Coaxial twin-core high-voltage cable and method for manufacturing coaxial twin-core high-voltage cable

Abstract

The present disclosure relates to a coaxial dual core high voltage (HV) cable comprising a first extruded elongated hollow profile of conductive metal forming a first conductor, a second extruded elongated profile of conductive metal forming a second conductor, where the second conductor is coaxially disposed within the first conductor. A first electrically insulating layer is disposed between the first conductor and the second conductor and coats an outer surface of the second conductor and an inner surface of the first conductor, and a second electrically insulating layer coats an outer surface of the first conductor. The disclosure also relates to a method for manufacturing such a cable and to the use of such a cable.

Description

Technical Field

[0001] The present application relates to an internally and / or externally cooled coaxial twin-core high voltage cable and a method for manufacturing the cable. The present application also relates to an externally and / or internally cooled coaxial twin-core flat shaped high voltage cable and a method for manufacturing the flat shaped cable. The coaxial twin-core high voltage cable disclosed herein is particularly suitable for vehicles such as electric vehicles and hybrid electric vehicles. Background Art

[0002] High voltage (HV) cables for high voltage power transmission are used in various applications, such as ignition systems and alternating current (AC) or direct current (DC) power transmission. HV cables are also used in the field of hybrid electric vehicle (HEV) or electric vehicle (EV) technology, where the voltage power from the battery is amplified by an inverter and output to the drive motor via a large diameter high voltage power cable with sufficient current capacity.

[0003] The requirements for hybrid electric vehicles and electric vehicle technology and the development of said technology have led to an increase in the size of HV cables used as power cables due to higher voltages in power transmission. At high voltages, the conductive material tends to get very hot unless the cable has a sufficiently high diameter. In addition, there is a continuous effort to reduce the size of the engine compartment and reduce the weight of all components in the vehicle. Thus, there is a need for HV cables that allow the size and weight of components in the vehicle to be reduced. Summary of the invention

[0004] The object of the present invention is to provide a high voltage cable which is light in weight and saves space.

[0005] This object is achieved by the subject-matter of the attached independent claims.

[0006] According to a first aspect, the present disclosure relates to a coaxial twin-core high voltage (HV) cable, comprising a first extruded elongated hollow profile of conductive metal forming a first conductor, a second extruded elongated profile of conductive metal forming a second conductor, wherein the second conductor is coaxially arranged within the first conductor, and further comprising a first electrical insulation layer arranged between the first conductor and the second conductor and coating an outer surface of the second conductor and an inner surface of the first conductor, and wherein the second electrical insulation layer coats the outer surface of the first conductor.

[0007] The second conductor may be a solid rod or a hollow profile having at least one gap over its entire length.

[0008] The coaxial twinax HV cable may have a cross-sectional shape selected from standard circular, rounded, oval, flat oval (stadium), rectangular, oblong, square, or polygonal.

[0009] The coaxial twin-core HV cable may have a flat cross-sectional shape, wherein a first electrical insulation layer disposed between the first conductor and the second conductor is in direct contact with an outer surface of the second conductor and an inner surface of the first conductor, and wherein the first electrical insulation layer has a substantially uniform thickness.

[0010] The coaxial twin-core HV cable may further include at least one cooling channel for the flow of a cooling medium, wherein the at least one cooling channel is an extruded metal tube coaxially arranged within the at least one void of the second conductor, and a third electrical insulation layer is arranged between an outer surface of the at least one cooling tube and an inner surface of the at least one void of the second conductor.

[0011] The coaxial twin-core HV cable may include two cooling channels, wherein the cooling channels are a first cooling channel for flow of a cooling medium and a second cooling channel for return flow of the cooling medium.

[0012] The two cooling channels may be formed by a single extruded cooling tube having two parallel channels extending in the axial direction.

[0013] The two cooling channels may be formed by two separate extruded tubes extending in the axial direction.

[0014] The first conductor, the second conductor and the at least one cooling tube are made of a metal selected from aluminum, an aluminum alloy, copper or a copper alloy. Preferably, the first conductor, the second conductor and the at least one cooling tube are made of aluminum or an aluminum alloy.

[0015] In a preferred embodiment, the first conductor and / or the second conductor is made of an AA6XXX series alloy or an AA1XXX series alloy.

[0016] The material of the first electrically insulating layer and / or the second electrically insulating layer and / or the third electrically insulating layer may have a dielectric strength of 30-70 kV / mm.

[0017] The material of the second electrically insulating layer may have a dielectric strength of 15-30 kV / mm.

[0018] According to a second aspect, the present disclosure relates to a method for manufacturing the above-mentioned coaxial twin-core high voltage cable. The method comprises the following steps:

[0019] (i) providing a first extruded hollow profile of an electrically conductive metal and a second extruded profile of an electrically conductive metal, the second extruded profile having a diameter smaller than an inner diameter of a hollow portion of the first extruded hollow profile, and the second extruded profile being a solid rod or a hollow profile having at least one void throughout its length;

[0020] (ii) applying a coating layer of a first electrically insulating material onto an outer surface of the second extruded profile to obtain a coated second extruded profile having a first electrically insulating layer;

[0021] (iii) assembling the first extruded hollow profile and the second extruded profile by placing the coated second extruded profile within the first extruded hollow profile, and

[0022] (a) expanding the coated second extruded tube until the first electrically insulating layer directly contacts and covers the inner surface of the first extruded hollow profile, or

[0023] (b) reducing the diameter of the cross-section of the first extruded hollow profile until the first electrically insulating layer directly contacts and covers the inner surface of the first extruded hollow profile, or

[0024] (c) a combination of (a) and (b); and

[0025] (iv) applying a coating of a second electrically insulating material onto the outer surface of the first extruded hollow profile.

[0026] The method may comprise applying a second electrically insulating layer before or after step (iii).

[0027] The method may further comprise,

[0028] - providing at least one cooling tube, wherein the at least one cooling tube is an extruded metal tube;

[0029] - applying a coating layer of a third electrically insulating material onto the outer surface of the at least one cooling tube to obtain at least one coated cooling tube;

[0030] - placing the at least one coated cooling tube in a second extruded hollow profile having at least one void and performing one or both of the following:

[0031] - expanding the at least one coated cooling tube until the third electrically insulating layer on the outer surface of the at least one cooling tube directly contacts and covers the inner surface of the void of the second extruded hollow profile, or

[0032] - reducing the diameter of the cross section of the second extruded hollow profile until the third electrically insulating layer on the outer surface of the at least one cooling tube directly contacts and covers the inner surface of the void of the second extruded hollow profile.

[0033] The method may further comprise the step of flattening the cable.

[0034] The first extruded hollow profile, the second extruded profile and the at least one cooling tube are made of a metal selected from the group consisting of aluminum, an aluminum alloy, copper or a copper alloy, preferably aluminum or an aluminum alloy.

[0035] According to a third aspect, the present disclosure relates to the above-mentioned coaxial two-core high voltage (HV) cable for high voltage power transmission in a hybrid electric vehicle (HEV) or an electric vehicle (EV), or as a charging cable in a charging unit or charging station, or in a charging station infrastructure, or in an electric ship or a hybrid electric ship, or in a data center, or in a windmill or wind park, or in a PV system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1a Illustrated is a perspective view of a portion of a coaxial twinax HV cable in accordance with the present disclosure. For illustration purposes, the different layers of the cable are shown.

[0037] Figure 1b Graphical instructions Figure 1a Side view of the portion of the coaxial twincore HV cable.

[0038] Figure 1c Graphical instructions Figure 1a and Figure 1b Cross-sectional view of a coaxial twin-core HV cable.

[0039] Figure 2 Illustrated is a perspective view of a portion of a flat shaped coaxial twinax HV cable in accordance with the present disclosure.

[0040] Figure 3 The cross-sectional shape of a portion of a flat coaxial twinax HV cable in accordance with the present disclosure is illustrated.

[0041] Figure 4 ac illustrate perspective views of portions of different example embodiments of coaxial twin-core HV cables with internal cooling channels in accordance with the present disclosure.

[0042] Figure 5 Illustrated is a cross section of a flat formed coaxial twin-core HV cable with internal cooling channels in accordance with the present disclosure. DETAILED DESCRIPTION

[0043] In the following description, various examples and embodiments of the present invention are set forth to enable those skilled in the art to more thoroughly understand the present invention. The specific details described in the context of each embodiment and with reference to the accompanying drawings should not be interpreted as limiting. On the contrary, the scope of the present invention is defined in the appended claims.

[0044] Throughout the specification and claims, unless the context clearly dictates otherwise, the following terms take the meanings explicitly associated with this document. The phrase "in one embodiment" as used herein does not necessarily refer to the same embodiment, although it may refer to the same embodiment. In addition, the phrase "in another embodiment" as used herein does not necessarily refer to a different embodiment, although it may refer to a different embodiment. Therefore, as described below, the various embodiments of the present invention can be easily combined without departing from the scope of the present invention.

[0045] In addition, the term "or" as used herein is an inclusive "or" operator, equivalent to the term "and / or", unless the context clearly dictates otherwise. The term "based on" is not exclusive, and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a", "an", and "the" may include plural references. The meaning of "in..." includes "in..." and includes plural references. The meaning of "in..." includes "in..." and "on...".

[0046] The present disclosure aims to provide a light-weight, space-saving coaxial twin-core high-voltage cable (hereinafter also referred to as a "cable"). The cable is suitable for applications with a voltage of 600-1200V, such as in electric vehicles, however the cable can be used with other voltage ranges, such as up to 2500V or even higher. The cable has excellent internal and / or external cooling, thereby avoiding heat accumulation in the cable core. The cable is particularly suitable for installation in electric vehicles or hybrid electric vehicles. The cable is also suitable for connection to a charging cable in a charging unit or charging station, or for use in charging station infrastructure. Other suitable applications of the cable are electric vessels or hybrid electric vessels such as sea vessels, ships and boats, data centers, power windmills, PV systems and any other facilities requiring HV transmission cables.

[0047] Thus, the present disclosure relates to a coaxial twin-core high voltage (HV) cable, comprising a first extruded elongated hollow profile of conductive metal forming a first conductor (also indicated as "outer conductor"), a second extruded elongated profile of conductive metal forming a second conductor (also indicated as "inner conductor"), wherein the second conductor is coaxially arranged within the first conductor, and a first electrical insulation layer is securely arranged between the second conductor and the second conductor, coating the outer surface of the second conductor and the inner surface of the first conductor, and a second electrical insulation layer / jacket coats the outer surface of the first conductor. The provision of the first electrical insulation layer securely fixed between the inner conductor and the outer conductor, directly contacting the entire surface area of ​​the adjacent inner and outer conductors, results in a large surface contact area and excellent heat transfer between the inner and outer conductors. In addition, the first electrical insulation layer disposed between the inner and outer conductors is securely held in place, thereby allowing the cable to bend without compromising heat transfer capabilities or insulation properties. In addition, due to the concentric conductors, the coaxial twin-core HV cable does not require shielding or filters to minimize electromagnetic interference. The enhanced cooling and elimination of the need for a shielding layer allow for a smaller cable cross-sectional area compared to high voltage applications and capacities.

[0048] The expression "direct contact" etc. used herein in relation to the first electrically insulating layer arranged between the inner (second) conductor and the outer (first) conductor should be understood as the first electrically insulating layer contacting and covering the complete inner surface of the first (outer) conductor and the outer surface of the second (inner) conductor, preferably without any gap therebetween, including after any bending operation. It should be understood that the same applies to the disclosure relating to the third electrically insulating layer arranged between the at least one cooling tube and the inner conductor.

[0049] The conductive metal forming the outer (first) conductor and the inner (second) conductor can be selected from aluminum, aluminum alloys, copper or copper alloys. Preferably, the conductive metal is aluminum or an aluminum alloy because aluminum significantly reduces the weight of the cable compared to Cu. In addition, aluminum has a lower cost than Cu and may also be a more sustainable material choice. Particularly suitable aluminum alloys for the inner and outer conductors are AA6XXX series aluminum alloys and AA1XXX series aluminum alloys. In the present disclosure, references to AA1XXX series and AA6XXX series aluminum alloys refer to the nomenclature of the Aluminum Association, which uses a four-digit system for wrought alloy composition families (see "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys" by the Aluminum Association).

[0050] Coaxial twin-core HV cables can have a cross-sectional shape that is generally standard round, round, oval, flat oval (stadium or pill shape), rectangular, oblong, square, or polygonal. The generally flat shape of the cable is advantageous because the large surface area of ​​the flat cable results in better heat dissipation (external cooling, "passive" cooling) compared to round or non-flat cables. Thus, the flat cable can reduce the volume and overall weight of the cable. The generally flat shape is also advantageous for placement and stacking of the cables because less space is required.

[0051] The first electrically insulating layer is made of a non-conductive material that can properly withstand bending and properly has sufficient dielectric strength to prevent current from passing between the inner conductor and the outer conductor. The material of the first electrically insulating layer preferably has a dielectric strength of 30-70 kV / mm, more preferably at least 40 kV / mm. Therefore, the first electrically insulating layer can be made relatively thin to allow effective heat transfer from the inner conductor while providing sufficient electrical insulation. The material of the first electrically insulating layer can be a polymer material, such as polyethylene or polyamide, such as PA12, etc., which has sufficient dielectric strength and can therefore be made thin enough to provide effective heat transfer from the inner conductor to the outer conductor. Other advantageous properties of the first electrically insulating layer material are good adhesion properties and flame retardancy as well as good thermal conductivity.

[0052] It is important to avoid short circuits and damage to equipment and personnel. Thus, the first electrically insulating layer should preferably cover and contact the entire outer surface of the inner conductor without any gaps, and should preferably also contact the entire inner surface of the outer conductor. It should be understood that a portion of the end of the inner conductor may not be covered by the electrically insulating layer to allow electrical connection to the connection point. Advantageously, the first electrically insulating layer is first applied to the inner conductor, and then the inner conductor is inserted into the outer conductor, followed by enlarging the inner conductor, or reducing the diameter of the cross-section of the outer conductor, as described in more detail below. The material of the electrically insulating layer can be applied so as to obtain a permanent adhesion between the inner conductor and the insulating layer, such as chemical adhesion, for example by applying a primer or glue to the surface of the inner conductor before applying the insulating layer, or any other suitable pretreatment.

[0053] High voltage cables need to be insulated outwardly to prevent the conductor from contacting other objects or people. Thus, the cable includes a second electrical insulation layer arranged on the outer surface of the outer conductor to prevent undesired short circuits and other injuries. The material of the second electrical insulation layer is appropriately a non-conductive polymer material and may have a dielectric strength lower than that of the material of the first electrical insulation layer, such as 15-30 kV / mm or 20-25 kV / mm. The material of the second electrical insulation layer may have a higher dielectric strength, for example, the material of the second electrical insulator may be the same as the first insulation layer. The requirement for good heat transfer of the outer conductor may not be so high, so the material of the second electrical insulation layer may have a thickness higher than that of the first electrical insulation layer. For example, the second electrical insulation layer may be made of a polymer material, such as polyethylene, such as XLPE, which has a much lower cost than a material with a higher dielectric strength. The second electrical insulation layer is preferably not permanently adhered to the surface of the conductor so that it can be stripped off, thereby making an electrical connection.

[0054] The ends of the inner and outer conductors may be shaped to form a single connecting piece.In a preferred embodiment, the connecting piece is integral with the conductors of the cable.

[0055] According to a first embodiment, a coaxial twin-core HV cable according to the present disclosure has a flat cross-sectional shape. The flat shape of the cable cross section is advantageous because the flat form provides better heat dissipation due to the larger surface area relative to the cross-sectional area of ​​the conductor. The flat cable can have a substantially rectangular, oval or flat oval (stadium shape) cross section. The term "flat" should be understood to include a cable cross-sectional shape having a ratio of the transverse direction (width w) to the height h greater than 1. The ratio w / h should preferably be at least 1.5, or at least 2, such as 2-8 or 4-7. The outer conductor (first conductor) is composed of an elongated hollow extruded profile (first extruded profile). The inner conductor can be composed of a solid or hollow extruded profile (second extruded profile). The cross-sectional shapes of the first extruded profile and the second extruded profile should preferably correspond, so that the second extruded profile fits in the longitudinal hollow of the first extruded profile, and the first electrical insulation layer arranged between the two profiles completely covers the outer surface of the inner conductor and the inner surface of the outer conductor, and is locked in place by the outer surface of the inner conductor and the inner surface of the outer conductor. In addition, the thickness of the first electrical insulation layer is substantially uniform over the entire length of the straight cable. The flat cable shape can be obtained by flattening (squashing) an assembly of an inner conductor and an outer conductor with an insulating layer arranged therebetween. Flattening can be obtained by rolling, pressing, drawing or any other suitable method. In an embodiment, the inner conductor is made of an extruded hollow profile having a cross-sectional shape corresponding to the outer conductor. This embodiment can facilitate the manufacture of the conductor assembly and the flattening process. By the flattening process, when the hollow profile is compressed, the inner conductor can obtain a strip shape. The flat cable includes an insulating layer / sheath on the outer surface of the outer conductor. The outer insulating layer / sheath can be applied before or after flattening of the conductor assembly.

[0056] It should be understood that the coaxial twin-core HV cable can have a flat shape in one or more portions of the longitudinal length of the cable, so the cross-sectional shape of the cable can vary along the longitudinal length. Different cross-sectional shapes along the length of the cable can have the advantage of facilitating the placement and installation of the cable.

[0057] The conductive metal, the first electrically insulating material and the second insulating material for the outer conductor and the inner conductor according to the first embodiment are the same as described above.

[0058] In a second embodiment, a coaxial twin-core HV cable according to the present disclosure may include at least one internal cooling channel for passing a cooling medium through the interior of the cable, thereby achieving cooling of the cable. In this second embodiment, the inner (second) conductor is composed of an extruded elongated hollow profile having at least one hollow void throughout its length. As described above, the outer (first) conductor is composed of an extruded hollow elongated profile. The first electrical insulation layer is arranged between the inner conductor and the outer conductor, completely covering the outer surface of the inner conductor and the inner surface of the outer conductor in a corresponding manner as described above. The thickness of the first insulation layer is substantially uniform and is firmly held in place by the inner conductor and the outer conductor. The at least one cooling channel is arranged in at least one void of the inner (second) conductor, extending in the longitudinal direction of the cable. The electrical insulation layer represented herein as the third electrical insulation layer is arranged between the outer surface of the at least one cooling channel and the inner surface of the void of the hollow inner conductor.

[0059] Due to the excellent heat transfer performance and the impermeability of gases and liquids in the metal, the at least one cooling channel (also referred to herein as cooling tube) is preferably made of an extruded metal tube. The cooling tube can advantageously be made of aluminum, an aluminum alloy, copper or a copper alloy. Since aluminum and aluminum alloys are light in weight and relatively low in cost compared to copper, it is preferred that the at least one cooling tube is made of aluminum or an aluminum alloy. Suitable aluminum alloys for cooling tubes can be, for example, AA3XXX series alloys, such as AA3003. The alloy for cooling tubes preferably should have good drawability. The alloy preferably also should have acceptable corrosion resistance.

[0060] The at least one cooling channel may be an extruded aluminum tube having two or at least two channels extending in parallel in the longitudinal direction, in which the cooling medium may flow in the same or opposite directions. Alternatively, the at least two cooling channels may be composed of two or more cooling tubes arranged in the inner conductor so that the cooling medium flows in the same or opposite directions. In the example of two separate cooling tubes, the inner conductor may have two longitudinal hollow portions extending over the entire length of the profile to accommodate the cooling tubes. A single cooling tube or two separate cooling tubes with two channels makes it possible to use a single connector to supply and collect the cooling fluid / medium, because the cooling fluid can be introduced and discharged from the same end of the cable. In such an embodiment, the other end of the cooling channel may be closed by a capping device for guiding the cooling medium to flow from the inlet channel to the return channel. The at least one cooling channel may have a length greater than that of the inner conductor and the outer conductor. In addition, the at least one cooling channel may be equipped with a device that allows the cooling medium / fluid to be quickly connected to the cooling tube, or be shaped in a manner that allows the cooling medium / fluid to be quickly connected to the cooling tube. Preferably, the outer surface of the at least one cooling channel extending from the cable is completely covered / insulated by a third electrical insulation layer or other suitable insulating covering.

[0061] The third electrical insulating layer is made of a non-conductive material, which can properly withstand bending and properly has enough dielectric strength to prevent current from passing between the at least one cooling channel and the inner conductor. The material of the third electrical insulating layer can have a dielectric strength of 30-70 kV / mm, preferably at least 40 kV / mm. Therefore, the third electrical insulating layer can be made relatively thin to allow effective cooling of the inner conductor and the outer conductor while providing enough electrical insulation. The material of the third electrical insulating layer can be a polymer material, such as polyethylene or polyamide, such as PA12, etc., which has enough dielectric strength, so it can be made thin enough to provide effective cooling of the coaxial twin-core HV cable. The third electrical insulating layer should preferably cover and contact the entire outer surface of the at least one cooling channel without any gap, and preferably also contact the entire inner surface of the inner conductor. Other advantageous properties of the third electrical insulating layer material are good adhesion and flame retardancy and good thermal conductivity.

[0062] Advantageously, the third electrically insulating layer is first applied to the at least one cooling tube, which is then inserted into the hollow portion of the inner conductor, and then the at least one cooling tube is enlarged, or the cross section of the inner conductor is reduced, as described in more detail below. The material of the third electrically insulating layer may be applied so as to obtain a permanent adhesion between the cooling tube and the insulating layer, such as a chemical adhesion, for example by applying a primer or glue to the surface of the cooling tube before applying the insulating layer, or any other suitable pretreatment.

[0063] Due to the enhanced external cooling and / or internal cooling, the high voltage twin core cable of the present disclosure may have a smaller cross-sectional area than a solid non-cooled high voltage cable for corresponding voltage applications. Thus, for any construction or configuration as defined above, the cable may have, for example, 70-500 mm 2 For example, for the same voltage application, the cross-sectional area is 70-120 mm 2 The external or internal cooling cable will correspond to a cross-sectional area of ​​approximately 200-250 mm 2 The cooling tube may suitably have an outer diameter of 6-10 mm. Due to the smaller diameter and internal space, costs and weight can be greatly reduced. It should be understood that other cross-sectional areas and dimensions can be achieved for different applications. In this context, the cable cross-sectional area refers to the cross-sectional area of ​​the conductor.

[0064] Typical operating ambient temperature is approximately 125°C.

[0065] Due to the preferred choice of extruded metal profiles used as internal cooling tubes and conductors, the high voltage cable of the present disclosure may not be generally flexible. Thus, it may be necessary to use a bending tool to bend the cable into its final shape.

[0066] The present disclosure also relates to a method for manufacturing the above-mentioned coaxial dual-core high-voltage cable. The method comprises the following steps:

[0067] - providing a first elongated extruded hollow profile of an electrically conductive metal and a second elongated extruded profile of an electrically conductive metal, wherein the outer diameter of the second extruded profile is smaller than the inner diameter of the hollow portion of the first extruded hollow profile, and the second extruded profile (3) is a solid rod or a hollow profile having at least one void over its entire length;

[0068] - applying a coating layer of a first electrically insulating material onto an outer surface of the second extruded profile to obtain a coated second extruded profile having the first electrically insulating layer thereon;

[0069] - placing the coated second extruded profile within the hollow portion of the first extruded hollow profile, and

[0070] (i) expanding the coated second extruded profile until the first electrically insulating layer completely covers the inner surface of the first extruded hollow profile, or

[0071] (ii) reducing the cross-section of the first extruded hollow profile until the first electrically insulating layer completely covers the inner surface of the first extruded hollow profile;

[0072] (iii) or a combination of methods (i) and (ii), and

[0073] - Applying a coating of a second electrically insulating material to the outer surface of the first extruded hollow profile.

[0074] The reduction of the cross section of the hollow profile may be performed by cold working, such as hammering, pressing, roll forming, drawing or other methods known to those skilled in the art.

[0075] The second extruded profile may be a solid profile or a hollow profile having at least one void over the entire length. The cross-sectional shape of the first extruded hollow profile, in particular the cross-sectional shape of the longitudinal hollow void of the first extruded hollow profile, should preferably correspond to the outer cross-sectional shape of the second extruded profile. By having corresponding cross-sectional shapes of the first profile and the second profile, the assembly of the extruded profiles will be facilitated.

[0076] The first electrically insulating layer may be applied to the outer surface of the second extruded profile by any suitable method, such as co-extrusion, powder coating, use of an adhesive, or other methods known to those skilled in the art. The material of the first electrically insulating layer may be applied so as to obtain a permanent adhesion between the inner conductor and the insulating layer, such as chemical adhesion, for example by applying a primer or glue to the surface of the inner conductor before applying the insulating layer, or any other suitable pretreatment. It should be understood that a portion of one or both ends of the inner conductor may not be coated to make an electrical connection.

[0077] The second electrically insulating layer may be applied to the outer surface of the first extruded profile by any suitable method, which may correspond to the method described above for applying the first electrically insulating layer. Thus, the method of applying the second electrically insulating layer may include co-extrusion, powder coating or other suitable methods. The application of the second insulating layer on the outer surface of the first extruded hollow profile may be performed before or after the assembly of the first extruded hollow profile and the second extruded profile.

[0078] The assembly of the first extruded profile and the second extruded profile includes placing the coated second extruded profile in the longitudinal hollow portion of the first extruded hollow profile. Thereafter, at least one of the profiles is deformed so that the first electrical insulation layer is firmly in contact with the inner surface of the first extruded hollow profile (outer conductor) and the outer surface of the second extruded profile (inner conductor). If the coated second extruded profile is a hollow profile, the deformation can be obtained by expanding the coated second extruded profile until the first electrical insulation layer completely and firmly contacts and covers the inner surface of the first extruded hollow profile. The expansion of the profile can be achieved by methods known to those skilled in the art, such as core drawing and hydraulic forming. Alternatively, the deformation can be obtained by reducing the cross-section of the first extruded hollow profile until the first electrical insulation layer completely and firmly contacts and covers the inner surface of the first extruded hollow profile. The reduction in cross section can be achieved by any method known to those skilled in the art, preferably by cold working, such as hammering, pressing, roll forming or drawing. It should be understood that deformation caused by expansion and reduction of the cross section is also possible.

[0079] In a first embodiment of the method, the method relates to the manufacture of a flat-shaped coaxial twin-core HV cable. The method for manufacturing a flat-shaped cable may involve the use of a first extruded profile and a second extruded profile having a substantially rectangular or oval or flat oval (stadium-shaped) cross-sectional shape. The assembly of the extruded profiles can be performed as described above. Another method for manufacturing a flat-shaped coaxial twin-core HV cable may include assembling the extruded profiles as described above, and then the assembly undergoes flattening deformation. In this method, it is preferred that the second extruded profile constituting the inner conductor is a hollow profile, such as a tube. During flattening deformation, the inner hollow profile (inner conductor) will be flattened to obtain a strip shape, while the outer conductor surrounds the inner conductor, and the first electrical insulation layer remains in place during the flattening process. Flattening can be obtained by rolling, pressing, drawing or any other suitable method known to those skilled in the art. The insulating layer / sheath can be applied on the outer surface of the outer conductor before or after flattening of the conductor assembly.

[0080] In a second embodiment of the method, the method further comprises

[0081] (a) providing at least one cooling channel, wherein the at least one cooling channel is one or more extruded metal tubes;

[0082] (b) applying a coating of a third electrically insulating material to an outer surface of the at least one cooling channel to obtain at least one coated cooling channel; and

[0083] (c) placing the at least one coated cooling channel within the longitudinal void of the second extruded hollow tube, and

[0084] - expanding the at least one coated cooling channel until the third electrically insulating layer on the outer surface of the at least one cooling channel contacts and completely covers the inner surface of the hollow void of the second extruded tube, or

[0085] - reducing the cross-section of the second extruded tube until the third electrically insulating layer on the outer surface of the at least one cooling channel contacts and completely covers the inner surface of the hollow void of the second extruded tube, or a combination of enlarging and reducing the cross-section.

[0086] The at least one cooling channel is preferably an extruded tube of aluminium or an aluminium alloy.

[0087] Advantageously, the at least one coated cooling channel is assembled with the inner conductor by enlarging the cooling channel. The enlarging can be performed, for example, by core drawing or hydroforming.

[0088] Furthermore, a second embodiment of the method involves placing the assembly of the inner conductor and the at least one cooling channel in a longitudinal hollow portion of the first extruded profile (outer conductor) and reducing the cross-section of the outer conductor until the inner surface of the hollow space contacts and is completely covered by the first electrically insulating layer on the outer surface of the inner conductor.

[0089] Example Embodiments

[0090] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the present disclosure are shown. However, the present disclosure may be embodied in other forms and should not be construed as being limited to the embodiments disclosed herein. The disclosed embodiments are provided in order to fully convey the scope of the present disclosure to those skilled in the art. It should be understood that the dimensions and dimensional ratios in the accompanying drawings are merely illustrative and should not be construed as limiting.

[0091] In the drawings, like reference numerals refer to like parts throughout the various drawings unless otherwise specified.

[0092] Figures 1 ac show a coaxial twin-core HV cable 1, which includes an outer hollow conductor 2, an inner conductor 3 arranged inside the hollow outer conductor 2, and a first electrical insulation layer 4 arranged between the inner conductor 3 and the hollow outer conductor 2, wherein the first electrical insulation layer 4 is in direct contact with the entire outer surface of the inner conductor 3 and the entire inner surface of the hollow outer conductor tube 2. In the example shown in the diagram, the cable includes a second electrical insulation layer 5 arranged on the outer surface of the hollow outer conductor 2. For illustration purposes, Figure 1a and Figure 1b Each layer of the cable is cut through. Figure 1c A cross section of the cable is shown, illustrating a solid conductor 3 coaxially arranged within an outer hollow conductor 2, and a first electrical insulation layer 4 arranged between the inner and outer conductors. The outer surface of the outer conductor 2 has a sheathing layer of an electrical insulation layer 5.

[0093] Figure 2A perspective view of a flat shaped coaxial twin-core HV cable 1 is shown, the cable comprising an outer hollow conductor 2, an inner conductor 3 arranged in the hollow outer conductor 2, and a first electrical insulation layer 4 arranged between the inner conductor 3 and the hollow outer conductor 2, wherein the first electrical insulation layer 4 is in direct contact with the entire outer surface of the inner conductor 3 and the entire inner surface of the hollow outer conductor tube 2. In the example shown in the diagram, the cable comprises a second electrical insulation layer 5 arranged on the outer surface of the hollow outer conductor 2. The outer conductor 2 and the inner conductor 3 are made of extruded metal tubes, assembled as described above, and then undergo a flattening process until the inner tube is completely flattened. After the tube assembly is flattened, the first electrical insulation layer 4 is in direct contact with the entire outer surface of the inner conductor 3 and the entire inner surface of the hollow outer conductor tube 2. For illustration purposes, each layer of the cable is cut. The flat cable 1 has a high surface area, which results in an enhanced cooling effect compared to a non-flat cable. In addition, the height of the flat cable is low compared to a circular shape with an equal cross-sectional area.

[0094] Figure 3 An alternative cross-sectional shape of a flat coaxial twin-core HV cable 1 is shown, wherein the inner conductor 3 is a solid extruded profile.

[0095] Figure 4 a-c show perspective views of different exemplary embodiments of a coaxial twin-core HV cable 1 with internal cooling channels 6, 6'. Corresponding to the cable in Fig. 1, the cable 1 comprises an outer hollow conductor 2 and an inner hollow conductor 3 arranged inside the hollow outer conductor 2, and a first electrical insulation layer 4 is arranged between the inner conductor 3 and the hollow outer conductor 2, wherein the first electrical insulation layer 4 is in direct contact with the entire outer surface of the inner conductor 3 and the entire inner surface of the hollow outer conductor tube 2. In the example shown in the diagram, the cable comprises a second electrical insulation layer 5 arranged on the outer surface of the hollow outer conductor 2. Figure 4 a illustrates a coaxial twin-core HV cable 1, wherein the inner conductor includes two separate D-shaped hollow portions extending along the entire length of the cable 1. Each D-shaped port has a D-shaped cooling tube 7, 7' arranged therein, thereby forming two separate cooling channels 6, 6' for the flow and return of a cooling medium. A third electrical insulation layer 8, 8' is arranged between the inner conductor 3 and the cooling tube 7, 7', wherein the third electrical insulation layer 8, 8' is in direct contact with the entire outer surface of the cooling tube 7, 7' and the entire inner surface of the hollow portion of the inner conductor tube 3. Figure 4 b shows Figure 4 a, in which the cooling tubes 7, 7' are round tubes, and correspondingly, the port in the inner conductor 3 is round. Figure 4 c illustrates a single circular cooling tube 7 which is divided into two cooling channels 6, 6' by the inner wall, so that each cooling channel is D-shaped. Correspondingly, the hollow portion in the inner conductor has a circular shape. Figure 4 In each of the examples shown in ac, the cooling tube 7, 7' is made of metal, preferably extruded aluminum tube.

[0096] Figure 5 An alternative cross section of a flat formed coaxial twin core HV cable 1 with internal cooling channels is shown. The flat form of the cable 1 also comprising internal cooling channels has effective cooling both from the outside due to the increase in surface area and from the inside due to active cooling.

Claims

1. A coaxial twin-core high voltage (HV) cable (1), comprising: - a first extruded elongated hollow profile of electrically conductive metal forming a first conductor (2); - a second extruded elongated profile of electrically conductive metal forming a second conductor (3), said second conductor (3) being arranged coaxially within said first conductor (2); - a first electrical insulation layer (4) arranged between the first conductor (2) and the second conductor (3) and coating the outer surface of the second conductor (3) and the inner surface of the first conductor (2); and - a second electrically insulating layer (5) coating the outer surface of the first conductor (2).

2. The coaxial twin-core HV cable (1) according to claim 1, wherein the second conductor (3) is a solid rod or a hollow profile having at least one gap over its entire length.

3. A coaxial twin-core HV cable (1) according to claim 1 or 2, wherein the cable (1) has a cross-sectional shape selected from standard round, circular, oval, flat oval (stadium), rectangular, oblong, square or polygonal.

4. A coaxial twin-core HV cable (1) according to claim 2 or 3, wherein the cable (1) has a flat cross-sectional shape, and the first electrical insulation layer (4) arranged between the first conductor (2) and the second conductor (3) is in direct contact with the outer surface of the second conductor (3) and the inner surface of the first conductor (2), and has a substantially uniform thickness.

5. The coaxial twin-core HV cable (1) according to any one of claims 1 to 4, further comprising at least one cooling channel (6, 6') for the flow of a cooling medium, wherein the at least one cooling channel (6, 6') is an extruded metal tube (7, 7') coaxially arranged in the at least one gap of the second conductor (3), and has a third electrical insulation layer (8, 8') arranged between the outer surface of the at least one cooling tube (7, 7') and the inner surface of the at least one gap of the second conductor (3).

6. The coaxial twin-core HV cable (1) according to claim 5, comprising two cooling channels (6, 6'); the cooling channels (6, 6') are a first cooling channel (6, 6') for the flow of a cooling medium, and Second cooling channel (6, 6') for return flow of cooling medium.

7. Coaxial twin-core HV cable (1) according to claim 6, wherein the two cooling channels (6, 6') are formed by a single extruded cooling tube (7) having two parallel channels extending in the axial direction.

8. The coaxial twin-core HV cable (1) according to claim 6, wherein the two cooling channels are formed by two separate extruded tubes (7, 7') extending in the axial direction.

9. The coaxial twin-core HV cable (1) according to any one of claims 1 to 8, wherein the first conductor (2) and the second conductor (3) and the at least one cooling tube (7, 7') are made of a metal selected from aluminum, an aluminum alloy, copper or a copper alloy.

10. The coaxial twin-core HV cable (1) according to claim 9, wherein the first conductor (2) and / or the second conductor (3) is made of AA6XXX series alloy or AA1XXX series alloy.

11. The coaxial twin-core HV cable (1) according to any one of claims 1 to 10, wherein the material of the first electrical insulation layer and / or the second electrical insulation layer and / or the third electrical insulation layer has a dielectric strength of 30-70 kV / mm.

12. Coaxial twin-core HV cable (1) according to any one of claims 1 to 10, wherein the material of the second electrical insulation layer has a dielectric strength of 15-30 kV / mm.

13. A method for manufacturing a coaxial two-core high-voltage cable (1) according to any one of the preceding claims 1 to 12, the method comprising the following steps: (i) providing a first extruded hollow profile (2) of a conductive metal and a second extruded profile (3) of a conductive metal, wherein the diameter of the second extruded profile (3) is smaller than the inner diameter of the hollow portion of the first extruded hollow profile (2), and the second extruded profile (3) is a solid rod or a hollow profile having at least one void throughout its entire length; (ii) applying a coating layer (4) of a first electrically insulating material onto the outer surface of the second extruded profile (3) to obtain a coated second extruded profile having a first electrically insulating layer (4); (iii) assembling the first extruded hollow profile (2) and the second extruded profile (3) by placing the coated second extruded profile (3) within the first extruded hollow profile (2), and (a) expanding the coated second extruded tube (3) until the first electrically insulating layer (4) directly contacts and covers the inner surface of the first extruded hollow profile (2), or (b) reducing the diameter of the cross section of the first extruded hollow profile (2) until the first electrically insulating layer (4) directly contacts and covers the inner surface of the first extruded hollow profile (2), or (c) a combination of (a) and (b); (iv) applying a coating layer (5) of a second electrically insulating material onto the outer surface of the first extruded hollow profile (2).

14. The method according to claim 13, wherein the step of applying the second electrically insulating layer (5) is performed before or after step (iii).

15. The method according to claim 13 or 14, further comprising: - providing at least one cooling tube (7, 7'), said at least one cooling tube being an extruded metal tube; - applying a coating layer (8) of a third electrically insulating material on the outer surface of the at least one cooling tube (7, 7') to obtain at least one coated cooling tube (7, 7'); - placing the at least one coated cooling tube (7, 7') in the second extruded hollow profile (3) having at least one void and performing one or both of the following: - expanding the at least one coated cooling tube (7, 7') until the third electrically insulating layer (8) on the outer surface of the at least one cooling tube directly contacts and covers the inner surface of the void of the second extruded hollow profile (3), or - reducing the diameter of the cross section of the second extruded hollow profile (3) until the third electrically insulating layer (8) on the outer surface of the at least one cooling tube (7, 7') directly contacts and covers the inner surface of the void of the second extruded hollow profile (3).

16. The method according to any one of claims 13-15, further comprising flattening of the cable (1).

17. The method according to any one of claims 13 to 16, wherein the first extruded hollow profile (2), the second extruded profile (3) and the at least one cooling tube (7, 7') are made of a metal selected from the group consisting of aluminum, an aluminum alloy, copper or a copper alloy, preferably aluminum or an aluminum alloy.

18. Use of a coaxial two-core high voltage (HV) cable (1) according to any one of claims 1 to 12 for high voltage power transmission in a hybrid electric vehicle (HEV) or an electric vehicle (EV), or as a charging cable in a charging unit or charging station, or in a charging station infrastructure, or in an electric ship or hybrid electric ship, or in a data center, or in a windmill or windmill park, or in a PV system.

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