Custom DC Filter Capacitor Manufacturers

How are vacuum drying and impregnation processes carried out during the manufacturing process of DC filter capacitors? What are the important effects of the impregnation process on the performance and life of capacitors?

Vacuum drying process
Preparation: Before vacuum drying, the components of the DC filter capacitor need to be pre-treated, including cleaning and inspecting the metallized film (such as polypropylene, polyester, etc.) to ensure that there are no impurities and damage on its surface. At the same time, prepare the vacuum drying equipment and check whether the sealing and various parameters of the equipment are normal.
Place in the drying chamber: Place the pre-treated capacitor components in the vacuum drying chamber, and pay attention to the placement method that is conducive to heat transfer and moisture dissipation. Generally, the components are placed in layers, leaving enough space for hot air to circulate.
Vacuuming: Start the vacuum pump and gradually reduce the pressure in the drying chamber to form a vacuum environment. During the vacuuming process, pay close attention to the changes in pressure to ensure that the vacuum degree meets the specified requirements. Usually, the vacuum degree should reach a few Pascals or even lower to effectively remove moisture and air from the components.
Heating and drying: Heat the drying chamber in a vacuum environment. The heating method can be electric heating, thermal radiation, etc., so that the capacitor components are evenly heated. The heating temperature is generally controlled at around 80-120℃, and the specific temperature depends on the material and structure of the capacitor. During the heating process, moisture will evaporate from the component and be pumped out of the drying chamber by the vacuum pump.
Drying time control: Drying time is a key parameter, which depends on the size of the capacitor, the water content of the component, and the requirements of the drying process. Generally speaking, the drying time of small capacitors may range from a few hours to more than ten hours, while large capacitors may take dozens of hours or even longer. During the drying process, it is necessary to regularly test the water content of the component. When the water content reaches below the specified standard, it can be considered that the drying is complete.
Cooling and removal: After drying is completed, stop heating and let the capacitor component cool naturally to room temperature in a vacuum environment. After cooling, slowly release the vacuum, take out the dried component, and prepare for the next impregnation process.

Impregnation process
Impregnation liquid preparation: For DC filter capacitors, the commonly used impregnation liquid is environmentally friendly insulating oil such as rapeseed oil. Before use, the rapeseed oil needs to be filtered, dehydrated, etc. to ensure that its purity and performance meet the requirements. At the same time, some additives such as antioxidants and anti-aging agents can be added as needed to improve the performance and life of the capacitor.
Component impregnation: Put the dried capacitor element into the impregnation tank, and then slowly pour the treated impregnation liquid into the impregnation tank so that the element is completely immersed in the impregnation liquid. During the impregnation process, stirring, ultrasonic waves and other methods can be used to promote the impregnation liquid to fully penetrate into various parts of the element, especially the gaps between the metallized films and the contact between the electrode and the film.
Vacuum impregnation: In order to improve the impregnation effect, vacuum impregnation is usually used. After the element is immersed in the impregnation liquid, the impregnation tank is vacuumed to further reduce the pressure in the tank. Under vacuum conditions, the impregnation liquid can better penetrate into the tiny pores of the element, remove the air and impurities therein, and improve the uniformity and density of the impregnation.
Impregnation time and temperature control: Impregnation time and temperature are also important process parameters. Generally speaking, the impregnation temperature is around 40-60℃, and the impregnation time depends on the type and size of the capacitor, which may be between several hours and tens of hours. Properly increasing the temperature can reduce the viscosity of the impregnation liquid and facilitate its penetration, but too high a temperature may cause the performance of the impregnation liquid to change, so the temperature range needs to be strictly controlled.
Post-impregnation treatment: After the impregnation is completed, remove the capacitor element from the impregnation tank and drain the excess impregnation liquid. Then clean the surface of the element to remove impurities and impregnation liquid residues that may be attached to the surface. For some capacitors with higher requirements, it may also be necessary to cure the impregnated element to further improve its performance and stability.

The impact of the impregnation process on the performance and life of the capacitor
Improve electrical performance: Through the impregnation process, the insulating oil can fill the gaps between the metallized films, reduce the presence of air gaps and impurities, thereby improving the insulation performance of the capacitor and reducing dielectric loss. At the same time, good impregnation can make the electric field distribution more uniform, reduce the local electric field concentration phenomenon, improve the withstand voltage of the capacitor, enable it to withstand higher operating voltages, and protect the network from instantaneous voltage spikes and surges.
Enhance heat dissipation performance: DC filter capacitors will generate a certain amount of heat during operation. The presence of the impregnation liquid can effectively transfer the heat from the inside of the element to the shell, improving the heat dissipation effect. Insulating oils such as rapeseed oil have good thermal conductivity and can quickly dissipate heat, reducing the operating temperature of the capacitor, thereby reducing the performance degradation and shortened life caused by high temperature and extending the service life of the capacitor.
Improve self-healing performance: Metallized film capacitors have self-healing properties. When local defects on the film cause breakdown, the surrounding metallized layer will evaporate at high temperature to form an insulating area, allowing the capacitor to continue to work normally. The impregnation liquid can play a role in cooling and isolation during the self-healing process, preventing the expansion of the fault point, improving the self-healing ability of the capacitor, and thus enhancing its reliability and stability.
Prevent aging and corrosion: The additives in the impregnation liquid can form a protective film on the surface of the capacitor element to prevent the metallized film and electrodes from being oxidized and corroded. At the same time, the insulating oil can prevent the intrusion of external moisture and impurities, reduce the performance degradation and shortened life caused by moisture and pollution, and maintain the long-term stability of the capacitor performance.
Improve vibration and impact resistance: Jiande Antai Power Capacitor Co., Ltd.'s DC filter capacitors are made of aluminum casing, with a side plate thickness of 2 mm, a cover plate and a base thickness of 3 mm, and through a good impregnation process, the components and the casing form a whole, which enhances the structural strength of the capacitor. During the impregnation process, the insulating oil fills the gap between the component and the casing, which plays a role in buffering and shock absorption, allowing the capacitor to withstand harsh working conditions and have good vibration and impact resistance.

In the manufacturing process of DC filter capacitors, vacuum drying and impregnation processes are very critical links. As a professional manufacturer with 40 years of experience, Jiande Antai Power Capacitor Co., Ltd. has rich experience and strict quality control in these processes, ensuring that the DC filter capacitors it produces are ISO9001 and CE certified, and have won wide recognition and trust from domestic and foreign customers with excellent performance and reliable quality. By optimizing the vacuum drying and impregnation process, the performance and life of the capacitor can be effectively improved to meet the high requirements for DC filter capacitors in different application scenarios.