Photovoltaic cable fire suppression protectors, systems, materials and methods for MC4 connectors

Abstract

The invention relates to the technical field of photovoltaic cable or wire installation, basic electrical elements, connecting devices and adhesives, in particular to a photovoltaic cable fire extinguishing protector, system, material and method for an MC4 connector. The protector comprises a hollow shell, a perfluorohexanone microcapsule patch arranged towards a heating area, a composite seal, a limiting structure and a high-viscosity heat-conducting interface material, and a closed cavity is formed after the hollow shell, the perfluorohexanone microcapsule patch, the composite seal, the limiting structure and the high-viscosity heat-conducting interface material are assembled. The equivalent heat transfer gap is limited, the equivalent ventilation rate is checked through a concentration-time curve, the patch explosive load is determined according to calculation, second-level establishment is achieved, and the volume fraction not lower than the fire extinguishing threshold value is maintained within the set time. The device does not need external energy supply, has the functions of mechanical protection, rapid fire extinguishing and after-combustion inhibition, and is suitable for various outdoor photovoltaic scenes.

Description

Technical Field

[0001] This invention relates to the fields of installation, basic electrical components, connection devices and adhesives for photovoltaic cables or wires, and particularly to a photovoltaic cable fire extinguisher, system, material and method for MC4 connectors. Background Technology

[0002] With the rapid development of the global photovoltaic industry, the safety of photovoltaic systems has become an increasingly prominent issue. As a core connection component between photovoltaic modules and cables, and between cables and inverters, the MC4 connector's operational status directly affects the safety of the entire photovoltaic system. Industry statistics show that, as of 2023, approximately 42% of photovoltaic power plant fires in my country originated from MC4 connector failures. Therefore, providing highly reliable protection for MC4 connectors is a crucial step in reducing the fire risk of photovoltaic systems.

[0003] Chinese Patent No. CN221305873U (hereinafter referred to as Document 1) discloses a protective box for an MC4 connector, which can form a flame-retardant barrier around the connector, providing isolation and protection for the connector, thereby effectively preventing the spread of flames and improving system safety. However, Document 1 can only provide mechanical protection and basic insulation functions, lacking active fire extinguishing capabilities. Although the flame-retardant wire sleeve used has flame-retardant properties, it can only delay combustion and cannot quickly suppress the fire in the early stages. At the same time, conventional electrical fire extinguishing devices (such as dry powder or aerosol devices) are too large to be integrated into the compact structure of the MC4 connector.

[0004] On the other hand, the inventors in this case, through research and investigation, discovered that perfluorohexanone (C6F...) 12 O2, as a novel clean fire extinguishing agent, possesses advantages such as high extinguishing efficiency (extinguishing concentration 4%~6%), excellent insulation performance (breakdown voltage > 50kV), and environmental friendliness (ODP=0, GWP=1, atmospheric residence time < 0.01 years), making it highly suitable for use in the field of electrical fire extinguishing. However, it is liquid at room temperature (boiling point approximately 49℃), making it difficult to directly encapsulate in small-volume protective cavities; therefore, it has not yet been applied in miniature electrical connection devices.

[0005] In the prior art, Chinese invention application CN116889694A (hereinafter referred to as Document 2) proposes a fire extinguishing tablet solution using perfluorohexanone microcapsule technology. This solution distributes fire-fighting microcapsules evenly within a silicone substrate layer, utilizing the silicone layer to fix, support, and protect the microcapsules, preventing premature rupture during the high-temperature curing process, thereby improving the yield. The silicone substrate layer also isolates the microcapsules from air, moisture, ultraviolet radiation, and acid / alkali corrosion, extending their service life and maintaining the normal trigger sensitivity of the microcapsules when heated.

[0006] However, the inventors of this case have found that if the perfluorohexanone microcapsule fire extinguishing tablets in Document 2 are directly attached to the inside of the MC4 protective box shown in Document 1, although the fire extinguishing performance can be improved to a certain extent, there are still technical bottlenecks that are difficult to overcome.

[0007] On the one hand, the internal space of the MC4 connector is extremely limited, with a cavity volume of usually less than 30mL, and it is in a complex outdoor environment with high temperature difference, wind convection, salt spray and water vapor interference.

[0008] On the other hand, if fire extinguishing pads are simply attached, it is difficult to form a sufficient volume fraction of perfluorohexanone vapor (≥4%~6%) within seconds (≤3s) after a fire occurs, which makes it impossible to achieve rapid fire extinguishing and prevent reignition.

[0009] Therefore, how to achieve efficient encapsulation and rapid thermal response triggering of perfluorohexanone within a limited volume, and how to make the cavity vapor volume fraction reach and maintain the extinguishing threshold within seconds, has become a key issue that urgently needs to be addressed in current technology. Summary of the Invention

[0010] The purpose of this invention is to provide a photovoltaic cable fire extinguishing device, system, material and method for MC4 connectors to address the shortcomings of the prior art. It aims to achieve efficient encapsulation and rapid thermal response triggering of perfluorohexanone within a limited volume, and to make the cavity vapor volume fraction reach and maintain the fire extinguishing threshold within seconds.

[0011] This case involves a photovoltaic cable fire extinguisher for MC4 connectors, a high-security photovoltaic system, which, as part of a high-temperature and high-voltage electrical contact protection system, is closely related to thermally conductive protective materials for electronic packaging. It belongs to the core electronic industry, the manufacturing of tin materials for electronic packaging, and the extended application direction of zinc structural functional materials.

[0012] This invention achieves the above objective through the following technical solution: a fire extinguishing device for photovoltaic cables using MC4 connectors, comprising:

[0013] The housing is hollow inside and serves to accommodate the MC4 connector. Cable inlets are located at both ends. When assembled and closed, the housing forms an effective volume of [missing information]. A sealed cavity;

[0014] Perfluorohexanone microcapsule patches are disposed on the inner wall of the housing (i.e., the inner wall of the cavity) and arranged toward the predetermined heating area of ​​the MC4 connector;

[0015] A composite sealing structure is provided at the cable inlet and cooperates with the housing. The composite sealing structure and the housing together increase the equivalent air exchange rate of the sealed cavity. Within the target range, the volume fraction of perfluorohexanone vapor in the cavity is kept at or above the extinguishing threshold during the target maintenance time;

[0016] A limiting structure is provided on the inner wall of the housing; and

[0017] A thermally conductive interface material is disposed between the patch and the MC4 connector, and its thermal conductivity and thickness after assembly under pressure are configured to create an equivalent heat transfer gap. Limited to no more than the target thermal response time Equivalent thermal diffusivity of the interface The calculated maximum allowable value ( (to the maximum permissible heat transfer gap), thereby ensuring that the patch releases perfluorohexanone within the target thermal response time.

[0018] Furthermore, the MC4 connector is installed in the cavity, and the cavity's protection rating is not lower than IP67; the equivalent ventilation rate... The volume fraction-time decay curve of perfluorohexanone in the chamber was obtained through exponential fitting and used for maintenance condition verification; the volume fraction-time relationship satisfies the following equation:

[0019] ;

[0020] in, For a moment volume fraction, This is the initial volume fraction. This is the equivalent ventilation rate;

[0021] The composite sealing structure includes a sealing element. The housing mates with the sealing element at the cable inlet to form a meandering labyrinthine sealing flow channel. After assembly, the sealing element forms multiple contact surfaces with the cable sheath and the cable inlet to reduce the equivalent ventilation rate. .

[0022] Furthermore, the housing has a double-half-opening structure, and the limiting structure is integrally formed with the housing as limiting hooks and limiting slots distributed along the axial direction of the housing. The thermally conductive interface material is applied between the boss and the patch and / or the patch and the connector, and after assembly, the equivalent heat transfer gap is reduced. Limited to a range not exceeding 0.5 mm; the heat transfer gap satisfies the following formula:

[0023] ;

[0024] in, For the maximum permissible heat transfer gap, The equivalent thermal diffusivity of the interface. The target thermal response time;

[0025] The thermal conductivity of the thermal interface material is not less than 1.0 W / (m·K), and the operating temperature range covers −40℃ to 180℃;

[0026] The shell has an inner and outer layer structure. The inner layer is made of heat-resistant insulating material, and the outer layer has a weather-resistant coating with a thickness of not less than 20μm to improve its UV resistance and corrosion resistance.

[0027] The patch surface has a weather-resistant or self-healing coating to improve long-term outdoor stability.

[0028] In the heat conduction and triggering coupling design of this invention, the thermal conductivity of the heat-conducting interface material and its thickness after assembly and pressure constitute an equivalent heat transfer gap. The main controlling factor is the equivalent heat transfer gap, which is not simply a geometric distance, but rather refers to the equivalent heat transfer path thickness between the heat source and the perfluorohexanone microcapsule patch, taking into account factors such as the thickness of the thermally conductive layer, surface roughness, and micro-gaps. This parameter directly determines the speed at which heat is transferred from the heating surface to the patch trigger interface, thus affecting the response time of the microcapsule.

[0029] Under steady-state conditions, the transfer of heat through the thermally conductive interface layer can be approximated as a one-dimensional heat conduction process, and its equivalent thermal resistance can be determined by the thickness and thermal conductivity of the thermally conductive interface material. If the thickness of the thermally conductive interface material is too large or its thermal conductivity is insufficient, heat will be trapped within the interface layer, resulting in a slower temperature rise rate and preventing the microcapsules within the patch from triggering within the predetermined response time. If the thermally conductive layer is too thin, air gaps will form due to insufficient surface adhesion, leading to discontinuous local heat transfer paths. Therefore, to ensure the target thermal response time... For internally triggered extinguishing agent release, the thermal conductivity of the heat-conducting interface material and its compressive thickness must be designed in a coordinated manner to ensure an equivalent heat transfer gap. Satisfy thermal response constraints:

[0030] ;

[0031] in, This represents the equivalent thermal diffusivity of the interface region. The physical meaning of this constraint lies in the thermal conduction time constant. It is approximately proportional to the square of the heat transfer path length, that is:

[0032] ;

[0033] when When the temperature is too high, the time it takes for the temperature wave to reach the surface of the microcapsule will exceed [a certain value]. This caused a delay in the firefighting response; and when When the above inequality is satisfied, the microcapsule can be heated to the trigger temperature within the target time, ensuring that the device can rapidly release perfluorohexanone under short-term thermal events and achieve a second-level fire extinguishing response.

[0034] Further analysis shows that, The value depends on the thickness of the thermal interface material under pressure. With thermal conductivity The matching relationship. Its approximate relationship can be written as:

[0035] ;

[0036] in, Let be the equivalent thermal conductivity of the interface region. Therefore, when... When improving, This will reduce the heat transfer path, shorten the trigger time; conversely, when At lower levels, if not reduced accordingly This will lead to Exceeding the allowable upper limit results in microcapsule trigger hysteresis. Therefore, this invention controls the compressive thickness of the thermally conductive interface material by adjusting its formulation and filling amount. thermal conductivity This results in an equivalent heat transfer gap. satisfy This constraint ensures that heat is transferred to the extinguishing agent triggering interface within the target response time, achieving a safe, stable, and rapid extinguishing response process.

[0037] This design approach transforms the parameter configuration of the thermal interface material from a simple material selection issue into a coupled thermal system comprised of factors such as thermal diffusivity, geometric assembly clearance, and interfacial contact pressure. Through theoretical calculations and experimental verification, the inventors determined the equivalent heat transfer gap under different combinations of thermal conductivity and thickness. Changes in response time The effect exhibits a quadratic relationship. When the thickness of the thermally conductive layer is halved or the thermal conductivity is doubled, The corresponding reduction of approximately 40%–50% can shorten the trigger time by approximately 60%–70%. This optimized matching strategy effectively transforms thermal design constraints into parameter control of materials and structures, achieving predictability and verifiability in systematic design.

[0038] Furthermore, equivalent ventilation rate The fit was performed using the least squares method with an exponential decay model, and the goodness of fit satisfied. Or within the 95% confidence interval The relative uncertainty does not exceed 10%;

[0039] Equivalent heat transfer gap Acceptance is determined by assembly fixtures, which are combinations of go / no-go gauges or feeler gauges and limit blocks. The equivalent heat transfer gap is measured in the corresponding area of ​​the patch after assembly. satisfy And the measurement repeatability is not worse than ±0.05 mm, of which This is the maximum permissible heat transfer gap;

[0040] limited The dimensional chain consists of the limit hook height tolerance, the connector outer diameter tolerance, and the thickness tolerance of the thermal interface material after coating. The combined deviation of these three in the assembled state satisfies... Consistency requirements For equivalent heat transfer gap, This is the maximum permissible heat transfer gap. Specifically, the sensor is mainly used in development and type testing, as well as production line sampling / calibration stages, to measure data (and fit the data). The sensor was then removed and a sealing plug was used to restore a full seal. The weather-resistant or self-healing coating on the patch surface has an adhesion grade of no less than 1 (according to GB / T9286 or equivalent standard) after accelerated UV aging test (QUV, 340nm, ≥1000h), a mass loss rate of no more than 5%, and no cracking, blistering or peeling after salt spray (≥480h) and thermal cycling (−40℃-85℃, ≥200 times).

[0041] A quantitative design method for a perfluorohexanone microcapsule fire extinguisher for preparing MC4 connectors includes the following steps:

[0042] Preset steps: Determine the cavity volume And set the target volume fraction Duration ;

[0043] Preliminary step: Calculate the instantaneous target volume fraction based on the ideal gas law. Required instantaneous minimum vaporization mass ;

[0044] Initial steps: After the housing is assembled and closed, tracer gas is injected into the cavity to the initial volume fraction through the reusable calibration channel or dedicated calibration port in the cable inlet labyrinth section. Record the volume fraction-time data series and fit the data to obtain the equivalent ventilation rate. And calculate the maintenance supply quality. ;

[0045] Metering steps: Determine the minimum vaporization mass With maintaining supply quality Summation and introduction of engineering margin factor To obtain the total load ;

[0046] Conversion steps: Combine with the effective area of ​​the patch Density of the mixture With effective core material mass fraction Converting the thickness of the adhesive layer ;

[0047] Calculation steps: Based on the unsteady-state thermal diffusion approximation, from the target response time... Equivalent thermal diffusivity of the interface By reverse calculation, the equivalent heat transfer gap is obtained. Maximum permissible heat transfer gap Based on this, the limiting structure and the thickness of the thermal interface material were designed.

[0048] Furthermore, in the preliminary step, the instantaneous minimum vaporization mass is calculated according to equation (1):

[0049] Equation (1): ;

[0050] in, The instantaneous minimum vaporization mass, This is the cavity pressure (usually taken as standard atmospheric pressure). This represents the effective volume of the cavity after assembly. For the target volume fraction, The constant is 8.314 J·mol⁻¹·K⁻¹. Temperature at release (K) This represents the molar mass of perfluorohexanone.

[0051] Furthermore, in the initial steps, maintaining the quality of the supply is crucial. Approximate the result using equation (2):

[0052] Equation (2): ;

[0053] in, To maintain the quality of supplies, For the minimum instantaneous vaporization mass, It is the equivalent ventilation rate (the reciprocal of time). The set duration.

[0054] Furthermore, in the metering step, the total load... According to formula (3), we get:

[0055] Equation (3): ;

[0056] in, For total load capacity, This is the engineering margin coefficient (dimensionless). For the minimum instantaneous vaporization mass, To maintain the quality of supplies.

[0057] Furthermore, in the thickness calculation step, the thickness of the laminate is converted according to formula (4):

[0058] Equation (4): ;

[0059] in, For the thickness of the adhesive layer, The mass of pure perfluorohexanone in a single patch, This represents the effective coating area of ​​the patch. For the density of the lamination mixture, The effective core material mass fraction in the mixture;

[0060] The process window for the lamination thickness is set to ,occupy 2%-10%, of which The target thickness refers to the theoretical thickness that the laminate is expected to achieve during design and production. This refers to the allowable thickness deviation range, used to compensate for thickness changes caused by curing shrinkage and surface finishing.

[0061] Furthermore, the maximum allowable heat transfer gap is calculated from equation (5) and used for structural design:

[0062] Equation (5): ;

[0063] in, For the maximum permissible heat transfer gap, The equivalent thermal diffusivity of the interface. The target thermal response time;

[0064] The sensor used to determine the volume fraction of perfluorohexanone in the cavity has a range of not less than 10% VOL, an indication error of not more than ±0.1% VOL, and a sampling interval of not more than 1 s; the volume fraction-time relationship is obtained by fitting equation (6). :

[0065] Equation (6): ;

[0066] in, For a moment volume fraction, This is the initial volume fraction. It is the equivalent ventilation rate.

[0067] A highly adhesive thermally conductive interface material for use in the aforementioned high-security photovoltaic system, comprising an organosilicone adhesive composition, is used to form a thermally conductive adhesive layer between the perfluorohexanone microcapsule patch and the MC4 connector and to achieve thermal coupling and fixed connection. The composition comprises the following components in parts by weight:

[0068] The product comprises: 60-120 parts of silicone resin base (containing vinyl-terminated polydimethylsiloxane and / or phenyl-modified polysiloxane); 0.5-5 parts of interface coupling modifier; a curing system (containing a crosslinking agent and catalyst, and configured to cure within 24 hours at a temperature not exceeding 60°C, with the peak self-heating temperature relative to the environment not exceeding +20°C); 5-40 parts of thermally conductive filler, selected from one or more of boron nitride, aluminum nitride, flake graphite, graphene, alumina, or copper powder, and surface-treated with a silane coupling agent; 2-20 parts of flame retardant additive; and 0.2-3 parts of rheology modifier and defoaming system.

[0069] The material has a Brinell viscosity of 5×10³ to 1×10³ at 25°C. 5 The pressure is mPa·s, suitable for forming an interface layer of 50–300 μm under pressure, and after curing, it simultaneously meets the following indicators: thermal conductivity not less than 1.0 W·m⁻¹·K⁻¹; equivalent interfacial thermal resistance not more than 0.25 K·cm²·W⁻¹; 180° peel strength to the inner wall of the polyetheretherketone shell and the backing substrate of the patch not less than 1.0 N·mm⁻¹; volume resistivity not less than 1.0 × 10¹² Ω·cm; dielectric strength not less than 15 kV·mm⁻¹; volatile organic compound content not more than 0.5%; total extractable halide ion content not more than 10 ppm; operating temperature range −40℃ to 180℃, after thermal cycling; adhesion and thermal conductivity retention rate not less than 80% after salt spray and UV aging. This part of the technology is essentially a strong-adhesion interface functional material (a high thermal conductivity self-adhesive layer based on organosilicon), involving self-adhesive rubber asphalt rolls, which belong to the self-adhesive rubber asphalt material system in advanced inorganic non-metallic materials; as well as synthetic polymer sealing materials and high-efficiency sealants involving advanced petrochemical new materials.

[0070] MC4 connectors are typically used in confined spaces, outdoor temperature cycling, and environments with vibration and salt spray / moisture. This dictates that the interface between the patch and the connector must not only ensure efficient heat conduction but also maintain positional stability under long-term environmental stress, preventing pumping out or surface creep. If the interface loosens or its thickness shifts, the equivalent heat transfer gap increases, slowing down the microcapsule trigger response. Simultaneously, "bypass gaps" form at the patch edges, allowing extinguishing vapors on the cavity side to escape more easily, significantly increasing the difficulty of maintaining the volume fraction. While general-purpose thermal greases offer low thermal resistance, they lack structural adhesion; ordinary double-sided adhesives provide initial and holding power but often suffer from insufficient thermal conductivity, poor insulation, and inadequate volatile content control. To address this conflicting constraint, this project employs a specialized interface material with high adhesion and low interfacial thermal resistance, primarily based on silicone. Through formulation and process coupling, it simultaneously solves four objectives: thermal conductivity, insulation, long-term adhesion, and environmental adaptability.

[0071] The resin matrix of the material is made of vinyl-terminated polydimethylsiloxane, synergistically combined with a certain proportion of phenyl-modified siloxane. The former provides a low glass transition temperature and excellent resilience, while the latter enhances resilience under UV and low-temperature shock, and strengthens the wetting and physical bonding of the polyetheretherketone shell and the polyimide patch backing, providing a substrate for high peel strength. The thermally conductive network uses fillers such as boron nitride, aluminum nitride, and alumina, which prioritize electrical insulation, in a particle size distribution, supplemented with a small amount of lamellar carbon material used only when dielectric boundaries are met. The filler surface is pretreated with a silane coupling agent, allowing the inorganic filler to form stable, dense, and non-agglomerated thermal channels in the siloxane network. This allows for good rheological and workability even at high solids content, with a bulk thermal conductivity consistently reaching or exceeding 1.0 W·m⁻¹·K⁻¹, without sacrificing volume resistivity and dielectric strength. To achieve direct adhesion to common engineering plastics (such as PA and PPO) for polyetheretherketone, polyimide, and MC4 shells, the coupling modifier adopts a synergistic system of epoxy or amino-functionalized silanes. By controlling the dosage within a low percentage range, the chemical bridging and energy matching of the polar substrate interface can be significantly improved, which can both suppress shear displacement under thermal cycling and reduce the risk of pump-out caused by long-term vibration.

[0072] The choice of curing system directly affects the safety and cleanliness of the microcapsules. This study employs a low-exothermic addition crosslinking system, which can cure within 24 hours under mild conditions not exceeding 60°C. The self-heating peak during curing does not exceed +20°C relative to the environment, avoiding the exothermic shocks and low-molecular-weight byproduct precipitation common in condensation systems. This reduces thermo-mechanical disturbances to the microcapsule wall material and volatile contamination of the shell cavity from the source. For electrochemical and insulation reliability considerations, the formulation sets strict upper limits on the total amount of volatile organic compounds and extractable halide ions, ensuring that the material will not become a potential source of corrosion or insulation degradation in photovoltaic scenarios with long-term moisture and micro-electric fields. To balance dispensing and thickness control during press-fitting, the material exhibits a medium-to-high viscosity rheological window at room temperature, with the Brinell viscosity controlled within the process-operable range. This allows for rapid spreading and filling of microscopic voids under assembly pressure, forming a stable interface layer of 50–300 μm after compaction. This thickness range matches the maximum permissible heat transfer gap design on the device side, eliminating the primary cause of contact thermal resistance without introducing unnecessary thermal path lengthening. To quantify interface performance, the equivalent interface thermal resistance, tested using standard methods, is no higher than 0.25 K·cm²·W⁻¹, the 180° peel strength reaches and preferably exceeds 1.0 N·mm⁻¹, and the volume resistivity is no less than 10 N / mm². 13 Ω·cm, dielectric strength not less than 20kV·mm⁻¹; after thermal shock, salt spray and ultraviolet aging, the performance retention rate is higher than 80%, to prove that the adhesion and thermal conductivity do not significantly degrade throughout the entire life cycle.

[0073] In the preparation process, firstly, in the filler coupling pretreatment step, boron nitride, aluminum nitride, and alumina are reacted with silane coupling agents to complete surface organication and moisture removal. Subsequently, in the base material and additive premixing step, vinyl siloxane, phenyl-modified siloxane, interface coupling modifier, and flame retardant additive are uniformly mixed in proportion to ensure sufficient wetting and compatibility of the system before the introduction of high-filler. In the batch addition and mixing step, the coupled thermally conductive filler is added in three to four batches to a visceral mixer / planetary vacuum stirrer, controlling temperature rise and shear until uniform dispersion without significant agglomeration. Then, a vacuum degassing step is performed. The pressure is reduced to eliminate microbubbles and lower potential sources of interfacial thermal resistance. Hydrosilicone crosslinking agents and catalysts are added during the curing system introduction and viscosity tuning steps, and the rheology is finely adjusted with diluents or thixotropic modifiers to ensure stable and controllable dispensing or scraping processes. The film formation / dispensing and curing steps are completed in a clean environment, and the coating or dispensing is completed after pressing and cured at room temperature or 40–60°C. The thickness is confirmed to be within the design window by feeler gauge or non-contact measurement. Finally, the performance testing and release steps are conducted item by item according to thermal conductivity, adhesion, dielectric, volatile / ionic residue and environmental durability to ensure that the interface parameters of each batch of materials and assembly are under closed-loop control.

[0074] The aforementioned materials and processes are not optimized in isolation, but rather directly synergistically integrated with the overall heat transfer and airtightness objectives. Utilizing high adhesion and low interfacial thermal resistance, the thermal path between the patch and connector is effectively transferred within seconds, meeting the design requirements for the target thermal response time. The material's volume stability and adhesive durability during curing and service ensure that the equivalent heat transfer gap does not "grow" over its lifespan, thus maintaining trigger consistency. The interface layer forms a continuous sealing transition around the patch, suppressing microcracks on the cavity side and helping to reduce the equivalent air exchange rate, making it easier to achieve the calculated conditions for maintaining the volume fraction. Unlike existing technologies that directly apply thermally conductive fillers to the patch substrate, the materials described here are specifically designed for the "patch-connector" coupling interface. A complete set of boundary conditions is provided around the microcapsule's temperature-sensitive characteristics and photovoltaic insulation boundaries, including low-heat curing, ion and volatile limits, dielectric safety, and long-term retention rate, addressing interface engineering challenges in different problem domains. Based on this, the cavity volume, sealing structure and limiting gap design of the device are transformed from the aforementioned calculation model. The physical properties and process window of the interface material, in turn, ensure that these calculation targets can be repeatedly achieved during manufacturing and life cycle, thereby forming a closed loop of "formula-process-structure-indicators" to ensure the comprehensive technical effect of rapidly establishing the target volume fraction in a limited space and stably suppressing reignition within a set time.

[0075] A method for preparing the aforementioned strongly adhesive thermally conductive interface material includes the following steps:

[0076] The surface coupling modification steps of the filler are as follows: The thermally conductive filler is treated with 0.5-2.0% by mass of silane coupling agent in anhydrous organic solvent at 50-80℃ for 0.5-2h, dried and then sieved through a 200-400 mesh sieve to obtain the surface-modified thermally conductive filler.

[0077] Premixing steps for base material and additives: At a temperature not exceeding 40°C, put the silicone resin base material, flame retardant additives, rheology modifiers and defoaming system into a planetary mixer or three-roll mill and premix for 10 to 30 minutes.

[0078] In the batch addition and mixing steps: Under the condition of 300-1000 rpm, the surface-modified thermally conductive filler is slowly added into the premixed system in 2-4 batches and mixed for 15-45 minutes, while controlling the material temperature rise to not exceed 10℃ during the process.

[0079] Vacuum degassing step: Place the mixture under a vacuum of -0.08 to -0.095 MPa for 5 to 20 minutes to degas and eliminate entrained gas;

[0080] Curing system introduction steps: Add crosslinking agent and catalyst and disperse evenly so that the resulting composition can be cured within 24 hours at a temperature not higher than 60°C and the peak value of self-heating during curing is not higher than the ambient temperature +20°C;

[0081] Viscosity tuning steps: By fine-tuning the base material and filler or by appropriate thickening / dilution, the Brinell viscosity at 25℃ is adjusted to reach 5×10³~1×10³. 5 mPa·s;

[0082] Film formation / dispensing and curing steps: Apply an interface layer with a thickness of 50-300 μm after pressure to the surface to be bonded by scraping or dispensing, and choose to cure at room temperature for 24 h or at 40-60℃ for 2-6 h;

[0083] Performance testing and release procedures: The thermal conductivity, equivalent interfacial thermal resistance and 180° peel strength of the cured sample are tested. After meeting the aforementioned indicators after curing, it is put into use as a thermally conductive adhesive material between the perfluorohexanone microcapsule patch and the MC4 connector.

[0084] The beneficial effects of this invention are:

[0085] This invention achieves highly efficient fire extinguishing and reignition prevention control within a confined space by systematically integrating the MC4 connector protective structure with perfluorohexanone microcapsule fire extinguishing technology. Its core concept lies in the coupled design of the cavity structure, heat conduction path, airtightness, and extinguishing agent release dynamics, enabling the formation and maintenance of a stable extinguishing atmosphere within seconds. This overcomes the technical bottleneck of existing technologies that cannot quickly establish an effective extinguishing concentration under limited volume and environmental disturbances.

[0086] The device features a double-half-opening housing structure, which is locked in place by a limiting structure to position the MC4 connector. This ensures a defined geometric relationship between the connector and the patch, guaranteeing the stability of the heat conduction path and heat transfer efficiency. The inner wall of the housing is equipped with perfluorohexanone microcapsule patches, which form a tight fit with the MC4 connector through a thermally conductive interface material. This interface material is either thermally conductive silicone grease or thermally conductive gel (with a thermal conductivity of...). It has a high thermal conductivity and a wide operating temperature range, enabling heat to be transferred to the patch in a very short time, thereby achieving the target thermal response time. The internally triggered microcapsule ruptures and releases perfluorohexanone. This design allows localized overheating to be directly converted into extinguishing agent release behavior, achieving a zero-delay coupling from "heat point" to "extinguishing response".

[0087] By incorporating a composite sealing structure at the cable inlet of the housing, a meandering labyrinthine sealed flow channel is formed, supplemented by a compressible elastic seal. This limits the equivalent air exchange rate λ between the cavity and the outside air to an extremely low level, reducing gas convection losses. After assembly, the seal forms multiple contact surfaces with the cable sheath and the housing port. This multi-layered interface structure effectively suppresses gas leakage caused by external disturbances, ensuring that the perfluorohexanone vapor volume fraction within the cavity can be stably maintained within the target range of 4%–6% during fire extinguishing, thereby preventing reignition caused by concentration decay.

[0088] In addition, the device utilizes the equivalent thermal diffusivity at the interface. With target response time The matching design was used to calculate the maximum allowable heat transfer gap. Therefore, in the structural design and manufacturing tolerance chain control, Limited to no more than The design ensures the determinism of the interfacial heat transfer response through the inverse calculation of the heat diffusion equation, enabling a sufficient number of microcapsules to rupture within a specified time at each heat conduction path, forming a continuous extinguishing gas release layer and achieving uniform spatial distribution of the extinguishing agent.

[0089] The decay relationship of cavity volume fraction over time during the maintenance phase after microcapsule release. It is used as a quantitative verification standard. By performing exponential fitting on the attenuation curve and maintaining R²≥0.95, the repeatability of fire extinguishing performance and the reliability of parametric design can be guaranteed. The inventors further introduced a quantitative calculation model for the fire extinguishing agent based on the ideal gas law, using the instantaneous minimum vaporization mass... With maintaining supply quality Step-by-step calculation, combined with engineering allowance coefficient The microcapsule loading is optimized to ensure that the release amount meets the needs of instantaneous fire extinguishing while avoiding sudden pressure increases in the cavity or material waste caused by excessive release, thus achieving a balance between the utilization rate of the extinguishing agent and safety.

[0090] Overall, this device achieves efficient fire extinguishing and concentration maintenance within an extremely small volume through optimized cavity structure, quantitative constraints on heat conduction paths, and mathematical design of extinguishing agent release kinetics. Compared with existing technologies, this invention can not only rapidly trigger fire extinguishing within seconds of abnormal temperature rise in the MC4 connector, but also maintain a stable extinguishing concentration in complex outdoor environments, significantly reducing the risk of reignition. It fundamentally overcomes the shortcomings of the first paper, which only provides mechanical protection, and the second paper, which cannot stably maintain the extinguishing concentration. This gives the MC4 connector self-response and self-inhibition active protection capabilities, thereby enabling the photovoltaic system to operate reliably for a long time under high safety levels. Attached Figure Description

[0091] Figure 1 This is a schematic diagram of the photovoltaic cable fire extinguishing device of the present invention in its assembled closed state.

[0092] Figure 2 for Figure 1 A structural decomposition diagram.

[0093] Figure 3 for Figure 2 A schematic diagram of the further decomposition of the structure based on the above.

[0094] The reference numerals in the figures include:

[0095] 1-Shell,

[0096] 11-Cable inlet, 12-Cavity, 13-Pattern, 14-Composite sealing structure, 15-Limiting structure.

[0097] 111-Maze-sealed flow channel,

[0098] 151-Limit hook, 152-Limit opening. Detailed Implementation

[0099] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It is understood that the accompanying drawings are provided for reference and illustration only, and are not intended to limit the present invention. The connection relationships shown in the accompanying drawings are only for clear description and do not limit the connection method. The step names are only for convenience of description and do not constitute a limitation on the order of methods.

[0100] like Figures 1-3 As shown, embodiments of this application provide a photovoltaic cable fire extinguishing device and method for MC4 connectors. This solution adds an active fire extinguishing function to the traditional passive protection structure. Through the synergistic effect of optimized heat conduction path, enhanced sealing performance, and quantitative design of microcapsule release, it achieves rapid triggering, concentration establishment, and controllable control of the entire process of preventing reignition within a small volume space.

[0101] A fire extinguishing device for photovoltaic cables using MC4 connectors, comprising:

[0102] Housing 1, hollow inside to accommodate MC4 connector, with cable inlets 11 at both ends, the housing 1, when assembled and closed, forms an effective volume of A sealed cavity 12;

[0103] The perfluorohexanone microcapsule patch 13 is disposed on the inner wall of the housing 1 (i.e. the inner wall of the cavity 12) and arranged towards the predetermined heating area of ​​the MC4 connector;

[0104] A composite sealing structure 14 is disposed at the cable inlet 11 and cooperates with the housing 1. The composite sealing structure 14 and the housing 1 together reduce the equivalent air exchange rate of the sealed cavity 12. Within the target range, the volume fraction of perfluorohexanone vapor in cavity 12 is kept at or above the extinguishing threshold during the target maintenance time.

[0105] The limiting structure 15 is disposed on the inner wall of the housing 1, and is used to lock the housing 1 when it is closed, thereby positioning and locking the MC4 connector; and

[0106] A thermally conductive interface material is disposed between the limiting structure 15 and the patch 13 and / or between the patch 13 and the MC4 connector, for use in reducing the equivalent heat transfer gap. Limited to no more than the target thermal response time Equivalent thermal diffusivity of the interface The calculated maximum allowable value ( (to the maximum permissible heat transfer gap), thereby ensuring that the patch 13 is triggered to release perfluorohexanone within the target thermal response time.

[0107] Furthermore, the MC4 connector is installed in the cavity 12, and the protection rating of the cavity 12 is not lower than IP67; the equivalent ventilation rate... The perfluorohexanone volume fraction-time decay curve within cavity 12 was obtained through exponential fitting and used for maintenance condition verification. The housing 1 has a double-half-opening structure. The limiting structure 15 is integrally formed with the housing 1 as limiting hooks 151 and limiting slots 152 distributed along the axial direction of the housing 1. A thermally conductive interface material is applied between the boss and the patch 13 and / or between the patch 13 and the connector, and after assembly, the equivalent heat transfer gap is reduced. It is limited to a range of no more than 0.5 mm.

[0108] A quantitative design method for a perfluorohexanone microcapsule fire extinguisher for preparing MC4 connectors includes the following steps:

[0109] Preset steps: Determine the volume of cavity 12 And set the target volume fraction Duration ;

[0110] Preliminary step: Calculate the instantaneous target volume fraction based on the ideal gas law. Required instantaneous minimum vaporization mass ;

[0111] Initial steps: The concentration-time decay experiment was used to obtain the desired results. And calculate the mass of the maintenance supply. ;

[0112] Metering steps: Determine the minimum vaporization mass With maintaining supply quality Summation and introduction of engineering margin factor To obtain the total load ;

[0113] Conversion steps: Combine the effective area of ​​patch 13 Density of the mixture With effective core material mass fraction Converting the thickness of the adhesive layer ;

[0114] Calculation steps: Based on the unsteady-state thermal diffusion approximation, from the target response time... Equivalent thermal diffusivity of the interface By reverse calculation, the equivalent heat transfer gap is obtained. Maximum permissible heat transfer gap Based on this, the limiting structure 15 and the thickness of the thermal interface material were designed.

[0115] The device proposed in this invention differs significantly from existing technologies in both its overall structure and physical mechanism, and is particularly innovative compared to the direct combination of References 1 and 2. Through a defined combination of technical features, this device achieves a complete fire extinguishing logic within a very small space, including rapid response, concentration formation and maintenance, and prevention of reignition.

[0116] First, this invention establishes a stable and minimal heat transfer path between the patch 13 and the connector heating area by setting a limiting structure 15 on the inner wall of the housing 1 and a thermally conductive interface material on the inner wall of the cavity 12. According to the theory of heat diffusion, the heat transfer time... With gap thickness They are related by a square, that is: ;

[0117] in, The characteristic time for heat transfer is denoted as s. The distance (m) between patch 13 and the heating surface. The equivalent thermal diffusivity (m² / s). When When the diameter is reduced from 3mm to 0.5mm, will shorten by approximately This represents a significant increase, meaning the fire suppression response time is improved by an order of magnitude. This is achieved by selecting thermally conductive silicone grease or thermally conductive gel (with a thermal conductivity of...). As a thermally conductive interface material, it can further improve the interface thermal conductivity, shorten the triggering time to less than 2 seconds, and thus complete the release of the extinguishing agent in the "preheating stage" before the flame is generated.

[0118] Secondly, the sealing assembly of the present invention adopts a composite sealing design that combines a labyrinth seal structure with a sealing element, which significantly reduces the equivalent air exchange rate of the cavity 12. According to the concentration decay model: ;

[0119] in, For a moment gas concentration, This is the initial concentration. This is the equivalent ventilation rate. If The concentration can remain unchanged after 5 minutes. The concentration remained above the extinguishing threshold. This result demonstrates that the present invention can maintain the extinguishing concentration for an extended period without external power supply, effectively preventing reignition.

[0120] Furthermore, the perfluorohexanone microcapsule patch 13 of this invention achieves a precise match between the extinguishing agent loading and extinguishing performance through a standardized design. Minimum instantaneous vaporization mass The calculation formula is: ;

[0121] in, The pressure in the cavity is 12 Pa. The effective volume (m³) of cavity 12. The target volume fraction (usually taken as 0.05–0.06). , Release temperature (K) This represents the molar mass of perfluorohexanone.

[0122] Based on this, the maintenance supply quality after leakage compensation is taken into account. :

[0123] ;in, To maintain the quality of supplies, For the minimum instantaneous vaporization mass, It is the equivalent ventilation rate (the reciprocal of time). The set duration;

[0124] Combining the two, we obtain the total load capacity: ;in, For total load capacity, This is the engineering margin coefficient (dimensionless). For the minimum instantaneous vaporization mass, To maintain the quality of supplies.

[0125] This series of calculations allows production engineers to quantitatively determine coating thickness and charge amount based on the housing volume, sealing rating, and fire extinguishing objective, without the need for trial and error.

[0126] In addition, the coating thickness of patch 13 Compared with the drug content of a single tablet The relationship between them is determined by the following formula: ;in, The coating thickness is in meters (m). The area of ​​patch 13 is (m²). The density (kg / m³) is the mixture of microcapsules and silicone rubber. This represents the mass fraction of pure perfluorohexanone in the mixture;

[0127] This formula allows for the direct conversion of theoretical loading capacity into process control parameters, enabling batch, reproducible production.

[0128] Through the aforementioned quantitative design method, this invention not only achieves active fire suppression in terms of functionality, but also establishes a complete link in engineering design methodology, encompassing performance objectives, structural parameters, and process control. Consequently, fire suppression performance no longer relies on experience but can be accurately predicted through measurable parameters, greatly improving reliability and consistency.

[0129] This device mainly includes: a hollow shell 1, a composite sealing assembly, a thermally conductive interface material, and a perfluorohexanone microcapsule patch 13. The shell 1 has a double-layer structure; the inner layer uses a high-temperature resistant insulating material such as PEEK (polyetheretherketone), and the outer layer is an UV-resistant and weather-resistant layer coated with a 35μm thick PVF (polyvinyl fluoride) coating. This structure ensures both mechanical strength and insulation performance while resisting outdoor UV and damp heat aging. Cable inlets 11 are located at both ends of the shell 1, employing a labyrinth seal channel 111 and a composite sealing structure 14 that mates with a compressible elastic seal to achieve an IP67 level seal. The shell 1 is equipped with an integrated limiting hook 151 and a limiting slot 152 to control the geometric gap between the MC4 connector and the patch 13.

[0130] To achieve rapid thermal response, the inventors used thermally conductive silicone grease as the interface filler material, with a thermal conductivity of not less than 1.0 W / (m·K), which was uniformly applied between the limiting hook 151 and the patch 13 during the assembly of the cavity 12. According to the formula... If the equivalent heat transfer gap And the equivalent thermal diffusivity of the thermally conductive material Then the response time It can be triggered immediately when the connector temperature reaches 110°C.

[0131] (I) Microcapsule preparation process

[0132] Perfluorohexanone microcapsules were prepared using interfacial polymerization, the basic principle of which is that a polymerization reaction occurs at the interface of an oil-water two-phase system to form a coating film. The specific steps are as follows:

[0133] Oil phase preparation steps: Perfluorohexanone and Span-80 is mixed to form an oil phase.

[0134] Aqueous phase preparation steps: Add to deionized water Polyurea prepolymer and SDS.

[0135] Emulsification step: The oil phase is dropped into the aqueous phase at a certain speed, and stirred for 10 minutes to form particles of a certain size. – The emulsion.

[0136] Polymerization and curing step: Heat to Maintain for 2 hours, and the interface will aggregate to form a coating layer.

[0137] Washing and drying steps: centrifugation, washing three times, then... Freeze-dry for 24 hours to obtain dried microcapsule powder.

[0138] According to TGA testing, the initial temperature of weight loss for the microcapsules is... The temperature at which it is fully released is approximately It is suitable for MC4 connectors under overheat triggering conditions.

[0139] (II) Fabrication process of patch 13

[0140] Patch 13 uses silicone rubber as a matrix. The prepared microcapsule powder is mixed with methyl vinyl silicone rubber at a mass ratio of 6:4, and then added... Dicumyl peroxide is used as a crosslinking agent. After mixing for 10 minutes using a two-roll mill to form a uniform paste, it is applied to a PI film at a doctor blade height. Apply evenly.

[0141] The coated film at Bake for 30 minutes to cross-link and form, then spray with a layer of coating. A self-healing polyurethane coating is used to improve weather resistance.

[0142] According to formula (4): ;

[0143] Set a single-piece patch 13 Mixture density , Target drug quality ,have to:

[0144]

[0145] Therefore, the actual coating thickness is controlled within... – Within the specified range. The drug content and trigger temperature for each batch are confirmed by weighing and TGA testing.

[0146] (III) Sealing performance and parameter calibration

[0147] After sealing the prototype, inject... The tracer gas concentration was recorded over time using a gas sensor. Equation (6) was used to fit the experimental data to the model: goodness of fit The result To prepare for subsequent design .

[0148] During the design phase, the required total amount of extinguishing agent is determined through the following calculations:

[0149] set up , , , .but: ;

[0150] Maintaining supply quality: ;

[0151] Engineering allowance coefficient is taken as , ;

[0152] Because it uses a double-patch 13 structure, each tablet contains medication. .

[0153] Actual testing verified that the fire extinguishing response time under this design is approximately 1.8 seconds, the extinguishing concentration is maintained for 5 minutes, and no reignition was observed.

[0154] (iv) Structural assembly process

[0155] The assembly process strictly follows the principles of modularization and pollution prevention, and the specific steps are as follows:

[0156] Pre-treatment steps: First, clean the MC4 connector body, the inner wall of housing 1, and the surface of the limiting hook 151 with isopropyl alcohol (IPA), and then... Dry for 10 minutes to remove surface oil and moisture. Immediately after cleaning, apply a layer of approximately [thickness missing]. Use thermal grease to prevent air bubbles from forming.

[0157] Installation steps for patch 13: Using a dedicated positioning fixture, attach the perfluorohexanone microcapsule patch 13 to the limiting hook 151 and / or the inner wall of the cavity 12, controlling the gap. If the gap is too large, it will affect the heat conduction rate; if it is too small, patch 13 will be prone to breakage under pressure. Therefore, an elastic silicone gasket is used to automatically compensate for manufacturing tolerances, ensuring that the assembly tolerance meets ±0.05mm.

[0158] Cable embedding procedure: Insert the photovoltaic cable into the labyrinth-sealed inlets at both ends of housing 1. The seals are made of fluororubber with a hardness of Shore A70 and a radial pre-compression ratio of 15%. This pre-compression ratio was determined through finite element simulation and can maintain constant contact stress under temperature cycling (–40℃~85℃), ensuring stable sealing performance.

[0159] Housing 1 Closing and Locking Procedure: A snap-fit ​​structure with metal pressure plates is used for fixation, ensuring the structure can be repeatedly disassembled and reassembled. The snap-fit ​​is injection molded from 30% PBT+GF material and has undergone 500 opening and closing tests without cracking. The pressure plate is stamped from SUS304 stainless steel and can provide a clamping force of over 200N.

[0160] Pressure relief vent configuration steps: To prevent the extinguishing gas from being released too quickly and causing the housing 1 to rupture, a micro-orifice valve is provided on the top of the housing 1, with an orifice diameter of... The valve plate is made of a PTFE film and a silicone pad layer, and has a one-way pressure relief function. This pressure relief port allows the internal air pressure to rise to [a certain value]. It will automatically open after the fire is extinguished and close naturally afterward to prevent external moisture from entering.

[0161] After assembly, each sample underwent an airtightness test using the helium leak detection method to determine the leakage rate. It meets the IP67 rating.

[0162] (v) Experimental verification and performance testing

[0163] Thermal response time test: A step temperature function is applied to a constant temperature platform, with the temperature increasing by a factor of 1 / 2. As the speed increases, an infrared thermal imager is used to record the center temperature of patch 13 and the start time of release.

[0164] Experimental data show that: when At that time, the microcapsule structure begins to expand; The first bubbles were released from the surface. It reaches a stable vaporization stage at this time. The average trigger delay is... Standard deviation This demonstrates good consistency.

[0165] Fire extinguishing effect test: Load the MC4 connector to This simulates localized heating caused by poor contact. In the experiment, the connector temperature was raised to [temperature value missing] by external heating. And ignite it by arc.

[0166] The control groups were:

[0167] Group Fire extinguishing equipment Response time (s) Complete fire extinguishing time (s) Whether it reignites Remark A No device -- -- yes Continued combustion B Document 2 Fire Extinguishing Disc 5.4 11.2 yes Unstable concentration C The device of the present invention 1.8 3.5 no No reignition

[0168] The results showed that the average extinguishing time of the present invention was only 3.5 seconds, and the concentration remained stable for 5 minutes after extinguishing without reignition, indicating that it is sensitive to thermal triggering, forms a concentration quickly, and maintains a stable concentration.

[0169] Long-term aging test: The sample was placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 1000 hours, and its perfluorohexanone retention rate was tested. The retention rate was determined by gas chromatography. The results showed no significant permeation in the microcapsule shell. Infrared spectroscopy analysis indicated that the amide bonds in the coating layer did not undergo significant breakage, suggesting that the material has good weather resistance.

[0170] (vi) Parameter stability and process window

[0171] To ensure consistency between different batches, the following three key process windows are defined:

[0172] Thermal response window: Trigger temperature Below 105℃, there is a risk of accidental triggering; above 115℃, fire suppression may be delayed. The microcapsule shell thickness should be controlled within... – This ensures stability within that range.

[0173] Sealed Leakage Window: Equivalent Ventilation Rate Too high a concentration will cause it to decay too quickly, while too low a concentration will cause pressure buildup, leading to premature valve diaphragm opening. Control is achieved by adjusting the labyrinth seal tooth depth and the seal compression ratio.

[0174] Thickness and drug content window: Coating thickness The corresponding single tablet contains medicine If the thickness is too thin, the medicine storage will be insufficient; if it is too thick, it will affect heat conduction.

[0175] Establish a multifactor regression model using DOE experimental design:

[0176] ;

[0177] in To determine the probability of successfully extinguishing the fire. is the regression coefficient.

[0178] Final Model The predicted optimal parameter set is: , , .

[0179] Verification has shown that with this parameter combination, the fire extinguishing success rate reaches 100%, and the response time is the shortest.

[0180] (vii) Weathering and lifespan testing

[0181] The samples underwent the following extreme environmental cycling tests:

[0182] project condition Loop count result High and low temperature cycling -40℃~85℃, 4 hours per cycle 500 No cracks, no leaks Salt spray test 5% NaCl, 35℃, 96h 1 Metal parts are free from corrosion UV aging UVA340, power 0.89W / m², 1000h 1 Casing ΔE<2 Vibration and shock 10–500Hz, 5g acceleration 1 Complete structure

[0183] After all tests, patch 13 maintained stable performance, with microcapsule integrity rate >98% and no significant decrease in fire extinguishing performance.

[0184] According to the Arrhenius accelerated life model:

[0185] ;

[0186] Assume the aging rate constant ratio Then the service life If the performance is maintained for 1000 hours under aging at 85℃, the lifespan at room temperature (25℃) is approximately 10,000 hours, or >1 year. Considering engineering margins, the device lifespan can reach 5 years.

[0187] (viii) Summary of preparation methods

[0188] Perfluorohexanone microcapsules were prepared using interfacial polymerization, with the shell thickness controlled. Microcapsules and silicone rubber are mixed at a mass ratio of 6:4, coated to a thickness of 0.55 mm, and then cross-linked and cured. An outer polyurethane protective layer is then applied. Control the gap of patch 13 during assembly. sealing rate After being filled with thermally conductive silicone grease and sealed with a labyrinth seal structure, the entire device can automatically release fire extinguishing gas when the MC4 connector overheats, thus achieving a self-starting fire extinguishing function.

[0189] In summary, based on the above analysis and verification, this invention possesses the following significant technical advantages:

[0190] This invention achieves active fire suppression, reignition prevention, and long-term stability performance that traditional MC4 connectors cannot provide through systematic structural design and material synergy. Its innovation lies in combining the thermally triggered release mechanism of perfluorohexanone microcapsules with the concentration maintenance system of the sealed cavity 12, enabling the fire suppression process to automatically initiate without external power supply. When the local temperature rise of the connector reaches a set threshold, the microcapsules rapidly rupture under the action of the thermally conductive interface, releasing perfluorohexanone and forming a localized high-concentration vapor environment, completing the fire suppression reaction within seconds. Because this process is entirely driven by heat conduction, the system does not require additional power supply or control circuitry, thus significantly improving reliability and independence.

[0191] Regarding the sealing system, a labyrinth seal structure combined with elastic seals forms a composite protection, ensuring that chamber 12 maintains stable airtightness even after release. Perfluorohexanone vapor maintains its extinguishing concentration within chamber 12 for an extended period, avoiding the concentration decay and reignition problems caused by leakage in conventional devices. Simultaneously, by incorporating a controllable one-way pressure relief structure at the sealing end, when the internal pressure of chamber 12 exceeds a safety threshold, some gas can be automatically released to balance the internal and external pressure difference, achieving a dynamic balance between concentration maintenance and pressure stability.

[0192] At the design level, this invention establishes for the first time a complete quantitative design system, achieving minimum vaporization mass. Maintaining supply quality and total load The calculation formulas for parameters enable precise matching of extinguishing agent dosage. This system not only makes the extinguishing effect predictable and verifiable, but also provides an engineering basis for structural adjustments under different chamber volumes and thermal conditions, transforming product development from empirical testing to calculable and reproducible engineering design.

[0193] In terms of manufacturing process, the preparation and integration of microcapsule patches 13 can be completed using conventional silicone rubber coating and molding equipment. The process is mature and the equipment is highly versatile. The overall assembly process of patch 13 and shell 1 does not require a high-pressure or vacuum environment, ensuring the stability and consistency of large-scale production. The production cost is low, making it suitable for mass promotion and application in industries such as photovoltaics, energy storage, and charging piles.

[0194] Furthermore, perfluorohexanone, as an environmentally friendly fire extinguishing agent with zero ozone depletion potential (ODP=0) and low global warming potential (GWP=1), leaves no corrosive residue after release and has no adverse effects on metal terminals, insulating materials, or sealant layers. It can maintain chemical stability and safety performance in outdoor conditions for more than ten years. Through the above-mentioned multi-level technological synergy, this invention fundamentally overcomes the limitations of traditional MC4 connector protection structures, which are only passively flame-retardant and cannot actively extinguish fires. It constructs a miniature fire extinguishing and protection system with self-response and self-inhibition functions, providing a long-term reliable safety protection solution for photovoltaic systems and other high-density electrical connection scenarios. It also relates to the manufacturing of other power transmission and distribution and control equipment, such as new energy (excluding non-motorized vehicles), ground AC, and underground AC charging piles.

[0195] Finally, it should be noted that the names of the method steps are for ease of description only and do not constitute a limitation on the order of the methods. Any cross-referencing or superposition of the various embodiments of this solution by those skilled in the art still falls within the original disclosure scope of this solution. Furthermore, the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention 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 the present invention should be included within the protection scope of the present invention.

Claims

1. A fire extinguishing device for photovoltaic cables using MC4 connectors, characterized in that, include: The housing (1) is hollow inside and is used to accommodate the MC4 connector. It has cable inlets (11) at both ends. When assembled and closed, it forms an effective volume of [missing information]. The sealed cavity (12); Perfluorohexanone microcapsule patch (13) is disposed on the inner wall of the housing (1) and arranged toward the predetermined heating area of ​​the MC4 connector; A composite sealing structure (14) is used to seal the housing (1) after assembly and closure; A limiting structure (15) is provided on the inner wall of the housing (1); as well as A thermally conductive interface material is disposed between the patch (13) and the MC4 connector, and its thermal conductivity and thickness after compression are configured to create an equivalent heat transfer gap. Limited to no more than the target thermal response time Equivalent thermal diffusivity of the interface The calculated maximum allowable value .

2. The fire extinguishing device according to claim 1, characterized in that, The composite sealing structure (14) and the shell (1) together increase the equivalent air exchange rate of the sealed cavity (12). Within the target range, the volume fraction of perfluorohexanone vapor in the cavity (12) is kept at or above the extinguishing threshold during the target maintenance time; The equivalent ventilation rate The volume fraction-time decay curve of perfluorohexanone within cavity (12) was obtained through exponential fitting and used for maintenance condition verification; the volume fraction-time relationship satisfies the following equation: ； in, For a moment volume fraction, This is the initial volume fraction. This is the equivalent ventilation rate; The composite sealing structure (14) includes a seal, and the housing (1) cooperates with the seal at the cable inlet (11) to form a meandering labyrinth sealing channel (111). After assembly, the seal forms multiple contact surfaces with the cable sheath and the cable inlet (11).

3. The fire extinguishing device according to claim 2, characterized in that, The shell (1) is a double-half split structure; the limiting structure (15) is integrally formed with the shell (1) as a limiting hook (151) and a limiting slot (152) distributed along the edge of the shell (1), which are used to fasten the shell (1) after the shell (1) is closed; Equivalent heat transfer gap Satisfy the following formula: ； in, For equivalent heat transfer gap, For the maximum permissible heat transfer gap, The equivalent thermal diffusivity of the interface. The target thermal response time; The thermal conductivity of the thermal interface material is not less than 1.0 W / (m·K), and the operating temperature range covers -40℃ to 180℃; The shell (1) has an inner and outer layer structure. The inner layer is made of heat-resistant insulating material, and the outer layer has a weather-resistant coating with a thickness of not less than 20μm to improve UV resistance and corrosion resistance. The patch (13) has a weather-resistant self-healing coating on its surface.

4. A high-security photovoltaic system, characterized in that, Includes an MC4 connector and a fire extinguishing device as described in any one of claims 1-3, wherein the MC4 connector is installed in the cavity (12).

5. A quantitative design method for perfluorohexanone microcapsule fire extinguishing devices used in the fabrication of MC4 connectors, characterized in that, Includes the following steps: Preset steps: Determine the volume of cavity (12) And set the target volume fraction Duration ; Preliminary step: Calculate the instantaneous target volume fraction based on the ideal gas law. Required instantaneous minimum vaporization mass ; Initial steps: After the housing (1) is assembled and closed, tracer gas is injected into the cavity (12) through the reusable calibration channel or dedicated calibration port of the labyrinth section of the cable inlet (11) to the initial volume fraction. Record the volume fraction-time data series and fit the data to obtain the equivalent ventilation rate. And calculate the maintenance supply quality. ; Metering steps: Determine the minimum vaporization mass With maintaining supply quality Summation and introduction of engineering margin factor To obtain the total load ; Conversion steps: Combine the effective area of ​​patch (13) Density of mixture With effective core material mass fraction Converting the thickness of the adhesive layer ; Calculation steps: Based on the unsteady-state thermal diffusion approximation, from the target response time... Equivalent thermal diffusivity of the interface By reverse calculation, the maximum allowable heat transfer gap can be obtained. Based on this, the limiting structure (15) and the thickness of the thermal interface material are designed.

6. The method according to claim 5, characterized in that, In the preliminary step, the instantaneous minimum vaporization mass is calculated according to equation (1): Equation (1): ; in, The instantaneous minimum vaporization mass, The pressure of cavity (12) (usually taken as standard atmospheric pressure). The effective volume of the cavity (12) after assembly. For the target volume fraction, The constant is 8.314 J·mol⁻¹·K⁻¹. Temperature at release (K) This refers to the molar mass of perfluorohexanone; In the initial steps, maintain the quality of the supply. Approximate the result using equation (2): Equation (2): ; in, To maintain the quality of supplies, For the minimum instantaneous vaporization mass, It is the equivalent ventilation rate (the reciprocal of time). The set duration; Total load According to formula (3), we get: Equation (3): ; in, For total load capacity, This is the engineering margin coefficient (dimensionless). For the minimum instantaneous vaporization mass, To maintain the quality of supplies; In the thickness calculation step, the thickness of the laminate is converted according to formula (4): Equation (4): ; in, For the thickness of the adhesive layer, The mass of pure perfluorohexanone in a single patch (13) For the effective coating area of ​​patch (13), For the density of the lamination mixture, The effective core material mass fraction in the mixture; The process window for the lamination thickness is set to ,occupy 2%-10%, of which The target thickness is set. This refers to the allowable range of thickness deviation.

7. The method according to claim 5, characterized in that, The maximum allowable heat transfer gap is calculated from equation (5) and used for structural design: Equation (5): ; in, For the maximum permissible heat transfer gap, The equivalent thermal diffusivity of the interface. The target thermal response time; The sensor used to determine the volume fraction of perfluorohexanone in cavity (12) has a range of not less than 10% VOL, an indication error of not more than ±0.1% VOL, and a sampling interval of not more than 1 s; the volume fraction-time relationship is obtained by fitting equation (6). : Equation (6): ; in, For a moment volume fraction, This is the initial volume fraction. It is the equivalent ventilation rate.

8. A method for manufacturing a high-security photovoltaic system as described in claim 4, characterized in that, Includes the following steps: Assembly and positioning steps: Before applying thermally conductive interface material, the nominal net radial distance between the contact surface of the patch (13) and the outer surface of the MC4 connector is defined as the geometric heat transfer gap. The MC4 connector is installed and positioned inside the cavity (12) of the housing (1), so that the geometric heat transfer gap is made. Controlled ; and confirmed by feeler gauge or non-contact optical measurement; Thermal interface layer setting steps: Apply thermal interface material evenly to the contact surface between the perfluorohexanone microcapsule patch (13) and the MC4 connector, and press-fit it under constant temperature conditions. The actual thickness after pressing is... With thermal conductivity Configured to jointly satisfy ,in For equivalent heat transfer gap, For the equivalent thermal diffusivity of the interface, The target thermal response time; Sealing assembly steps: The seal is embedded in the housing (1) and forms a labyrinth sealing channel (111) and multiple contact surfaces with the cable inlet (11) of the housing (1) to reduce leakage. The housing (1) is closed and locked by the limiting structure (15). Tracer charging procedure: With the chamber closed, tracer gas is charged into the cavity (12) to the initial volume fraction through the reusable calibration channel or dedicated calibration port of the labyrinth section of the cable inlet (11). ; Concentration verification steps: Record the volume fraction - time data column. ,according to The equivalent ventilation rate was obtained by fitting. And verify that the maintenance conditions are met. ,in For a moment volume fraction For the initial volume fraction, For equivalent ventilation rate, This represents the fire extinguishing threshold volume fraction. Loading setup steps: Based on The total perfluorohexanone loading was allocated to several patches (13), and according to Set the layer thickness, where For total load capacity, For engineering margin coefficient, For the instantaneous minimum vaporization mass, To maintain the quality of supplies, For the thickness of the adhesive layer, For the quality of a single pure perfluorohexanone tablet, For the effective coating area of ​​patch (13), For the density of the lamination mixture, The effective core material mass fraction in the mixture; Functional verification steps: Simultaneously monitor the interface thermal response and cavity (12) volume fraction under controlled heating, and confirm that the requirements are met. and ,in For interface thermal response time, For the target thermal response time, For a moment volume fraction This represents the fire extinguishing threshold volume fraction.

9. A method for implementing automatic fire extinguishing in a high-security photovoltaic system as described in claim 4, characterized in that, Includes the following steps: Preliminary conditions and steps: System assembly completed and meets the requirements. and ,in For equivalent heat transfer gap, For the equivalent thermal diffusivity of the interface, For the target thermal response time, For a moment volume fraction For the initial volume fraction, This is the equivalent ventilation rate; Thermal coupling triggering steps: When the temperature of the predetermined heating area of ​​the MC4 connector reaches the trigger threshold, the patch (13) microcapsule releases perfluorohexanone to achieve instantaneous concentration building up, and its minimum concentration building up is based on... Confirmed, among which For the instantaneous minimum vaporization mass, For the target volume fraction, For the pressure of cavity (12), For the effective volume of cavity (12), molar mass of perfluorohexanone For gas constant, Temperature at release; Concentration maintenance procedure: To combat leakage, a set maintenance time is set. Internal retention Maintain supply levels according to Settings, in which To maintain the quality of supplies, For the instantaneous minimum vaporization mass, For equivalent ventilation rate, To maintain time, For a moment volume fraction This represents the fire extinguishing threshold volume fraction. Reignition suppression steps: Maintain the volume fraction of cavity (12) not less than Until the fault is resolved or manual intervention is completed.

10. A highly adhesive thermally conductive interface material applied to the high-security photovoltaic system of claim 4, characterized in that, The material is an organosilicon adhesive composition used to form a thermally conductive adhesive layer between the perfluorohexanone microcapsule patch (13) and the MC4 connector and to achieve a thermally coupled and fixed connection. The composition consists of the following components in parts by weight: 60-120 parts of silicone resin base (containing vinyl-terminated polydimethylsiloxane and / or phenyl-modified polysiloxane). 0.5 to 5 parts of interface coupling modifier; The curing system (containing a crosslinking agent and a catalyst and configured to cure within 24 hours at a temperature not exceeding 60°C, with the peak self-heating temperature during curing not exceeding +20°C relative to the ambient temperature). 5 to 40 parts of thermally conductive filler, selected from one or more of boron nitride, aluminum nitride, flake graphite, graphene, alumina or copper powder, and surface-treated with silane coupling agent; 2-20 parts of flame retardant additive; and 0.2–3 parts of rheology conditioning and defoaming system; The strongly adhesive thermally conductive interface material has a Brinell viscosity of 5×10³ to 1×10³ at 25°C. 5 mPa·s.

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