Film snubber film capacitors are widely used in high-frequency filtering, bypass, and first-order or second-order filter circuits. The downstream of home appliances, lighting, industry, photovoltaics, wind power, electric vehicles, etc. From the perspective of specific circuit functions, film snubber film capacitors can generally achieve the following functions:
- filtering, the rectification circuit turns the AC into a pulsating DC, and the filtered pulsating DC voltage becomes a relatively stable DC voltage;
- Reduce noise. Sometimes there will be noise interference outside the system in the current, and the capacitor can be reduced at this time to reduce the interference of noise outside the system;
- Suppress and buffer EMI. During the system’s operation, sudden current and signal interference often occur. The EMI filter can reduce the interference current and signal that suddenly enter the system;
- DC support DC-link is generally required in the scene of AC-DC conversion and plays the role of filtering and energy storage to support the stability of the DC circuit. The unclear antecedent is the film capacitor shaft-weighted；
- The most important application scenarios have important applications in various converters;
Energy storage temporarily stores through the higher and release a higher instantaneous current when the system needs it.
DC support is a scenario where film snubber film capacitors have unique advantages. Since the supporting capacitor needs to have two functions of filtering and energy storage at the same time, secondly, there are higher requirements for the selection of capacitors:
- High capacitance: The primary requirement for a capacitor with an energy storage function is to have a high capacitance value. The larger the capacitance value, the smaller the chance of voltage fluctuation of the DC bus. Under this demand, ceramic snubber film capacitors generally cannot meet the requirements;
- High voltage: In some scenarios, a withstand voltage of thousands of volts is required, and aluminum electrolytic capacitors cannot meet this demand;
- Long life: As mentioned above, film capacitors have self-healing properties and high safety, so film capacitors have a strong advantage in this scenario.
The value of the DC support capacitor is relatively high. Since the voltage and capacitance of DC support capacitors are generally relatively large, the film capacitors used in this scene are generally of high value and quantity. Ordinary capacitors used for filtering, noise prevention, and other functions generally have a unit price of less than 10 yuan. In contrast, The unit price of DC support film snubber film capacitors generally ranges from tens of yuan to hundreds of yuan.
In addition, film snubber film capacitors can also be used as snubber capacitors to protect circuit systems. When high-frequency noise occurs in the circuit, the film capacitor can also suppress and remove the noise so that the new energy vehicle will not be disturbed by high-frequency noise.
Film capacitor production process:
1. Film cutting: Cut the metal foil into the required design width with a film cutting machine according to the designed capacity of the product. It is required that there are no burrs when cutting and the appearance is free from dirt and wrinkles.
2. Winding: According to the requirements of the process, select the needle core and metal lim and wind it into a core with a winding machine. It is required that the capacity of the film capacitor meets the design requirements, the end face of the core is flat, the burnt film is clean, the tension is moderate, and the film cannot be scratched.
3. Hot pressing: According to the requirements of the process, select the appropriate hot pressing parameters (pressure, temperature, time) on the hot pressing machine to flatten the core into shape. It is required that the core cannot be loosened when a slight external force is applied, and the film cannot be delaminated.
4. Braiding: According to the requirements of the process, select the appropriate adhesive tape and weave the core into a roll. The adhesive tape is required to have good adhesion, and the adhesive tape cannot cover the end face of the core.
5. Gold spraying: Spray a metal layer on the two end faces of the core. According to the requirements of the process, select the spraying distance, air pressure, and wire speed. It is required that the thickness and adhesion of sprayed gold meet the requirements.
6. Hemming: Disassemble the braid after gold spraying, and use a roller machine to remove the residual edge after gold spraying and the excess metal dust adhered to the surface of the core. Hemming time and speed refer to process requirements. It is required that there is no redundant metal edge on the end face of the core and no metal dust on the surface.
7. Vacuum drying: Depending on the product requirements, the drying oven selects a qualified temperature, pressure, and time to improve the electrical properties of film capacitor products. It is required to ensure the accuracy of the parameters the machine sets.
8. Empowerment: According to the characteristics of film capacitor products, select the appropriate incremental voltage to improve the electrical performance of high film capacitor products. The voltage setting is required to be accurate.
9. Soldering: Solder the pins on the core. It is required that the wire diameter and length are correct, the position is appropriate, the welding current is correct, the metal film cannot be scalded, the solder joints are smooth, there are no burrs, and there is no false welding.
10. Plug-in: Insert the core into the plastic shell. The core is required to be in the middle of the shell and fixed
11. Potting: Potting the potting material into the plastic shell. It is required that the proportion of the potting material is correct, the stirring is uniform, there should be no resin on the lead-out end and the shell surface, and no bubbles on the grease surface. The size is accurate
indeed.
12. Printing: Print relevant information on the surface of the material. It is required that the label of the film capacitor is correct; the silk screen is clear, centered, and not easy to fall off.
13. Shipment inspection: performance random inspection (capacity, loss, withstand voltage, insulation resistance). The appearance of the plastic shell should be smooth, without scratches, burrs, resin, and other bad phenomena.
With the development of new energy vehicles, the demand for film snubber film capacitors is also increasing. When purchasing film capacitors, pay attention to the quality and quality of film capacitors. In summary, film capacitors under different scenarios can exhibit different functional characteristics, so they are widely used in various downstream fields. Among them, under the demand scenario of DC support other types of capacitors do not have so that they can be widely used in industries, wind power, photovoltaics, energy storage, electric vehicles, and other fields. The above fields are currently in a good stage of industry development, so under the stimulation of these fields, the market space for film capacitors is gradually opening up.
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