JP5332217B2 - Superconducting device - Google Patents

Description

  The present invention relates to a superconducting device, and more specifically, in a superconducting device in which a superconducting coil excited by an alternating current is accommodated in a vacuum heat insulating container, the cooling mechanism of the superconducting coil is improved to reduce the size and weight of the entire superconducting device. And to improve the superconducting performance.

  Conventionally, superconducting motors and transformers have been provided as devices using superconducting coils. For example, in Japanese Patent Laid-Open No. 2007-37343 (Patent Document 1), the present applicant has proposed a superconducting motor using a superconducting coil as a stator of a superconducting motor. In the superconducting motor, a heat insulating container is buried in the groove portion of the field side stator, and the superconducting coil is accommodated in the heat insulating container. A liquid nitrogen tank is connected to the heat insulating container through a heat insulating pipe, and a cooling system for circulating liquid nitrogen as a refrigerant is provided to cool the superconducting coil to the superconducting temperature.

A general configuration of a cooling system that circulates liquid nitrogen as a refrigerant and cools the superconducting coil is configured as shown in FIG. That is, the cooling system 1 accommodates the superconducting coil 3 in the heat insulating container 2, attaches the heat insulating pipe 5 to the heat insulating container 2 via the connector 4, and circulates liquid nitrogen as a refrigerant. The heat insulation pipe 5 is provided with a pump 6 for powering the circulation of liquid nitrogen, and a reservoir 8 to which a refrigerator 7 is attached.
In this way, the entire superconducting coil is cooled by filling the heat insulating container containing the superconducting coil with liquid nitrogen.

The cooling system using liquid nitrogen as a refrigerant is used when an alternating current is passed through a superconducting coil.
When an alternating current is passed through the superconducting coil, the superconducting wire itself generates heat and an AC loss (AC loss) is generated. The superconducting wire is quenched due to the AC loss, and the superconducting performance is easily lost. The AC loss is determined by the magnitude of the current flowing through the superconducting coil and the strength of the magnetic field applied to the superconducting coil at each position of the superconducting coil.
FIG. 5 is a diagram showing an outline of AC loss with respect to a magnetic field. When the magnetic field is strong, a large AC loss occurs regardless of the temperature at which the superconducting coil is cooled.
For this reason, when an alternating current is passed through the superconducting coil, it is important to reliably cool the superconducting coil and efficiently remove heat generation. By using a cooling system using liquid nitrogen as a refrigerant, the superconducting coil The whole can be reliably cooled.

However, since liquid nitrogen can exist as a liquid only at a temperature of 64K (Kelvin) or higher, when liquid nitrogen is used as a refrigerant, the superconducting coil cannot be cooled to a temperature lower than that. On the other hand, it is known that the performance of the high-temperature superconducting wire constituting the superconducting coil is further improved when cooled to 64K or lower.
For this reason, when the superconducting coil is cooled using liquid nitrogen, the superconducting coil has a lower critical current than the case where the superconducting coil is cooled to 64K or less, and the superconducting state is maintained only in a range where the magnetic field applied to the superconducting coil is weak. There is a problem that can not be.

Moreover, when cooling with refrigerants, such as liquid nitrogen, there exists a problem that the heat insulation from the outside must be suppressed by making a heat insulation container into a double tank, and the structure of a heat insulation container becomes complicated.
Furthermore, in order to circulate the refrigerant, the cooling system requires a heat insulating pipe, a pump, a reservoir, a heat exchanger, and the like in addition to the refrigerator. In addition, a special connector is required for piping of liquid refrigerant such as liquid nitrogen, and there is a problem that the structure of the cooling system is complicated and expensive.
Furthermore, the cooling system has a problem that the size of the refrigerator is increased because the heat entering from the outside in the heat insulating piping or the like or the heat generated by the pump must be cooled.

  In particular, when the current flowing through the superconducting coil is an alternating current, an alternating current loss occurs as described above. Therefore, the cooling system must reliably cool the alternating current loss, and a larger refrigerator is required. There is a problem of becoming. In particular, when the magnetic field applied to the superconducting coil is large, or when the number of turns of the superconducting coil is large and the dose is large, the AC loss also increases, so that the cooling system is enlarged and the entire apparatus equipped with the superconducting coil is also enlarged. There's a problem.

JP 2007-37343 A

  The present invention has been made in view of the above problems, and it is an object of the present invention to improve the superconducting performance by reducing the size and weight of the superconducting device when an alternating current is passed through the superconducting coil.

In order to solve the above problems, the present invention provides a superconducting coil wound with a superconducting wire excited by an alternating current;
A vacuum insulation container that contains the superconducting coil in a vacuum and is not filled with a refrigerant;
A refrigerator having a cold head protruding into the vacuum insulation container;
A superconducting coil direct cooling heat transfer material for connecting the cold head and the superconducting coil in the vacuum insulation container;
The superconducting coil is composed of a plurality of single pancake coils or double pancake coils. These superconducting coils are laminated and fixed on the outer periphery of the central connecting core, and a plurality of metal plates are spaced between and on both sides of the laminated superconducting coils. Open and place
The heat transfer material is connected between the cold head connection portion connected to the cold head, the metal connection portions at both ends connected to the metal plates arranged on both sides, and the intermediate portion connected to the metal plate arranged between the superconducting coils. metal connecting portion protruding branches, metal connecting portions of said end that the branch is a shape with a reduced thermal resistance than the intermediate metal connecting portion,
A superconducting device is characterized in that the superconducting temperature of the superconducting coil is 10 K or more and 60 K or less, the magnetic field generated by the superconducting coil is 0.1 T or more and 20 T or less, and the alternating current flowing through the superconducting coil is 10 A or more and 1000 A or less. doing.

  In the superconducting device of the present invention, a superconducting coil for exciting an alternating current is accommodated in a vacuum heat insulating container, and the superconducting coil is directly cooled by a refrigerator through a heat transfer material. For this reason, it is not necessary to use a refrigerant of liquid nitrogen as in the prior art, and the superconducting coil can be cooled to a temperature lower than 64 K, which is the limit temperature that can be cooled with liquid nitrogen. By this cooling, even when the critical current of the superconducting coil is large and the magnetic field applied to the superconducting coil is strong, the superconducting coil can be brought into the superconducting state, and the performance of the superconducting coil can be improved.

  In addition, since the critical current of the superconducting coil is increased by cooling the superconducting coil to a lower temperature than when liquid nitrogen is used, the same ampere-turn as the case of using liquid nitrogen (the current value flowing through the superconducting coil and the superconducting coil In order to generate the magnetomotive force of the product of the number of turns, the number of turns of the superconducting coil may be small, and the dose of the superconducting wire can be reduced.

  In particular, since an alternating current flows through the superconducting coil of the superconducting device of the present invention, the AC loss generated in the superconducting coil is determined by the dose of the superconducting wire, and the AC loss decreases as the dose of the superconducting wire decreases. For this reason, the cooling system for cooling AC loss can be reduced in size. In addition, since the dose of the superconducting wire can be reduced, the superconducting coil itself can be reduced in size and weight.

  Furthermore, since no refrigerant is used in the present invention, a heat insulation pipe, a pump, a reservoir, a heat exchanger, and the like are not required in the cooling system, so that the cost of the cooling system can be suppressed and the size and weight can be reduced. Furthermore, since the intrusion heat from the heat insulating pipes and the like, heat generation by the pump, etc. are reduced, the refrigerator does not need to cool the heat generation, and the refrigerator can be miniaturized.

As described above, the superconducting temperature of the superconducting coil is set to 10K to 60K.
This is because when the superconducting temperature, that is, the cooling temperature of the superconducting coil is higher than 60K, the performance of the superconducting coil does not change as compared with the case of using a liquid nitrogen refrigerant. In addition, when the superconducting temperature of the superconducting coil is less than 10K, the cooling capacity of the refrigerator is reduced.
At this time, the magnetic field generated by the superconducting coil is not less than 0.1T and not more than 20T, more preferably not less than 0.5T and not more than 20T. The current flowing through the superconducting coil is 10A or more and 1000A or less.

The heat insulating container is composed of one tank made of metal or FRP,
The heat transfer material is made of a metal plate made of a metal having a high thermal conductivity selected from copper and aluminum or a metal wire insulatively coated with a conductor made of the metal, and the container is filled with a heat insulating material. It is preferable.

When cooling with a refrigerant such as liquid nitrogen, it is necessary to use a heat insulating container as a double tank to suppress heat intrusion from the outside. However, in the present invention, since the heat insulating container is evacuated, a single tank is used. However, sufficient heat insulation performance can be provided.
In addition, the superconducting coil can be cooled from the cold head of the refrigerator through the heat transfer material by using a metal having a high thermal conductivity such as copper or aluminum as the heat transfer material.
Furthermore, since the space in the heat insulating container is filled with a heat insulating material, it is possible to prevent radiant heat from being transmitted to the superconducting coil .

When the heat insulating container is made of a metal material, since the strength is strong, the thickness of the heat insulating container can be reduced, and the size can be reduced. Further, since the periphery of the heat insulating container is in contact with the atmosphere, natural cooling and cooling with cooling water can be easily performed at low cost.
Further, when the heat insulating container is made of FRP (fiber reinforced resin), even if an alternating current is passed through the superconducting coil, an induced current does not flow through the heat insulating container to generate heat, and the loss of the entire superconducting device is reduced and cooling efficiency is reduced. Can be increased.

The superconducting coil is composed of a plurality of single pancake coils or double pancake coils, and these superconducting coils are laminated and fixed to a central connecting core made of resin,
Flange portions are provided at both ends in the axial direction of the central connecting core member, a metal plate of the same type as the heat transfer material is fixed to the flange portion, the metal plate and the heat transfer material are fixed by soldering, and Or
The metal plate is disposed between the superconducting coils to be laminated, the metal plate is fixed to the heat transfer material by soldering, and an insulating film is interposed between the metal plate and the superconducting coil. preferable.

  According to the said structure, since the heat-transfer material is being fixed to the metal plate provided in the both ends of the axial direction of a superconducting coil, a superconducting coil can be cooled from both ends. Moreover, since the metal plate is arrange | positioned between the superconducting coils to laminate | stack, it can cool also from between superconducting coils.

  As described above, according to the superconducting device of the present invention, an AC current is passed through the superconducting coil, and the superconducting coil is directly cooled by a refrigerator through a heat transfer plate, thereby superconducting at a lower temperature than when liquid nitrogen is used. A coil can be used. Furthermore, the cooling system can be reduced in size and weight, and the superconducting coil itself can be reduced in size and weight, so that the entire superconducting device is reduced in size and weight.

Embodiments of the present invention will be described with reference to the drawings.
1 to 3 show a first embodiment of the present invention.
In the superconducting device 10 of the present invention, a superconducting coil 11 wound with a superconducting wire excited by an alternating current is accommodated in a vacuum heat insulating container 12, and the superconducting coil 11 is cooled by a refrigerator 13.

The vacuum heat insulating container 12 is a container having a circular cross section made of stainless steel, which is a metal material, and the inside is evacuated without being filled with a refrigerant.
A through hole 12 a is provided in the side wall of the vacuum heat insulating container 12, and the heat transfer tube 14 of the refrigerator 13 is inserted and fixed in the through hole 12 a, and the refrigerator 13 is attached to the vacuum heat insulating container 12. A cold head 15 is attached to the tip of the heat transfer tube 14 of the refrigerator 13, and the cold head 15 protrudes into the vacuum heat insulating container 12.
In the present embodiment, the refrigerator 13 uses AL325 manufactured by CryoMec, but SRDK408 manufactured by Sumitomo Heavy Industries, RS373 manufactured by Aisin, or the like may be used.

A heat transfer material 16 for directly cooling the superconducting coil 11 is provided in the vacuum heat insulating container 12. The heat transfer material 16 is made of a copper plate having a high thermal conductivity. The heat transfer material 16 connects the cold head 15 and the superconducting coil 11 to cool the superconducting coil 11.
The heat transfer material 16 may be a metal plate made of a metal having a high thermal conductivity such as aluminum instead of copper. Moreover, it is good also as metal wires, such as a litz wire which carried out the insulation coating of the conductor which consists of this metal.

  Further, the vacuum heat insulating container 12 is filled with a heat insulating material 17 for preventing radiant heat from being transmitted to the superconducting coil 11, and the heat insulating material 17 is made of laminated aluminum foil. Although only a part of the heat insulating material 17 is shown in FIG. 1, the heat insulating material 17 is filled in the entire vacuum heat insulating container 12.

Superconducting coil 11 is formed of a plurality of single pancake coils 11a. Each single pancake coil 11a is obtained by flatwise winding a superconducting wire around a cylindrical central connecting core 11b made of resin, and a plurality of single pancake coils 11a are stacked and fixed in the axial direction to form one superconducting coil. 11 is set. End faces of the superconducting wires of the pancake coils at both ends are connected to a power source (not shown) through lead wires (not shown).
The superconducting coil 11 may be formed from a double pancake coil.

  Circular flange portions 11c having the same diameter as the superconducting coil 11 are provided at both ends in the axial direction of the central connecting core member 11b. The inner surface of the flange portion 11c is brought into contact with both end surfaces in the axial direction of the superconducting coil 11, and a circular metal plate 18A having a diameter larger than that of the superconducting coil 11 is fixed to the outer surface of the flange portion 11c with an adhesive. That is, the superconducting coil 11 and the metal plate 18A are insulated by the flange portion 11c. The metal plate 18A is made of copper which is the same kind of metal as the heat transfer material 16.

  Further, a metal plate 18B is disposed between each single pancake coil 11a, and an insulating film 19 is interposed between the metal plate 18B and the superconducting coil 11. The insulating film 19 has a thickness as small as possible in order to reduce the thermal resistance. In this embodiment, a polyimide film having a thickness of 12.5 μm is used.

  Furthermore, the heat transfer material 16 is connected to the outer peripheral side of the inner surfaces of the metal plates 18A and 18B by soldering. The heat transfer material 16 is formed by punching a copper plate, and a cold head connection portion 16a connected to the cold head 15, a metal plate connection portion 16b connected to the metal plates 18A at both ends of the superconducting coil 11, and a single pancake coil 11a. And a metal plate connecting portion 16c connected to the metal plate 18B between them.

The cross-sectional area of the metal plate connection portion 16b is larger than the cross-sectional area of the metal plate connection portion 16c. When an alternating current is passed through the superconducting coil 11, a magnetic field having a component perpendicular to the tape surface of the superconducting wire is generated at both ends in the axial direction of the superconducting coil 11, and the magnetic field of the vertical component is an AC loss of the superconducting coil 11. That is, it causes heat generation. Therefore, by increasing the cross-sectional area of the metal plate connecting portion 16b to be connected to the metal plate 18 A of the both ends of the superconducting coil 11, the heat transfer member 16 from the end positions in the axial direction of the superconducting coil 11 to the cold head 15 The thermal resistance is made small.
Further, a slit 16d is formed on the surface of the heat transfer material 16 in parallel with the direction in which the magnetic flux flows. The slit 16d blocks the eddy current route that flows on the surface of the heat transfer material 16 when an alternating current is passed through the superconducting coil 11, thereby reducing the heat generated by the induced current and eddy current generated in the heat transfer material 16. Yes. That is, in FIG. 1, although the slit 16d is put in the vertical direction, it is not restricted to the vertical direction.

Next, the operating conditions of the superconducting device 10 of the present invention will be described.
The refrigerator 13 of the superconducting device 10 of the present invention cools the heat generated in the superconducting wire (AC loss, AC loss) when an AC current is passed through the superconducting coil 11.
FIG. 2 is a diagram showing the performance of the model number AL325 of the cryogenic refrigerator 13.
For example, at 70K, there is a cooling capacity of about 280W, and at 20K, there is a cooling capacity of about 70W. That is, the refrigerator 13 can cool an AC loss of about 280 W when maintaining 70 K, but can cool only a loss of about 70 W at 20 K, and the cooling capacity is reduced to 1/4 times. doing.

On the other hand, FIG. 3 is a diagram showing the critical current with respect to the magnetic field when the superconducting coil 11 is cooled from 20K to 77K. For example, when the superconducting coil 11 is used with a magnetic field of 0.5 T, the critical current is about 30A at 70K, and about 600A when cooled to 20K, which is about 20 times.
At this time, the ampere turn indicating the magnetomotive force of the superconducting coil 11 is defined by the product of the current flowing through the superconducting coil 11 and the number of turns of the superconducting coil 11.
For this reason, assuming that the ampere turn is constant, when the superconducting coil 11 is used at 20K, the critical current is 20 times that at 70K, so the number of turns may be 1/20 times. That is, the dose of the superconducting wire becomes 1/20 times.

  As described above, the AC loss is a loss due to heat generated in the superconducting wire when an AC current is passed through the superconducting coil 11, and the AC loss is proportional to the dose of the superconducting wire. For this reason, when the superconducting coil 11 is used at 20K, the AC loss is 1/20 times that when used at 70K.

  Therefore, when an alternating current is passed through the superconducting coil 11, when the superconducting coil 11 is used at 20K, the cooling capacity of the refrigerator 13 is ¼ times that when used at 70K. The amount of heat generated by the AC loss to be cooled by the refrigerator 13 is also 1/20 times, and the power necessary for cooling the superconducting coil 11 is 1/5 times. That is, the decrease in the heat generation amount due to the AC loss is greater than the decrease in the cooling capacity of the refrigerator 13.

  As described above, the superconducting device 10 according to the present invention uses the superconducting coil 11 by cooling the superconducting coil 11 to a temperature in a range where the decrease in the heat generation amount due to the AC loss is larger than the decrease in the cooling capacity of the refrigerator 13. Improved performance.

  Further, compared to the case where the superconducting coil 11 is cooled to 70 K using a cooling system using liquid nitrogen as a refrigerant, the superconducting device 10 of the present invention can be cooled to 20 K, so the dose of the superconducting coil 11 is small and AC is reduced. In addition to reducing the loss, it is not necessary to cool the heat intrusion from the cooling system, the loss due to the eddy current of the heat insulating container 12, the heat generation of the pump, or the like. For this reason, only the AC loss from the superconducting wire having a small number of turns needs to be cooled, and if the AC loss can be reduced to 1/4 times the loss when liquid nitrogen is used as the refrigerant, the superconducting device 10 of the present invention can be used. However, the cooling efficiency is improved.

Further, when a cooling system using liquid nitrogen as a refrigerant is used, the superconducting coil 11 can be cooled only to 64K. In this case, when a high magnetic field is generated in the superconducting coil 11, the superconducting coil 11 maintains a superconducting state. I can't. As shown in FIG. 3, when the superconducting coil 11 is cooled to 70K, the superconducting state can be maintained when the magnetic field applied to the superconducting coil 11 is about 0.5 T or less. In such a case, the superconducting state cannot be maintained.
On the other hand, when the superconducting coil 11 is cooled to 20K in the superconducting device 10 of the present invention, the superconducting state is maintained even if the magnetic field applied to the superconducting coil 11 is 12T as shown in FIG.

  Therefore, the operating condition of the superconducting device 10 of the present invention is that the superconducting temperature of the superconducting coil 11 is reduced to 10K or more and 60K or lower than that when the superconducting coil 11 is cooled with liquid nitrogen. 20T or less, more preferably 0.5T or more and 12T or less, and the current flowing through the superconducting coil 11 is 10A or more and 1000A or less. In this case, the superconducting coil 11 maintains the superconducting state, and the superconducting device 10 can be operated.

  Thus, according to the present invention, the superconducting coil 11 that excites alternating current is accommodated in the vacuum heat insulating container 12, and the superconducting coil 11 is directly cooled by the refrigerator 13 via the heat transfer material 16. Therefore, it is not necessary to use a liquid nitrogen refrigerant as in the prior art, and the superconducting coil 11 can be cooled to a temperature lower than 64K, which is the limit temperature that can be cooled with liquid nitrogen. By this cooling, even when the critical current of the superconducting coil 11 is large and the magnetic field applied to the superconducting coil 11 is strong, the superconducting coil 11 can be brought into the superconducting state, and the performance of the superconducting coil 11 can be improved.

Further, since the critical current of the superconducting coil 11 is increased, in order to generate a magnetomotive force of the same ampere turn (product of the current value flowing through the superconducting coil 11 and the number of turns of the superconducting coil 11) as in the case of using liquid nitrogen, A small number of turns of the superconducting coil 11 is sufficient, and the dose of the superconducting wire can be reduced.
In particular, since an alternating current flows through the superconducting coil 11 of the superconducting device 10 of the present invention, the AC loss generated in the superconducting coil 11 is determined by the dose of the superconducting wire, and the AC loss decreases as the dose of the superconducting wire decreases. . For this reason, the cooling system for cooling AC loss can be reduced in size. Since the dose of the superconducting wire can be reduced, the superconducting coil 11 itself can be reduced in size and weight.

  Moreover, since no refrigerant is used in the present invention, a heat insulation pipe, a pump, a reservoir, a heat exchanger or the like is not required in the cooling system, and the cost of the cooling system can be suppressed, and the size and weight can be reduced. Furthermore, since the intrusion heat from the heat insulating piping or the like, the heat generation by the pump, and the like are reduced, the refrigerator 13 does not need to cool the heat generation, and the refrigerator 13 can be downsized.

  In addition, this invention is not limited to the said embodiment, The various form within the claim of this invention is included.

1 is an overall schematic configuration diagram showing a first embodiment of a superconducting device according to the present invention. It is a figure which shows the cooling performance of a refrigerator. It is a figure which shows the critical current with respect to the magnetic field in the superconducting temperature of a superconducting coil. It is a figure of the cooling system which used liquid nitrogen as a refrigerant. It is a figure which shows the alternating current loss with respect to a magnetic field.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Superconducting device 11 Superconducting coil 11a Single pancake coil 11b Center connection core material 11c Flange part 12 Vacuum heat insulating container 13 Refrigerator 15 Cold head 16 Heat transfer material 17 Heat insulating material 18 Metal plate 19 Insulating film

Claims (3)

A superconducting coil wound with a superconducting wire excited by an alternating current;
A vacuum insulation container that contains the superconducting coil in a vacuum and is not filled with a refrigerant;
A refrigerator having a cold head protruding into the vacuum insulation container;
A superconducting coil direct cooling heat transfer material for connecting the cold head and the superconducting coil in the vacuum insulation container;
The superconducting coil is composed of a plurality of single pancake coils or double pancake coils. These superconducting coils are laminated and fixed on the outer periphery of the central connecting core, and a plurality of metal plates are spaced between and on both sides of the laminated superconducting coils. Open and place
The heat transfer material is connected between the cold head connection portion connected to the cold head, the metal connection portions at both ends connected to the metal plates arranged on both sides, and the intermediate portion connected to the metal plate arranged between the superconducting coils. metal connecting portion protruding branches, metal connecting portions of said end that the branch is a shape with a reduced thermal resistance than the intermediate metal connecting portion,
A superconducting device, wherein a superconducting temperature of the superconducting coil is 10 K or more and 60 K or less, a magnetic field generated by the superconducting coil is 0.1 T or more and 20 T or less, and an alternating current flowing through the superconducting coil is 10 A or more and 1000 A or less. The superconducting device according to claim 1, wherein the vacuum heat insulating container is made of one tank made of a metal material or FRP, and the metal plate and the heat transfer material are made of copper or aluminum . The superconducting device according to claim 1, wherein a slit is provided in the heat transfer material .

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