A high temperature superconducting current lead

Abstract

The application provides a high-temperature superconducting current lead, and belongs to the technical field of superconducting material preparation, and comprises: an HTS composite strip, which is prepared by parallel welding a plurality of HTS strips in the length direction of a flexible metal plate; and a stabilizer material, which is impregnated into the HTS composite strip, and has a critical temperature higher than that of the HTS strip and lower than the smaller value between the thermal degradation temperature of the HTS strip and the melting point of the welding material. By parallel welding a plurality of HTS strips in the length direction of a flexible metal strip and externally arranging the stabilizer material for protection, the pre-prepared high-temperature superconducting current lead can meet the minimum critical bending radius of 5 mm, and the prepared high-temperature superconducting current lead can be deformed to a large extent during use, and when Δ(I c / I c0 ) is greater than 1% and the final bending radius is not less than 5 mm, the critical strain is not greater than 0.4%.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting material preparation, and in particular relates to a high-temperature superconducting current lead. Background Art

[0002] High-temperature superconducting materials offer numerous advantages, including low loss and high current carrying capacity. High-temperature superconducting current leads are key electrical connection components, widely used in superconducting magnets, magnetic resonance imaging, and superconducting power equipment. Compared to traditional metal wires, high-temperature superconducting materials offer the advantages of zero resistance and high current carrying capacity, improving energy efficiency and reducing production costs across a wide range of industries.

[0003] Traditional current leads use metal conductors such as copper, which can cause heat generation and energy dissipation when carrying high currents. With technological advancements and increasing demands for energy efficiency, high-temperature superconducting current leads are becoming an ideal alternative to traditional wires. They can withstand high current densities and excel in high-power applications. Yttrium barium copper oxide (YBCO), a typical second-generation high-temperature superconductor material, is often used in conjunction with copper to create high-temperature superconducting current leads.

[0004] During use, high-temperature superconducting tape is often subjected to tensile or compressive strain. Without a mechanically stable structure, the tape is easily damaged by mechanical stress and other factors, resulting in a decrease in the current-carrying performance of the current leads. Providing stable support for the high-temperature superconducting tape improves its mechanical stability and increases its plasticity, allowing it to maintain good current-carrying performance in a variety of application environments. Rigid current leads may encounter mechanical issues such as thermal contraction during cooling, and flexible current leads may break if bent into a tape with an excessively small diameter. Therefore, it is necessary to add a protective structure to the conductive structure of the lead.

[0005] The invention patent with announcement number CN112997260B discloses a high-temperature superconducting current lead with a braided sleeve and a junction box and a preparation method thereof. The invention patent prepares multiple HTS tapes into an HTS cable, which is then wrapped in a braided sleeve made of copper, and a sealing sheath is added to the outermost layer. The first and second junction boxes are connected at the ends of the current lead. However, during the bending process of the high-temperature superconducting current prepared by this technical solution, the HTS strips rub against each other, making the current lead unable to be reused multiple times. In addition, the current lead of this technical solution is pre-bent before preparation. After preparation, it cannot be adjusted to a large range, which greatly reduces its applicability.

[0006] The invention patent with publication number JP2016009721A discloses a superconducting current lead, which includes a superconducting tape, a metal electrode for joining the two ends of the superconducting tape, and a reinforcing component. However, the superconducting tape segment has no mechanically stable protective structure, and the superconducting tape is easily bent and broken, resulting in damage to the current lead. Summary of the Invention

[0007] To solve the above problems, the present invention provides a high-temperature superconducting current lead. By welding multiple HTS tapes in parallel along the length of a flexible metal strip and providing a stabilizer material on the outside for protection, the pre-prepared high-temperature superconducting current lead can meet the minimum critical bending radius of 5mm, and the prepared high-temperature superconducting current lead can be deformed to a large extent during use. c / I c0 )>1% and the final bending radius is not less than 5mm, the critical strain is not greater than 0.4%.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a high-temperature superconducting current lead, comprising: an HTS composite tape, wherein the HTS composite tape is prepared by parallel welding a plurality of HTS tapes in the length direction of a flexible metal plate; and a stabilizer material, wherein the HTS composite tape is impregnated with the stabilizer material, and the stabilizer material has a temperature higher than the critical temperature of the HTS tape and lower than the thermal degradation temperature of the HTS tape or the melting point of the solder, whichever is smaller.

[0010] Furthermore, it also includes: a sheath, which wraps the stabilizer material.

[0011] Furthermore, the cross-section of the sheath is elliptical, and the major axis of the ellipse coincides with the width direction of the metal plate.

[0012] Furthermore, the stabilizer material is wax; the flexible metal strip is a copper strip; the Hastelloy alloy side of the HTS strip is welded to the flexible metal strip via a PbSn tin material; and the thickness of the welding layer is 0.05-0.1 mm.

[0013] Furthermore, the relationship between the major axis a and minor axis b of the ellipse and the width w of the metal plate satisfies:

[0014]

[0015] b=λ2a

[0016] Where λ1 is the first correction coefficient, λ2 is the second correction coefficient, and w0 is the standard width.

[0017] Furthermore, the welding area between the HTS tape and the flexible metal strip is divided into a plurality of independent partitions, and the distance between two adjacent independent partitions does not exceed 2 mm.

[0018] Furthermore, the thickness t of the welding layer and the distance L between the independent partitions satisfy:

[0019] s=tL

[0020] L=λ3t 2 / 3

[0021] Where s is the preset area value, and λ3 is the third correction coefficient.

[0022] Furthermore, the system further comprises: a junction box, located at each end of the HTS composite strip, each junction box being electrically connected to the HTS composite strip and configured to be electrically connected to an external component.

[0023] Furthermore, it includes a sheath, and both ends of the sheath have a portion to be clamped; the junction box includes an electrical connection portion, and a clamping portion rotatably connected to the electrical connection portion, and when the clamping portion is rotated and tightened, the electrical connection portion and the clamping portion clamp the portion to be clamped.

[0024] Furthermore, the electrical connection portion of the junction box consists of two parts, and a slot is provided at the junction of the two parts, and the slot is used to accommodate the HTS composite strip; a protrusion is provided on the side for contacting the flexible metal strip of the HTS composite strip, the height of the protrusion is not greater than 3 / 4 of the thickness of the flexible metal strip, and the pressing surface of the protrusion is planar, and the total area of ​​the pressing surface is 1 / 10-3 / 10 of the contact area between the slot and the HTS composite strip.

[0025] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include:

[0026] (1) First, the flexible metal strip supports the HTS strip, which improves the supporting strength of the current lead and prevents the current lead from generating stress concentration under large tension, resulting in a significant reduction in the critical current of the HTS strip.

[0027] (2) Secondly, the HTS strips are welded in parallel in the length direction of the flexible metal strip, which avoids the overlap of the HTS strips in the longitudinal direction and reduces the minimum critical bending radius of the pre-prepared high-temperature superconducting current lead. By adopting the technical solution proposed in the present invention, the minimum critical bending radius can be reduced to 5 mm, and the prepared high-temperature superconducting current lead can meet the requirements of Δ(I c / I c0 )>1% and the final bending radius is not less than 5mm, the critical strain is not greater than 0.4%.

[0028] (3) Finally, compared with the prior art, the current lead prepared using the technical solution disclosed in this application can be reused. Specifically, the high-temperature superconducting current lead can be bent within the critical strain range to meet different usage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 Schematic diagram of the high-temperature superconducting current lead structure in an embodiment of the present invention;

[0031] Figure 2 is a partial cross-sectional view along the length direction of a high-temperature superconducting current lead in an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the structure of a high-temperature superconducting current lead with a junction box in an embodiment of the present invention;

[0033] Figure 4 for Figure 3 AA section view in;

[0034] Figure 5 Schematic diagram of the structure of the portion of the electrical connection portion in contact with the flexible metal strip in an embodiment of the present invention.

[0035] Explanation of the accompanying drawings: 1. HTS composite strip; 10. HTS strip; 11. Flexible metal strip; 12. Independent partition; 2. Stabilizer material; 3. Sheath; 30. Part to be clamped; 4. Junction box; 40. Electrical connection part; 400. Slot; 401. Protrusion; 402. Installation part; 41. Pressing part. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] The embodiment of the present invention discloses a high temperature superconducting current lead, such as Figure 1As shown, it includes: an HTS composite strip 1, which is prepared by parallel welding of multiple HTS strips 10 on a flexible metal strip 11 in the length direction; a stabilizer material 2, which is impregnated with the HTS composite strip 1, and the stabilizer material 2 has a temperature higher than the critical temperature of the HTS strip 10 and lower than the thermal degradation temperature of the HTS strip or the melting point of the solder, whichever is smaller.

[0038] The present invention forms an HTS composite strip by parallel welding the HTS strip along the length of the flexible metal strip. First, the flexible metal strip supports the HTS strip, improving the support strength of the current lead and preventing stress concentration in the current lead under large tension, which would significantly reduce the critical current of the HTS strip. Second, the HTS strip is parallel welded along the length of the flexible metal strip, avoiding longitudinal overlap between the HTS strips and reducing the minimum critical bending radius of the pre-prepared high-temperature superconducting current lead. By adopting the technical solution proposed by the present invention, the minimum critical bending radius can be reduced to 5mm, and the prepared high-temperature superconducting current lead can meet the requirements of Δ(I c / I c0 )>1% and the final bending radius is not less than 5mm, the critical strain is not greater than 0.4%; finally, compared with the prior art, the current lead prepared by the technical solution disclosed in this application can be reused. Specifically, the high-temperature superconducting current lead can be bent within the critical strain range to meet different usage conditions.

[0039] It should be noted that the meaning of "pre-prepared" in the present invention is: the critical bending radius of the prepared HTS composite tape before impregnation with the stabilizer material; and the meaning of "prepared" is the critical strain of the HTS composite tape after impregnation with the stabilizer material. "Critical bending radius" and "critical strain" are Δ(I c / I c0 )>1% when the bending radius and strain, where I c is the current value after bending or strain, I co It is the current value before bending or strain.

[0040] It should be noted that the flexible metal strip in the present invention is a steel or copper strip. It not only provides support for the HTS strip but also serves as a current diversion mechanism, ensuring current diversion when the HTS strip's conductivity is limited, thereby increasing the safety margin of the current lead. Preferably, the steel strip is made of stainless steel, and the copper strip is made of pure copper or a copper alloy. The thickness of the flexible metal strip is less than 0.5 mm, preferably 0.1-0.2 mm.

[0041] The stabilizer material is used to keep the current lead structurally stable during handling of the system and during operation of the superconducting system. The stabilizer material is preferably a wax, and the current lead can be heated to melt the wax so that the wax can be bent into a desired shape and then allowed to cool to maintain the desired shape. A suitable wax will have a melting point that exceeds the expected operating temperature of the current lead (for example 77K, or the critical temperature of the HTS tape) or is above room temperature (290K to ensure that the wax is stable at room temperature) but below the degradation temperature of the HTS (i.e., the temperature at which permanent damage to the HTS will occur). If the melting point of the solder in the current lead is below the degradation temperature of the HTS tape, the melting point of the wax is selected to be less than the melting point of the solder. "Above" or "below" in this application does not include the value itself.

[0042] While wax is used herein as an example, other substances having a temperature above room temperature and below the HTS degradation temperature or the melting point of solder, whichever is less, would also be suitable as a stabilizer material for impregnating the HTS current leads.

[0043] One wax that meets the above conditions is beeswax (melting temperature is 60°C and is stable over a low temperature cycle). Where "wax" is used herein, the wax may also be a mixture of different waxes or other materials to achieve the desired properties.

[0044] The HTS tape in this application comprises a protective layer, a superconducting layer, a buffer layer, and a Hastelloy alloy, arranged in this order. The protective layer is made of silver, while the superconducting layer in this embodiment is made of REBCO. The buffer layer includes, but is not limited to, one or more of CeO2, YSZ (yttrium-stabilized zirconia), and Y2O3.

[0045] The device further comprises a sheath 3, which wraps the stabilizer material 2. The sheath is made of heat shrinkable material, wrapping the stabilizer material, the flexible copper plate and the HTS tape, and is preferably made of a material with lower thermal conductivity than the superconducting tape, such as glass fiber reinforced plastic (GFRP).

[0046] Specifically, such as Figure 1 As shown, the sheath 3 has an elliptical cross-section, with the major axis of the ellipse coinciding with the width of the metal sheet. This elliptical cross-section of the sheath facilitates limiting the direction in which the operator or bending equipment bends the current lead during subsequent deformation, ensuring that the current lead bends along the minor axis of the ellipse, avoiding bending along the major axis of the ellipse, or limiting the degree of bending.

[0047] Preferably, the stabilizer material is wax, the flexible metal strip is copper, and the Hastelloy side of the HTS strip is welded to the flexible metal strip via a PbSn filler metal. The thickness of the weld layer is 0.05-0.1 mm. Copper strip has excellent electrical conductivity and can effectively divert current when the current carrying capacity of the HTS strip decreases. Furthermore, the PbSn filler metal is used to coordinate the deformation stress between the HTS strip and the flexible metal strip. If the PbSn filler metal is too thick, the tensile or compressive stress exerted on the HTS strip when the current lead bends is large, reducing the critical current carrying capacity of the HTS strip. However, if the PbSn filler metal is too thin, the coordination between the flexible metal strip and the HTS strip is poor, and the tensile or compressive stress exerted on the HTS strip is still large. Based on these considerations, when using PbSn filler metal, a weld layer thickness of 0.05-0.1 mm can effectively coordinate the HTS strip and the flexible metal strip, reducing the tensile or compressive stress exerted by the flexible metal strip on the HTS strip.

[0048] Based on the selection of the above materials, in the embodiment of the present invention, the relationship between the major axis a and the minor axis b of the ellipse and the width w of the metal plate satisfies:

[0049]

[0050] b=λ2a

[0051] Wherein, λ1 is the first correction coefficient, with a value range of 1.2-1.5, λ2 is the second correction coefficient, with a value range of 0.4-0.6, and w0 is the standard width, with a value range of 10-15mm. The major axis a and minor axis b in the present invention can be the external elliptical dimensions of the sheath cross section, or the internal elliptical dimensions of the sheath cross section. Since the sheath thickness does not exceed 3mm, it has little effect on the calculation results, and the internal elliptical dimensions of the sheath cross section are preferably used. In the embodiment of the present invention, 60Sn-40Pb tin material is used for welding, and the value of λ1 is 1.2, the value of λ2 is 0.4, and the value of w0 is 10mm.

[0052] In order to further increase the critical strain of the prepared high-temperature superconducting current lead, such as Figure 2As shown, the welding area between the HTS tape 10 and the flexible metal strip 11 is composed of multiple independent partitions 12, and the distance L between two adjacent independent partitions 12 does not exceed 2mm. When the current lead is bent upward or downward, the space formed between the two adjacent independent partitions allows the HTS tape to deform, thereby increasing the critical strain of the prepared high-temperature superconducting current lead. However, it should be pointed out that the reason why L is selected to be no more than 2mm is that L is coordinated with the thickness of the welding layer to prevent the melted wax from entering the space formed between the two adjacent independent distributions from the openings on both sides, thereby limiting the deformation ability of the prepared high-temperature superconducting current lead. With this technical solution, when the width of the independent partition is 4mm and the length is 4mm, the minimum critical bending radius can be reduced to 4.5mm, and the prepared high-temperature superconducting current lead can meet the requirements of Δ(I c / I c0 )>1% and the final bending radius is not less than 4.5mm, the critical strain is not greater than 0.5%.

[0053] However, in the above solution, part of the space is filled with wax. Based on the above considerations, the thickness t of the welding layer and the distance L between the independent partitions satisfy:

[0054] s=tL

[0055] L=λ3t 2 / 3

[0056] Where s is the preset area value, which is related to the stabilizer material used. In the embodiment of the present invention, beeswax is used and the value is 0.1mm 2 λ3 is the third correction coefficient, which has a value of 3-10, and is 5 in the embodiment of the present invention. The above solution allows beeswax to enter the space between the two adjacent independent partitions through the pores on both sides, reducing the critical strain value of the prepared current lead. Using this technical solution, when the width of the independent partition is 4mm and the length is 4mm, the minimum critical bending radius can be reduced to 4.1mm, and the prepared high-temperature superconducting current lead can meet the requirements of Δ(I c / I c0 )>1% and the final bending radius is not less than 4.1mm, the critical strain is not greater than 0.58%.

[0057] like Figure 3 and 4 As shown, this embodiment of the present invention further includes a junction box 4 located at each end of the HTS composite strip. Each junction box 4 is electrically connected to the HTS composite strip 1 and configured to provide electrical connections to external components. It should be noted that the HTS composite strip in this embodiment of the present invention has only two connection ends, so junction boxes 4 only need to be provided at these two ends.

[0058] Specifically, the two ends of the sheath 3 have a clamping portion 30; the junction box 4 includes an electrical connection portion 40 and a clamping portion 41 rotatably connected to the electrical connection portion. When the clamping portion 41 is rotated and tightened, the electrical connection portion 40 and the clamping portion 41 clamp the clamping portion 30.

[0059] It can be understood that the clamping part 41 is connected to the electrical connection part 40 by a threaded connection, and the outer side of the electrical connection part 40 is provided with a thread that engages with the inner side of the clamping part. By tightening the clamping part, the clamping part 30 of the sheath 3 is clamped and connected.

[0060] Specifically, such as Figure 4 and 5 As shown, the electrical connection portion 40 of the junction box 4 consists of two parts, with a slot 400 located at the junction of the two parts. The slot 400 is used to receive the HTS composite strip 1. A protrusion 401 is provided on the side of the HTS composite strip 1 that contacts the flexible metal strip. The height of the protrusion is no more than ¾ of the thickness of the flexible metal strip 11. The pressing surface of the protrusion 401 is planar, with a total pressing surface area of ​​1 / 10-3 / 10 of the contact area between the slot and the HTS composite strip. The protrusion 401 is used to press the HTS composite strip between the two parts of the electrical connection portion 40. This size restriction prevents excessive or insufficient pressure on the HTS strip, which could affect the current carrying capacity of the connection. Furthermore, the force acts on one side of the flexible metal strip, which acts as a buffer, further reducing the impact of pressure on the critical current carrying capacity of the HTS strip.

[0061] Preferably, the thread between the clamping part 41 and the electrical connection part 40 has a certain inclination angle, that is, as the clamping part is tightened, the extrusion force between the two parts of the electrical connection part 40 becomes greater. At this time, it is only necessary to install the two parts of the slot and the HTS belt. As the clamping part is tightened, the protrusion 401 in the slot 400 squeezes one side of the flexible metal strip, thereby realizing the installation of the HTS composite strip.

[0062] Preferably, Figure 5 As shown, the electrical connector 40 includes a mounting portion 402 for threaded engagement with the compression portion, and a connection portion for connection to the HTS composite strip 1. The connection portion includes a slot 400 and a protrusion 401 on the slot surface that mates with the flexible metal surface of the HTS composite strip. After the two parts of the electrical connector 40 are assembled, the cross-section of the connection portion has the same shape as the sheath, but is larger than the sheath, facilitating subsequent preparation and installation.

[0063] The high-temperature superconducting current lead including the junction box can be manufactured by the following steps:

[0064] 1. Prepare HTS tape and flexible metal strip of the same length;

[0065] 2. Weld the HTS strip along the width direction of the flexible metal strip to prepare an HTS composite strip. To facilitate the control of welding thickness, welding is performed using welding sheets. That is, welding sheets of a certain thickness are prepared and connected by heating and pressurizing.

[0066] 3. Prepare a sheath longer than the HTS tape or flexible metal material;

[0067] 4. Assemble one end of the HTS composite tape with the electrical connection portion 40 and install it into the sheath, and seal one side of the sheath through the electrical connection portion 40;

[0068] 5. Add wax pellets to the required amount from the opening on the other side of the sheath;

[0069] 6. Install the electrical connector on the other end of the HTS composite strip and heat it. The heating process is to heat from the center to the ends. The sheath shrinks and exerts pressure on the wax, which expel the gas from both sides.

[0070] 7. Heating both sides of the sheath so that the two sides of the sheath shrink to form a portion to be clamped 30;

[0071] 8. Install the pressing parts 41 on both sides of the electrical connection part.

[0072] If the high-temperature superconducting current lead needs to be pre-fabricated, then after step 5, the semi-finished product can be bent manually or by equipment, and step 6 is performed after the bending process is completed.

[0073] The prepared high-temperature superconducting current lead can be bent according to the specific installation environment without exceeding the critical strain condition proposed by the present invention to meet the installation requirements.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-temperature superconducting current lead, characterized in that: include: HTS composite strips, wherein the HTS composite strips are prepared by parallel welding of multiple HTS strips in the length direction of a flexible metal strip; a stabilizer material impregnated with the HTS composite tape, the stabilizer material having a temperature greater than the critical temperature of the HTS tape and less than the thermal degradation temperature of the HTS tape or the melting point of the solder, whichever is less; a sheath enclosing the stabilizer material; The cross section of the sheath is elliptical, and the major axis of the ellipse coincides with the width direction of the metal strip; The Hastelloy side of the HTS strip is welded to the flexible metal strip via PbSn tin material; The thickness of the welding layer is 0.05-0.1mm; The relationship between the major axis a and minor axis b of the ellipse and the width w of the metal strip satisfies: b=λ2a Where λ1 is the first correction coefficient, λ2 is the second correction coefficient, and w0 is the standard width; The welding area between the HTS tape and the flexible metal strip is divided into multiple independent partitions, and the distance between two adjacent independent partitions does not exceed 2 mm; The thickness t of the welding layer and the distance L between the independent partitions satisfy: s=tL L=λ3t 2 / 3 Where s is the preset area value, and λ3 is the third correction coefficient.

2. The high-temperature superconducting current lead according to claim 1, characterized in that: The stabilizer material is wax; The flexible metal strip is a copper strip.

3. The high-temperature superconducting current lead according to claim 1, characterized in that: Also includes: A junction box is located at each end of the HTS composite tape, each junction box being electrically connected to the HTS composite tape and configured to make an electrical connection to an external component.

4. The high-temperature superconducting current lead according to claim 3, characterized in that: The sheath comprises a sheath, wherein both ends of the sheath have portions to be clamped; The junction box includes an electrical connection portion and a pressing portion rotatably connected to the electrical connection portion. When the pressing portion is rotated and tightened, the electrical connection portion and the pressing portion clamp the portion to be clamped.

5. The high-temperature superconducting current lead according to claim 4, characterized in that: The electrical connection portion of the junction box is composed of two parts, and a slot is provided at the junction of the two parts, and the slot is used to receive the HTS composite strip; A protrusion is provided on one side for contacting the flexible metal strip of the HTS composite strip. The height of the protrusion is not greater than 3 / 4 of the thickness of the flexible metal strip, and the pressing surface of the protrusion is planar. The total area of ​​the pressing surface is 1 / 10-3 / 10 of the contact area between the slot and the HTS composite strip.

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