Electrically shielded cable

Abstract

The invention relates to a cable (1, 10, 20, 30) comprising a central electrical conductor (2) and a shielding layer (3) surrounding the central conductor (2) and forming a tubular sheath housing the conductor (2), the shielding layer (3) comprising a plurality of strands (31, 32, 33, 34) wound in a spiral manner around the central conductor (2) at a pitch greater than or equal to 100 mm in order to obtain a characteristic frequency greater than or equal to 1 MHz.

Description

Technical Field

[0001] The present invention relates to an electric cable with electromagnetic shielding and in particular to an electric cable for use in motor vehicles and more particularly to an electric cable with high voltage, advantageously for voltages greater than 48 volts. Background Art

[0002] Shielded cables are often used when connecting electrical components together. When there are a large number of electrical components, the cables are subject to severe electromagnetic stress and require shielding. In the case of high-voltage cables, the shielding must ensure protection at high frequencies (above a characteristic frequency of 1 MHz, preferably between 1 MHz and 100 MHz).

[0003] In this application field, the shield covers the insulation surrounding the cell. The shield is obtained by using a braid, a strip or a combination of braided strips made of a conductive material. Shielding based on strands arranged in a spiral manner is not currently used in this application field because it typically only ensures a protection up to 100 kHz. There is a need to optimize the shield in order to maintain its mechanical stability, maintain a sufficiently low R0 (R0 characterizes the quality of the shield when a direct current passes through the cable), ensure protection at high frequencies above the characteristic frequency of 1 MHz, and maintain the flexibility of the cable incorporating the shield. Summary of the Invention

[0004] The present invention provides a cable with optimized shielding performance.

[0005] To this end, the present invention proposes a high voltage cable for voltages greater than 48 volts, the cable comprising a central electrical conductor and a shielding layer surrounding the central conductor to form a tubular casing accommodating the conductor, the shielding layer comprising 84 to 216 strands wound helically around the central conductor with a pitch between 100 mm and 250 mm, inclusive, the cable thus having a characteristic frequency comprised between 1 MHz and 100 MHz.

[0006] The present invention is advantageously supplemented by the following features, either individually or in any technically feasible combination:

[0007] The shielding layer (3) comprises 59 to 836 strands, preferably 84 to 216 strands or 84 to 120 strands.

[0008] The diameter of the strands of the shielding layer (3) is between 0.08 mm and 0.22 mm, inclusive, or between 0.1 mm and 0.22 mm, or between 0.1 mm and 0.15 mm.

[0009] The shield comprises 120 strands wound in a helically fashion with a pitch of 250 mm, each strand having a diameter of 0.1 mm.

[0010] The shield comprises 84 strands wound in a helically fashion with a pitch of 250 mm, each strand having a diameter of 0.15 mm.

[0011] The shield comprises 216 strands wound in a helically fashion with a pitch of 250 mm, each strand having a diameter of 0.15 mm.

[0012] - It comprises a retaining structure (5) surrounding the shielding layer (3).

[0013] - The retaining structure consists of a retaining cord (51) or a retaining tape (52) wound in a spiral manner around the shielding layer (3).

[0014] The holding structure comprises two holding ropes (51) or two holding belts (52) or a combination of a crossed holding rope (51) and a holding belt.

[0015] The retaining rope or retaining belt is made of polyester, polyethylene, polypropylene, polyamide, aramid or glass fiber.

[0016] - It comprises a shielding screen made of an electrically conductive material, preferably an aluminium tape, wound in a spiral manner around the retaining structure (5) so as to completely cover the retaining structure (5).

[0017] The strands of the shielding layer are electrical conductors, preferably made of copper, aluminum or a composite material.

[0018] The outer diameter of the electrical conductor (2) is between 1 mm and 35 mm, preferably between 3 mm and 22 mm, preferably 4 mm.

[0019] The present description also relates to an electric cable comprising a central electrical conductor and a shielding layer surrounding the central conductor to form a tubular envelope containing the conductor, the shielding layer comprising a plurality of strands wound helically around the central conductor with a pitch greater than or equal to 100 mm so as to obtain a characteristic frequency greater than or equal to 1 MHz.

[0020] This example is advantageously supplemented by the following features, either individually or in any technically feasible combination:

[0021] - the winding pitch of the shielding layer is less than or equal to 1000 mm, preferably equal to 250 mm;

[0022] - The shield consists of 59 to 836 strands;

[0023] - the diameter of the strands of the shielding layer is between 0.08 mm (inclusive) and 0.22 mm (inclusive);

[0024] - the cable comprises a retaining structure surrounding the shielding layer;

[0025] - The retention structure consists of a retention cord or tape wrapped helically around the shield;

[0026] - The holding structure comprises two holding ropes or two holding belts or a combination of a crossed holding rope and a holding belt;

[0027] - the retaining rope or retaining belt is made of polyester, polyethylene, polypropylene, polyamide, aramid or glass fiber;

[0028] - the cable comprises a shielding screen wound in a spiral manner around the retaining structure so as to completely cover the retaining structure, the screen being made of a conductive material, preferably an aluminum tape;

[0029] - the strands of the shielding layer are electrical conductors, preferably made of copper, aluminum or a composite material;

[0030] The outer diameter of the electrical conductor is between 1 mm and 35 mm, preferably between 3 mm and 22 mm, preferably 4 mm.

[0031] Thus, the cable of the present invention provides better shielding than that obtained using braiding because it has a lower wire density, no crossing or interlacing between strands, thereby increasing bending strength, is faster to produce, and is easier to disassemble to simplify its recycling.

[0032] The wrapping or spiral winding of the strands for the shielding layer achieves the same cable shielding performance using less material than a braided cable.The use of less conductive materials such as aluminum, recycled materials or composite materials is therefore also conceivable.

[0033] Wrapping allows the shield dimensions to be optimized to get as close as possible to the target electromagnetic compatibility (EMC) benchmark. This has the effect of reducing the amount of shielding material required. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects and advantages of the present invention will appear from the following description, which is purely illustrative and non-limiting and should be read in conjunction with the accompanying drawings, in which:

[0035] - Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 shows a longitudinal view of a cable according to various embodiments of the present invention;

[0036] - Figure 5shows the transfer impedance (ohm / m) as a function of frequency for various cables #1, #2, #3, #4;

[0037] - Figure 6 The transfer impedance Zt (mΩ / m) on cable #2 is shown. The cable #2 has a 4 mm 2 Conductive cross-section of 100 mm with an aluminium strip subjected to successive bending with a radius of 3 times the cable diameter (3D) and then 5 times the cable diameter (5D) after irradiation;

[0038] - Figure 7 Shows the screen attenuation of the shield on cable #2, which has a 4 mm 2 Conductive cross-section with aluminum strips, subjected to successive bending with a radius of 3 times the cable diameter (3D) and then 5 times the cable diameter (5D) after cross-linking;

[0039] - Figure 8 The transfer impedance Zt (Ω / m) of cable #5 is shown. The cable #5 has a cross section of 35mm. 2 An electrical conductor having a shielding layer without a tape thereon, subjected to continuous bending with a radius of 5 times the cable diameter (5D) after cross-linking;

[0040] - Figure 9 The transfer impedance of the braid and wrap are compared with similar R0. It can be seen that at frequencies above 1 MHz, the curves remain relatively comparable and the shielding performance is therefore similar.

[0041] Similar components have the same reference numerals throughout the drawings. DETAILED DESCRIPTION

[0042] Figure 1 A longitudinal view of a shielded cable 1 according to a first embodiment is shown.

[0043] The cable 1 comprises an electric conductor 2 consisting of a conductive core 21 covered with an insulation 22 , and an electromagnetic shielding layer 3 surrounding the electric conductor 2 .

[0044] The shield 3 has a cylindrical shape, within which the conductor 2 extends along the axis of rotational symmetry X of the cable 1. The shape of the shield 3, and therefore the shape of the cable 1, defines an axial direction DA along which the axis of cylindrical symmetry X extends, as well as a radial direction DR. An outer jacket 4 surrounds the shield 3. The outer jacket 4 is made of an electrically insulating material, preferably a polymer (e.g., polyolefin, PET, etc.).

[0045] The conductive core 21 is made of a conductive material such as copper, and the outer sheath 4 is made of an electrically insulating material.

[0046] Advantageously, the conductive core 21 is composed of one or more conductive cores (copper, aluminum, CNT, SN and composite materials, etc.), individually insulated with a single or multiple layers of electrical insulating material 22 (such as XLPO, PE, PP, PET, RPET, etc.).

[0047] The electrical conductor 2 preferably has a circular geometry.

[0048] Furthermore, the outer diameter of the electrical conductor 2 is between 1 mm and 35 mm, preferably between 3 mm and 22 mm.

[0049] Alternatively, the conductive core 2 has a ring-shaped geometry.

[0050] The shielding layer 3 comprises metal strands 31, 32, 33, 34 wrapped or wound in a helical manner around the electrical conductor 2. The shielding layer 3 advantageously comprises 59 to 836 strands.

[0051] The wire strands 31 , 32 , 33 , 34 of the shielding layer 3 are advantageously bare electrical conductors (tinned copper or aluminum).

[0052] The helical geometry of the shielding layer 3 is advantageously defined so as to maintain efficient shielding at high frequencies, that is to say at frequencies above 100 kHz.

[0053] Preferably, the wrapping pitch (the distance between each turn of the helix, or the length of cable over which the helix completes one full rotation) is greater than or equal to 100 mm in order to obtain a characteristic frequency greater than 1 MHz. The characteristic frequency is the frequency at which the performance of the shielding sheath begins to deteriorate.

[0054] Preferably, the wrapping pitch is less than 1000 mm to ensure adequate mechanical retention between the shielding strands. In practice, the strands wound in a helical manner must move very little when the cable is bent and deformed.

[0055] Preferably, the number of strands is defined to achieve 100% wrap coverage. This ensures that the conductive component 2 is perfectly covered over its entire length, with the shielding layer 3 then being well distributed over the entire surface of the conductor 2. The shielding layer 3 preferably has a thickness between 0.08 mm and 0.22 mm. This thickness can be achieved with a single layer formed from strands preferably having a diameter between 0.08 mm and 0.22 mm, or with multiple layers, provided both layers have a thickness preferably between 0.08 mm and 0.22 mm.

[0056] In addition, the shielding layer 3 is adhered to the electrical conductor 2 via an adhesive layer (not shown). Such an adhesive layer is, for example, an adhesive.

[0057] Figure 2 A longitudinal view of a shielded cable 10 according to a second embodiment is shown.

[0058] In addition to the features of the first embodiment, the cable 10 comprises a retaining structure 5, which here comprises a retaining cord 51, for example made of polyester, which is wound in a helical manner around the shielding layer 3, but with a smaller pitch, such as Figure 2 This retaining structure 5 allows the strands of the shielding layer 3 to be held underneath, and in particular it allows the strands of the shielding layer 3 to be held against each other. Alternatively, the retaining structure is a polyester tape 52, such as Figure 4 shown.

[0059] The sheath 4 eventually covers the retaining structure 5 .

[0060] Figure 3 A longitudinal view of a shielded electrical cable 20 according to a third embodiment is shown.

[0061] In addition to the features of the second embodiment, this cable 20 includes a polyester retaining tape or aluminum shielding screen 6 surrounding the retaining structure 5. This screen or tape 6 is wound in a spiral around the underlying retaining structure 5 to completely cover it. In particular, it is wound by partially overlapping from one rotation to the next. It has a rectangular cross-section, preferably with a width between 1 mm and 10 mm.

[0062] Figure 4 A longitudinal view of a shielded electrical cable 30 according to a fourth embodiment is shown.

[0063] In addition to the features of the second embodiment, this cable 30 provides a retaining structure 5 that includes a retaining tape 52, for example, made of polyester, in addition to the polyester cord 51. The retaining tape 52 and the retaining cord 51 are spirally wound around the shield 3 in opposite directions so as to intersect. This helps retain the shield 3. The retaining tape 52 has a rectangular cross-section and is preferably between 1 mm and 10 mm wide.

[0064] Additionally, a cable may be provided as a combination of the third embodiment and the fourth embodiment.

[0065] Example

[0066] Various cables including the shielding layer 3 were manufactured and characterized.

[0067] Figure 5 The transfer impedance (ohm / m) as a function of frequency (in MHz) is shown for various cables #1, #2, #3, #4, the characteristics of which are shown in the table below.

[0068]

[0069] Transfer impedance is a measurement that characterizes shield performance. It indicates the voltage induced in an electrical conductor related to the current circulating in the shield. This measurement is performed according to the IEC 62153-4-16 standard.

[0070] exist Figure 5 In the diagram, it can be seen that for cables #2, #3, and #4 with a pitch of 250 mm, transfer impedances well below the gauge (the desired target) are achieved. In contrast, for a longitudinal strand lay (equivalent to infinite pitch) (cable #1), insufficient strands remain to ensure 100% coverage, and the transfer impedance is above the gauge. This gives an indication of the length of the pitch, which should not be too long.

[0071] It can also be seen that for a pitch of 250 mm, the addition of the retention structure 5 comprising both retention cord 51 and polyester retention tape 52 also improves the transfer impedance. Thus, the curve for cable #4 is lower than the curve for cable #3 (without polyester retention tape 52 but only polyester retention cord 51).

[0072] Figure 6 The transfer impedance Zt (mΩ / m) of cable #2 is shown. The cable #2 has a 4 mm 2 The core cross-section of the conductor is 100 mm, with a shielding screen 6 consisting of an aluminum tape wound helically with a pitch of 250 mm, after cross-linking and undergoing successive bends with a radius of 3 times the cable diameter (3D) and then 5 times the cable diameter (5D). It should be noted that cross-linking refers to the creation of new connections by bombardment. This is electron irradiation.

[0073] Figure 7 Shown is the screen attenuation (AS) of the shield 3 on cable #2 with a 4 mm 2 A core section of an electrical conductor of 1000 mm with an aluminium tape wound in a helically manner with a pitch of 250 mm, after cross-linking and subjected to successive bending with a radius of 3 times the cable diameter (3D) and then 5 times the cable diameter (5D).

[0074] Screen attenuation describes the effectiveness of shielding and is expressed in dB. It corresponds to the ratio between the power transmitted into the cable and the power radiated. This measurement is performed according to the IEC 62153-4-16 standard.

[0075] Figure 6 and Figure 7 It was shown that the shield does not degrade upon bending after cross-linking.

[0076] Figure 8 The transfer impedance Zt (Ω / m) on cable #5 is shown. The cable #5 has a 35mm 2An electrical conductor 2 of a core cross-section with a shielding layer 3 without a retaining tape or shielding screen (aluminum tape) after cross-linking and subjected to continuous bending with a radius of 5 times the cable diameter (5D).

[0077] The figure shows that as the cable is bent the shielding degrades. This therefore highlights the importance of the polyester retaining tape in its ability to retain the strands and provide 100% coverage without degrading the shielding.

[0078] Figure 9 The transfer impedances of the braid and wrap with similar R0 are compared for cable #2. It should be noted that at frequencies above 1 MHz, the curves remain relatively comparable, and the shielding performance is therefore similar.

[0079] Various cables having the characteristics shown in the table below were tested. In particular, a cable according to the invention, referred to as Shield, was compared with a prior art cable, referred to as Braid.

[0080]

[0081] 4mm with shielding 2 A flexibility of 9 N was measured on the conductive cross-section cable. This is better than the braided cable, which offers a flexibility of 10.3 N.

[0082] Similarly, the 35mm with shielding layer has a 49N compared to the 49N of braided cable. 2 An average flexibility of 33N was measured on the conductive cross-section cable.

[0083] It is also shown that wrapping reduces the weight of the shield compared to braiding while having an R0 comparable to braiding.

Claims

1. A high voltage cable (10, 20, 30) for voltages greater than 48 volts, the cable (1, 10, 20, 30) comprising a central electrical conductor (2) and a shielding layer (3) surrounding the central conductor (2) to form a tubular envelope containing the conductor (2), the shielding layer (3) comprising 84 to 216 strands (31, 32, 33, 34) wound helically around the central conductor (2) with a pitch between 100 mm and 250 mm, inclusive, the cable (1, 10, 20, 30) thereby having a characteristic frequency between 1 MHz and 100 MHz.

2. The cable (1, 10, 20, 30) according to claim 1, wherein The shielding layer (3) comprises 59 to 836 strands, preferably 84 to 216 strands or 84 to 120 strands.

3. The cable (1, 10, 20, 30) according to any one of claims 1 to 2, wherein The diameter of the strands of the shielding layer (3) is between 0.08 mm and 0.22 mm, inclusive, or between 0.1 mm and 0.22 mm, or between 0.1 mm and 0.15 mm.

4. The cable according to any one of claims 1 to 2, wherein The shielding layer comprises 120 strands wound in a helical manner with a pitch of 250 mm, each strand having a diameter of 0.1 mm.

5. The cable according to any one of claims 1 to 2, wherein The shield comprises 84 strands wound helically at a pitch of 250 mm, each strand having a diameter of 0.15 mm.

6. The cable according to any one of claims 1 to 2, wherein The shielding layer comprises 216 strands wound in a helical manner with a pitch of 250 mm, each strand having a diameter of 0.15 mm.

7. The cable (10, 20, 30) according to any one of claims 1 to 6, comprising a retaining structure (5) surrounding the shielding layer (3).

8. The cable (10, 20) according to claim 7, wherein The retaining structure (5) consists of a retaining rope (51) or a retaining belt (52) wound in a spiral manner around the shielding layer (3).

9. Cable (30) according to the preceding claim, wherein The holding structure (5) comprises two holding ropes (51) or two holding belts (52) or a combination of a crossed holding rope (51) and a holding belt (52).

10. The cable according to claim 8 and / or claim 9, wherein: The retaining rope or the retaining belt is made of polyester, polyethylene, polypropylene, polyamide, aramid or glass fiber.

11. The cable (20) according to any one of claims 7 to 10, comprising a shielding screen (6) wound in a spiral manner around the retaining structure (5) so as to completely cover the retaining structure (5), the screen being made of a conductive material, preferably an aluminum tape.

12. The cable (1, 10, 20, 30) according to any one of claims 1 to 11, wherein The strands (31, 32, 33, 34) of the shielding layer (3) are electrical conductors, preferably made of copper, aluminum or a composite material.

13. The cable (1, 10, 20, 30) according to any one of claims 1 to 12, wherein The outer diameter of the electrical conductor (2) is between 1 mm and 35 mm, preferably between 3 mm and 22 mm, preferably 4 mm.

Images