A large-current square flexible cable and a preparation method thereof

Abstract

The application belongs to the field of cables, and discloses a large-current square flexible cable and a preparation method thereof.The large-current square flexible cable comprises, from inside to outside, a conductor, an inner shielding layer, an inner semiconductive layer, a modified cross-linked polyolefin insulation layer, an outer semiconductive layer, an outer shielding layer and a sheath layer; the conductor comprises multiple layers of copper sheets and interlayer insulation films between the copper sheets.The cable has high current carrying density, low partial discharge, high voltage strength, high shielding effectiveness, low transfer impedance and good mechanical properties and environmental properties.

Description

Technical Field

[0001] This invention belongs to the field of cables, and specifically relates to a high-current square flexible cable and its preparation method. Background Technology

[0002] With the rapid development of new energy power generation and industrial automation, the demand for flexible cables with high current density and high reliability in power transmission systems is becoming increasingly urgent. Traditional round cables have the following technical bottlenecks: low current carrying capacity, with a circular cross-section space utilization rate of less than 70%; poor heat dissipation performance, with the skin effect leading to excessive temperature rise; and low temperature resistance, with ordinary PVC insulation only able to withstand temperatures up to 105℃.

[0003] To address the aforementioned issues, using square-section conductors has become a viable technological approach. Square conductors offer higher space utilization and a larger heat dissipation surface area for the same cross-sectional area, enabling them to carry higher current densities while also reducing the impact of the skin effect.

[0004] However, the application of square conductors also brings new technical challenges. First, the square cross-section exhibits electric field concentration at its corners, which, if not properly addressed, can lead to partial discharge or even insulation breakdown, severely impacting the cable's reliability and lifespan. Second, square conductors employing multi-layer copper sheet stacking structures have stepped edges on their surface, placing higher demands on the adhesion of the cladding layer. Furthermore, achieving good mid-to-high frequency electromagnetic shielding performance while ensuring high current carrying capacity is also a pressing technical challenge that needs to be addressed in this field. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the purpose of this invention is to provide a high-current square flexible cable.

[0006] Another objective of this invention is to provide a method for preparing the above-mentioned high-current square flexible cable.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A high-current square flexible cable comprises, from the inside out, a conductor, an inner shielding layer, an inner semiconductive layer, a modified cross-linked polyolefin insulation layer, an outer semiconductive layer, an outer shielding layer, and a sheath layer; the conductor comprises multiple layers of copper sheets and interlayer insulating films between the copper sheets.

[0008] Furthermore, the copper sheet includes a copper sheet body and a plating layer covering the outer surface of the copper sheet body.

[0009] Furthermore, the plating layer is at least one of a tin layer and a silver layer.

[0010] Furthermore, the thickness of the copper sheet body is 0.95-3.05 mm; the thickness of the plating layer is 3-5 μm.

[0011] Furthermore, the copper sheet has 1-5 layers.

[0012] Furthermore, the interlayer insulating film includes an aluminum oxide film.

[0013] Furthermore, the thickness of the interlayer insulating film is 40-60 μm, preferably 45-55 μm.

[0014] Furthermore, both the inner and outer semiconductive layers are composite layers of carbon nanotubes and insulating materials.

[0015] Furthermore, the insulating material includes at least one of silicone rubber and cross-linked polyolefin (XLPO).

[0016] Furthermore, the thickness of the inner semiconductive layer and the outer semiconductive layer are independently 0.18-0.22 mm.

[0017] Furthermore, both the inner and outer shielding layers are tin-plated copper wire braided layers; the coverage of the inner shielding layer is ≥85%; the diameter of the tin-plated copper wire is 0.14-0.17mm; preferably 0.14-0.16mm; and / or, the coverage of the outer shielding layer is ≥90%; the diameter of the tin-plated copper wire is 0.11-0.13mm.

[0018] Furthermore, the modified cross-linked polyolefin insulating layer is a composite layer of cross-linked polyolefin with an aromatic ring structure introduced into the main chain and hindered phenolic antioxidant.

[0019] Furthermore, the amount of the hindered phenolic antioxidant added is 0.8% of the mass of the cross-linked polyolefin.

[0020] Furthermore, the sheath layer is a composite layer of low-smoke halogen-free polypropylene (LSZH-PP) and flame retardant.

[0021] Furthermore, the flame retardant includes at least one of magnesium hydroxide, aluminum hydroxide, and ammonium polyphosphate.

[0022] Further, the flame retardant is magnesium hydroxide and ammonium polyphosphate; the magnesium hydroxide is 63-67% of the mass of the low-smoke halogen-free polypropylene; preferably 64.5-65.5%, and the ammonium polyphosphate is 13-17% of the mass of the low-smoke halogen-free polypropylene; preferably 14.5-15.5%.

[0023] A method for manufacturing the above-mentioned high-current square flexible cable includes the following steps: S1. In a vacuum environment, copper sheets and interlayer insulating films are stacked sequentially, and the stacked conductor is hot-pressed; a pulsed laser is used to perform micro-spot welding on the hot-pressed conductor; S2. Weave an inner shielding layer on the outer surface of the conductor obtained in step S1; S3. The outer surface of the product obtained in step S2 is extruded simultaneously using an extruder and a composite die head to form an inner semiconductive layer, a modified cross-linked polyolefin insulating layer, and an outer semiconductive layer. S4. Weave an outer shielding layer on the outer surface of the product obtained in step S3; S5. A sheath layer is formed on the outer surface of the product obtained in step S4 by an extrusion process.

[0024] Furthermore, the coating in the copper sheet described in step S1 is obtained by electroplating methyl sulfonate on the surface of the copper sheet body.

[0025] Further, the hot pressing temperature in step S1 is 155°C; the pressure is 18 MPa; and the time is 8-12 min, preferably 9-11 min.

[0026] Furthermore, the spacing of the micro-spot welding in step S1 is 4.8-5.2 mm.

[0027] Furthermore, the weaving described in steps S2 and S4 is independently performed using a 72-spindle high-speed weaving machine; the weaving speed is independently 24-26 rpm; and the weaving angle is independently 43-47°.

[0028] Furthermore, in step S3, the temperature of the feeding section of the extruder is 155-165℃; the temperature of the die head is 195-205℃.

[0029] The implementation of this invention has the following beneficial effects: The cable of this invention features high current carrying capacity, low partial discharge, high withstand voltage, high shielding effectiveness, low transfer impedance, and excellent mechanical and environmental properties. Specifically: The conductor of this invention adopts a design of multi-layer copper sheet stacking and interlayer insulation, which not only improves the current carrying density, but also effectively suppresses high-frequency eddy current loss and reduces the skin effect through interlayer insulation; the semiconducting layer and the shielding layer form a gradient electromagnetic shielding structure, which significantly improves the shielding performance in the mid-to-high frequency range; the modified cross-linked polyolefin insulation layer maintains high electrical strength and mechanical properties after long-term aging at 125°C through aromatic ring structure modification and antioxidant synergy.

[0030] This invention avoids dielectric loss and improves the insulation strength and thermal stability between conductor layers through vacuum hot pressing; it achieves reliable electrical connection between conductor layers through laser micro-welding while maximizing the overall flexibility of the conductor; and it ensures a seamless interface between the three functional layers through a three-layer co-extrusion process, eliminating interlayer gaps, significantly improving the electric field distribution, and reducing partial discharge to an extremely low level. Attached Figure Description

[0031] Figure 1This is a schematic diagram of the high-current square flexible cable of the present invention.

[0032] Wherein, 1-conductor; 101-copper sheet; 102-interlayer insulating film; 2-inner shielding layer; 3-inner semiconducting layer; 4-modified cross-linked polyolefin insulating layer; 5-outer semiconducting layer; 6-outer shielding layer; 7-sheathing layer. Detailed Implementation

[0033] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the invention will now be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing the present invention and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on the present invention.

[0034] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are used only for the convenience of describing the present invention and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood according to the specific circumstances.

[0035] Unless otherwise specified, all reagents used in the examples are commercially available.

[0036] like Figure 1 As shown, a high-current square flexible cable includes, from the inside out, a conductor 1, an inner shielding layer 2, an inner semiconductive layer 3, a modified cross-linked polyolefin insulation layer 4, an outer semiconductive layer 5, an outer shielding layer 6, and a sheath layer 7; the conductor 1 includes multiple copper sheets 101 and interlayer insulating films 102 between the copper sheets 101.

[0037] Specifically, in this embodiment, the conductor 1 adopts a design of multilayer copper sheet 101 stacking and interlayer insulation, which not only increases the current carrying density, but also effectively suppresses high-frequency eddy current loss and reduces the skin effect through interlayer insulation; the semiconducting layer and the shielding layer form a gradient electromagnetic shielding structure, which significantly improves the shielding performance in the mid-to-high frequency range; the modified cross-linked polyolefin insulation layer 4 maintains high electrical strength and mechanical properties after long-term aging at 125°C through aromatic ring structure modification and antioxidant synergy.

[0038] In some embodiments, the copper sheet 101 includes a copper sheet body and a plating layer covering the outer surface of the copper sheet body. The plating layer is at least one of tin and silver. The thickness of the copper sheet body is 0.95-3.05 mm, and the thickness can be any value within this range, including 0.95 mm, 1 mm, or 3.05 mm, etc.; the thickness of the plating layer is 3-5 μm, such as 3 μm, 4 μm, or 5 μm, etc. The number of layers of the copper sheet 101 is 1-5, and can be 1, 3, or 5, etc.

[0039] In some embodiments, the interlayer insulating film 102 comprises an aluminum oxide film. Preferably, it is an anodic aluminum oxide film. The thickness of the interlayer insulating film 102 is 40-60 μm, preferably 45-55 μm, and can be selected as 40 μm, 45 μm, 50 μm, 55 μm or 60 μm, etc.

[0040] In some embodiments, both the inner semiconductive layer 3 and the outer semiconductive layer 5 are composite layers of carbon nanotubes and insulating materials. The insulating material includes at least one of silicone rubber and cross-linked polyolefin (XLPO). The cross-linked polyolefin includes cross-linked polyethylene or cross-linked polypropylene, etc. Specifically, the semiconductive layer not only provides electric field homogenization but also enhances the adhesion between the insulating layer and the shielding layer (≥50 N / cm), preventing interlayer delamination. Further, the resistance gradient between the inner semiconductive layer 3 and the outer semiconductive layer 5 is 10. 2 -10 4 Ω·cm.

[0041] In some embodiments, the thickness of the inner semiconductive layer 3 and the outer semiconductive layer 5 is independently 0.18-0.22 mm, and the thickness can be selected from any value within this range, including 0.18 mm, 0.2 mm or 0.22 mm, etc.

[0042] In some embodiments, both the inner shielding layer 2 and the outer shielding layer 6 are tin-plated copper wire braided layers; the coverage of the inner shielding layer 2 is ≥85%, optionally 85%, 90%, or 95%; the diameter of the tin-plated copper wire is 0.14-0.17 mm, preferably 0.14-0.16 mm, such as 0.14 mm, 0.15 mm, 0.16 mm, or 0.17 mm; the coverage of the outer shielding layer 6 is ≥90%, optionally 90%, 92%, or 95%; the diameter of the tin-plated copper wire is 0.11-0.13 mm, such as 0.11 mm, 0.12 mm, or 0.13 mm. Understandably, through the synergy of the high-density tin-plated copper wire braided inner shielding layer 2, the precision tin-plated copper wire braided outer shielding layer 6, and the inner and outer semiconductive layers 3 and 5, a shielding effectiveness of ≥70 dB (1 MHz-1 GHz) is achieved.

[0043] In some embodiments, the modified crosslinked polyolefin insulating layer 4 is a composite layer of crosslinked polyolefin with an aromatic ring structure introduced into the main chain and a hindered phenolic antioxidant. Specifically, the crosslinked polyolefin with an aromatic ring structure introduced into the main chain includes an ethylene-styrene copolymer crosslinked by peroxide or silane; the hindered phenolic antioxidant includes one of antioxidant 1076 (octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and antioxidant 1010 (pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]). Further, the amount of hindered phenolic antioxidant added is 0.8% of the mass of the crosslinked polyolefin. The modified crosslinked polyolefin insulating layer 4 has a dielectric strength ≥25kV / mm and a volume resistivity ≥10. 15 Ω·cm.

[0044] In some embodiments, the sheath layer 7 comprises low-smoke halogen-free polypropylene (LSZH-PP) and a flame retardant. The flame retardant comprises at least one of magnesium hydroxide, aluminum hydroxide, and ammonium polyphosphate, with combinations including aluminum hydroxide and ammonium polyphosphate, magnesium hydroxide and ammonium polyphosphate, or magnesium hydroxide + aluminum hydroxide + ammonium polyphosphate, etc. Further, the flame retardant is magnesium hydroxide and ammonium polyphosphate; the magnesium hydroxide constitutes 63-67% of the mass of the low-smoke halogen-free polypropylene, preferably 64.5-65.5%, optionally 63%, 64.5%, 65%, 65.5%, or 67%, etc., and the ammonium polyphosphate constitutes 13-17% of the mass of the low-smoke halogen-free polypropylene, preferably 14.5-15.5%, such as 13%, 14.5%, 15%, 15.5%, or 17%, etc. By adjusting the ratio of low-smoke halogen-free polypropylene (LSZH-PP) to the flame retardant, an oxygen index ≥32% and a smoke density transmittance ≥80% are achieved, which is superior to conventional halogen-free materials (typically ≤60%). The magnesium hydroxide flame retardant contained in the sheath material decomposes and absorbs heat at high temperatures, forming a protective layer that delays the oxidation of the shielding layer and improves the electrical resistance stability after salt spray testing (change ≤5%). The thickness of sheath layer 7 is 1.4-1.6mm, with options including 1.4mm, 1.5mm, or 1.6mm.

[0045] Some embodiments provide a method for preparing the above-mentioned high-current square flexible cable, including the following steps: S1. In a vacuum environment, copper sheets and interlayer insulating films are stacked sequentially, and the stacked conductor is hot-pressed; a pulsed laser is used to perform micro-spot welding on the hot-pressed conductor.

[0046] Specifically, the plating on the copper sheet is obtained by electroplating methanesulfonate on the surface of the copper sheet body. The hot pressing temperature is 155℃; the pressure is 18MPa; and the time is 8-12 min, preferably 9-11 min, such as 8 min, 9 min, 10 min, 11 min, or 12 min. The spacing of the micro-spot welding is 4.8-5.2 mm, such as 4.8 mm, 5 mm, or 5.2 mm.

[0047] Furthermore, real-time X-ray imaging (10μm resolution) is introduced after hot pressing to enable online detection and control throughout the process, ensuring that there is no misalignment between layers and that the welding points are of good quality.

[0048] Specifically, during the vacuum hot pressing process, the vacuum environment completely eliminates air bubbles between the copper sheet layers. The precisely controlled temperature and pressure ensure that the insulating film deforms uniformly and achieves a physical-chemical bond with the copper sheet. No adhesive is needed, thus avoiding dielectric loss and improving the interlayer insulation strength and thermal stability.

[0049] Specifically, in the process of micro-spot welding using pulsed lasers, the laser energy is concentrated and the heat-affected zone is extremely small, which achieves reliable electrical connection between conductor layers while maintaining the overall flexibility of the conductor to the maximum extent.

[0050] The DC resistivity of the conductor obtained in step S1 is ≤0.0175Ω·mm. 2 / m, superior to conventional soft busbars (typically ≥0.018Ω·mm). 2 / m).

[0051] S2. Weave an inner shielding layer on the outer surface of the conductor obtained in step S1.

[0052] S3. The outer surface of the product obtained in step S2 is extruded simultaneously using an extruder and a composite die head to form an inner semiconductive layer, a modified cross-linked polyolefin insulating layer, and an outer semiconductive layer.

[0053] Specifically, in step S3, the temperature of the feeding section of the extruder is 155-165℃, and can be selected from 155℃, 160℃, or 165℃, etc.; the temperature of the die head is 195-205℃, and any value can be selected within this range, including 195℃, 200℃, or 205℃, etc.

[0054] Understandably, a single extruder combined with a composite die head is used to achieve simultaneous extrusion molding of the inner semiconductive layer, the modified cross-linked polyolefin insulating layer, and the outer semiconductive layer in one step. This process ensures a seamless interface between the three functional layers, eliminates interlayer gaps, significantly improves the electric field distribution, and reduces partial discharge to an extremely low level (<3pC).

[0055] S4. Weave an outer shielding layer on the outer surface of the product obtained in step S3.

[0056] Specifically, steps S2 and S4 are independently woven using a 72-spindle high-speed braiding machine; the braiding speed is independently 24-26 rpm, and the braiding speed of steps S2 and S4 can be selected independently within this range, such as 24 rpm, 25 rpm or 26 rpm; the braiding angle is independently 43-47°, and 43°, 45° or 47° can be selected.

[0057] Furthermore, the weaving process employs a 72-spindle high-speed weaving machine, achieving a tension control accuracy of ±0.1N, ensuring stable shielding layer coverage and uniform structure.

[0058] S5. A sheath layer is formed on the outer surface of the product obtained in step S4 by an extrusion process. Specifically, the extrusion process in this step is a conventional process.

[0059] Example 1 The structural parameters of the high-current square flexible cable in this embodiment are as follows: The conductor consists of 5 layers of 1.0 mm thick copper sheets (the copper sheet body is 0.994 mm thick, the plating is tin, and the plating thickness is 3 μm), and the interlayer insulating film is a 50 μm anodic aluminum oxide film; The diameter of the tin-plated copper wire in the inner shielding layer is 0.15mm, with a coverage rate of 85%. The inner semiconductive layer is a composite layer of carbon nanotubes and silicone rubber with a thickness of 0.20 mm. The amount of carbon nanotubes added is 3.0% of the mass of silicone rubber. The modified cross-linked polyolefin insulation layer is a 1.2 mm thick composite layer of ethylene-styrene copolymer and antioxidant 1010 (the amount of antioxidant 1010 added is 0.8% of the mass of ethylene-styrene copolymer); The outer semiconductive layer is a 0.20 mm thick composite layer of carbon nanotubes and silicone rubber, with the amount of carbon nanotubes added being 3.0% of the mass of the silicone rubber. The diameter of the tin-plated copper wire in the outer shielding layer is 0.12 mm, with a coverage rate of 90%. The sheath layer is a 1.5mm thick composite layer of LSZH-PP and flame retardant. The flame retardant is magnesium hydroxide (65% of the mass of LSZH-PP) and ammonium polyphosphate (15% of the mass of LSZH-PP).

[0060] The method for preparing a high-current square flexible cable in this embodiment includes the following steps: S1. Under vacuum, copper sheets and interlayer insulating films are stacked sequentially, and the stacked conductor is hot-pressed at 155℃ and 18MPa for 10 minutes; the hot-pressed conductor is then micro-spot welded with a spacing of 5mm using a pulsed laser, and the welding power is 200W. S2. The outer surface of the conductor obtained in step S1 is braided with an inner shielding layer using a 72-spindle high-speed braiding machine at a braiding speed of 25 rpm and a braiding angle of 45°. S3. The outer surface of the product obtained in step S2 is extruded simultaneously using an extruder and a composite die head to form an inner semiconductive layer, a modified cross-linked polyolefin insulating layer, and an outer semiconductive layer. The temperature of the feeding section of the extruder is 160°C; the temperature of the die head is 200°C. S4. The outer surface of the product obtained in step S3 is braided with a 72-spindle high-speed braiding machine to form an outer shielding layer. The braiding speed is 25 rpm and the braiding angle is 45°. S5. A sheath layer is formed on the outer surface of the product obtained in step S4 by an extrusion process.

[0061] The cable obtained in this embodiment was subjected to relevant tests, and the results are as follows: Electrical performance: DC resistance: 0.0173 Ω·mm 2 / m; Power frequency withstand voltage: 12kV / 5min without breakdown; Partial discharge: 1.8 pC (1.5 U0); Shielding effectiveness: 72dB (100MHz); Transfer impedance: 9mΩ / m (100MHz).

[0062] Mechanical properties: Tensile strength: 15 MPa; Bending life: 120,000 cycles (R=8D); Compressive strength: 2000 N / 10 cm; Adhesion of the braided layer: 53 N / cm.

[0063] Environmental performance: Temperature resistance test: After aging at 125℃ for 3000 hours, the tensile strength retention rate was 92%, and the volume resistivity was 10. 14 Ω·cm; Salt spray test: After 96 hours, the resistance change of the inner and outer shielding layers is ≤5%; Flame retardant test: self-extinguishing time for vertical combustion is 14s; light transmittance in smoke density is 80%.

[0064] Example 2 The difference from Example 1 is that the thickness of both the inner and outer semiconductive layers is 0.18 mm.

[0065] The cable obtained in this embodiment was subjected to relevant tests, and the results are as follows: Electrical performance: DC resistivity: 0.0173 Ω·mm 2 / m; Power frequency withstand voltage: 12kV / 5min without breakdown; Partial discharge: 2.5pC (1.5U0); Shielding effectiveness: 71dB (100MHz); Transfer impedance: 9mΩ / m (100MHz).

[0066] Mechanical properties: Tensile strength: 15 MPa; Bending life: 120,000 cycles (R=8D); Compressive strength: 2000 N / 10 cm; Adhesion of the braided layer: 52 N / cm.

[0067] Environmental performance: Temperature resistance test: After aging at 125℃ for 3000 hours, the tensile strength retention rate was 92%, and the volume resistivity was 10. 14 Ω·cm; Salt spray test: After 96 hours, the resistance change of the inner and outer shielding layers is ≤5%; Flame retardant test: self-extinguishing time for vertical combustion is 14s; light transmittance in smoke density is 80%.

[0068] Example 3 The difference from Example 1 is that the inner and outer semiconductive layers are composite layers of carbon nanotubes and cross-linked polyethylene.

[0069] The cable obtained in this embodiment was subjected to relevant tests, and the results are as follows: Electrical performance: DC resistivity: 0.0170 Ω·mm 2 / m; Power frequency withstand voltage: 12kV / 5min without breakdown; Partial discharge: 2.0 pC (1.5 U0); Shielding effectiveness: 72dB (500MHz); Transfer impedance: 9mΩ / m (100MHz).

[0070] Mechanical properties: Tensile strength: 15 MPa; Bending life: 110,000 cycles (R=8D); Compressive strength: 2100 N / 10 cm; Adhesion of the braided layer: 55 N / cm.

[0071] Environmental performance: Temperature resistance test: After aging at 125℃ for 3000 hours, the tensile strength retention rate was 92%, and the volume resistivity was 2×10⁻⁶. 14 Ω·cm; Salt spray test: After 96 hours, the resistance change of the inner and outer shielding layers is ≤5%; Flame retardant test: self-extinguishing time for vertical combustion is 15s; light transmittance in smoke density is 80%.

[0072] Comparative Example 1 The difference from Example 1 is as follows: The conductor has three layers of copper sheets, and the interlayer insulating film is replaced with interlayer coated epoxy conductive adhesive.

[0073] Step S1 involves pressing the conductor layers together at 120°C and 10MPa in a non-vacuum environment; resistance spot welding is used between the conductor layers.

[0074] Step S3 involves three extrusion steps: first, the inner semiconductive layer is extruded; after cooling, the modified cross-linked polyolefin insulating layer is extruded; and after cooling, the outer semiconductive layer is extruded.

[0075] Comparative Example 2 The difference from Comparative Example 1 is that it has no inner semiconductive layer and no outer semiconductive layer.

[0076] Table 1 Performance comparison of Example 1 and Comparative Examples 1-2 In summary, the cable having the structure described in the above embodiments and obtained using the corresponding manufacturing method possesses the following properties: Electrical performance: DC resistivity: ≤0.0175Ω·mm 2 / m. The DC resistivity is comparable to that of pure copper, indicating that the multilayer copper sheet stacked structure does not sacrifice conductivity. At the same time, the square cross-section has a higher space utilization rate than the circular one, effectively improving the current carrying capacity.

[0077] Power frequency withstand voltage: 12kV / 5min without breakdown; Partial discharge: <3pC (1.5U0). In the power frequency withstand voltage test, the cable can withstand 12kV / 5min without breakdown; at the 1.5U0 test voltage, the partial discharge of the cable is less than 3pC. This indicates that the electric field concentration problem at the corners of the square conductor has been effectively suppressed, and the overall electrical strength of the insulation system is good.

[0078] Shielding effectiveness: ≥70dB (1MHz-1GHz); Transfer impedance: ≤10mΩ / m (100MHz). This indicates that the gradient shielding structure formed by the semiconductive layer and the shielding layer effectively improves the shielding performance at mid-to-high frequencies.

[0079] Mechanical properties: Tensile strength: ≥15MPa; Bending life: >100,000 cycles (R=8D); Compressive strength: ≥2000N / 10cm; Adhesion of the braided layer: ≥50N / cm.

[0080] Environmental performance: Temperature resistance test: After aging at 125℃ for 3000 hours, the tensile strength retention rate is ≥90%, and the volume resistivity is ≥10. 14 Ω·cm; Salt spray test: After 96 hours, the resistance change of the inner and outer shielding layers is ≤5%; Flame retardant test: self-extinguishing time of vertical combustion ≤15s; light transmittance in smoke density ≥80%.

[0081] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A high-current square flexible cable, characterized in that: From the inside out, it comprises a conductor, an inner shielding layer, an inner semiconductive layer, a modified cross-linked polyolefin insulating layer, an outer semiconductive layer, an outer shielding layer, and a sheath layer; the conductor comprises multiple copper sheets and an interlayer insulating film between the copper sheets; Both the inner and outer semiconductive layers are composite layers of carbon nanotubes and insulating materials. The thickness of the inner and outer semiconductive layers is independently 0.18-0.22 mm; Both the inner and outer shielding layers are tin-plated copper wire braided layers. The coverage of the inner shielding layer is ≥85%; The coverage of the outer shielding layer is ≥90%.

2. The high-current square flexible cable according to claim 1, characterized in that: The copper sheet includes a copper sheet body and a plating layer covering the outer surface of the copper sheet body.

3. The high-current square flexible cable according to claim 1, characterized in that: The interlayer insulating film includes an aluminum oxide film.

4. The high-current square flexible cable according to claim 1, characterized in that: The modified cross-linked polyolefin insulating layer is a composite layer of cross-linked polyolefin with an aromatic ring structure introduced into the main chain and hindered phenolic antioxidant.

5. The high-current square flexible cable according to claim 1, characterized in that: The sheath layer is a composite layer of low-smoke halogen-free polypropylene and flame retardant.

6. A method for preparing a high-current square flexible cable according to any one of claims 1-5, characterized in that, Includes the following steps: S1. In a vacuum environment, copper sheets and interlayer insulating films are stacked sequentially, and the stacked conductor is hot-pressed; a pulsed laser is used to perform micro-spot welding on the hot-pressed conductor; S2. Weave an inner shielding layer on the outer surface of the conductor obtained in step S1; S3. The outer surface of the product obtained in step S2 is extruded simultaneously using an extruder and a composite die head to form an inner semiconductive layer, a modified cross-linked polyolefin insulating layer, and an outer semiconductive layer. S4. Weave an outer shielding layer on the outer surface of the product obtained in step S3; S5. A sheath layer is formed on the outer surface of the product obtained in step S4 by an extrusion process.

7. The method for preparing a high-current square flexible cable according to claim 6, characterized in that: The hot pressing temperature in step S1 is 155℃; the pressure is 18MPa; and the time is 8-12min. And / or, the spacing of the micro-spot welding in step S1 is 4.8-5.2 mm.

Images