Multifunctional low-inductance large-capacity polypropylene film capacitor

Abstract

The application discloses a kind of multi-functional low-inductance large-capacity polypropylene film capacitors, belong to film capacitor technical field.The capacitor includes plastic shell, A electrode busbar and B electrode busbar, ground row, support capacitor core, absorption capacitor core and Y capacitor core arranged in the form of laminated in the inside of plastic shell.Multiple support capacitor cores are connected in parallel on two busbars;Absorption capacitor core is directly placed just below electrode lead-out end, and two ends are connected with lead-out end extremely short path respectively through busbar II;Y capacitor core is connected with busbar and ground row respectively.The application highly integrates three kinds of functional cores in the same shell, greatly reduces the system volume and weight, reduces the case connection and risk point;Busbar laminated arrangement effectively offsets parasitic inductance;The super-short path layout of absorption capacitor core greatly improves the high-frequency peak absorption effect, and perfectly adapts to the demand of high-frequency power electronic application.

Description

Technical Field

[0001] This invention relates to the field of film capacitor technology, and more specifically, to a multifunctional, low-inductance, high-capacity polypropylene film capacitor. Background Technology

[0002] Polypropylene film capacitors are widely used in power electronic equipment due to their excellent high-frequency insulation properties and low temperature variation. As traditional IGBT modules in power electronics technology gradually shift to high-frequency SiC modules, more stringent requirements are being placed on the parasitic inductance (ESL), equivalent series resistance (ESR), and size and weight of film capacitors.

[0003] Currently, existing technologies mainly suffer from the following drawbacks: 1. In traditional solutions, manufacturers produce pulse film capacitors for peak absorption, Y capacitors for electromagnetic interference suppression, and DC support capacitors separately, depending on the application scenario. This requires each type of capacitor to be individually packaged, which not only greatly increases the overall size and weight of the capacitors (a fatal weakness in weight-sensitive fields such as aerospace), but also makes the internal wiring of the chassis cumbersome, and the large number of connection points increases the risk of poor soldering and failure.

[0004] 2. Traditional DC support capacitors do not use integrated busbars or multilayer busbars, resulting in a large equivalent series inductance (ESL). Under the high-frequency operation of SiC modules, the large parasitic inductance can easily cause oscillations and circulating currents in the circuit, leading to a significant decrease in filtering characteristics, generating additional losses, and causing severe overheating or even failure of the capacitor.

[0005] 3. Traditional absorption capacitors use a conventional overlapping connection method, resulting in a long lead path between the capacitor core and the lead terminals, leading to a large parasitic inductance in the leads. At high frequencies, excessive parasitic inductance in the leads hinders the capacitor's rapid charging, causing high-frequency overvoltage spikes to be unable to be effectively and completely absorbed. Summary of the Invention

[0006] The present invention provides a multifunctional low-inductance, high-capacity polypropylene film capacitor to solve the technical problems of large size and weight, complex wiring, and large parasitic inductance and poor peak absorption effect caused by the separate setting of different functional capacitors in the prior art.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows: A multifunctional low-inductance, high-capacity polypropylene film capacitor includes: a plastic shell, an A-electrode busbar, a B-electrode busbar, a grounding busbar, a supporting capacitor core, an absorbing capacitor core, and a Y-capacitor core. Both the A electrode busbar and the B electrode busbar are located inside the plastic shell and are arranged in a stacked manner; the A electrode busbar is provided with multiple A electrode leads and the B electrode busbar is provided with multiple B electrode leads, and both the A electrode leads and the B electrode leads extend out of the plastic shell. The supporting capacitor cores are multiple, and the multiple supporting capacitor cores are connected in parallel through busbar I and overlapped on the A electrode busbar and the B electrode busbar; There are multiple absorption capacitor cores, and the multiple absorption capacitor cores are respectively placed below the corresponding A electrode lead and B electrode lead. Both ends of each absorption capacitor core are connected to the corresponding A electrode lead and B electrode lead through busbar II respectively. The Y capacitor core is at least two, one of which is connected to the A electrode busbar and the ground busbar respectively through busbar III, and the other Y capacitor core is connected to the B electrode busbar and the ground busbar respectively through busbar III.

[0008] Furthermore, there are three A electrode leads and three B electrode leads, forming three sets of electrode leads in a one-to-one correspondence; there are three absorption capacitor cores, which are respectively placed below the three sets of electrode leads.

[0009] Furthermore, the grounding busbar has a grounding busbar lead-out end, and an anti-rotation groove is formed on the plastic shell. A portion of the grounding busbar lead-out end is embedded in the anti-rotation groove. The depth of the anti-rotation groove is less than the thickness of the grounding busbar lead-out end, so that a portion of the grounding busbar lead-out end protrudes above the anti-rotation groove.

[0010] Furthermore, both the A electrode busbar and the B electrode busbar are integrally formed structures.

[0011] Furthermore, the supporting capacitor core is wound from a high sheet resistance metallized polypropylene film with a thickened edge, and the metallized coating of the high sheet resistance metallized polypropylene film is divided into two regions: a thickened edge and a non-thickened edge.

[0012] Furthermore, the absorption capacitor core is formed by winding a double-sided metallized polypropylene film and a white polypropylene film.

[0013] Furthermore, the Y capacitor core is formed by winding a thin film with an internal series structure.

[0014] Furthermore, the busbar I and the end face of the supporting capacitor core, the busbar II and the end face of the absorbing capacitor core, and the busbar III and the end face of the Y capacitor core are all connected by spot welding; the end faces of the supporting capacitor core, the absorbing capacitor core, and the Y capacitor core all have a multi-layer gold sprayed layer formed by air spraying process.

[0015] Furthermore, after the cores and busbars are assembled, the internal gaps of the plastic shell are filled with cured epoxy resin.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention integrates a supporting capacitor core that provides DC support, an absorbing capacitor core that absorbs spikes, and a Y-capacitor core that suppresses electromagnetic interference into a single plastic housing. Compared to the traditional use of multiple capacitors in combination, the overall volume can be reduced by about 30%, the weight by about 20%, the required housing is reduced from 6 to 1, and the number of encapsulation steps is reduced from 6 to 1. This not only reduces production costs but also significantly reduces the number of contact points inside the chassis, thus reducing potential risks.

[0017] (2) The present invention stacks the A electrode busbar and the B electrode busbar inside, and uses the magnetic fields generated by the opposite current directions to cancel each other out, which greatly reduces the equivalent series inductance (ESL) and equivalent series resistance (ESR) of the capacitor, reduces additional losses, significantly reduces heat generation, and better adapts to the application scenarios of high frequency SiC modules.

[0018] (3) The present invention has a special topological layout for the absorption capacitor core, which is placed directly below the A and B electrode leads and connected nearby through bus II. This design makes the current path the shortest and the lead parasitic inductance the smallest, thereby ensuring that it can respond extremely quickly and completely absorb overvoltage spikes under high frequency conditions.

[0019] (4) For chassis installation scenarios, the present invention creatively designs an anti-rotation groove on the plastic shell. After the grounding busbar lead-out end is embedded in the anti-rotation groove, when the screw is tightened, the anti-rotation groove can effectively prevent the grounding busbar lead-out end from rotating, avoiding deformation and breakage of the lead-out end, and ensuring long-term grounding reliability.

[0020] (5) The supporting capacitor core of the present invention adopts a high sheet resistance metallized polypropylene film with thickened edges, which takes into account both voltage resistance and current resistance and reduces volume; the absorbing capacitor core adopts a combination of double-sided metallized film and white film, which enables it to withstand pulsed large current of thousands of V / μs voltage impact; the Y capacitor core adopts an inner series structure film, which greatly ensures the overvoltage resistance capability.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, embodiments of the present invention are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is an external view of the polypropylene film capacitor in the embodiment; Figure 2 This is a first-dimensional view of the internal structure of the polypropylene film capacitor in the embodiment; Figure 3 This is a second stereoscopic view of the internal structure of the polypropylene film capacitor in the embodiment; Figure 4 This is a first-level view of the internal structure of the polypropylene film capacitor in the embodiment; Figure 5 This is a second head-up view of the internal structure of the polypropylene film capacitor in the embodiment; Figure 6 This is a structural diagram of the polypropylene film capacitor in the embodiment, showing the layout of busbar I, where the supporting capacitor core has been removed; Figure 7 This is a structural diagram of the capacitor being assembled on the tooling in the embodiment; Explanation of reference numerals in the attached drawings: 1-Plastic casing; 2-A electrode busbar; 3-B electrode busbar; 4-Grounding busbar; 5-Busbar I; 6-Busbar II; 7-Busbar III; 8-Absorption capacitor core; 9-Y capacitor core; 10-Support capacitor core; 11-Base plate; 12-Positioning plate; 13-Positioning screw; 14-Anti-rotation groove. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0025] This invention provides a multifunctional, low-inductance, high-capacity polypropylene film capacitor that integrates peak absorption, electromagnetic interference suppression, and DC support. It should be noted that, since polypropylene capacitors do not have positive and negative terminals, the letters A and B will be used below to refer to the different terminals inside the capacitor.

[0026] like Figures 1 to 6 As shown, the capacitor includes: a plastic casing 1, an A-electrode busbar 2, a B-electrode busbar 3, a ground busbar 4, a supporting capacitor core 10, an absorption capacitor core 8, and a Y-capacitor core 9. This capacitor integrates three different functional cores inside the plastic casing 1, with the specific layout and structure as follows: Both electrode busbar 2 (A) and electrode busbar 3 (B) are located inside the plastic housing 1. Electrode busbar 2 and electrode busbar 3 are arranged in a stacked configuration inside the plastic housing 1. Figure 5 As shown, the stacked arrangement design allows the magnetic fields generated by the opposite current directions in the two busbars to cancel each other out when alternating current passes through them, thus effectively reducing the parasitic inductance (ESL) of the capacitor. Simultaneously, both electrode A busbar 2 and electrode B busbar 3 are integrally molded structures. This integrated design reduces the number of solder joints inside the capacitor, lowering the risk of poor soldering due to numerous solder joints and reducing the equivalent series resistance (ESR) of the capacitor, ultimately significantly reducing heat generation and losses.

[0027] Electrode busbar 2 has multiple A-electrode leads, and electrode busbar 3 has multiple B-electrode leads. In this embodiment, preferably, there are three A-electrode leads and three B-electrode leads, forming three sets of electrode leads (each set includes one A-electrode lead and one adjacent B-electrode lead). Each A-electrode lead and each B-electrode lead extends through the plastic housing 1 to connect to an external circuit (such as a SiC power module).

[0028] When this capacitor is used in a chassis, it is fixed to the chassis with screws. The grounding busbar 4 has a grounding busbar lead-out terminal. To prevent the grounding busbar lead-out terminal from rotating during installation, which could cause torsional deformation or even breakage, an anti-rotation design is added to the plastic casing 1. For example... Figure 1 As shown in the enlarged view, the plastic casing 1 has an anti-rotation groove 14, and part of the grounding busbar lead-out end is embedded in the anti-rotation groove 14. Furthermore, the depth of the anti-rotation groove 14 is less than the thickness of the grounding busbar lead-out end, so that a portion of the grounding busbar lead-out end protrudes above the anti-rotation groove 14 after being embedded. This allows the screws to tightly press against the protruding grounding busbar lead-out end when it is fixed to the chassis, ensuring reliable grounding while preventing rotation of the grounding busbar lead-out end through the sidewall limitation of the anti-rotation groove 14.

[0029] The following describes the core arrangement and connection method: (1) Support capacitor core 10 that provides DC support The supporting capacitor core 10 consists of multiple capacitors (in this embodiment, combined with...). Figure 2 , Figure 3As can be seen, they are arranged in an array, with a preferred number of 18. Multiple supporting capacitor cores 10 are connected in parallel through busbar I5 and overlapped on the A electrode busbar 2 and the B electrode busbar 3 to form a large-capacity supporting capacitor with a capacitance range of several hundred μF to several thousand or even tens of thousands of μF, which serves as DC support, energy storage and smoothing filtering functions.

[0030] (2) Absorption capacitor core that performs peak absorption 8 There are three absorption capacitor cores 8, each corresponding to one of the three sets of electrode leads. The three absorption capacitor cores 8 are placed directly below the corresponding A electrode lead and B electrode lead. The two ends of each absorption capacitor core 8 are connected to the corresponding A electrode lead and B electrode lead respectively through two busbars II 6.

[0031] The principle behind this layout is that the parasitic inductance of the capacitor consists of two parts: the inductance of the core itself and the inductance of the leads. Since the core itself is made using non-inductive winding, its parasitic inductance is relatively small. According to the formula for calculating copper sheet inductance, the shorter the busbar path, the smaller the parasitic inductance of the leads. At high frequencies, if the parasitic inductance is too large, the capacitor will not be able to charge quickly enough and thus cannot fully absorb spikes. This invention places the absorption capacitor core 8 directly below the leads and connects it to the busbar via an extremely short busbar II 6, minimizing the current path. Compared to traditional combined lead methods, this significantly reduces parasitic inductance, thereby ensuring excellent spike absorption performance under high-frequency conditions.

[0032] (3) Y capacitor core that plays a role in suppressing electromagnetic interference 9 There are at least two Y-capacitor cores 9 (two in this embodiment). One Y-capacitor core 9 is connected at both ends to the A-electrode busbar 2 and the ground busbar 4 via two busbars III7 respectively; the other Y-capacitor core 9 is connected at both ends to the B-electrode busbar 3 and the ground busbar 4 via two other busbars III7. This achieves the connection between the internal circuitry and the chassis, effectively suppressing electromagnetic interference (EMI).

[0033] To ensure the performance of the various cores integrated within the same housing under harsh operating conditions, this embodiment employs targeted selection of the winding film for each core: The supporting capacitor core 10, primarily responsible for large-capacity energy storage and smoothing filtering, is wound from a high sheet resistance metallized polypropylene film with thickened edges. The metallization coating of this high sheet resistance metallized polypropylene film is divided into two regions: a thickened edge and a non-thickened edge. The thickened edge improves the current withstand capability of the supporting capacitor core 10, while the high sheet resistance of the non-thickened edge improves the voltage withstand capability. Therefore, while ensuring current and voltage withstand capabilities, a thinner film can be used to fabricate the core, further reducing the product size.

[0034] For the absorption capacitor core 8, due to the need to withstand high dv / dt (voltage change rate) and extremely high pulse current capability, it is made of a combination of double-sided metallized polypropylene film and polypropylene white film wound together. Its current withstand capability is tens of times that of a single-sided metallized film wound core, and it can withstand voltage surges of hundreds or even thousands of V / μs.

[0035] For the Y capacitor core 9, in order to ensure the core's resistance to voltage surges and overvoltages, it is made of a thin film with an internal series structure.

[0036] The fabrication process of the multifunctional low-inductance high-capacity polypropylene film capacitor described in this embodiment mainly includes the following steps S1-S7, and specific process parameters are used to ensure the realization of the claimed structure: S1, Winding: Select the corresponding film for winding according to the specific selection requirements of the cores with different functions mentioned above.

[0037] S2, Heat treatment: After flattening each wound core, place it on the upper clamping fixture and apply a pressure of 2 MPa. Then, place it in a vacuum oven for pressurized heat treatment and drying to fully remove the moisture and excess gas inside the core and ensure the electrical performance of each core.

[0038] S3, Gold Spraying: After heat treatment, the core is wrapped with a masking tape and then gold sprayed. To ensure the adhesion between the gold spraying layer and the core end face, and to improve the strength of the gold spraying layer, an air-jet process is used to form multiple gold spraying layers on the core end face.

[0039] S4, Core Welding: The end faces of busbar I5 and supporting capacitor core 10, busbar II6 and absorption capacitor core 8, and busbar III7 and Y capacitor core 9 are all connected by spot welding to form each functional core group.

[0040] S5, Core assembly welding: To ensure the reliability of product assembly dimensions and busbar welding, this embodiment adopts the following... Figure 7 The customized fixture shown is used for positioning welding. The fixture includes a base plate 11, a positioning plate 12, and positioning screws 13. The base plate 11 is used to fix the positioning plate 12 and the plastic housing 1 of the capacitor. The positioning plate 12 and the positioning screws 13 together fix the electrode leads of the busbar. To improve positioning accuracy, the mating points of the positioning screws 13, the positioning plate 12, and the electrode leads of the busbar are all designed with oblong holes.

[0041] In specific operation, first fix the plastic shell 1 on the fixture, then put each core group and grounding bus 4 into the plastic shell 1 in sequence; then fix the A electrode bus 2 on the fixture, and spot weld the bus plate on one side of the supporting capacitor core group and the absorbing capacitor core group to the A electrode bus 2; after completing the above welding, fix the B electrode bus 3 on the positioning fixture, and spot weld the remaining supporting capacitor core group and the bus plate on one side of the absorbing capacitor core group to the B electrode bus 3.

[0042] S6, Injection: After welding is completed, epoxy resin is injected into the internal gap of the plastic shell 1 using a tooling.

[0043] S7, Curing: The filled capacitor and its tooling are placed in an oven for heating and curing, so that the epoxy resin is cured and formed, thereby obtaining a high-strength, high-insulation and high-thermal-conductivity resin encapsulation, which greatly improves the encapsulation effect and shock resistance.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multifunctional low-inductance, high-capacity polypropylene film capacitor, characterized in that, include: Plastic casing (1), A electrode busbar (2), B electrode busbar (3), grounding busbar (4), supporting capacitor core (10), absorbing capacitor core (8) and Y capacitor core (9); The A electrode busbar (2) and the B electrode busbar (3) are both located inside the plastic shell (1) and are arranged in a stacked manner; the A electrode busbar (2) is provided with multiple A electrode leads, and the B electrode busbar (3) is provided with multiple B electrode leads, and both the A electrode leads and the B electrode leads extend out of the plastic shell (1). There are multiple supporting capacitor cores (10), and the multiple supporting capacitor cores (10) are connected in parallel through busbar I (5) and overlapped on the A electrode busbar (2) and the B electrode busbar (3); There are multiple absorption capacitor cores (8), and the multiple absorption capacitor cores (8) are respectively placed below the corresponding A electrode lead-out end and B electrode lead-out end. Both ends of each absorption capacitor core (8) are connected to the corresponding A electrode lead-out end and B electrode lead-out end respectively through busbar II (6). There are at least two Y capacitor cores (9). One of the Y capacitor cores (9) is connected to the A electrode busbar (2) and the ground busbar (4) respectively through busbar III (7). The other Y capacitor core (9) is connected to the B electrode busbar (3) and the ground busbar (4) respectively through busbar III (7).

2. The multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The number of A electrode leads and B electrode leads are both three, and they form three sets of electrode leads in a one-to-one correspondence; the number of absorption capacitor cores (8) is three, and the three absorption capacitor cores (8) are respectively placed below the three sets of electrode leads.

3. The multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The grounding bar (4) has a grounding bar lead-out end, and the plastic shell (1) has an anti-rotation groove (14) on it. Part of the grounding bar lead-out end is embedded in the anti-rotation groove (14). The groove depth of the anti-rotation groove (14) is less than the thickness of the grounding bar lead-out end, so that part of the grounding bar lead-out end protrudes above the anti-rotation groove (14).

4. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, Both the A electrode busbar (2) and the B electrode busbar (3) are integrally molded structures.

5. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The number of supporting capacitor cores (10) is 18.

6. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The supporting capacitor core (10) is made of a high sheet resistance metallized polypropylene film with a thickened edge, and the metallized coating of the high sheet resistance metallized polypropylene film is divided into two regions: a thickened edge and a non-thickened edge.

7. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The absorption capacitor core (8) is formed by winding a double-sided metallized polypropylene film and a white polypropylene film.

8. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The Y capacitor core (9) is formed by winding a thin film with an internal series structure.

9. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in claim 1, characterized in that, The busbar I (5) and the end face of the supporting capacitor core (10), the busbar II (6) and the end face of the absorbing capacitor core (8), and the busbar III (7) and the end face of the Y capacitor core (9) are all connected by spot welding; the end faces of the supporting capacitor core (10), the absorbing capacitor core (8) and the Y capacitor core (9) all have a multi-layer gold sprayed layer formed by air spraying process.

10. A multifunctional low-inductance, high-capacity polypropylene film capacitor as described in any one of claims 1 to 9, characterized in that, After the cores and busbars are assembled, the internal gaps of the plastic shell (1) are filled with cured epoxy resin.

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