Gel insulating medium power capacitor and preparation method thereof

Abstract

The invention discloses a preparation method of a gel insulating medium power capacitor, and belongs to the technical field of power capacitors, and the method comprises the steps: rolling a film and an electrode together to form elements, packaging a plurality of elements to form a capacitor core, and carrying out the vacuum drying pretreatment of the capacitor core; under a heating condition, injecting the modified polyurethane gel into the shell, so that the shell of the capacitor is completely filled with the gel; under a continuous heating condition, triggering a cross-linking reaction of the modified polyurethane gel, and performing in-situ curing to form a semi-solid gel medium layer; after the modified polyurethane gel is cooled and solidified, the shell is directly sealed and packaged, and an extra outer packaging layer does not need to be arranged. And the defects of leakage risk, environmental protection problem and high structural complexity of the traditional liquid impregnant are effectively overcome.

Description

Technical Field

[0001] The present invention belongs to the technical field of power capacitors, and particularly relates to a gel-insulated dielectric power capacitor and a preparation method thereof. Background Art

[0002] Traditional film power capacitors use liquid impregnants, such as mineral oil, ester liquids, benzyl toluene, etc., to fill and improve insulation performance. However, this design has some defects. First, the liquid impregnants are toxic and corrosive, and once leaked, they are likely to cause environmental pollution. Second, after the impregnants leak, air gaps will be generated inside the capacitor, resulting in a decline in insulation performance and thus triggering equipment failures. In addition, the commonly used liquid impregnants are flammable or combustion-supporting. Once a fire breaks out, it is easy for the fire to spread, presenting serious fire hazards. To overcome the above problems, a new structure of power capacitors needs to be developed. To ensure the insulation performance between the core and the shell, traditional designs require an additional outer encapsulation layer, increasing material costs and structural complexity. Therefore, there is an urgent need for a new insulating material and structural design to simplify the capacitor structure, improve reliability and environmental protection performance. Polyurethane is used as the insulating material between the core and the shell in flexible DC capacitors. This material has a certain elasticity, but there are still many air gaps and it is not suitable as the dielectric of power capacitors. Commonly used capacitor impregnants are all toxic and corrosive, and once leaked, they are likely to cause environmental pollution; after the impregnants leak, air gaps are generated inside the capacitor, resulting in a decline in insulation performance and causing equipment failures; the commonly used liquid impregnants at present are flammable or combustion-supporting, and once a fire breaks out, it is easy for the fire to spread, presenting serious fire hazards.

[0003] Although resin materials, such as polyurethane, show significant advantages in terms of environmental friendliness and structural simplification compared to traditional liquid impregnants, they also have inherent defects. Resin materials generally lack self-healing ability, which means that once microcracks or damages occur inside the material, they cannot repair themselves like organisms or some intelligent materials. As a result, the damages gradually accumulate, the insulation performance continuously decreases, and ultimately it may lead to the failure of the capacitor. This lack of self-healing ability limits the application of resin materials in the field of power capacitors that require high reliability and long life. Chinese Patent Application CN107275082A discloses a dry-type power electronic capacitor with a resin shell. The capacitor consists of a resin shell, a core, a terminal, and the filled resin. This application can solve the defects such as the leakage risk and environmental friendliness problems existing in traditional liquid impregnated capacitors, but there are still problems of further optimizing the core design, improving the insulation performance and heat resistance of the resin material. In addition, this application does not involve the improvement of the self-healing ability of the resin material, and the lack of self-healing ability is still the key factor restricting the further improvement of the performance of resin-based capacitors. Chinese Patent Application CN107275087A discloses a DC capacitor for an ultra-high power three-level inverter. The capacitor consists of a shell, a core, a terminal, the filled resin, and a pressure relief valve. This application can solve the defects such as the leakage risk and environmental friendliness problems existing in traditional liquid impregnated capacitors, but there are still problems of further optimizing the heat dissipation structure of the capacitor, improving the efficiency of the electrical outgoing copper foil and the connecting copper foil, and exploring the use of more advanced insulating materials. Similarly, this application also does not solve the problem of the lack of self-healing ability of the resin material, which is crucial for improving the operation reliability and extending the service life of the capacitor.

[0004] Regarding traditional liquid impregnated capacitors, there is a leakage risk. Once the impregnating agent leaks, it is easy to cause environmental pollution, equipment damage, and fire hazards. The structure of traditional liquid impregnated capacitors is complex. An additional outer encapsulation layer needs to be set to ensure the insulation performance between the core and the shell, increasing the material cost and structural complexity. Commonly used liquid impregnants such as mineral oil, ester liquids, benzyl toluene, etc. are all toxic and corrosive, which is not conducive to environmental protection. After the impregnating agent leaks, air gaps will be generated inside the capacitor, resulting in a decrease in insulation performance and triggering equipment failures. Currently, commonly used liquid impregnants have flammable or combustion-supporting characteristics. Once a fire breaks out, it is easy for the fire to spread, posing serious fire hazards. At the same time, although existing resin-based capacitors have solved many problems brought by liquid impregnants, the defect that the resin material itself lacks self-healing ability has not been solved. There is an urgent need to find a new film power capacitor using a high dielectric strength modified polyurethane gel as the insulating medium to solve the leakage risk, poor environmental friendliness, complex structure, decreased insulation performance, and fire hazards existing in existing liquid impregnated capacitors, and it also needs to have self-healing ability to further improve the reliability and service life of the capacitor. Summary of the Invention

[0005] In order to overcome the disadvantages of the above-mentioned existing technologies, the object of the present invention is to provide a gel-insulated dielectric power capacitor and a preparation method thereof, so as to solve the technical problems of leakage risk, environmental protection problems, high structural complexity existing in traditional liquid-impregnated capacitors, and the general lack of self-healing ability in existing resin materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions to be realized: The present invention discloses a preparation method of a gel-insulated dielectric power capacitor, including the following steps: Roll the film and the electrode together to form an element, pack multiple elements to form a capacitor core, perform vacuum drying pretreatment and vacuum impregnation on the capacitor core, spin-dry the excess impregnating agent, and then place it in the capacitor housing; Under heating conditions, inject the modified polyurethane gel into the capacitor housing to make the gel completely fill the capacitor housing; Under continuous heating conditions, trigger the cross-linking reaction of the modified polyurethane gel and in-situ cure to form a semi-solid gel dielectric layer; After the modified polyurethane gel cools down, directly seal the capacitor housing to obtain a gel-insulated dielectric power capacitor.

[0007] Preferably, the preparation method of the modified polyurethane gel includes the following steps: Mix the high-temperature cross-linking agent and the catalyst, and then mix with the polyurethane prepolymer. After high-speed dispersion, ultrasonic treatment and degassing treatment, obtain the precursor of the modified polyurethane gel; Inject the precursor of the modified polyurethane gel into a mold, and through heating and curing treatment, make the polyurethane prepolymer undergo a cross-linking reaction to obtain the modified polyurethane gel.

[0008] Further preferably, the mass ratio of the polyurethane prepolymer, the high-temperature cross-linking agent and the catalyst is 100:5:0.5; The high-temperature cross-linking agent is dicumyl peroxide; the catalyst is dibutyltin dilaurate.

[0009] Preferably, the dielectric strength of the modified polyurethane gel is ≥30 kV / mm, the thermal expansion coefficient is 50 - 200 ppm / °C, the Poisson's ratio is 0.2 - 0.4, and the Young's modulus is 0.05 - 0.5 GPa.

[0010] Preferably, the modified polyurethane gel has self-healing properties and the thermal expansion coefficient matches that of the metal housing.

[0011] Preferably, the film is made of polypropylene with a thickness of 5 - 40 μm, and the electrode is aluminum foil with a thickness of 4 - 10 μm.

[0012] Preferably, the temperature of vacuum drying is 65 °C, the vacuum degree is 5 - 15 Pa, and the time of vacuum drying is 3 - 8 h.

[0013] Preferably, the heating temperature for injecting the modified polyurethane gel into the capacitor housing is 55 - 60 °C.

[0014] Preferably, the heating temperature for the crosslinking reaction is 80 - 85 °C; the heating time for the crosslinking reaction is 3 - 5 h.

[0015] The present invention also discloses a gel-insulated dielectric power capacitor, which is prepared by using the above-mentioned preparation method of the gel-insulated dielectric power capacitor, and includes a capacitor housing, a capacitor core, and a modified polyurethane gel filled between the capacitor housing and the capacitor core.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a gel-insulated dielectric power capacitor, which uses a modified polyurethane gel as the internal insulating medium of the capacitor, cancels the outer encapsulation layer of the capacitor core, and directly uses the gel medium's own insulation and insulating performance to achieve direct insulation encapsulation between the core and the housing. This design can effectively solve the leakage risk, environmental protection problems, and high structural complexity defects existing in traditional liquid impregnants, thereby providing a thin-film power capacitor with strong reliability, environmental protection, and simplified structure. The gel medium simultaneously realizes insulation and encapsulation, breaking through the traditional separate design of "medium + structure". The heat curing process ensures gapless bonding between the gel and the core surface, avoiding partial discharge. The gel has a low Young's modulus and a large Poisson's ratio, which can fill the gaps of the capacitor core and also play a role in isolating the capacitor core from the housing. It is non-toxic and non-corrosive liquid, with better environmental protection performance; the gel self-healing property reduces the failure rate (the expected life is increased by 30%); after the structure is simplified, the material cost is reduced by 15%.

[0017] The present invention also discloses a gel-insulated dielectric power capacitor prepared by the above-mentioned preparation method, which uses a high-dielectric-strength modified polyurethane gel to replace the traditional liquid impregnants, cancels the outer encapsulation layer of the core, and directly uses the gel to achieve insulation encapsulation between the core and the housing, thereby significantly improving the reliability, environmental protection, and structural simplicity of the capacitor. The self-healing property of the gel medium can automatically repair minor defects, reduce the failure rate, and extend the service life; the non-toxic and non-corrosive gel avoids environmental pollution problems caused by liquid leakage; the simplified structure not only reduces the material cost but also eliminates the fire hazard caused by the flammability of traditional liquid impregnants; in addition, the gel's thermal expansion coefficient matching the metal housing effectively avoids mechanical stress caused by temperature changes, further improving the stability and service life of the capacitor. Description of the Drawings

[0018] Figure 1Schematic diagram of the preparation method of the gel insulation medium power capacitor disclosed by the present invention. Detailed implementation manners

[0019] The technical solutions of the present invention will be described clearly and completely below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0020] In the present invention, if there is no special explanation, all the implementation manners and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0021] In the present invention, if there is no special explanation, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0022] In the present invention, if there is no special explanation, the percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0023] In the present invention, if there is no special explanation, the various components or their preferred components involved can be combined with each other to form a new technical solution.

[0024] In the present invention, unless otherwise stated, the numerical range "a~b" represents the abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been fully listed herein, and "6~22" is only the abbreviated representation of these numerical combinations.

[0025] The "range" disclosed by the present invention can be in the form of one or more lower limits and one or more upper limits respectively.

[0026] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0027] In the present invention, unless otherwise stated, each reaction or operation step can be carried out sequentially or in sequence. Preferably, the reaction methods herein are carried out sequentially.

[0028] Unless otherwise stated, the professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0029] The present invention provides a preparation method of a gel insulation medium power capacitor, comprising the following steps: First, wind the metallized film into a cylindrical core, and perform vacuum drying pretreatment on the core.

[0030] Then, at a temperature of 55 - 60 °C, inject the modified polyurethane gel into the outer shell so that the gel completely fills the shell.

[0031] Next, trigger the cross - linking reaction of the gel by heating. The heating temperature for the cross - linking reaction is 80 - 85 °C and the time is 3 - 5 h, so that it in - situ cures to form a dense semi - solid gel dielectric layer.

[0032] Finally, after the gel cools and cures, directly seal the outer shell without setting an additional outer encapsulation layer.

[0033] The modified polyurethane gel has the advantages of high dielectric strength (≥30 kV / mm), self - healing property, and a thermal expansion coefficient matching that of the metal outer shell. Among them, the self - healing property can automatically fill in minor defects to prevent partial discharge; the matching of the thermal expansion coefficient can eliminate mechanical stress caused by temperature changes.

[0034] In addition, the present invention also adopts the following optimized designs: The component adopts a winding structure and is wound by special equipment, improving the space utilization rate of the outer shell; Adopt the process of impregnating the core and then centrifuging to dry it, which not only ensures the insulation inside the core but also avoids the flow of the impregnating agent.

[0035] The connecting copper foil is formed by die stamping, reducing the welding process and lowering the contact resistance and equivalent resistance; The gaps between components and between the core and the outer shell are all filled with gel, playing the role of insulation and mechanical buffering.

[0036] The present invention provides a gel - insulated dielectric power capacitor, which uses a modified polyurethane gel with high dielectric strength as the insulating medium. The capacitor includes a capacitor outer shell, a capacitor core, and the modified polyurethane gel filled in the capacitor outer shell.

[0037] The capacitor core is wound, with polypropylene as the main dielectric, having a thickness of 5 - 40 μm, and the electrode is aluminum foil with a thickness of 4 - 10 μm.

[0038] The surface of the capacitor core undergoes vacuum drying pretreatment to remove residual moisture. Then inject the modified polyurethane gel into the capacitor outer shell, with the temperature controlled at 55 - 60 °C, so that the gel completely covers the surface of the core. The dielectric strength of the used modified polyurethane gel is not less than 30 kV / mm, the thermal expansion coefficient is 50 - 200 ppm / °C, the Poisson's ratio is 0.2 - 0.4, and the Young's modulus is 0.05 - 0.5 GPa.

[0039] Next, heat the outer shell, control the temperature at 80 - 85 °C, and keep it for 3 - 5 h to trigger the cross-linking reaction of the gel, so that it in-situ cures to form a dense solid dielectric layer. The cured gel has self-healing properties and can automatically fill small defects to prevent partial discharge.

[0040] After the gel cools and cures, directly seal the outer shell without setting an additional outer encapsulation layer. The outer shell material is selected from aluminum alloy or stainless steel, which matches the thermal expansion coefficient of the gel to avoid mechanical stress caused by temperature changes.

[0041] The present invention also provides a method for preparing the above-mentioned gel-insulated dielectric power capacitor, and the specific steps are as follows: 1) The capacitor uses polypropylene as the main dielectric with a thickness of 5 - 40 μm, and the electrode is aluminum foil with a thickness of 4 - 10 μm; 2) Put the core into a vacuum drying oven, control the temperature at 65 °C, the vacuum degree at 5 - 15 Pa, and the vacuum drying time at 3 - 8 h; 3) Prepare a modified polyurethane gel, the main raw materials including polyurethane prepolymer, high-temperature cross-linking agent and catalyst, and the mass ratio of each substance is 100:5:0.5; the preparation method includes: Weigh an appropriate amount of polyurethane prepolymer and put it into a stirring container; add the high-temperature cross-linking agent to the polyurethane prepolymer according to the proportion and stir evenly; Add the catalyst according to the proportion and mix well after each addition until all substances are evenly mixed; The high-temperature cross-linking agent is dicumyl peroxide; the catalyst is dibutyltin dilaurate; 4) Inject the liquid gel into the aluminum alloy outer shell, control the temperature at 55 - 60 °C, so that the gel completely fills the capacitor outer shell; 5) Put the outer shell containing the gel and the core into a heating box at 80 - 85 °C for 3 - 5 h to make the gel cross-link and cure into a mold; 6) Take out the outer shell, naturally cool it to room temperature, and seal the outer shell to obtain the final power capacitor product.

[0042] The present invention also provides a gel-insulated dielectric power capacitor, which adopts a layered perfusion process and uses gels with different dielectric constants for different regions.

[0043] Specifically, first divide the core into an inner region and an outer region. The inner region refers to the central part of the core, and the outer region refers to the space between the core and the outer shell.

[0044] Then, first inject liquid gel into the outer shell, control the temperature at 55 - 60 °C, so that it completely fills the capacitor outer shell.

[0045] Then cure the low dielectric constant gel at 80 - 85 °C for 3 - 5 h to form a semi - solid gel - like dielectric layer.

[0046] This layered perfusion process can optimize the electric field distribution and improve the breakdown voltage of the capacitor. The high dielectric constant gel inside can withstand a higher electric field strength, while the low dielectric constant gel outside plays the role of insulation and buffering.

[0047] The present invention selects a modified polyurethane gel, which has: (1) High dielectric strength (≥30 kV / mm); (2) Self - healing property: Tiny defects can be automatically filled to prevent partial discharge; (3) The coefficient of thermal expansion matches that of the metal shell to eliminate mechanical stress; (4) Integrated insulation design: The modified polyurethane gel undertakes both dielectric insulation and mechanical buffering functions, replacing the traditional double - layer structure of "impregnant + outer encapsulation".

[0048] Gel - like dielectric replaces liquid impregnant: Use a gel - like material with high dielectric strength as the internal insulation dielectric of the capacitor to eliminate the risk of liquid leakage.

[0049] No outer encapsulation structure: Cancel the outer encapsulation layer of the capacitor core, and use the self - insulation performance of the gel dielectric to achieve direct insulation encapsulation between the core and the shell.

[0050] Other types of gels: Such as silicone gel, the curing process needs to be adjusted to adapt to high - temperature environments.

[0051] Layered perfusion: Use gels with gradient dielectric constants in different regions to optimize the electric field distribution.

[0052] A gel - insulated dielectric power capacitor provided by the present invention has strong reliability, environmental friendliness and a simplified structure. By using a high - dielectric - strength modified polyurethane gel as the insulation dielectric, triple breakthroughs in environmental friendliness, reliability and structural simplification are achieved: The gel dielectric eliminates the risk of partial discharge with its self - healing property and extends the life by 30%. At the same time, it replaces the traditional liquid impregnant to completely eliminate the leakage hidden danger; Its property that the coefficient of thermal expansion matches that of the metal shell and its physical property of low Young's modulus form a gap - free insulation encapsulation layer through the heat - curing process, enabling the direct combination of the capacitor core and the shell without an additional outer encapsulation structure. While simplifying the production process and reducing the material cost by 15%, it ensures excellent electric field distribution uniformity and mechanical buffering performance, and finally constructs a new type of thin - film power capacitor solution with high reliability, environmental friendliness and economy.

[0053] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0054] Figure 1 It is a schematic diagram of the preparation method of the gel-insulating medium power capacitor disclosed in the present invention. As can be seen from the figure, it includes the following steps: 1) Core pretreatment: Wind the metallized film into a cylindrical core and vacuum dry it. 2) Gel perfusion: Inject the liquid gel into the outer shell at 50°C to completely cover the surface of the core. 3) In-situ curing: Trigger the gel cross-linking reaction by heating to form a dense solid dielectric layer. 4) Sealed packaging: Directly package the outer shell after cooling without additional over-packaging. In the core pretreatment stage, it is necessary to strictly control the structure forming to ensure that the shape and size of the core meet the design requirements, and optimize the process parameters to improve efficiency and product quality. The gel perfusion process needs to finely manage the temperature conditions to ensure that the gel evenly covers the surface of the core and reaches the expected coverage quality. In the in-situ curing technical link, trigger the cross-linking reaction of the gel by heating and other means to form a dense solid dielectric layer, and ensure that the cured structure has excellent insulation performance and mechanical strength. In the sealed packaging optimization stage, it is necessary to follow strict cooling treatment specifications to ensure the sealing and stability of the packaged capacitor, improve the process efficiency, and reduce costs. These carefully designed steps and strict control measures jointly ensure the reliability, environmental protection and structural simplification of the new solid dielectric layer capacitor.

[0055] Example 1 A preparation method of a gel-insulating medium power capacitor includes the following steps: Roll a film with a thickness of 5 μm and an aluminum foil electrode with a thickness of 4 μm together to form an element. Pack multiple elements to form a capacitor core. Perform vacuum drying pretreatment and vacuum impregnation on the capacitor core. After spinning off the excess impregnating agent, place it in the capacitor outer shell; the temperature of the vacuum drying is 65°C, the vacuum degree is 5 Pa, and the time of the vacuum drying is 3 h.

[0056] Mix the high-temperature crosslinking agent dicumyl peroxide and the catalyst dibutyltin dilaurate, then mix with the polyurethane prepolymer. After high-speed dispersion, ultrasonic treatment and degassing treatment, a precursor of the modified polyurethane gel is obtained; the mass ratio of the polyurethane prepolymer, the high-temperature crosslinking agent and the catalyst is 100:5:0.5.

[0057] Inject the precursor of the modified polyurethane gel into a mold, and through heating and curing treatment, the heating temperature is 55 °C; make the polyurethane prepolymer undergo a crosslinking reaction to obtain the modified polyurethane gel; the dielectric strength of the modified polyurethane gel is 30 kV / mm, the thermal expansion coefficient is 50 ppm / °C, the Poisson's ratio is 0.2, and the Young's modulus is 0.05 GPa.

[0058] Under the heating condition of 55 °C, inject the modified polyurethane gel into the capacitor housing so that the gel completely fills the capacitor housing.

[0059] Under the continuous heating condition of 80 °C, trigger the crosslinking reaction of the modified polyurethane gel and in-situ cure to form a semi-solid gel dielectric layer; the heating time of the crosslinking reaction is 3 h.

[0060] After the modified polyurethane gel cools, directly seal and package the capacitor housing without setting an additional outer encapsulation layer, and a gel-insulated dielectric power capacitor is obtained.

[0061] Example 2 A preparation method of a gel-insulated dielectric power capacitor includes the following steps: Roll a film with a thickness of 10 μm and an aluminum foil electrode with a thickness of 6 μm together to form an element. Pack multiple elements to form a capacitor core. Perform vacuum drying pretreatment and vacuum impregnation on the capacitor core. After spinning off the excess impregnating agent, place it in the capacitor housing; the temperature of the vacuum drying is 65 °C, the vacuum degree is 10 Pa, and the time of the vacuum drying is 5 h.

[0062] Mix the high-temperature crosslinking agent dicumyl peroxide and the catalyst dibutyltin dilaurate, then mix with the polyurethane prepolymer. After high-speed dispersion, ultrasonic treatment and degassing treatment, a precursor of the modified polyurethane gel is obtained; the mass ratio of the polyurethane prepolymer, the high-temperature crosslinking agent and the catalyst is 100:5:0.5.

[0063] Inject the precursor of the modified polyurethane gel into a mold, and through heating and curing treatment, the heating temperature is 58 °C; make the polyurethane prepolymer undergo a crosslinking reaction to obtain the modified polyurethane gel; the dielectric strength of the modified polyurethane gel is 35 kV / mm, the thermal expansion coefficient is 100 ppm / °C, the Poisson's ratio is 0.3, and the Young's modulus is 0.1 GPa.

[0064] Under the heating condition of 58 °C, inject the modified polyurethane gel into the capacitor housing to make the gel completely fill the capacitor housing.

[0065] Under the continuous heating condition of 82 °C, trigger the cross-linking reaction of the modified polyurethane gel and in-situ cure to form a semi-solid gel dielectric layer; the heating time of the cross-linking reaction is 3.5 h.

[0066] After the modified polyurethane gel cools down, directly seal and package the capacitor housing without setting an additional outer encapsulation layer, and the gel-insulated dielectric power capacitor is obtained.

[0067] Example 3 A preparation method of a gel-insulated dielectric power capacitor includes the following steps: Roll a film with a thickness of 20 μm and an aluminum foil electrode with a thickness of 8 μm together to form an element, pack multiple elements to form a capacitor core, perform vacuum drying pretreatment and vacuum impregnation on the capacitor core, spin-dry the excess impregnating agent, and place it in the capacitor housing; the temperature of the vacuum drying is 65 °C, the vacuum degree is 12 Pa, and the time of the vacuum drying is 6 h.

[0068] Mix the high-temperature cross-linking agent dicumyl peroxide and the catalyst dibutyltin dilaurate, and then mix with the polyurethane prepolymer. After high-speed dispersion, ultrasonic treatment and degassing treatment, obtain the precursor of the modified polyurethane gel; the mass ratio of the polyurethane prepolymer, the high-temperature cross-linking agent and the catalyst is 100:5:0.5.

[0069] Inject the precursor of the modified polyurethane gel into a mold, and through heating and curing treatment, the heating temperature is 58 °C; make the polyurethane prepolymer undergo a cross-linking reaction to obtain the modified polyurethane gel; the dielectric strength of the modified polyurethane gel is 36 kV / mm, the thermal expansion coefficient is 180 ppm / °C, the Poisson's ratio is 0.35, and the Young's modulus is 0.3 GPa.

[0070] Under the heating condition of 58 °C, inject the modified polyurethane gel into the capacitor housing to make the gel completely fill the capacitor housing.

[0071] Under the continuous heating condition of 84 °C, trigger the cross-linking reaction of the modified polyurethane gel and in-situ cure to form a semi-solid gel dielectric layer; the heating time of the cross-linking reaction is 4 h.

[0072] After the modified polyurethane gel cools down, directly seal and package the capacitor housing without setting an additional outer encapsulation layer, and the gel-insulated dielectric power capacitor is obtained.

[0073] Example 4 A preparation method of a gel-insulated dielectric power capacitor includes the following steps: A film with a thickness of 40 μm and an aluminum foil electrode with a thickness of 10 μm are wound together to form a component. Multiple components are packed to form a capacitor core. The capacitor core is subjected to vacuum drying pretreatment and vacuum impregnation. After the excess impregnating agent is spun dry, it is placed in a capacitor housing; the temperature of the vacuum drying is 65 °C, the vacuum degree is 15 Pa, and the time of the vacuum drying is 8 h.

[0074] A high-temperature crosslinking agent, dicumyl peroxide, and a catalyst, dibutyltin dilaurate, are mixed, and then mixed with a polyurethane prepolymer. After high-speed dispersion, ultrasonic treatment, and degassing treatment, a precursor of a modified polyurethane gel is obtained; the mass ratio of the polyurethane prepolymer, the high-temperature crosslinking agent, and the catalyst is 100:5:0.5.

[0075] The precursor of the modified polyurethane gel is injected into a mold. Through heating and curing treatment, the heating temperature is 60 °C; the polyurethane prepolymer undergoes a crosslinking reaction to obtain a modified polyurethane gel; the dielectric strength of the modified polyurethane gel is 40 kV / mm, the thermal expansion coefficient is 200 ppm / °C, the Poisson's ratio is 0.4, and the Young's modulus is 0.5 GPa.

[0076] Under the heating condition of 60 °C, the modified polyurethane gel is injected into the capacitor housing to make the gel completely fill the capacitor housing.

[0077] Under the continuous heating condition of 85 °C, the crosslinking reaction of the modified polyurethane gel is triggered and in-situ cured to form a semi-solid gel dielectric layer; the heating time of the crosslinking reaction is 5 h.

[0078] After the modified polyurethane gel cools down, the capacitor housing is directly sealed without setting an additional outer encapsulation layer, and a gel-insulated dielectric power capacitor is obtained.

[0079] In summary, for a gel-insulated dielectric power capacitor and its preparation method according to the present invention, a thin-film power capacitor using a high-dielectric-strength modified polyurethane gel as an insulating medium, the power capacitor has excellent environmental performance, no toxic or corrosive liquids, avoiding environmental pollution problems caused by leakage of traditional liquid impregnating agents; the reliability is significantly improved, the gel medium has self-healing properties, can automatically fill small defects, reduce the local discharge failure rate, and the expected life is increased by 30%; the structure is simplified, the outer encapsulation layer of the capacitor core is cancelled, and the direct insulation encapsulation of the core and the housing is realized by using the self-insulating performance of the gel medium, and the material cost is reduced by 15%; the safety performance is enhanced, there is no flammable or combustion-supporting liquid, eliminating the risk of fire hazards caused by leakage of traditional liquid impregnating agents; the thermal stability is good, the thermal expansion coefficient of the gel matches that of the metal housing, avoiding mechanical stress caused by temperature changes, and improving the service life of the capacitor.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a gel-insulating medium power capacitor, characterized in that, It includes the following steps: Roll the film and the electrode together to form an element, pack multiple elements to form a capacitor core, conduct vacuum drying pretreatment and vacuum impregnation on the capacitor core, spin-dry the excess impregnating agent, and then place it in the capacitor housing; Under heating conditions, inject the modified polyurethane gel into the capacitor housing to make the gel completely fill the capacitor housing; Under continuous heating conditions, trigger the cross-linking reaction of the modified polyurethane gel and in-situ cure to form a semi-solid gel dielectric layer; After the modified polyurethane gel cools down, directly seal the capacitor housing to obtain a gel-insulated dielectric power capacitor.

2. The preparation method of the gel-insulated dielectric power capacitor according to claim 1, wherein The preparation method of the modified polyurethane gel includes the following steps: Mix the high-temperature cross-linking agent and the catalyst, and then mix with the polyurethane prepolymer. After high-speed dispersion, ultrasonic treatment and degassing treatment, obtain the precursor of the modified polyurethane gel; Inject the precursor of the modified polyurethane gel into the mold, and through heating and curing treatment, make the polyurethane prepolymer undergo a cross-linking reaction to obtain the modified polyurethane gel.

3. The preparation method of the gel-insulated dielectric power capacitor according to claim 2, wherein, The mass ratio of the polyurethane prepolymer, high-temperature cross-linking agent and catalyst is 100:5:0.5; The high-temperature cross-linking agent is dicumyl peroxide; the catalyst is dibutyltin dilaurate.

4. The preparation method of the gel-insulated dielectric power capacitor according to claim 1, characterized in that, The dielectric strength of the modified polyurethane gel is ≥30 kV / mm, the thermal expansion coefficient is 50 - 200 ppm / °C, the Poisson's ratio is 0.2 - 0.4, and the Young's modulus is 0.05 - 0.5 GPa.

5. The preparation method of the gel-insulated dielectric power capacitor according to claim 1, characterized in that, The modified polyurethane gel has self-healing properties, and its thermal expansion coefficient matches that of the metal housing.

6. The preparation method of the gel insulation medium power capacitor according to claim 1, characterized in that The film is made of polypropylene with a thickness of 5 - 40 μm, and the electrode is aluminum foil with a thickness of 4 - 10 μm.

7. The preparation method of the gel-insulated dielectric power capacitor according to claim 1, characterized in that, The temperature of the vacuum drying is 65 °C, the vacuum degree is 5 - 15 Pa, and the time of the vacuum drying is 3 - 8 h.

8. The preparation method of the gel insulation medium power capacitor according to claim 1, characterized in that, The heating temperature for injecting the modified polyurethane gel into the capacitor housing is 55 - 60 °C.

9. The preparation method of the gel insulation medium power capacitor according to claim 1, characterized in that, The heating temperature of the cross-linking reaction is 80 - 85 °C; the heating time of the cross-linking reaction is 3 - 5 h.

10. A gel-insulating medium power capacitor, characterized in that, Prepared by using the preparation method of the gel-insulated dielectric power capacitor according to any one of claims 1 - 9, including a capacitor housing, a capacitor core, and a modified polyurethane gel filled between the capacitor housing and the capacitor core.

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