Three-level film capacitor

Abstract

The utility model relates to the technical field of thin-film capacitors, in particular to a three-level thin-film capacitor, which not only can meet the requirement of high capacity required by a high-power inverter, but also can reduce the occupied space in an inverter module and is convenient to install, and comprises a capacitor shell and a capacitor core, the capacitor core comprises three core groups which are arranged in the same capacitor shell, each core group is composed of two groups of cores which are connected in parallel, two ends of each core group are fixedly connected with welding copper plates, the welding copper plates are connected with busbars provided with electrode through holes, extraction electrodes penetrate through the electrode through holes, and the extraction electrodes are connected with the busbars. The core is a flat core formed by winding a metalized film.

Description

Technical Field

[0001] This utility model relates to the field of thin film capacitor technology, specifically a three-level thin film capacitor. Background Technology

[0002] Metallized film capacitors (FSCs) are characterized by high voltage resistance, high ripple current withstand capability, and low ESR and ESL. They are essential for energy storage and ripple voltage suppression in the DC link of energy inverters to ensure normal operation. However, with the advent of high-voltage, high-current IGBT devices, three-level inverters have become a development trend for high-voltage, high-power inverters. Typically, FSCs have small capacitance, requiring multiple sets of FSCs to be connected in parallel within the inverter module, which presents an inconvenience for installation and use. Summary of the Invention

[0003] To solve the above-mentioned technical problems, this utility model provides a three-level thin-film capacitor that can meet the large capacity requirements of high-power inverters, reduce space occupation in inverter modules, and facilitate installation.

[0004] The technical solution is as follows: a three-level film capacitor, comprising a capacitor shell and a capacitor core, characterized in that the capacitor core comprises three core groups installed in the same capacitor shell, each core group consisting of two sets of cores connected in parallel and having two ends fixedly connected to a welded copper plate, the welded copper plate being connected to a busbar with electrode through holes, the electrode through holes having lead-out electrodes passing through them, and the core being a flat core formed by winding a metallized film.

[0005] A further feature is that the capacitor shell is an aluminum shell, and the inner wall of the aluminum shell is roughened and reinforced with intermittent reinforcing ribs;

[0006] An insulating encapsulation cover is provided on the potting surface;

[0007] The encapsulation insulating cover plate is provided with an injection port and a boss;

[0008] The welding copper plate has through holes for adhesive material;

[0009] The metallized film is provided with a half-T two-section safety membrane structure.

[0010] The width of the transparent white stripes on both sides of the metallized film is reduced to 0.2 mm.

[0011] By adopting this utility model, three core groups are integrated into one capacitor housing, replacing the structure of multiple three-level film capacitors connected in parallel. This reduces space occupancy, makes installation and use more convenient, and adopts a flat core structure, which has higher energy density and occupies relatively less space compared to a round core, making the internal space more compact, reducing volume and saving space. Each core group consists of two sets of cores connected in parallel, narrowing the film width and increasing the overcurrent capacity. Overall, it better meets the large capacity requirements of high-power inverters. Attached Figure Description

[0012] Figure 1 A schematic diagram of a three-level thin-film capacitor integrated group designed according to this utility model;

[0013] Figure 2 Internal structure diagram of the three-level film capacitor designed for this utility model;

[0014] Figure 3 An exploded view of the three-level thin-film capacitor designed for this utility model;

[0015] Figure 4 This is a schematic diagram of the core structure;

[0016] Figure 5 This is a schematic diagram of the encapsulation cover.

[0017] Figure 6 This is a schematic diagram of the casing;

[0018] Figure 7 This is a schematic diagram of welding copper plates;

[0019] Figure 8 This is a schematic diagram showing the connection between a conventional lead-out electrode and a busbar.

[0020] Figure 9 This diagram illustrates the connection between the electrodes and the busbar in this design.

[0021] Figure 10 This is a schematic diagram showing the connection between the capacitor core and the soldered copper plate.

[0022] Figure 11 A schematic diagram showing the assembly of the core, welding copper plate, electrodes, and shell;

[0023] Figure 12 This is a schematic diagram of a metallized thin film structure. Detailed Implementation

[0024] See Figures 1 to 12As shown, a three-level film capacitor includes a capacitor housing 1 and a capacitor core 3. The capacitor core 3 comprises three core groups installed within the same capacitor housing 1. Each core group consists of two sets of cores 31 and 32 connected in parallel, with both ends fixedly connected to a welded copper plate 4. Since the current carrying capacity of the capacitor is related to the width and thickness of the metallized film, the narrower the metallized film, the stronger its current carrying capacity and the better its heat dissipation. Therefore, in this invention, the film width is narrowed, and two sets are connected in parallel to increase the current carrying capacity. The welded copper plate 4 is provided with electrode through holes. The busbar 5 has welding pins 41 and adhesive through-holes 42 on the welding copper plate. The adhesive through-holes 42 facilitate adhesive penetration during potting, ensuring full potting of the product. Lead-out electrodes 6 pass through the electrode through-holes. Since it is a three-level circuit, there are three lead-out electrodes. A stacked busbar configuration is used, with two electrodes passing through the through-holes of the uppermost busbar 5 without contact. The other electrode has a cross-shaped bracket at its bottom, passes through the through-hole, and is held in place by the cross-shaped bracket and welded in place. Welding is performed from bottom to top, using a cross-shaped bracket to hold the busbar in place, increasing weld strength and preventing excessive force. Figure 8 The problem of electrode detachment in the existing structure shown.

[0025] Conventional capacitors use a circular core design, which has the disadvantage of taking up a lot of space. With market changes, there is an increasing demand for smaller and more sophisticated products. Therefore, this invention uses a flat core made of metallized thin film instead of a circular core. Compared with a circular core, the flat core has a higher energy density and occupies relatively less space, making the internal space more compact, reducing volume, and saving space.

[0026] The capacitor casing 1 is made of aluminum, which has better heat dissipation performance compared to other metals. However, due to the presence of grease, dust, or excessive smoothness on the metal surface, the metal surface becomes a weak interface layer, which can affect the adhesion of the resin. Therefore, this invention features a polished inner surface to increase its roughness, and several reinforcing ribs 11 are added to the inner surface to further enhance the adhesion between the resin and the casing, preventing the casing from detaching. In addition, the outer surface of the aluminum casing is sandblasted to prevent corrosion of the casing under long-term outdoor high temperature and humidity conditions.

[0027] Conventional capacitors are directly encapsulated with epoxy resin. However, if the encapsulated surface area is large, cracking can easily occur over prolonged use. This invention addresses this by adding an encapsulation cover plate 2 to the encapsulated surface to prevent cracking caused by an excessively large encapsulated area. Simultaneously, the cover plate is made of insulating plastic to enhance the insulation between the leads and the casing.

[0028] The encapsulation insulating cover plate has a potting port 22 and a boss 21. The boss 21 can increase the creepage distance between the lead electrodes 6 and between the lead electrodes and the capacitor housing 1, thereby improving the insulation withstand voltage.

[0029] The film is made of 125℃ high-temperature resistant polypropylene film, which has low tensile strength, elongation at break, and thermal shrinkage, while exhibiting excellent resistance to high-temperature deformation. These characteristics ensure that the capacitor can continue to operate stably without performance degradation at a high temperature of 110℃. In terms of film coating design, a semi-T two-section edge-thickened structure is adopted. Conventional semi-T metallized safety films usually adopt a single-section design, which is prone to large metal area failure, leading to rapid capacity decay or even loss. Therefore, this invention modifies the conventional single-section design to a two-section design, namely a semi-T two-section metallized safety film. The film coating adopts a semi-trapezoidal two-section explosion-proof structure 301. The metal contact area of ​​the two sections, as well as the second section's transverse fuse, can provide overvoltage overload disconnection. Furthermore, the width of the transparent white strips on both sides of the metallized film is reduced from 0.4mm to 0.2mm, increasing the metal coating contact area, improving the effective capacity of the core, and reducing the outer diameter of the core. The introduction of a two-section design not only enhances the explosion-proof effect of the safety film but also significantly improves the overcurrent capacity of the capacitor core through the thickened coating design at the half-T edge, enabling the capacitor to maintain stable performance even under harsh operating conditions. The capacitor core is wound from a safety-resistant, high-temperature-resistant metallized polypropylene film with a half-trapezoidal two-section structure. The capacitor core provided by this invention, wound from a metallized polypropylene film with a half-trapezoidal two-section structure, possesses excellent high-temperature stability, high capacity, miniaturization, and enhanced explosion-proof and overcurrent capabilities, making it an ideal choice for capacitor manufacturing in high-temperature environments.

Claims

1. A three-level film capacitor, comprising a capacitor casing and a capacitor core, characterized in that, The capacitor core includes three core groups installed in the same capacitor housing. Each core group consists of two sets of cores connected in parallel and both ends are fixedly connected to a welded copper plate. The welded copper plate is connected to a busbar with electrode through holes. The electrode leads pass through the electrode through holes. The core is a flat core wound from a metallized thin film.

2. A three-level film capacitor according to claim 1, characterized in that, The capacitor casing is made of aluminum, and the inner wall of the aluminum casing is roughened and reinforced with intermittent reinforcing ribs.

3. A three-level film capacitor according to claim 1, characterized in that, An insulating encapsulation cover is provided on the potting surface of the capacitor casing.

4. A three-level film capacitor according to claim 3, characterized in that, The encapsulation insulating cover plate has an opening for filling glue and a boss.

5. A three-level film capacitor according to claim 1, characterized in that, Through holes for adhesive are made on the welding copper plate.

6. A three-level film capacitor according to claim 1, characterized in that, The metallized film is provided with a half-T two-section safety membrane structure.

7. A three-level film capacitor according to claim 1, characterized in that, The width of the transparent white stripes on both sides of the metallized film is reduced to 0.2 mm.

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