Capacitor impregnation process

Abstract

The invention relates to the technical field of capacitor manufacturing, in particular to a capacitor impregnation process, which comprises a heating and tossing stage, a primary vacuumizing stage, a cooling stage, a secondary vacuumizing stage, an oil injection stage and an impregnation stage, the interior of the impregnation tank body is heated to a first set temperature, meanwhile, pre-vacuumizing treatment and gas injection treatment are sequentially conducted on the interior of the impregnation tank body, and the pre-vacuumizing treatment and the gas injection treatment are circularly conducted. According to the invention, the air pressure and temperature of the impregnation tank body are dynamically regulated and controlled in stages before oil injection and impregnation, so that residual air molecules and water molecules among capacitor elements are maximally removed, and the impregnation effect of the capacitor is improved.

Description

Technical Field

[0001] This invention relates to the field of capacitor manufacturing technology, and more specifically to a capacitor impregnation process. Background Technology

[0002] All-film capacitors are a type of capacitor where the insulating medium between the plates is entirely thin film. Vacuum drying and impregnation is one of the most critical processes in the production of all-film capacitors, significantly impacting their quality and lifespan. Vacuum impregnation involves removing moisture and gases from the capacitor's internal components under vacuum, followed by the injection of purified and inspected liquid insulating oil into the capacitor under pressure. The impregnating oil fills the spaces between the capacitor elements, serving as both an auxiliary dielectric and providing insulation and thermal conductivity.

[0003] Currently, controlling the moisture and oxygen levels within the impregnation container is a critical issue during the impregnation process. Residual impregnating agent with water seals can easily remain at the bottom of the container. This moisture can seep into the capacitor's plates or between the internal plates during impregnation, causing oxidation and potentially leading to breakdown during subsequent use. Therefore, improving the impregnation effect is an urgent problem to be solved in capacitor manufacturing. Summary of the Invention

[0004] The technical problem solved by this invention is how to improve the impregnation effect of capacitors.

[0005] To address the above problems, the present invention provides a capacitor impregnation process, comprising: Heating and gas ballasting stage: After placing the capacitor in the impregnation tank, the inside of the impregnation tank is heated to the first set temperature. At the same time, the inside of the impregnation tank is subjected to pre-vacuuming and gas injection treatment in sequence, and the pre-vacuuming and gas injection treatment are cyclically performed. First vacuuming stage: The inside of the impregnation tank is evacuated once; Cooling stage: The inside of the impregnation tank is cooled to a second set temperature, and at the same time, inert gas is injected into the impregnation tank to keep the gas pressure inside the impregnation tank stable at a first gas pressure value. Secondary vacuuming stage: A secondary vacuum is performed inside the impregnation tank to keep the air pressure inside the impregnation tank stable at the second air pressure value; Oiling stage and immersion stage.

[0006] Optionally, the pre-vacuuming process includes: pre-vacuuming the inside of the impregnation tank until the pressure drops to 3 to 5 kPa; the gas injection process includes: injecting inert gas into the impregnation tank until the pressure reaches 80 to 85 kPa, and maintaining this pressure for 10 to 15 minutes.

[0007] Optionally, the first set temperature in the heating gas ballast stage is 80 to 84°C.

[0008] Optionally, the duration of the heating and ballast stage is 6 to 8 hours.

[0009] Optionally, the step of performing a vacuum evacuation inside the impregnation tank includes: sequentially and stably maintaining the vacuum level inside the impregnation tank at a third pressure value and a fourth pressure value, and maintaining the temperature inside the impregnation tank at the first set temperature; wherein the third pressure value is greater than the fourth pressure value.

[0010] Optionally, the third pressure value ranges from 0.8 to 1 kPa, and the fourth pressure value ranges from 5 to 7 Pa.

[0011] Optionally, the third pressure value is maintained for 1 to 3 hours, and the fourth pressure value is maintained for 35 to 40 hours.

[0012] Optionally, during the cooling stage, the second set temperature ranges from 55 to 60°C, and the first air pressure value ranges from 70 to 75 kPa.

[0013] Optionally, the temperature range of the secondary vacuuming stage is 45 to 50°C, the range of the second gas pressure value is 1 to 3 Pa, and the duration of the secondary vacuuming stage is 15 to 20 hours.

[0014] Optionally, the temperature of the impregnation stage shall not exceed 50°C, the vacuum degree shall not exceed 5Pa, and the impregnation time shall not be less than 25h.

[0015] The advantages of this invention compared to related technologies include: This invention first uses a heating and ballasting stage to rapidly vaporize the water and residual oil inside the impregnation tank. Under the cyclical pre-vacuuming and gas injection processes, the vaporized components are expelled along with the injected gas during each pre-vacuuming process. Then, a first vacuuming stage further removes residual water vapor from the impregnation tank, causing the capacitor film to expand in the thickness direction, reducing the gap between the plates, and thus promoting the initial expulsion of air from the capacitor cavity, keeping the tank dry and relatively clean. Subsequently, in the cooling stage, inert gas is injected into the impregnation tank to carry heat out of the tank through its flow. During this process, the expanded state of the capacitor film gradually disappears and returns to its original state. Finally, a second vacuuming stage maximizes the removal of gas from the capacitor cavity. Therefore, this invention, by dynamically controlling the gas pressure and temperature inside the impregnation tank in stages before oil impregnation, maximizes the removal of residual air and water molecules between capacitor elements, improving the impregnation effect and capacitor product performance. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of the capacitor impregnation process in an exemplary embodiment of the present invention. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0018] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit this application. The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] Taking a fully film oil-filled capacitor as an example, its manufacturing process typically includes steps such as component winding, core assembly and packaging, welding, vacuum impregnation, and hot-baking for leak testing. In the vacuum impregnation process, the casing of the fully film oil-filled capacitor is filled with impregnating oil, typically benzyltoluene, silicone oil, or high-purity rapeseed oil. The oil serves as both an auxiliary dielectric and provides insulation and thermal conductivity. After the capacitor oil is injected into the capacitor under vacuum, it is pressurized to fill the spaces between the capacitor elements.

[0020] During the impregnation process, controlling the moisture and oxygen levels within the impregnation container is crucial, significantly impacting the capacitor's performance and lifespan. Due to the large size of power capacitors, the impregnation tanks used are also relatively large. This can lead to residual impregnating agent with water seals at the bottom of the tank. This moisture can seep into the capacitor's plates or internal plates during impregnation, causing oxidation. Furthermore, all-film capacitors use polypropylene film as the main dielectric. Polypropylene exhibits different shrinkage and expansion capabilities at different temperatures, making temperature control during impregnation extremely important. Additionally, minimizing air removal between the plates and the main dielectric during impregnation is another key factor affecting capacitor performance.

[0021] To address the above problems, embodiments of the present invention provide a capacitor impregnation process, comprising the following stages: Heating and gas ballasting stage: After placing the capacitor in the impregnation tank, the inside of the impregnation tank is heated to the first set temperature. At the same time, the inside of the impregnation tank is subjected to pre-vacuuming and gas injection treatment in sequence, and the pre-vacuuming and gas injection treatment are repeated cyclically. First vacuuming stage: The inside of the impregnation tank is evacuated once; Cooling stage: Cool the inside of the impregnation tank to the second set temperature, and at the same time inject inert gas into the impregnation tank to keep the gas pressure inside the impregnation tank stable at the first gas pressure value. Secondary vacuuming stage: A secondary vacuum is performed inside the impregnation tank to ensure that the air pressure inside the impregnation tank is stably maintained at the second air pressure value. Oiling stage and immersion stage.

[0022] In the capacitor impregnation process of this invention, a heating and gas ballast stage is first used to rapidly vaporize the water and residual oil inside the impregnation tank. Then, under the cyclical pre-vacuuming and gas injection processes, the vaporized components are discharged along with the injected gas during each pre-vacuuming process. Next, a first vacuuming stage further removes residual water vapor from the impregnation tank and causes the capacitor film to expand in the thickness direction, reducing the gap between the plates and promoting the initial removal of air from the capacitor cavity, keeping the tank dry and relatively clean. Subsequently, in the cooling stage, inert gas is injected into the impregnation tank to carry heat out of the tank through its flow. During this process, the expanded state of the capacitor film gradually disappears and returns to its original state. Finally, a second vacuuming stage maximizes the removal of gas from the capacitor cavity. Therefore, this invention, by dynamically controlling the gas pressure and temperature inside the impregnation tank in stages before oil impregnation, maximizes the removal of residual air and water molecules between capacitor elements, thus improving the performance of the capacitor product.

[0023] In some optional embodiments, the first set temperature in the heating and gas ballast stage is 80 to 84°C. While heating to maintain the first set temperature inside the impregnation tank, the impregnation tank is cyclically subjected to pre-vacuuming and gas injection. Specifically, the pre-vacuuming includes: pre-vacuuming the impregnation tank until the pressure drops to 3 to 5 kPa; the gas injection includes: injecting inert gas into the impregnation tank until the pressure reaches 80 to 85 kPa. It should be understood that one gas ballast cycle includes one pre-vacuuming and one gas injection. When heating begins, the impregnation tank is first pre-vacuumed until the pressure inside the tank drops to 3 to 5 kPa. Then, the inlet valve is opened, and inert gas is injected into the impregnation tank until the pressure reaches 80 to 85 kPa. This pressure is maintained for 10 to 15 minutes before the next gas ballast cycle begins, until the heating and gas ballast stage ends. Optionally, the duration of the heating and gas ballast stage can be 6 to 8 hours.

[0024] During the heating and gas ballast stage, heating and gas ballasting are carried out simultaneously. The residual liquid inside the impregnation tank is heated and vaporized, while the inert gas introduced into the impregnation tank during gas ballasting further accelerates the vaporization of the residual liquid. Then, a pre-vacuuming process is used to remove it from the impregnation tank. Therefore, under the control of heating and gas pressure in this stage, most of the liquid water can be converted into gas and discharged from the impregnation tank.

[0025] In some optional embodiments, the vacuuming stage further includes: sequentially and stably maintaining the vacuum level inside the impregnation tank at a third pressure value and a fourth pressure value, wherein the third pressure value is greater than the fourth pressure value. Specifically, the third pressure value ranges from 0.8 to 1 kPa, and the fourth pressure value ranges from 5 to 7 Pa; the third pressure value is maintained for 1 to 3 hours, and the fourth pressure value is maintained for 35 to 40 hours.

[0026] It should be noted that during the first vacuuming stage, the temperature inside the impregnation tank is maintained at the first set temperature, namely 80 to 84°C, which can be dynamically controlled by the heating device.

[0027] In this embodiment, the vacuuming stage can be further divided into a low-vacuum stage and a high-vacuum stage. In the low-vacuum stage, the pressure inside the impregnation tank is maintained at a third atmospheric pressure value. The main purpose is to expel air from the capacitor cavity and further remove residual moisture from the impregnation tank, while simultaneously maintaining the capacitor core temperature at 80 to 84°C. This allows the thin film to expand in the thickness direction, reducing the gap between the plates and allowing air to escape, thus keeping the impregnation tank dry and relatively clean. In the high-vacuum stage, the pressure inside the impregnation tank is further reduced to a fourth atmospheric pressure value, maximizing the removal of moisture between the component plates. During this stage, the thin film continues to expand, compressing the air between the plates. Moisture and air are discharged through the vent valve. Additionally, moisture in the insulating components is also fully removed.

[0028] In this embodiment, the vacuuming stage is divided into two vacuum gradients, with each vacuum level maintained for a certain period of time. The low vacuum stage corresponds to viscous flow, suitable for rapidly removing large amounts of air; the high vacuum stage corresponds to molecular flow, capable of handling gas within micropores. This staged vacuuming process is both efficient and thorough, significantly shortening the overall vacuuming time and facilitating the complete removal of residual gas and adsorbed water vapor.

[0029] In some alternative embodiments, during the cooling phase, the second set temperature ranges from 55 to 60°C, and the first pressure value ranges from 70 to 75 kPa.

[0030] In this embodiment, the impregnation tank stops heating during the cooling phase and is filled with inert gas as a heat transfer medium to break up the vacuum. Simultaneously, a circulating fan inside the impregnation tank is activated, allowing the inert gas to circulate within the tank and conduct heat to the internal heating oil pipes. The heating oil pipes are then cooled by external water cooling, thus removing the heat from the tank. During the cooling phase, the expanded state of the main medium, the polypropylene film, gradually disappears and returns to its original state. This embodiment accelerates the cooling rate within the tank by injecting inert gas, avoiding excessively long cooling times under vacuum conditions that could affect the overall impregnation efficiency.

[0031] In some optional embodiments, the temperature range of the secondary vacuuming stage is 45 to 50°C, the second pressure value ranges from 1 to 3 Pa, and the duration of the secondary vacuuming stage is 15 to 20 hours.

[0032] In this embodiment, after controlling the temperature and pressure inside the impregnation tank to the set values ​​during the cooling stage, gaps will reappear between the plates after the capacitor film returns to its original state, generating a small amount of air that has not been expelled. Performing a second vacuum at this point will allow this portion of gas to be expelled to the greatest extent possible. Furthermore, maintaining the temperature at 45 to 50°C during the second vacuum stage ensures that the capacitor film will not expand again during this stage, facilitating the smooth progress of the oil filling stage.

[0033] In some optional embodiments, the temperature during the oil injection stage does not exceed 50°C, the vacuum degree does not exceed 7Pa, and the oil injection time is not less than 12h; the temperature during the impregnation stage does not exceed 50°C, the vacuum degree does not exceed 5Pa, and the impregnation time is not less than 25h.

[0034] By controlling the oil injection time, sufficient time is given for residual gas to be removed by the vacuum pump, ensuring a smooth oil rise and complete filling of all spaces. This also helps avoid impacting the capacitor core and generating air bubbles. Controlling the impregnation time ensures deep penetration of the impregnating oil into the capacitor core, fully entering the space between the plates and the dielectric, and completely eliminating microscopic air bubbles. After impregnation, the air inlet valve is opened for venting, allowing the impregnation tank to cool to room temperature before the capacitor is removed from the tank.

[0035] It should be noted that the inert gas used in the embodiments of the present invention can be selected from any one of nitrogen, helium, neon and argon, and is preferably nitrogen.

[0036] The present invention will be described in detail below through specific embodiments: Example 1 In this embodiment, the capacitor impregnation process includes the following steps: Heating and ballasting stage: Place the capacitor in the impregnation tank and turn on the heater to maintain the temperature inside the impregnation tank between 80 and 84°C. During this process, turn on the vacuum pump to pre-evacuate the impregnation tank until the gas pressure inside the impregnation tank drops to 5 kPa. Turn off the vacuum pump and open the nitrogen inlet valve to inject nitrogen until the gas pressure inside the tank reaches 85 kPa. Maintain this for 15 minutes, and then repeat the pre-evacuation and gas injection cycle until the heating and ballasting stage ends. The heating and ballasting stage lasts for 7 hours.

[0037] First vacuuming stage: Turn on the vacuum pump and maintain the temperature inside the impregnation tank between 80 and 84°C. Then, first evacuate until the internal pressure of the impregnation tank drops to 1 kPa, and then maintain this pressure for 2 hours. Then, evacuate again until the internal pressure of the impregnation tank drops to 7 Pa, and maintain this pressure for 40 hours.

[0038] Cooling stage: Stop heating the impregnation tank and open the nitrogen inlet valve and the built-in fan of the impregnation tank to reduce the temperature to 60°C and increase the gas pressure inside the tank to 75 kPa.

[0039] Secondary vacuuming stage: Reduce the internal temperature of the impregnation tank to 50°C, turn on the vacuum pump, reduce the air pressure inside the impregnation tank to 3Pa, and maintain this air pressure for 1000min.

[0040] Oil injection stage: Open the oil injection pipe to inject oil, control the oil injection temperature to not exceed 50℃, the vacuum degree to not exceed 7Pa, and the oil injection time to not be less than 12h.

[0041] Impregnation stage: The impregnation temperature shall not exceed 50℃, the vacuum degree shall not exceed 5Pa, and the impregnation time shall not be less than 25h.

[0042] After impregnation, the capacitors are cooled to room temperature and then removed from the container.

[0043] The impregnation process described in this embodiment was used to impregnate a batch of six capacitors. The relevant performance indicators of each capacitor after impregnation are shown in Table 1. Table 1. Performance indicators of a single batch of capacitors after impregnation in Example 1

[0044] It is evident that capacitors from the same batch of impregnation treatment exhibit characteristics such as small fluctuations in finished product weight, high consistency in capacitance, low loss rate, and high withstand voltage.

[0045] Example 2 In this embodiment, the capacitor impregnation process includes the following steps: Heating and ballasting stage: Place the capacitor in the impregnation tank and turn on the heater to maintain the temperature inside the impregnation tank between 80 and 84°C. During this process, turn on the vacuum pump to pre-evacuate the impregnation tank until the gas pressure inside the impregnation tank drops to 4 kPa. Turn off the vacuum pump and open the nitrogen inlet valve to inject nitrogen until the gas pressure inside the tank reaches 83 kPa. Maintain this for 15 minutes, and then repeat the pre-evacuation and gas injection cycle until the heating and ballasting stage ends. The heating and ballasting stage lasts for 8 hours.

[0046] First vacuuming stage: Turn on the vacuum pump and maintain the temperature inside the impregnation tank between 80 and 84°C. Then, first evacuate until the internal pressure of the impregnation tank drops to 0.8 kPa, and then maintain this pressure for 3 hours. Then, evacuate again until the internal pressure of the impregnation tank drops to 5 Pa, and maintain this pressure for 35 hours.

[0047] Cooling stage: Stop heating the impregnation tank and open the nitrogen inlet valve and the built-in fan of the impregnation tank to reduce the temperature to 58°C and increase the gas pressure inside the tank to 73 kPa.

[0048] Secondary vacuuming stage: Reduce the internal temperature of the impregnation tank to 48°C, turn on the vacuum pump, reduce the gas pressure inside the impregnation tank to 2Pa, and maintain this pressure for 20 hours.

[0049] Oil injection stage: Open the oil injection pipe to inject oil into the immersion tank, control the oil injection temperature to not exceed 50℃, the vacuum degree to not exceed 7Pa, and the oil injection time to not be less than 12h.

[0050] Impregnation stage: The impregnation temperature shall not exceed 50℃, the vacuum degree shall not exceed 5Pa, and the impregnation time shall not be less than 25h.

[0051] After impregnation, the capacitors are cooled to room temperature and then removed from the container.

[0052] Similarly, the impregnation process in this embodiment was used to impregnate a batch of 6 capacitors, and the relevant performance indicators of each capacitor after impregnation are shown in Table 2: Table 2 Performance indicators of a single batch of capacitors after impregnation in Example 2

[0053] Example 3 In this embodiment, the capacitor impregnation process includes the following steps: Heating and ballasting stage: Place the capacitor in the impregnation tank and turn on the heater to maintain the temperature inside the impregnation tank between 80 and 84°C. During this process, turn on the vacuum pump to pre-evacuate the impregnation tank until the gas pressure inside the impregnation tank drops to 3 kPa. Then, turn off the vacuum pump and open the nitrogen inlet valve to inject nitrogen until the gas pressure inside the tank reaches 80 kPa. Repeat the pre-evacuation and gas injection cycle until the heating and ballasting stage ends. The heating and ballasting stage lasts for 8 hours.

[0054] First vacuuming stage: Turn on the vacuum pump and maintain the temperature inside the impregnation tank between 80 and 84°C. Then, first evacuate until the internal pressure of the impregnation tank drops to 0.8 kPa, and then maintain this pressure for 1 hour. Then, evacuate again until the internal pressure of the impregnation tank drops to 5 Pa, and maintain this pressure for 38 hours.

[0055] Cooling stage: Stop heating the impregnation tank and open the nitrogen inlet valve and the built-in fan of the impregnation tank to reduce the temperature to 55°C and increase the gas pressure inside the tank to 70 kPa.

[0056] Secondary vacuuming stage: Reduce the internal temperature of the impregnation tank to 45°C, turn on the vacuum pump, reduce the gas pressure inside the impregnation tank to 1Pa, and maintain this pressure for 15 hours.

[0057] Oil injection stage: Open the oil injection pipe to inject oil, control the oil injection temperature to not exceed 50℃, the vacuum degree to not exceed 7Pa, and the oil injection time to not be less than 12h.

[0058] Impregnation stage: The impregnation temperature shall not exceed 50℃, the vacuum degree shall not exceed 5Pa, and the impregnation time shall not be less than 25h.

[0059] After impregnation, the capacitors are cooled to room temperature and then removed from the container.

[0060] The impregnation process described in this embodiment was used to impregnate a batch of six capacitors. The relevant performance indicators of each capacitor after impregnation are shown in Table 3. Table 3 Performance indicators of single batch capacitors after impregnation in Example 3

[0061] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A capacitor impregnation process, characterized in that, include: Heating and gas ballasting stage: After placing the capacitor in the impregnation tank, the inside of the impregnation tank is heated to the first set temperature. At the same time, the inside of the impregnation tank is subjected to pre-vacuuming and gas injection treatment in sequence, and the pre-vacuuming and gas injection treatment are cyclically performed. First vacuuming stage: The inside of the impregnation tank is evacuated once; Cooling stage: The inside of the impregnation tank is cooled to a second set temperature, and at the same time, inert gas is injected into the impregnation tank to keep the gas pressure inside the impregnation tank stable at a first gas pressure value. Secondary vacuuming stage: A secondary vacuum is performed inside the impregnation tank to keep the air pressure inside the impregnation tank stable at the second air pressure value; Oiling stage and immersion stage.

2. The capacitor impregnation process according to claim 1, characterized in that, The pre-vacuuming process includes: pre-vacuuming the inside of the impregnation tank until the pressure drops to 3 to 5 kPa; the gas injection process includes: injecting inert gas into the impregnation tank until the pressure reaches 80 to 85 kPa, and maintaining this pressure for 10 to 15 minutes.

3. The capacitor impregnation process according to claim 1, characterized in that, The first set temperature in the heating and ballast stage is 80 to 84°C.

4. The capacitor impregnation process according to claim 1, characterized in that, The heating and ballast stage is maintained for 6 to 8 hours.

5. The capacitor impregnation process according to claim 1, characterized in that, The step of performing a vacuum evacuation inside the impregnation tank includes: maintaining the vacuum level inside the impregnation tank at a third pressure value and a fourth pressure value in sequence, and maintaining the temperature inside the impregnation tank at the first set temperature; wherein the third pressure value is greater than the fourth pressure value.

6. The capacitor impregnation process according to claim 5, characterized in that, The third pressure value ranges from 0.8 to 1 kPa, and the fourth pressure value ranges from 5 to 7 Pa.

7. The capacitor impregnation process according to claim 6, characterized in that, The third air pressure value is maintained for 1 to 3 hours, and the fourth air pressure value is maintained for 35 to 40 hours.

8. The capacitor impregnation process according to claim 1, characterized in that, During the cooling phase, the second set temperature ranges from 55 to 60°C, and the first air pressure ranges from 70 to 75 kPa.

9. The capacitor impregnation process according to claim 1, characterized in that, The temperature range of the secondary vacuuming stage is 45 to 50°C, the second pressure value ranges from 1 to 3 Pa, and the duration of the secondary vacuuming stage is 15 to 20 hours.

10. The capacitor impregnation process according to claim 1, characterized in that, The temperature during the impregnation stage shall not exceed 50°C, the vacuum degree shall not exceed 5Pa, and the impregnation time shall not be less than 25 hours.

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