capacitor

Abstract

The present invention relates to a capacitor including at least four winding elements (1 to 6) arranged in a stack, each of the winding elements (1 to 6) having a top surface (1 b to 6 b) and a bottom surface (1 a to 6 a), a first busbar (7) and a second busbar (8), wherein, in a stacking direction (S) of the stack, the first busbar (7) is coupled to the top surface (1 a) of a first winding element (1), the top surface (6 b) of a last winding element (6), and the bottom surfaces (2 a to 5 a) of the other winding elements (2 to 5), and the second busbar (8) is coupled to the bottom surface of the first winding element (1), the bottom surface of the last winding element (6), and the top surfaces of the other winding elements (2 to 5) in the stacking direction (S) of the stack.

Description

[Technical Field]

[0001] The present invention relates to a capacitor. In particular, the capacitor may be a metallized DC link film capacitor. The capacitor may be a power capacitor. [Background technology]

[0002] When constructing a DC link capacitor, the objective is to provide a capacitor with low equivalent series inductance (ESL). WO 2019 / 101802 A1 proposes a capacitor in which the polarity of each winding element is reversed relative to adjacent winding elements. While this design provides low ESL, it has the disadvantages of requiring a large amount of copper and multiple insulating sheets between winding elements. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved capacitor. [Means for solving the problem]

[0004] This object is solved by the subject matter of claim 1. The dependent claims relate to preferred embodiments of the capacitor.

[0005] A capacitor is provided that includes at least four winding elements arranged in a stack, each having a top surface and a bottom surface. The top surface may be opposite the bottom surface. A winding axis of the winding element may be perpendicular to each of the top surface and the bottom surface. The winding elements may be capacitance units. Each winding element of the capacitor may have the same capacitance. Each winding element may have a first pole of a first polarity, e.g., positive polarity, and a second pole of a second polarity, e.g., negative polarity. Energy may be stored in the winding element by applying a voltage between the first pole and the second pole.

[0006] The capacitor includes a first bus bar and a second bus bar, which may be a metal strip, a metal bar, or a metal sheet configured for localized high current power distribution.

[0007] In the stacking direction of the winding elements, the first bus bar is connected to the top surface of the first winding element, the top surface of the last winding element, and the bottom surfaces of the remaining winding elements, and in the stacking direction of the winding elements, the second bus bar is connected to the bottom surface of the first winding element, the bottom surface of the last winding element, and the top surfaces of the remaining winding elements.

[0008] Thus, the top surface of the outermost winding element of the stack can be connected to a first busbar, the bottom surfaces of all other winding elements can also be connected to the first busbar, the bottom surface of the outermost winding element can be connected to a second busbar, and the top surfaces of the other winding elements can also be connected to the second busbar.

[0009] This arrangement of the first and second busbars results in a stack of winding elements, with the outermost winding element having an opposite polarity compared to the other winding elements in the stack, where in each pair of adjacent winding elements, the adjacent winding elements have the same polarity except for the pair formed by the first and second winding elements and the pair formed by the penultimate and last winding elements.

[0010] By reversing the polarity of only the outermost winding elements, the magnetic flux of the magnetic field generated by each winding element in the stack can be fully compensated, resulting in a capacitor with low ESL.

[0011] This capacitor is suitable for power applications with voltages above 600V and switching frequencies above 10kHz. By reversing the polarity of the outermost winding element, the magnetic fields generated by each winding element in the stack are weakened or even cancelled out. Therefore, when a voltage is applied to the winding elements of the stack, only a very weak magnetic field is generated overall. This results in low inductance in the connections between the winding elements and the busbar. Therefore, the inductance of the capacitor is very low. Low inductance between the winding elements is important for power capacitors because high inductances can cause resonance effects and high losses due to parasitic inductance and resistance.

[0012] Additionally, the polarity of the outermost winding elements is reversed, reducing the inductance of the overlapping busbars and therefore the overall inductance of the device.

[0013] The term "stack" can refer to a set of winding elements arranged adjacent to each other in the stacking direction. The first winding element of a stack can be defined as a winding element that is arranged adjacent to another winding element, i.e., the second winding element, in the stacking direction and not arranged adjacent to any further winding elements in the opposite direction to the stacking direction. The last winding element of a stack can be defined as a winding element that is arranged adjacent to another winding element, i.e., the penultimate winding element, in the stacking direction and not arranged adjacent to any further winding elements in the stacking direction. Thus, each of the outermost winding elements of a stack can be adjacent to only one winding element of the stack, and each of the other winding elements of the stack can be adjacent to two winding elements of the stack.

[0014] Preferably, the capacitor does not include any other wound elements in addition to the wound elements in the stack.

[0015] In some embodiments, the capacitor may include multiple stacks of at least winding elements, where in each stack, the polarity of the outermost winding element is reversed compared to the other winding elements. Each of the stacks m includes a first bus bar and a second bus bar, where in the stacking direction of each stack, the first bus bar is coupled to the top surface of the first winding element, the top surface of the last winding element, and the bottom surfaces of the other winding elements, and in the stacking direction of each stack, the second bus bar is coupled to the bottom surface of the first winding element, the bottom surface of the last winding element, and the top surfaces of the other winding elements. Preferably, the capacitor does not include any other winding elements in addition to the winding elements in the multiple stacks.

[0016] Because only the outermost winding element has an inverted polarity compared to each adjacent winding element, only the outermost winding element needs to be insulated from the adjacent winding elements, for example by providing an insulating sheet. Compared to a reference capacitor in which each winding element has the opposite polarity to its adjacent winding element, the number of insulators can be significantly reduced. The reduction in the number of insulators results in weight reduction, reduced material costs, and a simplified manufacturing process.

[0017] The first winding element in the stacking direction of the stack and the last winding element in the stacking direction of the stack may have the same polarity, and the other winding elements may have a polarity opposite to that of the first winding element.

[0018] The first busbar and the second busbar can be arranged to overlap each other. In particular, the first busbar and the second busbar can be arranged so that at least 20% of the area of ​​the first busbar overlaps with the second busbar, preferably at least 50% of the area of ​​the first busbar overlaps with the second busbar. More preferably, at least 80% of the area of ​​the first busbar overlaps with the second busbar. In the overlapping area of ​​the busbars, a thin insulator can be arranged between the busbars to prevent short circuits between the busbars.

[0019] The first and second bus bars can be configured to have currents flowing in opposite directions through the bus bars. Due to the overlap of the bus bars, the magnetic field generated by the current flowing through the first bus bar is compensated for, or at least weakened, by the magnetic field generated by the current flowing through the second bus bar. The greater the overlap between the bus bars, the better the magnetic field weakening or cancellation. Magnetic field compensation can result in low inductance and uniform impedance for all winding elements. Both magnetic field compensation through bus bar overlap and magnetic field compensation through the opposite polarity of the outermost winding elements in the stack reduce the parasitic inductance of the capacitor, thereby providing a capacitor with very low ESL.

[0020] The first and second bus bars can be disposed on sides of the stack that are perpendicular to the top surfaces of the winding elements and perpendicular to the bottom surfaces of the winding elements. The sides of the stack may have a smaller surface area than the top surface of the stack formed by the top surfaces of the winding elements and a smaller surface area than the bottom surface of the stack formed by the bottom surfaces of the winding elements. By disposing the first and second bus bars on the sides of the stack, the bus bars are disposed on a surface that has a relatively small area, thereby reducing the amount of material required for the bus bars. The bus bars may comprise or be made of copper. Reducing the amount of material for the bus bars can reduce the weight and material costs of the capacitor.

[0021] A first insulating sheet may separate the first winding element from the other winding elements in the stack, and a second insulating sheet may separate the last winding element from the other winding elements in the stack. No insulating sheets may be disposed between the other winding elements in the stack. Further, no resin may be disposed between the winding elements in the stack.

[0022] Therefore, insulating sheets may be placed only between pairs of winding elements having opposite polarities. Regardless of the number of winding elements in the stack, only two insulating sheets are required because only the outermost pairs of adjacent winding elements have winding elements with opposite polarities. Reducing the number of insulating sheets in a capacitor can reduce the material requirements and cost of the capacitor.

[0023] The first busbar may include a first portion and a second portion. The first portion may be connected to the top surface of the first winding element and the top surface of the last winding element. The second portion may be connected to the bottom surface of the other winding elements. The two portions of the first busbar may be fixed to each other by, for example, laser welding. The second busbar may have only a single portion. [Brief explanation of the drawings]

[0024] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. [Figure 1] FIG. 1 shows a perspective view of a capacitor. [Figure 2] FIG. 1 shows a perspective view of a capacitor. [Figure 3] The capacitor part is shown. [Figure 4] The simulation results of the ESL of the capacitor shown in FIG. 3 and the reference capacitor are shown. DETAILED DESCRIPTION OF THE INVENTION

[0025] Figures 1 and 2 show perspective views of a capacitor, with Figure 1 showing the bottom surface of the capacitor and Figure 2 showing the top surface of the capacitor.

[0026] The capacitor includes multiple winding elements 1 to 6 arranged in a stack. Each of the winding elements 1 to 6 includes a bottom surface 1a to 6a and a top surface 1b to 6b. The top surfaces 1a to 6a and the bottom surfaces 1b to 6b face each other, and the winding axis of each of the winding elements 1 to 6 is perpendicular to the top surfaces 1a to 6a and the bottom surfaces 1b to 6b.

[0027] The winding elements 1-6 are arranged in the stack such that each of their top surfaces 1b-6b faces in the same direction. In particular, the surface normal of each of the top surfaces 1b-6b is perpendicular to the stacking direction S of the stack. Furthermore, the bottom surfaces 1a-6a of each of the winding elements face in the same direction, and the surface normal of the bottom surfaces 1a-6a is perpendicular to the stacking direction S and opposite to the surface normal of the top surfaces 1a-5a.

[0028] In the embodiment shown in Figures 1 and 2, the capacitor includes six winding elements 1-6. For purposes of illustration, two of the six winding elements 1-6 are not shown in Figure 2. The capacitor may also include four, five, or any number greater than six winding elements.

[0029] The capacitor includes a first bus bar 7 and a second bus bar 8 .

[0030] The first busbar 7 and the second busbar 8 are arranged on the side surfaces of the stack. The side surfaces connect the top surface of the stack, formed by the top surfaces 1b-6b of the winding elements 1-6, to the bottom surface of the stack, formed by the bottom surfaces 1a-6a of the winding elements 1-6. Each of the first busbar 7 and the second busbar 8 overlaps only a small portion of the top surface and the bottom surface of the stack. For example, each of the first busbar 7 and the second busbar 8 overlaps less than 10% of the surface of each of the top surface and the bottom surface of the stack. This arrangement of the busbars 7 and 8 allows the busbars 7 and 8 to be configured with a small surface so that the amount of material used for the busbars 7 and 8 can be kept reasonable, thereby reducing the weight of the capacitor.

[0031] The first busbar 7 can be connected to a first pole of an external circuit. The second busbar 8 can be connected to a second pole of an external circuit. The first busbar 7 and the second busbar 8 are configured so that currents of opposite polarity flow through the busbars 7, 8.

[0032] The first bus bar 7 and the second bus bar 8 each have one or more terminals (not shown). The bus bars 7 and 8 are configured to be connected to an external circuit via these terminals. An electrical signal can be applied to the terminals.

[0033] The first busbar 7 is connected to the top surface 1b of the first winding element 1 in the stacking direction S. The first busbar 7 has two connection pins 9 each connected to the top surface 1b of the first winding element 1.

[0034] The first busbar 7 is connected to the top surface 6b of the last winding element 6 in the stacking direction S. The first busbar 7 has two connection pins 9 each connected to the top surface 6b of the last winding element 6.

[0035] The first bus bar 7 is connected to the bottom surfaces 2a to 5a of all the winding elements 2 to 5 except for the bottom surface 1a of the first winding element 1 in the stacking direction S and the bottom surface 6a of the last winding element 6. The first bus bar 7 is connected to each of the bottom surfaces of the winding elements 2 to 5 via two connection pins 9.

[0036] The second busbar 8 is connected to the top surface 1a of the first winding element 1 in the stacking direction S. The second busbar 8 has two connection pins 9 each connected to the bottom surface 1a of the first winding element 1.

[0037] The second busbar 8 is connected to the bottom surface 6a of the last winding element 6 in the stacking direction S. The second busbar 8 has two connection pins 9 connected to the bottom surface 6a of the last winding element 6.

[0038] The second busbar 8 is connected to the top surfaces 2b to 5b of all winding elements 2 to 5 except for the top surfaces 1b, 6b of the first and last winding elements 1, 6 in the stacking direction S. For each of the winding elements 2 to 5, except for the first winding element 1 and the last winding element 6 in the stacking direction S, the second busbar 8 has two connection elements 9 connected to the respective top surfaces 2b to 5b.

[0039] Therefore, the first winding element 1 and the last winding element 6 have a polarity opposite to that of the other winding elements 2 to 5. That is, the outer winding elements 1, 6 of the stack have a polarity opposite to that of the other winding elements 2 to 5.

[0040] The polarities of the winding elements 1 to 6 alternate along the stacking direction S from the first winding element 1 to the next adjacent winding element 2 and again from the penultimate winding element 5 to the last winding element 6. In the intermediate part of the stack formed between the second winding element 2 and the penultimate winding element 5, the polarities of the winding elements 2 to 5 do not alternate along the stacking direction S.

[0041] The alternating polarity of the outermost winding elements 1, 6 compensates for the magnetic flux generated by one of the outermost winding elements 1, 6 and each of its adjacent winding elements 2, 5. The magnetic flux of other winding element pairs in the middle of the stack is not compensated for. However, the polarity changes between the outermost winding elements 1, 6 and each of their adjacent winding elements 2, 5 result in opposite AC currents flowing at each point on the busbars 7, 8, significantly reducing the inductance in the "supply lines" to the winding elements. The inductance of each individual winding element 1-6 may already be very low. With the current parallel connection of winding elements 1-6, this value becomes less significant because it is divided by the number of winding elements.

[0042] Overall, this results in a capacitor with very low parasitic inductance. By reducing the parasitic inductance, the impedance from the terminals to each winding element 1-6 becomes more uniform between winding elements 1-6 for each frequency in the bandwidth over which the capacitor operates. This results in a low and uniform ESL from each terminal pair 8.

[0043] As described above, the first busbar 7 and the second busbar 8 overlap each other. Current flowing through the first busbar 7 generates a first magnetic field, and current flowing through the second busbar 8 generates a second magnetic field. By overlapping the two busbars 7 and 8, the first magnetic field and the second magnetic field are mutually compensated for. The magnetic field compensation results in low inductance and uniform impedance for all winding elements 1 to 6.

[0044] The inductance of the magnetic field emerging from adjacent winding elements 2-5 of the same polarity is compensated by the reduced inductance of the overlapping busbars 7, 8. The combination of overlapping busbars 7, 8 with opposite polarity and the stack of outermost winding elements 1, 6 having opposite polarity compared to the other winding elements 2-5 results in a very good reduction of the magnetic flux and thereby a low ESL.

[0045] The first busbar includes a first portion 7a and a second portion 7b. Each portion 7a, 7b is formed from a metal sheet. The first portion 7a of the first busbar 7 is connected to the top surfaces 1b, 6b of the first and last winding elements 1, 6. The second portion 7b of the first busbar 7 is connected to the bottom surfaces 2b-5b of the other winding elements 2-5. The second portion 7b comprises a terminal of the first busbar 7. The first portion 7a and the second portion 7b are permanently fixed to each other, for example, by laser welding.

[0046] An insulator is disposed between the first bus bar 7 and the second bus bar 8 to prevent a short circuit between the two bus bars.

[0047] Figure 3 shows a portion of a capacitor including five winding elements 1-3, 5, and 6. The capacitor of Figure 3 differs from the capacitor shown in Figures 1 and 2 only in the number of winding elements. For simplicity, the five winding elements are referenced as 1-3, 5, and 6, such that winding element 4 is omitted compared to the capacitor of Figures 1 and 2.

[0048] In particular, five winding elements 1 to 3, 5, 6 of the stack, a first insulating sheet 10 and a second insulating sheet 11 are shown in FIG.

[0049] The first insulating sheet 10 is arranged between the first winding element 1 and the second winding element 2 in the stacking direction S. The second insulating sheet 11 is arranged between the last winding element 6 and the penultimate winding element 5 in the stacking direction S.

[0050] Therefore, insulating sheets 10, 11 are arranged between each pair of winding elements 1-2 and 5-6 having opposite polarities. Insulating sheets 10, 11 are not arranged between winding elements 1-3 and 5 having the same polarity. Compared to a capacitor in which each winding element has an opposite polarity to the adjacent winding element, the number of insulating sheets can be reduced, thereby reducing the weight and cost of the capacitor.

[0051] While the capacitor design shown in Figures 1-3 requires only two insulating sheets 10, 11 for any stack of winding elements, a capacitor with n winding elements with opposite polarity between each pair of adjacent winding elements would require n-1 insulating sheets for a stack of n winding elements. In the capacitors shown in Figures 1-3, the number of insulating sheets is always two for any number of n winding elements in the stack.

[0052] Figure 4 shows the ESL simulation results for the capacitor shown in Figure 3 and the reference capacitor. The first curve C1 shows the ESL for a pair of terminals of the capacitor shown in Figure 3. The second curve C2 shows the ESL for a pair of terminals of the reference capacitor, where all winding elements have the same polarity. Compared to the reference capacitor, the ESL is reduced by approximately 6 nH. Thus, changing the polarity of the outermost winding elements 1 and 5 significantly reduces the ESL while at the same time only requiring two additional insulating sheets 10 and 11, resulting in a modest increase in weight and cost. These insulating sheets 10 and 11 are placed between each pair of winding elements 1-2 and 5-6 with opposite polarities. [Explanation of symbols]

[0053] 1 Wire-wound element 1a Bottom 1b Top side 2-winding element 2a Bottom 2b Top side 3-winding element 3a Bottom 3b Top side 4-winding element 4a Bottom 4b Top surface 5 winding element 5a Bottom 5b Top side 6 winding elements 6a Bottom 6b Top side 7 No. 1 bus bar 7a Part 1 7b Part 2 8 Second bus bar 9 connecting pins 10 First insulating sheet 11 Second insulating sheet S Stacking direction

Claims

1. A capacitor, at least four winding elements arranged in a stack, each winding element having a top surface and a bottom surface; A first bus bar; A second bus bar; In a stacking direction of the stack, the first bus bar is coupled to a top surface of a first winding element, a top surface of a last winding element, and a bottom surface of another winding element; A capacitor, wherein in a stacking direction of the stack, the second bus bar is coupled to a bottom surface of the first winding element, a bottom surface of the last winding element, and a top surface of the other winding element.

2. The capacitor of claim 1 , wherein the winding elements are arranged in the stack such that a surface normal to a top surface of each winding element is perpendicular to the stacking direction.

3. 3. The capacitor according to claim 1, wherein the first winding element in the stacking direction of the stack and the last winding element in the stacking direction of the stack have the same polarity, and the other winding elements have polarities opposite to the polarity of the first winding element.

4. 4. The capacitor according to claim 1, wherein the first bus bar and the second bus bar are arranged to overlap each other.

5. 5. The capacitor of claim 4, wherein the first bus bar and the second bus bar are arranged so that at least 20% of the area of ​​the first bus bar overlaps with the second bus bar, preferably so that at least 50% of the area of ​​the first bus bar overlaps with the second bus bar.

6. 6. The capacitor of claim 1, wherein the first bus bar and the second bus bar are arranged on a side of the stack that is perpendicular to a top surface of the winding element and perpendicular to a bottom surface of the winding element.

7. 7. The capacitor of claim 1, wherein a first insulating sheet separates the first winding element from the other winding elements in the stack, a second insulating sheet separates the last winding element from the other winding elements in the stack, and no insulating sheet is disposed between the other winding elements.

8. 8. The capacitor of claim 1, wherein the first bus bar includes a first portion and a second portion, the first portion being connected to a top surface of the first winding element in the stacking direction and a top surface of the last winding element in the stacking direction, and the second portion being connected to a bottom surface of the other winding elements.

9. The capacitor of claim 8 , wherein the first portion of the first bus bar and the second portion of the first bus bar are fixed to one another.

10. The capacitor according to any one of claims 1 to 9, wherein the second bus bar is made of a single part.

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