occurs, the short-circuit current is limited to a safe range that it can disconnect before the circuit breaker operates. If the circuit breaker fails to disconnect, a continuous set current is used to melt the current-sensitive current-limiting element, thus achieving the final disconnection of the circuit.

[0016] The circuit protection device with integrated current limiting and backup fuse functions provided in this application constructs a dual protection mechanism of first current limiting protection and then backup fuse by connecting current-sensitive current limiting elements in series. This enables low-cost, low-breaking-capacity miniature circuit breakers to reliably interrupt extremely large short-circuit currents far exceeding their own capacity, ultimately achieving high breaking capacity, high safety and low cost of the system.

[0017] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the present application and form part of the specification. Together with the embodiments of the present application, they serve to explain the present application but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the circuit protection device with integrated current limiting and backup fuse functions according to an embodiment of this application; Figure 2 This is a short-circuit protection method according to an embodiment of this application. Detailed Implementation

[0019] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0020] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this application. It should be understood that the drawings and embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0021] The term "comprising" and its variations as used in this application are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0022] It should be noted that the terms "first" and "second" may be used in this application only to distinguish different devices, components or parts, and are not used to define the order of functions performed by these devices, components or parts or their interdependence.

[0023] It should be noted that the terms "one" and "more" used in this application are illustrative rather than restrictive, and those skilled in the art should understand that, unless explicitly stated otherwise in the context, they should be understood as "one or more". "More" should be understood as two or more.

[0024] In the description of this application, the circuit breaker body 1 refers to a standardized circuit breaker module known in the art, possessing basic switching and protection functions. It typically includes, but is not limited to, the following core components: a contact system (including moving and stationary contacts) for connecting and disconnecting circuits, an arc-extinguishing device (such as an arc-extinguishing chamber) for extinguishing the arc generated during disconnection, an operating mechanism for realizing closing-holding-opening operations, and at least one trip unit (e.g., a thermal trip unit for overload protection or a magnetic trip unit for short-circuit protection), all of which are encapsulated within an insulating housing.

[0025] The "breaking" function of a circuit breaker refers to the process by which, in the event of a fault (such as overload or short circuit), the trip unit drives the operating mechanism to forcibly separate the moving and stationary contacts to interrupt the current. The electric arc generated during this process is introduced into the arc-extinguishing chamber and rapidly extinguished through cooling, elongation, and splitting, ultimately achieving safe isolation of the circuit. This is the core protection function of a circuit breaker.

[0026] It should be noted that the inventive point and innovation of this application do not lie in any change or improvement to the internal structure of the circuit breaker body 1. Its specific structure, working principle, and manufacturing method are not within the scope of protection sought in this application. The core of this application lies in introducing an independent current-limiting protection structure 2 in series with the circuit breaker body 1 to construct a completely new device with high breaking capacity and a dual protection mechanism. Therefore, any technical solution that utilizes this core concept to combine a current-limiting element with a standard circuit breaker body with breaking capacity falls within the protection scope of this application.

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0028] Example 1 In the embodiments of this application, a circuit protection device integrating current limiting and backup fuse functions is provided, comprising: a circuit breaker body; a current limiting protection structure connected in series with the circuit breaker body; the current limiting protection structure includes a current-sensitive current limiting element made of a conductive material with a positive temperature coefficient; under the action of a short-circuit current, the resistance value of the current-sensitive current limiting element increases nonlinearly within a preset time range to limit the current, thereby protecting the circuit breaker body, and when the circuit breaker body fails to trip, the current-sensitive current limiting element undergoes physical melting due to overheating to completely cut off the circuit.

[0029] Figure 1 The following is a schematic diagram of the electrical connection principle of a circuit protection device integrating current limiting and backup fuse functions according to an embodiment of this application. Figure 1 The circuit protection device with integrated current limiting and backup fuse functions of this application is described in further detail.

[0030] The circuit protection device integrating current limiting and backup fuse functions according to this application embodiment includes: a circuit breaker body 1, a current limiting protection structure 2, a power input terminal 3, and a load output terminal 4. The power input terminal 3, the current limiting protection structure 2, the circuit breaker body 1, and the load output terminal 4 are connected in series to form a protection branch of the main circuit. The current limiting protection structure 2 is a current-sensitive current limiting element. Its core characteristic is that when a large short-circuit current passes through it, it heats up rapidly due to its own resistance, causing its resistance value to increase sharply, thereby limiting the short-circuit current. The current-sensitive current limiting element is made of a conductive material with a positive temperature coefficient. Under the action of a short-circuit current, its resistance value increases rapidly and non-linearly to limit the current, thereby protecting the circuit breaker body from damage by a short-circuit current exceeding its breaking capacity. Furthermore, if the circuit breaker body fails to trip in time due to a fault, this current-sensitive current limiting element physically fuses due to overheating, serving as a final protection measure to completely disconnect the circuit.

[0031] The conductive material with a positive temperature coefficient refers to a material whose resistivity increases significantly with increasing temperature. Under normal operation, it has low resistance and low power consumption; when subjected to a short-circuit high current, the material rapidly heats up due to Joule heating, causing a sharp increase in resistance, thereby strongly limiting the fault current. Using this as the current-limiting element in this application provides both sensitive response and self-protection.

[0032] The circuit protection device integrating current limiting and backup fuse functions of this application serves as the core protection element, connected in series in the main circuit of the protected circuit. The power input terminal 3 is connected to the upstream power distribution source (such as the 220V busbar in a server rack) to introduce electrical energy. The load output terminal 4 is connected to the downstream power system or equipment requiring protection (such as a group of AI servers or a power distribution unit in a server rack). Its usage is the same as a conventional circuit breaker: installed in a distribution box or equipment inlet. Once a short circuit occurs on the downstream load side (such as inside a server), the huge current will first flow through the current limiting protection structure 2, which quickly limits the current to ensure the circuit breaker body 1 can safely disconnect. If the circuit breaker body 1 fails, the current limiting protection structure 2 will automatically fuse, forming a final safety barrier, thereby protecting the entire downstream circuit and the upstream power grid from impact.

[0033] In some exemplary embodiments, the conductive material is made of, for example, aluminum or an aluminum alloy, more preferably 5052 aluminum alloy.

[0034] In some exemplary embodiments, the current-sensitive current-limiting element is a 5052 aluminum alloy wire with a length of about 4.74m and a diameter of about 2.1mm.

[0035] In some exemplary embodiments, the current-limiting protection structure 2 is directly installed inside the insulating housing of the circuit breaker body 1. Specifically, structurally, a 4.74m long aluminum alloy wire is tightly wound into a spiral coil and installed in an empty area inside the insulating housing using non-conductive clamps. To optimize space utilization, the spiral coil can be laid flat in an empty planar area inside the housing or coiled three-dimensionally along the height of the housing. The spiral coil is fixed inside the housing by multiple non-conductive clamps, ensuring sufficient electrical clearance and creepage distance between it and other conductive components (such as the contact system, trip unit) and the metal housing (if any) inside the circuit breaker body 1. Electrically, one end of the current-limiting protection structure 2 is connected to the internal contact of the input terminal of the circuit breaker body 1 by welding or screws, and the other end is connected to the inlet terminal of the moving contact of the circuit breaker body 1, thereby achieving close series connection with the circuit breaker body 1.

[0036] Furthermore, the coiled design itself creates natural airflow channels between the turns, which is beneficial for heat dissipation during normal operation (27.1W power consumption). In addition, highly thermally conductive insulating materials (such as thermally conductive silicone or alumina ceramic sheets) can be filled around the coil to conduct heat to the housing, further improving heat dissipation efficiency.

[0037] This embodiment, based on an exemplary design objective (rated voltage 220V, rated current 20A, target breaking capacity 50kA), elaborates in detail the calculation and selection process of key parameters for the current-sensitive current-limiting element (i.e., current-limiting protection structure 2) to verify that it meets the following three core requirements: 1) Under a rated current of 20A, its steady-state heat dissipation power should be less than 50W; 2) In the event of a short circuit, it can limit the current to below 2000A within 0.01 seconds; 3) When the circuit breaker fails, it can reliably melt and completely disconnect the circuit within 0.05 seconds.

[0038] First, the length L of the current-limiting element is determined based on the fuse requirements.

[0039] To ensure that the circuit breaker breaks within the set fusing time (e.g., t_f = 0.05s) in backup protection, the energy absorbed by the current-limiting element within this time must be sufficient to heat it from room temperature (e.g., 25°C) to its melting point (T_m). The energy required for fusing is described by the following heat balance equation: P_avg×t_f=m×c×ΔT_m; Where P_avg is the average heating power from room temperature to melting point, m is the mass, c is the specific heat capacity, and ΔT_m is the temperature rise from room temperature to melting point.

[0040] The average power P_avg is approximated by averaging the power of the current-limiting element at room temperature (P_25) and the power at melting point (P_m). Combining Ohm's law with the resistance of the current-limiting element at room temperature (R_25 = ρ × L / A, where ρ is resistivity, A is cross-sectional area, and L is length) and the temperature coefficient of resistance formula (R_T = R_25 × [1 + α × (T - 25)], where α is the temperature coefficient of resistance), the derivation process is as follows: P_25=U² / R_25; P_m=U² / R_m=U² / (R_25×(1+α×(T_m-25))); P_avg=(P_25+P_m) / 2=(U² / R_25+U² / (R_25×(1+α×(T_m-25)))) / 2=1 / 2×U² / R_25×(1+1 / (1+α×(T_m-25))); Where U is the operating voltage and R_m is the resistance at the melting point.

[0041] Substituting the mass m = ρ_m × A × L and R_25 = ρ × L / A into the heat balance equation, we get: (1 / 2)×(U² / R_25)×(1+1 / (1+α×(T_m-25))))×t_f=ρ_m×A×L×c×ΔT_m; (1 / 2)×(U²×A / (ρ×L))×(1+1 / (1+α×(T_m-25))))×t_f=ρ_m×A×L×c×ΔT_m; After simplification, the formula for calculating the critical length L that determines the melting time is obtained: L²=(U²×t_f×(1+1 / (1+α×(T_m-25)))) / (2×ρ×ρ_m×c×ΔT_m).

[0042] The calculation formula shows that the melting length L of the current limiting element depends mainly on the material properties (ρ, density ρ_m,c,T_m,α), and is independent of the cross-sectional area A.

[0043] Pure aluminum was initially selected as the candidate material, with the following parameters: resistivity ρ = 2.82 × Ω·m, density ρ_m = 2.70 × 10³ kg / m³, specific heat capacity c = 897 J / (kg·K), temperature coefficient of resistance α = 0.00429 / ℃, melting point T_m = 660℃. Calculate the temperature rise ΔT_m = 660 - 25 = 635℃.

[0044] Substituting into the above calculation formula, we get: L=√((220²×0.05×(1+1 / (1+0.00429×(660-25)))) / (2×2.82× ×2.70×10³×897×635))≈5.95(m). In the embodiments of this application, “√(·)” indicates taking the square root.

[0045] The calculated length L is approximately 5.95 meters, which ensures that if the circuit breaker fails to trip in time, the current-limiting protection structure 2 can melt within 0.05 seconds, cutting off the circuit and preventing further damage. However, this length presents significant challenges in terms of structural layout.

[0046] To reduce component size, 5052 aluminum alloy with higher resistivity was selected, with the following parameters: resistivity ρ = 4.95 × Ω·m, density ρ_m=2.68×10³kg / m³, specific heat capacity c=897J / (kg·K), temperature coefficient of resistance α=0.00429 / °C, melting point T_m=607℃. Calculate the temperature rise ΔT_m=607-25=582℃.

[0047] Substituting into the calculation formula, we get: L=√((220²×0.05×(1+1 / (1+0.00429×(607-25)))) / (2×4.95× ×2.68×10³×897×582))≈4.74(m).

[0048] Therefore, 5052 aluminum alloy was ultimately chosen, with the length L of its current-limiting element designed to be approximately 4.74 meters. This ensures that if the circuit breaker fails to trip in time, the current-limiting protection structure 2 can melt within 0.05 seconds, cutting off the circuit and preventing further damage. At the same time, the structural layout is significantly less complex.

[0049] Secondly, the cross-sectional area A is determined based on the flow restriction requirements.

[0050] After determining the length L=4.74m, it is necessary to calculate the temperature rise within 0.01 seconds after the short circuit occurs, and calculate the cross-sectional area A required to limit the current to below 2000A based on the resistance value at this temperature.

[0051] First, calculate the approximate temperature rise ΔT over 0.01 seconds (t_s). The formula for calculating the temperature change ΔT is: ΔT = (U × I_avg × t_s) / (m × c). Where m = ρ_m × A × L, and I_avg is the average current under short-circuit conditions.

[0052] Using a similar average power method as described above, an iterative estimation is performed assuming a reference temperature rise (e.g., 150°C): P_25=U² / R_25; P_175=U² / R_225=U² / (R_25×(1+α×150)); The average power is: P_avg=(P_25+P_175) / 2=(U² / R_25+U² / (R_25×(1+α×150))) / 2=1 / 2×U² / R_25×(1+1 / (1+α×150)); Substituting R_25=ρ×L / A, we get: P_avg=1 / 2×U² / (ρ×L / A)×(1+1 / (1+α×150))=1 / 2×U²×A / (ρ×L)×(1+1 / (1+α×150)); ΔT=P_avg×t_s / (ρ_m×A×L×c)=(1 / 2×U²×A / (ρ×L)×(1+1 / (1+α×150))×t_s) / (ρ_m×A×L×c)=(1 / 2×U²×t_s×(1+1 / (1+α×150))) / (ρ×ρ_m×c×L²); Substituting the values ​​of each parameter, we get: ΔT=(1 / 2×220 2 ×0.01×(1+1 / (1+0.00429×150))) / (4.95× ×2.68×10³×897×4.74²)=145.6 (℃).

[0053] Calculations show that under short-circuit conditions, the current-limiting protection structure can raise the temperature by approximately 145.6℃ within 0.01s. At this point, the resistance of the current-limiting element rises to R_145.6 = R_25 × (1 + α × 145.6). To limit the current to I_target = 2000A, its resistance must satisfy R_145.6 = U / I_target. Combining R_25 = ρ × L / A, for a circular cross-section filamentary element (A = π × (d² / 4)), the diameter d can be derived as follows: R_145.6=(ρ×L / A)×(1+α×145.6)=U / I_target; d=√((4×ρ×L×(1+α×145.6)) / (π×(U / I_target))).

[0054] Substitute the numerical values ​​into the calculation: d=√((4×4.95× ×4.74×(1+0.00429×145.6)) / (π×(220 / 2000)))≈0.0021(m)=2.1(mm). Therefore, we need to select a 5052 aluminum alloy wire with a diameter of 2.1mm and a length of 4.74m as the current-limiting protection structure 2 to ensure that, under short-circuit conditions, the current-limiting protection structure 2 can limit the current to 2000A within 0.01s.

[0055] Finally, it was verified whether the steady-state power loss of the current-limiting element met the requirements under the rated operating current of 20A.

[0056] Calculate the resistance of the current-limiting element at room temperature: R_25 = ρ × L / A = 4.95 × ×4.74 / (π×(0.0021 / 2)²)≈0.06775(Ω); The rated operating heat output is: P_25 = I² × R_25 = 20² × 0.06775 ≈ 27.1 (W); As can be seen, the calculated steady-state power is 27.1 watts, which is far below the design target of 50 watts. This indicates that the temperature rise of the current-limiting element is controllable during normal operation and can be effectively dissipated through its own surface area and coiled structure.

[0057] Based on the above calculations, a 5052 aluminum alloy wire with a length of approximately 4.74 meters and a diameter of approximately 2.1 millimeters was selected as the current limiting protection structure 2, which can simultaneously meet all three design requirements: normal operation heat dissipation, rapid current limiting during short circuits, and backup fuse protection.

[0058] Example 2 In this embodiment, a circuit protection device integrating current limiting and backup fuse functions is also provided. The difference from Embodiment 1 is that, considering the convenience of modifying existing circuit breakers or the ease of replacing current limiting elements, the current limiting protection structure 2 adopts a modular external structure.

[0059] This modular external structure refers to the current-limiting protection structure 2 being encapsulated within a separate, proprietary insulating module housing. This housing is made of high-temperature resistant, high-strength engineering plastics (such as PBT or nylon). Inside the housing, metal wires are arranged on an insulating frame in a coiled or bent manner. Standard electrical interfaces, such as plug-in terminals or bolt-on posts, are provided at both ends of the housing.

[0060] The current-limiting protection structure 2 is connected in series between the incoming terminal and the power input terminal 3 of the circuit breaker body 1 through electrical interfaces at both ends of the housing. The current-limiting protection structure 2 and the circuit breaker body 1 are physically separate, but electrically they are a single unit.

[0061] This modular design allows for the replacement of only the entire module after the current-limiting protection structure 2 (current-limiting element) blows, without having to touch or scrap the circuit breaker body 1, making maintenance safer and faster.

[0062] The module housing can be sealed to prevent external contamination, or it can be designed to be detachable for easy replacement of the internal current-limiting wire.

[0063] Example 3 In this embodiment, a short-circuit protection method is also provided, which is implemented based on the hardware structure described in Embodiment 1 or 2 above.

[0064] Figure 2 The following is a flowchart of a short-circuit protection method according to an embodiment of this application, which will be combined with... Figure 2 The short-circuit protection method of this application is described in detail.

[0065] First, in step 201: connect the current limiting element in series.

[0066] This step includes connecting the current-limiting protection structure 2 (such as 5052 aluminum alloy wire) in series with the circuit breaker body 1 into the protected main circuit, forming an electrical path of power supply-current-limiting element-circuit breaker-load. This step is the foundation for building the entire protection system.

[0067] Step 202: Short circuit identification and current limiting. This is the first layer of protection in this embodiment.

[0068] This step includes: when a short-circuit fault occurs in the main circuit, a huge short-circuit current will instantaneously pass through the current-limiting protection structure 2. The current-limiting element of the current-limiting protection structure 2 utilizes its own resistive characteristics and thermal inertia to perform the core current-limiting action, including: Energy absorption and temperature rise: The short-circuit current generates huge Joule heat (P=I²R) on the current-limiting element in a very short time (e.g., within 1 millisecond), causing its temperature to rise sharply.

[0069] Resistance jump: Due to the strong positive temperature coefficient (PTC) effect of the material, its resistance value increases rapidly and nonlinearly with increasing temperature.

[0070] Achieving current limiting: According to Ohm's law (I=U / R, where I represents current, U represents voltage, and R represents resistance), the rapid increase in the total resistance of the loop causes the short-circuit current to be effectively limited below a preset safe peak value (e.g., limiting the current from a potential value of over 25kA to below 2000A within 10 milliseconds).

[0071] The core of this step is to limit the dynamic stability value of the short-circuit current to within the rated breaking capacity (Icu) of the circuit breaker body 1 before the mechanical tripping mechanism of the circuit breaker body 1 has fully activated (usually after 10-20 milliseconds).

[0072] In step 203: The circuit breaker trips normally.

[0073] The circuit breaker body 1 detects a limited overcurrent (e.g., 2000A), which is still within the magnetic or electronic tripping sensing range of the circuit breaker body, but is far below the extreme short-circuit current it cannot withstand. Subsequently, the circuit breaker body 1 reliably performs the disconnection operation, cutting off the circuit. In this scenario, the system only needs to be reset by the circuit breaker body 1 to return to normal; the current-limiting element of the current-limiting protection structure 2 can continue to be used because it has not reached its melting point.

[0074] Step 4.204: Backup fuse protection. This is the second layer of protection in this embodiment.

[0075] If, due to extreme circumstances (such as circuit breaker mechanism jamming, contact welding, etc.), the circuit breaker body 1 fails to execute the disconnection command, the circuit will remain connected. In this case: A large current continuously passes through the current-limiting element of the current-limiting protection structure 2, which is already in a high-temperature and high-resistance state, causing its temperature to rise further. Based on the material and size design, the current limiting element will reach its material melting point (e.g., 607°C) within a set backup protection time (e.g., 50 milliseconds), resulting in physical melting, arcing in the air, and eventually extinguishing, thus completely disconnecting the circuit.

[0076] This step provides a final, physical safety barrier to prevent catastrophic accidents caused by protection failure.

[0077] The circuit protection method provided in this embodiment constructs a deep, dual protection system through a timing logic of first limiting current, then disconnecting, and then using fuses as backup. This method enables circuit breakers with low breaking capacity to be reliably applied in scenarios with high breaking capacity requirements, while ensuring ultimate safety in the event of a single system failure (circuit breaker failure).

[0078] It will be understood by those skilled in the art that the above descriptions are merely preferred embodiments of this application and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A circuit protection device integrating current limiting and backup fuse functions, characterized in that, include: Circuit breaker body; A current-limiting protection structure is connected in series with the circuit breaker body; The current limiting protection structure includes a current-sensitive current limiting element made of a conductive material with a positive temperature coefficient. Under the action of short-circuit current, the resistance value of the current-sensitive current-limiting element increases nonlinearly within a preset time range to limit the current, thereby protecting the circuit breaker body. If the circuit breaker body fails to disconnect, the current-sensitive current-limiting element will physically melt due to overheating to cut off the circuit.

2. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, Also includes: The power input terminal and the load output terminal are connected in series to form the protection branch of the main circuit. The power input terminal is used to connect to the power distribution power supply, and the load output terminal is used to connect to the power system or equipment that needs protection, so that the current limiting protection structure and the circuit breaker body are connected in series in the protected circuit.

3. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, The conductive material is aluminum or an aluminum alloy.

4. The circuit protection device integrating current limiting and backup fuse functions according to claim 3, characterized in that, The aluminum alloy is 5052 aluminum alloy.

5. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, The current-sensitive current-limiting element is a metal wire with a length of 4.74m and a diameter of 2.1mm.

6. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, The current-sensitive current-limiting element has a heat generation power of less than 50W at the rated operating current.

7. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, The current-sensitive current-limiting element is configured to limit the current to below 2000A within 0.01 seconds after a short circuit occurs.

8. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, The current-sensitive current-limiting element is configured to melt within 0.05 seconds if the circuit breaker fails to trip.

9. The circuit protection device integrating current limiting and backup fuse functions according to claim 1, characterized in that, The current-sensitive current-limiting element is arranged in a coiled, bent, or spiral shape within the insulating housing of the circuit breaker body or in an insulating module independent of the circuit breaker body.

10. A short-circuit protection method, characterized in that, Includes the following steps: A current-sensitive current-limiting element is connected in series in the circuit of the circuit breaker; By utilizing the characteristic of the current-sensitive current-limiting element that rapidly heats up and increases resistance when a short circuit occurs, the short-circuit current is limited to a safe range that it can disconnect before the circuit breaker operates. If the circuit breaker fails to disconnect, a continuous set current is used to melt the current-sensitive current-limiting element, thus achieving the final disconnection of the circuit.

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