JPH09139309A - Superconductive coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress frictional heat generated by the friction against a spool when a superconductive wire is moved by electromagnetic force during current- carrying and prevent the generation of quenching by baking a baking film consisting of a material with a small friction coefficient on the inner side surface of flanges and on the outer peripheral surface of a barrel part where the spool will be in contact with a wound superconductive wire. SOLUTION: This superconductive coil is provided with a stainless steel spool 1 whose pipe-shaped barrel part 1a has flanges 1b at the both ends, and a winding part 3 consisting of copper stabilized NbTi superconductive wire 2 wound about the outer periphery of the barrel part 1a of this spool 1 between the flanges 1b. Further, the spool 1 has a baking film 4 of 500μm in thickness consisting of teflon baked on the inner side surface of both flanges 1b and on the outer peripheral surface of the barrel part 1a. Thus, the frictional force against the superconductive wire is made smaller than that in the case where the superconductive wire is directly in contact with the stainless steel, so that the generation of frictional heat can be suppressed and quenching can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting coil excited at an extremely low temperature, and more particularly to a superconducting coil formed by winding a superconducting wire around a cylindrical bobbin in a solenoid shape.

[0002]

2. Description of the Related Art A solenoid type superconducting coil is a cylindrical bobbin having flanges (1b) at both ends as shown in (a) of FIG. 3 which is an explanatory sectional view of the basic structure. (1)
The superconducting wire (2) is wound around the outer circumference of the body (1a) of the superconducting wire like a solenoid.It is cooled to a cryogenic temperature below the critical temperature of the superconducting wire (2) by liquid helium, etc. As a result, a high magnetic field is generated.

By the way, when this superconducting coil is excited by energization, an electromagnetic force acts on the wound superconducting wire (2), and as shown by the arrow in FIG. An electromagnetic force that compresses the line portion (3) in the axial direction and an electromagnetic force that spreads it in the radial direction act. Then, when the superconducting wire (2) moves due to the electromagnetic force, heat is generated in that part, and the entire winding part (3) changes to the normal conducting state at a current value lower than the critical current that can flow in the superconducting wire (2). A phenomenon called "quenching" occurs,
The occurrence of this quench is due to the superconducting wire accompanying the electromagnetic force described above.
The main cause is considered to be heat generation due to friction between (2) and the bobbin (1).

Conventionally, as a means for preventing heat generation due to such friction, a method of suppressing the movement of the superconducting wire by electromagnetic force by winding the superconducting wire with a large tension when winding the superconducting wire on the bobbin (FIG. 4). As shown in, between the body (11a) of the reel (11) and the superconducting wire (12), a sliding material (13) having a small friction coefficient, for example, a method of inserting a polyimide-based or Teflon-based film ( JP-A-63-283105) is adopted.

[0005]

However, the above-mentioned conventional method has the following problems. That is, like the former method, when the superconducting wire is wound with a large tension, it is necessary to increase the wall thickness of the winding frame so that the tension does not buckle, and a large tension applying device Will be needed. Further, in the latter method, the film wound around the body of the reel may be broken by the pressure when the superconducting wire is wound, and moreover, in the inner side surface portion that contacts the superconducting wires of both flanges of the reel. It is necessary to process the film into a ring shape, which complicates the construction. Furthermore, due to the difference in heat shrinkage between the reel and the film, the film may be displaced or partially torn during cooling during operation.

The present invention has been made in order to solve the above problems, and it is possible to wind a superconducting wire with a large tension, which requires a thicker wall and a special tension applying device. It is an object of the present invention to provide a superconducting coil that can prevent the occurrence of quenching without and stably, suppressing the generation of frictional heat between the superconducting wire and the winding frame due to the movement of the superconducting wire due to the electromagnetic force during energization.

[0007]

In order to achieve the above object, the present invention has the following arrangement. That is, the superconducting coil according to the present invention is a superconducting coil formed by winding a superconducting wire in a solenoid shape around the outer periphery of a cylindrical winding frame having flanges at both ends, wherein the winding frame is a wound superconducting coil. It is characterized in that it has a baking coating formed by baking a material having a small friction coefficient on the inner surface of the flange and the outer peripheral surface of the body which are in contact with the wire.

Further, the formation area of the baking coating of the reel is
It may be the entire inner surface of both flanges and the outer peripheral surface of the vicinity of both flanges except the axial center of the body. Further, the baking coating of the winding frame may be made of a Teflon-based material, or may be made of a fluororesin.

In the superconducting coil of the present invention, since the bobbin around which the superconducting wire is wound has the seizure coating of a material having a small friction coefficient on the inner surface of the flange and the outer peripheral surface of the body which are in contact with the superconducting wire. The friction coefficient between the superconducting wire and the bobbin becomes small, and the generation of frictional heat between the superconducting wire and the bobbin due to the movement of the superconducting wire due to the electromagnetic force during energization can be suppressed to prevent quenching. That is, if the surface pressure between the superconducting wire and the bobbin is P and the friction coefficient between them is μ, the frictional force is represented by μP, and the amount of heat generated by friction is proportional to this frictional force.
If the friction coefficient μ is small, heat generation due to frictional force can be suppressed and quenching can be prevented. In addition, the baking coating on the reel can further increase the bonding strength to the reel surface as compared with the film fixed with an adhesive or the like of the above-mentioned prior art, which can cause misalignment during cooling during operation. It is possible to stably reduce the frictional force between the superconducting wires in contact with each other without causing partial breakage, and effectively prevent quenching.

On the other hand, in the superconducting coil formed by winding the superconducting wire around the outer circumference of the body of the bobbin in a solenoid shape, as shown in FIG.
As shown in Fig. (b), the electromagnetic force in the axial center part of the coil acts only in the radial direction, and especially in a large superconducting coil, the electromagnetic force in the axial direction hardly acts in the axial center part. . Therefore, in the case of a relatively large superconducting coil, the region where the seizure film on the winding frame is formed is the entire inner surface of both flanges and the outer peripheral surface in the vicinity of both flanges except the axially central part of the body, that is, in the axial direction. Even if the baking film in the central portion is omitted, it is possible to suppress the generation of frictional heat between the winding frame and the superconducting wire due to the movement of the superconducting wire at the time of energization to prevent quenching.

On the other hand, the surface of the superconducting wire wound around the bobbin is made of copper. For example, in the case of a stainless steel bobbin, the friction coefficient μ between the stainless steel and the copper of the bobbin is Is 0.21, whereas the friction coefficient μ between Teflon and copper is 0.11, and in the reel having the baking coating made of the Teflon-based material, compared with the winding frame having no baking coating,
The frictional force with the superconducting wire is significantly reduced. Therefore,
In a superconducting coil in which the baking coating of the winding frame is made of Teflon-based material, the frictional force between the winding frame and the superconducting wire is small, and as a result, the frictional heat can be suppressed to a low level, thus effectively preventing quenching. can do. Also, PT
Fluorine-based resins such as FE and EFP have a very small coefficient of friction with copper. Therefore, in a superconducting coil in which the baking coating of the winding frame is made of fluorine-based resin, the same effect as above can be obtained.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. [FIG. 1] is a front sectional view showing a schematic configuration of one embodiment of a superconducting coil according to the present invention.

The superconducting coil of this embodiment shown in FIG. 1 comprises a stainless steel reel (1) provided with flanges (1b) at both ends of a tubular body (1a), and this reel. Flange (1) (1
A coil portion (3) composed of a copper-stabilized NbTi superconducting wire (2) wound in a solenoid shape is provided around the outer periphery of the body portion (1a) between b). In addition, the reel (1) has a 500 μm thick baking film (4) made by baking Teflon on the inner surface of both flanges (1b) in contact with the superconducting wire (2) and the outer peripheral surface of the body (1a). I will do it.

In the superconducting coil of this embodiment having the above structure,
The coefficient of friction μ between the stainless steel of the reel (1) and the copper on the surface of the superconducting wire (2) is 0.21, while the inner surface of the flange (1b) of the reel (1b) and the body ( 1a) The friction coefficient μ between the Teflon on the outer surface of the baked film (4) and the copper on the surface of the superconducting wire (2) is
0.11 and the frictional force between the superconducting wire (2) and the superconducting wire (2) is significantly smaller than that when the superconducting wire (2) directly contacts the stainless steel of the bobbin (1). Therefore, the quenching can be prevented by suppressing the generation of frictional heat between the superconducting wire (2) and the reel (1) caused by the electromagnetic force during energization.

Further, the Teflon baking film (4) baked on the reel (1) has more bonding strength to the reel (1) surface than the film fixed with an adhesive or the like of the prior art. The superconducting wire that is in contact with the superconducting wire can be increased without causing misalignment or partial breakage during cooling during operation.
(2) The frictional force between and can be stably reduced, and quenching can be effectively prevented.

In the above embodiment, the case where a Teflon baked film is formed on all of the inner surface of both flanges and the outer peripheral surface of the body of the winding frame which is in contact with the superconducting wire has been shown, but particularly in the case of a relatively large superconducting coil. In the central portion of the coil in the axial direction, almost no electromagnetic force acts in the axial direction, so that it is possible to omit the baking coating in the central portion of the reel body in the axial direction. That is, for example, in a superconducting coil in which a NbTi superconducting wire with a diameter of 1.6 mm is wound 3984 times around a bobbin with an outer diameter of 150 mm and a length of 800 mm, the length of the central portion of the coil in the axial direction is 450
The axial electromagnetic force in the mm region is less than 5% of its maximum value. Therefore, as shown in FIG. 2, even if the baking film on the axial center portion of the barrel portion of the winding frame is omitted, the same effect as in the above embodiment can be obtained.

FIG. 2 is a front sectional view showing a schematic configuration of another embodiment of the superconducting coil according to the present invention. The superconducting coil of the present embodiment is the same as the embodiment shown in FIG. 1 except that the forming region of the baking coating of the winding frame is different. The same reference numerals are given, the description thereof is omitted, and only the differences will be summarized and described.

In the superconducting coil of this embodiment shown in FIG. 2, the formation area of the baking coating (4) of the reel (1) is the reel (1).
The entire inner surface of both flanges (1b) and the outer peripheral surface of the vicinity of both flanges (1b) excluding the axial center portion of the body portion (1a).

In the superconducting coil of this embodiment having the above structure,
Due to the above-mentioned reasons, even if the baking film (4) at the axial center portion of the body (1a) of the reel (1) is omitted, the same effect as in the above-mentioned embodiment can be obtained, and It can be applied to a large superconducting coil to reduce its manufacturing cost and improve its economic efficiency.

In the above embodiments, the case in which the material of the bobbin is stainless steel has been described as an example, but the present invention is not limited to this and is generally used as a bobbin of a superconducting coil. Materials that can be used include stainless steel, metal materials such as aluminum alloy and copper, or GF
A non-metal material such as RP can be used. Further, as the baking film of the winding frame, not only Teflon-based material but also a fluorine-containing material such as PTFE or EFP can be used as long as the coefficient of friction with copper is small and the baking treatment can be performed easily and surely. It goes without saying that the same effect can be obtained by using a resin.

In the above embodiments, the case of a superconducting coil using a copper-stabilized NbTi superconducting wire has been described as an example, but the present invention is not limited to the copper-stabilizing NbTi superconducting wire. It can be applied to superconducting coils using all kinds of superconducting wires.

[0022]

As described above, according to the superconducting coil of the present invention, it is possible to wind the superconducting wire with a large tension which requires a thicker winding frame and a special tension applying device. Without and stable, it is possible to suppress the occurrence of quenching by suppressing the generation of frictional heat between the superconducting wire due to the movement of the superconducting wire due to the electromagnetic force at the time of energization, thereby improving the stability of the superconducting coil. You can

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a schematic configuration of one embodiment of a superconducting coil according to the present invention.

FIG. 2 is a front sectional view showing a schematic configuration of another embodiment of the superconducting coil according to the present invention.

FIG. 3 is an explanatory sectional view of a basic configuration of a conventional solenoid type superconducting coil.

FIG. 4 is a front sectional view showing a schematic configuration of a conventional superconducting coil.

[Explanation of symbols]

 (1)-Reel (1a)-Body (1b)-Flange (2)-Superconducting wire (3)-Winding part. (4) --Baked film

Claims (4)

[Claims] 1. A superconducting coil formed by winding a superconducting wire in the form of a solenoid around the outer periphery of a cylindrical winding frame having flanges at both ends, wherein the winding frame is inside the flange in contact with the wound superconducting wire. A superconducting coil having a baking coating formed by baking a material having a small friction coefficient on a side surface and an outer peripheral surface of a body portion. 2. The superconducting coil according to claim 1, wherein the seizure film forming region of the winding frame is the entire outer surface of the inner surface of both flanges and the outer peripheral surface of the body in the vicinity of both flanges except the axially central portion. . 3. The superconducting coil according to claim 1, wherein the baking coating of the winding frame is made of a Teflon-based material. 4. The superconducting coil according to claim 1, wherein the baking coating of the winding frame is made of a fluororesin.