Power cable
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOTOKU INC
- Filing Date
- 2025-01-22
- Publication Date
- 2026-08-03
AI Technical Summary
【0012】 本発明によれば、突入電流などの過度電流に起因する導体発熱を速やかに冷却可能な冷却構造を有する電力ケーブルが実現できる。
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Figure 2026125157000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a power cable for power supply.
Background Art
[0002] Conventionally, a power supply cable provided with a cooling pipe has been proposed (Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-18748). Also, a coaxial cable in which a refrigerant flows through a void portion formed in a hollow core body has been proposed (Patent Document 2: Japanese Unexamined Patent Application Publication No. 2015-100188).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the power supply cable described in Patent Document 1, since the cooling pipe is provided at the center of the power line, it is impossible to sufficiently secure the cross-sectional area required for cooling the conductor heat generation during energization. Also, since the cross-section is a non-axisymmetric shape, it has less flexibility than the coaxial cable having an axisymmetric shape such as that of Patent Document 2.
[0005] In order to shorten the power supply time to an electric vehicle, it is necessary to increase the amount of electric power flowing through the conductor. On the other hand, when the amount of electric power is increased, the conductor heat generation increases, and when the conductor heat generation becomes excessive, there is a problem that the outer covering melts and the insulation performance cannot be maintained.For example, due to an excessive current such as an inrush current, the conductor heat generation may temporarily increase and exceed the heat resistance temperature of the hollow core body.
[0006] The present invention has been made in view of the above circumstances, and aims to provide a power cable having a heat-resistant structure that can withstand conductor heating caused by excessive currents such as inrush currents, while also having a cooling structure that can quickly cool the conductor heating. [Means for solving the problem]
[0007] The power cable according to the present invention comprises a stranded wire and an outer sheath that insulates the stranded wire, the outer sheath comprising an inner annular portion, three or more rib portions extending radially from the inner annular portion, and an outer annular portion connected to the outer end of the rib portion, the flow channels enclosed by the inner annular portion, the rib portion and the outer annular portion being formed in the same number as the rib portion, the stranded wire being an assembly of individual wires with an insulating layer formed on the outer circumference of a metal wire, and having voids, the voids comprising an outer void portion formed on the outside of the stranded wire and an inner void portion formed on the inside of the stranded wire, and the configuration is characterized in that a coolant is flowed through the flow channels and the voids to suppress the temperature rise when energized.
[0008] With this configuration, a cooling channel is provided in the outer casing, and a cooling void is provided inside the inner annular section. This ensures sufficient cross-sectional area for cooling the heat generated by the conductor when energized, and allows for direct cooling where the refrigerant comes into contact with the stranded wire and absorbs heat. As a result, the cooling efficiency is dramatically improved.
[0009] The void ratio of the void portion is preferably 27 to 35%. The void ratio is expressed as a percentage of the cross-sectional area of the void portion to the inner cross-sectional area of the inner annular portion. The void ratio can be calculated using the sum of the outer void cross-sectional area formed by the stranded wire and the inner annular portion and the inner void cross-sectional area formed inside the stranded wire. By setting the void ratio to 27% or more, the stranded wire can be sufficiently cooled. By setting the void ratio to 35% or less, sufficient power can be supplied to the stranded wire.
[0010] The aforementioned stranded wire is preferably a rope twist. Rope twisting provides excellent shape stability. Furthermore, since the void is formed in a spiral shape, sufficient surface area and volume of the void through which the refrigerant flows can be secured.
[0011] This configuration offers excellent flexibility while easily accommodating power supply methods with currents of 300A or more, power supply methods with a power of 3000VA, and known charging standards such as CHAdeMO and SAE. As an example, the power cable according to the present invention constitutes a power supply line from the power supply unit to the battery in an electric vehicle. [Effects of the Invention]
[0012] According to the present invention, a power cable having a cooling structure capable of rapidly cooling conductor heat generated by excessive currents such as inrush current can be realized. [Brief explanation of the drawing]
[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a power cable according to this embodiment. [Figure 2] Figure 2 is a schematic diagram illustrating an example of the power cable shown in Figure 1. [Figure 3] Figure 3A schematically shows the arrangement of the voids when the final strand of the stranded wire is 3 strands. Figure 3B schematically shows the arrangement of the voids when the final strand of the stranded wire is 4 strands. Figure 3C schematically shows the arrangement of the voids when the final strand of the stranded wire is 5 strands. Figure 3D schematically shows the arrangement of the voids when the final strand of the stranded wire is 6 strands. [Figure 4] Figure 4 is a schematic diagram showing an example of the application of a power cable according to this embodiment. [Modes for carrying out the invention]
[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. As an example, the power cable 1 according to this embodiment constitutes a power supply line from the power supply unit 51a to the battery 51b in an electric vehicle 51, as shown in Figure 4. Connectors for external connection are attached to both ends of the power cable 1. The coolant flows through the cable via the connectors. In all the figures used to explain the embodiments, components having the same function are denoted by the same reference numerals, and repeated explanations may be omitted.
[0015] [Power Cables] As shown in Figure 1, the power cable 1 of this embodiment comprises stranded wire 2 and an outer sheath 4 that insulates the stranded wire 2. The outer sheath 4 is made of a thermoplastic resin with an integral structure comprising an inner annular portion 4a, three or more rib portions 4b extending radially from the inner annular portion 4a, and an outer annular portion 4c connected to the outer ends of the rib portions 4b. The number of flow channels 5 enclosed by the inner annular portion 4a, the rib portions 4b, and the outer annular portion 4c is the same as the number of rib portions 4b. In order to achieve both heat dissipation efficiency and mechanical strength, the number of rib portions 4b is set to 3 to 9. By setting the number of rib portions 4b to 3 or more, sufficient mechanical strength of the outer sheath 4 can be ensured. By setting the number of rib portions 4b to 9 or less, sufficient cross-sectional area of the flow channels 5 necessary for cooling by flowing a refrigerant can be ensured. More preferably, the number of rib portions 4b is set to 5 to 7. In other words, it is preferable that the number of flow channels 5 be set to 5 to 7.
[0016] In the example shown in Figure 1, the power cable 1 has six rib sections 4b extending radially from the inner annular section 4a, and six flow channels 5 are formed at these locations. As will be described later, the power cable 1 has a void section 6 consisting of a plurality of outer void sections 6a formed by the outer circumferential surface of the composite twisted structure in the stranded wire 2 and the inner circumferential surface of the inner annular section 4a, and a plurality of inner void sections 6b formed inside the stranded wire 2.
[0017] As shown in Fig. 2, the power cable 1 of the present embodiment is configured to suppress the temperature rise during energization by flowing the refrigerant 7 through the flow path 5 and the void portion 6. As an example, the refrigerant 7 is air or an inert gas. Thereby, an increase in the weight of the power cable 1 can be prevented. As an example, the outside air is used as the refrigerant 7. Then, the refrigerant 7 is taken in from one end side of the power cable 1 and made to flow, and is discharged outside the machine from the other end side of the power cable 1. Thereby, the power cable 1 can be easily cooled. The arrow in Fig. 2 indicates the traveling direction of the refrigerant 7. In addition, as a configuration other than the above, the refrigerant 7 may be an inert liquid or an antifreeze liquid.
[0018] The stranded wire 2 according to the present embodiment is formed by twisting copper or aluminum single wires. As an example, the stranded wire 2 is an aggregate of single wires in which an insulating film such as an oxide film is formed on the outer periphery of a metal wire made of copper or a copper alloy. As an example, the stranded wire 2 has a composite twist structure including a first stranded wire obtained by twisting single wires, a second stranded wire obtained by twisting the first stranded wire, and a third stranded wire obtained by twisting the second stranded wire. The insulating film in the stranded wire 2 is made of a material that does not interfere with soldering. As an example, the insulating film in the stranded wire 2 is made of polyurethane, polyester, or the like.
[0019] As an example, the porosity α of the void portion 6 is 27 to 35%. The porosity α is represented by the percentage of the cross-sectional area of the void portion 6 with respect to the inner cross-sectional area of the inner annular portion 4a. Since the outer periphery of the stranded wire 2 is inscribed in the inside of the inner annular portion 4a, the porosity α can be calculated from the relationship between the two.
[0020] Fig. 3A is a diagram schematically showing the arrangement of the void portion 6 when the final number of twists of the stranded wire 2 is three. The porosity α when the final number of twists of the stranded wire 2 is three is 35%. Fig. 3B is a diagram schematically showing the arrangement of the void portion 6 when the final number of twists of the stranded wire 2 is four. The porosity α when the final number of twists of the stranded wire 2 is four is 31%. Fig. 3C is a diagram schematically showing the arrangement of the void portion 6 when the final number of twists of the stranded wire 2 is five. The porosity α when the final number of twists of the stranded wire 2 is five is 31%. Fig. 3D is a diagram schematically showing the arrangement of the void portion 6 when the final number of twists of the stranded wire 2 is six. The porosity α when the final number of twists of the stranded wire 2 is six is 33%.
[0021] When the final of the twisted wire 2 is 7 - strand twisted, the porosity α is 33%. When the final of the twisted wire 2 is 8 - strand twisted, the porosity α is 27%. When the final of the twisted wire 2 is 9 - strand twisted, the porosity α is 31%. Also, when the final of the twisted wire 2 is 10 - strand twisted, the porosity α is 31%. And when the final of the twisted wire 2 is 11 - strand twisted, the porosity α is 29%.
[0022] In the example of FIG. 2, the twisted wire 2 is a rope twist. The rope twist is a twisting structure in the twisted wire 2 where the final (n + 1)-th twisting direction is opposite to the twisting direction from the first twisting direction to the n - th twisting direction. Here, n is a natural number of 2 or more. Preferably, n is 2 or 3.
[0023] As an example, a plurality of elementary wires are Z - twisted to form a first twisted wire, a plurality of the first twisted wires are Z - twisted to form a second twisted wire, and a plurality of the second twisted wires are S - twisted to form a third twisted wire. As another example, a plurality of elementary wires are Z - twisted to form a first twisted wire, a plurality of the first twisted wires are Z - twisted to form a second twisted wire, a plurality of the second twisted wires are Z - twisted to form a third twisted wire, and a plurality of the third twisted wires are S - twisted to form a fourth twisted wire. As another example, a plurality of elementary wires are S - twisted to form a first twisted wire, a plurality of the first twisted wires are S - twisted to form a second twisted wire, and a plurality of the second twisted wires are Z - twisted to form a third twisted wire. As another example, a plurality of elementary wires are S - twisted to form a first twisted wire, a plurality of the first twisted wires are S - twisted to form a second twisted wire, a plurality of the second twisted wires are S - twisted to form a third twisted wire, and a plurality of the third twisted wires are Z - twisted to form a fourth twisted wire. Here, Z - twist is synonymous with left - twist and S - twist is synonymous with right - twist.
[0024] As an example, the twisted wire 2 uses elementary wires composed of a metal wire made of copper or a copper alloy and an insulating film made of polyurethane. The total value of the cross - sectional area of the conductors is 20~120mm 2 . The insulating film has a radial thickness of 0.006~0.018mm.
[0025] As an example, 3 to 12 strands of wire are twisted together to create strand 2. As an example, 10 to 20 strands of wire are twisted together to create the first strand, and then 4 to 7 strands of the first strand are twisted together to create strand 2. As an example, 27 strands of wire are twisted together to create the first strand, and then 7 strands of the first strand are twisted together to create strand 2. As an example, 30 strands of wire are twisted together to create the first strand, and then 8 strands of the first strand are twisted together to create strand 2. As an example, 35 strands of wire are twisted together to create the first strand, and then 10 strands of the first strand are twisted together to create strand 2. As an example, 10 to 35 strands of wire are twisted together to create the first strand, and then 4 to 10 strands of the first strand are twisted together to create strand 2.
[0026] As an example, six strands of wire are twisted together in a Z-shape to form the first stranded wire, four strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, and four strands of the second stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, six strands of wire are twisted together in a Z-shape to form the first stranded wire, four strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, and five strands of the second stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, six strands of wire are twisted together in a Z-shape to form the first stranded wire, five strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, and seven strands of the second stranded wire are twisted together in an S-shape to form the second stranded wire. For example, 10 strands of wire are twisted together in a Z-shape to form the first stranded wire, 5 strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, and 7 strands of the second stranded wire are twisted together in an S-shape to form the second stranded wire. For example, 12 strands of wire are twisted together in a Z-shape to form the first stranded wire, 6 strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, and 10 strands of the second stranded wire are twisted together in an S-shape to form the second stranded wire. For example, 6 to 12 strands of wire are twisted together in a Z-shape to form the first stranded wire, 4 to 6 strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, and 4 to 10 strands of the second stranded wire are twisted together in an S-shape to form the second stranded wire.
[0027] As an example, six strands of wire are twisted together in a Z-shape to form the first stranded wire, four strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, four strands of the second stranded wire are twisted together in a Z-shape to form the third stranded wire, and four strands of the third stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, seven strands of wire are twisted together in a Z-shape to form the first stranded wire, six strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, five strands of the second stranded wire are twisted together in a Z-shape to form the third stranded wire, and five strands of the third stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, eight strands of wire are twisted together in a Z-shape to form the first stranded wire, six strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, five strands of the second stranded wire are twisted together in a Z-shape to form the third stranded wire, and seven strands of the third stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, 10 strands of wire are twisted together in a Z-shape to form the first stranded wire, 6 strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, 5 strands of the second stranded wire are twisted together in a Z-shape to form the third stranded wire, and 7 strands of the third stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, 12 strands of wire are twisted together in a Z-shape to form the first stranded wire, 6 strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, 6 strands of the second stranded wire are twisted together in a Z-shape to form the third stranded wire, and 7 strands of the third stranded wire are twisted together in an S-shape to form the second stranded wire. As an example, 12 strands of wire are twisted together in a Z-shape to form the first stranded wire, 7 strands of the first stranded wire are twisted together in a Z-shape to form the second stranded wire, 6 strands of the second stranded wire are twisted together in a Z-shape to form the third stranded wire, and 7 strands of the third stranded wire are twisted together in an S-shape to form the second stranded wire. For example, 6 to 12 strands of wire are twisted together in a Z-shape to create the first stranded wire, 4 to 10 strands of the first stranded wire are twisted together in a Z-shape to create the second stranded wire, 4 to 6 strands of the second stranded wire are twisted together in a Z-shape to create the third stranded wire, and 4 to 10 strands of the third stranded wire are twisted together in an S-shape to create stranded wire 2.
[0028] The outer covering 4 can be made of olefin resins such as polyethylene and polypropylene. Crosslinked polyethylene is particularly preferred because it has a heat resistance temperature of 120°C. The outer covering 4 can also be made of fluororesins such as PTFE, PFA, FEP, PCTFE, ETFE, and ECTFE. These fluororesins have better heat resistance than olefin resins.
[0029] As an example, the outer sheath portion 4 has a radial thickness of 0.6 to 2.4 mm for the inner annular portion 4a, a radial thickness of 0.6 to 2.4 mm for the outer annular portion 4c, and a circumferential thickness of 0.7 to 2.1 mm for the rib portion 4b. This configuration allows for a small diameter, robust, and highly flexible structure. However, the configuration is not limited to the above.
[0030] [Manufacturing method for the outer covering] The outer sheath portion 4 is manufactured using a die. The die has a central hole, an inner annular hole formed adjacent to its outer edge surrounding the central hole, six or more predetermined shaped holes extending radially from the outer circumference of the inner annular hole and wider than the inner annular hole, and an outer annular hole connecting the outer ends of the predetermined shaped holes and wider than the inner annular hole. Molten resin is extruded from the inner annular hole, predetermined shaped holes and outer annular hole using the die and slowly cooled and solidified. By forming the outer sheath portion 4 through this extrusion molding, an inner annular portion 4a, rib portions 4b extending radially from the inner annular portion 4a, and an outer annular portion 4c connecting the outer ends of the rib portions 4b are integrally formed around the stranded wire 2 using thermoplastic resin. Furthermore, a flow channel 5 is formed that is continuous in the longitudinal direction, surrounded by the inner annular portion 4a, the rib portions 4b, and the outer annular portion 4c. In addition, an outer void portion 6a is formed that is continuous in the longitudinal direction, surrounded by the outer circumferential surface of the stranded wire 2 and the inner circumferential surface of the inner annular portion 4a. According to the manufacturing method of this embodiment, a power cable 1 that is small in diameter, robust, and highly flexible can be produced.
[0031] [Air cooling test] Next, a sample was prepared and an air-cooling test was conducted to confirm the cooling capacity of the aforementioned power cable 1. The test standard was JIS C2805:2010.
[0032] (Examples) The stranded wire 2 in the example sample is a rope stranded wire made by twisting together 2520 strands of Type 2 polyurethane copper wire, each strand having an outer diameter of 0.12 mm. The stranded wire 2 is made by Z-twisting 12 strands together to form the first stranded wire, Z-twisting 6 strands of the first stranded wire to form the second stranded wire, Z-twisting 5 strands of the second stranded wire to form the third stranded wire, and S-twisting 7 strands of the third stranded wire. The stranded wire 2 has a void portion 6 consisting of a plurality of outer void portions 6a formed by the outer circumferential surface of the stranded wire 2 and the inner circumferential surface of the inner annular portion 4a, and an inner void portion 6b formed on the inside of the stranded wire 2, with a void ratio α of void portion 6 being 33%. The outer sheath portion 4 is made of cross-linked polyethylene resin. The outer sheath portion 4 has a radial thickness of 0.8 mm in the inner annular portion 4a, a circumferential thickness of 1.4 mm in the rib portion 4b, and a radial thickness of 1.2 mm in the outer annular portion 4c. The outer sheath portion 4 has six channels 5 formed in it. The power cable 1 of Example 1 has an outer diameter of 16.0 mm and a total length of 3.3 m.
[0033] In the first air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 50A was continuously applied to the stranded wire 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous energization, the surface temperature of the stranded wire 2 reached 154°C, and the surface temperature of the outer sheath 4 reached 121°C. Subsequently, room temperature air was introduced as the refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end of the sample. The temperature was measured using a non-contact thermometer after 10 minutes of continuous air cooling. As a result, the surface temperature of the stranded wire 2 reached 95°C, and the surface temperature of the outer sheath 4 reached 45°C. Therefore, the example confirmed that by flowing the refrigerant 7, the surface temperature of the stranded wire 2 was cooled by 59°C, and the surface temperature of the outer sheath 4 was cooled by 76°C.
[0034] In the second air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 70A was continuously applied to the stranded wire 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous energization, the surface temperature of the stranded wire 2 reached 164°C, and the surface temperature of the outer sheath 4 reached 131°C. Subsequently, room temperature air was introduced as the refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end of the sample. The temperature was measured using a non-contact thermometer after 10 minutes of continuous air cooling. As a result, the surface temperature of the stranded wire 2 reached 85°C, and the surface temperature of the outer sheath 4 reached 47°C. Therefore, the example confirmed that by flowing the refrigerant 7, the surface temperature of the stranded wire 2 was cooled by 79°C, and the surface temperature of the outer sheath 4 was cooled by 84°C.
[0035] (Reference example) The sample in the reference example is a bundle of 2520 strands of Type 2 polyurethane copper wire, each with an outer diameter of 0.12 mm, used as the conductor. The outer sheath of the reference example is the same as that of the embodiment. The outer diameter and total length of the cable in the reference example are the same as those of the embodiment.
[0036] In the first air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 50A was continuously applied to stranded wire 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous current application, the surface temperature of the conductor reached 154°C, and the surface temperature of the outer sheath reached 121°C. Subsequently, room temperature air was introduced as refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end. The temperature was measured using a non-contact thermometer after 10 minutes of continuous air cooling. As a result, the surface temperature of the conductor reached 105°C, and the surface temperature of the outer sheath reached 49°C. Therefore, it was confirmed that in the reference example, the surface temperature of the conductor was cooled by 49°C and the surface temperature of the outer sheath was cooled by 72°C by flowing refrigerant 7.
[0037] In the second air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 70A was continuously applied to stranded wire 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous current application, the surface temperature of the conductor reached 164°C, and the surface temperature of the outer sheath reached 131°C. Subsequently, room temperature air was introduced as refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end of the sample. The temperature was measured using a non-contact thermometer after 10 minutes of continuous air cooling. As a result, the surface temperature of the conductor reached 94°C, and the surface temperature of the outer sheath reached 52°C. Therefore, it was confirmed that in the reference example, the surface temperature of the conductor was cooled by 70°C and the surface temperature of the outer sheath 4 was cooled by 79°C by flowing refrigerant 7.
[0038] The results of the above-mentioned air cooling tests confirmed that in both the example and the reference example, the temperature rise could be suppressed by flowing the refrigerant 7 through the flow path 5. Furthermore, it was confirmed that the example could suppress the temperature rise during energization even more effectively than the reference example which does not have the air gap 6. [Explanation of Symbols]
[0039] 1 Power cable 2 strands 4 outer cover portion, 4a inner annular portion, 4b rib portion, 4c outer annular portion 5 channels 6 Cavity, 6a Outer cavity, 6b Inner cavity 6b 7 Refrigerant 51 Electric vehicle, 51a Power supply unit, 51b Battery α porosity
Claims
1. The device comprises a stranded wire and an outer sheath that insulates the stranded wire, the outer sheath comprising an inner annular portion, three or more rib portions extending radially from the inner annular portion, and an outer annular portion connected to the outer end of the rib portions, and the number of flow channels enclosed by the inner annular portion, the rib portions, and the outer annular portion is the same as the number of rib portions. The aforementioned stranded wire is an assembly of individual wires, each having an insulating layer formed on its outer circumference, and has a void portion, which consists of an outer void portion formed on the outside of the stranded wire and an inner void portion formed on the inside of the stranded wire. The configuration suppresses the temperature rise when power is applied by flowing a refrigerant through the aforementioned flow path and the aforementioned gap. A power cable characterized by the following features.
2. The porosity of the aforementioned void is 27-35%. The power cable according to claim 1, characterized by the following:
3. The aforementioned stranded wire is twisted into a rope. The power cable according to claim 2, characterized by the following:
4. To configure a power supply line from the power supply unit to the battery in an electric vehicle. A power cable according to any one of claims 1 to 3, characterized by the following: