JP7739211B2 - Stacked high-temperature superconducting coil device - Google Patents

Description

An embodiment of the present invention relates to a stacked-type high-temperature superconducting coil device in which multiple high-temperature superconducting coils are stacked, each made by winding high-temperature superconducting wire around a bobbin.

Stacked high-temperature superconducting coil devices, in which multiple superconducting coils, each made by winding high-temperature superconducting wire around a bobbin, are stacked in the central axial direction, are subjected to electromagnetic forces due to the self-magnetic field when current is applied and external magnetic fields. These electromagnetic forces generate hoop stress, which is electromagnetic stress that causes the superconducting coil to expand in the radial direction, and axial compressive stress, causing the winding portion of the superconducting coil to deform in the radial and axial directions. If this hoop stress or axial compressive stress exceeds the allowable stress of the superconducting wire, the superconducting properties will deteriorate.

JP 2013-219196 A

As a result, a configuration has been considered in which a retaining ring made of reinforcing wire such as metal tape is placed around the outer periphery of the superconducting coil to suppress radial deformation of the superconducting coil, thereby reducing the hoop stress acting on the superconducting wire and preventing deterioration of the superconducting properties.

However, with this configuration, the width of the reinforcing wire is limited by the height of each pancake coil, so it is not possible to reduce the stress generated by axial compressive stress or suppress deformation. Therefore, when a strong magnetic field generates a high electromagnetic force, there is a risk that the superconducting characteristics will deteriorate due to axial compressive stress. Furthermore, if the superconducting coil moves even slightly due to axial deformation, the imbalance in electromagnetic force can destroy mechanically weak points such as the connections between the superconducting coils, and in the worst case scenario, cause them to burn out.

The problem that this invention aims to solve is to provide a stacked high-temperature superconducting coil device that prevents deformation of the superconducting coil due to axial compressive stress, even when a strong electromagnetic force is generated by a strong magnetic field.

To solve the above problem, the stacked high-temperature superconducting coil device of this embodiment has a pancake-shaped superconducting coil formed by concentrically winding high-temperature superconducting tape wire around an insulating bobbin, and a reinforcing wire wound around the outermost periphery of the superconducting coil. The device is equipped with multiple axially stacked pancake coils and axial reinforcing members arranged on the radial outer peripheral surfaces of the reinforcing wire, and at least portions of the outer peripheral surfaces of axially adjacent reinforcing wires are connected via the axial reinforcing members.

1A and 1B show a stacked high-temperature superconducting coil device according to a first embodiment, in which FIG. 1A is a cross-sectional view thereof, and FIG. 1B is an enlarged view of part A in FIG. 3A and 3B show a superconducting coil according to the first embodiment, in which FIG. 3A is a perspective view thereof, FIG. 3B is a cross-sectional view thereof, and FIG. 3C is an enlarged view of part B of FIG. FIG. 1 is a schematic perspective view of a superconducting tape wire according to a first embodiment. FIG. 10 is a cross-sectional plan view of a stacked high-temperature superconducting coil device according to a second embodiment. 10A and 10B show a stacked high-temperature superconducting coil device according to a third embodiment, in which FIG. 10A is a cross-sectional view thereof, and FIG. 10B is an enlarged view of part C in FIG. 10A and 10B show a stacked high-temperature superconducting coil device according to a fourth embodiment, where (a) is a cross-sectional view thereof and (b) is an enlarged view of part D in (a).

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
A first embodiment will be described with reference to Figures 1 to 3. Figure 1 shows a stacked high-temperature superconducting coil device according to this embodiment, where (a) is a cross-sectional view and (b) is an enlarged view of part A in (a).

The stacked high-temperature superconducting coil device 10 of this embodiment comprises a bobbin 20, superconducting coils 30, reinforcing wires 40, and an axial reinforcing member 50. Multiple superconducting coils 30 are stacked in the direction of the central axis of the superconducting coils 30 (hereinafter also referred to as the axial direction), and a reinforcing wire 40 is wound around the outermost periphery of each superconducting coil 30. Furthermore, an axial reinforcing member 50 is provided on the radial outer periphery of the reinforcing wires 40 so that the outer periphery of each of the reinforcing wires 40 adjacent to each other in the central axis direction of the superconducting coil 30 in the radial direction (hereinafter also referred to as the radial direction) of the superconducting coil 30 is connected axially via the reinforcing member 50.

Here, when distinguishing between the individual stacked reinforcing members 40, they are referred to with subscripts, such as reinforcing wire 40a and reinforcing wire 40b. Furthermore, the white arrows in the drawings indicate radial and axial electromagnetic forces, with solid arrows indicating the radial direction and dashed arrows indicating the central axis of the superconducting coil 30, respectively.

As shown in Figure 2, the superconducting coil 30 is formed by overlapping a superconducting tape wire 30a and an insulating tape wire 30b and spirally winding them around an insulating spool 20 made of an insulating material such as glass fiber reinforced plastic or reinforced PTFE (polytetrafluoroethylene) to form a winding portion 31. Furthermore, when multiple superconducting coils 30 are stacked, insulating layers 32 are formed on the top and bottom surfaces of the winding portion 31 to insulate and protect the winding portion 31 from the winding portions of other layers.

The superconducting coil 30 is integrally impregnated and hardened with a resin such as epoxy (not shown), which suppresses mechanical movement of the superconducting tape wire 30a when the superconducting coil 30 is in use and maintains its strength. It also provides insulation protection between the turns of the superconducting tape wire 30a, preventing quenching, a condition that destroys the superconducting state of the superconducting coil 30.

As shown in FIG. 3, the superconducting tape wire 30a has a tape substrate 33, an intermediate layer 34, and a superconducting layer 35, both surfaces of which are coated with a stabilizing layer 36. An orientation layer 37 may be provided between the tape substrate 33 and the intermediate layer 34, and a protective layer 38 may be provided between the superconducting layer 35 and the stabilizing layer 36.

The tape substrate 33 is provided for purposes such as maintaining the strength of the superconducting tape wire 30a, and is made of a material such as a high-strength metal, such as Hastelloy (registered trademark) or a Ni-based alloy such as NiW.

The intermediate layer 34 is a diffusion prevention layer made of a material such as cerium oxide, yttria-stabilized zirconia (YSZ), magnesium oxide, yttrium oxide, ytterbium oxide, or barium zirconia, and is formed on the tape substrate 33.

The superconducting layer 35 is made of a superconductor thin film having, for example, an RE123-based composition (RE1B2C3O7, etc.). The "RE" in "RE1B2C3O7" stands for at least one of a rare earth element (e.g., neodymium (Nd), gadolinium (Gd), holmium (Ho), samarium (Sm), etc.) and yttrium, "B" stands for barium (Ba), "C" stands for copper (Cu), and "O" stands for oxygen (O).

The stabilization layer 36 is provided for purposes such as preventing the superconducting layer 35 from burning if excessive current flows through it, and is made of, for example, conductive silver.

The orientation layer 37 is provided for purposes such as orienting the intermediate layer 34 on the tape substrate 33, and is made of, for example, magnesium oxide (MgO). Note that this can be omitted if an oriented substrate is used.

The protective layer 38 is provided to prevent the superconducting layer 35 from deteriorating due to exposure to moisture in the air, and is made of, for example, silver. Like the stabilizing layer 36, the protective layer 38 also serves to prevent the superconducting layer 35 from burning if excessive current flows through it.

The tape width w of such a multi-layered superconducting tape wire 30a is, for example, 4 to 12 mm, and the thickness t is 0.1 to 0.2 mm. Furthermore, while the superconducting tape wire 30a has excellent mechanical strength in the longitudinal direction, it is characterized by being vulnerable to tensile stress (peel stress) in the direction perpendicular to the tape surface.

In addition, the superconducting tape wire 30a may be coated with an insulating material such as polyimide or polyimide amide to form an insulating coated superconducting tape wire.

The reinforcing wire 40 is preferably made of a high-strength metal such as a copper alloy, aluminum alloy, stainless steel, or nickel-based alloy.

The axial reinforcing member 50 is preferably made of a material with a Young's modulus equal to or greater than that of the reinforcing wire 40. Furthermore, a non-magnetic material that is not magnetized by the magnetic field generated by the stacked high-temperature superconducting coil device 10 is preferred. Suitable materials include high-strength copper alloys such as CuNi, CuBe, and C6782, aluminum alloys such as Al-Mg-based A5083 and Al-Zn-Mg-based A7024 and A7003, stainless steel, and nickel-based alloys such as Inconel (registered trademark) and Hastelloy (registered trademark), and combinations of these metals are also suitable.

Methods for forming the axial reinforcing member 50 include fitting a ring-shaped member onto the superconducting coil 30, or winding a plate material with a width that matches the stack height of the superconducting coil 30. Alternatively, the axial reinforcing member 50 may be formed by connecting and integrating ring-shaped members that have been divided in the axial direction.

For ease of manufacturing, the axial reinforcing member 50 and the reinforcing wire 40, and the turns of the plate material when it is wound, may be left unattached. However, to achieve structural integration, they may be secured together with an adhesive layer such as a synthetic resin (not shown) such as epoxy, an adhesive, or solder.

Next, we will explain the operation of the stacked high-temperature superconducting coil device 10.

In the stacked high-temperature superconducting coil device 10 of this embodiment configured as described above, the reinforcing wires 40a and 40b adjacent in the axial direction are connected via an axial reinforcing member 50.

With this configuration, even if the superconducting coil 30 attempts to deform in the axial direction due to electromagnetic force, the axial reinforcing member 50 suppresses the axial deformation of the superconducting coil 30. Furthermore, even in cases where a strong electromagnetic force is generated due to a strong magnetic field, suppressing deformation of the superconducting coil 30 reduces the axial compressive stress acting on the superconducting tape wire 30a, allowing for stable current flow without degrading the superconducting properties.

In addition, by setting the thermal contraction rate of the axial reinforcing member 50 to be greater than the thermal contraction rate of the superconducting coil 30 equipped with the reinforcing wire 40, the difference in thermal contraction can be used to more firmly integrate the axial reinforcing member 50 and the reinforcing wire 40.

The same effect can be expected when a double-pancake-shaped superconducting coil is used for the superconducting coil 30, and a single-pancake-shaped superconducting coil and a double-pancake-shaped superconducting coil may be combined and stacked. Furthermore, the shape of the superconducting coil 30 is not limited to a circular shape; similar effects can be obtained with non-circular coils consisting of straight and arc sections, elliptical coils, and three-dimensional coils wound three-dimensionally, such as saddle coils.

As described above, in this embodiment, reinforcing wires 40 that are provided on the outer periphery of the superconducting coil 30 and that are adjacent in the axial direction are connected via an axial reinforcing member 50. This configuration makes it possible to suppress axial deformation of the superconducting coil 30, even in cases where a strong electromagnetic force is generated by a strong magnetic field, and enables stable current flow without degrading the superconducting properties.

Second Embodiment
The second embodiment will be described with reference to Fig. 4. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. Fig. 4 is a plan cross-sectional view of a stacked high-temperature superconducting coil device according to the second embodiment. As shown in Fig. 4, in this embodiment, the axial reinforcing member 50 is divided into two in the circumferential direction of the superconducting coil 30, and the two axial reinforcing members 50a, 50b are connected at a portion of the circumferential direction by fastening bolts and nuts 51.

In this embodiment, configured as described above, tightening the bolts and nuts 51 allows the outer periphery of the reinforcing wire 40 to be compressed radially by the two axial reinforcing members 50a and 50b.

This configuration allows the outer periphery of the reinforcing wire 40 to be compressed radially, thereby more firmly integrating the axial reinforcing member 50 and the reinforcing wire 40. Therefore, compared to the first embodiment, axial deformation of the superconducting coil 30 can be further suppressed, and even in cases where a strong electromagnetic force is generated by a strong magnetic field, stable current can be passed through the coil without degrading its superconducting properties.

The connection method is not limited to the bolt and nut method, and may also be welding or crimping. In this case, the two axial reinforcing members 50a, 50b can be connected while the outer periphery of the reinforcing wire 40 is separately compressed. Furthermore, although the embodiment has been described with an example in which the axial reinforcing member 50 is divided into two pieces in the circumferential direction, it is of course possible to divide it into three or more pieces in some cases.

(Third embodiment)
The third embodiment will be described with reference to Fig. 5. The same components as those in the first and second embodiments are designated by the same reference numerals, and detailed descriptions thereof will be omitted. Fig. 5 shows a stacked high-temperature superconducting coil device according to the third embodiment, with (a) being its cross-sectional view and (b) being an enlarged view of part C in (a).

In this embodiment, as shown in Figure 5, the axial reinforcing member 50 further includes an extension portion 52 extending radially inwardly of the superconducting coil 30 so as to axially connect at least a portion of the surfaces of the opposing axial end portions of the reinforcing wires 40c and 40d.

In this embodiment, the gap between the opposing axial ends of the reinforcing wires 40c and 40d is filled by the extension 52 of the axial reinforcing member 50.

With this configuration, the gap between the opposing axial ends of the reinforcing wires 40c and 40d is filled and connected by the extension 52 of the axial reinforcing member 50, further suppressing axial deformation of the superconducting coil 30 due to electromagnetic force compared to the first and second embodiments. Therefore, even in cases where a strong electromagnetic force is generated by a strong magnetic field, stable current flow can be achieved without degrading the superconducting properties.

The extension portion 52 need only be continuously connected to the axial reinforcing member 50, and does not have to be formed by machining; the extension portion 52 may be manufactured separately and then integrated.

(Fourth embodiment)
The fourth embodiment will be described with reference to Fig. 6. The same components as those in the first to third embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. Fig. 6 shows a stacked high-temperature superconducting coil device according to this embodiment, with (a) being its cross-sectional view and (b) being an enlarged view of part D in (a).

In this embodiment, as shown in Figure 6, the radial thickness of the axial reinforcing members 50 provided on the radial outer peripheral surfaces of the reinforcing wires 40e, 40f varies depending on the axial position, and the thickness at positions closer to the axial center is relatively thicker than the thickness at the axial ends. Here, the axial center refers to the axial center of the stacked superconducting coils 30.

The axial compressive stress of the superconducting coil 30 is highest near the axial center of the superconducting coil 30. In other words, when multiple superconducting coils 30 are stacked, the compressive stress acting on the superconducting coil 30 located in the center is the highest. In this embodiment configured in this manner, the radial thickness of the axial reinforcing member 50 becomes relatively thicker near the axial center where the axial compressive stress is higher.

By adopting this configuration, axial deformation of the superconducting coils 30 located near the axial center of the stacked superconducting coils 30, which are subjected to high compressive stress, can be further suppressed compared to the first to third embodiments. Therefore, even in cases where a strong electromagnetic force is generated by a strong magnetic field, stable current flow can be achieved without degrading the superconducting properties.

In at least one embodiment described above, reinforcing wires that are provided on the outer periphery of the superconducting coil and adjacent in the axial direction are connected via an axial reinforcing member. This configuration makes it possible to suppress axial deformation of the superconducting coil, even in cases where a strong electromagnetic force is generated by a strong magnetic field, and allows stable current flow without degrading the superconducting properties.

While several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

10...Stacked high-temperature superconducting coil device, 20...winding frame, 30...superconducting coil, 30a...superconducting tape wire, 30b...insulating tape wire, 31...winding portion, 32...insulating layer, 33...tape substrate, 34...intermediate layer, 35...superconducting layer, 36...stabilizing layer, 37...orientation layer, 38...protective layer, 40, 40a, 40b, 40c, 40d, 40e, 40f...reinforcing wire material, 50, 50a, 50b...axial reinforcing member, 51...bolt nut, 52...extension portion.

Claims (5)

a pancake coil including a pancake-shaped superconducting coil formed by concentrically winding a high-temperature superconducting tape wire around an insulating bobbin, and a reinforcing wire wound around the outermost periphery of the superconducting coil, the pancake coil being stacked in the axial direction;
an axial reinforcing member disposed on a radially outer peripheral surface of the reinforcing wire,
The reinforcing wires adjacent in the axial direction are connected to each other at least in part of their outer circumferential surfaces via the axial reinforcing member,
The axial reinforcement member further has an extension portion extending in an inner circumferential direction so as to axially connect at least a portion of the surfaces of the opposing axial end portions of the axially adjacent reinforcing wires via the axial reinforcement member. 2. The stacked high-temperature superconducting coil device according to claim 1 , wherein the axial reinforcing member is formed by winding a metal plate material. 3. The stacked high-temperature superconducting coil device according to claim 1 , wherein the axial reinforcing member is formed by connecting a plurality of members. 4. The stacked high-temperature superconducting coil device according to claim 1, wherein the thermal contraction rate of the front axial reinforcing member is greater than the thermal contraction rate of the superconducting coil. 5. The stacked high-temperature superconducting coil device according to claim 1, wherein the front axial reinforcing member is made of a high-strength metal containing at least one of a copper alloy, an aluminum alloy, a stainless steel, and a nickel-based alloy.