Capacitor, in particular intermediate circuit capacitor for a multiphase system

Abstract

For a capacitor (1), in particular an intermediate circuit capacitor for a multiphase system, comprising a first surface electrode (11) and a second surface electrode (12) opposite it at a first distance (d1), and comprising at least one capacitor structure (20) having at least one dielectric arranged between the first surface electrode (11) and the second surface electrode (12), wherein a conductor surface section (13) adjoins the first surface electrode (11), which is angled at an edge (11a) of the first surface electrode (11) in the direction of the second surface electrode (12) and at least partially covers a first side wall (21) of the capacitor structure (20),with at least one first terminal (31) for electrically contacting the first surface electrode (11) and with a second terminal (32) parallel to the first terminal (31) and separated by a second gap (d2) for electrically contacting the second surface electrode (12), wherein the first terminal (31) projects outwards at an end of the conductor surface section (13) that is directed away from the first surface electrode (11), it is proposed that the capacitor (1) has at least one electrically conductive shielding element (14) fixed to the capacitor (1), wherein the electrically conductive shielding element (14) covers a second side wall (22) of the capacitor structure (20) perpendicular to the first surface electrode (11) and the second surface electrode (12) and to the conductor surface section (13).

Description

State of the art

[0001] The invention relates to a capacitor, in particular an intermediate circuit capacitor for a multiphase system, with the features of the preamble of independent claim 1.

[0002] Such a capacitor is known, for example, from DE 10 2015 216 771 A1. Inverters for electrical machines often use power electronics in which electrical capacitors are arranged in an intermediate circuit of an electrical network coupled to a B6 bridge and an electrical machine.

[0003] The use of capacitors in the DC link counteracts parasitic inductances. Such parasitic inductances are generated, for example, by the electrical conductors between an electrical power source and the electrical loads connected to it. In the operation of a multiphase electrical system consisting of an electrical power source, a B6 bridge with a connected electric machine, and an electrical network connecting the power source to the B6 bridge, adverse voltage fluctuations, known as voltage ripple, can occur. The design and dimensioning of capacitors connected in the DC link significantly influence the intensity of the voltage ripple occurring on the electrical interconnection lines. Disclosure of the invention

[0004] The present invention relates to a capacitor, in particular an intermediate circuit capacitor for a multiphase system, comprising a first surface electrode and a second surface electrode opposite it at a first distance, and comprising at least one capacitor structure having at least one dielectric arranged between the first surface electrode and the second surface electrode, wherein a conductor surface section adjoins the first surface electrode, which is angled at an edge of the first surface electrode towards the second surface electrode and covers a first side wall of the capacitor structure, comprising at least one first terminal for electrically contacting the first surface electrode and a second terminal parallel to the first terminal and separated by a second distance for electrically contacting the second surface electrode.wherein the first terminal projects outwards at an end of the conductor surface section that is directed away from the first surface electrode. According to the invention, the capacitor has at least one electrically conductive shielding element fixed to the capacitor, wherein the electrically conductive shielding element covers a second side wall of the capacitor structure that is perpendicular to the first surface electrode, the second surface electrode and the conductor surface section.

[0005] In the context of this application, a capacitor structure is understood to be a structure that, together with the first and second surface electrodes, can form a capacitor, or that itself forms a capacitor. The capacitor structure may, for example, be a dielectric, such that the first surface electrode, together with the second surface electrode and the dielectric arranged between the first and second surface electrodes, form a capacitor. However, the capacitor structure may also consist of one or more capacitors arranged between the first and second surface electrodes, which, depending on the intended use, may be connected in parallel or in series.

[0006] In the context of this application, a surface electrode is understood to be a conducting structure extending in a plane, made of, for example, a metal, which rests on the capacitor structure and is electrically connected to a terminal of the capacitor. The surface electrodes can completely or partially cover the opposing contact surfaces of the capacitor structure. The surface electrodes can be continuous across the surface or have one or more recesses. If the capacitor structure consists of a group of individual capacitors, each individual capacitor is electrically contacted by the surface electrodes. It is not necessary for the surface electrodes to completely cover the capacitor structure.

[0007] In the context of this application, an electrically conductive shielding element is understood to be a component of any shape made of electrically conductive material, which covers the second side wall in such a way as to achieve electromagnetic shielding. The electrically conductive shielding element can, for example, be plate-shaped and cover the second side wall completely or partially. However, it is also possible for the electrically conductive shielding element to be designed, for example, as a grid, in such a way as to achieve electromagnetic shielding. Advantages of the invention

[0008] The capacitor presented here uses at least one electrically conductive shielding element to shield an otherwise unshielded side wall of the capacitor structure. This at least one electrically conductive shielding element causes an advantageous change in the specific impedance characteristic of the capacitor. The resulting electromagnetic shielding reduces the impedance of the capacitor across the frequency range, and the capacitor becomes lower-resistance for certain frequency components. This results in a beneficial reduction of the voltage ripple. This advantage is achieved simply by a special arrangement of an electrically conductive shielding element on the capacitor. This advantageously avoids the need to increase the capacitance value, which would otherwise be required to reduce the voltage ripple by increasing the size of the capacitor.

[0009] Reduced voltage ripple leads to lower electrical losses, which in turn has a positive effect on thermal losses. Lower thermal losses mean less cooling surface area and thus a saving of installation space or the implementation of alternative cooling concepts that would otherwise be necessary to dissipate the heat generated by the condenser, resulting in further space savings. Furthermore, lower electrical losses increase electrical efficiency.

[0010] Another advantage lies in the extended lifespan. A smaller voltage ripple means less stress on the capacitor, which, as already explained, leads to a reduction in power loss. Both of these characteristics directly affect the reliability and thus the lifespan of the capacitor.

[0011] Advantageous embodiments and further developments of the invention enable the features contained in the dependent claims.

[0012] By integrally connecting at least one electrically conductive shielding element to the first or second surface electrode, simplified assembly of the shielding element is advantageously achieved, as the shielding element is installed on the capacitor together with a surface electrode. For this purpose, for example, the at least one electrically conductive shielding element can run parallel to the second side wall and be spaced from the second side wall of the capacitor structure by a third distance.

[0013] However, it is also possible that at least one electrically conductive shielding element is manufactured as a separate component and is applied directly to the second side wall, independent of the surface electrodes.

[0014] The at least one electrically conductive shielding element can be designed in a simple way as a plate-shaped component, preferably made of metal.

[0015] In a particularly advantageous embodiment, a first electrically conductive shielding element covers the second side wall, and a second electrically conductive shielding element covers a third side wall of the capacitor structure facing away from the second side wall. The first electrically conductive shielding element and the second electrically conductive shielding element can, for example, be two identically constructed, parallel plates that enclose the capacitor structure on opposite sides.

[0016] The first electrically conductive shielding element can partially or, in particular, completely cover the second side wall. Alternatively or additionally, the second electrically conductive shielding element can partially or, in particular, completely cover the third side wall.

[0017] In one embodiment, the first surface electrode and / or the second surface electrode can project beyond the second side wall by an overhang, and the at least one electrically conductive shielding element at the end of the overhang can be angled perpendicularly from the first and / or second surface electrode. This makes it very easy to ensure that the respective shielding element is positioned at a distance from one side wall.

[0018] In a further advantageous embodiment, a first electrically conductive shielding element is angled away from the first surface electrode, and a third electrically conductive shielding element is angled away from the second surface electrode, wherein the first and third electrically conductive shielding elements overlap without electrical contact at the second side wall. Alternatively or additionally, a second electrically conductive shielding element can be angled away from the first surface electrode, and a fourth electrically conductive shielding element can be angled away from the second surface electrode, wherein the second and fourth electrically conductive shielding elements overlap without electrical contact at the third side wall. The mutually overlapping shielding elements at the two opposite side walls result in particularly effective shielding in each case.

[0019] In a particularly inexpensive and simple manner, the first surface electrode together with the conductor surface section and the at least one electrically conductive shielding element can be designed as a metallic stamped and bent part.

[0020] It is particularly worth mentioning that all the aforementioned advantages have a direct positive impact on costs. Brief description of the drawings Fig. Figure 1 shows a schematic representation of a first embodiment of a capacitor according to the invention, Fig. Figure 2 shows a schematic representation of a capacitor structure, which is located in the Fig. The capacitor shown in section 1 is included. Fig. Figure 3 shows a schematic representation of a second embodiment of a capacitor according to the invention, Fig. Figure 4 shows a simplified cross-section through a third embodiment of a capacitor according to the invention. Fig. Figure 5 shows in the upper part an impedance curve for a capacitor without electrically conductive shielding elements, in the middle part an associated spectral composition of the voltage ripple, and in the lower part the time course of the voltage ripple occurring in a selected time range. Fig. Figure 6 shows in the upper part an impedance curve for a capacitor according to the invention, in the middle part an associated spectral composition of the voltage ripple and in the lower part the time course of the voltage ripple occurring in a selected time range. Embodiments of the invention

[0021] Fig. 1 and Fig. Figure 2 shows a schematic representation of a first embodiment of a capacitor 1 according to the invention, comprising a capacitor structure 20. The illustrated capacitor 1 includes a first surface electrode 11 and a second surface electrode 12 opposite it at a first distance d1. The first surface electrode 11 and the second surface electrode 12 each extend in a plane and preferably run parallel to each other. In the embodiment shown here, the first surface electrode 11 and the second surface electrode 12 are preferably formed with a rectangular plate contour. Alternatively, the first surface electrode and / or the second surface electrode can also be formed by a planar electrode structure that only partially covers the capacitor structure 20 and that may have one or more recesses.A capacitor structure 20 is inserted between the first surface electrode 11 and the second surface electrode 12.

[0022] The capacitor structure 20 is in Fig. Figure 2 shows a substantially cuboid body with a flat base 26, a flat top 25 facing away from the base 26, a first side wall 21 and a fourth side wall 24 facing away from the first side wall, as well as a second side wall 22 and a third side wall 23 facing away from the second side wall, wherein the second side wall 22 and the third side wall 23 extend perpendicular to the base 26, the top 25 and the first side wall 21 and fourth side wall 24, and the first side wall 21 and fourth side wall 24 extend perpendicular to the base 26, the top 25 and the second side wall 22 and third side wall 23. The capacitor structure 20 can, for example, be a dielectric such that the first surface electrode 11 together with the second surface electrode 12 and the dielectric arranged between the first surface electrode 11 and the second surface electrode 12 form the capacitor 1.The capacitor structure 20 can also consist of one or more individual capacitors arranged between the first surface electrode 11 and the second surface electrode 12, which can be connected in parallel or in series depending on the application. Various capacitor technologies, such as stacked or circular-wound capacitors, can be used as individual capacitors. These can, for example, be electrically connected to the first surface electrode 11 and the second surface electrode 12.

[0023] The first surface electrode 11 is arranged on the top surface 25 of the capacitor structure 20. The second surface electrode 12 is arranged on the opposite base surface 26. The in Fig. 1 and Fig. The embodiment of the capacitor 1 according to the invention shown in Figure 2 further comprises a conductor section 13 adjoining the first surface electrode 11, which is angled at a right angle at an edge 11a of the first surface electrode 11 towards the second surface electrode 12 and at least partially covers the first side wall 21 of the capacitor structure 20. In the embodiment shown here, the conductor section 13 almost completely covers the first side wall 21. A first terminal 31 for electrically contacting the first surface electrode 11 is connected to the conductor section 13. The first terminal 31 is angled outwards at a right angle at one end of the conductor section 13 that is adjacent to the second surface electrode 12.In other words: the first pole terminal 31 and the first surface electrode 11 are alternately angled away from the conductor surface section 13 at opposite ends of the conductor surface section 13. As in . Fig. As shown in Figure 1, the second terminal 32 can, for example, extend beyond the plane of the second surface electrode 12. The second terminal 32 is electrically connected to the second surface electrode 12. In the exemplary embodiment of Figure 1, the second terminal 32 runs along the plane of the second surface electrode 12. Fig. 1, for example, parallel to the first pole terminal 11 and is separated from it by a distance d2. In deviation from the embodiment of the Fig. 1. It is also possible that the conductor surface section 13 does not extend completely, but only over a part of the first side wall 21, and that a further conductor surface section, angled away from the second surface electrode 12, is also connected to it. The second pole connection 32 is then again angled outwards from the second conductor surface section, so that a mirror-symmetrical structure can be created, which is, for example, mirror-symmetrical with respect to an imaginary plane that runs through the gap between the first pole connection 31 and the second pole connection 32.

[0024] The first surface electrode 11 with the adjoining conductor surface section 13 and the first terminal 31, as well as the second surface electrode 12 with the second terminal 32, are preferably made of electrically conductive material such as metal. The first surface electrode 11 and the second surface electrode 12 can be flat and, for example, made of sheet metal. The parallel gap formed by the second distance d2 between the first terminal 31 and the second terminal 32 can, for example, be filled with a conductor only in Fig. 3 shown, electrically insulating material 40 should be filled.

[0025] The capacitor 1 presented here further comprises at least one electrically conductive shielding element 14 fixed to the capacitor 1, wherein the electrically conductive shielding element 14 covers the second side wall 22 of the capacitor structure 20, which is perpendicular to the first surface electrode 11 and the second surface electrode 12 and to the conductor surface section 13 or the first side wall 21. Although a positive effect is already achieved with only one electrically conductive shielding element 14, it is particularly advantageous if, as in the embodiment of Fig. 1, two electrically conductive shielding elements 14a, 14b are attached to the capacitor 1. Fig. Figure 1 shows a first electrically conductive shielding element 14a, which, for example, completely covers the second side wall 22 of the capacitor structure 20. In combination with this, or independently of it, a second electrically conductive shielding element 14b can cover the third side wall 23 of the capacitor structure 20, which faces away from the second side wall 22. It is possible that the first electrically conductive shielding element 14a partially or completely covers the second side wall 22 and / or that the second electrically conductive shielding element 14b also partially or completely covers the third side wall 23. The first and second electrically conductive shielding elements 14a, 14b are made of electrically conductive material such as metal (for example, each from a separate piece of sheet metal) and are, for example, plate-shaped, but can also be designed as a grid or in another shape suitable for shielding.The first and second electrically conductive shielding elements 14a, 14b can, for example, be manufactured separately and adhere to the second side wall 22 and the third side wall 23, respectively.

[0026] Fig. Figure 3 shows a schematic representation of a second embodiment of the capacitor 1 according to the invention. A section of a perspective view of the capacitor 1 is shown. Fig. Figure 3 shows a first electrically conductive shielding element 14a, which is integrally connected to the first surface electrode 11. Alternatively, it is also possible to integrally connect the first electrically conductive shielding element 14a to the second surface electrode 12. As shown in Fig. As shown in Figure 3, in this embodiment the first surface electrode 11 projects beyond the second side wall 22 with a projection 15. The first electrically conductive shielding element 14a is angled perpendicularly at the end of the projection 15 towards the second surface electrode 12 and runs parallel to the second side wall 22, so that the first electrically conductive shielding element 14a is located opposite the second side wall 22 at a distance d3, and a gap exists between the second side wall 22 and the first electrically conductive shielding element 14a. This gap can be filled, for example, with an electrically insulating material, unlike the one shown. In this embodiment, the opposite third side wall 23 of the capacitor structure 20 can be covered analogously by a second electrically conductive shielding element 14b, which is located opposite the third side wall 23 at a distance.This distance can, for example, correspond to the distance d3.

[0027] Fig. Figure 4 shows a schematic representation of a third embodiment of the capacitor 1 according to the invention. Fig. 4 a cross-section through a capacitor 1. In this embodiment, a first electrically conductive shielding element 14a and a second electrically conductive shielding element 14b are angled perpendicularly at two opposite ends of the first surface electrode 11 in the direction of the second surface electrode 12, such that the first electrically conductive shielding element 14a partially or completely covers the second side wall 22 and the second electrically conductive shielding element 14b partially or completely covers the third side wall 23. In this respect, the structure is similar to that in Fig. 3 second embodiment shown. In contrast to the one in Fig. In the second embodiment shown in Figure 3, a third electrically conductive shielding element 14c and a fourth electrically conductive shielding element 14d are additionally angled perpendicularly at two opposite ends of the second surface electrode 12 in the direction of the first surface electrode 11, so that the third electrically conductive shielding element 14c partially or completely covers the first electrically conductive shielding element 14a without contact and the fourth electrically conductive shielding element 14d partially or completely covers the second electrically conductive shielding element 14b without contact.In particular, the third electrically conductive shielding element 14c can be located at a distance from the first electrically conductive shielding element 14a and the fourth electrically conductive shielding element 14d can be located at a distance from the second electrically conductive shielding element 14b, so that a labyrinthine structure is created which electromagnetically shields the second side wall 22 and the third side wall 23.

[0028] Fig. Figure 5 shows, for better understanding, an impedance curve for a capacitor in the upper part, as in Fig. 1 shown, but without the electrically conductive shielding elements 14. In the middle part of the Fig. Figure 5 shows a corresponding spectral composition of the voltage ripple and the lower part shows a time course of the voltage ripple occurring in a selected time range.

[0029] In the upper part of the Fig. Figure 1 shows the impedance curve with reference symbol 51 plotted against the frequency. This impedance curve 51 was calculated using a finite element method. The impedance is plotted on the right ordinate. Reference symbol 52 represents the distribution of the spectral current components, which was calculated from a simulation of a current waveform for a network consisting of an electric machine and a B6 bridge. The left ordinate in the upper part of Fig. 5 represents the current intensity of the spectral components.

[0030] The central section shows the distribution 54 of the spectral voltage components calculated from the spectral current components 52 and the impedance curve 51. The frequency is plotted on the ordinate and the voltage on the abscissa. Curve 55 describes the spectral voltage components summed over a frequency band between 1 kHz and 200 kHz.

[0031] By transforming the spectral voltage components into the time domain, a time course 53 of the voltage ripple is obtained, which in the lower part of the Fig. Figure 5 is shown. The ordinate of the lower diagram represents the voltage, and the abscissa represents time.

[0032] The same representations are in Fig. 6 for a capacitor 1 with the electrically conductive shielding elements 14a, 14b, as in Fig. Figure 1 represents the impedance curve. Here, too, the impedance curve with reference symbol 61 is plotted against the frequency. This impedance curve 61 was calculated using a finite element method for capacitor 1 with the conductive shielding elements 14a and 14b. The impedance is plotted on the right ordinate. Reference symbol 62 represents the distribution of the spectral current components, which was calculated from a simulation of a current waveform for a network consisting of an electric machine and a B6 bridge. The left ordinate in the upper part of Fig. 6 represents the current intensity of the spectral components.

[0033] The middle section also shows the distribution 64 of the spectral voltage components calculated from the spectral current components 62 and the impedance curve 61. The frequency is plotted on the ordinate and the voltage on the abscissa. Curve 65 again describes the spectral voltage components summed over a frequency band between 1 kHz and 200 kHz.

[0034] Here too, transforming the spectral voltage components into the time domain yields a time course 63 of the voltage ripple, which is in the lower part of the Fig. Figure 6 is shown. The ordinate of the lower diagram represents the voltage, and the abscissa represents time.

[0035] From the comparison of the lower part of Fig. 5 and Fig. Figure 6 clearly shows a reduction in voltage ripple of approximately 30% compared to the results obtained in Fig. 5, which serve as a reference.

[0036] It follows that the additional arrangement of the electrically conductive shielding elements 14a and 14b on the second side wall 22 and the third side wall 23 of the capacitor structure 20, through their influence on the electromagnetic shielding effect of the capacitor 1 used as an intermediate circuit capacitor, leads to a significant reduction in the impedance curve. This results in a significant and advantageous reduction of the resulting voltage ripple 63.

[0037] The positive effect would also occur in a weakened form with only one electrically conductive shielding element 14. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2015 216 771 A1

[0002]

Claims

[1] Capacitor (1), in particular intermediate circuit capacitor for a multiphase system, comprising a first surface electrode (11) and a second surface electrode (12) opposite it at a first distance (d1) and comprising at least one capacitor structure (20) having at least one dielectric arranged between the first surface electrode (11) and the second surface electrode (12), wherein a conductor surface section (13) adjoins the first surface electrode (11), which is angled at an edge (11a) of the first surface electrode (11) in the direction of the second surface electrode (12) and at least partially covers a first side wall (21) of the capacitor structure (20),with at least one first pole connection (31) for electrical contacting the first surface electrode (11) and with a second pole connection (32) parallel to the first pole connection (31) and separated by a second distance (d2) for electrical contacting the second surface electrode (12), wherein the first pole connection (31) projects outwards at an end of the conductor surface section (13) that is directed away from the first surface electrode (11), , characterized by , that the capacitor (1) has at least one electrically conductive shielding element (14) fixed to the capacitor (1), wherein the electrically conductive shielding element (14) covers a second side wall (22) of the capacitor structure (20) perpendicular to the first surface electrode (11) and the second surface electrode (12) and to the conductor surface section (13). [2] Capacitor (1) according to claim 1, characterized by, that at least one electrically conductive shielding element (14) is integrally connected to the first surface electrode (11) or the second surface electrode (12). [3] Capacitor (1) according to claim 1 or 2, characterized by , that at least one electrically conductive shielding element (14) runs parallel to the second side wall (22) and is spaced apart from the second side wall (22) of the capacitor structure (20) by a third distance (d3). [4] Capacitor (1) according to claim 1, characterized by , that at least one electrically conductive shielding element (14) is applied as a separate component to the second side wall (22). [5] Capacitor (1) according to at least one of the preceding claims, characterized by , that at least one electrically conductive shielding element (14) is designed in the shape of a plate. [6] Capacitor (1) according to at least one of the preceding claims, characterized by, that a first electrically conductive shielding element (14a) covers the second side wall (22) and a second electrically conductive shielding element (14b) covers a third side wall (23) of the capacitor structure (20) facing away from the second side wall (22). [7] Capacitor (1) according to claim 6, characterized by , that the first electrically conductive shielding element (14a) completely covers the second side wall (22) and / or the second electrically conductive shielding element (14b) completely covers the third side wall (23). [8] Capacitor (1) according to claim 3, characterized by , that the first surface electrode (11) and / or the second surface electrode (12) extends beyond the second side wall (22) by a projection (15) and that at least one electrically conductive shielding element (14) is angled perpendicularly at the end of the projection (15). [9] Capacitor (1) according to claim 2 or 3, characterized by, that a first electrically conductive shielding element (14a) is angled from the first surface electrode (11) and a third electrically conductive shielding element (14c) is angled from the second surface electrode (12) and that the first electrically conductive shielding element (14a) and the third electrically conductive shielding element (14c) overlap electrically without contact at the second side wall (22) and / or a second electrically conductive shielding element (14b) is angled from the first surface electrode (11) and a fourth electrically conductive shielding element (14d) is angled from the second surface electrode (12) and that the second electrically conductive shielding element (14a) and the fourth electrically conductive shielding element (14c) overlap electrically without contact at the third side wall (23). [10] Capacitor (1) according to claim 2 or 3, characterized by, that the first surface electrode (11) together with the conductor surface section (13) and the at least one electrically conductive shielding element (14) is designed as a metallic stamped and bent part.

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