Uninsulated superconducting coil

Abstract

The utility model relates to the technical field of nuclear fusion, and discloses an uninsulated superconducting coil which comprises a coil framework. The superconducting tape is wound on the coil framework to form a multi-turn superconducting tape winding; the metal strip is wound between turns of the superconducting strip; and a welding layer formed by a metal solder is filled between the metal belt and the superconducting belt material. The turn-to-turn resistance of the superconducting tape in the uninsulated superconducting coil can be increased through parallel winding of the metal tape and the superconducting tape, so that the time constant of the uninsulated superconducting coil in the charging and discharging process is reduced, meanwhile, a gap between the metal tape and the superconducting tape is filled with welding flux, and the metal tape and the superconducting tape are welded together through a formed welding layer. The interturn combining capacity of the non-insulation superconducting coil is enhanced, the mechanical stability of the non-insulation superconducting coil is enhanced, meanwhile, the heat capacity of the non-insulation superconducting coil can be increased and a cold conduction channel can be increased by winding and welding a metal belt between turns in parallel, so that the cold conduction effect is enhanced, and the overall performance of the non-insulation superconducting coil is improved.

Description

Technical Field

[0001] This utility model relates to the field of nuclear fusion technology, specifically to a non-insulated superconducting coil. Background Technology

[0002] Uninsulated superconducting coils are coils wound with superconducting tape and without an organic insulating layer between turns. Compared to traditional insulated coils, uninsulated superconducting coils have a more compact structure, stronger mechanical and cooling performance, and can provide higher magnetic field strength, making them suitable for a wider range of applications. Therefore, the mechanical properties, cooling performance, and inter-turn resistivity of uninsulated superconducting coils often have a significant impact on their performance.

[0003] Existing non-insulated superconducting coils often have low inter-turn resistivity, which leads to a large time constant during the charging and discharging process. Furthermore, some non-insulated coils exhibit poor mechanical and cooling performance. Therefore, how to provide sufficient mechanical stability to non-insulated superconducting coils while minimizing inter-turn resistance and increasing cooling performance to improve their overall performance has become an urgent technical problem to be solved. Utility Model Content

[0004] In view of this, the present invention provides a non-insulated superconducting coil to solve the technical problem of how to provide sufficient mechanical stability to the non-insulated coil while minimizing the inter-turn resistance of the coil and increasing the cooling performance to improve the overall performance of the non-insulated superconducting coil.

[0005] This utility model provides a non-insulated superconducting coil, comprising: a coil frame; a superconducting tape wound on the coil frame to form a multi-turn superconducting tape winding; a metal tape wound between the turns of the superconducting tape; and a welding layer formed of metal solder filling the space between the metal tape and the superconducting tape.

[0006] In one embodiment, the width of the metal strip is greater than the width of the superconducting strip.

[0007] In one embodiment, the metal solder forms a solder shell on the surface of the superconducting strip winding; the metal strip separates the solder shells on adjacent turns of the superconducting strip.

[0008] In one embodiment, the metal strip and the superconducting strip are arranged flush on the annular surface of the non-insulated superconducting coil side and alternately arranged with concave and convex surfaces on the annular surface of the other side.

[0009] In one embodiment, the coil frame is further provided with a channel plate perpendicular to the axial direction of the coil frame, and the uninsulated coil is located on both sides of the channel plate; on the side facing the channel plate, the metal strip is flush with the superconducting strip; on the side away from the channel plate, the metal strip and the adjacent superconducting strip are arranged in an alternating convex-concave pattern.

[0010] In one embodiment, the width of the metal strip is 1.1 to 1.5 times the width of the superconducting strip.

[0011] In one embodiment, the metal solder comprises solder.

[0012] In one embodiment, the metal strip comprises a brass strip or a stainless steel strip.

[0013] This application has at least the following beneficial effects.

[0014] By winding metal strips and superconducting strips together, the inter-turn resistance of the superconducting strips in the non-insulated superconducting coil can be increased, thereby reducing the time constant of the non-insulated superconducting coil during charging and discharging. At the same time, by using solder to fill the gaps between the metal strips and the superconducting strips, a weld layer is formed to weld the metal strips and superconducting strips together, enhancing the inter-turn bonding capability of the non-insulated superconducting coil and improving its mechanical stability. In addition, by winding and welding metal strips between the turns, the heat capacity of the non-insulated superconducting coil can be increased, increasing the cooling channels and thus enhancing the cooling effect, thereby improving the overall performance of the non-insulated superconducting coil. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic cross-sectional view of a non-insulated superconducting coil according to an embodiment of the present invention.

[0017] Figure 2 A cross-sectional structural schematic diagram of another non-insulated superconducting coil provided according to an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the cross-sectional structure of a non-insulated superconducting coil impregnated with solder;

[0019] Figure 4 This is a schematic diagram of the cross-sectional structure of a non-insulated superconducting coil welded by brazing;

[0020] Figure 5 yes Figure 2 , Figure 3 and Figure 4 The results of the inter-turn resistivity test for three types of uninsulated superconducting coils are shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0022] This application provides a non-insulated superconducting coil, such as Figure 1 As shown, the non-insulated superconducting coil includes: a coil frame 1 and a superconducting tape 2, which are wound on the coil frame 1 to form a multi-turn superconducting tape winding;

[0023] A metal strip 3 is wrapped around the turns of the superconducting strip 2; a welding layer 4 formed of metal solder is filled between the metal strip 3 and the superconducting strip 2.

[0024] In this embodiment, by winding the metal strip 3 and the superconducting strip 2 together, the inter-turn resistance of the superconducting strip 2 inside the non-insulated superconducting coil can be increased, thereby reducing the time constant of the non-insulated superconducting coil during the charging and discharging process. At the same time, the gap between the metal strip 3 and the superconducting strip 2 is filled with solder, and the formed welding layer 4 welds the metal strip 3 and the superconducting strip 2 together, enhancing the inter-turn bonding capability of the non-insulated superconducting coil and enhancing the mechanical stability of the non-insulated superconducting coil. In addition, by winding and welding the metal strip 3 between the turns, the heat capacity of the non-insulated superconducting coil can be increased, the cooling channels can be increased, and the cooling effect can be enhanced.

[0025] In one embodiment, the width of the metal strip 3 is greater than the width of the superconducting strip 2. The metal strip 3 can effectively isolate the superconducting strips 2 of adjacent turns, prevent direct or indirect contact between the superconducting strips 2, and result in a lower range of inter-turn resistivity fluctuations. It also greatly enhances the overall Joule thermal stability of the uninsulated superconducting coil.

[0026] In one embodiment, to reduce the gap between the metal strip 3 and the superconducting strip 2, enhance the overall cooling performance and mechanical strength of the uninsulated superconducting coil, and to stabilize the inter-turn resistivity, a solder layer 4 is formed to fill the gap between the metal strip 3 and the superconducting strip 2, reducing the solder cavity between them. The solder impregnation method allows the solder to form a solder shell 41 on the surface of the superconducting strip winding. Since the width of the metal strip 3 is greater than the width of the superconducting strip 2, after soldering, see... Figure 2 The uninsulated superconducting coil shown has a metal strip 3 separating the solder shell 41 on the superconducting strip 2 of adjacent turns, to prevent the problem of reduced inter-turn resistivity caused by indirect contact between the superconducting strips 2 of adjacent turns through the metal solder.

[0027] In one embodiment, the width of the metal strip 3 is 1.1 to 1.5 times the width of the superconducting strip 2. For example, taking a 4.0 mm wide strip and a 4.5 mm wide strip as examples, the width of the metal strip 3 can be 5.0 mm. In an optional embodiment, the specific value of the width of the metal strip 3 can be determined according to actual conditions.

[0028] In one embodiment, the metal strip 3 and the superconducting strip 2 are arranged flush on the annular surface of the uninsulated superconducting coil side and alternately arranged with concave and convex surfaces on the other annular surface. This prevents damage to the superconducting strip when removing the solder shell 41, and the alternating concave and convex arrangement enhances the isolation effect of the metal strip on the superconducting strip, further improving the inter-turn resistivity.

[0029] One method for aligning the metal strip 3 and the superconducting strip 2 flush on one side of the annular surface of the uninsulated superconducting coil and alternately arranged with concave and convex sections on the other side is as follows: The coil frame 1 is further provided with a guide plate perpendicular to the axial direction of the coil frame 1, and the uninsulated coil is located on both sides of the guide plate; on the side facing the guide plate, the metal strip 3 is flush with the superconducting strip 2; on the side away from the guide plate, the metal strip 3 and the adjacent superconducting strip 2 are arranged with alternating convex and concave sections. The guide plate is used as an alignment base to align the metal strip 3 and the superconducting strip 2 on the guide plate for winding.

[0030] In one embodiment, the metal strip 3 can be selected from copper strip, brass strip, and stainless steel strip. Brass is an alloy of copper and zinc, and has a relatively high resistivity of 7.1 × 10⁻⁶ at 20°C. -8 Ω·m, 4.66 × 10⁻⁶ at 77 K. -8 Ω·m; in contrast, pure copper is copper, so its resistivity is lower than that of brass, at 1.76 × 10⁻⁶ Ω·m. -8 Ω·m, 2.44 × 10⁻⁶ at 77 K. -9The resistivity of stainless steel at 77 K is 5.4–5.88 × 10⁻⁶ Ω·m. -7 Ω·m.

[0031] The time constant of the superconducting coil during charging and discharging is: τ = L / Rc, where τ is the time constant, L is the coil inductance, and Rc is the inter-turn resistance. It is evident that to reduce the time constant of the coil during charging and discharging, the inter-turn resistance needs to be maximized. Therefore, in this embodiment, the metal strip 3 can be made of brass or stainless steel.

[0032] In another embodiment, since stainless steel has high tensile strength and elastic modulus, using stainless steel strips for winding can provide stable mechanical properties with good resistance to expansion forces for uninsulated superconducting coils. However, metal solder has poor wettability to stainless steel, which easily forms cavities in the solder layer 4, reducing the cooling effect of the uninsulated superconducting coil. Therefore, in this embodiment, stainless steel strips with metal coatings that are easily wetted by solder, or stainless steel strips wrapped with metal materials that are easily wetted by solder, can be used as metal strip 3 and wound with superconducting strip 2. This can provide greater mechanical strength and a larger inter-turn resistivity while minimizing the formation of cavities in the solder layer 4, thus improving the cooling effect of the coil. In this embodiment, the metal coating can be nickel plating, gold plating, copper plating, etc.; the wrapped metal material can be brass, pure copper, gold, silver, etc.

[0033] In one embodiment, the metal solder can be solder, which can be either high-temperature solder or low-temperature solder. Optionally, the metal solder can also be a metal solder with a melting point below 250°C, such as tin-silver-copper solder, bismuth solder, indium solder, etc. Alternatively, silver solder, which has better liquid flowability, can be used to reduce the cavity in the solder layer 4.

[0034] See Figures 2 to 5 As shown, the inter-turn resistivity of a non-insulated superconducting coil without metal strips wound in parallel and the non-insulated superconducting coil in this application are compared, wherein... Figure 2 A schematic diagram of the uninsulated superconducting coil in this application is shown. Figure 3 A schematic diagram of a solder-impregnated, uninsulated superconducting coil is shown. Figure 4 A schematic diagram of a non-insulated superconducting coil welded by brazing is shown; Figure 5 It shows Figure 3 The coil shown is designated as #1. Figure 4 The coil shown is designated as #2. Figure 2 The coil shown represents the inter-turn resistivity test results of three types of uninsulated superconducting coils, designated as #3.

[0035] Specifically, such as Figure 3The diagram shows a non-insulated superconducting coil impregnated with solder. Solder is filled between the superconducting strips 2, and a solder shell 41 is formed on the surface of the superconducting strip winding. The inter-turn resistivity of the coil is measured to be 0.43 μΩ·cm. 2 With low inter-turn resistivity, the time constant of the uninsulated superconducting coil reaches 2090s during the charging and discharging process.

[0036] like Figure 4 The diagram shown illustrates a non-insulated superconducting coil constructed using brazing. This brazed coil connects adjacent layers of superconducting tape 2 by direct heating without external solder. Testing revealed that the inter-turn resistivity of the non-insulated superconducting coil can reach 1.39 μΩ·cm. 2 Compared to solder-impregnated coils, brazed non-insulated superconducting coils exhibit significantly increased inter-turn resistance, and the time constant during charge-discharge processes decreases to 658 s. However, after multiple tests, the inter-turn resistance of the brazed non-insulated superconducting coil remains unstable, and its Joule heating is also unstable during charge-discharge. Research revealed that during brazing, the lack of additional solder leads to irregular solder points at the ends of the non-insulated superconducting coil, caused by melting solder, resulting in unstable inter-turn resistance. Furthermore, the absence of additional solder creates cavities in the weld layer 4 between the superconducting strips 2, further increasing the inter-turn resistivity of the brazed non-insulated superconducting coil. These cavities in the weld layer 4 also severely affect the overall cooling performance of the non-insulated superconducting coil, causing Joule heating instability during charge-discharge.

[0037] like Figure 2 As shown, the non-insulated superconducting coil, which is welded and wound using the metal strip 3 of this application, has its solder shell 41 separated from the superconducting strip 2 by a brass strip larger than the width of the superconducting strip 2. After multiple low-temperature tests, it was found that the inter-turn resistivity of the non-insulated superconducting coil stabilized at 3.5 μΩ·cm. 2 The increased inter-turn resistivity of the non-insulated superconducting coil was maintained within a range of no more than 4%. This increased inter-turn resistivity also reduced the time constant during the charge-discharge process in low-temperature testing to approximately 140 seconds, significantly shortening the time required for voltage stabilization during testing. Multiple tests showed that the low inter-turn resistivity fluctuation also greatly enhanced the overall Joule thermal stability of the non-insulated superconducting coil. Simultaneously, the brass winding also improved the overall mechanical stability of the non-insulated superconducting coil and enhanced its cooling performance.

[0038] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0039] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An uninsulated superconducting coil, characterized by, The application relates to an uninsulated superconducting coil comprising: a coil former; a superconducting tape wound on the coil former to form a plurality of turns of superconducting tape winding; a metal strip wound between the turns of the superconducting tape, and a solder layer formed by a metal solder between the metal strip and the superconducting tape.

2. The uninsulated superconducting coil according to claim 1, wherein: the width of the metal strip is greater than the width of the superconducting tape.

3. The uninsulated superconducting coil of claim 2, wherein, the metal solder forms a solder shell on the surface of the superconducting tape winding; the metal strip separates the solder shells on the superconducting tapes of adjacent turns.

4. The uninsulated superconducting coil of claim 2, wherein, the metal strip and the superconducting tape are arranged in parallel on one annular surface of the uninsulated superconducting coil and are arranged in concave-convex alternation on the other annular surface.

5. The uninsulated superconducting coil of claim 2, wherein, the coil former is further provided with a partition plate perpendicular to the axial direction of the coil former, and the uninsulated superconducting coil is located on both sides of the partition plate; on the side facing the partition plate, the metal strip is arranged in parallel with the superconducting tape, and on the side away from the partition plate, the metal strip and the superconducting tape are arranged in concave-convex alternation.

6. The uninsulated superconducting coil of any one of claims 2 to 5, wherein, the width of the metal strip is 1.1 to 1.5 times the width of the superconducting tape.

7. The insulated superconducting wire of claim 1 wherein, the metal solder comprises a metal solder with a melting point below 250 DEG C.

8. The uninsulated superconducting coil of claim 1, wherein, the metal strip comprises a brass strip or a stainless steel strip.

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