Dry-type overpressure explosion-proof capacitor and preparation method and explosion-proof performance test method thereof

Abstract

The invention provides a dry-type overpressure explosion-proof capacitor, a preparation method thereof and an explosion-proof performance test method. The dry-type overpressure explosion-proof capacitor comprises an electrode assembly, the electrode assembly comprises an electrode core, a lead and a wire outlet terminal, the lead is used for connecting the electrode core and the wire outlet terminal, at least one explosion-proof point is arranged on the lead, and the explosion-proof point comprises at least one of a mechanical notch and a welding point. According to the dry-type overpressure explosion-proof capacitor provided by the invention, the mechanical gaps and / or the welding spots are arranged on the leads used for connecting the electrode cores and the outgoing line terminals to serve as explosion-proof points, the explosion-proof points are weak points of mechanical tension, and under the action of the tension, the explosion-proof points can be preferentially snapped compared with other parts of the leads, so that external power supply input is cut off, the explosion-proof effect is achieved, and the service life of the dry-type overpressure explosion-proof capacitor is prolonged. Compared with an oil type over-pressure explosion-proof capacitor, the dry type over-pressure explosion-proof capacitor provided by the invention can avoid the oil leakage problem and the problems of environmental pollution, equipment safety and the like caused by oil leakage.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and particularly relates to a dry overpressure explosion-proof capacitor, a preparation method thereof, and an explosion-proof performance testing method. Background Art

[0002] Oil-immersed capacitors mainly use a metal shell and are filled with insulating oil through a vacuum impregnation process. The insulating oil inside is generally mainly vegetable oil or mineral oil. Oil-immersed capacitors have been widely used in fields such as reactive power compensation and AC filtering due to their characteristics of low temperature rise and long service life. However, there are also inevitable oil leakage problems and many problems such as environmental pollution and equipment safety caused by oil leakage.

[0003] Compared with oil-immersed capacitors, dry capacitors have the advantages of no oil leakage, higher safety, and environmental friendliness. Dry capacitors do not use environmentally harmful chemicals during the production process and are considered environmentally friendly capacitor products. With the development of technology, the application range of dry capacitors is gradually expanding and is expected to gradually replace oil-immersed capacitors in the future.

[0004] The explosion-proof function is a very important performance of capacitors. Especially for capacitors with a large volume and large capacity, once such capacitors explode, the energy generated and the damage caused are extremely large. Therefore, the reliability of the explosion-proof function of capacitors is very important. The explosion-proof of capacitors requires tensile force because it uses mechanical tensile force to pull apart the electrodes of the capacitor, making the capacitor in an open circuit state, thereby avoiding capacitor breakdown or short circuit caused by too high voltage or overheating, and thus achieving the purpose of explosion-proof.

[0005] Existing dry overpressure explosion-proof capacitors usually use mechanical tensile force to pull apart the electrodes of the capacitor, mainly using the force of gas expansion as the tensile force for breaking the lead wire, making the capacitor in an open circuit state, thereby avoiding capacitor breakdown or short circuit caused by too high voltage or overheating. When the voltage is too high or the heat generation is too large, the gas inside the capacitor expands, causing the outer shell to deform and bulge, thereby breaking the electrode connection wire (i.e., the lead wire), disconnecting the capacitor, and preventing short circuit of the circuit. However, when the mechanical tensile force is insufficient or the degree of gas expansion inside the capacitor is low, the lead wire is not easily broken, resulting in the explosion-proof failure of the dry overpressure explosion-proof capacitor. Summary of the Invention

[0006] The present invention provides a dry overpressure explosion-proof capacitor, a preparation method thereof, and an explosion-proof performance testing method. The dry overpressure explosion-proof capacitor can achieve safe and reliable explosion-proof on the premise of ensuring no oil leakage.

[0007] According to the first aspect of the present invention, a dry overpressure explosion-proof capacitor is provided. The dry overpressure explosion-proof capacitor includes an electrode assembly, and the electrode assembly includes an electrode core, a lead wire, and an outlet terminal. The lead wire is used to connect the electrode core and the outlet terminal, and at least one explosion-proof point is provided on the lead wire. The explosion-proof point includes at least one of a mechanical notch and a solder joint.

[0008] In the dry overpressure explosion-proof capacitor provided by the present invention, by providing a mechanical notch and / or a solder joint as an explosion-proof point on the lead wire for connecting the electrode core and the outlet terminal, first, relative to the entire lead wire, the explosion-proof point is a weak point of mechanical tension. Under the action of tension, it can be broken preferentially compared with other parts of the lead wire. And due to the existence of the explosion-proof point, the lead wire is easy to be broken even under mechanical tension or when the internal expansion degree of the capacitor is relatively low, so as to cut off the external power input and achieve the explosion-proof effect, making the capacitor safer and more reliable. Second, compared with the oil-type overpressure explosion-proof capacitor, the dry overpressure explosion-proof capacitor provided by the present invention can avoid problems such as oil leakage and various problems brought about by oil leakage, such as environmental pollution and equipment safety. Thus, the dry overpressure explosion-proof capacitor provided by the present invention can achieve safe and reliable explosion-proof on the premise of ensuring no oil leakage.

[0009] The explosion-proof point can be formed by stamping, wire cutting, laser cutting, shearing and other methods, and the position of the explosion-proof point can be set at any position on the lead wire. The contact area near the mechanical notch or the solder joint is smaller than that at the non-mechanical notch or non-solder joint position, and the temperature rise is slightly higher. However, the lead wire is generally made of copper, and its thermal conductivity is good, so the influence on the temperature rise of the capacitor is not great. And during the subsequent assembly process of the dry overpressure explosion-proof capacitor, in order to prevent the lead wire containing the explosion-proof point from breaking at the explosion-proof point, an insulating rigid sleeve slightly larger than the lead wire size can be sleeved outside the explosion-proof point or a substance that is solid at room temperature (to protect the explosion-proof point) and melts into a liquid or becomes soft at high temperature (without affecting the tension), such as microcrystalline wax or low melting point polycaprolactone with a melting point of 45°C to 105°C, can be coated.

[0010] Preferably, the above-mentioned dry overpressure explosion-proof capacitor further includes an upper positioning sleeve, a lower positioning sleeve, a positioning assembly, and a pole shell. The upper positioning sleeve covers the upper end face of the electrode assembly, the lower positioning sleeve covers the lower end face of the electrode assembly, and the positioning assembly is used to fix the electrode assembly; the materials of the upper positioning sleeve, the lower positioning sleeve, the positioning assembly, and the pole shell independently include at least one of polyimide, mica paper, phenolic composite material, epoxy resin composite material, and unsaturated polyester composite material.

[0011] The commonly used polymer dielectric film in the capacitor is polypropylene. Polypropylene will undergo melting decomposition when the capacitor fails, and its melting temperature is about 165°C, and the 5% thermal decomposition temperature (the temperature at which the mass of polypropylene decreases by 5% due to the action of heat) can be as high as 400°C.

[0012] The upper positioning sleeve, lower positioning sleeve, positioning component and pole housing in the dry overpressure explosion-proof capacitor involved in this solution are all made of the above-mentioned high heat-resistant insulating material, so that the upper positioning sleeve, lower positioning sleeve, positioning component and pole housing can all pass the glow wire test at 400°C. When the capacitor fails, it can reduce the risk of the polymer dielectric film in the capacitor melting and decomposing and melting through the upper positioning sleeve, lower positioning sleeve, positioning component and pole housing, and further improve the explosion-proof success rate of the capacitor.

[0013] If the insulating materials used for the upper positioning sleeve, lower positioning sleeve, positioning component and pole housing do not have high heat resistance and cannot pass the glow wire test at 400°C, it is easy to occur that when the capacitor fails to explode successfully, the melt formed by the melting and decomposition of the polymer dielectric film in the capacitor has already insulated and melted through the upper positioning sleeve, lower positioning sleeve, positioning component and pole housing, and then a short circuit occurs between the electrode core and the outer shell, resulting in explosion-proof failure or fire.

[0014] Preferably, the materials of the upper positioning sleeve, lower positioning sleeve, positioning component and pole housing are all polyimide or mica paper.

[0015] Preferably, the above-mentioned dry overpressure explosion-proof capacitor further includes a cylindrical outer shell. The electrode assembly and the pole housing are fixed inside the cylindrical outer shell. The bottom thickness of the cylindrical outer shell is above 1.0 mm, and the circumferential side wall thickness of the cylindrical outer shell is above 0.6 mm.

[0016] Controlling the bottom thickness and side wall thickness of the cylindrical outer shell of the dry overpressure explosion-proof capacitor within the above ranges, first, it can ensure the pressure-bearing capacity of the capacitor, cover the air pressure value during capacitor explosion-proof, and make the capacitor not easily crack during the explosion-proof process. Second, the side wall thickness of the cylindrical outer shell also undertakes the function of pressing the electrode assembly. Therefore, when the side wall thickness of the cylindrical outer shell is controlled within the above range, when the bottom of the capacitor is broken down, it can improve the explosion-proof success rate. Third, it can control the cost and quality of the outer shell within an appropriate range.

[0017] Preferably, at least one inward groove is provided on the surface of the cylindrical outer shell near the upper positioning sleeve. The groove is used to press the electrode core, and the depth of the groove is above 5 mm.

[0018] The groove provided on the cylindrical outer shell of the dry overpressure explosion-proof capacitor in this solution is located on the upper end face of the electrode core. During normal operation, this groove is used to press the electrode core. During the explosion-proof process, on the one hand, it is used to press the electrode core to prevent the overall upward movement of the electrode core. On the other hand, if the lower end face of the electrode core is severely broken down and the electrode core must move upward, the flattened groove will be pulled open or even flattened, providing a buffer space for the electrode core and the gas generated by explosion-proof breakdown, and avoiding explosion-proof failure.

[0019] For capacitors with a small diameter (e.g., a diameter below 76 mm), since the air pressure required to achieve explosion protection due to the deformation and bulging of the finished cover plate is relatively large, and the length of the groove cannot be too long, the probability of the groove being pulled open and flattened is very high. In this case, two grooves will be set up when necessary.

[0020] Preferably, potting glue is filled between the cylindrical shell and the electrode assembly, and the gel strength of the potting glue is 50 - 1500 g.

[0021] Preferably, the potting glue includes at least two of epoxy resin, epoxy soybean oil, castor oil, diphenylmethane diisocyanate (MDI), and methyltetrahydrophthalic anhydride.

[0022] Compared with liquid insulating oil, in this solution, the potting glue with a gel strength within the above range and containing the above components is used to fill the gap between the cylindrical shell and the electrode assembly, which can have a certain obstructive effect on the gas generated by dielectric breakdown.

[0023] When dielectric breakdown occurs in the lower electrode core (for multiple electrode cores) or the lower part of the electrode core (especially for multi-inner-strung electrode cores), the gas generated by the dielectric needs to accumulate to generate a certain pressure before it can penetrate into the reserved explosion-proof space. At this time, a relatively large air pressure will be generated on the circumferential side of the cylindrical shell. If the side wall thickness of the shell is relatively thin and the pressure-bearing capacity is insufficient, the circumferential side of the shell will crack first, resulting in the failure of explosion protection. Therefore, after filling the gap between the cylindrical shell and the electrode assembly with potting glue, it is necessary to select a high heat-resistant pole shell insulating material that can withstand the melting temperature of the dielectric to ensure that the electrode core and the shell will not be directly short-circuited to cause the failure of explosion protection, and reserve enough time for the gas to accumulate until a sufficient air pressure is generated to penetrate the potting glue or diffuse along the surface of the potting glue and the electrode core to the reserved explosion-proof space, providing key support for ensuring reliable explosion protection.

[0024] Preferably, the potting glue is selected from one of the following combinations:

[0025] Combination 1: Epoxy resin, castor oil, and diphenylmethane diisocyanate (MDI) with a mass ratio of 80 - 180:25:6 - 10;

[0026] Combination 2: Epoxy soybean oil, castor oil, and diphenylmethane diisocyanate (MDI) with a mass of 80 - 180:25:6 - 10;

[0027] Combination 3: Epoxy soybean oil and epoxy resin with a mass ratio of 80 - 180:25;

[0028] Combination 4: Epoxy soybean oil and methyltetrahydrophthalic anhydride with a mass ratio of 100:10 - 50.

[0029] The components and their contents in the gel - state potting material used to form the potting compound are regulated so that the potting compound formed after the gel - state potting material cures (the cured gel - state potting material does not resume flowing at 150 °C and does not resume becoming liquid at 180 °C - 200 °C) has poor bulk strength, poor interfacial adhesion, and is gas - permeable. This can ensure that the gas generated when the dielectric breaks down the capacitor can quickly penetrate into the explosion - proof reserved space. At the same time, it has the characteristics of no corrosion to the metal coating of the electrode core and no swelling to the dielectric film. After potting, the capacitor has no oil - leakage problem and can better meet the explosion - proof requirements of the capacitor.

[0030] If the content of epoxidized soybean oil and epoxy resin in the gel - state potting material is too high, or the content of diphenylmethane diisocyanate is too low, the gel - state potting material will cure poorly. If the content of epoxidized soybean oil and epoxy resin is too low, or the content of methyltetrahydrophthalic anhydride is too high, the strength and hardness of the potting compound formed after the gel - state potting material cures will be too high, making it difficult to meet the explosion - proof requirements.

[0031] Preferably, the potting compound further includes molecular sieve activated powder and nano - thermal conductive filler. The nano - thermal conductive filler includes at least one of boron nitride, silicon oxide, and aluminum oxide. The mass ratio of the molecular sieve activated powder in the potting compound is 0.5 - 5%, and the mass ratio of the nano - thermal conductive filler in the potting compound is 0.5 - 2%.

[0032] Preferably, the nano - thermal conductive filler includes at least one of nano - boron nitride, nano - silicon oxide, and nano - aluminum oxide.

[0033] According to the second aspect of the present invention, a method for preparing a dry - type over - pressure explosion - proof capacitor is provided, including the following steps:

[0034] S1. Deposit a metal layer on one surface of the polymer dielectric film to obtain a metallized film. Stack at least two metallized films in a staggered manner in the width direction and then wind them around a mandrel so that the wound metallized film wraps the mandrel to obtain an electrode core.

[0035] S2. Perform a heat - setting treatment on the electrode core.

[0036] S3. Perform a gold - spraying treatment on the end faces of the electrode core that has undergone the heat - setting treatment.

[0037] S4. Connect the electrode core that has undergone the gold - spraying treatment to the outgoing terminal using leads, and set at least one mechanical notch and / or solder joint on the leads to form an electrode assembly.

[0038] S5. Install the electrode assembly into the housing, inject the gel-like potting material into the interior of the housing, and after the gel-like potting material is cured, it forms potting glue, thus obtaining a dry overpressure explosion-proof capacitor. Among them, the gel-like potting material includes at least two of epoxy resin, epoxidized soybean oil, castor oil, diphenylmethane diisocyanate, and methyltetrahydrophthalic anhydride.

[0039] In the preparation method of the dry overpressure explosion-proof capacitor provided by this solution, after the electrode core obtained by winding the metallized film around the mandrel is heat-set and gold-sprayed, the electrode core is connected to the outgoing terminal by using a lead wire with mechanical notches and / or solder joints to form an electrode assembly, and then it is prepared by injecting with the gel-like potting material containing the above components and curing. The dry overpressure explosion-proof capacitor obtained through the above steps can achieve safe and reliable explosion protection on the premise of ensuring no oil leakage.

[0040] Preferably, S5 includes the following operations:

[0041] S5-1. Dehydrate the raw materials for preparing the gel-like potting material under the conditions of a temperature of 90-120°C and a vacuum degree below -0.09 MPa until the moisture content is below 150 ppm;

[0042] S5-2. Mix the raw materials that have undergone vacuum dehydration evenly to obtain the gel-like potting material;

[0043] S5-3. Install the electrode assembly into the housing and keep it for 0.5-2 min under the condition that the vacuum degree is less than -0.09 MPa, then inject the gel-like potting material into the interior of the housing, and after curing, it forms potting glue, thus obtaining a dry overpressure explosion-proof capacitor.

[0044] During the perfusion process using the gel-like potting material, first, by dehydrating the raw materials for preparing the gel-like potting material and adjusting the temperature and vacuum degree within the above ranges, the moisture content of each raw material is reduced to below 150 ppm, which can reduce the corrosion risk of the metal coating in the electrode core and ensure the capacitance of the finally obtained capacitor. Second, by evacuating the electrode assembly before potting and controlling the vacuum degree and treatment time within the above ranges, the moisture adsorbed inside the electrode assembly can be removed, thereby reducing the risk of attenuation of the capacitance of the finally obtained capacitor.

[0045] If the temperature or vacuum degree used in the dehydration treatment of the raw materials for preparing the gel - state potting compound is too low, the dehydration time will be too long, or the dehydration standard cannot be achieved, resulting in too high water content in the potting compound, corroding the metal coating of the electrode core component, attenuating the capacitance value of the capacitor, and increasing the tangent value of the loss angle. If the temperature used in the dehydration treatment of the raw materials for preparing the gel - state potting compound is too high, it will cause thermal oxidative degradation of epoxy soybean oil, epoxy resin, and castor oil, increasing the acid value, attenuating the capacitance value of the capacitor, and increasing the tangent value of the loss angle.

[0046] Preferably, in S5 - 3, after injecting the gel - state potting compound into the interior of the housing, evacuate with nitrogen and cure the gel - state potting compound at 80 - 95 °C for 2 - 4 hours.

[0047] During the injection molding process of the gel - state potting compound, choosing nitrogen evacuation can prevent moisture in the air from entering the capacitor, reducing the corrosion risk of the gel - state potting compound to the metal coating in the electrode core.

[0048] According to the third aspect of the present invention, there is provided a method for testing the explosion - proof performance of the above - mentioned dry - type over - pressure explosion - proof capacitor, including the following steps:

[0049] S1. Embedding a conductor in the vertical film layer on the electrode core or using a DC voltage to break down the electrode core to obtain a semi - finished product;

[0050] S2. Assembling the semi - finished product with other components into a dry - type over - pressure explosion - proof capacitor;

[0051] S3. After heating the dry - type over - pressure explosion - proof capacitor to 40 - 105 °C, applying an AC voltage V1 to the outgoing line terminal of the dry - type over - pressure explosion - proof capacitor and maintaining it for 5 min - 8 h, testing the current of the outgoing line terminal and the capacitance of the dry - type over - pressure explosion - proof capacitor, where the rated working voltage of the dry - type over - pressure explosion - proof capacitor is V2, and V1 and V2 satisfy V1 = 1.3 - 1.5V2;

[0052] S4. Evaluating the explosion - proof performance of the dry - type over - pressure explosion - proof capacitor by combining the current of the outgoing line terminal, the capacitance of the dry - type over - pressure explosion - proof capacitor, the appearance of the dry - type over - pressure explosion - proof capacitor, and the fire - starting situation.

[0053] The existing explosion-proof test method for dry overpressure explosion-proof capacitors is to first apply a DC voltage between the outgoing terminals of the capacitor to cause the electrode core to break down, and then apply an AC voltage. During this process, when the DC voltage is applied to cause the electrode core to break down, the position where the electrode core breaks down is random. Any position or multiple positions on the upper end face, middle part, side face, and lower end face of the electrode core may break down. Therefore, it is difficult to simulate the most severe phenomenon of "breakdown of the lower end face of the electrode core" that occurs in the actual working condition, that is, the position where the gas penetration length is the longest. It can be seen that when using the existing explosion-proof test method to detect dry overpressure explosion-proof capacitors, even capacitors that pass the existing explosion-proof test may experience explosion-proof failure during actual application. That is, the existing explosion-proof test method has inaccurate problems in evaluating the explosion-proof performance of dry overpressure explosion-proof capacitors.

[0054] Compared with the existing explosion-proof test method for dry overpressure explosion-proof capacitors, the explosion-proof performance test method for dry overpressure explosion-proof capacitors provided by this solution embeds a conductor in the vertical film layer on the electrode core or uses a DC voltage to break down the electrode core. By artificially creating an electrical weak point at the farthest end of the electrode core, it can well simulate the most severe working conditions that may occur in the actual working condition of the capacitor, improve the accuracy of the explosion-proof test results, and make the dry overpressure explosion-proof capacitors passing the explosion-proof performance test provided by this solution safer during actual operation. Specific embodiments

[0055] The following further clearly and completely describes the technical features in the technical solution provided by the present invention in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0056] Embodiment 1

[0057] A dry overpressure explosion-proof capacitor is prepared through the following steps:

[0058] S1. Deposit a metal layer on one surface of a polymer dielectric film (polypropylene film) to obtain a metallized film. Stack at least two metallized films with a dislocation in the width direction and then wind them along a mandrel so that the wound metallized film wraps the mandrel (polycarbonate) to prepare an electrode core.

[0059] S2. Perform heat setting treatment on the electrode core.

[0060] S3. Perform gold spraying treatment on the end faces of the electrode core after heat setting treatment.

[0061] S4. Use leads to weld the electrode cores that have undergone gold spraying treatment to the outgoing line terminals correspondingly, and set at least one mechanical notch on the leads by means of laser cutting to form an electrode assembly;

[0062] S5. Pre-bake, potting, and crimping and sealing the holes

[0063] S5-1. Dehydrate the raw materials (140 parts by weight of epoxy resin, 25 parts by weight of castor oil, 6 parts by weight of MDI, 3 parts by weight of molecular sieve activated powder, 1.5 parts by weight of nano boron nitride) for preparing the gel-like potting compound at a temperature of 105°C and a vacuum degree of -0.09 MPa until the water content is below 150 ppm;

[0064] S5-2. Mix the above raw materials that have undergone vacuum dehydration treatment evenly to obtain a gel-like potting compound;

[0065] S5-3. Put the upper positioning sleeve, lower positioning sleeve, positioning assembly (positioning clip), and pole housing on the outside of the electrode assembly, and then integrally install them into a cylindrical housing with a bottom thickness of 1.0 mm and a circumferential side wall thickness of 0.6 mm. Use a grooving machine to roll an inward groove with a depth of more than 5 mm on the cylindrical housing near the upper part of the upper positioning sleeve, and then use a tooling to flatten it and press the electrode core tightly to obtain a semi-finished product. Then, after pre-baking the semi-finished product, place the pre-baked semi-finished product in a vacuum perfusion machine and keep it for 1 min under the condition that the vacuum degree is less than -0.09 MPa, and then inject the gel-like potting compound into the inside of the cylindrical housing. After curing, it forms potting glue. Pass the lead through the finished product cover hole (composed of components such as an insulating terminal seat, a metal cover plate, an insulating base, an insulating seal, metal rivets, and metal electrode plates), and then use a crimping machine to perform double crimping and use solder to seal the holes to obtain a dry overpressure explosion-proof capacitor;

[0066] Among them, the materials of the upper positioning sleeve, lower positioning sleeve, positioning clip, and pole housing are all polyimide.

[0067] Example 2

[0068] This example provides a dry overpressure explosion-proof capacitor. Compared with Example 1, the difference in composition is that in the preparation step S4 of the dry overpressure explosion-proof capacitor, solder joints are used to replace the mechanical notches on the leads. Except for the above differences, the materials, formula ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0069] Example 3

[0070] In Experimental Groups A - F of Example 3, a dry overpressure explosion - proof capacitor is provided. Compared with Example 1, the difference in composition is that in preparation step S5 - 3 of the dry overpressure explosion - proof capacitor, the materials of the lower positioning sleeve and the pole housing are different, as shown in Table 1 specifically. Except for the above - mentioned differences, the materials, formula ratios, and preparation operations used in Experimental Groups A - F of this example are strictly the same as those in Example 1.

[0071] Table 1 Materials of the lower positioning sleeve and the pole housing in Experimental Groups A - F of Example 3

[0072]

[0073]

[0074] Example 4

[0075] In Experimental Groups a - d of this example, a dry overpressure explosion - proof capacitor is provided. Compared with Example 1, the difference in composition is that in preparation step S5 - 3 of the dry overpressure explosion - proof capacitor, the bottom thickness and the circumferential side - wall thickness of the cylindrical shell are different, as shown in Table 2 specifically. Except for the above - mentioned differences, the materials, formula ratios, and preparation operations used in Experimental Groups a - d of this example are strictly the same as those in Example 1.

[0076] Table 2 Bottom thickness and circumferential side - wall thickness of the cylindrical shell in Experimental Groups a - d of Example 4

[0077]

[0078] Example 5

[0079] In this example, a dry overpressure explosion - proof capacitor is provided. Compared with Example 1, the difference in composition is that in preparation step S5 - 3 of the dry overpressure explosion - proof capacitor, two grooves with a depth of more than 5 mm are rolled inward on the cylindrical shell near the upper part of the upper positioning sleeve by a grooving machine. Except for the above - mentioned differences, the materials, formula ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0080] Example 6

[0081] In Experimental Groups ① - ⑧ of this example, a dry overpressure explosion - proof capacitor is provided. Compared with Example 1, the difference in composition is that in preparation step S5 - 1 of the dry overpressure explosion - proof capacitor, the raw material composition of the gel - state potting compound is different, as shown in Table 3 specifically. Except for the above - mentioned differences, the materials, formula ratios, and preparation operations used in Experimental Groups ① - ⑧ of this example are strictly the same as those in Example 1.

[0082] Table 3 Raw material composition of the gel - state potting compound in Experimental Groups ① - ⑧ of Example 6

[0083]

[0084]

[0085] Example 7

[0086] This example provides a dry overpressure explosion-proof capacitor. Compared with Example 1, the difference in composition is that in the preparation step S5-1 of the dry overpressure explosion-proof capacitor, the temperature used for dehydrating the raw materials for preparing the gel-like potting compound is 100 °C, and the vacuum degree is -0.0990 MPa. Except for the above differences, the materials, formula ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0087] Example 8

[0088] This example provides a dry overpressure explosion-proof capacitor. Compared with Example 1, the difference in composition is that in the preparation step S5-1 of the dry overpressure explosion-proof capacitor, the temperature used for dehydrating the raw materials for preparing the gel-like potting compound is 125 °C. Except for the above differences, the materials, formula ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0089] Example 9

[0090] This example provides a dry overpressure explosion-proof capacitor. Compared with Example 1, the difference in composition is that in the preparation step S5-3 of the dry overpressure explosion-proof capacitor, the pre-baked semi-finished product is placed under atmospheric pressure for perfusion. Except for the above differences, the materials, formula ratios, and preparation operations used in this example are strictly the same as those in Example 1.

[0091] Example 10

[0092] A method for testing the explosion-proof performance of a dry overpressure explosion-proof capacitor includes the following steps:

[0093] S1. Embedding a conductor in the vertical film layer on the electrode core or using a DC voltage to break down the electrode core to obtain a semi-finished product;

[0094] S2. Assembling the semi-finished product with other components into a dry overpressure explosion-proof capacitor;

[0095] S3. After heating the dry overpressure explosion-proof capacitor to 40 - 105 °C, applying an AC voltage V1 to the outgoing line terminal of the dry overpressure explosion-proof capacitor and maintaining it for 5 min - 8 h, and testing the current of the outgoing line terminal and the capacitance of the dry overpressure explosion-proof capacitor. Among them, taking the rated working voltage of the dry overpressure explosion-proof capacitor as V2, V1 and V2 satisfy V1 = 1.3 - 1.5V2;

[0096] S4. Evaluate the explosion-proof performance of the dry-type overpressure explosion-proof capacitor by combining the current of the outgoing terminal, the capacitance of the dry-type overpressure explosion-proof capacitor, the appearance of the dry-type overpressure explosion-proof capacitor, and the fire situation.

[0097] Comparative Example 1

[0098] This comparative example provides a dry-type overpressure explosion-proof capacitor. Compared with Example 1, the difference in composition is that: in the preparation step S4 of the dry-type overpressure explosion-proof capacitor, no mechanical notch or solder joint is formed on the lead wire. Except for the above differences, the materials, formula ratios, and preparation operations used in this comparative example are strictly the same as those in Example 1.

[0099] Comparative Example 2

[0100] This comparative example provides a method for testing the explosion-proof performance of a dry-type overpressure explosion-proof capacitor. Compared with Example 10, the difference in composition is that: no conductor is embedded in the vertical film layer of the electrode core in the dry-type overpressure explosion-proof capacitor, and a DC voltage is used to break down the electrode core. Except for the above differences, the materials, formula ratios, and preparation operations used in this comparative example are strictly the same as those in Example 1.

[0101] Test Example 1

[0102] 1. Test Subjects

[0103] In this test example, the dry-type overpressure explosion-proof capacitors prepared in Examples 1 to 9 and Comparative Example 1 are used as test subjects for relevant performance tests.

[0104] 2. Test Contents

[0105] (1) Gel Strength of Potting Compound

[0106] A round indenter with a diameter of 12.7 mm (without chamfer) is vertically pressed into the potting compound in the dry-type overpressure explosion-proof capacitor by 4 mm, and the maximum force during the pressing process (expressed in g) is recorded. The gel strength of the potting compound is characterized by this test result.

[0107] (2) Pole Case Withstand Voltage Performance

[0108] The pole case insulation test steps are as follows: First, short-circuit the outgoing terminals of the capacitor, and then apply a power frequency AC voltage of 2Un + 2000 between the metal shell and the short-circuited outgoing terminals using an AC withstand voltage tester for 10 s. If there is no breakdown or flashover, it is determined that the pole case withstand voltage is qualified; if there is breakdown or flashover, it is determined that the pole case withstand voltage is poor. Here, Un is the effective voltage of the capacitor.

[0109] (3) Explosion-Proof Performance Test

[0110] Use the explosion-proof performance test method of the dry overpressure explosion-proof capacitor provided in Example 10 to test the explosion-proof performance of the dry overpressure explosion-proof capacitors prepared in Examples 1-9 and Comparative Example 1. If the current between the terminals is 0, or the capacitance is in the pF range, the AC withstand voltage test between the terminal and the outer shell meets the requirements, the outer shell does not explode, the position of the rolling groove is not flattened, the cover plate is not lifted, the electrode core assembly is not thrown out, and there is no fire, it is determined that the explosion-proof test of the dry overpressure explosion-proof capacitor passes (explosion-proof success); otherwise, it fails (explosion-proof failure).

[0111] (4) Durability performance test

[0112] Under the condition of high temperature (75 °C), continuously apply an AC test power supply of 1.35Un to the dry overpressure explosion-proof capacitor for 1000 h, and measure the capacitance and loss tangent value of the dry overpressure explosion-proof capacitor before and after the test to evaluate the durability performance of the dry overpressure explosion-proof capacitor, and calculate the change amount of the capacitance and loss tangent value according to the following formula:

[0113] Change amount of capacitance (%) = (C1 - C0) / C0 × 100%, where C0 represents the capacitance of the dry DC support capacitor before applying the AC test power supply of 1.35Un, and C1 represents the capacitance of the dry DC support capacitor after applying the AC test power supply of 1.35Un;

[0114] Change amount of loss tangent value = tanδ - tanδ0, where tanδ0 represents the loss tangent value of the dry DC support capacitor before applying the AC test power supply of 1.35Un, and tanδ represents the loss tangent value of the dry DC support capacitor after applying the AC test power supply of 1.35Un.

[0115] 3. Experimental results

[0116] Table 4 Gel strength test results of the potting adhesive in the dry overpressure explosion-proof capacitor

[0117]

[0118]

[0119] The gel strength test results of the potting adhesives in the dry overpressure explosion-proof capacitors prepared in Example 1 and Example 6 are shown in Table 4.

[0120] By comparing the gel strength of the potting adhesives in the dry overpressure explosion-proof capacitors provided in Example 1 and Example 6, it can be seen that the components of the gel-state potting material used to form the potting adhesive will affect the gel strength of the potting adhesive in the finally prepared dry overpressure explosion-proof capacitor. The components and their contents in the potting material need to be controlled within a certain range to ensure that the gel strength of the potting adhesive formed after curing meets the requirements of the dry overpressure explosion-proof capacitor. For example, the gel strength of the potting adhesives in the dry overpressure explosion-proof capacitors in experimental groups ⑤, ⑥, and ⑦ of Example 1 and Example 6 is within the range of 400 - 1500 g. The body strength of the potting adhesive is poor, the interfacial adhesion is poor, and gas is easily permeable, which can ensure that the gas generated when the dielectric breaks down the capacitor can quickly penetrate into the explosion-proof reserved space. At the same time, it has the characteristics of no corrosion to the metal coating of the electrode core and no swelling to the dielectric film. There is no oil leakage problem in the potted capacitor, and it can better meet the explosion-proof requirements of the capacitor. If the gel strength of the potting adhesive in the dry overpressure explosion-proof capacitor is too low, such as in experimental groups ②, ④, and ⑧ of Example 6, it is easy for the potting adhesive to show poor curing and be in a flowing state or unable to cure; if the gel strength of the potting adhesive in the dry overpressure explosion-proof capacitor is too high, such as in experimental groups ① and ③ of Example 6, due to the too high strength of the potting adhesive (>2000 g), it will cause the gas generated when the dielectric breaks down the capacitor to be difficult to penetrate into the explosion-proof reserved space, and it cannot meet the explosion-proof requirements of the capacitor.

[0121] Table 5 Test Results of the Pole Shell Voltage Withstanding Performance of Dry Overpressure Explosion-Proof Capacitors

[0122]

[0123]

[0124] The test results of the pole shell voltage withstanding performance of the dry overpressure explosion-proof capacitors prepared in Example 1 and Example 3 are shown in Table 5.

[0125] By comparing the test results of the pole shell voltage withstanding of the dry overpressure explosion-proof capacitors in Example 1 and Example 3, it can be found that compared with experimental groups B - F in Example 3, the material of the lower positioning sleeve of the dry overpressure explosion-proof capacitors in experimental group A of Example 1 and Example 3 is polyimide or mica paper, and there is no breakdown or flashover phenomenon of the metal shell when applying a power frequency alternating voltage of 2Un + 2000 for 10 s between the metal shell and the short-circuited outgoing terminal. Passing the pole shell voltage withstanding test, the above results show that both the lower positioning sleeve and the pole shell in the dry overpressure explosion-proof capacitor adopt high heat-resistant insulating materials such as polyimide or mica paper. When the capacitor fails, it can reduce the risk of the polymer dielectric film in the capacitor melting and decomposing and melting through the lower positioning sleeve and the pole shell, and improve the explosion-proof success rate of the capacitor.

[0126] Table 6 Explosion-proof performance test results of dry overpressure explosion-proof capacitors

[0127]

[0128]

[0129] The explosion-proof performance test results of the dry overpressure explosion-proof capacitors prepared in Examples 1-9 and Comparative Example 1 are shown in Table 6.

[0130] In the dry overpressure explosion-proof capacitor provided by Comparative Example 1, no mechanical notch or solder joint was provided on the lead wire used to connect the electrode core and the outgoing terminal during the preparation process. During the explosion-proof performance test, the cover plate of the capacitor was lifted and the explosion-proof failed. Compared with Comparative Example 1, in the dry overpressure explosion-proof capacitors provided in Examples 1-2 and 7-9, mechanical notches or solder joints were provided on the lead wire used to connect the electrode core and the outgoing terminal as explosion-proof points during the preparation process, and the explosion-proof performance test could be passed. This is mainly because, compared with the entire lead wire, the explosion-proof point is the weak point of mechanical tensile force. Under the action of tensile force, it can be broken preferentially compared with other parts of the lead wire. And due to the existence of the explosion-proof point, the lead wire is easy to be broken even when the mechanical tensile force or the internal expansion degree of the capacitor is relatively low, so as to cut off the external power input and achieve the explosion-proof effect.

[0131] Compared with Experimental Groups B-F of Example 3, the materials of the lower positioning sleeve of the dry overpressure explosion-proof capacitors in Example 1 and Experimental Group A of Example 3 are polyimide or mica paper, and the material of the pole shell is polyimide. The explosion-proof performance test results show that the capacitors in Experimental Groups B-F of Example 3 failed in explosion-proof, while the capacitors in Example 1 and Experimental Group A of Example 3 were successful in explosion-proof and the capacitance was in the pF level. The above results show that high heat-resistant insulating materials such as polyimide or mica paper are used for both the lower positioning sleeve and the pole shell in the dry overpressure explosion-proof capacitor. When the capacitor fails, it can reduce the risk of the polymer dielectric film in the capacitor melting and decomposing and melting through the lower positioning sleeve and the pole shell, and improve the explosion-proof success rate of the capacitor.

[0132] By comparing the explosion-proof performance test results of the dry overpressure explosion-proof capacitors in Example 1 and Example 4, it can be found that in Example 1, by controlling the bottom thickness of the cylindrical outer shell of the capacitor to be above 1.0 mm and the thickness of the circumferential side wall to be above 0.6 mm, the pressure-bearing capacity of the capacitor can be guaranteed, and the air pressure value during the explosion-proof of the capacitor can be covered, so that the capacitor is not easy to crack during the explosion-proof process and the explosion-proof is successful.

[0133] By comparing the explosion-proof performance test results of the dry overpressure explosion-proof capacitors provided in Example 1 and Example 6, it can be seen that the components and their contents of the gel-like potting material used to form the potting compound will affect the explosion-proof performance of the finally prepared dry overpressure explosion-proof capacitors.

[0134] Table 7 Test Results of Capacitance and Dissipation Factor of Dry Overpressure Explosion-Proof Capacitors

[0135]

[0136]

[0137] Note: In the dry overpressure explosion-proof capacitors provided in each example and comparative example, the formulations with poor curing and explosion-proof failure are not subjected to the durability performance test to evaluate their corrosiveness.

[0138] The test results of the capacitance and dissipation factor of the dry overpressure explosion-proof capacitors prepared in Examples 1, 6 to 9 are shown in Table 7.

[0139] By comparing the test results of the capacitance change amount and dissipation factor change amount of Example 1 and Example 6, it can be seen that compared with using other components as the raw materials of the potting compound in the dry overpressure explosion-proof capacitors, using epoxy resin, castor oil, and MDI as the potting material and controlling the mass ratio of the three between 80 - 180:25:6 - 10, the finally prepared dry overpressure explosion-proof capacitors have more excellent durability performance at high temperature, specifically reflected in that the capacitance change amount and dissipation factor change amount of the capacitor can be maintained at a relatively low level before and after continuously applying an AC test power supply of 1.35Un to the capacitor for 1000h.

[0140] The test results of the capacitance change amount and dissipation factor change amount of Examples 1, 7, and 8 can show that by dehydrating the raw materials used to prepare the gel-like potting material and controlling the temperature between 90 - 120°C and the vacuum degree below -0.09MPa, the corrosion risk of the gel-like potting material to the metal coating in the electrode core can be reduced, and the durability performance of the capacitor can be improved, specifically reflected in that the capacitance change amount and dissipation factor change amount of the capacitor can be maintained at a relatively low level before and after continuously applying an AC test power supply of 1.35Un to the capacitor for 1000h.

[0141] By comparing the test results of the capacitance change amount and dissipation factor change amount of Example 1 and Example 9, it can be seen that by evacuating the electrode assembly before potting and controlling the vacuum degree within the range of less than -0.09MPa, the moisture adsorbed inside the electrode assembly can be removed, thereby reducing the risk of attenuation of the capacitance of the finally prepared capacitor and improving the durability performance of the capacitor.

[0142] Test Example 2

[0143] In this test example, the dry overpressure explosion-proof capacitors provided in Examples 1 to 9 were used as the test objects, and the explosion-proof performance of the test objects was tested respectively by using the explosion-proof performance test methods of the dry overpressure explosion-proof capacitors provided in Example 10 and Comparative Example 2. The evaluation criteria for whether the capacitor explosion-proof test passed (explosion-proof success) or failed (explosion-proof failure) referred to Test Example 1. Among them, the test quantity N of the dry overpressure explosion-proof capacitors provided in Examples 1 to 9 was 5 each, that is, 5 parallels were made for each group of experiments, and the quantities of the capacitors with explosion-proof success and explosion-proof failure were recorded.

[0144] Table 8 Comparison of the explosion-proof performance test results of dry overpressure explosion-proof capacitors by using different explosion-proof test methods

[0145]

[0146] The explosion-proof performance of the dry overpressure explosion-proof capacitors provided in Examples 1 to 9 was tested respectively by using the explosion-proof performance test methods of the dry overpressure explosion-proof capacitors provided in Example 10 and Comparative Example 2, and the results are shown in Table 8.

[0147] As can be seen from Table 8, when testing the explosion-proof performance of the dry overpressure explosion-proof capacitors by using the explosion-proof performance test method provided in Comparative Example 2, there was a phenomenon that some of the dry overpressure explosion-proof capacitors that passed the explosion-proof performance test failed in the explosion-proof test when using the explosion-proof performance test method provided in Example 10. The above results can illustrate that there is a problem of inaccurate results in evaluating the explosion-proof performance of the dry overpressure explosion-proof capacitors by using the explosion-proof performance test method provided in Comparative Example 2. Compared with the existing explosion-proof test methods for dry overpressure explosion-proof capacitors, the explosion-proof performance test method of the dry overpressure explosion-proof capacitors provided in Example 10 embeds a conductor in the vertical film layer on the electrode core or uses a DC voltage to break down the electrode core, and artificially creates an electrical weak point at the farthest end of the electrode core, which can well simulate the most severe working conditions that may occur in the actual working conditions of the capacitor, improve the accuracy of the explosion-proof test results, and make the dry overpressure explosion-proof capacitors that pass the explosion-proof performance test provided in Example 10 safer during actual operation.

[0148] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A dry overpressure explosion-proof capacitor, characterized in that: The dry over-pressure explosion-proof capacitor includes an electrode assembly, which includes an electrode core, a lead wire and an outlet terminal. The lead wire is used to connect the electrode core and the outlet terminal. At least one explosion-proof point is provided on the lead wire, and the explosion-proof point includes at least one of a mechanical notch and a welding point.

2. The dry-type overpressure explosion-proof capacitor according to claim 1, characterized in that: The dry over-pressure explosion-proof capacitor further includes an upper positioning sleeve, a lower positioning sleeve, a positioning assembly and an electrode shell, wherein the upper positioning sleeve covers the upper end surface of the electrode assembly, the lower positioning sleeve covers the lower end surface of the electrode assembly, and the positioning assembly is used to fix the electrode assembly; The materials of the upper positioning sleeve, the lower positioning sleeve, the positioning assembly, and the pole shell independently include at least one of polyimide, mica paper, phenolic composite material, epoxy resin composite material, and unsaturated polyester composite material.

3. The dry-type overpressure explosion-proof capacitor according to claim 2, characterized in that: The dry over-pressure explosion-proof capacitor also includes a cylindrical shell, the electrode assembly and the pole shell are fixed in the cylindrical shell, the bottom thickness of the cylindrical shell is greater than 1.0 mm, and the circumferential side wall thickness of the cylindrical shell is greater than 0.6 mm.

4. The dry-type overpressure explosion-proof capacitor according to claim 3, characterized in that: The surface of the cylindrical shell close to the upper positioning sleeve is provided with at least one inward groove, the groove is used to compress the electrode core, and the depth of the groove is above 5 mm.

5. The dry-type overpressure explosion-proof capacitor according to claim 3, characterized in that: A potting compound is filled between the cylindrical shell and the electrode assembly, and the gel strength of the potting compound is 50 to 1500 g.

6. The dry-type overpressure explosion-proof capacitor according to claim 5, characterized in that: The potting glue comprises at least two of epoxy resin, epoxy soybean oil, castor oil, diphenylmethane diisocyanate and methyltetrahydrophthalic anhydride.

7. The dry-type overpressure explosion-proof capacitor according to claim 6, characterized in that: The potting glue further comprises molecular sieve activation powder and nano thermal conductive filler, wherein the nano thermal conductive filler comprises at least one of boron nitride, silicon oxide and aluminum oxide; The molecular sieve activation powder accounts for 0.5-5% by weight in the potting compound, and the nano thermal conductive filler accounts for 0.5-2% by weight in the potting compound.

8. A method for preparing a dry overpressure explosion-proof capacitor, characterized in that: The following steps are involved: S1. Plating a metal layer on one surface of the polymer dielectric film to obtain a metallized film, stacking at least two layers of the metallized film in a staggered manner in the width direction and winding them along a mandrel so that the wound metallized film wraps the mandrel to obtain an electrode core; S2. performing heat setting treatment on the electrode core; S3. The end surface of the electrode core after heat setting treatment is subjected to gold spraying treatment; S4. Connecting the electrode core treated with gold spraying to the outlet terminal using a lead wire, and providing at least one mechanical notch and / or welding point on the lead wire to form an electrode assembly; S5. The electrode assembly is installed in a housing, and a gel potting material is injected into the interior of the housing. The gel potting material is cured to form a potting glue to obtain the dry over-pressure explosion-proof capacitor, wherein: The gel-state potting material comprises at least two of epoxy resin, epoxy soybean oil, castor oil, diphenylmethane diisocyanate and methyltetrahydrophthalic anhydride.

9. The method for preparing a dry overpressure explosion-proof capacitor according to claim 8, characterized in that: The S5 includes the following operations: S5-1. The raw material for preparing the gel potting material is dehydrated at a temperature of 90 to 120 ° C and a vacuum degree of -0.09 MPa or less to a moisture content of less than 150 ppm; S5-2. The raw materials subjected to vacuum dehydration treatment are mixed uniformly to obtain the gel potting material; S5-3. After the electrode assembly is placed in a casing and maintained at a vacuum degree of less than -0.09 MPa for 0.5 to 2 minutes, a gel-like potting material is injected into the interior of the casing to form the potting glue after curing, thereby obtaining the dry-type over-pressure explosion-proof capacitor.

10. The method for testing the explosion-proof performance of a dry-type overpressure explosion-proof capacitor according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. embedding a conductor in a vertical film layer on the electrode core or using a DC voltage to break through the electrode core to obtain a semi-finished product; S2. Assembling the semi-finished product with other components into a dry-type over-pressure explosion-proof capacitor; S3. After heating the dry-type over-pressure explosion-proof capacitor to 40-105°C, apply an AC voltage V1 to the outlet terminal of the dry-type over-pressure explosion-proof capacitor and maintain it for 5min-8h, and test the current of the outlet terminal and the capacity of the dry-type over-pressure explosion-proof capacitor, wherein the rated working voltage of the dry-type over-pressure explosion-proof capacitor is V2, and V1 and V2 satisfy that V1=1.3-1.5V2; S4. Evaluate the explosion-proof performance of the dry-type over-pressure explosion-proof capacitor based on the current of the outlet terminal, the capacity of the dry-type over-pressure explosion-proof capacitor, the appearance of the dry-type over-pressure explosion-proof capacitor and the fire situation.

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