JP7614993B2 - Superconducting coil and superconducting coil device - Google Patents

Description

Embodiments of the present invention relate to superconducting coils and superconducting coil devices that have the ability to prevent thermal runaway or quenching.

Superconducting wires have a critical current, critical temperature, and critical magnetic field that allow them to maintain the superconducting state. Therefore, even if the electrical resistance is nearly zero, it is not possible for an infinite current to flow. When any of the critical values is exceeded, a transition to a normal conductive state, i.e., a quench, occurs.
Such Joule heating in the normal transition region due to quenching can instantly cause thermal runaway in the superconducting coil, and in the worst case scenario, can lead to burning, so protection technology against quenching is essential.

One conventional technique for quench protection is to connect a protective resistor in parallel with the superconducting coil. This method detects the coil voltage and temperature rise that occurs when the coil transitions to a normal conductive state, and uses this as a trigger to cut off the excitation power supply. After cutting off, the superconducting coil and protective resistor form a closed circuit, so the stored energy in the superconducting coil is consumed by Joule heating in the protective resistor placed in the room temperature section, and the current flowing through the coil can be attenuated.

Examples of superconducting wires used in such superconducting coils include high-temperature superconducting wires such as Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ wire and RE ₁ B ₂ C ₃ O ₇ wire. A superconducting coil using high-temperature superconducting wire has a high critical current density even at high temperatures of 20 K to 50 K compared to conventional low-temperature superconducting wires such as NbTi, and therefore enables high current density operation at high temperatures.

However, if a quench occurs during high current density operation, in the temperature range of 20K to 50K, the operating temperature is higher than that of a superconducting coil using low-temperature superconducting wire, so the specific heat is large and the normal transition region expands slowly. In addition, since high current density operation also increases the heat generation density, the quench protection method of the conventional technology described above causes localized thermal runaway and burns out before it can be detected.

Therefore, if the superconducting wires of different turns inside the superconducting coil are short-circuited between the turns, the current flowing through the part where the normal transition has occurred can be diverted to the superconducting wires of different turns. By diverting the current through the normal conductive part, it is possible to suppress localized heat generation and thermal runaway in the normal transition region.
Specifically, a method has been proposed in which a bypass is provided on the side of the winding portion of the superconducting coil along the radial direction of the coil, the bypass being electrically connected to the superconducting wire, thereby short-circuiting the superconducting wire of different turns via the bypass.

Patent No. 6486817

In the above-mentioned conventional superconducting coil, when electrodes are attached to the innermost or outermost circumference and electricity is passed through it, if the superconducting wire connected to the electrodes undergoes a normal conductive transition, there is no path for the current to flow to the electrodes avoiding the superconducting wire that has undergone a normal conductive transition, so the current continues to flow through the superconducting wire that has undergone a normal conductive transition, creating the risk of localized heat generation and burning.

If only a portion of the superconducting wire connected to the electrode undergoes a normal conductive transition, current can flow to the electrode via the portion of the superconducting wire that does not undergo a normal conductive transition. However, this effectively reduces the area of the connection between the electrode and the superconducting wire, which can cause localized heat generation and burnout.

In addition, when the current is diverted from the nth turn of the superconducting wire to the n+1th turn of the superconducting wire, the current can be diverted using the circumferential length of one turn. However, since the electrodes usually have a limited circumferential length, the size of the connection part with the superconducting wire is smaller than the circumferential length of one turn of the superconducting wire.

Therefore, even if only a part of the superconducting wire connected to the electrode undergoes a normal conductive transition, it may generate heat and cause burning.
The embodiments of the present invention have been made to solve such problems, and an object of the present invention is to provide a superconducting coil and a superconducting coil device that are capable of suppressing the occurrence of thermal runaway or quenching.

In order to solve the above problems, the superconducting coil of this embodiment is a superconducting coil comprising a winding section formed by winding a tape-shaped high-temperature superconducting wire in which thin-film layers including a high-temperature superconducting layer are stacked, an inner electrode and/or an outer electrode connected to the high-temperature superconducting wire at the innermost and/or outermost circumferences of the winding section, and a conductive member provided on an end surface perpendicular to the winding axis direction of the winding section, electrically connecting axial ends of the high-temperature superconducting wire to each other and forming a detour, characterized in that the conductive member extends from the winding section to the inner circumference side and/or the outer circumference side in the winding radial direction and is in contact with a surface of the inner electrode and/or the outer electrode perpendicular to the winding axis direction.
Further, the superconducting coil device according to this embodiment is characterized in that a plurality of superconducting coils according to this embodiment are stacked in the winding axis direction.

According to an embodiment of the present invention, it is possible to suppress the occurrence of thermal runaway or quenching in superconducting coils and superconducting coil devices.

A diagram showing the structure of a typical high-temperature superconducting wire. FIG. 1 is a perspective view of a typical superconducting coil. Cross-sectional view of line II-II in Figure 2. FIG. 4 is an enlarged cross-sectional view of region Ω of FIG. 3 . FIG. 4 is a cross-sectional view of a detour made of conductive resin. FIG. 7A is an enlarged cross-sectional view of a region Ω1 in FIG. 6, and FIG. 7B is an enlarged cross-sectional view of a region Ω2. Top view of a superconducting coil with electrodes attached. Overview of a typical superconducting coil device. FIG. 2 is a schematic view of a superconducting coil according to the first embodiment. 11A is an enlarged cross-sectional view of a region Ω3 in FIG. 10, and FIG. 11B is an enlarged cross-sectional view of a region Ω4. FIG. 11 is a schematic view of a superconducting coil according to a second embodiment. 13A is an enlarged cross-sectional view of the vicinity of the inner electrode in FIG. 12, and FIG. 13B is an enlarged cross-sectional view of the vicinity of the outer electrode. 13A is an enlarged cross-sectional view of the vicinity of an inner electrode according to a third embodiment, and FIG. 13B is an enlarged cross-sectional view of the vicinity of an outer electrode. FIG. 13 is a schematic view of a superconducting coil according to a fourth embodiment. FIG. 13 is a configuration diagram of an electrode and a thin-film wire according to a fifth embodiment.

First, we will explain the structure, function and effects of typical high-temperature superconducting wire and superconducting coils.

(High-temperature superconducting wire)
The configuration of a general high-temperature superconducting wire 20 will be described with reference to the configuration diagram of FIG.

As shown in FIG. 1, the high-temperature superconducting wire 20 is generally composed of a tape-shaped thin-film wire in which thin-film layers are stacked. This high-temperature superconducting wire (hereinafter also referred to as "thin-film wire") 20 is, for example, a wire such as an REBCO wire that includes a high-temperature superconducting layer 25 made of rare metal oxide (RE oxide).

The thin-film wire 20 is composed of a substrate 22 made of a high-strength metal material such as a nickel-based alloy, stainless steel, or copper, an intermediate layer 24 formed on the substrate 22, an orientation layer 23 made of magnesium or the like that orients the intermediate layer 24 on the surface of the substrate 22, a high-temperature superconducting layer 25 made of an oxide formed on the intermediate layer 24, a protective layer 26 made of silver, gold, platinum, or the like, and a stabilization layer 21 made of a highly conductive metal such as copper or aluminum.

The intermediate layer 24 prevents thermal distortion caused by thermal contraction of the substrate 22 and the high-temperature superconducting layer 25. The protective layer 26 protects the high-temperature superconducting layer 25 by preventing oxygen contained in the high-temperature superconducting layer 25 from diffusing from the high-temperature superconducting layer 25. The stabilizing layer 21 serves as a bypass path for excess current flowing to the high-temperature superconducting layer 25 to prevent thermal runaway.
The types and numbers of layers constituting the thin film wire 20 are not limited to those described above, and can be changed as necessary.

(Superconducting coil)
FIG. 2 is a perspective view of a typical superconducting coil 10, FIG. 3 is a cross-sectional view taken along line II-II in FIG. 2, and FIG. 4 is an enlarged cross-sectional view of a region Ω in FIG.

2 and 3 is obtained by winding the thin-film wire 20 around the winding form 14 to form a pancake-shaped winding section 12 having a space penetrating the winding axis center C. Note that the superconducting coil 10 may be obtained without the winding form 14 by removing the winding form 14 after forming the winding section 12. A coil formed into a pancake shape by concentrically winding the thin-film wire 20 is called a pancake coil.
As shown in FIG. 2, the direction parallel to the winding axis of the superconducting coil 10 is called the winding axis direction, the direction in which the thin-film wire 20 is wound is called the coil circumferential direction, and the direction in which the thin-film wire 20 is stacked by winding is called the coil radial direction.

The winding section 12 has a pair of winding end surface sections 18 formed by stacking the thin-film wire 20 by winding. In addition, the gap between adjacent turns of the thin-film wire 20 in the superconducting coil 10 is simply referred to as the gap between the coil turns.

As shown in FIG. 4, an insulating member 33 is inserted between the thin-film wire 20 to insulate adjacent turns. An insulating tape made of, for example, polyimide is preferably used as the insulating member 33. The tape-shaped insulating member 33 is inserted between the coil turns by being wound together with the thin-film wire 20.

The superconducting coil 10 may also be impregnated with a sticky insulating material such as epoxy resin. By impregnating with the sticky resin, adjacent thin-film wires 20 and insulating members 33 in the superconducting coil 10 are fixed together, improving the thermal conductivity and mechanical strength of the superconducting coil 10. Note that a sticky insulating material such as epoxy resin can also function as insulating member 33 when inserted between turns, but to ensure reliable insulation between the superconducting coil turns, it is preferable to insulate between the coil turns reliably using tape-like polyimide or the like.

(Detour)
4, the superconducting coil 10 is provided with a detour 19 (also referred to as a "conductive member") made of a conductive member that electrically connects the thin-film wires 20 at different positions in the superconducting coil 10 on at least one side of a pair of winding end surface portions 18. Note that the detour 19 may be provided on both of the pair of winding end surface portions 18.

The material of the detour 19 is selected to have a resistance greater than the resistance of the superconducting coil 10 during normal operation and less than the resistance of the superconducting coil 10 during the normal conductive transition. For example, normal conductive metals such as copper, stainless steel, aluminum, or indium, semiconductors, conductive plastics, ceramic materials, conductive resins, or superconducting materials may be used. Carbon materials such as graphite, carbon fiber, or carbon fiber composites may also be suitably used as the detour 19.

These materials are formed into sheet-like plate materials or foils and connected to the winding portion 12 by crimping or soldering. Alternatively, the detour 19 may be formed by plating or coating one of the winding end faces 18. In particular, forming the detour 19 by plating allows the detour 19 to be made thin, and does not impede the free deformation of the superconducting coil 10. Furthermore, forming the detour 19 by plating or coating allows the thickness of the detour 19 in the winding axis direction to be adjusted, and the resistance value of the detour 19 to be adjusted.

The detour 19 may also be formed by applying a conductive resin layer 36 as shown in FIG. 5. For example, the conductive resin layer 36 may be made by mixing conductive powder 35 into a non-conductive resin. In this case, the volume resistivity of the conductive resin layer 36 can be easily adjusted by changing the proportion and type of conductive powder 35 mixed into the conductive resin layer 36.

As the conductive powder 35, for example, a carbon-based powder such as carbon black, carbon fiber, or graphite is used, but a metal-based powder such as metal fine particles, metal oxide, metal fiber, or whiskers may also be used. Also, the conductive powder 35 may be made by metal-coating fine particles or synthetic fibers.

Furthermore, a conductive resin layer 36 of different composition may be applied to each position of the winding end surface portion 18 to form the detour 19. The conductive resin layer 36 may also be formed by impregnating a part or all of the winding portion 12, including the spaces between adjacent thin-film wires 20 in the coil radial direction.

In this way, the contact area between the conductive resin layer 36 and the thin-film wires 20 can be increased, and the contact resistance between the conductive resin layer 36 and the thin-film wires 20 can be reduced.
Incidentally, adjacent thin-film wires 20 may be in direct contact with each other without using the insulating member 33 between the thin-film wires 20 adjacent in the coil radial direction. In this case, the stabilization layers 21 covering the outer surfaces of adjacent thin-film wires 20 are in contact with each other in the coil radial direction, and are electrically connected to each other, thereby functioning as the detour 19.

(insulating plate)
4, an insulating plate 16 is provided on an end surface of the detour 19 to insulate the detour 19 and the winding portion 12 from adjacent superconducting coils 10, etc. An epoxy resin or fiber-reinforced plastic is preferably used as the insulating plate 16.

(Effects of detours)
Here, the effect of providing the bypass path (conductive member) 19 to suppress the occurrence of thermal runaway or the like will be described.

As the thin-film wire 20 approaches the critical current, which is the limit of the current that can pass through it, an external magnetic field gradually penetrates, and the parts where the superconducting state is locally destroyed undergo a normal conductive transition. The flux flow resistance associated with this local normal conductive transition generates heat due to Joule loss, and if it increases due to an increase in the coil temperature, etc., it can induce thermal runaway or quenching (hereinafter collectively referred to as "thermal runaway, etc.").

By providing a detour 19 to suppress the occurrence of thermal runaway, etc., when local flux flow resistance occurs due to a normal conducting transition in a part of the thin-film wire 20, a part Ia of the current I flowing in the coil circumferential direction can be diverted in the coil radial direction via the detour to the thin-film wire 20 of another adjacent turn (not shown).

Here, the energizing current flowing in the coil circumferential direction decreases from I to I-Ia. At this time, if the resistance of the detour 19 is Ra and the flux flow resistance is R, the current Ia detouring in the coil radial direction is proportional to R/(R+Ra). Therefore, as the flux flow resistance increases, more of the energizing current detouring in the coil radial direction (not shown).
Therefore, it is possible to prevent a large amount of energizing current I from flowing through a normal conductive portion that has locally transitioned to a normal conductive state, and the occurrence of thermal runaway and the like can be suppressed.

When the coil turns are electrically connected via the detour 19, not only when flux flow resistance occurs but also when the superconducting coil 10 is excited from a non-energized state to the rated current value, a portion I' of the energizing current I supplied from the power source due to induced voltage is diverted in the coil radial direction to the thin film wire 20 of the other turns via the detour 19 (not shown). After excitation is complete, no induced voltage is generated, so the current I' flowing through the detour 19 gradually flows in the coil circumferential direction, and it takes time for the magnetic field to reach the designed value.

Therefore, the lower the resistance between the coil turns, the more current is diverted during excitation, and the longer the excitation time becomes unnecessarily. It is preferable to set the resistance Ra of the detour 19 to a small resistance that allows a sufficient amount of current to be diverted to the detour 19 when flux flow resistance occurs, and to a large resistance that does not unnecessarily lengthen the excitation time when exciting the superconducting coil 10 from a non-energized state to the rated current value.

(electrode)
When energizing the above-described superconducting coil 10, both ends of the winding portion 12 need to be electrically connected to terminals of an external power source. Electrodes 40 (inner electrode 40a, outer electrode 40b) are generally used as conductive parts for electrically connecting lead wires drawn from the terminals of the external power source to the superconducting coil 10 (see FIGS. 6 to 8).

The electrodes 40 are electrically connected to the thin-film wire 20 of the innermost and/or outermost turns of the winding section 12 by soldering or the like, and allow the flow of the current I through the superconducting coil 10 to flow in or out. The electrodes 40 electrically connected to the superconducting coil 10 are electrically connected to the lead wires directly or indirectly via other conductive parts, so that the superconducting coil 10 is electrically connected to the terminals of an external power source.

The electrode 40 is preferably made of, for example, copper, silver, gold, indium, or an alloy thereof. The electrode 40 may be formed by replacing a portion of the reel 14 in FIG. 3 with copper, silver, gold, indium, or an alloy thereof.

Figure 6 shows a perspective view of the superconducting coil 10 with the inner electrode 40a attached to the innermost circumference and the outer electrode 40b attached to the outermost circumference, and Figures 7(a) and 7(b) show enlarged cross-sectional views of regions Ω1 and Ω2 in Figure 6.

Here, we will discuss the difference between the circumferential length of the portion where the electrode 40 and the thin-film wire 20 are connected and the circumferential length of the portion where adjacent thin-film wires 20 are connected by a detour 19 within the winding section 12.

If the electrodes 40 used for inputting and outputting the current of the superconducting coil 10 are made larger than necessary, the following disadvantages (1) to (4) arise.
(1) The weight of the entire device increases, (2) The volume of the device increases, (3) The heat capacity increases, and it takes time to heat the thin film wire 20 when soldering it, and (4) The cost of manufacturing the electrodes increases.

Therefore, the electrodes 40 are generally designed to be as small as possible, provided that the heat generated when a current is passed through them does not exceed the cooling capacity of the device.
For this reason, in many cases, the circumferential length of the electrode 40 is designed to be smaller than the circumferential length of the thin-film wire 20 of the turn to which the electrode 40 is connected. For example, the circumferential length of the electrode 40 may be designed to be approximately half the circumferential length of the thin-film wire 20. In addition, the circumferential length of the electrode 40 may be one-tenth or less of the circumferential length of the thin-film wire 20.

In the example shown in FIG. 8, the connection length with the thin-film wire 20 when the inner electrode 40a is attached to the inner circumference side of the coil is L1, and the connection length with the thin-film wire 20 when the outer electrode 40b is attached to the outer circumference side of the coil is L2, which is approximately 1/10 or less of the circumferential length of the thin-film wire 20.

When a thin-film wire 20 that is not adjacent to the inner electrode 40a and the outer electrode 40b undergoes a normal conducting transition, the current can be diverted to an adjacent thin-film wire 20 via a detour 19 using the circumferential length of one turn.

However, when the thin-film wire 20 adjacent to the inner electrode 40a or the outer electrode 40b undergoes a normal conductive transition, the current avoids the normal conductive portion 15 (see Figures 7(a) and (b)), and the effective circumferential length of the connection between the inner electrode 40a or the outer electrode 40b and the thin-film wire 20 becomes even shorter. This causes the problem of increased electrical resistance at the connection, which generates heat.

Furthermore, if a normal conductive transition occurs in a section longer than the circumferential length of the connection between the inner electrode 40a or the outer electrode 40b and the thin-film wire 20, the current cannot avoid the normal conductive portion 15 and flow into the electrode 40, and the current continues to flow through the normal conductive portion 15, causing the problem of heat generation.

(Superconducting coil device)
As shown in FIG. 9, a plurality of superconducting coils 10 may be stacked concentrically in the winding axis direction to form a superconducting coil device 100.

A typical superconducting coil device 100 has a metal plate 41 that is placed across two adjacent superconducting coils 10 among a number of stacked superconducting coils 10. The metal plate 41 is electrically connected to the thin-film wire 20 by soldering or the like, and allows the current I flowing out of one of the two superconducting coils 10 to flow into the other superconducting coil 10.

The metal plate 41 is suitably made of, for example, copper, silver, gold, indium, or an alloy thereof. Focusing on one superconducting coil 10 among the multiple superconducting coils 10 constituting the superconducting coil device 100, the metal plate 41 plays a role in causing the flow of the current I passing through the superconducting coil 10 to flow in or out, and can be regarded as the same as the electrode 40. Therefore, when multiple superconducting coils 10 are stacked to constitute the superconducting coil device 100, the metal plate 41 also constitutes the electrode 40.
Hereinafter, embodiments of a superconducting coil according to the present invention will be described with reference to the drawings.

[First embodiment]
The superconducting coil according to the first embodiment will be described with reference to FIG. 10, and FIGS.

(composition)
FIG. 10 is a schematic view of the superconducting coil 10 according to the first embodiment, and FIGS. 11(a) and 11(b) are enlarged cross-sectional views of regions Ω3 and Ω4 shown in FIG.

In the superconducting coil 10 according to this embodiment, the inner electrode 40a is connected to the thin-film wire 20 of the innermost turn of the winding section 12, and the detour 19 provided on the winding end surface section 18 extends radially inward and contacts the inner electrode surface 50a perpendicular to the winding axis direction of the inner electrode 40a (FIG. 11(a)).

The outer electrode 40b is connected to the thin-film wire 20 of the outermost turn of the winding section 12, and the detour 19 provided on the winding end surface 18 extends radially outward and contacts the outer electrode surface 50b perpendicular to the winding axis direction of the outer electrode 40b (Figure 11(b)). The detour 19 is effective if it contacts at least a part of the inner electrode surface 50a and the outer electrode surface 50b, but a greater effect is obtained if it contacts the entire surface of the inner electrode surface 50a and the outer electrode surface 50b.

As a method for contacting the detour 19 with the inner electrode surface 50a and the outer electrode surface 50b, direct contact is effective, but contact may also be made via other materials with high conductivity, such as solder or silver paste. Either method is effective because the detour 19 is electrically connected to the inner electrode 40a and the outer electrode 40b without going through the thin-film wire 20.

(Action)
The operation of the superconducting coil 10 according to this embodiment configured as above will be described.
First, consider the case where a current flows out from the winding portion 12 to the outer electrode 40b. In the conventional superconducting coil 10, when the thin-film wire 20 adjacent to the outer electrode 40b undergoes a normal conductive transition, as shown in Fig. 7(b), there is no path for a current to flow from the winding portion 12 to the outer electrode 40b while avoiding the normal conductive portion 15, so the current flows out to the outer electrode 40b through the normal conductive portion 15.

In addition, in FIG. 7(a), the detour 19 can contact the surface parallel to the winding axis direction of the inner electrode 40a, but it only makes contact at a slight step caused by the difference in axial length between the thin-film wire 20 and the inner electrode 40a. Because the contact resistance is large, a sufficient amount of current cannot be detoured, and there is a risk that the current will not be able to flow around the normally conducting portion 15.

In contrast, in the superconducting coil 10 of the first embodiment, as shown in Figures 11(a) and 11(b), the detour 19 electrically connects the thin-film wire 20 to the inner electrode 40a and the outer electrode 40b, so that a path exists through which current flows from the winding portion 12 to the inner electrode 40a or the outer electrode 40b, avoiding the normal conductive portion 15. This allows the current to flow to the inner electrode 40a or the outer electrode 40b, avoiding the normal conductive portion 15.

(effect)
As described above, in the conventional superconducting coil 10 shown in Figures 7(a) and 7(b), when the thin-film wire 20 adjacent to the inner electrode 40a and the outer electrode 40b undergoes a normal conductive transition, the current flows through the normal conductive portion 15 to the inner electrode 40a or the outer electrode 40b, which may cause localized heat generation and burnout.

On the other hand, in the superconducting coil 10 according to the first embodiment, as shown in Figures 11(a) and 11(b), the current can be caused to flow from the thin-film wire 20 to the inner electrode 40a or the outer electrode 40b via the detour 19, avoiding the normal conductive portion 15, thereby preventing localized heat generation in the normal conductive portion 15 and suppressing the occurrence of thermal runaway or quenching of the superconducting coil 10.

Second Embodiment
A superconducting coil according to a second embodiment will be described with reference to Fig. 12, Fig. 13(a) and Fig. 13(b). Note that the same components as those in the above embodiment are given the same reference numerals, and duplicated descriptions will be omitted.

(composition)
In the superconducting coil 10 according to the second embodiment, the lead electrode 42 is connected to the inner electrode 40a, and the detour 19 is also in contact with the lead electrode 42. Similarly, the lead electrode 42 is connected to the outer electrode 40b, and the detour 19 is also in contact with the outer lead electrode 42.

These lead electrodes 42 are fixed and electrically connected to the inner and outer electrodes 40a, 40b by soldering, screwing, or other methods in order to extend the inner and outer electrodes 40a, 40b. The lead electrodes 42 are preferably made of copper, silver, gold, indium, or alloys thereof. The lead electrodes 42 and the inner and outer electrodes 40a, 40b may be made of the same material. The lead electrodes 42 are connected to a power source via lead wires, and become part of the current path when current flows in and out of the superconducting coil 10.

(Action and Effect)
Since there is contact resistance at the connection portion between the detour 19 and the inner and outer electrodes 40a, 40b, when a current flows to the inner and outer electrodes 40a, 40b via the detour 19 while avoiding the normally conductive portion 15, heat may be generated at the contact portion with the detour 19. In the second embodiment, the detour 19 is also electrically connected to the lead electrode 42, so that the cross-sectional area of the path through which the current flowing in the detour 19 flows out to the outside of the superconducting coil 10 is increased, and the contact resistance is reduced.

As a result, heat generation at the connection between the bypass 19 and the inner and outer electrodes 40a, 40b is suppressed, further reducing the risk of thermal runaway or quenching of the superconducting coil 10.

[Third embodiment]
A superconducting coil according to a third embodiment will be described with reference to Figures 14(a) and 14(b). Note that the same components as those in the above-mentioned embodiment are given the same reference numerals, and duplicated descriptions will be omitted.

(composition)
In the superconducting coil 10 according to the third embodiment, the detour 19 is arranged to cover the entire inner and outer electrodes 40 a, 40 b. When the bobbin 14 and the lead electrode 42 of the superconducting coil 10 are connected to the electrode 40, the same effect can be obtained by covering the surfaces other than the connection surfaces.

(Action and Effect)
In this embodiment, the detour 19 is arranged to cover the entire inner and outer electrodes 40a, 40b, thereby increasing the area of the connection between the detour 19 and the inner and outer electrodes 40a, 40b, and thereby reducing the contact resistance of the connection.
Therefore, heat generation at the connection portion between the bypass 19 and the inner and outer electrodes 40a, 40b is suppressed, so that the risk of thermal runaway or quenching of the superconducting coil 10 can be reduced.

[Fourth embodiment]
A superconducting coil according to a fourth embodiment will be described with reference to Fig. 15. Note that the same components as those in the above-mentioned embodiments are given the same reference numerals, and duplicated descriptions will be omitted.

(composition)
15, in the superconducting coil 10 according to the fourth embodiment, the detour 19 extends over the entire circumference at the radial end on the side where the inner and outer electrodes 40a, 40b are provided so as to cover the radial end (the innermost circumference or the outermost circumference) of the winding portion 12. When the superconducting coil 10 includes a reel 14 and inner and outer lead electrodes 42, the same effect can be obtained by covering the surface excluding the connection surfaces with these members. The same effect can also be obtained by covering the reel 14 and the inner and outer lead electrodes 42.

(Action and Effect)
In this embodiment, the detour 19 is arranged around the entire innermost or outermost circumference of the superconducting coil 10, so that the cross-sectional area of the current path when current flows from the thin-film wire 20 to the inner and outer electrodes 40a, 40b via the detour 19 is increased, and the resistance value of the current path can be reduced.
Therefore, a sufficient amount of current flows from the thin-film wire 20 to the bypass 19, so that the risk of thermal runaway or quenching of the superconducting coil 10 can be further reduced.

[Fifth embodiment]
A superconducting coil according to the fifth embodiment will be described with reference to Fig. 16. Note that the same components as those in the above-mentioned embodiments are given the same reference numerals, and duplicated descriptions will be omitted.

In the superconducting coil 10 according to the fifth embodiment, the winding section 12 is wound around a bundle of multiple thin-film wires 20. There is no limit to the number n of thin-film wires 20 bundled together, but they are usually bundled together in the range of n=2 to 5. By using n thin-film wires 20 bundled together, there is an advantage in that the critical current of the thin-film wires 20 can be effectively increased by n times.

On the other hand, since it is necessary to electrically connect the multiple thin-film wires 20 to the inner and outer electrodes 40a, 40b, respectively, if the bypass path 19 does not electrically connect the inner and outer electrodes 40a, 40b to the thin-film wires 20, the following disadvantages arise.

In other words, if the circumferential length of the inner and outer electrodes 40a, 40b is L, the number of thin-film wires 20 to be bundled is n, and the circumferential length connected to the inner and outer electrodes 40a, 40b is evenly distributed among the thin-film wires 20, the circumferential length of the connection between the inner and outer electrodes 40a, 40b and the thin-film wire 20 is L/n, and the circumferential length of the connection between the inner and outer electrodes 40a, 40b and the thin-film wire 20 is smaller than when there is only one thin-film wire 20.

Therefore, compared to when only one thin-film wire 20 is used, the heat generated when the thin-film wire 20 adjacent to the inner and outer electrodes 40a, 40b undergoes a normal conductive transition is greater. Figure 16 shows the positional relationship when an inner electrode 40a with length L1 and two thin-film wires 20a, 20b are used.

(Action and Effect)
In the present embodiment, too, the detour 19 electrically connects the inner electrode 40a and the thin-film wires 20a, 20b, so that when the thin-film wires 20a, 20b adjacent to the inner electrode 40a undergo a normal conductive transition, the current flowing through the thin-film wires 20a, 20b flows to the inner electrode 40a via the detour 19, thereby avoiding the normal conductive portion 15. Thus, the above-mentioned disadvantages can be reduced while the advantages of bundling the thin-film wires 20a, 20b can be obtained.
Therefore, a sufficient amount of current flows from the multiple thin-film wires 20a, 20b to the bypass 19, thereby reducing the risk of thermal runaway or quenching of the superconducting coil 10.

Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the gist of the invention. These embodiments and their variations are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

For example, a so-called pancake-shaped superconducting coil is given as an example of the shape of the winding section in which the bypass path, conductive member, and insulating material are provided. However, applicable winding sections are not limited to pancake-shaped ones. In addition, the invention can also be applied to non-circular coils such as saddle-shaped, elliptical, and three-dimensional coils.

10...superconducting coil, 12...winding section, 14...winding frame, 15...normally conductive portion, 16...insulating plate, 18...winding end surface, 19...detour (conductive member), 20...high-temperature superconducting wire (thin-film wire), 21...stabilizing layer, 22...substrate, 23...orientation layer, 24...intermediate layer, 25...high-temperature superconducting layer, 26...protective layer, 33...insulating member, 35...conductive powder, 36...conductive resin layer, 40...electrode, 40a...inner electrode, 40b...outer electrode, 41...metal plate, 42...lead electrode, 50a...inner electrode surface, 50b...outer electrode surface, 100...superconducting coil device

Claims (8)

A superconducting coil comprising: a winding section formed by winding a tape-shaped high-temperature superconducting wire in which thin-film layers including a high-temperature superconducting layer are stacked; an inner electrode and/or an outer electrode connected to the high-temperature superconducting wire at the innermost and/or outermost periphery of the winding section; and a conductive member provided on an end surface perpendicular to the winding axis direction of the winding section, electrically connecting axial ends of the high-temperature superconducting wire to each other and forming a bypass path,
A superconducting coil characterized in that the conductive member extends from the winding portion to the inner and/or outer circumferential sides in the winding radial direction and is in contact with a surface of the inner electrode and/or outer electrode perpendicular to the winding axis direction. The superconducting coil according to claim 1, characterized in that it has an outlet electrode connected to the inner electrode and/or the outer electrode, and the conductive member is in contact with the outlet electrode. The superconducting coil according to claim 1 or 2, characterized in that the conductive member is arranged to cover the entire inner electrode and/or the outer electrode. The superconducting coil according to claim 1 or 2, characterized in that the conductive member is arranged to cover the entire innermost circumference and/or the entire outermost circumference of the winding portion, including the inner electrode and/or the outer electrode. A superconducting coil according to any one of claims 1 to 4, characterized in that the conductive member is made of conductive resin. A superconducting coil according to any one of claims 1 to 5, characterized in that an insulating plate made of an insulating material is provided on the surface of the conductive member. A superconducting coil according to any one of claims 1 to 6, characterized in that the winding section is formed by bundling and winding a plurality of the high-temperature superconducting wires. A superconducting coil device comprising a plurality of superconducting coils according to any one of claims 1 to 7 stacked in the winding axis direction.

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