Electrical system housing comprising attachment tabs incorporating local inductors

Abstract

The invention relates to an electrical system (30) comprising: - a housing (31) comprising a lateral mounting wall (331) forming a radiator (35) for power transistors or behind which a fin radiator is located, - the lateral mounting wall (33.1) comprising attachment tabs (37), - the attachment tabs (37) protruding with respect to a thickness of the lateral mounting wall (33.1) so that the lateral mounting wall (33.1) is placed at a distance from the frame, - each attachment tab (37) comprising a corresponding local inductor (40), such that a common mode current originating from the power transistors and passing through the radiator (35) can be channelled to the frame via the local inductors (40) of the attachment tabs (37), forming a path having an impedance at high frequency between the radiator (35) and the frame.

Description

DESCRIPTION TITLE: ELECTRICAL SYSTEM HOUSING WITH MOUNTING BRACKS INCLUDING INDUCTORS LOCAL

[0001] The present invention relates to an electrical system housing comprising mounting tabs incorporating local inductances. The invention finds a particularly advantageous, but not exclusive, application in the field of power electricity with electrical circuits associated with high-power rotating electrical machines equipping a vehicle, in particular an aircraft.

[0002] Figure 1 represents a classic electrical architecture 10 comprising two static electrical converters, namely a rectifier 12 capable of transforming a polyphase alternating voltage into a direct voltage and an inverter 14 capable of transforming a direct voltage into a polyphase alternating voltage. The electrical architecture 10 includes an alternating network 16 for supplying a load 18, such as a polyphase electric motor, through the rectifier 12, generating a direct voltage from the alternating voltage from the alternating network 16, and through the inverter 14 supplying a polyphase alternating voltage to the electrical load 18 from the direct voltage.

[0003] The inverter 14 is mounted on a heatsink for cooling. The inverter 14 has three bridge arms (14u, 14v, and 14w, one per phase), each with two transistors, for example MOSFETs or IGBTs (Insulated Gate Bipolar Transistors), controlled in on / off mode. Each transistor can be paired with a diode. In the example shown, the three-phase electrical load 18 has three phases, each connected to a corresponding bridge arm (14u, 14v, 14w).

[0004] In this electrical architecture 10, two types of currents are distinguished, namely a useful current going from the source 16 to the load 18 and a unnecessary current, called common mode current Imc, which goes from the source 16 to the radiator connected to the chassis and therefore to ground 20 via parasitic capacitors 24.

[0005] To reduce the common-mode current (Imc), it is known to insert an inductor, called a common-mode inductor (22), as part of an LC filter. This common-mode inductor (22) simultaneously sees both the useful and waste currents, which necessitates sizing it accordingly. Conventional common-mode inductors (22), generally in the form of a toroid, therefore present significant constraints in terms of size and mass. A common-mode inductor (22) for a 50kW inverter (14) typically weighs more than 800 grams.

[0006] The common-mode current Imc is primarily due to the parasitic capacitances of the converter transistors 14. Document EP4145505A1 describes how to locally filter the common-mode current using a specific local inductance at each transistor. This reduces the stress on the input LC filter inductance 22. However, such a solution, implemented by the circuit manufacturer or foundry, is expensive and complex.

[0007] The invention aims to effectively remedy the aforementioned drawbacks by proposing an electrical system comprising: - at least one electrical converter comprising a plurality of power transistors, - a casing made of an electrically conductive material, defining an enclosure in which the electrical converter is placed, - said housing comprising a supporting side panel forming a heat sink for the power transistors or behind which is a finned heat sink on which the power transistors are mounted, - said side support panel comprising fixing brackets intended to secure the electrical system to a chassis, - the fixing brackets protruding beyond a certain thickness of the wall lateral support, so that the lateral support wall is positioned at a distance from the chassis, - each mounting tab having a corresponding local inductance, so that a common mode current from the power transistors and passing through the heatsink can be channeled to the chassis via the local inductances of the mounting tabs forming a high-frequency impedance path between the heatsink and the chassis.

[0008] The invention thus makes it possible to reduce the common-mode current and therefore to reduce the mass and size of the common-mode inductance in power converters while maintaining the rigidity required during vibration tests. Indeed, the added mass due to local inductances (a few tens of grams per mounting tab) is negligible compared to the reduction of the common-mode inductance mass by a factor of 2 to 10. The invention also makes it possible to increase the dV / dT switching ratio of the converter's transistors. The invention also has the advantage of being simple to implement and low-cost.

[0009] According to one embodiment of the invention, each local inductance comprises at least one ferromagnetic core disposed on or at least partly inside a corresponding mounting tab.

[0010] According to one embodiment of the invention, the ferromagnetic core is disposed at least partly inside a correspondingly shaped groove made in a fixing tab.

[0011] According to one embodiment of the invention, the ferromagnetic core is glued or brazed onto the housing around the mounting tab.

[0012] According to one embodiment of the invention, the ferromagnetic core is arranged around a pad extending between the housing and a corresponding mounting tab.

[0013] According to one embodiment of the invention, the ferromagnetic core is arranged between a face of a mounting tab and a retaining plate. corresponding, stiffening pads extending between one face of the fixing bracket and a face opposite the retaining plate.

[0014] According to one embodiment of the invention, individual ferromagnetic cores are arranged around each stiffening pad.

[0015] According to one embodiment of the invention, the ferromagnetic core takes the form of a tile provided with holes for the passage of the fixing element and the stiffening pads.

[0016] According to one embodiment of the invention, the ferromagnetic core is mounted between two walls of a spacer connected to each other by a connecting stud around which the ferromagnetic core is arranged.

[0017] According to one embodiment of the invention, the ferromagnetic core consists of a ring of round, rectangular or ovoid shape, or any other geometric shape suitable for the application.

[0018] According to one embodiment of the invention, the ferromagnetic core is a single piece.

[0019] According to one embodiment of the invention, the ferromagnetic core is made in two parts assembled together.

[0020] According to one embodiment of the invention, the fixing tabs are made at least partly of a ferromagnetic material constituting the local inductances of the fixing tabs.

[0021] According to one embodiment of the invention, said electrical system comprises a ferromagnetic sheet disposed between the side support wall of the housing and the chassis.

[0022] The invention also relates to an assembly comprising an electrical system as previously defined and a chassis on which said electrical system is fixed.

[0023] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0024] [Fig. 1] Figure 1, already described, is an electrical architecture with static electrical converters equipped with a common mode inductance aimed at reducing the common mode current due to the parasitic capacitances of the transistors of an inverter;

[0025] [Fig. 2a] [Fig. 2b] [Fig. 2c] Figures 2a, 2b and 2c are perspective and cross-sectional views from different angles of an electrical system housing equipped with mounting tabs incorporating local inductances according to the invention;

[0026] [Fig. 3] Figure 3 is a schematic side view illustrating the empty space provided between the housing according to the invention and the mounting frame;

[0027] [Fig. 4a] [Fig. 4b] Figures 4a and 4b are a perspective view of different shapes of ferromagnetic cores according to the invention;

[0028] [Fig. 5] Figure 5 is a perspective view representing a first variant of the realization of a local inductance of the fixing lug according to the invention;

[0029] [Fig. 6] Figure 6 is a schematic representation of a second embodiment of a local inductance of the fixing leg according to the invention;

[0030] [Fig. 7] Figure 7 is a schematic representation of a third embodiment of a local inductance of the fixing leg according to the invention;

[0031] [Fig. 8] Figure 8 is a schematic representation of a fourth embodiment of a local inductance of the fixing leg according to the invention;

[0032] [Fig. 9] Figure 9 is a schematic representation of a fifth embodiment of a local inductance of the fixing lug according to the invention;

[0033] [Fig. 10] Figure 10 is a schematic representation of a sixth embodiment of a local inductance of the fixing lug according to the invention;

[0034] [Fig. 11] Figure 11 is a schematic representation illustrating the insertion of a ferromagnetic sheet between a chassis and the housing of the electrical system according to the invention.

[0035] It should be noted that, in the figures, structural and / or functional elements common to the different embodiments may have the same reference numbers. Thus, unless otherwise stated, such elements have identical structural, dimensional, and material properties.

[0036] Figures 2a, 2b and 2c show an electrical system 30 comprising a housing 31 made of an electrically conductive material delimiting an enclosure 32 in which at least one electrical converter 14 is disposed. The housing 31 is an electromagnetic compatibility (EMC) housing 31 allowing to avoid electromagnetic disturbances which are troublesome for any electrical component in the environment of the system.

[0037] The electrical converter 14 comprises a plurality of power transistors. The electrical converter 14 is, for example, an inverter 14. This electrical converter 14 is integrated into an electrical architecture similar to that of Figure 1, arranged within the housing 31.

[0038] More specifically, the parallelepiped-shaped housing 31 comprises a plurality of side walls 33.1-33.6 delimiting the enclosure 32. One of the side walls, in this case wall 33.1, referred to as the "support side wall", carries the The electrical converter 14 includes mounting brackets 37 for securing the electrical system 30 to a chassis 36 (see figure 3). The chassis 36 may, for example, be a structural element of an aircraft.

[0039] To dissipate heat from the power converter 14, said power converter 14 is mounted on a heat sink 35. The heat sink 35 may be formed by the supporting side panel 33.1. The power converter 14 is then mounted directly against an inner face of the supporting side panel 33.1 facing the interior of the enclosure 32. When the heat sink 35 is formed by the supporting side panel 33.1, the panel 33.1 may be a plate within which channels for circulating a cooling fluid are defined. The housing 31 is then provided with an inlet and an outlet for the cooling fluid, for example, oil or water containing antifreeze.

[0040] Alternatively, the radiator 35 can be a finned radiator mounted on the side support wall 33.1 by which the housing 31 is attached to the chassis 36. A fan 34, visible in Figure 2a, can be mounted on the housing 31 to generate an internal airflow to dissipate heat from the converter 14 by convection. The housing 31 can also include connectors 39 for receiving power and / or control signals from the electrical system 30.

[0041] The mounting brackets 37 project from an edge of the supporting side wall 33.1. Each mounting bracket 37 has an opening for a fastener, such as a screw, stud, rivet, or any other fastener suitable for the application. The mounting brackets 37 may be right-angled.

[0042] The mounting tabs 37 can be integral with the supporting side wall 33.1. The mounting tabs 37 can be brazed or sintered onto the housing 31. In one embodiment, the housing 31 has four mounting tabs 37 arranged at the four corners of the supporting side wall 33.1. Alternatively, the housing 31 may have fewer or more than four mounting tabs 37.

[0043] The mounting tabs 37 project beyond the thickness of the support side wall 33.1, such that the support side wall 33.1 is positioned at a distance from the chassis 36 when the housing 31 is mounted on the chassis, as shown in Figure 3. For example, a gap 38 is provided between the support side wall 33.1 and the chassis 36, having, for example, a thickness of approximately 0.5 mm. The thickness of the gap 38 is adjusted according to the order of magnitude of the common-mode current intensity. In other words, the mounting tabs 37 protrude from the plane of the support side wall 33.1. This protrusion is labeled D in Figure 2c. The protrusion of the fixing tabs 37 can be achieved by means of a chamfer or by an extra thickness of the fixing tabs 37.1.

[0044] Each mounting tab 37 has a corresponding local inductance 40, so that a common-mode current from the power transistors of the converter 14 and passing through the heatsink 35 can be channeled to the chassis 36 via the local inductances 40 of the mounting tabs 37 forming a high-frequency impedance path between the heatsink 35 of the converter 14 and the chassis 36.

[0045] The mounting tabs 37 thus have a dual function, namely a mechanical fixing function and a function of channeling common mode currents to the chassis 36 to ground.

[0046] It is important that each of the mounting tabs 37 be associated with a local inductance 40 in order to prevent the common mode current from finding a path of lower impedance than that through the local inductances 40 of the mounting tabs 37.

[0047] Each local inductance 40 may include at least one ferromagnetic core 41 disposed on or at least partly inside a corresponding mounting tab 37.

[0048] In the embodiment of figures 2a to 2c, the ferromagnetic core 41 is disposed at least partly inside a correspondingly shaped groove 42 formed in a fixing tab 37.

[0049] The ferromagnetic core 41 can be a ring of round shape (see Figure 4a), rectangular shape (see Figure 4b), square shape, ovoid shape, or any other geometric shape suitable for the application. The term "ring" refers to a ferromagnetic core 41 with a closed circumference defining an internal opening, and which can take various forms.

[0050] The ferromagnetic core 41 can be a single piece, as shown in Figure 4a. Alternatively, the ferromagnetic core 41 is made of two parts joined together, for example by bonding or sintering, as shown in Figure 4b. A two-part ferromagnetic core 41 can facilitate core replacement. The ferromagnetic core 41 can be made of a ferromagnetic material selected from: ferrite, or any other iron-, cobalt-, and / or nickel-based material. The dimensions of the ferromagnetic core 41 are adapted according to the order of magnitude of the common-mode current intensity.

[0051] In the embodiment of Figure 5, the ferromagnetic core 41 is glued or brazed onto the housing 31 around the mounting tab 37. In this case, it may be advantageous to use a two-part ferromagnetic core 41.

[0052] In the embodiment shown in Figure 6, the ferromagnetic core 41 is arranged around a stud 45 extending between the housing 31 and a corresponding mounting tab 37. The ferromagnetic core 41 has a cross-section with a shape corresponding to that of the stud 45, in particular a round, rectangular, square, or ovoid shape, or any other shape suitable for the application.

[0053] In the embodiment of Figure 7, the ferromagnetic core 41 is arranged between a face of a fixing tab 37 and a corresponding retaining plate 46.

[0054] Stiffening pads 50 extend between one face of the mounting bracket 37 and an opposite face of the retaining plate 46. Individual ferromagnetic cores 51 are arranged around each stiffening pad 50. The individual ferromagnetic cores 51 have a cross-section with a shape corresponding to that of the stiffening pads 50. including a round, rectangular, square or ovoid shape, or any other shape suitable for the application.

[0055] A fastener 47, such as a screw, stud or rivet or any other type of fastener suitable for the application, is inserted into a passage opening made in the fixing tab 37, an opening in the ferromagnetic core 41 and a passage opening in the retaining plate 46,

[0056] The embodiment of figure 8 is analogous to that of figure 7 except that the ferromagnetic core 41 takes the form of a tile 54 with holes for the passage of the fixing member 47 and the stiffening studs 50. The tile 54 has the form of a flat plate of low thickness.

[0057] In the embodiment of Figure 9, the ferromagnetic core 41 is mounted between two walls 55 of a spacer 56 connected to each other by a connecting stud 57 around which the ferromagnetic core 41 is arranged. The connecting stud 57 may be hollow to allow the passage of a fastener 58, such as a screw, a stud or a rivet or any other type of fastener suitable for the application, also inserted inside an opening made in the fixing tab 37.

[0058] In the embodiment of Figure 10, the fixing tabs 37 are made at least partly of a ferromagnetic material constituting the local inductances 40 of the fixing tabs 37.

[0059] In the embodiment shown in Figure 11, a ferromagnetic sheet 60 is positioned between the supporting side wall 33.1 of the housing 31 and the chassis 36. The ferromagnetic sheet 60 is fixed to the rear face of the supporting side wall 33.1 facing the chassis 36. When the housing 31 is attached to the chassis 36, the ferromagnetic sheet 60 is in contact on one side with the supporting side wall 33.1 of the housing 31 and on the other with the chassis 36. The ferromagnetic sheet 60 thus allows for better distribution of unnecessary common-mode currents. This results in an additional improvement in EMC (Electromagnetic Compatibility) signature. The ferromagnetic sheet 60 can be used with all the embodiments described above. The EMC gain can advantageously be optimized by using different ferromagnetic materials for the ferromagnetic sheet 60 and the magnetic core(s) 41 in the mounting tabs 37.

[0060] The ferromagnetic sheet 60 is, in practice, thick enough to ensure contact on both sides (housing 31 and chassis 36) depending on the mounting system. To account for surface defects (flatness, roughness) that could damage the sheet during use, the ferromagnetic sheet 60 is sufficiently thick, specifically greater than 0.5 mm, to prevent any contact between the side support wall 33.1 of the housing 31 and the chassis 36.

[0061] According to this embodiment, a conduction current is distinguished on the one hand, passing through the housing 31 and the local inductances 40 of the mounting tabs 37, then going to the system ground via the chassis 36, and on the other hand, a displacement current passing through the housing 31 and the ferromagnetic sheet 60, then going to the system ground via the chassis 36. The conduction current has a frequency, in particular, between 150 kHz and 150 MHz. The displacement current has a frequency, in particular, between 1 MHz and 300 MHz.

[0062] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways as long as they are not incompatible or mutually exclusive.

[0063] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variations that a person skilled in the art may envision within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be considered separately or in combination.

Claims

DEMANDS 1. Electrical system (30) comprising: - at least one electrical converter (14) comprising a plurality of power transistors, - a housing (31) made of an electrically conductive material delimiting an enclosure (32) in which the electrical converter (14) is placed, - said housing (31) comprising a supporting side wall (33.1) forming a heat sink (35) for the power transistors or behind which is a finned heat sink on which the power transistors are mounted, - said side support wall (33.1) having fixing lugs (37) intended to secure the electrical system (30) to a chassis (36), characterized in that the fixing lugs (37) extend in projection relative to a thickness of the supporting side wall (33.1), so that the supporting side wall (33.1) is disposed at a distance from the chassis (36), - each mounting tab (37) having a corresponding local inductance (40), so that a common-mode current from the power transistors and passing through the heatsink (35) can be channeled to the chassis (36) via the local inductances (40) of the mounting tabs (37) forming a high-frequency impedance path between the radiator (35) and the chassis (36).

2. Electrical system according to claim 1, characterized in that each local inductance (40) comprises at least one ferromagnetic core (41) disposed on or at least partly inside a corresponding mounting tab (37).

3. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is disposed at least in part inside a correspondingly shaped groove (42) formed in a fixing tab (37).

4. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is glued or brazed onto the housing (31) around the fixing tab (37).

5. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is arranged around a pad (45) extending between the housing (31) and a corresponding mounting tab (37).

6. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is disposed between a face of a fixing tab (37) and a corresponding retaining plate (46), stiffening pads (50) extending between a face of the fixing tab (37) and an opposite face of the retaining plate (46).

7. Electrical system according to claim 6, characterized in that the ferromagnetic core (41) takes the form of a tile (54) provided with holes for the passage of the fixing member (47) and the stiffening pads (50).

8. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is mounted between two walls (55) of a spacer (56) connected to each other by a connecting stud (57) around which the ferromagnetic core (41) is arranged.

9. Electrical system according to any one of claims 2 to 8, characterized in that the ferromagnetic core (41) is constituted by a ring of round, rectangular or ovoid shape, or any other geometric shape suitable for the application.

10. Electrical system according to claim 1, characterized in that the fixing tabs (37) are made at least partly of a ferromagnetic material constituting the local inductances (40) of the fixing tabs (37).

11. Electrical system according to any one of claims 1 to 10, characterized in that it comprises a ferromagnetic sheet (60) disposed between the side support wall (33.1) of the housing (31) and the chassis (36).

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