Assembly comprising two power electronics components and an interconnector

Abstract

The present invention relates to an assembly comprising a first power electronics component having a first electrical conduction bar (7) and a second power electronics component having a second electrical conduction bar (8). This assembly includes an interconnector (11) separate from said first electrical conduction bar (7) and second electrical conduction bar (8), the interconnector (11) electrically connecting the first electrical conduction bar (7) and the second electrical conduction bar (8). The first electrical connection bar (7) has a first cross-section and the second electrical connection bar (8) has a second cross-section. The interconnector (11) has a cross-section at least equal to each of the first and second cross-sections and greater than at least one of the first and second cross-sections. The invention also relates to an inverter comprising such an assembly. (See Figure 1 for abbreviations.)

Description

Title of the invention: Assembly comprising two power electronic components and an interconnector TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of electrical and electronic equipment which comprises at least one electrical conduction bar. It relates to the electrical connection between two electronic components crossed by a high-power current. This type of component generally comprises electrical conduction bars, and / or can be linked together by such electrical conduction bars.

[0002] An electrical conduction bar means a metal bar, for example copper, suitable for conducting an electric current. Such a bar is also sometimes referred to as an "interconnection bar", and more generally by the English term "busbars".

[0003] In an inverter, in particular an inverter of an electric automobile powertrain, which constitutes a preferred application of the present invention, the electrical power passes through the various power electronic components of the inverter via electrical conduction bars.

[0004] The present invention is thus explained below in detail within the framework of this preferred application, but is obviously applicable in numerous other applications. STATE OF THE ART

[0005] Electric or hybrid vehicles have a powertrain system powered by a high-voltage battery. The high-voltage battery provides the energy needed by the electric motor (or electric motors) to propel the vehicle.

[0006] To control the motor, the use of an inverter, which converts the direct current from the high voltage battery into alternating current, is well known.

[0007] For this purpose, the inverters comprise power modules comprising electronic switches, for example IGBTs (IGBT meaning insulated gate bipolar transistor), the opening and closing of which are controlled appropriately.

[0008] When passing through an inverter, the power current passes through various power electronic components: an electromagnetic compatibility filter, a DC link, and the power modules. The term DC link here refers to the component generally designated by the English term "DC link", also sometimes called DC bus or DC bus. It has capacitors (called DC link capacitors) that act as an intermediate buffer between the input source and the output load, which have different instantaneous powers, voltages, and frequencies. In electric vehicle applications, DC link capacitors help compensate for the effects of inductance in the electrical system. They also serve as filters that protect vehicle subsystems from voltage spikes, surges, and electromagnetic interference.

[0009] The connections through which the electrical power passes through the inverter are generally made in the form of electrical conduction bars.

[0010] Such an inverter thus comprises an assembly of several components which are generally included in a casing. These components typically comprise one or more terminals allowing their connection.

[0011] In particular due to the high power currents which pass through them during operation, the components of the inverter generate heat which can impair the proper functioning of these components or damage them. This is particularly the case for power modules due to the numerous switching operations of the electronic switches. This is also the case for all the components crossed by the current, which heat up by the Joule effect.

[0012] For example, in some inverters, the connection between the output of the electromagnetic compatibility filter and the DC link capacitors (i.e. the "DC link") is made by extending the busbar of the DC link. Depending on the general configuration of the inverter in question, this may prove unsuitable, for thermal reasons and / or energy losses.

[0013] The present invention thus concerns the electrical connections between two power electronic components. Statement of the invention

[0014] The present invention aims to remedy all or part of the drawbacks of the state of the art cited above.

[0015] For this purpose, the invention relates to an assembly comprising a first power electronics component comprising a first electrical conduction bar and a second power electronics component comprising a second electrical conduction bar. This assembly comprises an interconnector, distinct from said first electrical conduction bar and second electrical conduction bar. The interconnector electrically connects the first electrical conduction bar and the second electrical conduction bar. The interconnector is such that, the first electrical connection bar having a first section and the second electrical connection bar having a second section, the interconnector has a section at less than equal to each of the first section and second section and greater than at least one of the first section and second section.

[0016] Throughout this document, the concept of section of an electrical conduction bar is understood as the surface area of ​​the transverse plane section of the conduction bar.

[0017] The electrical conduction bar may be made of copper in particular. The term "copper" refers to this metal, its grades and its alloys commonly used as an electrical conductor. The electrical conduction bar may be made of bare copper, or may have a coating of nickel, tin, silver, or several of these metals. The conduction bar may alternatively be made of aluminum, brass or bronze. These metals may be bare or may have a metallic coating.

[0018] The assembly may include a housing, and a thermal interface that is electrically insulating but thermally conductive may be interposed between the interconnector and a surface of the housing.

[0019] The thermal interface may comprise a thermal paste.

[0020] A thermal paste is a substance that increases the thermal conductivity between the surfaces between which it is interposed. The thermal paste may in particular be silicone-based or ceramic-based. In the present application, a thermally conductive but electrically insulating thermal paste is selected.

[0021] A first bond is formed between the interconnector and the first electrical conduction bar, and a second bond is formed between the interconnector and the second electrical conduction bar, and at least one of the first bond and the second bond may be a solder or a braze.

[0022] Weld is understood to mean the connection resulting from welding, for example by laser, and brazing is understood to mean the connection resulting from soldering.

[0023] In particular, one of the first connection and the second connection being a brazing or welding, the other of the first connection and the second connection may be a screw connection.

[0024] The thermal interface may in particular be interposed between the surface of the casing and a weld or brazing type connection.

[0025] The interconnector may be formed from a metal bar or a laminated metal bar. The use of a laminated (sometimes also called "laminated") metal bar formed from a superposition of thin metal sheets gives the interconnector great flexibility allowing it to adapt to the configuration of the components being connected. This may be advantageous when the configuration is complex, and / or when only a small number of parts are produced.

[0026] The first electrical conduction bar and the second electrical conduction bar may extend in parallel planes spaced apart from each other, and the interconnector can then have, seen in longitudinal section, an S-shaped profile for example.

[0027] Depending on the configuration of the assembly comprising the interconnector, the latter may have other shapes, seen in longitudinal section. For example, the interconnector may have an L shape, allowing the connection of electrical conduction bars which extend perpendicularly to each other. The interconnector may have a Q shape (Greek letter omega) allowing a certain adjustment in two directions of the connections between the interconnector and the electrical conduction bars. This embodiment is advantageously produced with an interconnector composed of a laminated metal bar, which provides a certain flexibility.

[0028] The interconnector advantageously has a substantially constant section. This section may be between 20 mm2 and 60 mm2, preferably between 30 mm2 and 50 mm2, for example 39 mm2. It is recalled that the section corresponds in the present document to the surface of the transverse plane section. The interconnector may in particular have the shape of a flat bar, of section (as shape of the transverse section) substantially rectangular.

[0029] Obviously, each of the first power electronics component and second power electronics component may comprise two electrical interconnection bars, and the assembly may then comprise two interconnectors. Everything that has been described in relation to the interconnector is applicable in this case to each of the interconnectors.

[0030] According to a preferred application of the invention, the first power electronics component may be an electromagnetic compatibility filter (for example located at the input of a power converter, in particular an inverter) and the second power electronics component is a DC connection of a power converter.

[0031] The invention also relates to an inverter comprising an assembly as previously described. BRIEF DESCRIPTION OF THE FIGURES

[0032] Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the present invention, with reference to the appended drawings, in which: • [Fig.l] represents, in a three-dimensional schematic view, an assembly conforming to an embodiment of the invention in its immediate environment of use; • [Fig.2] represents the whole of [Fig.l] in a schematic view of detail ; • [Fig.3] represents a schematic sectional view of the whole of [Fig.2]; • [Fig.4] is a schematic sectional view of an example of an interconnector that can be used to form an assembly in accordance with the subject of the present invention; • [Fig.5] is a schematic sectional view of another example of an interconnector; • [Fig.6] is a schematic sectional view of another example of an interconnector. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present description is given as a non-limiting example of embodiment.

[0034] [Fig.l] partly represents an inverter 1, comprising a casing 2 in which the various electronic components constituting the inverter 1 are arranged.

[0035] In the application example shown here, the inverter comprises an input filter, namely an electromagnetic compatibility filter 3 generally referred to as an “EMC filter” intended to prevent disturbances in the equipment connected to the inverter power supply. This is then referred to as filtering the power signal.

[0036] The electromagnetic compatibility filter 3 is thus generally formed from a combination of one or more electrical conduction bars, one or more inductors and one or more capacitors.

[0037] Each electrical conduction bar must be connected, at the input 301 of the electromagnetic compatibility filter 3, to the high voltage circuit enabling the inverter to be powered, here respectively to the positive pole and the negative pole of this circuit and of the high voltage battery. This connection which ensures the electrical power supply of the inverter 1 is made via the high voltage connector 4.

[0038] The output 302 of the electromagnetic compatibility filter 3 must be connected to a DC link 5 (also called “DC link”) which comprises a set of capacitors, and which ensures the electrical connection with the power modules 6 of the inverter.

[0039] The present invention finds a particularly advantageous application at the level of the connection between the output 302 of the electromagnetic compatibility filter 3 and the DC connection 5, as shown in detail in [Fig.2].

[0040] The electromagnetic compatibility filter 3 constitutes in this context a first power electronics component comprising a first electrical conduction bar 7. The DC link 5 constitutes a second power electronics component comprising a second electrical conduction bar 8. The first electrical conduction bar 7 must be electrically connected to the second electrical conduction bar.

[0041] Obviously, the electromagnetic compatibility filter 3 also comprises another electrical conduction bar, which is designated here as the third electrical conduction bar 9 of the assembly, and the DC connection 5 also comprises another electrical conduction bar or fourth electrical conduction bar 10.

[0042] What is explained below concerning the connection between the first electrical conduction bar 7 and the second electrical conduction bar 8 can be applied mutatis mutandis to the connection between the third electrical conduction bar 9 and the fourth electrical conduction bar 10.

[0043] It has thus been found that in certain assemblies comprising power electronic components, likely to be crossed by significant currents, the electrical connection between these components can prove problematic. In particular, in the example shown, there is a certain distance and a difference in level between the output 32 of the input filter 3, that is to say the end of the first electrical conduction bar 7, and the input of the DC link, that is to say the end of the second electrical conduction bar 8.

[0044] It would be complex to extend the first electrical conduction bar or the second electrical conduction bar, and this would have a significant cost, in particular due to the complex geometry that this would involve.

[0045] This could also pose significant thermal problems.

[0046] Indeed, taking the example shown, the section of the electrical conduction bars of the DC link is sized to ensure satisfactory electrical conduction, but they can nevertheless undergo heating by the Joule effect. In the DC link, the capacitors are generally embedded in a coating material (generally called by the English term "potting") which is thermally conductive and which allows the heat generated in the DC link to be evacuated to suitable cooling means (radiators, liquid cooling circuit, etc.). Outside of the DC link itself, such heat evacuation is not ensured.

[0047] Furthermore and generally, it is appropriate to limit energy losses in these connections.

[0048] It is thus planned to make the connection and the electrical connection between the first electrical conduction bar 7 and the second electrical conduction bar 8 by an interconnector 11. The interconnector 11 is formed of copper or nickel. The notion of copper includes the grades of copper and copper alloys commonly used as electrical conductors, as well as tinned copper, copper having undergone a surface treatment, or even rolled or laminated copper. The same applies to nickel.

[0049] The interconnector 11 comprises a first end 111 intended to be connected to the first electrical conduction bar, the end of which at the output 32 of the input filter 3 forms a connection terminal.

[0050] The interconnector 11 comprises a second end 112 intended to be connected to the second electrical conduction bar, the end of which at the level of the input filter 3 forms a connection terminal.

[0051] As seen in [Fig. 3], the interconnector has, according to the present invention, a section at least equal to the section of the first electrical conduction bar and the section of the second electrical conduction bar. Furthermore, the section of the interconnector is greater than the section of at least one of the first electrical conduction bar and the second electrical conduction bar. In other words, the section of the interconnector is greater than or equal to the section of each of the first electrical conduction bar and the second electrical conduction bar, and greater than at least one of these sections.

[0052] Thus, it is certain that the interconnector will not constitute an obstacle to the flow of current, compared to the components to which it is connected.

[0053] The heating by Joule effect of the interconnector is thus limited.

[0054] Obviously, the connections between the interconnector 11 and the first electrical conduction bar 7 and between the interconnector 11 and the second electrical conduction bar must not constitute heating zones by Joule effect. For this, these connections can be made by welding or brazing, or by screws. In these two cases, the contact surface between the interconnector 11 and the electrical conduction bar considered is at least equal to, and preferably greater than, the cross-section of the interconnector. The contact surface must be flat and free of burrs.

[0055] In the example of the embodiment shown in [Fig. 3], the connection between the interconnector 11 and the first electrical conduction bar 7 is a screw connection. Such a connection uses a screw 12, the screwing of which causes the interconnector 11 to be tightened against the electrical conduction bar 7. In particular, the screw 12 can pass through the interconnector 11 and the electrical conduction bar via holes formed in these elements, and, while the head 121 of the screw 12 presses on one of these elements (directly or via a support washer), the screw 12 is engaged in a nut 122 bearing on the other of these elements.

[0056] The connection between the interconnector 11 and the second electrical conduction bar 8 is a weld or a brazing. A brazing is generally simpler to produce and requires a lower investment in tools. A weld is generally quicker to produce and is less expensive (because it does not require filler metal).

[0057] Obviously, the connection between the interconnector 11 and the first electrical conduction bar 7 can be made alternatively by welding or brazing. The connection between the interconnector 11 and the second electrical conduction bar 8 can alternatively be a screw connection.

[0058] In the embodiment of [Fig. 3], a thermal interface 13 is interposed between the interconnector 11 and the casing 2. More precisely, a thermal interface 13 is interposed between the interconnector 11 and a pad 201 formed by the casing 2.

[0059] The thermal interface 13 may consist, for example, of a thermal paste, also referred to by the English term “gap filler”. Such a thermal paste is deposited in a pasty form during the manufacture of the power electronics system in question, which is typically an inverter.

[0060] The paste is compressed between the interconnector 11 and the casing 2, which has the effect to improve its thermal conductivity properties. The paste then polymerizes but retains a certain flexibility.

[0061] The use of a thermal paste ensures good heat transmission to the casing, in particular thanks to the spreading of the paste. The heat is then evacuated by the casing, and if necessary by a heat transfer fluid of a liquid cooling system. Alternatively, the use of a thermal pad (generally called a "thermal pad" or "gap pad" according to the usual English terminology) is possible.

[0062] The establishment of a thermal interface is here partly permitted by the fact that the connection between the interconnector 11 and the second electrical conduction bar 8 is made by welding (or brazing), leaving the lower surface of the interconnector 11 free at the level of this connection.

[0063] In the example shown, the presence of a thermal interface 13 at the connection with the second conduction bar is all the more relevant since the section of the second conduction bar 8 is small compared to that of the first conduction bar 7, and of course of the interconnector 11, so that certain heating could occur in this zone.

[0064] Such a thermal interface can nevertheless be provided in any other location, between the interconnector and the casing 2.

[0065] [Fig. 4] is a schematic sectional view of an example of an interconnector, in this case the interconnector 11 used in the assembly shown in Figures 1 to 3.

[0066] The interconnector 11 has, seen in longitudinal section, an S-shaped profile. This makes it possible to connect electrical conduction bars which extend in distant and parallel planes. In this case, the interconnector is configured so as to form, for its connection with the first conduction bar, an interface in a PI plane located on a lower surface of the interconnector 11. The interconnector 11 is configured so as to form, for its connection with the second conduction bar, an interface in a plane P2 located on an upper surface of the interconnector 11. The plane PI is distinct from the plane P2, and PI and P2 are parallel to each other.

[0067] [Fig. 5] is a schematic sectional view of an example of an interconnector 11 which, seen in longitudinal section, has a Q-shaped profile. The central part of the interconnector gives it a certain flexibility allowing adaptation of the relative position between the first end 111 and the second end 112 of the interconnector. In order to increase the flexibility of the interconnector 11, it may be formed from a laminated metal bar.

[0068] [Fig. 6] is a schematic sectional view of an example of an interconnector 11 which has, seen in longitudinal section, an L-shaped profile.

[0069] Thus, within the framework of the present invention, an assembly is proposed comprising power electronic components whose electrical conduction bars are connected to each other by an interconnector, which limits energy losses and heating. For this, the cross-section of the interconnector is at least equal to the largest cross-section of the electrical conduction bars of the power electronic components that it connects, or even greater than the cross-section of the conduction bars of the components that it connects.

[0070] The invention is of particular interest in an inverter, in particular an inverter used in an electric or hybrid motor vehicle, where the connection between power electronic components in a closed environment could lead to thermal problems.

Claims

Claims

1. An assembly comprising a first power electronics component comprising a first electrical conduction bar (7) and a second power electronics component comprising a second electrical conduction bar (8), the assembly comprising an interconnector (11) separate from said first electrical conduction bar (7) and second electrical conduction bar (8), the interconnector (11) electrically connecting the first electrical conduction bar (7) and the second electrical conduction bar (8), the first electrical connection bar (7) having a first section, the second electrical connection bar (8) having a second section, the interconnector (11) having a section at least equal to each of the first section and second section and greater than at least one of the first section and second section.

2. An assembly according to claim 1, wherein the assembly comprises a housing (2), and wherein a thermal interface (13) which is electrically insulating but thermally conductive, is interposed between the interconnector (11) and a surface of the housing (2).

3. An assembly according to claim 2, wherein the thermal interface (13) comprises a thermal paste.

4. An assembly according to one of the preceding claims comprising a first connection between the interconnector and the first electrical conduction bar, and a second connection between the interconnector and the second electrical conduction bar, wherein at least one of the first connection and the second connection is a weld or a braze.

5. An assembly according to claim 4, wherein only one of the first connection and the second connection is a solder or a weld, and wherein the other of the first connection and the second connection is a screw connection (12).

6. An assembly according to claim 2 and claim 4, wherein the thermal interface (13) is interposed between the surface of the casing (2) and the weld or braze type connection.

7. An assembly according to any preceding claim, in which the interconnector (11) is formed of a metal bar or a laminated metal bar.

8. An assembly according to any one of the preceding claims, wherein the first electrical conduction bar (7) and the second electrical conduction bar (8) extend in planes (PI, P2) parallel and distant from each other, and the interconnector (11) has, seen in longitudinal section, an S-shaped profile.

9. Assembly according to any one of the preceding claims, in which the interconnector (11) has a substantially constant section, between 20 mm2 and 60 mm2, preferably between 30 mm2 and 50 mm2, for example 39 mm2.

10. An assembly according to any preceding claim, wherein each of the first power electronics component and second power electronics component comprises two electrical interconnection bars, and the assembly comprises two interconnectors.

11. An assembly according to any preceding claim wherein the first power electronics component is an electromagnetic compatibility filter (3) and the second power electronics component is a DC link (5) of a power converter.

12. An inverter (1) comprising an assembly according to any one of the preceding claims.

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