Power electronics device with optimized current density distribution by means of a coplanar busbar arrangement; and electric machine

Abstract

The invention relates to a power electronics device (1) for an electric machine (2), comprising several power modules (3) and several busbars (4a, 4b, 4c) connected to the power modules (3), each forming a phase and prepared for connection to the electric machine (2), wherein the busbars (4a, 4b, 4c) are arranged coplanar to each other at least with their first busbar sections (5a, 5b, 5c) adjacent to the power modules (3) and / or the busbars (4a, 4b, 4c) have second busbar sections (6a, 6b, 6c) which run parallel to each other and are arranged one above the other.

Description

[0001] The invention relates to a power electronics device for an electrical machine, preferably an electric drive motor of a motor vehicle, comprising a plurality of power modules and a plurality of busbars connected to the power modules, each forming a phase (of the electrical machine) and prepared for connection to the electrical machine. Furthermore, the invention relates to an electrical machine comprising this power electronics device.

[0002] Known power electronics devices and electrical machines are already well known from the prior art. For example, DE 10 2021 110 983 A1 discloses a power electronics module for an electrical machine with a specially designed EMC filter device.

[0003] Power electronics devices are already known in which individual components are connected to one another via busbars. In particular on the AC side of the power electronics device, current sensors are often connected to the power modules via the busbars designed as conductors. Individual busbar sections are often arranged in parallel. It has been found that, particularly on the AC busbar side, an alternating current causes the conductor cross-section to contribute more to current conduction at the edges due to current displacement. The current density is therefore significantly lower in the middle region of the conductor than at the edges. The consequence is that the busbar heats up more with the same cross-section, or alternatively, the cross-section of the busbar must even be increased.

[0004] It is therefore an object of the present invention to provide a power electronics device which allows a higher current density, particularly on the AC side, with constant conductor cross-sections.

[0005] This is achieved according to the invention in that the busbars are arranged / run coplanar to one another at least with their first rail sections adjacent to the power modules and / or the busbars have second rail sections which run parallel to one another and are arranged one above the other.

[0006] With this arrangement of the first rail sections and / or the second rail sections, it has been found that a significantly more homogeneous current distribution occurs within the busbar. This reduces the current displacement effect in particular, so that the impedance of the busbar decreases significantly at higher frequencies. Overall, this in turn significantly reduces the heating of the busbar, so that the cross-section of the busbar can even be reduced if necessary.

[0007] Further advantageous embodiments are claimed in the subclaims and explained in more detail below.

[0008] Accordingly, it is further advantageous if the respective second rail section preferably connects to the respective first rail section via a step.

[0009] It is also advantageous to incorporate electrical insulation layers and / or metallic shielding layers between the first rail sections and / or between the second rail sections. This results in efficient power transmission in the most compact installation space possible.

[0010] For ease of production, it has also proven advantageous if the second rail sections with the insulation layers and / or the shielding layers are formed as a laminated structure. The insulation layers, preferably made of plastic material, can thus be easily pressed together with the rail sections and metallic shielding layers, preferably made of metal, in a material-to-metal and form-fitting manner.

[0011] As an alternative to the connection as a laminated structure, it is also expedient if the second rail sections form a cast-shaped structure with the insulation layers and / or the shielding layers, wherein the insulation layers are introduced between the second busbar sections and / or the shielding layers by a casting process (primary forming process).

[0012] It has also proven advantageous to arrange a thermally conductive layer, preferably a TIM layer, particularly preferably a gap pad, between one of the busbars and a housing of the power electronics device. This allows the heat generated during operation to be dissipated as effectively as possible.

[0013] Furthermore, it is advantageous if a current sensor is arranged on at least two first rail sections (or more preferably on three rail sections).

[0014] If shielding walls are arranged between the current sensors / the first rail sections with the current sensors, the measuring accuracy of the current sensors is further increased.

[0015] If the busbars, preferably in their second rail section, are (entirely) surrounded by a magnetic core, a filter function is cleverly implemented. Preferably, the three second rail sections are surrounded by a single ring-shaped / O-shaped (or oval or rectangular) core.

[0016] Furthermore, the invention relates to an electrical machine having a stator, a rotor and a power electronics device connected to a coil arrangement of the stator or the rotor according to at least one of the previously described embodiments, wherein each first rail section is directly connected to a power module and a plurality of second rail sections of the power electronics device are each connected to a phase connection of the coil arrangement.

[0017] The invention will now be explained in more detail with reference to the figures. They show: Fig. 1 a sectional view of a power electronics device according to the invention according to a preferred embodiment in the region of a busbar arrangement comprising three busbars, wherein the busbars are arranged coplanar to one another at least in a first rail section accommodating a current sensor, Fig. 2 a plan view of the busbar arrangement according to Fig. 1, Fig. 3 a perspective view of a power electronics device with the housing partially hidden, illustrating its further structure, and Fig. 4 is a schematic longitudinal section of an electrical machine equipped with the power electronics device of the Fig. 1 is coupled.

[0018] The figures are merely schematic and serve solely to clarify the invention. The same elements are designated by the same reference numerals.

[0019] In connection with the Fig. 3 and Fig. 4, reference should first be made to the preferred field of application of the power electronics device 1 according to the invention. The power electronics device 1 is preferably part of an electrical machine 2, i.e., connected to an electrical machine 2. The electrical machine 2 is preferably used as the drive motor of a (more preferably purely battery-electrically powered) motor vehicle.

[0020] In Fig. 4 also shows that the power electronics device 1 is electrically connected by its output-side (here three) terminals 18 / outputs to (here three) phase terminals 16a, 16b, 16c of the electric machine 2, namely a coil arrangement 15 of the electric machine 2. In this embodiment, the coil arrangement 15 is formed as part of a stator 14, but can alternatively also be part of a rotor 19 of the electric machine 2. It should also be noted that, although three phases / phase terminals 16a, 16b, 16c are present in this embodiment, this number can, in principle, also vary. Thus, the subject matter of the invention is not limited to three-phase systems, but also encompasses other multi-phase systems.

[0021] A basic structure of the power electronics device 1 according to the invention is shown in Fig. 3. A housing 9 of the power electronics device 1 is illustrated only in half (namely, its lower half as viewed in the installed position), so that the structure inside the housing 9 can be seen in particular.

[0022] With Fig. 3, connected power modules 3 can be seen starting from the output-side connections 18. Each output-side connection 18 is electrically connected to a power module 3. A capacitor module 20 (DC link capacitor module) is in turn connected upstream of the power modules 3. The power modules 3 are connected to (AC) outputs of the capacitor module 20. A (DC) input of the capacitor module 20 is connected to a current coupling 21, which current coupling 21 is in turn implemented by several rails. A DC current sensor 22 is in turn arranged on this current coupling 21. Furthermore, an EMC filter 23 is connected upstream of the capacitor module 20 and is directly connected to input-side connections of the power electronics device 1 (not shown in detail here).

[0023] According to the invention, an arrangement of several busbars 4a, 4b, 4c is now provided on an AC side, i.e. a side of the capacitor module 20 facing the electric machine 2 along a current transmission path when the electric machine 2 is driven ( Fig. 1 and Fig. 2). In this design, three busbars 4a, 4b, 4c are implemented. This arrangement of the busbars 4a, 4b, 4c is positioned between the respective power module 3 and the electric machine 2.

[0024] It can be seen that each busbar 4a, 4b, 4c has a first rail section 5a, 5b, 5c, which is connected to the power module 3. According to the invention, the first rail sections 5a, 5b, 5c of the busbars 4a, 4b, 4c run parallel to each other, i.e. lie in one plane, as can be seen when viewing the Fig. 1 and Fig. 2. Preferably, the busbars 4a, 4b, 4c in the region of the first rail sections 5a, 5b, 5c are covered both from above and from below by an insulating layer 7, as viewed in an intended installation position in the acting gravitational field.

[0025] It is according to Fig. 2 that the first rail sections 5a, 5b, 5c are arranged at a distance from one another when viewed in a plane.

[0026] Furthermore, it can be seen that a current sensor 11a, 11b, 11c is positioned on each of the parallel longitudinal sections of the first rail sections 5a, 5b, 5c. It should be noted that, in principle, it would also be sufficient to position a current sensor on only two of the three first rail sections 5a, 5b, 5c. The actual current sensor 11a, 11b, 11c is shown mounted on a printed circuit board 24 that accommodates it.

[0027] Viewed along the length of the busbars 4a, 4b, 4c, the current sensors 11a, 11b, 11c are arranged at the same height / axial height, but can be arranged at different heights. A shielding wall 12 is inserted transversely thereto, between the respective first rail sections 5a and 5b, and 5b and 5c. This shielding wall serves to shield the magnetic fields of the current sensors 11a, 11b, 11c from each other, thus improving the measurement accuracy of the current sensors 11a, 11b, 11c.

[0028] In the further extension, the busbars 4a, 4b, 4c each transition from their first rail section 5a, 5b, 5c into a second rail section 6a, 6b, 6c.

[0029] The first busbar 4a forms a flat plate, with both its first rail section 5a and its second rail section 6a lying in a common plane of extension.

[0030] On the side of the further, namely second and third, busbars 4b, 4c, a step 17 is provided between the first rail section 5b, 5c and the second rail section 6b, 6c. The step 17 is designed such that the second rail sections 6b, 6c of the second and third busbars 4b, 4c are arranged one above the other and below the second rail section 6a of the first busbar 4a. The three second rail sections 6a, 6b, 6c thus run parallel to each other and in different planes. In conjunction with Fig. 2 clearly shows that the three second rail sections 6a, 6b, and 6c overlap one another. It should also be noted that a step 17 is optional, especially if the current sensors 11a, 11b, and 11c are positioned at the same height. If the conductors / busbars 4a, 4b, and 4c run straight, no steps are created.

[0031] The Fig. Figure 2 also shows that insulation layers 7 are located between the respective second rail sections 6a, 6b, 6c. Metallic shielding layers are also present between the respective second rail sections 6a, 6b, 6c. Thus, two insulation layers 7 are arranged between each two second rail sections 6a, 6b, 6c arranged directly above one another, and a metallic shielding layer 8 is arranged between these two insulation layers 7. Finally, both the uppermost second rail section 6a and the lowermost second rail section 6c are covered by a metallic shielding layer and an insulation layer.

[0032] Preferably, the layered structure consisting of the busbars 4a, 4b, 4c in the region of the second busbar sections 6a, 6b, 6c with the shielding layers 8 and the insulation layers 7, preferably made of plastic, is implemented as a laminated structure, i.e., one bonded and joined by adhesive bonding and pressing. Alternatively, however, it is also possible to cast the insulation layers, which are preferably made of plastic, into the existing gaps between the shielding layers 8 and the second busbar sections 6a, 6b, 6c and, after they have cured, to create a cast structure.

[0033] With regard to the laminated structure, it has also proven advantageous if the current sensors 11a, 11b, 11c, together with the further structure of the busbars 4a, 4b, 4c and insulation layers 7, are also attached to the busbars 4a, 4b, 4c in a lamination step. Alternatively, the current sensors 11a, 11b, 11c can also be attached to the busbars 4a, 4b, 4c in other ways, for example by separate bonding, by screwing (e.g., using plastic screws), or clipping / positive locking.

[0034] Furthermore, Fig. 1 that the busbars 4a, 4b, 4c are preferably entirely surrounded in one region by an annular / O-shaped magnetic core 13. The core 13 is arranged here in the region of the second rail sections 6a, 6b, 6c.

[0035] In addition, Fig.1 shows that the second rail sections 6a, 6b, 6c finally penetrate the housing 9 and are further connected to the phase terminals 16a, 16b, 16c with their side arranged outside the housing 9.

[0036] It should also be noted that, towards the underside of the busbars 4a, 4b, 4c, a thermally conductive layer / conductive layer 10 is arranged between the housing 9 and the lowest (third) busbar 4c, which thermally connects the arrangement of the busbars 4a, 4b, 4c to the housing 9. The conductive layer can be designed as a TIM layer, for example as a gap pad.

[0037] In other words, the three conductor layers (busbars 4a, 4b, 4c on the side of their first rail sections 5a, 5b, 5c), which are connected to three phases on the power module 3 or on the electric machine 2, are arranged coplanar to one another.

[0038] There are insulation layers 7 between the individual conductor layers or phases.

[0039] One possible implementation could be that the conductor layers and insulation layers 7 are designed in the form of a laminated busbar (production of a laminated busbar: conductor layers and insulation layers are alternately stacked on top of each other and pressed together).

[0040] Another possible implementation would be to construct this structure as a “molded” / cast busbar (manufacturing: a molding material is located between the conductor layers as electrical insulation; material is introduced between the conductor layers by a transfer molding process).

[0041] An optimal thermal connection of the flat and planar busbar to the inverter housing (housing 9) is possible with a TIM.

[0042] A current sensor 11a, 11b, 11c is positioned on each of the conductor layers (busbars 4a, 4b, 4c on the side of their second rail sections 6a, 6b, 6c) to measure the phase currents. In principle, two current sensors would also be sufficient, since the current of the third phase can be calculated.

[0043] The substrate or circuit board 24 of the current sensor 11a, 11b, 11c is attached to the busbar (arrangement of the busbars 4a, 4b, 4c) by gluing, screwing with plastic screws, or clipping. The current sensors 11a, 11b, 11c are integrated directly onto the busbar and can be laminated or molded.

[0044] Optionally, metal layers (shielding layers 8) can be placed between the individual phases to shield the phases from each other (similar to a shielded cable from the inverter to the machine).

[0045] Optionally, shielding elements (shielding walls 12) are also integrated into the busbar between the individual current sensors 11a, 11b, 11c.

[0046] Optionally, a magnetic core 13 (usually a nanocrystalline core) can be integrated as an EMC measure at the output of the inverter in order to reduce the current edges towards the electrical machine 2.

[0047] The number of phases can be freely selected and is not limited to three phases. List of reference symbols 1 power electronics device 2 electric machine 3 Power module 4a first busbar 4b second busbar 4c third power rail 5a first rail section of the first conductor rail 5b first rail section of the second busbar 5c first rail section of the third conductor rail 6a second rail section of the first conductor rail 6b second rail section of the second busbar 6c second rail section of the third conductor rail 7 Insulation layer 8 Shielding layer 9 housings 10 thermal conductive layer 11a Current sensor of the first busbar 11b Current sensor of the second busbar 11c Current sensor of the third busbar 12 Shielding wall 13 core 14 Stator 15 Coil arrangement 16a first phase connection 16b second phase connection 16c third phase connection 17th level 18 output connection 19 Rotor 20 capacitor module 21 Power coupling 22 DC current sensor 23 EMC filters 24 circuit board QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2021 110 983 A1

[0002]

Claims

[1] Power electronics device (1) for an electrical machine (2), comprising a plurality of power modules (3) and a plurality of busbars (4a, 4b, 4c) connected to the power modules (3), each forming a phase and prepared for connection to the electrical machine (2), characterized by that the busbars (4a, 4b, 4c) are arranged coplanar to one another at least with their first rail sections (5a, 5b, 5c) adjacent to the power modules (3) and / or the busbars (4a, 4b, 4c) have second rail sections (6a, 6b, 6c) which run parallel to one another and are arranged one above the other. [2] Power electronics device (1) according to claim 1, characterized by that electrical insulation layers (7) and / or metallic shielding layers (8) are introduced between the first rail sections (5a, 5b, 5c) and / or between the second rail sections (6a, 6b, 6c). [3] Power electronics device (1) according to claim 2, characterized by that the second rail sections (6a, 6b, 6c) are formed as a laminated structure with the insulation layers (7) and / or the shielding layers (8). [4] Power electronics device (1) according to claim 2, characterized by that the second rail sections (6a, 6b, 6c) form a cast structure with the insulation layers (7) and / or the shielding layers (8), wherein the insulation layers (7) are introduced between the second busbar sections (6a, 6b, 6c) and / or the shielding layers (8) by a casting process. [5] Power electronics device (1) according to one of claims 1 to 4, characterized by that a thermal conductive layer (10) is arranged between one of the busbars (4a, 4b, 4c) and a housing (9). [6] Power electronics device (1) according to one of claims 1 to 5, characterized bythat a current sensor (11a, 11b, 11c) is arranged on at least two first rail sections (5a, 5b, 5c). [7] Power electronics device (1) according to claim 6, characterized by that shielding walls (12) are arranged between the current sensors (11a, 11b, 11c). [8] Power electronics device (1) according to one of claims 1 to 6, characterized by that the busbars (4a, 4b, 4c) are surrounded by a magnetic core (13). [9] Electrical machine (2) with a stator (14), a rotor (19) and a power electronics device (1) connected to a coil arrangement (15) of the stator (14) or the rotor (19) according to one of claims 1 to 8, wherein each first rail section (5a, 5b, 5c) is directly connected to a power module (3) and a plurality of second rail sections (6a, 6b, 6c) of the power electronics device (1) are each connected to a phase connection (16a, 16b, 16c) of the coil arrangement (15).

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