JPH09129938A - Superconduction apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement means that even if a superconductor coil is quenched, without opening a cryogenic vessel to the air, the pressure rise can be suppressed to contribute to improvement of the safety and expansion of the application. SOLUTION: A superconduction apparatus has a superconductor coil 7 and cryogenic coolant liq. 8 in a cryogenic vessel 1 wherein a first pressure rise suppressing space 10 formed above the surface of the cryogenic coolant liq. 8 and second volume-variable pressure rise suppressing space 11 formed in a top-closed structure 9 with its opening down in the liq. 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device, and more particularly to a superconducting device capable of suppressing a pressure increase in a cryogenic container which occurs when a superconducting coil is quenched.

[0002]

As is well known, the main part of a superconducting device is
A superconducting coil and a cryogenic refrigerant liquid represented by liquid helium are contained in a cryogenic container. In general, it is not possible to eliminate the heat penetration into the cryogenic container. Therefore, the cryogenic refrigerant liquid contained in the cryogenic container is gradually evaporated. Therefore, normally, the evaporative gas generated in the cryogenic container is reliquefied using a refrigerator to keep the liquid surface at a constant level.

By the way, in such a superconducting device, when a part of the coil is changed from the superconducting state to the normal conducting state while the superconducting coil is energized, a resistance is generated at this transition portion to generate heat. Due to this heat generation, the adjacent parts also change to the normal conducting state, this process occurs one after another, and finally the entire coil becomes the normal conducting state. This phenomenon is called quench.

A large amount of heat is generated when a quench occurs.
Therefore, when quench occurs, the liquid helium that cools the superconducting coil is evaporated and a large amount of helium gas is generated. It is usually difficult to quickly reliquefy this helium gas in a refrigerator. When liquid helium evaporates to helium gas, the volume becomes very large and the pressure in the cryogenic container rises. Therefore, normally, when the pressure in the cryogenic container rises to a predetermined value, a safety valve is opened to release a part of the helium gas into the atmosphere.

However, in the method of releasing a large amount of helium gas into the atmosphere when the quench occurs, the following problems newly occur. That is, there is a risk of causing oxygen deficiency in the surrounding area when ventilation is not sufficient at the time of release. Further, it is necessary to add the reduced liquid helium content into the cryogenic container, but this addition requires some equipment and skill, and it is difficult to finish in a short time.

In particular, recently, an attempt has been made to construct a fault current limiter of a power system using a superconducting coil of non-induction winding by utilizing the quench phenomenon of the superconducting coil, but it takes a long time to add liquid helium. In short, it becomes difficult to secure the stability of the power system. In other words, this type of fault current limiter is configured by using a superconducting coil of non-induction winding, and normally a load current is applied to the superconducting coil of non-induction winding, and the short-circuit accident or the ground fault causes the superconducting coil. When the flowing current exceeds a critical value, the superconducting coil is quenched, and the resistance of the superconducting coil is instantly generated to limit the current. After that, the circuit breaker provided on the power supply side is opened. In this case, when the circuit breaker opens, the insulation at the accident location may be restored, so the circuit breaker is usually re-closed within a fixed time. The time until re-input is desired to be within 1 minute in the case of a current limiting device provided between systems. It is very difficult to add the reduced liquid helium content within such a short time. This is not limited to current limiting devices, but can also be applied to superconducting transformers. It can also be applied to the case where liquid nitrogen is used as the cryogenic refrigerant liquid.

Therefore, in order to solve such a problem, it is conceivable to provide a large-scale cryogenic refrigerant liquid supply source and a refrigerator having a large capacity, but if such a means is adopted, an increase in equipment cost is avoided. You will not get it.

[0008]

As described above, when the pressure in the cryogenic container increases due to evaporation of the cryogenic refrigerant liquid during quenching of the superconducting coil, the conventional cryogenic container is opened to the atmosphere. The superconducting device not only has a problem of causing oxygen deficiency in the surrounding area when it is opened, but it is difficult to pour the reduced amount of cryogenic refrigerant liquid into the cryogenic container in a short time. When installed, there was a problem that affected the stability of the system.

Therefore, the present invention provides a superconducting device capable of suppressing a pressure increase without opening the cryogenic container to the atmosphere even when the superconducting coil is quenched, and thus contributing to improvement of safety and expansion of applicability. It is intended to be provided.

[0010]

In order to achieve the above object, the present invention provides a superconducting device containing a superconducting coil and a cryogenic refrigerant liquid in a cryogenic container, wherein the cryogenic container comprises: A pressure rise suppression space is provided which communicates with the region where the cryogenic refrigerant liquid is stored.

The pressure rise suppression space is a first pressure rise suppression space formed by a space above the liquid surface of the cryogenic refrigerant liquid, and a bottomed bottom whose opening is located in the cryogenic refrigerant liquid. It may be constituted by a second pressure rise suppressing space having a variable volume formed by the internal space of the structure.

In order to achieve the above object, the present invention provides a superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein a space above the liquid surface of the cryogenic refrigerant liquid is provided. A buffer tank is provided to communicate therewith to form a pressure rise suppression space.

In order to achieve the above object, the present invention provides a superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein at least the superconducting material is contained in the cryogenic refrigerant liquid. A stirrer for stirring the cryogenic refrigerant liquid when the coil is quenched is provided.

The stirring means is provided at at least one of an upper position and a lower position with the superconducting coil as a boundary, and when the superconducting coil is quenched, the cryogenic refrigerant liquid is forced along the surface of the superconducting coil. It may be constituted by an inclined guide plate for circulating the superconducting coil, and is provided below the superconducting coil to force the cryogenic refrigerant liquid along the surface of the superconducting coil at least when the superconducting coil is quenched. It may be constituted by a screw device for circulation. Further, the stirring means has a variable volume stirring space formed by the internal space of the bottomed structure arranged with the opening downward in the cryogenic refrigerant liquid, and at least the volume of the stirring space at the time of quenching the superconducting coil. It may be configured by a variable volume device that is variable and agitates the cryogenic refrigerant liquid.

In order to achieve the above object, the present invention is a superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein the superconducting coil is formed in a multi-layer structure. .

In order to achieve the above object, the present invention is a superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein a good heat conducting member is contained in the cryogenic refrigerant liquid. Are arranged.

In order to achieve the above object, the present invention is a superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, and a heat storage material is placed in the cryogenic refrigerant liquid. doing.

The superconducting device according to the present invention described above is constructed based on the following knowledge. That is, FIG.
As shown in, a case will be described in which a superconducting coil B and liquid helium C that is a cryogenic refrigerant liquid that cools the superconducting coil B are housed in a closed cryogenic container A.

When the superconducting coil B is quenched, heat is generated in the superconducting coil B as described above, and this heat is consumed by evaporating the liquid helium C. The consumption of this heat energy raises the pressure in the cryogenic container A.

In this case, according to experiments and analysis by the inventors, the propagation of pressure in the liquid helium C is very fast on the order of milliseconds, but the propagation of heat in the liquid helium C is very fast on the order of 100 seconds. Turns out to be late. Therefore, in FIG.
Only the liquid helium located in the region indicated by the chain double-dashed line, that is, the peripheral region D of the superconducting coil B (hereinafter referred to as effective liquid helium) is used for heat absorption, and the liquid located in the other regions Helium (hereinafter referred to as ineffective liquid helium) and helium gas floating on the liquid surface are adiabatically compressed. Reactive liquid helium that is adiabatically compressed absorbs little energy, and most of the energy is absorbed by effective liquid helium. Therefore, the pressure increase in the closed cryogenic container A depends on the amount of the effective liquid helium described above.

FIG. 3 shows a calculation example in which the relationship between the input energy and the pressure rise is obtained using the amount X of effective liquid helium as a parameter (note that X = 0.3 is also a measurement example). On the other hand, FIG. 4 shows a calculation example in which the amount X of effective liquid helium is kept constant and the relationship between the input energy and the pressure rise is obtained using the volume of the helium gas space as a parameter.

From these figures, it can be understood that the following structure is required to suppress the pressure increase in the closed cryogenic container A when the superconducting coil B is quenched. (1) Replace the ineffective liquid helium with gas helium to increase the gas space ratio. The ratio of the gas space is increased by connecting with the external gas space.

(2) When quenching, liquid helium is stirred to increase the amount of effective liquid helium. A good heat conducting member is arranged in liquid helium to increase the amount of effective liquid helium. The superconducting coil is formed in a multi-layer structure to increase the amount of effective liquid helium.

(3) A heat storage material having a large heat capacity is arranged in liquid helium to absorb the input heat energy. These methods are not limited to the case where the cryogenic refrigerant liquid is liquid helium, but can be applied to the case where other cryogenic refrigerant liquids such as liquid nitrogen are used.

The above-mentioned superconducting device according to the present invention is (1)
One of the methods from ~ (3) is adopted. Therefore, even when the superconducting coil is quenched, the pressure increase can be suppressed without opening the cryogenic container to the atmosphere.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic diagram of a superconducting device according to an embodiment of the present invention. In the figure,
Reference numeral 1 indicates a cryogenic container. The cryogenic container 1 includes an outer tank 2 made of a non-magnetic material, an inner tank 3 made of a non-magnetic material housed in the outer tank 2, and a space between the inner tank 3 and the outer tank 2. The vacuum heat insulating layer 4 is formed.

A liquid injection pipe 5 is connected to the upper wall of the inner tank 3 so as to communicate with the inner tank, and the upper end side of the liquid injection pipe 5 is the outer tank 2.
It penetrates airtightly through the upper wall and is guided to the outside. And
An open end located outside the liquid injection pipe 5 is closed by a safety valve 6. The operating pressure of the safety valve 6 is set to a value that is about the same as or slightly higher than that of the conventional superconducting device.

In the inner tank 3, a superconducting coil 7 is arranged, and liquid helium 8 which is a cryogenic refrigerant liquid is accommodated to the level where the superconducting coil 7 is submerged. Further, in the region including the axial center portion of the superconducting coil 7 in the inner tank 3, a bottomed structure 9 formed in a cup shape with a non-magnetic material has an opening located below, and most of it has liquid helium 8 It is arranged to be inserted inside.

That is, in this example, the space 10 existing on the liquid surface of the liquid helium 8 is used as the first pressure rise suppressing space, and the space 1 with variable volume formed inside the bottomed structure 9 is used.
1 is the second pressure increase suppression space. As can be seen from this structure, the space 11 is formed by replacing the ineffective liquid helium.

A final stage heat exchanger 13 of a GMJT refrigerator 12 for reliquefying the helium gas floating in this space is arranged in the space 10 in the inner tank 3. GMJT
The refrigerator 12 is a combination of a Gifford McMahon refrigerator and a Jules Thomson refrigerator.

In this GMJT refrigerator 12, the helium gas discharged from the compressor 14 provided outside the cryogenic container 1 is arranged in the vacuum heat insulating layer 4 in the first stage heat exchanger 1
5 through the primary side of the GM refrigerator 16 and then further cooled by the first stage cooling stage 17 of the GM refrigerator 16 and then passed through the primary side of the second stage heat exchanger 18 and then the second stage of the GM refrigerator 16. It is further cooled in the cooling stage 19, then passed through the primary side of the third-stage heat exchanger 20 and then adiabatically expanded by the JT valve 21 and led to the final-stage heat exchanger 13. Then, the helium gas discharged from the final stage heat exchanger 13 is supplied to the secondary side of the third stage heat exchanger 20, the secondary side of the second stage heat exchanger 19, and the secondary side of the first stage heat exchanger 15. They are sequentially passed and guided to the suction port of the compressor 14. The GM refrigerator 16 is configured in the same manner as a known one using a cold storage material, and the first cooling stage 17 has 40
The second cooling stage 19 is held at about 10K.

In FIG. 1, reference numeral 22 denotes a heat shield plate disposed in the vacuum heat insulating layer 4, and the heat shield plate 22 is G
It is thermally connected to the first cooling stage 17 of the M refrigerator 16. Further, in FIG. 1, a power lead for energizing the superconducting coil 7, a means for detecting that the superconducting coil 7 is quenched, a means for interrupting the power supply to the superconducting coil 7 at the time of quenching, etc. are omitted.

With such a structure, in the steady operation state, the superconducting coil 7 is cooled by the cooling action of the liquid helium 8.
Holds the superconducting state. Further, the liquid level of the liquid helium 8 is kept constant by the refrigerating action of the GMJT refrigerator 12.

In such a state, the superconducting coil 7
When a large amount of heat is generated, a large amount of heat is generated, and this heat causes the effective liquid helium of the liquid helium 8 to evaporate and a large amount of helium gas is generated. It is difficult to quickly reliquefy the generated helium gas in the GMJT refrigerator 12. Therefore, the pressure in the inner tank 3 of the cryogenic container 1 tends to rise.

However, in the case of this example, the function of suppressing the pressure rise by the space 10 existing on the liquid surface of the liquid helium 8 and the inside of the bottomed structure 9 are formed so as to replace the ineffective liquid helium. The function of suppressing the pressure increase by the space 11 having a variable volume effectively acts, and the pressure increase is suppressed to a relatively small value that is equal to or lower than the operating pressure of the safety valve 6.

That is, in this example, since the ratio of the gas space to the volume of the inner tank 3 is increased, it is possible to suppress the pressure increase during the quench. The helium gas generated by evaporation is gradually reliquefied by the GMJT refrigerator 12. Further, the superconducting coil 7 is also gradually cooled and returns to the superconducting state again. Therefore, even if the superconducting coil 7 is quenched, the superconducting coil 7 can be returned to the superconducting state again in a short time without opening the cryogenic container 1 to the atmosphere.

5 to 15 show a schematic structure of a main part of a superconducting device according to another embodiment of the present invention. In these figures, the same parts as those in FIG. 1 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

In the superconducting device shown in FIG. 5, a cup-shaped bottomed structure 9a made of a non-magnetic material is located in the region including the axial center of the superconducting coil 7 with its opening below, and all of them are A variable volume space 11 is formed inside the bottomed structure 9a which is arranged so as to be inserted into the liquid helium 8.
a is the second pressure increase suppression space. Also in this example, the space 11a is replaced with ineffective liquid helium.

In the superconducting device shown in FIG. 6, the bottomed structures 9b and 9c configured to form an annular container along the inner peripheral surface of the inner tank 3 are opened in the liquid helium 8. Are arranged in a two-stage configuration so that they can be inserted into the
11c is the second pressure increase suppression space. Also in this example, the spaces 11b and 11c are replaced with ineffective liquid helium.

In the example shown in FIGS. 5 and 6, the amount of ineffective liquid helium is reduced to increase the ratio of the gas space. Therefore, similarly to the example shown in FIG. 1, even when the superconducting coil 7 is quenched, it is possible to suppress an increase in internal pressure without opening the inner tank 3 to the atmosphere.

In the superconducting device shown in FIG. 7, the first pressure rise suppressing space 10 formed on the liquid surface of the liquid helium 8 is connected to the buffer tank 30 via the pipe 29 to increase the gas space ratio. There is.

Even if such a structure is adopted, the same effect as that of the example shown in FIG. 1 can be obtained. In the superconducting device shown in FIG. 8, an inner tank 31 smaller than the inner tank 3 is provided in the inner tank 3, and the superconducting coil 7 and the liquid helium 8 are accommodated in the inner tank 31 to reduce the ineffective liquid helium. At the same time, the ratio of gas space is increased.

In the superconducting device shown in FIG. 9, the inner tank 3 is divided into two horizontally by a partition wall 32, and the superconducting coil 7 and the liquid helium 8 are accommodated in one of the divided regions, so that the ineffective liquid helium is contained. And increase the ratio of gas space.

Even if the configuration shown in FIGS. 8 and 9 is adopted,
The same effect as the example shown in FIG. 1 can be obtained. FIG.
In the superconducting device shown in FIG. 2, the funnel-shaped inclined guide plates 33a, 33a,
33b are arranged with their respective tops upward, and the amount of effective liquid helium described above is increased by the stirring function of these inclined guide plates 33a and 33b.

That is, the inclined guide plates 33a and 33b are
The inner diameter is smaller than that of the superconducting coil 7 and the outer diameter is larger than that of the superconducting coil 7, and it is provided at an angle of 20 to 70 degrees with respect to the axis of the superconducting coil 7.
Therefore, when the superconducting coil 7 is quenched and helium gas is generated, and this helium gas rises, the ascending force is generated by the inclined guide plates 33a and 33b along the surface of the superconducting coil 7 as indicated by the two-dot chain line arrow in the figure. It is converted into the force to forcibly circulate liquid helium by stirring. As a result, the effective amount of effective liquid helium increases, and the pressure increase during quenching is suppressed. The inclined guide plate 33b located below can be omitted.

In the superconducting device shown in FIG. 11, the screw device 34 is arranged at a lower position on the axis of the superconducting coil 7, and the force of the screw device 34 causes the superconducting coil 7 to move as indicated by the two-dot chain line arrow in the figure. The liquid helium is forcibly stirred and circulated along the surface of the, thereby increasing the effective amount of liquid helium. The screw device 34 may be constantly operated, or may be started when the superconducting coil 7 is quenched.

In the example shown in FIG. 12, the internal space 11 of the bottomed structure 9 shown in FIG. 1 is connected via a pipe 25 to a variable volume device 26 arranged outside. The variable volume device 26 is composed of a cylinder 27, a piston 28 reciprocally arranged in the cylinder 27, and a drive mechanism (not shown) that drives the piston 28 when the superconducting coil 7 is quenched. . In this example, the piston 28
The liquid helium invading the bottomed structure 9 is pushed out or pulled in by actively driving the liquid helium, thereby forcibly creating a flow of liquid helium near the surface of the superconducting coil 7 and The amount of effective liquid helium is increasing. Therefore, in this example, the internal space 11 is used as a space for stirring.

In the superconducting device shown in FIG. 13, the amount of effective liquid helium is increased by forming the superconducting coil 7 in a multi-layer structure. Even with this configuration, it is possible to suppress the pressure increase during the quench.

In the superconducting device shown in FIG. 14, a good heat conducting member 3 made of copper or aluminum in liquid helium 8 is used.
By arranging a plurality of 5 in a relationship extending in the vertical direction, the effective amount of effective liquid helium is increased.

In the superconducting device shown in FIG. 15, a heat storage material 36 having a large heat capacity, such as Er ₃ Ni, is arranged in liquid helium 8 and the heat storage material 36 absorbs heat generated when the superconducting coil 7 is quenched. I am trying.

Even with this structure, it is possible to suppress the pressure increase during the quench. In each of the above-mentioned examples, liquid helium is used as the cryogenic refrigerant liquid, but it goes without saying that the present invention can be applied to the case of using another cryogenic refrigerant liquid such as liquid nitrogen. Further, the superconducting coil can be applied to any of magnetic field generation, current limiting device, transformer, and the like.

[0052]

As described above, according to the present invention,
Even when the superconducting coil is quenched, the pressure rise can be suppressed without opening the cryogenic container to the atmosphere, which contributes to the improvement of safety and the expansion of applicability.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a superconducting device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the pressure suppression principle of the superconducting device according to the present invention.

FIG. 3 is a diagram for explaining the pressure suppression principle of the superconducting device according to the present invention.

FIG. 4 is a diagram for explaining the pressure suppression principle of the superconducting device according to the present invention.

FIG. 5 is a schematic configuration diagram of a main part in a superconducting device according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a main part in a superconducting device according to a third embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a main part in a superconducting device according to a fourth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a main part in a superconducting device according to a fifth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a main part in a superconducting device according to a sixth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a main part in a superconducting device according to a seventh embodiment of the present invention.

FIG. 11 is a schematic configuration diagram of a main part in a superconducting device according to an eighth embodiment of the present invention.

FIG. 12 is a schematic configuration diagram of a main part in a superconducting device according to a ninth embodiment of the present invention.

FIG. 13 is a schematic configuration diagram of a main part in a superconducting device according to a tenth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of a main part of a superconducting device according to an eleventh embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a main part in a superconducting device according to a twelfth embodiment of the present invention.

[Explanation of symbols]

1 ... Cryogenic container 2 ... Outer tank 3,31 ... Inner tank 4 ... Vacuum heat insulating layer 5 ... Injection pipe 6 ... Safety valve 7 ... Superconducting coil 8 ... Liquid helium 9, 9a, 9b, 9c ... Bottom structure 10 ... 1st pressure rise suppression space 11, 11a, 11b, 11c ... 2nd pressure rise suppression space 12 ... GMJT refrigerator 13 ... Final heat exchanger 21 ... JT valve 22 ... Heat shield plate 26 ... Volume variable device 27 ... Cylinder 28 ... Piston 30 ... Buffer tank 32 ... Partition walls 33a, 33b ... Inclined guide plate 34 ... Screw device 35 ... Good heat conduction member 36 ... Heat storage material

Front page continued (72) Inventor Tsukushi Hara 1-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Company (72) Inventor Masahiko Takahashi 1 Komukai-Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Stock-sharing ceremony Corporate Toshiba Research & Development Center (72) Inventor Hideo Hatakeyama 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki City, Kanagawa Stock Company Toshiba Research & Development Center (72) Inventor Hideki Nakagome Komukai-shi Toshiba, Kawasaki-shi, Kanagawa No. 1 Incorporated company Toshiba Research & Development Center

Claims (10)

[Claims] 1. A superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, and a pressure rise suppression leading to a region in which the cryogenic refrigerant liquid is housed is suppressed in the cryogenic container. A superconducting device having a space. 2. The pressure rise suppressing space is arranged with a first pressure rise suppressing space formed by a space above the liquid surface of the cryogenic refrigerant liquid, and an opening portion in the cryogenic refrigerant liquid with its opening downward. The superconducting device according to claim 1, wherein the superconducting device is configured by a second pressure rise suppressing space having a variable volume formed by an inner space of the bottomed structure. 3. A superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein a buffer tank which communicates with a space above the liquid surface of the cryogenic refrigerant liquid to form a pressure rise suppressing space is provided. A superconducting device, which is provided. 4. A superconducting device comprising a superconducting coil and a cryogenic refrigerant liquid contained in a cryogenic container, wherein the cryogenic refrigerant liquid is agitated in the cryogenic refrigerant liquid at least during quenching of the superconducting coil. A superconducting device, which is provided with a stirring means for 5. The agitating means is provided at at least one of an upper position and a lower position with the superconducting coil as a boundary, and the cryogenic refrigerant liquid is provided along the surface of the superconducting coil when the superconducting coil is quenched. The superconducting device according to claim 4, wherein the superconducting device is configured by an inclined guide plate that forcibly circulates. 6. The screw means is provided below the superconducting coil, and is a screw device for forcibly circulating the cryogenic refrigerant liquid along the surface of the superconducting coil at least when the superconducting coil is quenched. The superconducting device according to claim 4, wherein the superconducting device is provided. 7. The stirring means comprises a variable-volume stirring space formed by an internal space of a bottomed structure which is arranged in the cryogenic refrigerant liquid with an opening downward, and a volume of the stirring space. The superconducting device according to claim 4, wherein the superconducting device comprises a variable volume device that variably agitates the cryogenic refrigerant liquid. 8. A superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are contained in a cryogenic container, wherein the superconducting coil is formed in a multi-layer structure. 9. A superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein a good heat conducting member is disposed in the cryogenic refrigerant liquid. . 10. A superconducting device in which a superconducting coil and a cryogenic refrigerant liquid are housed in a cryogenic container, wherein a heat storage material is arranged in the cryogenic refrigerant liquid.