An inverter generally comprises two DC busbars to which a DC voltage is intended to be applied, these busbars being connected to power modules designed to generate respective AC voltage from the DC voltage.
The inverter often also comprises a capacitor unit (or “capa block”) comprising a housing and, located in the housing, several capacitors. The housing is designed to be closed hermetically in order to prevent water from the exterior to reach the capacitors, causing short circuit.
In order to be connected to the capacitors, the busbars therefore need to pass through the housing. To this end, it is known to form an overmolding over the busbars.
It is also known to fill the housing with a resin or gel to insure good protection of the capacitors.
TECHNICAL PROBLEM
When conducting thermal shock tests on the previous capacitor unit, few small droplets of water have been found inside the housing. This is due to pressure drops in the housing creating an external air intake through imperfections in the overmolding, in particular along the electrical conductors passing through it.
The invention aims to reduce the risk of water ingress inside a housing containing electrical components, along electrical conductors passing through the housing.

To this end, the invention relates to an electrical system comprising:
- a housing,
- an electrical component located in the housing,
- an electrical conductor connected to the electrical component and passing through the housing,
in which the housing comprises, where the electrical conductor passes through, an outer wall and an inner wall separated by a gap surrounding the electrical conductor and filled with a material adhering to the electrical conductor and the outer and inner walls of the housing.
Thanks to the invention, when water tries to enter the housing along the electrical conductor, it meets the material and is likely to be repelled. Therefore, as water ingress is unlikely to occur, internal components are protected from external aggression and, in particular, electrical short circuit can be avoided. Furthermore, there is no need to fill the housing with material such as a resin or gel.
Optionally, the housing comprises an overmolding formed over the electrical conductor and provided with the gap.
Optionally, the gap is a through-hole having two openings.
Optionally, the electrical conductor is a busbar strip.
Optionally, the electrical component is a capacitor.
Optionally, the electrical system further comprises a heatsink including a tub forming a lower part of the housing.
Optionally, the electrical system is an inverter.
Optionally, the material is hydrophobic.
Optionally, the material is viscous.
The invention also relates to a method for manufacturing an electrical system according to the invention, comprising: - obtaining a first part of the housing comprising the outer wall and the inner wall separated by the gap, and the electrical conductor successively passing through the outer wall, the gap and the inner wall; - filling the gap with the hydrophobic material through an opening

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of the gap; and - assembling the first part of the housing with the gap filled with a second part of the housing closing at least in part the opening.
BRIEF DESCRIPTION OF THE DRAWINGS
An exemplary embodiment of the invention will now be described with reference to figures 1 to 9 briefly described below.
Figure 1 is an electrical diagram of an inverter carrying out the invention.
Figure 2 is a three dimensional view of capacitors and busbars of a capacitor unit of the inverter of figure 1.
Figure 3 is a view similar to figure 2 with an overmolding around the busbars.
Figure 4 is a view similar to figure 2 with a cover covering the overmolding.
Figure 5 is a three dimensional view of a heatsink of the inverter of figure 1.
Figure 6 is a three dimensional view of the assembly of the elements of figure 4 with the heatsink of figure 5.
Figure 7 is a three dimensional cross section according to a first point of view, illustrating a gap provided in the overmolding.
Figure 8 is a three dimensional cross section according to a second point of view, illustrating the gap provided in the overmolding.
Figure 9 is a block diagram illustrating steps of a method for manufacturing the inverter of figure 1.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
An electrical system 100 according to the invention is illustrated on figure 1. In the described example, the electrical system 100 is an inverter.
The inverter 100 comprises a first DC electrical connector 102H and a second DC electrical connector 102L. A DC source is intended to be connected to these DC electrical connectors 102H, 102L to apply to them a DC voltage V, so that

a high electric potential is applied to the first DC electrical connector 102H and a low electric potential is applied to the second DC electrical connector 102L.
The inverter 100 further comprises a first busbar 104H and a second busbar 104L, respectively connected to the first and second DC electrical connectors 102H, 102L.
A busbar is a rigid electrical conductor for example designed to withstand electrical currents of at least 1 A. They preferably have a thickness of at least 1 mm and/or an electrical conducting section of at least 1 mm².
The inverter 100 further comprises a capacitor unit including a housing 108 defining an internal space and, located inside the housing 108 (i.e. in the internal space of the housing 108), one or several capacitors 110 connected between the two busbars 104H, 104L.
The electrical system 100 further comprises several power modules 112. Each power module 112 comprises a switching leg comprising a high side switch 114H connected to the first busbar 104H and a low side switch 114L connected to the second busbar 104L. The switches 114H, 114L are further connected together at a middle point. Each power module 112 further comprises a phase electrical connector 116 connected to the middle point and intended to provide an AC phase voltage from the DC voltage V, for example in order to drive an electrical motor (not shown).
In the following, the elements described will be located in space with respect to an arbitrary vertical up-down direction U-D, which may correspond to the usual vertical direction or be different depending on the orientation of the inverter 100.
The DC electrical connectors 102H, 102L, the busbars 104H, 104L and the capacitors 110 are illustrated on figure 2. As it is apparent on figure 2, each busbar 104H, 104L comprises a main body 202H, 202L to which the capacitors 110 are connected and several strips 204H, 206H, 208H, 204L, 206L, 208L extending from the main body 202H, 202L. As it will be explained later, the main bodies 202H, 202L are intended to lie inside the housing 108 while the strips 204H, 206H, 208H, 204L, 206L, 208L are intended to pass through the housing

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108. In particular, the first busbar 104H comprises a first strip 204H connected to the first DC electrical connector 102H, and second and third strips 206H, 208H intended to be connected to the power modules 112. The second busbar 104L comprises a first strip 204L connected to the second DC electrical connector 102L, and second and third strips 206L, 208L intended to be connected to an electrical mass of the inverter 100.
Referring to figure 3, the inverter 100 further comprises an overmolding 302 formed around the busbars 104H, 104L and in particular around the strips 204H, 206H, 208H, 204L, 206L, 208L. The overmolding 302 is for example made by an injection process of plastic, such as a polybutylene terephthalate reinforced with glass fibers. In this manner, the strips 204H, 206H, 208H, 204L, 206L, 208L pass through the overmolding 302.
For each strip 204H, 206H, 208H, 204L, 206L, 208L, the overmolding 302 is provided with a gap 304 opening upwards and downwards and through which the strip 204H, 206H, 208H, 204L, 206L, 208L passes. In the described example, each gap 304 has the shape of a slit. The presence of two openings (in the described example, the upwards and downwards openings) facilitates the overmolding operation. The gaps 304 are distinct from the internal space of the housing 108. The gaps 304 will be described in greater detail below, with reference to figures 7 and 8.
Referring to figure 4, the inverter 100 further comprises a cover 402 covering the overmolding 302. The cover 402 is for example made of plastic.
Referring to figure 5, the inverter 100 further comprises a heatsink 502. In the described example, the heatsink 502 is a single metallic piece obtained by casting.
The heatsink 502 comprises a first horizontal plate 504 on which the power modules 112 are intended to lie. In the described example, an inferior face of the plate 504 is provided with fins 506.
The heatsink 502 further comprises a tub 507 including a bottom 508 and surrounding walls 510 rising from the bottom 508. As it will be apparent later, the tub 507 forms a lower part of the housing 108.

Referring to figure 6, the overmolding 302 is fixed to the top of the surrounding walls 510 so as to extend the surrounding walls 510 upwards. In this manner, the bottom 508 forms a bottom of the housing 108, the walls 510 and the overmolding 302 form together side walls of the housing 108 and the cover 402 forms a top of the housing 108. The housing 108 is thus hermetically closed.
Besides, the heatsink 502 forms an electrical mass of the inverter 100, and thus the second and third strips 206L, 208L of the second busbar 104L are connected to it.
Figure 7 shows in greater details the gap 304 associated with the second strip 206H of the first busbar 104H. It will be noted that the other gaps 304 are similar.
The overmolding 302 forms a portion of a side wall of the housing 108 divided, where the second strip 206H of the first busbar 104H passes through, because of the presence of the gap 304, into an outer wall 702 and an inner wall 704 separated by the gap 304. The gap 304 thus extends inside the side wall of the housing 108 and is separated from the internal space of the housing 108 by the inner wall 704. The gap 304 is intended to be filled with a material adhering to the second strip 206H of the first busbar 104H and the outer and inner walls 702, 704 of the housing 108, at least more than the overmolding 302 adheres to the strips 204H, 206H, 208H, 204L, 206L, 208L. Preferably, the material has a surface tension of at least 36 mN/m.
In this manner, the second strip 206H of the first busbar 104H successively passes through the outer wall 702, the filled gap 304 and the inner wall 704.
Preferably, the material is viscous so that the gap can be easily filled. Furthermore, in case of slight deformation of the second strip 206H of the first busbar 104H, the viscosity keeps the material in contact to the second strip 206H of the first busbar 104H and to the walls 702, 704 of the housing 108. This prevents cracks to appear between the second strip 206H of the first busbar 104H and the walls 702, 704 of the housing 108, by means of which water could enter

the housing 108. For example, the material is a resin or a gel. Preferably, the material has a viscosity between 230 and 600 mPa.s.
Also preferably, the material is hydrophobic to further repel water.
The cover 402 closes the upwards opening of the gap 304, while the wall 510 of the heatsink 502 closes the downwards opening of the gap 304.
It will be noted that the gap 304 extends above and under the second strip 206H of the first busbar 104H.
Referring to figure 8, the gap 304 also extends right and left of the second strip 206H of the first busbar 104H, so that, laterally to the general direction of the second strip 206H of the first busbar 104H from the outside to the inside of the housing 108, the gap 304 surrounds the second strip 206H of the first busbar 104H. In this manner, when water tries to enter the housing along the second strip 206 of the first busbar 104H, it meets the material filling the gaps 304 and is likely to be repelled.
Referring to figure 9, a method 900 for manufacturing the inverter 100 will now be described.
At a step 902, the DC electrical connectors 102H, 102L, the capacitors 110 and the busbars 104H, 104L overmolded by the overmolding 302, as illustrated on figure 3, are obtained. It will be noted that the overmolding 302 forms a first part of the housing 108 comprising, for each busbar strip 204H, 206H, 208H, 204L, 206L, 208L: (i) an outer wall 702 and an inner wall 704 separated by a gap 304, and (ii) the busbar strip 204H, 206H, 208H, 204L, 206L, 208L successively passing through the outer wall 702, the gap 304 and the inner wall 704.
At a step 904, the cover 402 is fixed to the overmolding 302 by means of seal glue to obtain the result illustrated on figure 4. It will be noted that the upper openings of the gaps 304 are therefore closed by the cover 402. The seal glue is for example the same material used to fill the gaps 304 (see step 906 below).
At a step 906, the gaps 304 are filled with the material through their downwards openings. Furthermore, seal glue (for example, the material filling the gaps 304) is applied on a lower periphery of the overmolding 302.

At a step 908, the overmolding 302 with the gaps 304 filled is assembled with the tub 507 of the heatsink 502. By this operation the walls 510 close at least in part the downwards openings of the gaps 304, as illustrated on figure 7. More precisely, the walls 510 of the tub 507 come into contact with the lower periphery of the overmolding 302 so that the applied seal glue forms a seal between said walls 510 and the overmolding 302.
The present invention is not limited to the embodiments previously described, but is instead defined by the claims. It will indeed be apparent to those skilled in the art that modifications can be applied to the previously described embodiments.
Furthermore, the terms used in the claims are not to be construed as limiting the elements of the claims to the elements of the previously described embodiments, but should instead be interpreted to include all equivalent elements that a person skilled in the art applying his general knowledge can predict.

1. Electrical system (100) comprising:
- a housing (108),
- an electrical component (110) located in the housing (108),
- an electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) connected to the electrical component (110) and passing through the housing (108),
characterized in that the housing (108) comprises, where the electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) passes through, an outer wall (702) and an inner wall (704) separated by a gap (304) surrounding the electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) and filled with a material adhering to the electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) and the outer and inner walls (702, 704) of the housing (108).
2. Electrical system (100) according to claim 1, wherein the housing (108) comprises an overmolding (302) formed over the electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) and provided with the gap (304).
3. Electrical system (100) according to claim 1 or 2, wherein the gap (304) is a through-hole having two openings.
4. Electrical system (100) according to anyone of claims 1 to 3, wherein the electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) is a busbar strip.
5. Electrical system (100) according to anyone of claims 1 to 4, wherein the electrical component (110) is a capacitor.
6. Electrical system (100) according to anyone of claims 1 to 5, further comprising a heatsink (502) including a tub (507) forming a lower part of the housing (108).

7. Electrical system (100) according to anyone of claims 1 to 6, wherein the material is hydrophobic.
8. Electrical system (100) according to anyone of claims 1 to 7, wherein the material is viscous.
9. Electrical system (100) according to anyone of claims 1 to 8, being an inverter.
10. Method (900) for manufacturing an electrical system (100) according to anyone of claims 1 to 9, comprising:

- obtaining (902) a first part (302) of the housing (108) comprising the outer wall (702) and the inner wall (704) separated by the gap (304), and the electrical conductor (204H, 206H, 208H, 204L, 206L, 208L) successively passing through the outer wall (702), the gap (304) and the inner wall (704),
- filling (906) the gap (304) with the material through an opening of the gap (304), and
- assembling the first part (302) of the housing (108) with the gap (304) filled with a second part (507) of the housing (108) closing at least in part the opening.