A composite high temperature superconducting conductor joint compatible with forced flow cooling and electrical connections

Abstract

The application discloses a composite high-temperature superconducting conductor joint compatible with forced flow cooling and electric connection, which can realize compatible current transverse transmission and longitudinal cooling loop between multi-layer parallel solenoid coils. The inside step of the copper terminal is connected with the end metal core pipe of the composite high-temperature superconducting conductor, internal positioning of the high-current superconducting joint is realized, the outside step-shaped structure is assembled with the forced flow cooling pipeline of the low-temperature system, the low-temperature tin material is welded to form a molten pool, and a complete closed loop is formed; the metal plug is inserted into the through hole of the copper terminal during welding, is connected with the end metal core pipe of the conductor, and ensures that the solder tin does not immerse the forced flow cooling loop. While the low-resistance characteristic of the stepped superconducting joint is reserved, the construction of the internal low-temperature forced flow cooling loop of the conductor is completed, large-angle bending at the connection position of the conductor and the low-temperature pipeline is avoided, the flow resistance of the forced flow cooling of the low-temperature system is reduced, and the rapid cooling of the composite high-temperature superconducting conductor is realized.

Description

Technical Field

[0001] This invention relates to the field of high-temperature superconducting technology, specifically to a composite high-temperature superconducting conductor joint that is compatible with forced flow cooling and electrical connection. Background Technology

[0002] High-temperature superconducting materials refer to superconducting materials with a superconducting transition temperature above 77K. Compared to common low-temperature superconducting wires, high-temperature superconducting materials carry higher currents at the same temperature and background magnetic field, thus possessing great application potential in the power field. However, since a single superconducting tape has a limited current carrying capacity, multiple superconducting tapes are typically connected in parallel to form a composite high-temperature superconducting conductor when facing high current carrying capacity and high background magnetic field conditions. This composite conductor serves as the basic unit for manufacturing large electrical equipment (such as superconducting magnetic energy storage devices, superconducting current limiters, and longitudinal field superconducting magnets for fusion reactors). Common high-temperature superconducting conductors come in three forms: TSTC-type stacked twisted conductors, CORC conductors, and RAA conductors. CORC conductors are made by spirally winding multiple superconducting tapes onto a core tube. The superconducting tapes achieve a significant degree of spiral transposition, resulting in a uniform current density distribution. Due to their low overall inductance and simple and reliable winding and forming processes, unlike TSTC conductors which require extensive welding, CORC conductors have become one of the most promising conductor forms for high-temperature superconducting energy storage systems. However, due to the special manufacturing process of high-temperature superconducting tapes, the current-carrying stability of km-scale superconducting tapes is poor, thus posing a risk to the mass production of CORC high-temperature superconducting conductors. One common solution is to fabricate superconducting joints to connect multiple conductors to the target length.

[0003] Currently, there are two common types of CORC connectors. One type involves unwinding the ends of the CORC conductor to expose the internal copper tubing. The superconducting strips at the ends are then sequentially soldered to a metal block, with the internal copper tubing used for current flow and the copper busbar connected to the metal block. For example, when testing the performance of CORC conductors under high background field (19T) and rapid current change (67.8kA / s), PC Michael et al. at MIT unwound the superconducting strips at the ends and soldered them to a conical copper block, obtaining a single-sided connector resistance of approximately 11.5nΩ. The other method involves unwinding each layer of superconducting strip at the conductor's end by a length of the intercept, ensuring each layer can be electrically connected to solder. The conductor is then inserted into a copper terminal with a deep hole, and a cylindrical heater is used to heat the copper terminal while continuously adding solder wire and acid-free flux through the gap between the conductor and the copper terminal. TMulder et al. at CERN tested a CORC stepped connector at 4.5K with a resistance of approximately 30nΩ.

[0004] However, large magnets, as one of the mainstream applications of superconducting materials, are generally assembled from multiple double-panel or solenoid coils. The excitation power supply uses a series configuration, which requires the coils to be electrically connected via composite high-temperature superconducting conductor connectors. Furthermore, the superconducting conductors inside the coils are cooled using forced-flow liquid helium or helium gas, and the connectors of the composite high-temperature superconducting conductors must also be compatible with the practical requirements of cryogenic circuit connections. Therefore, low-resistance high-temperature superconducting connectors that can accommodate both forced-flow cooling and electrical connection are particularly important for the operating parameters and performance of the wound magnets. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a composite high-temperature superconducting conductor joint that is compatible with forced-current cooling and electrical connection. The joint relies on two welding operations on the inner and outer sides of the copper terminals to construct and seal the forced-current channel within the conductor. This achieves compatible lateral current transmission and longitudinal cooling circuits between multi-layer parallel solenoid coils. Because the internal tubing of multi-layer solenoids is too long, series forced-current cooling would result in excessive flow resistance and unsatisfactory cooling effect. Therefore, longitudinal multi-loop cooling is employed. To achieve rapid excitation and reduce power requirements, the multi-layer solenoids are powered in a series connection. This invention selects solders with different melting temperatures, preserving the low-resistance characteristics of the composite high-temperature superconducting stepped joint while exposing the internal metal core of the conductor, forming a complete sealed circuit with the external cryogenic system.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A composite high-temperature superconducting conductor joint compatible with forced-current cooling and electrical connection includes a composite high-temperature superconducting conductor, copper terminals with inner and outer stepped fixing structures, a metal plug, a helium tube, a G10 insulator, and insulating wrapping. The ends of the composite high-temperature superconducting conductor are exposed sequentially according to the length of each layer's intercept, and then soldered after being wrapped with solder to ensure sufficient contact area between the spiral superconducting strip and the solder, reducing the joint resistance. The copper terminals employ a double-sided stepped fixing structure; the inner stepped fixing structure connects to the metal core tube at the end of the composite high-temperature superconducting conductor, achieving internal positioning of the high-current-carrying composite high-temperature superconducting conductor joint. The metal plug... During welding, the front part is inserted into the tail hole of the copper terminal and connected to the metal core tube at the end of the composite high-temperature superconducting conductor to ensure that the solder does not submerge the forced flow cooling circuit. The metal plug is made of stainless steel and is removed from the tail of the copper terminal after welding. The outer step fixing structure of the copper terminal is assembled with the helium tube. After completion, low-temperature solder is used to weld at the step to form a molten pool, constituting a complete and sealed forced flow cooling circuit to ensure no helium leakage. The G10 insulator and the helium tube are connected by threads to ensure the insulation isolation between the cryogenic system and the power supply. The insulation wrapping covers the connection between the G10 insulator and the helium tube. After wrapping, it is cured and formed to ensure the seal at the connection.

[0008] Furthermore, the composite high-temperature superconducting conductor joint relies on two welding operations on the inner and outer sides of the copper terminals to complete the construction and sealing of the forced flow cooling circuit inside the metal core tube of the composite high-temperature superconducting conductor.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] The purpose of this invention is to provide a composite high-temperature superconducting conductor connector that is compatible with forced-flow cooling and electrical connection. Common stepped connectors for composite high-temperature superconducting conductors are manufactured using low-temperature soldering. After melting at high temperatures, the flowing solder flows into the metal core tube, preventing the superconducting conductor's internal core tube from being exposed as a channel for forced-flow cooling. This invention retains the low-resistance characteristics of the stepped connector by pre-placing a non-solderable metal plug to prevent the metal core tube from being filled with solder, thus achieving a complete closed forced-flow loop from the cooling pipeline to the superconducting connector to the composite high-temperature superconducting conductor. Simultaneously, this invention avoids large-angle bends in the forced-flow loop at the connector, helping to control the flow resistance of the low-temperature pipeline and ensuring sufficient mass flow rate and pressure within the pipeline during operation and testing. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention;

[0012] Figure 2This is a schematic diagram of the welding process for the internal channel of a through conductor according to an embodiment of the present invention;

[0013] Figure 3 This is a schematic diagram of a metal plug according to an embodiment of the present invention;

[0014] Figure 4 This is a schematic diagram of the sealing soldering of the outer molten pool and the helium tube according to an embodiment of the present invention.

[0015] In the figure: 1. Composite high-temperature superconducting conductor; 2. Copper terminal; 3. Metal plug; 4. Helium tube; 5. G10 insulator; 6. Insulation wrapping. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figures 1-4 As shown, the composite high-temperature superconducting conductor joint compatible with forced-current cooling and electrical connection of the present invention includes a composite high-temperature superconducting conductor 1, a copper terminal 2 with a double-sided stepped fixing structure, a metal plug 3, a helium tube 4, a G10 insulator 5, and an insulating wrapping 6. The ends of the composite high-temperature superconducting conductor 1 are exposed sequentially according to the length of each layer's intercept, and solder is wound around the surface before welding to ensure sufficient contact area between the spiral superconducting strip and the solder, reducing the joint resistance. The copper terminal 2 adopts a double-sided stepped fixing structure. The inner stepped fixing structure of the copper terminal 2 and the metal core tube of the composite high-temperature superconducting conductor 1 are threaded. During welding, the threads are used to position the stepped joint, ensuring that the central axis of the composite high-temperature superconducting conductor 1 and the copper terminal 2 coincides, guaranteeing that the solder thickness of each layer of superconducting strip current path is the same. The metal plug 3 is inserted into the metal core tube of the composite high-temperature superconducting conductor 1 through the through hole of the copper terminal 2 during welding, and is removed after welding to ensure that the solder does not submerge the forced-current cooling circuit. The forced-flow cooling circuit of the composite high-temperature superconducting conductor is located inside the metal core tube, which is connected to the external helium tube via the aforementioned operation. The outer step fixing structure of the copper terminal 2 is assembled together with the helium tube 4 used for forced-flow cooling in the cryogenic system. After completion, low-temperature solder is used to weld at the step to form a molten pool, constituting a complete closed circuit to ensure no leakage of forced-flow helium. The front end of the helium tube 4 is made of oxygen-free copper, and the rear end is made of stainless steel. The oxygen-free copper tube and the stainless steel tube are connected by a G10 insulator 5. After the G10 insulator 5 is connected to the oxygen-free copper tube and the stainless steel tube, multiple layers of insulating wrapping 6 are wrapped around its surface to complete the sealing and insulation of the helium tube 4.

[0018] As a preferred embodiment of the present invention, the metal plug 3 is made of non-stick stainless steel, which can be completely separated from the solder after welding. The probe at the front of the metal plug 3 is slightly smaller than the size of the conductor core tube to ensure smooth assembly. The rear end of the metal plug 3 is welded with an end, which makes it easy to remove the plug after welding and expose the internal channel of the conductor core tube.

[0019] In a preferred embodiment of the present invention, the copper terminal 2 requires threading at both the inner and outer step fixing structures. The inner thread connects to the metal core tube at the end of the composite high-temperature superconducting conductor 1, and the outer thread connects to the oxygen-free copper tube at the front of the helium tube 4. Both connections are made using threads.

[0020] In a preferred embodiment of the present invention, after the copper terminal 2 is connected to the helium tube 4, it needs to be sealed by welding. The melting point of the selected solder must be lower than that of the solder in the internal stepped joint to prevent internal fixation failure during the welding process. At the same time, the welding surface of the copper terminal 2 needs to be ground before welding to remove the oxide layer and ensure that the low-temperature solder can fully wet the surface of the copper terminal 2.

[0021] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific examples described or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A composite high-temperature superconducting conductor joint compatible with forced-flow cooling and electrical connection, characterized in that: The device includes a composite high-temperature superconducting conductor, copper terminals with inner and outer step fixing structures, a metal plug, a helium tube, a G10 insulator, and insulating wrapping. The ends of the composite high-temperature superconducting conductor are exposed sequentially according to the length of each layer's intercept, and then soldered after being wrapped with solder to ensure sufficient contact area between the spiral superconducting strip and the solder, reducing the joint resistance. The copper terminals employ a double-sided step fixing structure; the inner step fixing structure connects to the metal core tube at the end of the composite high-temperature superconducting conductor, achieving internal positioning of the high-current-carrying composite high-temperature superconducting conductor joint. During soldering, the front of the metal plug is inserted into the tail hole of the copper terminal. In the process, a metal core tube is connected to the end of the composite high-temperature superconducting conductor to ensure that the solder does not submerge the forced-flow cooling circuit; the metal plug is made of stainless steel and is removed from the tail of the copper terminal after welding; the outer step fixing structure of the copper terminal is assembled with the helium tube, and after completion, low-temperature solder is used to weld at the step to form a molten pool, constituting a complete and sealed forced-flow cooling circuit to ensure no helium leakage; the G10 insulator and the helium tube are connected by threads to ensure the insulation isolation between the cryogenic system and the power supply; the insulation wrapping covers the connection between the G10 insulator and the helium tube, and after wrapping, it is cured to ensure the seal at the connection.

2. The composite high-temperature superconducting conductor joint compatible with forced-flow cooling and electrical connection according to claim 1, characterized in that: The composite high-temperature superconducting conductor joint relies on two welding processes, one on the inner and one on the outer side of the copper terminal, to complete the construction and sealing of the forced flow cooling circuit inside the metal core tube of the composite high-temperature superconducting conductor.

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