JP2000269021A - Superconductor magnet and eddy current suppressing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce heat generation of an inner layer not only when the field fluctuates due to external environment but also when a coil is excited or demagnetized by providing a second layer with at least one discontinuous part for dividing the second layer in the axial direction of a pipe in the inner layer. SOLUTION: An insulating inner layer 10 comprises a first layer 11 formed on the outer surface of an inner layer 2, and a second layer formed on the first layer 11. The inner layer 2 is a hollow tubular container formed of a metallic material having a relatively high electric resistance and closed annularly as a whole. The second layer 12 is composed of a material having relatively low electrical resistance and provided with a discontinuous part 13 for dividing the second layer 12 in the axial direction A1 (inner layer pipe axis) of the pipe in the inner layer 2. The discontinuous part 13 is a groove-like recess formed by removing the second layer 12 along the inner layer pipe circumferential axis A2, i.e., the axis in the direction of circulating around the inner layer pipe axis A1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet device and a superconducting magnet device which generate a magnetic field by passing a permanent current in a state where a coil formed of a superconducting material is cooled to an extremely low temperature and in a superconducting state. The present invention relates to an eddy current suppressing method.

[0002]

2. Description of the Related Art A superconducting magnetic levitation railway has been developed as an alternative to a conventional railway utilizing wheels rolling on a traveling path such as a rail due to rolling friction, and tests and the like have been advanced for practical use. ing. This superconducting magnetic levitation railway is configured by providing a superconducting magnet device in a vehicle and arranging a coil in a guideway on the ground side. The coils on the ground are connected to each other by a predetermined connection method, and energized by power equipment. With such a configuration, by applying a predetermined current to the coil near the location where the vehicle exists, the attracting magnetic force and the repulsive magnetic force are generated to propel the vehicle, and the superconducting magnet device passes near the coil at high speed. As a result, a repulsive magnetic force and an attractive magnetic force are generated in a coil near a location where the vehicle is present by the electromagnetic induction effect caused by the electromagnetic force, and the vehicle is levitated.

FIG. 4 is a partially cutaway perspective view showing an example of the configuration of a superconducting magnet device mounted on a superconducting magnetic levitation railway vehicle. As shown in FIG. 4, this superconducting magnet device 2
00 has an outer tub 1, an inner tub 2, a refrigerator 4, and a power lead 5.

FIG. 5 is a partially cutaway perspective view showing the configuration of the inner tank 2 and the coils in the superconducting magnet device 200. As shown in FIG. 5, inside the inner tank 2, a coil 6 is accommodated via a spacer 2b for maintaining a gap.

[0005] coil 6 is fabricated by a superconducting material such as Nb (niobium) and niobium three tin (Nb ₃ Sn), it is formed in a closed ring as a whole. Also, the inner tank 2
It is a hollow tubular container made of a metal material such as stainless steel, and the tube has a closed ring as a whole. This inner tank 2
Is filled with liquid helium (not shown) as a refrigerant, and the coil 6 is immersed in liquid helium. The liquid helium is kept at an extremely low temperature of about 4K (K: absolute temperature) by the refrigerator 4 and is supplied to the inner tank 2 from the liquid helium tank 4a. The outer tub 1 is a hollow box-shaped container. Also,
The inner tank 2 is provided with a load supporting member 2a, whereby the inner tank 2 is housed in the outer tank 1 in an insulated state.

With the above configuration, the coil 6 is
Since it is cooled to an extremely low temperature of about K, it is in a superconducting state in which the electric resistance becomes almost zero. Therefore, when a current is supplied from the power lead 5 and a current flows through the coil 6 by the permanent current switch 7, this current continues to flow almost without being attenuated by the resistance, and becomes a permanent current. At this time, the energized coil 6 generates a magnetic field and acts as an electromagnet.

In this case, when there is a magnetic field fluctuation in the external environment (such as a harmonic magnetic field generated while the superconducting magnetic levitation railway vehicle is running), the lines of magnetic force (magnetic flux) passing through the inner tub 2 change.
Due to the fluctuation of the magnetic field lines (magnetic flux), a vortex current (hereinafter, referred to as “eddy current”) is induced inside the plate material of the inner tank 2 in a direction surrounding the magnetic field lines in a plane perpendicular to the magnetic field lines. . The inner tank 2 is formed of a metal material such as stainless steel, and the metal material such as stainless steel has a relatively high electric resistance value. For this reason, the eddy current receives high electric resistance and generates large Joule heat. The Joule heat gives heat to the liquid helium inside the inner tank 2, evaporates the liquid helium, and causes the superconducting state of the coil 6 to be eliminated (hereinafter, referred to as “quench”).

As a first countermeasure against the above eddy current, there is known a method of arranging a member 3 called a radiation shield member inside the outer tank 1 and outside the inner tank 2 as shown in FIG. Have been. The radiation shield member 3 is formed of a plate material made of a material having a low electric resistance value (hereinafter, referred to as a “low resistance material”), and is formed in a shape that covers the entire inner tank 2. From this, by generating the above-mentioned eddy current inside the radiation shield member 3,
The purpose is to reduce and suppress the eddy current generated inside the plate material of the inner tank 2.

A second measure against the above eddy current is shown in FIG.
In this method, the inner tank has a composite structure consisting of two layers as shown in FIG. As shown in FIG. 6B, the composite inner tank 50 is formed by forming a member 52 made of a low-resistance material such as copper on the outer surface of the inner tank 2 by plating or bonding. It is configured. With such a configuration,
Although the above-mentioned eddy current is generated inside the low-resistance member 52, the resistance value is small, so that the Joule heat generation is small. Therefore, the amount of evaporation of the liquid helium in the inner tank 2 is to be reduced and suppressed.

[0010]

However, the above-described eddy current suppressing method of the conventional superconducting magnet device 200 includes a case where a magnetic field is generated in the superconducting magnet device (hereinafter referred to as "excitation") and a case where the superconducting magnet device is used. There was a problem when stopping the magnetic field of 200 (hereinafter, referred to as “at the time of demagnetization”). That is, at the time of excitation, the DC current value is increased from a state where the permanent current value in the coil 6 is zero to a predetermined permanent current value. At the time of demagnetization, the state where the permanent current value within the coil 6 is zero from the state where the permanent current value is the predetermined value. The DC current value is decreased until. For this reason, the coil current increases during excitation and decreases during demagnetization, but this causes a slowly fluctuating magnetic field in the coil 6 itself. Large eddy currents are generated. Therefore, when the resistance is rather low, the eddy current is large, so that excessive Joule heat is generated, and the liquid helium inside the inner tank 2 evaporates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the problem to be solved by the present invention is not only when the magnetic field fluctuates due to the external environment, but also when the coil is excited or degaussed. It is an object of the present invention to provide a superconducting magnet device capable of reducing heat generation of a superconducting magnet and an eddy current suppressing method in the superconducting magnet device.

[0012]

In order to solve the above problems, a superconducting magnet device according to the present invention comprises a closed annular coil made of a superconducting material and a closed ring made of a metal material as a whole. In a superconducting magnet device having a tubular shape and an inner tank for accommodating the coil together with a refrigerant, and an outer tank for accommodating the inner tank in an insulated state, the superconducting magnet device is formed of an electrically insulating material and formed on an outer surface of the inner tank. A first layer formed of a low-resistance material having a low electric resistance, and a second layer formed on the first layer, wherein the second layer includes an inner portion that is an axis of the pipe in the inner tank; At least one discontinuous portion that divides the second layer in the direction of the tank tube axis is provided.

In the above superconducting magnet device, preferably, the discontinuous portion of the second layer is formed by removing the second layer so as to orbit around the inner tube axis.

In the above superconducting magnet apparatus, preferably, the discontinuous portion is filled with an electrically insulating material.

In the above-described superconducting magnet device, preferably, the first layer is an electrically insulating material wound around the outer surface of the inner tank so as to spirally surround the axis of the inner tank tube. It is formed by a fiber member composed of

In the above superconducting magnet device, preferably, the electrical insulating material includes a ceramic material containing silicon carbide and silicon dioxide, and a heat-resistant organic material containing aramid fiber.

In the above-described superconducting magnet apparatus, preferably, the fiber member includes a fiber, a string-like member made of the fiber, a woven fabric member made of the fiber, and a nonwoven fabric member made of the fiber.

In the above superconducting magnet device, preferably, the electrically insulating material is a good thermal conductor.

In the above superconducting magnet device, preferably, the closed ring includes a circle, an ellipse, and a race track shape.

The method for suppressing eddy current in a superconducting magnet device according to the present invention is characterized in that a closed annular coil made of a superconducting material and a refrigerant formed of a metallic material and formed into a closed annular tube as a whole are provided. A first layer made of an electrically insulating material is formed on an outer surface of the inner tank of a superconducting magnet device having an inner tank that houses the coil and an outer tank that houses the inner tank in an insulated state, and has an electrical resistance value. Is formed on the first layer, and the second layer is formed in a direction of an inner tank pipe axis which is an axis of the pipe in the inner tank.
The layer is divided to provide at least one discontinuous portion, and the generation of an eddy current, which is a current circulating in the direction of the inner tank tube axis, in the second layer is prevented.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments and drawings, the same reference numerals denote members having the same configuration and operation.

(1) First Embodiment FIG. 1 is a view showing a configuration of an inner tank in a first embodiment of a superconducting magnet device according to the present invention. FIG. 1A is an overall perspective view, and FIG. (B) has shown the expanded sectional view of a discontinuous part, respectively. The superconducting magnet device 101 of the first embodiment differs from the conventional example in that the superconducting magnet device 101 has an insulating inner tank 10 having a configuration different from the combination of the conventional inner tank 2 and the low-resistance member 52. Superconducting magnet device 101 of the first embodiment
Although not shown, the outer tank 1 and the insulated inner tank 10
, A refrigerator 4 and a power lead 5. Among these components, the outer tub 1, the refrigerator 4 and the power lead 5
Has exactly the same configuration and operation as the conventional superconducting magnet device 200 described above.

As shown in FIG. 1B, the insulating inner tank 10 has a first layer 11 formed on the outer surface of the inner tank 2 and a second layer 11 formed on the first layer 11. It has. Inner tank 2
Is a hollow tubular container formed of a metal material having a relatively high electric resistance value, for example, stainless steel, as described above, and has a closed ring shape as a whole.

The first layer 11 is formed of an electrically insulating material. Electrically insulating materials are electrically insulating,
Alternatively, it is a substance having a dielectric property, and has a property of not flowing a current even when a voltage is applied. Examples of the electrically insulating material forming the first layer 11 include a ceramic material. Examples of the electrically insulating ceramic material include silicon carbide (SiC), silicon dioxide (SiO ₂ ), diamond, and titanium dioxide (Ti).
O ₂ ) and zirconium oxide (ZrO ₂ ).
Silicon dioxide is also called alumina, and single crystal alumina (sapphire), quartz and the like are crystallized silicon dioxide. Further, titanium dioxide is also called titania, and zirconium oxide is also called zirconia.

The first layer 11 is made of the above-mentioned electrically insulating material,
It may be formed on the outer surface of the inner tank 2 in the form of a film, a layer, or a sheet. Further, the above-mentioned electrical insulating material is formed into a fibrous (thread-like) material, a string-like member made of this fiber, a woven fabric-like member made of this fiber, and a fiber member including a non-woven fabric-like member made of this fiber. A layer may be formed on the outer surface of the inner tank 2.

Examples of the electrically insulating material constituting the first layer 11 include, for example, a heat-resistant organic material in addition to the ceramic material. Examples of the heat-resistant organic material having electrical insulation properties include aromatic polyamide and the like. When the aromatic polyamide is used as a fiber, it is called an aramid fiber or a Kevlar fiber. Further, a layer is formed on the outer surface of the inner tank 2 by using the fiber member including the string member made of aramid fiber, the woven member made of aramid fiber, and the nonwoven member made of aramid fiber. Is also good.

As the electrically insulating material constituting the first layer 11, besides the above, for example, glass fiber, a string-like member made of glass fiber, a woven fabric member made of glass fiber, and a non-woven fabric made of glass fiber A layer may be formed on the outer surface of the inner tank 2 using a fibrous member including a shape member.

The thickness of the first layer 11 is arbitrary, and is 0.1 μm.
It can be up to about m to several mm.

The second layer 12 is made of a low-resistance material having a low electric resistance. As a low resistance material,
Metal materials having low electric resistance such as copper (Cu) and aluminum (Al) are included. In the second layer 12, a discontinuous portion 13 that divides the second layer 12 in a direction of a pipe axis A1 (hereinafter, referred to as an “inner pipe axis”) in the inner tank 2 is formed. The discontinuous portion 13 is a groove-shaped concave portion formed by removing the second layer 12 along the inner tank tube rotation axis A2 which is a direction axis orbiting around the inner tank tube axis A1. The discontinuous portion 13 may have a narrow slit shape.

The thickness of the second layer 12 is arbitrary, and is 0.1 μm.
It can be up to about m to several mm.

With the above-described configuration, the superconducting magnet device 101 of the first embodiment has the following advantages.

1) An eddy current that would otherwise be generated in the second layer 12 of the low-resistance material and supposed to circulate and flow along the inner tank tube axis A1 due to the magnetic field fluctuation is generated in the discontinuous portion 13. As a result, it cannot flow freely in the second layer 12.

2) A first layer 11 made of an electrically insulating material is provided between the second layer 12 made of a low-resistance material and the inner tank 2 made of a metal material having a higher electric resistance. Since it is electrically insulated completely, the eddy current blocked by the discontinuous portion 13 and having no place to go is surely prevented from entering the inner tank 2 and flowing. In this case,
If the first layer 11 made of an electrically insulating material is not provided between the outer surface of the inner tank 2 and the second layer 12 of the low resistance material, the eddy current generated in the second layer 12 is Continuous part 13
However, since the second layer 12 and the inner tank 2 are in close contact with each other and the length of the discontinuous portion 13 is short, the inner tank 2 which is not an electrical insulator even if the electrical resistance is slightly high. It is considered that large eddy currents cannot be prevented and flow of Joule heat in the inner tank 2 cannot be prevented after all.

3) If the first layer 11 is formed of a material that is not only electrically insulating but also a good thermal conductor,
Since it is in an extremely low temperature state substantially equal to that of the inner tank 2, copper (Cu)
The electrical resistance of the second layer 12 made of aluminum or aluminum (Al) can be kept low.

From the above, in the superconducting magnet device 101 of the first embodiment, even when the coil is excited or demagnetized, an eddy current is generated in the inner tank 2 or the second layer 12. Generation can be prevented, and heat generation in the inner tank 2 can be reduced.

(2) Second Embodiment The present invention can be realized by other configurations. next,
Another embodiment of the present invention will be described. FIG. 2 is a view showing a configuration of an inner tank in a second embodiment of the superconducting magnet device according to the present invention, wherein FIG. 2 (A) is an overall perspective view, and FIG. 2 (B) is an enlarged cross section of a discontinuous portion. The figures are shown respectively. The difference between the superconducting magnet device 102 of the second embodiment and the superconducting magnet device 101 of the first embodiment is that the superconducting magnet device 102 has a discontinuous portion 23 different from that of the first embodiment. Therefore, the description is omitted. In FIG. 2, portions denoted by the same reference numerals as those in FIG. 1 indicate the same components as those in FIG. 1.

As shown in FIG. 2, the discontinuous portion 23 of the superconducting magnet device 102 of the second embodiment is formed by filling the space of the discontinuous portion 13 of the first embodiment with an electrically insulating material. ing. The electrically insulating material to be filled is the first layer 1
The same material as that used in 1 or another electrically insulating material may be used. The electrical insulating material used for the discontinuous portion 23 is not limited to being formed in a layered form and may be of any shape, as long as it can be filled.

With the above configuration, the superconducting magnet device 102 of the second embodiment has the same advantages as those of the first embodiment.

(3) Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. The superconducting magnet device 103 of the third embodiment is different from the superconducting magnet devices 101, 1 of the first and second embodiments described above.
The difference from 02 is that it has a different first layer 31. The configuration and operation of the other components are the same as those in the first and second embodiments, and therefore description thereof is omitted. Note that FIG.
1, the same reference numerals as in FIGS. 1 and 2 denote the same components as in FIGS. 1 and 2.

As shown in FIG. 3, this third embodiment is
The method for forming the first layer 31 is characterized in that the first layer 31 is formed of a fiber made of an electrically insulating material, a string-shaped member made of the fiber, a woven fabric made of the fiber, and a non-woven fabric made of the fiber. The fiber member including the member is formed in a tape shape or a band shape, and is formed by being wound around the outer surface of the inner tank 2. In this case, the tape-shaped electrically insulating material 31 is circulated around the inner vessel pipe axis (the direction of the inner vessel pipe rotation axis).
Then, it is wound around the outer surface of the inner tank in a spiral manner.

According to the above, the first layer 31, which is an electrically insulating layer, can be formed easily and reliably. Further, the superconducting magnet device 103 of the third embodiment includes first, second,
It has the same advantages as the embodiment.

The present invention is not limited to the above embodiments. Each of the above embodiments is merely an example, and has substantially the same configuration as the technical idea described in the claims of the present invention, and those having the same functions and effects are:
Anything is included in the technical scope of the present invention.

For example, in each of the above embodiments, an example was described in which two discontinuous portions were provided in the second layer.
The present invention is not limited to this, and the number of discontinuous portions may be at least one, and may be one or three or more.

In each of the above embodiments, the inner tank 2
As an example, the shape of a closed circular race track is shown as an example, but the present invention is not limited to this.
An inner tank having another configuration, for example, a circular closed ring or an elliptical closed ring may be used.

[0045]

As described above, according to the present invention,
A first layer made of an electrically insulating material is provided on the outer surface of the inner tank of the superconducting magnet device, and a second layer made of a low-resistance material having a low electric resistance is provided on the first layer. The provision of at least one discontinuous portion that divides the second layer in the direction of the tank tube axis has the following advantages.

A) Since eddy current due to magnetic field fluctuation during excitation and demagnetization can be reduced, refrigerant evaporation can be reduced and the load on the refrigerator can be reduced.

B) By increasing the sweep speed at the time of excitation and demagnetization, the work time of excitation and demagnetization can be shortened, and heat can be prevented from entering the inner tank from the power lead. Machine load can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an inner tank in a first embodiment of a superconducting magnet device according to the present invention, FIG. 1 (A) is an overall perspective view, and FIG. 1 (B) is an enlarged cross section of a discontinuous portion. The figures are shown respectively.

FIG. 2 is a view showing a configuration of an inner tank in a second embodiment of the superconducting magnet device according to the present invention, FIG. 2 (A) is an overall perspective view, and FIG. 2 (B) is an enlarged cross section of a discontinuous portion. The figures are shown respectively.

FIG. 3 is a diagram illustrating an example of a method for forming an electrical insulating layer in FIGS. 1 and 2;

FIG. 4 is a partially cutaway perspective view showing a configuration of an example of a first conventional superconducting magnet device.

FIG. 5 is a partially cutaway perspective view showing a configuration of an inner tank and a coil in a first conventional superconducting magnet device.

6A and 6B are diagrams showing a relationship between an outer tub, an inner tub, and a coil in a second conventional superconducting magnet device, wherein FIG. 6A is a partially cutaway perspective view, and FIG. , Respectively.

[Description of Signs] 1 outer tank 2 inner tank 2a load support member 2b spacer 3 radiation shield member 4 refrigerator 4a liquid helium tank 5 power lead 6 coil 7 permanent current switch 10 insulated inner tank 11 first layer 12 second layer DESCRIPTION OF SYMBOLS 13 Discontinuous part 20 Insulated inner tank 23 Discontinuous part 30 Insulated inner tank 31 Fiber member 50 Composite inner tank 52 Low resistance member 101-103, 200 Superconducting magnet device A1 Inner tank tube axis A2 Inner tank tube rotation axis

Claims (9)

[Claims] A coil formed of a superconducting material and formed in a closed ring; an inner tank formed of a metal material and formed as a closed ring as a whole and accommodating the coil together with a refrigerant; A superconducting magnet device having an outer tank housed in a heat-insulated state, comprising: a first layer made of an electrically insulating material and formed on an outer surface of the inner tank; and a first layer made of a low-resistance material having a low electric resistance value. A second layer formed on the second layer, wherein the second layer has at least one discontinuous portion that divides the second layer in a direction of an inner tank tube axis that is an axis of the pipe in the inner tank. A superconducting magnet device, which is provided. 2. The superconducting magnet device according to claim 1, wherein the discontinuous portion of the second layer is formed by removing the second layer so as to orbit around the inner tube axis. A superconducting magnet device characterized by the above-mentioned. 3. The superconducting magnet device according to claim 2, wherein the discontinuous portion is filled with an electrically insulating material. 4. The superconducting magnet device according to claim 1, wherein the first layer is an electrically insulating material wound around the outer surface of the inner tank so as to spiral around the inner tube axis. A superconducting magnet device characterized by being formed of a fiber member made of: 5. The superconducting magnet device according to claim 1, wherein the electrically insulating material is a heat-resistant material containing silicon carbide, a ceramic material containing silicon dioxide, and an aramid fiber. A superconducting magnet device comprising a conductive organic material. 6. The superconducting magnet device according to claim 4, wherein the fiber member is a fiber, a string-shaped member made of the fiber,
A superconducting magnet device comprising: a woven fabric member made of the fiber; and a nonwoven fabric member made of the fiber. 7. The superconducting magnet device according to claim 1, wherein the electrically insulating material is a good thermal conductor. 8. The superconducting magnet device according to claim 1, wherein the closed ring includes a circle, an ellipse, and a racetrack shape. 9. A closed annular coil made of a superconducting material, an inner tank made of a metallic material, formed as a tube and forming a closed ring as a whole, and accommodating the coil together with a refrigerant; A first layer made of an electrically insulating material is formed on an outer surface of the inner tank of the superconducting magnet device having an outer tank housed in a state, and a second layer made of a low-resistance material having a low electric resistance is formed on the first layer. A second layer is formed on a layer, and the second layer is divided in a direction of an inner tank pipe axis which is an axis of the pipe in the inner tank to provide at least one discontinuous portion, and the inner tank pipe in the second layer is provided. An eddy current suppressing method in a superconducting magnet device, characterized by preventing generation of an eddy current which is a current circulating in an axial direction.