busbar for a capacitor and capacitor

Abstract

having capacitor (1) - a round shape, - a large number of winding elements (2), - at least one busbar (3) designed and arranged to connect the winding elements (2) in parallel, wherein the busbar (3) has several layers.

Description

[0001] The present invention relates to a busbar for a capacitor. Furthermore, the present invention relates to a capacitor comprising the busbar.

[0002] In high-frequency applications, a capacitor must meet the requirements defined in Table 1 within the operating bandwidth. Table 1: Requirements for a capacitor in high-frequency applications Requirements A Low equivalent series resistance (ESR) B Frequency-stable ESR C Low equivalent series inductance (ESL) D Homogeneous internal current distribution E Internal resonance avoidance

[0003] Overlapping busbars are used for high-frequency applications where low equivalent series inductance (ESL), low and frequency-stable equivalent series resistance (ESR), and homogeneous internal current distribution are required. The overlapping busbar also helps to avoid internal resonances between the components.

[0004] Round capacitors are typically internally divided by axially parallel windings. The internal structure (round windings and terminals) is housed in a round casing. The round shape of the capacitor makes the use of an internal overlapping busbar particularly complex from a mechanical perspective.

[0005] Conventionally, capacitor windings are connected with flat ribbons or wires without overlap. This design has the following disadvantages when good performance at high frequencies is required: - The operating bandwidth is limited to low frequencies (f< 10kHz); The DC-link capacitor is divided into several independent capacitors connected in parallel via an external power rail. However, if space is limited and the only dimension of the capacitor that can be increased is its height, the problem cannot be solved with an efficient mechanical solution.

[0006] One objective of the present disclosure is to solve the aforementioned problems. This objective is achieved by the busbar and the capacitor according to the independent claims.

[0007] According to a first aspect of the present disclosure, a busbar is provided. The busbar is designed for use in a capacitor. The busbar is designed for integration into a capacitor, in particular a cylindrical capacitor. The busbar is suitable and arranged for high-frequency applications. The busbar is laminated. In other words, the busbar is at least partially overlapping. The busbar is designed to have a greater width / greater extent perpendicular to a longitudinal axis of the capacitor / greater azimuthal extent than conventional busbars.

[0008] The busbar has a round shape. For example, the busbar has the shape of part of a cylindrical shell. The busbar is adapted to the outer shape of the capacitor into which it is to be integrated. In particular, the busbar is adapted to the winding shape of the capacitor.

[0009] The laminated busbar significantly reduces parasitic inductances and resistances (ESRi, Rp, Rp2, ESLi, Lp, Lp2). This makes the busbar particularly suitable for high-frequency applications.

[0010] According to one embodiment, the busbar comprises a first layer or a first pole. The busbar also comprises a second layer or a second pole. The layers may, for example, consist of copper. The layers of the busbar are designed and arranged so that they can be connected to the poles of a capacitor, in particular to the poles of winding elements of the capacitor. The busbar, and in particular the layers, have an overlap region. In this overlap region, the layers of the busbar overlap each other. This enables a short and very uniform electrical connection.

[0011] According to one embodiment, an insulating layer is arranged between the first and second layers. The insulating layer can, for example, comprise a polymer. The insulating layer is provided at least in the overlap area. In this way, a short circuit between the two layers of the busbar can be effectively prevented.

[0012] According to one embodiment, the first layer comprises a plurality of first connection areas. The second layer comprises a plurality of second connection areas. The overlap area of ​​the first layer and the respective first connection area merge seamlessly. In other words, the first layer and the first connection areas are formed as a single piece. The overlap area of ​​the second layer and the respective second connection area merge seamlessly; that is, the second layer and the second connection areas are formed as a single piece. Fault-prone connections between the overlap area and the connection areas are thus eliminated.

[0013] Another aspect is the provision of a capacitor. This capacitor is suitable for high-frequency applications. It comprises a variety of winding elements, such as two, three, four, or more. These winding elements are axially arranged, meaning they are positioned along a main longitudinal axis of the capacitor.

[0014] The capacitor also includes at least one busbar. Preferably, the capacitor has exactly one busbar. This busbar can be the busbar described above. Therefore, all features described in connection with the busbar also apply to the capacitor.

[0015] The capacitor has a round shape. The capacitor can also have a cylindrical shape. Accordingly, the respective winding element also has a cylindrical shape. The laminated / overlapping busbar is designed and arranged to connect the winding elements in parallel.

[0016] The laminated busbar ensures a shorter and more uniform electrical connection across the capacitor, thus improving its electrical performance compared to conventional capacitors. Parasitic inductances and resistances can be significantly reduced, regardless of the width of the capacitor's metallized film. Because C is homogeneous, the impedance (Z) between the capacitor terminals and each independent winding element is also homogeneous across the entire bandwidth.

[0017] According to one embodiment, the busbar is arranged inside the capacitor housing. Accordingly, the busbar is an internal busbar. Preferably, the busbar is arranged on the outside of the winding elements. Preferably, the busbar covers between 20 and 50% of the outside of the winding elements. The laminated busbar is very space-saving. In particular, capacitors with the laminated busbar described above can maintain similar dimensions to those with standard terminals (copper strips). Since the standard dimensions of the capacitor diameters are retained, good integration into the power converter is possible.

[0018] According to one embodiment, the busbar comprises a first layer or a first pole. The busbar also comprises a second layer or a second pole. The first and second layers are electrically insulated from each other. In particular, the layers are electrically insulated by the insulating layer described above.

[0019] The layers of the busbar extend at least partially along one outer side of the respective winding element. In other words, the busbar extends along the longitudinal axis on the outer side of the winding elements.

[0020] The busbar has an overlap zone. In this overlap zone, the layers / poles of the busbar overlap. Since the busbar extends along the longitudinal axis of the capacitor, it is a laterally overlapping busbar.

[0021] Preferably, the overlap area of ​​the busbar is between 5% and 40% of the outer surface of the winding elements. In other words, the busbar is extended in the longitudinal and azimuthal directions such that the area where the two layers overlap covers up to 40% of the outer surface of the winding elements. The greater the overlap, the better the compensation of parasitic inductances and resistances. The size of the overlap area depends on both the size of the capacitor and the number of windings.

[0022] According to one embodiment, the busbar has a shape adapted to the diameter of the respective winding element. In particular, the busbar has a round shape, e.g., the shape of part of a cylindrical shell. The busbar can be used with any number of windings. In other words, the length and / or azimuthal extent of the busbar can be adapted to the size and number of winding elements. This provides a highly versatile busbar.

[0023] According to one embodiment, the busbar comprises a plurality of connection areas. In particular, the first layer comprises a plurality of first connection areas. The second layer comprises a plurality of second connection areas. A number of first connection areas corresponds to a number of winding elements. Furthermore, a number of second connection areas corresponds to the number of winding elements.

[0024] The connection areas are designed and arranged so that they can be electrically and mechanically connected to the poles of the winding elements. The connection areas can be soldered to the poles of the winding elements. Accordingly, the first layer can be connected to the first pole of each winding element. The second layer can be connected to the second pole of each winding element. This ensures a short and very balanced electrical connection between the busbar and the poles. In this way, the electrical performance of the capacitor is increased.

[0025] Further features, refinements and advantages will become apparent from the following description of the exemplary embodiments in conjunction with the figures. Fig. Figure 1 schematically shows a simplified electrical model of a capacitance unit according to the state of the art. Fig. Figure 2 schematically shows a simplified electrical model of a state-of-the-art DC-link capacitor. The Fig. 3a and Fig. Figure 3b schematically shows a perspective view of a capacitor according to the state of the art. Fig. 4a and Fig. Figure 4b schematically shows a perspective view of parts of a capacitor. Fig. 5a and Fig. Figure 5b schematically shows a cross-sectional view of part of a capacitor. Fig. Figure 6 schematically shows a cross-sectional view of part of a capacitor. Fig. Figure 7 schematically shows a perspective view of part of a capacitor. Fig. Figure 8 schematically shows a perspective view of the capacitor according to Fig. 7, The Fig. Figures 9a to 9c schematically show a perspective view of parts of the capacitor according to the Fig. 7 and Fig. 8, Fig. Figure 10 schematically shows a comparative ESR measurement between a capacitor according to the prior art and the capacitor according to the present disclosure.

[0026] The Fig. 1, Fig. 2, Fig. 3a and Fig. 3b refers to a capacitor according to the state of the art. In particular, the Fig. 3a and Fig. 3b a conventional capacitor 100 from a first side ( Fig. 3a) and from the opposite side ( Fig. 3b). The capacitor 100 is divided into units Ci (see Fig. 1 and Fig. 2), which are connected in parallel by flat copper strips 102. Each capacitance unit Ci contains a capacitance element (winding element 101) and its connections to the copper strip 102.

[0027] The winding elements 101 are connected in parallel by the copper strips 102 without any overlap of the copper strips 102. The copper strips 102 electrically connect the terminals / poles 103 of the winding elements 101. Each copper strip 102 is fastened to its respective terminal 103 by means of a screw 104. Each copper strip 102 extends along an outer surface of the capacitor 100 and, in particular, outside the housing of the capacitor 100 (external busbar). In other words, one copper strip 102 extends along the first outer surface of the capacitor 100, and another copper strip 102 extends along the second (opposite) outer surface of the capacitor 100.

[0028] Fig.Figure 1 shows a simplified electrical model of the capacitance unit Ci (winding element 101 and its connection with the copper strip 102). Here, ESRi represents the parasitic ESR of the capacitance unit Ci and ESLi represents the parasitic ESL of the capacitance unit Ci.

[0029] A simplified electrical model of a complete DC-link capacitor (with a variety of capacitance units Ci) is shown in Fig. 2 shown, where - Ci: Capacity unit - Capacity value, - ESRi: Capacity unit - parasitic ESR, - ESLi: Capacity unit - parasitic ESL, - Cp: Connections between the capacity units - parasitic capacity, - Rp, Rp2: Connections between the capacitance units - parasitic resistance, - Lp, Lp2: Connections between the capacitance units - parasitic inductance, - Rt: Connection - parasitic resistance, - Lt: Connection - parasitic inductance.

[0030] The electrical requirements achieved with this solution are summarized in Table 2. Requirements Achieved through state-of-the-art technology A Low equivalent series resistance (ESR) No B Frequency-stable ESR No C Low equivalent series inductance (ESL) No D Homogeneous internal current distribution No E Internal resonance avoidance No

[0031] Table 2: Requirements for a capacitor in high-frequency applications, as met by state-of-the-art capacitors.

[0032] The Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. Figure 9 schematically shows a capacitor 1 according to the present invention. The capacitor 1 has a round structure. In other words, the capacitor 1 has a round outer shape. In particular, the capacitor 1 has the outer shape of a cylinder (see especially the Fig. 4a, 4b, 8 and 9a to 9c). Capacitor 1 is particularly suitable for use in high-frequency applications.

[0033] The capacitor 1 comprises a plurality of winding elements 2. In this embodiment, the capacitor 1 comprises three winding elements 2 ( Fig. 4a). Of course, the capacitor 1 can also comprise more than three winding elements 2, e.g., four, five, or six winding elements 2. The capacitor 1 can also have fewer than three winding elements 2, e.g., two winding elements 2. In particular, the number of winding elements 2 is freely selectable. In other words, the construction described below can be realized with any number of winding elements 2. Insulation 9 is arranged between successive winding elements 2, as shown in Fig. 8 is evident. The insulation 9 can, for example, contain a polymer.

[0034] The winding elements 2 are arranged axially, i.e., they are arranged along a main longitudinal axis 18 of the capacitor 1. The winding elements 2 are electrically connected in parallel. For this purpose, a laminated busbar 3 is provided ( Fig. 4b). In this context, the term “laminated” means that the busbar 3 has several layers (4a, 4b, 5; see e.g. Fig. 6). These layers, which will be explained in detail later, overlap at least partially along an outer side of the winding elements 2. In other words, the busbar 3 is a (laterally) overlapping busbar.

[0035] As from Fig. As can be seen in Figure 4b, the busbar 3 extends along the outside of the winding elements 2 (lateral busbar). The busbar 3 extends along the outside of the winding elements 2 from a first end face 10 to a second end face 11 of the capacitor 1 (see Figure 4b). Fig.8) The busbar 3 covers at least part of the outside of the respective winding element 2. Overall, the entire busbar 3 covers between 20% and 50% of the outside of the winding elements 2. The busbar 3 is an internal busbar. In other words, the busbar 3 is located within a housing 16 of the capacitor 1 (see Fig. 9c).

[0036] The busbar 3 has a round shape, which is particularly well suited to Fig.5a. The busbar 3 has the shape of an (incomplete) cylindrical shell. The busbar 3 has a shape adapted to an outer shape and / or diameter of the respective winding element 2 and the housing 16 of the capacitor 1. The busbar 3 can be used with any number of windings. The length (axial extent, i.e., extent along the main longitudinal axis 18 of the capacitor 1) of the busbar 3 is adapted to the number of winding elements 2.

[0037] The busbar 3 has the layers already mentioned. In particular, the busbar 3 comprises a first layer (first pole) 4a and a second layer (second pole) 4b, which, for example, Fig. 5b and Fig. 6 can be taken from it.

[0038] Layers 4a and 4b contain copper. Layers 4a and 4b have a thickness between 0.3 mm and 1.5 mm, preferably 0.5 mm.

[0039] Layers 4a and 4b overlap at least partially. In particular, in a partial region of the busbar 3 (overlap region 6), the first layer 4a and the second layer 4b are stacked radially to the capacitor 1. The size of the overlap region 6 (axial and azimuthal extent) is selected such that it covers between 5% and 40% of the outer surface of the winding elements 2. Preferably, the overlap region 6 covers 30% of the outer surface of the winding elements 2.

[0040] Layers 4a and 4b are electrically insulated from each other by an insulating layer 5. The insulating layer 5 comprises a polymer. The thickness of the insulating layer 5 is between 0.2 mm and 2.5 mm. Preferably, the thickness of the insulating layer 5 is 0.5 mm.

[0041] The insulating layer 5 is arranged between the first layer 4a and the second layer 4b, at least in the overlap region 6 of the two layers 4a, 4b. In fact, the insulating layer 5 extends beyond the overlap region 6 in an azimuthal and / or axial direction, as can be seen, for example, from Fig. 5b is evident. In other words, the azimuthal and / or longitudinal extent of the entire busbar 3, including layers 4a, 4b and the insulating layer 5, is greater than the azimuthal extent of the overlap area 6 (see e.g. Fig. 7 and Fig. 8).

[0042] The first layer 4a is connected to a first pole 17a (e.g. the negative pole) of the respective winding element 2 ( Fig. 7). The second layer 4b is connected to a second pole 17b (e.g. the positive pole) of the respective winding element 2.

[0043] The first layer 4a comprises a plurality of first connection areas 7a. The second layer 4b comprises a plurality of second connection areas 7b. In this embodiment, each layer 4a, 4b comprises three connection areas 7a, 7b. The number of each connection area 7a, 7b corresponds to the number of winding elements 2.

[0044] The first connection areas 7a and the first layer 4a are formed in one piece. The second connection areas 7b and the second layer 4b are formed in one piece. The respective connection area 7a, 7b is rod-shaped. The respective connection area 7a, 7b extends parallel to the layers 4a, 4b along the outer surface of the respective winding element 2. In an intermediate section 19a, 19b (see Fig. 7 and Fig.8) The respective layer 4a, 4b transitions into the respective connecting area 7a, 7b. The intermediate section 19a, 19b extends perpendicularly to the connecting areas 7a, 7b.

[0045] The respective connection areas 7a, 7b are electrically and mechanically connected to the respective pole 17a, 17b of a winding element 2 for parallel connection of the winding elements 2. The connection areas 7a, 7b are connected to the poles 17a, 17b via a connection element 8, e.g. a metal strip ( Fig. 7 and Fig. 8). The connection areas 7a, 7b can be soldered to the poles 17a, 17.

[0046] For the electrical and mechanical connection of the busbar 3 with the terminals 13a, 13b of the capacitor 1, the capacitor 1 further comprises a first and a second terminal element 12a, 12b ( Fig. 8 and Fig.9a). The terminal elements 12a, 12b are arranged at the first end face 10 of the capacitor 1. The terminal elements 12a, 12b have, for example, metal strips. The terminal elements 12a, 12b are bent to connect the busbar 3 arranged on the side face of the winding elements 2 to the terminals 13a, 13b, which are arranged at the first end face 10 of the capacitor 1. A termination element 20 is arranged at the first end face 10 between the winding element 2 and the terminal elements 12a, 12b ( Fig. 8) The end element 20 has an insulating material, e.g. a polymer.

[0047] In a first end area, the first connection element 12a is connected to the first layer 4a of the busbar 3, e.g. by soldering ( Fig. 8 and Fig. 9a). Likewise, in a first end area, the second connection element 12b is connected to the second layer 4b of the busbar 3, e.g. by soldering ( Fig. 8 and Fig. 9a).

[0048] In a second or opposite end area, the first terminal element 12a is connected to the first terminal 13a, e.g. by means of a screw or by soldering ( Fig. 9a). Likewise, in a second or opposite end area, the second terminal element 12b is connected to the second terminal 13b, e.g. by means of a screw or by soldering ( Fig. 9a).

[0049] An external insulation 14 is arranged on the side surface of the winding elements 2 above the connection elements 12a, 12b ( Fig.9b). The external insulation 14 is strip-shaped. The external insulation 14 is round and extends partially around the outer surface of the winding element 2 located near the first end face 10 of the capacitor 1. The external insulation 14 electrically insulates the terminal elements 12a, 12b from the housing 16 of the capacitor 1, which is located on the external insulation 14 and completely covers the winding elements 2 and the busbar 3 ( Fig. 9c).

[0050] Furthermore, a cover 15 is arranged on the connection elements 12a, 12b at the first end side 10 ( Fig. 9b and Fig.9c). The cover 15 has two recesses. The recesses are designed and positioned to accommodate the terminals 13a and 13b. The terminals 13a and 13b protrude axially from the recesses. This allows for an electrical connection of the capacitor 1. The cover 15 serves as the termination element of the first end 10 of the capacitor 1. A corresponding cover without recesses is arranged at the second end 11 of the capacitor 1 (not explicitly shown).

[0051] The design described above allows for a significant reduction in parasitic inductances and resistances (ESRi, Rp, Rp2, ESLi, Lp, Lp2), regardless of the width of the capacitor's metallized film. Furthermore, assuming C is homogeneous, the impedance between terminals 13a, 13b, and each independent winding is homogeneous across the entire bandwidth. Therefore, the requirements summarized in Table 3 can be met. Requirements Fulfilled by the state of the art Fulfilled by the present invention A Low equivalent series resistance (ESR) No Yes B Frequency-stable ESR No Yes C Low equivalent series inductance (ESL) No Yes D Homogeneous internal current distribution No Yes E Internal resonance avoidance No Yes

[0052] Table 3: Requirements for a capacitor for high-frequency applications, as achieved by capacitors according to the prior art compared to the capacitor according to the present invention.

[0053] Fig. Figure 10 schematically shows a comparative ESR measurement between capacitor 100 according to the state of the art ( Fig. 3a, Fig. 3b) and the capacitor 1 according to the present disclosure ( Fig. 4, Fig. 5, Fig.6, Fig. 7, Fig. 8 to Fig. 9) It can be observed that the ESR in the prior art is less frequency-stable than the ESR of the capacitor according to the present invention. This is due to a higher skin effect, an inhomogeneous internal current distribution, and internal resonances in the prior art capacitor design.

[0054] In the figures, elements of the same structure and / or functionality can be designated with the same reference symbols. It goes without saying that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. Reference sign 1 Capacitor 2 winding element 3 Power rail 4a First shift 4b Second shift 5 Insulation layer 6 Overlap area 7a First connection area 7b Second connection area 8 Connection element 9 Insulation 10 First end face of the capacitor 11 Second end of the capacitor 12a First connection element 12b Second connection element 13a First connection 13b Second connection 14 Insulation 15 Cover 16 cases 17a First Pole 17b Second Pole 18 Main longitudinal axis 19a First Intermediate Section 19b Second Intermediate Section 20 Final element 100 Capacitor 101 Winding element 102 copper tape 103 connection 104 screw Ci Capacity Unit - Capacity Value ESRi capacity unit - parasitic ESR ESLi capacity unit - parasitic ESL Cp connections between capacity units - parasitic capacity Rp, Rp2 connections between capacitance units - parasitic resistance Lp, Lp2 connections between capacitance units - parasitic inductance Rt connection - parasitic resistance Lt connection - parasitic inductance

Claims

Capacitor (1) having a round shape, a plurality of winding elements (2), at least one busbar (3) designed and arranged to connect the winding elements (2) in parallel, the busbar (3) having several layers. Capacitor (1) according to claim 1, wherein the busbar (3) comprises a first layer (4a), a second layer (4b) and an insulating layer (5). Capacitor (1) according to claim 2, wherein the first layer (4a) and the second layer (4b) of the busbar (3) extend at least partially along an outside of the respective winding element (2). Capacitor (1) according to claim 2 or claim 3, wherein the busbar (3) has an overlap area (6) in which the layers (4a, 4b) overlap. Capacitor (1) according to claim 4, wherein the insulating layer (5) of the busbar (3) is arranged between the first and second layers (4a, 4b) of the busbar (3) at least in the overlap area (6). Capacitor (1) according to one of claims 2 to 5, wherein the first layer (4a) of the busbar (3) is connected to a first pole (17a) of a respective winding element (2) and wherein the second layer (4b) of the busbar (3) is connected to a second pole (17b) of a respective winding element (2). Capacitor (1) according to one of the preceding claims, wherein the busbar (3) has a shape adapted to a diameter of the respective winding element (2). Capacitor (1) according to one of the preceding claims, wherein the busbar (3) has a plurality of connection areas (7a, 7b) which are designed and arranged in such a way that they can be electrically and mechanically connected to poles (17a, 17b) of the winding elements (2). Capacitor (1) according to one of claims 4 to 8, wherein the first layer (4a) of the busbar (3) comprises a plurality of first connection areas (7a) and the second layer (4b) of the busbar (3) comprises a plurality of second connection areas (7b), wherein the overlap area (6) of the first layer (4a) and the respective first connection area (7a) merge into each other, and wherein the overlap area (6) of the second layer (4b) and the respective second connection area (7b) merge into each other. Capacitor (1) according to claim 9, wherein the number of first connection areas (7a) of the busbar (3) corresponds to a number of winding elements (2) and wherein the number of second connection areas (7b) of the busbar (3) corresponds to the number of winding elements (2). Capacitor (1) according to one of the preceding claims, wherein the busbar (3) is designed and arranged for high-frequency applications. Capacitor (1) according to one of the preceding claims, wherein an extension of the busbar (3) along a principal longitudinal axis (18) of the capacitor (1) is adapted to a number of winding elements (2). Capacitor (1) according to one of the preceding claims, wherein the busbar (3) extends along an outside of the winding elements (2) from a first end side (10) to a second end side (11) of the capacitor (1). Capacitor (1) according to one of claims 8 to 13, wherein the connection areas (7a, 7b) of the busbar (3) are connected to the poles (17a, 17b) by means of a connection element (8). Capacitor (1) according to claim 14, wherein the connecting element (8) comprises a metal strip. Capacitor (1) according to one of the preceding claims, wherein the busbar (3) is a single overlapping busbar and wherein all winding elements (2) are connected to the single overlapping busbar (3). Capacitor (1) according to one of the preceding claims, wherein the busbar (3) is arranged inside a housing (16) of the capacitor (1). Capacitor (1) according to one of the preceding claims, designed for use in high-frequency applications.

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