JP7222622B2 - Superconducting coil and superconducting coil device - Google Patents

Description

An embodiment of the present invention relates to a superconducting coil in which a superconducting wire is wound in a coil shape, and a superconducting coil device using this superconducting coil.

A superconducting wire has a range of current, temperature, and magnetic field in which the superconducting state can be maintained, that is, so-called critical current, critical temperature, and critical magnetic field. Therefore, even if the electrical resistance is almost zero, the current cannot flow infinitely, and if any critical value is exceeded, a transition phenomenon to the normal conducting state, that is, quench occurs. Joule heating in the normal-conducting transition region due to such quench causes instantaneous thermal runaway of the superconducting coil, and in the worst case, there is a risk of burnout. Therefore, protection technology against quench is essential.

As a conventional technique for quench protection, for example, there is a method of connecting a protection resistor in parallel with a superconducting coil. This method detects the coil voltage and temperature rise generated by the transition to the normal conducting state, and uses this as a trigger to cut off the excitation power supply. After shutting down, the superconducting coil and the protection resistor form a closed circuit, so the Joule heating of the protection resistor placed at room temperature consumes the stored energy in the superconducting coil, and the current flowing through the coil can be attenuated.

Superconducting wires used in such superconducting coils include, for example, Bi ₂ Sr ₂ Ca ₂
There are high-temperature superconducting wires such as Cu ₃ O ₁₀ +x wires and RE1B2C3O7 wires (REBCO wires). A superconducting coil using a high-temperature superconducting wire has a high critical current density even at a high temperature of 20 K to 50 K compared to a conventional low-temperature superconducting wire such as NbTi, so high current density operation at high temperature is possible.

In addition, "RE" of "RE1B2C3O7" is a rare earth element (for example, neodymium (Nd),
gadolinium (Gd), holminium (Ho), samarium (Sm), etc.) and at least one of yttrium elements, "B" is barium (Ba), "C" is copper (Cu),
"O" means oxygen (O).

However, when quenching occurs during high-current-density operation, the expansion of the normal-conducting transition region is slow in the temperature range of 20K to 50K because the specific heat is greater than the operating temperature of magnets using low-temperature superconducting wires. Since the current density operation also increases the heat generation density, the quench protection method of the prior art may cause local thermal runaway and burnout before detection.

Therefore, if the superconducting wires of different turns inside the superconducting coil are short-circuited between the turns, the current flowing in the portion where the normal conduction transition occurs can be detoured to the superconducting wires of different turns. By bypassing the normal-conducting portion of the current, it is possible to suppress local heat generation and thermal runaway in the normal-conducting transition region. Specifically, by providing a detour electrically connected to the superconducting wire on the side surface of the winding member along the coil radial direction of the superconducting coil, the superconducting wires of different turns are short-circuited via the detour. I have the technology.

JP 2017-103352 A WO2017/061563

However, when the heat transfer plate used for conduction cooling of the superconducting coil is provided on the side of the superconducting coil, the detour on the side of the coil and the heat transfer plate are electrically connected, and the refrigerator connected to the heat transfer plate breaks down. I had a problem. On the other hand, even if an insulating material is inserted between the detour and the heat transfer plate, an excessive voltage is applied to the detour when the load factor of the superconducting coil increases, causing dielectric breakdown and the detour and the heat transfer plate to conduct. I was afraid that I would lose it.

The risk of dielectric breakdown can be reduced by increasing the thickness of the insulating material between the detour and the heat transfer plate, but the thicker the insulating material, the lower the current density of the superconducting coil.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a superconducting coil and a superconducting coil device that can suppress the occurrence of thermal runaway or quenching and that can be conductively cooled using a heat transfer plate. and

The superconducting coil according to the present embodiment includes a winding member having a pair of winding side portions along the winding radial direction formed by laminating the superconducting wire material in the winding radial direction by winding, A detour is provided on one of the winding side portions of the winding member to electrically connect the superconducting wires of different turns in a radial direction , and the detour of the winding member is provided. A superconducting coil in which a heat transfer plate electrically insulated from the winding member is provided on the other winding side portion
In the coil, the winding side portions of the side provided with the heat transfer plate or the side provided with the detour
are laminated along the winding central axis so that the winding side portions of the winding face each other .

A superconducting coil device according to the present embodiment is characterized by including the superconducting coil described above.

According to the present invention, it is possible to provide a superconducting coil and a superconducting coil device capable of suppressing the occurrence of thermal runaway or quenching and conducting conduction cooling using a heat transfer plate.

FIG. 2 is a partially cutaway perspective view of a general high-temperature superconducting wire; 1 is a perspective view schematically showing an example of a superconducting coil made of a winding member wound with a high-temperature superconducting wire; FIG. FIG. 3 is a cross-sectional view showing a coil radial cross section taken along line II-II of FIG. 2 showing the superconducting coil; FIG. 4 is a coil radial direction sectional view showing an enlarged Ω portion of FIG. 3 ; Schematic cross-sectional view of a conductive resin. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a coil radial cross-sectional view showing an enlarged main part of a superconducting coil according to a first embodiment of the present invention; FIG. 5 is a coil radial direction cross-sectional view showing an enlarged main part of a superconducting coil according to a second embodiment of the present invention. FIG. 10 is a coil radial direction cross-sectional view showing an enlarged main part of a superconducting coil according to another example of the second embodiment of the present invention. FIG. 10 is a coil radial direction cross-sectional view showing an enlarged main part of a superconducting coil according to another example of the second embodiment of the present invention.

FIG. 3 is a coil radial direction cross-sectional view showing an enlarged main part of a superconducting coil according to a third embodiment of the present invention.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

The superconducting coils according to the embodiments are effective for both high-temperature superconducting wires and low-temperature superconducting wires. However, in the following, the case of using a high-temperature superconducting wire that exhibits a particularly high effect will be described as an example.

(Example 1)
First, the configuration of the high-temperature superconducting wire 20 will be described using the configuration perspective view of the high-temperature superconducting wire 20 in FIG. As shown in FIG. 1, the high-temperature superconducting wire 20 constitutes a tape-shaped thin-film wire 20 in which thin-film layers are laminated. This thin film wire 20 is made of, for example, a rare metal oxide (R
E oxide) (hereinafter referred to as "high-temperature superconducting layer 25"), such as a REBCO wire.

The thin film wire 20 includes a substrate 22 made of a high-strength metal material such as nickel-based alloy, stainless steel, or copper, an intermediate layer 24 formed on the substrate 22, and the intermediate layer 24 oriented on the surface of the substrate 22. a high-temperature superconducting layer 25 made of oxide formed on the intermediate layer 24; a protective layer 26 made of silver, gold, platinum, or the like;
and a stabilization layer 21, which is a well-conducting metal such as copper or aluminum.

Intermediate layer 24 prevents thermal distortion caused by thermal contraction of substrate 22 and superconducting layer 25 . The protective layer 26 protects the superconducting layer 25 by preventing oxygen contained in the high-temperature superconducting layer 25 from diffusing from the superconducting layer 25 . In addition, the stabilization layer 21 serves as a detour path for excessive current flow to the superconducting layer 25 to prevent thermal runaway. However, the kind and number of each layer constituting the thin film wire 20 are not limited to this, and may be as large or small as necessary.

FIG. 3 shows the configuration of the superconducting coil 10, and is a cross-sectional view showing a coil radial cross section taken along line II--II in FIG. Moreover, FIG. 4 is sectional drawing which expands and shows the (omega) part of FIG.

The superconducting coil 10 shown in FIG. 3 is formed by winding the thin-film wire 20 around the winding frame 14 to form the pancake-shaped winding member 12 having a space penetrating the center C in the winding axial direction. can get. A coil formed in a pancake shape by concentrically winding the thin film wire 20 is called a pancake coil.

The winding member 12 has a pair of winding side portions 18 formed by laminating the thin film wire 20 by winding. In addition, in the superconducting coil 10, the thin film wire 2 of another adjacent turn
The gap between 0's is simply called between coil turns. As shown in FIG. 4, an insulating member 33 is inserted between the thin-film wires 20 for insulation between adjacent turns. As the insulating member 33, for example, an insulating tape made of polyimide or the like is preferably used. The tape-shaped insulating member 33 is inserted between the coil turns by being co-wound with the thin film wire 20 .

The superconducting coil 10 may be impregnated with a sticky insulating material such as epoxy resin. By being impregnated with adhesive resin, adjacent thin film wire 20 and insulating member 33 in superconducting coil 10 are fixed, and thermal conductivity and mechanical strength of superconducting coil 10 are improved. An insulating material having adhesiveness such as epoxy resin can also work as the insulating member 33 by being inserted between the turns. Insulation between coil turns is preferred.

In addition, the superconducting coil 10 has, as shown in FIG.
A detour 19 is provided to electrically connect the thin-film wires 20 at different positions within the superconducting coil 10 . The material of the detour 19 is larger than the resistance of the superconducting coil 10 during normal operation,
In addition, a material having a resistance smaller than the resistance of the superconducting coil 10 at the time of transition to normal conduction is selected.

The material of the detour 19 is, for example, copper, stainless steel, aluminum or indium or other normally conducting metals, semiconductors, conductive plastics, ceramics materials, conductive resins, superconducting materials, or the like. A carbon material such as graphite, carbon fiber, or carbon fiber composite material can also be suitably used as the detour 19 . These materials are made into plate materials, foils, or the like, and are electrically connected to the winding member 12 by crimping, soldering, or the like.

Alternatively, the detour 19 may be formed by plating or coating one winding side portion 18 .
In particular, when the detour 19 is formed by plating, the detour 19 can be made thin and free deformation of the superconducting coil 10 is not hindered. Alternatively, the detour 19 may be formed by applying a conductive resin 36 as shown in FIG.

For the conductive resin 36, for example, a resin 37 having no conductivity mixed with conductive powder 35 can be used. In this case, the conductive powder 35 mixed with the conductive resin 36
It is possible to easily adjust the volume resistivity of the conductive resin 36 by changing the ratio and type of . As the conductive powder 35, for example, carbon-based powder such as carbon black, carbon fiber, or graphite is used. Also, the conductive powder 35 may be metal-based powder such as fine metal particles, metal oxides, metal fibers, or whiskers. moreover,
The conductive powder 35 may be formed by coating fine particles or synthetic fibers with a metal. Alternatively, the detour 19 may be formed by applying a conductive resin layer 36 having a different composition to each position of the winding side portion 18 .

Here, the effect of suppressing the occurrence of thermal runaway or the like by providing the detour 19 will be described. As the thin film wire 20 approaches the critical current, which is the limit of the applied current, the external magnetic field gradually penetrates, and the part where the superconducting state is locally destroyed transitions to normal conduction. The flux flow resistance associated with this local transition to normal conduction generates heat due to Joule loss, so if it increases due to a rise in coil temperature, etc., it induces thermal runaway or quench (hereinafter collectively referred to as "thermal runaway, etc."). .

By providing the detour 19, when a local flux flow resistance due to a normal-conducting transition occurs in a part of the thin film wire 20, a part Ia of the conducting current I flowing in the coil circumferential direction is transferred to the detour 19. It is possible to make a detour in the coil radial direction to the thin film wire 20 of another turn adjacent via. Here, the current flowing in the circumferential direction of the coil decreases from I to I-Ia. At this time, assuming that the resistance of the detour 19 is Ra and the flux flow resistance is R, the current Ia detoured in the radial direction of the coil is proportional to R/(R+Ra). As the flux flow resistance increases, a larger amount of current flows in the radial direction of the coil.

Therefore, it is possible to prevent a large amount of energizing current I from flowing through the normally conducting portion that has locally transitioned to the normal conducting state, and it is possible to suppress the occurrence of thermal runaway or the like.

Note that if the coil turns are electrically connected via the detour 19, the induced voltage is reduced not only when the flux flow resistance is generated, but also when the superconducting coil 10 is excited from the non-energized state to the rated current value. A part I′ of the current I supplied from the power source is detoured to the thin film wire 20 of another turn through the detour 19 in the radial direction of the coil. Since no induced voltage is generated after completion of excitation, the current I' flowing through the detour 19 gradually flows in the circumferential direction of the coil, and it takes time to reach the designed value of the magnetic field. Therefore, the lower the resistance between the coil turns, the more current is bypassed during excitation, unnecessarily lengthening the excitation time. The resistance Ra of the detour 19 is small enough to allow a sufficient amount of current to commutate to the detour when flux flow resistance occurs, and is unnecessary when the superconducting coil 10 is excited from a non-energized state to a rated current value. It is preferable to set the resistance so as not to increase the excitation time.

FIG. 6 shows a coil radial cross section of the superconducting coil 10 according to the first embodiment. In the superconducting coil 10 according to the first embodiment, the heat transfer plate 17 is
Of the pair of winding side portions 18, the detour 19 is provided in the other winding side portion 18 where the detour 19 is not provided, and the winding member 12 and the heat transfer plate 17 are electrically insulated. As a material for the heat transfer plate 17, a substance having a high thermal conductivity is preferable, and a metal such as aluminum or copper is preferably used. These materials are made into plates or foils and adhered to the other winding side portion 18 of the superconducting coil 10 .

The heat transfer plate 17 is thermally connected to a refrigerator (not shown) directly or indirectly via another heat transfer member, and has the effect of removing heat generated by the superconducting coil 10 . As a method for electrically insulating the winding member 12 and the heat transfer plate 17, the heat transfer plate 17 can be adhered to the winding member 12 using an electrically insulating adhesive such as epoxy resin. Of course, the winding member 12 may be impregnated with an insulating impregnating material such as epoxy resin. An electrical insulating plate 16 may be inserted between the winding member 12 and the heat transfer plate 17, and the insulating plate 16 is preferably made of fiber-reinforced plastic or the like. When inserting the insulating plate 16 between the winding member 12 and the heat transfer plate 17, the winding member 1 is bonded by bonding the winding member 12, the insulating plate 16, and the heat transfer plate 17 together with an epoxy resin.
2 and the heat transfer plate 17 can be thermally connected, and electrical insulation can be improved.

As described above, 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 transition to normal conduction. For example, when the flux flow resistance over the entire length of the superconducting coil is Rn when the thin film wire 20 transitions to normal conduction over the entire length, and the resistance of the detour 19 is Ra=R/10, then R/(R+Ra)=0.9. Approximately 90% of the applied current is detoured in the radial direction of the coil. When an excessive voltage is generated in the detour 19 in this state, if the heat transfer plate 17 is provided on the winding part side surface 18 on the same side as the detour 19, the heat transfer plate 17 is temporarily insulated. Even so, there is a risk that the current (90% of the energized current) detoured in the radial direction of the coil due to dielectric breakdown will flow through the heat transfer plate 17 .

In the superconducting coil 10 according to the first embodiment, the heat transfer plate 17 is different from the detour 19 in the winding member 1 .
2, even if an excessive voltage is generated in the detour 19 in this state, the current flowing through the detour 19 may directly flow into the heat transfer plate 17. do not have. Moreover, even if a dielectric breakdown occurs between the winding member 12 and the heat transfer plate 17, the current flowing through the heat transfer plate 17 is about 10% of the current, and the heat transfer plate 17 is the same as the detour 19. This can be greatly reduced compared to the case where it is provided on the side winding portion side surface 18 .

Therefore, the current flowing through the heat transfer plate 17 when dielectric breakdown occurs can be reduced more than in the conventional example, so the failure probability of equipment such as a refrigerator connected to the heat transfer plate 17 can be reduced.

(Example 2)
Next, Example 2 will be described with reference to FIGS. 7, 8, and 9. FIG. In addition, the same code|symbol is attached|subjected to the structure same as Example 1, and the overlapping description is abbreviate|omitted.

As shown in FIG. 7, the superconducting coil 40 according to the second embodiment is the superconducting coil 10 shown in FIG. are laminated along the winding central axis so that the winding side portions 18 face each other. In this case, the two adjacent heat transfer plates 17 may be integrated to replace one heat transfer plate 17 .

Alternatively, two detours 19 facing each other adjacently may be integrated and replaced with one detour 19 . In this case, since the adjacent superconducting coils 10 are electrically connected to each other, the current flowing through the superconducting coils 10 can be commutated to the adjacent superconducting coils 10 through the detour 19 . However, when the superconducting coils 10 are electrically connected, the excitation time becomes longer as in the case where the turns of the superconducting coil 10 are electrically connected. For this reason, in order not to increase the excitation time, as another embodiment shown in FIG. good too.

A plate-shaped fiber-reinforced plastic or the like can be used as the detour insulating plate 42 .
Alternatively, the detour insulating member 42 can be formed by applying an epoxy resin or the like.

As another embodiment, as shown in FIG. 9, a thin layer of epoxy resin, fiber reinforced plastic, or the like is formed in the gap where the detour 19 of the superconducting coil 43 faces in view of the heat transfer performance in the direction of the winding axis. An insulating heat equalizing plate 13 having a surface facing the detour 19 insulated with an insulating material may be provided. As the material of the insulating and heat equalizing plate 13, similarly to the heat transfer plate 17, a metal having a high thermal conductivity such as aluminum or copper is preferably used. The insulating and heat equalizing plate 13 is thicker than the detour 19 in order to facilitate heat transfer. Therefore, the insulating soaking plate 13 is not electrically connected to equipment outside the superconducting coils such as a refrigerator by an insulating material, and electrically insulates the adjacent superconducting coils 10 and The effect of keeping the temperature in 10 uniform can be obtained.

In the laminated superconducting coils 40, 41, and 43 according to the second embodiment, the heat transfer plate 1
7 is insulated from the winding side portion 18 on the opposite side across the winding member 12 from the detour 19, so even if an excessive voltage is generated in the detour 19 in this state, the detour There is no danger that the current flowing through 19 will directly flow into the heat transfer plate 17 . In addition, if the detour 19 that is adjacent and faces
Even if the insulating plate 16 provided between them or the insulator for insulating the insulating and heat equalizing plate 13 from the detour 19 causes a dielectric breakdown, the heat transfer plate 17 is detoured across the winding member 12. Since it is positioned on the winding side portion 18 opposite to the path 19 , there is no danger that the current flowing through the detour 19 will flow into the heat transfer plate 17 .

Therefore, as in the case of the first embodiment, when dielectric breakdown occurs, the current flowing through the heat transfer plate 17 can be reduced more than in the conventional example. Probability can be reduced.

(Example 3)
Next, Example 3 will be described with reference to FIG. In addition, the same code|symbol is attached|subjected to the structure same as Example 1 and Example 2, and the overlapping description is abbreviate|omitted.

In the laminated superconducting coil 50 according to the third embodiment, as shown in FIG. 10 corresponding to FIG. The adhesive force between the mold material 34 and the adjacent thin film wire 20 is weakened. Any material may be used as the release material 34 as long as the separation property between the release material 34 and the adjacent thin film wire 20 is good. For example, the insulating material member 33 can be used by adhering or applying fluorine resin, paraffin, grease, silicon oil, or the like.

When the superconducting coil 10 is used, the superconducting coil 10 is subjected to thermal stress in the coil radial direction generated during cooling to the operating temperature and separation stress such as electromagnetic stress generated by excitation. In particular, when the superconducting coil 10 is impregnated with a resin, the thermal stress caused by the difference between the thermal contraction rate of the thin film wire 20 and the thermal contraction rate of the resin used for impregnating the superconducting coil 10 causes the thin film wire 20 to
may be subjected to peel stress exceeding the allowable value.

When the thin film wire 20 is subjected to a peeling stress exceeding the allowable value, the high-temperature superconducting layer 25 inside the thin film wire 20 is mechanically destroyed, resulting in deterioration (degradation) of superconducting properties. When the superconducting property deteriorates, the critical current value is significantly lowered, so flux flow resistance is generated even at the energized current value that should not normally occur. The current flowing in the circumferential direction of the coil is reduced. Since the magnetic field generated by the superconducting coil 10 is proportional to the current flowing in the circumferential direction of the coil, the designed magnetic field cannot be generated by the superconducting coil 10 .

Therefore, when the thin-film wire 20 is used for the superconducting coil 10, it is necessary to devise measures so that the peel stress does not exceed the allowable value. Here, the thermal stress in the radial direction of the coil that occurs during cooling depends on the ratio of the inner diameter to the outer diameter of the coil. In the superconducting coil 50 (10) according to the ninth embodiment, the winding member 12 is divided into a plurality of pieces by the release member 34, so that the ratio of the inner diameter to the outer diameter of each divided winding member is set small. It is possible to keep the peel stress below the allowable value.

According to the superconducting coil 50 according to the third embodiment, by inserting the release material 34 between the coil turns described in the first embodiment, the delamination stress applied to the thin film wire 20 can be reduced to an allowable value or less. Therefore, deterioration of superconducting properties can be prevented, so that a designed magnetic field can be generated during rated operation, and thermal runaway can be avoided when flux flow resistance occurs due to a local normal-conducting transition. .

While several embodiments of the invention have been described, these embodiments have been presented by way of example 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. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

For example, in Examples 1 to 3, a so-called pancake-shaped superconducting coil was exemplified as the shape of the winding member provided with the detour, the conductive member, and the insulating material. However, applicable winding members are not limited to pancake-shaped ones. It can also be applied to non-circular coils such as racetrack, saddle, and elliptical coils.

Further, by incorporating the superconducting coil into a device such as a heavy particle therapy device that is required as a magnetic field generating source, it is possible to obtain a superconducting coil device that generates a desired magnetic field.

Furthermore, if necessary, it is possible to combine and stack a normal superconducting coil, and adopt and arrange the superconducting coil of the present invention only in a portion where thermal runaway or quenching is highly likely to occur.

DESCRIPTION OF SYMBOLS 10... Superconducting coil, 12... Winding member, 13... Insulating soaking plate, 14... Winding frame, 16... Insulating plate (
insulating member), 17 heat transfer plate, 18 winding side portion, 19 detour, 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 34 Release material 35 Conductive conductive powder 36 conductive resin 37 non-conductive resin 40, 41, 43 superconducting coil 42 detour insulating plate (detour insulating member) 50 superconducting coil.

Claims (11)

A winding member having a pair of winding side faces along the winding radial direction formed by laminating a superconducting wire material in the winding radial direction by winding, and one winding of the winding member A detour is provided on the wire side surface portion to electrically connect the superconducting wires of different turns in the radial direction , and the other winding side portion of the winding member is not provided with the detour path. is a superconducting coil provided with a heat transfer plate electrically insulated from the winding member,
The winding side portions provided with the heat transfer plate or the winding provided with the detour
A superconducting coil characterized by being laminated along a winding central axis so that side portions face each other . 2. A superconducting coil according to claim 1, wherein said heat transfer plate is provided on said winding member via an insulating member that electrically insulates said heat transfer plate. 2. A superconducting coil according to claim 1 , wherein said adjacent heat transfer plates or said detours of said laminated superconducting coils are integral members. 2. The superconducting structure according to claim 1 , wherein the detours of the stacked superconducting coils are provided with a detour insulation member for electrically insulating the detours on the facing surfaces of the adjacently opposed detours. coil. In the laminated superconducting coils, adjacently facing detours are provided with an insulating heat equalizing plate on the facing surface to electrically insulate the detours and keep the temperature in the adjacent superconducting coils uniform. 2. The superconducting coil according to claim 1 , wherein the superconducting coil is 6. The detour according to any one of claims 1 to 5 , wherein the detour is made of a conductive resin.
A superconducting coil according to any one of claims 1 to 3. 3. A superconducting coil according to claim 2, wherein said insulating member is made of epoxy resin or fiber reinforced plastic. 5. A superconducting coil according to claim 4 , wherein said detour insulating member is made of epoxy resin or fiber reinforced plastic. 9. The superconducting coil according to any one of claims 1 to 8 , wherein a release material is inserted between the turns of the winding member to weaken the adhesive force between the adjacent superconducting wires. A superconducting coil device comprising the superconducting coil according to any one of claims 1 to 9 . A superconducting coil device comprising a plurality of superconducting coils, including the superconducting coil according to any one of claims 1 to 9, laminated along the winding center.

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