A stepped high-temperature superconducting CICC conductor with high current-carrying capacity

Abstract

The present invention belongs to the field of superconducting technology, and particularly relates to a stepped high-temperature superconducting CICC conductor with high current-carrying capacity. The present invention includes a cooling medium channel, a conductor skeleton, stepped high-temperature superconducting strands, and a metal sheath. A circular hole is opened in the center of the conductor skeleton to form the cooling medium channel, and the cooling medium passes through the cooling medium channel; the conductor skeleton is provided with stepped helical grooves for installing the stepped high-temperature superconducting strands along the circumferential direction; the metal sheath is a hollow structure, sleeved outside the conductor skeleton, its inner wall contacts the outer wall of the conductor skeleton, and at the same time, the stepped high-temperature superconducting strands and the cooling medium channel are covered therein. The present invention can improve the space utilization rate of the existing TSTC type high-temperature superconducting CICC conductor and enable it to have a higher current-carrying capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of superconductivity, and particularly relates to a stepped high-temperature superconducting CICC conductor with high current-carrying capacity. Background Art

[0002] The critical transition temperatures (Tc) of practical low-temperature superconductors NbTi and Nb3Sn are approximately 9.2 K and 18.1 K respectively, and they usually operate in the liquid helium temperature range (4.2 K); while the Tc of the first-generation high-temperature superconductor (Bi-based) is about 108 K, and the Tc of the second-generation high-temperature superconductor (RE-based) is about 90 K, and they usually operate in the liquid nitrogen temperature range (77 K).

[0003] Compared with the first-generation high-temperature superconducting tapes and low-temperature superconducting (NbTi and Nb3Sn) materials, the second-generation high-temperature superconducting tapes have the advantages of higher current-carrying capacity, critical magnetic field, and mechanical strength. The high-temperature superconducting conductors prepared based on them are more suitable for the magnet systems of large-scale high magnetic field devices, such as the magnet systems of nuclear fusion devices, large particle colliders, and accelerators. Currently, high-temperature superconducting conductors mainly include three types: Roebel type, TSTC type, and CORC type. Among them, the Roebel conductor is woven from high-temperature superconducting tapes laser-cut into positive and negative trapezoidal shapes. To make a conductor with the same current-carrying capacity, more tapes are required than the other two types of conductors, so the manufacturing difficulty is high and the economy is poor; the CORC type conductor is formed by winding the tape around a circular metal core. For a CORC type conductor with the same current-carrying capacity, compared with the TSTC type conductor, more tapes are used, and the volume is large and the economy is poor. The TSTC type conductor is a conductor formed by simple stacking and twisting. For a conductor with the same current-carrying capacity, fewer tapes are required compared with the other two types of conductors, so the preparation process is simple and the economy is high.

[0004] Currently, the TSTC type CICC conductors designed for the magnet systems of high-field devices such as fusion reactors, large particle colliders, and large accelerators are all prepared by multi-strand square stacked conductors, and the space utilization rate of the conductor structure is relatively low, which limits the improvement of the current-carrying capacity of the conductor. In view of the above problems, the present invention provides a TSTC type high-temperature superconducting CICC conductor structure with high current-carrying capacity and mechanical properties suitable for large-scale high magnetic field magnets. Summary of the Invention

[0005] The purpose of the present invention is to provide a stepped high-temperature superconducting CICC conductor with high current-carrying capacity. Based on the current TSTC type conductor, it can improve the space utilization rate of the existing TSTC type high-temperature superconducting CICC conductor and enable it to have a higher current-carrying capacity.

[0006] The technical solution adopted by the present invention:

[0007] A stepped high-temperature superconducting CICC conductor with high current-carrying capacity, comprising a cooling medium channel, a conductor skeleton, stepped high-temperature superconducting strands, and a metal sheath. A circular hole is opened in the center of the conductor skeleton to form the cooling medium channel, and the cooling medium passes through the cooling medium channel; the conductor skeleton is provided with stepped helical grooves for installing the stepped high-temperature superconducting strands along the circumferential direction; the metal sheath is a hollow structure, sleeved outside the conductor skeleton, with its inner wall in contact with the outer wall of the conductor skeleton, and at the same time covering the stepped high-temperature superconducting strands and the cooling medium channel.

[0008] A pipe is inserted into the circular hole to form the cooling medium channel.

[0009] The cooling medium is liquid helium, supercritical helium, cryogenic gaseous helium, liquid nitrogen, or liquid hydrogen.

[0010] The stepped high-temperature superconducting strands are formed by stacking steps with different widths and thicknesses in a stepped arrangement that is centrosymmetric. The stepped high-temperature superconducting strands are prepared using second-generation high-temperature superconducting tapes, and each layer of superconducting tape is connected by a soldering material. When soldering, a brazing solder with a melting point lower than 200°C is used.

[0011] The cross-section of the metal sheath is a chamfered square, and the material is stainless steel, copper, aluminum, and their alloys.

[0012] The cross-section of the metal sheath is circular.

[0013] The number of the stepped high-temperature superconducting strands is determined to be 3 or more according to the conductor specifications and performance.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) The present invention provides a stepped high-temperature superconducting CICC conductor with high current-carrying capacity. Compared with a CICC conductor of the same size prepared with square conductor strands, the stepped conductor can accommodate more conductor strands, significantly improving the utilization rate of the space structure, increasing the current density per unit volume of the conductor, and improving the current-carrying capacity; the conductor strands are embedded in the core of the skeleton groove with the same pitch at a certain pitch, which can reduce the AC loss of the conductor. The conductor metal sheath can effectively improve the mechanical strength of the conductor and ensure stability under high fields. In addition, when preparing a magnet, the stepped conductor with high current-carrying capacity can effectively reduce the volume of the magnet, and the preparation process of this type of conductor has a lower difficulty, which is beneficial to the overall economy of conductor applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the prior art solutions, the following will briefly introduce the drawings required for use in the embodiments.

[0017] Figure 1Schematic diagram of a stepped high-temperature superconducting CICC conductor with high current-carrying capacity provided by the present invention;

[0018] Figure 2 is Figure 1 cross-sectional schematic diagram;

[0019] Figure 3 Schematic diagram of another stepped high-temperature superconducting CICC conductor with high current-carrying capacity provided by the present invention;

[0020] Figure 4 is Figure 3 cross-sectional schematic diagram;

[0021] In the figure: 1 - cooling medium channel, 2 - conductor skeleton, 3 - stepped high-temperature superconducting strand, 4 - metal sheath. Specific implementation manner

[0022] The following further elaborates in detail on a stepped high-temperature superconducting CICC conductor with high current-carrying capacity provided by the present invention in conjunction with the accompanying drawings and specific embodiments. Embodiment

[0023] As Figure 1 and Figure 2 shown, a stepped high-temperature superconducting CICC conductor with high current-carrying capacity includes a cooling medium channel 1, a conductor skeleton 2, multiple stepped high-temperature superconducting strands 3, and a metal sheath 4. A circular hole is opened in the center of the conductor skeleton 2 to form the cooling medium channel 1, or a pipe is further inserted into the circular hole to form the cooling medium channel 1;

[0024] The cooling medium is usually liquid helium, supercritical helium, cryogenic gaseous helium, liquid nitrogen, or liquid hydrogen, and is used to maintain the superconducting state of the stepped high-temperature superconducting strand 3.

[0025] In addition to the circular hole opened in the center, the conductor skeleton 2 is provided with stepped spiral grooves for installing the stepped high-temperature superconducting strands 3 along the circumferential direction;

[0026] The metal sheath 4 is a hollow structure, sleeved outside the conductor skeleton 2, with its inner wall in contact with the outer wall of the conductor skeleton 2, and at the same time covering the stepped high-temperature superconducting strands 3 and the cooling medium channel 1.

[0027] The conductor skeleton 2 is processed from a circular long wire. The circular opening at the axis center is the cooling medium channel 1, with a diameter between 2 - 20 mm; the stepped spiral grooves are used to install the stepped conductor strands 3, and their pitch and size specifications are designed according to parameters such as the engineering current density requirement of the conductor, the maximum twist pitch and bending radius of the strands.

[0028] The stepped high-temperature superconducting strand 3 is formed by stacking steps of different widths and thicknesses in a centrally symmetric stepped arrangement. The stepped high-temperature superconducting strand 3 is prepared using second-generation high-temperature superconducting tapes, where the tape width is 1 - 5 mm and the thickness is 0.05 - 0.1 mm. Each layer of superconducting tape is connected by a soldering material. When soldering, a brazing solder with a melting point below 200°C is used, and the solder is tin, lead, and tin-lead alloy. The number of steps of the stepped high-temperature superconducting strand 3 is controlled within the range of 2 - 5 according to the tape width. The thickness of each step is controlled within a reasonable range according to the actual requirements of the conductor, and the thicknesses of different steps of the same strand do not need to be the same and can be adjusted according to the actual structure and performance requirements of the conductor to ensure an increase in current-carrying capacity.

[0029] The cross-section of the metal sheath 4 is a chamfered square, Figure 1 and Figure 2 as shown, the material can be stainless steel, copper, aluminum, and their alloys. Embodiment

[0030] As Figure 3 and Figure 4 shown, the difference between this embodiment and Embodiment 1 is that:

[0031] The cross-section of the metal sheath 4 is circular. Its advantages are that the skin effect and heat dissipation effect during current transmission are better than those of a square cross-section conductor, it is more convenient for processing and manufacturing, and a circular cross-section conductor is more easily bent and formed during magnet manufacturing. The number of stepped high-temperature superconducting strands 3 can be determined to be 3 or more according to the conductor specifications and performance.

[0032] Figures 1 to 4 For the stepped high-temperature superconducting CICC conductor with high current-carrying capacity as shown, where the number of stepped superconducting strands 3 is 9, each strand has a total of 5 steps, the overall height is 5 mm, and the thickness of each step is 1 mm. The widths of the tapes used for each step from the outside to the inside are 5 mm, 4 mm, 3 mm, 2 mm, and 1 mm respectively, and the thickness is 0.1 mm for all. The typical critical current values of the tapes used at 77K @ self-field are: 160 A, 140 A, 130 A, 90 A, and 70 A respectively. Therefore, when this stepped CICC conductor with high current-carrying capacity is at 77K, the ultimate critical current can reach 53.1 kA. If a conductor of this size uses 5-mm square strands, the maximum number of strands of the conductor is 5, and the ultimate critical current at 77K is 40 kA. According to calculations, the critical current of the stepped CICC conductor of the same size is about 33% higher than that of the latter. During the actual preparation process, the thickness of each step of the stepped superconducting strand 3 can also be adjusted to further improve the current-carrying capacity of the conductor. Even calculated according to the same critical performance loss, the current-carrying capacity of the stepped CICC conductor is more than 33% higher than that of the conductor prepared with square strands.

[0033] The above-described embodiments are only used to elaborate the technical solutions of the present invention to help understand the method principles and ideas of the present invention. Within the relevant scope of changes, those skilled in the art can still make corresponding modifications based on the present invention according to specific application requirements.

[0034] A stepped high-temperature superconducting CICC conductor with high current-carrying capacity, comprising a cooling medium channel, a conductor skeleton, multiple stepped superconducting strands, and a metal sheath; the cooling medium channel can directly utilize the central circular hole of the conductor skeleton or a pipe can be inserted into the circular hole; the cooling medium is usually liquid helium, supercritical helium, cryogenic gaseous helium, liquid nitrogen, or liquid hydrogen, which is used to maintain the superconducting state of the superconducting strands; in addition to having a circular hole in the center, the conductor skeleton also has a stepped helical groove for installing the stepped superconducting strands; the metal sheath is a hollow structure, whose inner wall is in contact with the outer wall of the conductor skeleton, and at the same time wraps the conductor strands and the cooling channel inside; compared with conductors of the same size and specification, the current-carrying capacity can be increased by more than 33%.

[0035] The skeleton is processed from a circular long wire. There is a circular opening in the center of the axis, which will become the cooling medium channel or be closely fitted with the cooling pipe, with a diameter between 2 and 20 mm; the stepped helical groove is used to install the conductor strands, and its pitch and size specifications are designed according to the conductor parameters.

[0036] The conductor strands are arranged in a stepped shape that is centrosymmetric by stacked strands of different widths and thicknesses.

[0037] Prepared from second-generation high-temperature superconducting tapes, the tape specifications are: width 1 - 5 mm, thickness 0.05 - 0.1 mm, and each layer of superconducting tape is connected by a soldering material.

[0038] The number of steps of the strands is controlled within the range of 2 - 5 according to the width of the tape. The thickness of each step is controlled according to the actual requirements of the conductor, and the thicknesses of different steps of the same strand do not need to be the same, and can be adjusted according to the actual structure and performance requirements of the conductor to ensure an increase in the current-carrying capacity.

[0039] The cross-section of the sheath is circular or chamfered square, and the material can be stainless steel, copper, or aluminum.

[0040] According to the conductor specifications and performance requirements, the number of stepped conductor strands is 3 or more.

[0041] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A stepped high-temperature superconducting CICC conductor with high current-carrying capacity, characterized in that: it includes a cooling medium channel (1), a conductor skeleton (2), stepped high-temperature superconducting strands (3), and a metal sheath (4). A round hole is opened in the center of the conductor skeleton (2) to form the cooling medium channel (1), and the cooling medium passes through the cooling medium channel (1); the conductor skeleton (2) is provided with stepped helical grooves for installing the stepped high-temperature superconducting strands (3) along the circumferential direction; the metal sheath (4) is a hollow structure, sleeved outside the conductor skeleton (2), its inner wall contacts the outer wall of the conductor skeleton (2), and at the same time wraps the stepped high-temperature superconducting strands (3) and the cooling medium channel (1) inside; a pipe is inserted into the round hole to form the cooling medium channel (1); the cooling medium is liquid helium, supercritical helium, cryogenic gaseous helium, liquid nitrogen or liquid hydrogen.

2. The stepped high-temperature superconducting CICC conductor with high current-carrying capacity according to claim 1, characterized in that: the stepped high-temperature superconducting strands (3) are formed by stacking steps with different widths and thicknesses into a stepped arrangement that is centrosymmetric. The stepped high-temperature superconducting strands (3) are prepared by using second-generation high-temperature superconducting tapes, and each layer of superconducting tape is connected by a soldering material. When soldering, a brazing solder with a melting point lower than 200°C is used.

3. The stepped high-temperature superconducting CICC conductor with high current-carrying capacity according to claim 1, characterized in that: the cross-section of the metal sheath (4) is a chamfered square, and the material is stainless steel, copper, or aluminum.

4. The stepped high-temperature superconducting CICC conductor with high current-carrying capacity according to claim 1, characterized in that: the cross-section of the metal sheath (4) is circular.

5. The stepped high-temperature superconducting CICC conductor with high current-carrying capacity according to claim 1, characterized in that: the number of the stepped high-temperature superconducting strands (3) is determined to be 3 or more according to the conductor specifications and performance.

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