JPH0715844B2 - Superconducting coil - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superconducting coil which uses a compound-based superconducting wire and is heat-treated at a high temperature after winding to produce a superconducting substance,
In particular, it relates to a cooling arrangement.

[Prior Art] A conventional superconducting coil is disclosed in, for example, Japanese Patent Application Laid-Open No. 55-160406, and its schematic structure is shown in FIGS.
Shown in the figure. In each of these figures, (1) is a superconducting coil, (2) is a compound superconducting wire, and this superconducting wire (2) is a winding part (4) wound around a coil bobbin (3).
Are configured. The gap between the superconducting wires (2) of the winding portion (4) is impregnated with a thermosetting organic resin (6) in which a metal compound (5) is dispersed and mixed. The superconducting wire (2) is usually provided with insulation (7), and the material for the insulation (7) is heat-resistant glass fiber, glass cloth, or the like.

Next, the operation will be described. The superconducting coil (1) is usually immersed and cooled in liquid helium (not shown),
When the superconducting wire (2) is below its critical temperature, its electric resistance becomes zero and a large current can flow. Therefore, the superconducting coil (1) can generate a high magnetic field and is used as a high magnetic field generator. In particular, compound-based superconducting wires (2) such as NbSn (niobium tin tin) have good high magnetic field characteristics and
(Tesla) Used as superconducting coil wire for high magnetic field generation.

However, various instabilities exist in the superconducting coil (1), and the superconducting state may be partially broken and the normal conducting state may occur. In such a case, the superconducting coil (1)
Since a large current is flowing through it, a large amount of Juule's heat is generated even if a small amount of resistance is generated, and as a result, the temperature rises and the non-superconducting part increases, and the part where the resistance increases further expands. Eventually, a phenomenon called quenching in which the superconducting state is destroyed by avalanche in the entire coil is caused, and in some cases, coil burnout may occur.

Causes of instability of the superconducting coil (1) include movement of the superconducting wire (2) due to electromagnetic force, release of thermal residual strain when the superconducting coil (1) is cooled from room temperature to extremely low temperature, and the like. . Therefore, it is a technical issue in manufacturing the superconducting coil (1) to have a strong winding structure in which the superconducting wire (2) does not move and to prevent uneven thermal distribution in the coil. is there. With a metal-based superconducting wire, it is possible to fabricate a superconducting coil having a strong winding portion with no movement of the superconducting wire by performing the winding while applying tension during winding. This manufacturing method is possible because a metal-based superconducting wire does not require high-temperature heat treatment for producing a superconducting material.

On the other hand, the compound superconducting wire (2) has good high magnetic field characteristics,
It is a superconducting material suitable as a wire for high magnetic field coils.
Since it is a compound system, it is fragile and has the drawback that its superconducting properties deteriorate due to mechanical strain. For small-sized superconducting coils with a small winding diameter, the so-called wind and reactor (WI
ND AND REACT) method is adopted. That is, the superconducting coil (1) is manufactured by a process of winding a coil with an unreacted superconducting wire and then performing high temperature heat treatment to generate a superconducting substance. About 700 ℃ for NbSn superconducting wire, which is a typical example of compound system
Therefore, heat treatment for several tens of hours is required. Therefore, even if the initial tension is applied and the coil winding is performed, it is difficult to keep the tension remaining until after the heat treatment.

Therefore, in a superconducting coil (1) using a compound-based superconducting wire (2) that requires heat treatment after winding, the superconducting wire (2) is provided with an insulation (7) made of, for example, glass fiber having good heat resistance. After the heat treatment at a high temperature, a thermosetting organic resin (6) is impregnated and hardened to strengthen the winding, and the superconducting wire (2) is prevented from moving.

Further, in order to prevent thermal non-uniformity and thermal strain from occurring when the superconducting coil (1) is cooled from room temperature to extremely low temperature, a metallic compound (5) having good thermal conductivity is dispersed and mixed. There is also.

[Problems to be Solved by the Invention] However, the above-described conventional compound-based superconducting coil has a drawback that its use is limited to those that generate a DC magnetic field and cannot be applied to a coil that changes in a pulsed or AC magnetic field. There is. That is, in a coil that changes a magnetic field in a pulsed or AC manner, a so-called AC loss such as a hysteresis loss proportional to the magnetic field change rate, a coupling loss proportional to the square of the magnetic field change rate, and an eddy current loss occurs in the superconducting wire (2). . These electrical losses eventually result in thermal losses, that is, heat generation, which raises the temperature of the superconducting wire (2). The heat generated in these superconducting wires (2) is conducted across the superconducting wire portion and the resin portion in the impregnated coil structure shown in the above-mentioned conventional example, reaches outside the winding, and is removed by cooling with a coolant such as liquid helium. To be done. At this time, the superconducting wire portion and the resin portion have a thermal resistance. Therefore, in the superconducting coil (1) having a large magnetic field changing speed and a large amount of heat generation, the amount of heat generated is larger than the amount of heat removed by conduction, and the temperature inside the coil rises, leading to superconducting breakdown.

In order to solve such a problem, when the superconducting wire is made of metal, it is not necessary to heat-treat it at a high temperature. Therefore, as shown in FIGS. 6 and 7, the winding is made of, for example, glass fiber reinforced plastic (GFRP). The liquid helium in the gap between the spacers (8) can cool and remove the heat generated by the AC loss. At this time, a glass cloth, a formal coating or the like is used as the insulation (10) of the metallic superconducting wire (9). In addition, it is possible to wind while applying tension and maintain the tension at the time of winding until the end of coil production, but the winding structure is also strong and the superconducting wire (9) moves due to electromagnetic force. I won't let you.

However, in the case of the superconducting coil (1) using the compound superconducting wire (2), high temperature heat treatment is involved,
It was difficult to take such measures in an inexpensive way.
For example, ceramics has heat resistance and can be used as a cooling spacer for a superconducting coil (1) using a compound-based superconducting wire (2) that is subjected to high temperature heat treatment, but the material is expensive and machining is difficult. The superconducting coil (1) has the drawback of being expensive. Moreover, even if ceramics is used as a cooling spacer, the ceramics have mechanically brittle characteristics. Furthermore, high-temperature heat treatment makes the brittleness more remarkable, and the superconductivity is mechanically strong against electromagnetic force. It has the drawback that the coil (1) cannot be manufactured.

The present invention has been made to solve the above problems, and an object thereof is to obtain an inexpensive and mechanically strong superconducting coil.

[Means for Solving the Problem] The superconducting coil according to the present invention is arranged between winding layers,
After the cooling channel spacer is formed by inserting a metal piece inside the insulating material formed by knitting heat-resistant fiber into a bag, and the cooling channel spacer is arranged between the winding layers and wound. A high temperature heat treatment for producing a superconducting substance is performed, and an epoxy resin to be impregnated thereafter is provided.

[Operation] In the superconducting coil according to the present invention, a cooling channel spacer formed by inserting a metal piece inside an insulating material formed by knitting heat-resistant fibers in a bag shape is arranged between winding layers. After that, a high temperature heat treatment for producing a superconducting material is performed, and then an epoxy resin is impregnated to manufacture a mechanically strong superconducting coil.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In each of these figures, (1) to (7) have the same configuration as the conventional device described above. (11) is a cooling channel spacer for forming a cooling channel on a superconducting coil (1) formed by winding a compound-based superconducting wire (2) by the wind-and-react method, and is arranged between winding layers. . (12) is an insulating material formed by knitting heat-resistant fibers, for example, ceramics-based alumina fibers in a bag shape, (13)
Is a metal piece made of, for example, stainless steel inserted inside the insulating material (12) in order to withstand high temperature heat treatment and to make the spacer strong. These insulation materials (12), metal pieces (1
The spacer (11) for the cooling channel is composed of 3). (14) is an epoxy resin that is impregnated after the spacer (11) is placed between the winding layers and wound, and then subjected to high-temperature heat treatment for producing a superconducting substance.

Next, the operation will be described. A spacer (11) structure as shown in FIG. 1, a spacer (11) in which a metal piece (13) such as stainless steel is inserted inside an insulating material (12) formed by knitting a ceramic fiber into a bag shape. ) Structure, the insulating material (12) formed by knitting ceramic fibers in a bag shape can sufficiently maintain insulation between layers of the superconducting coil (1) even after high-temperature heat treatment for producing a superconducting substance. A cooling channel for liquid helium can be constructed in the winding part (4) of the superconducting coil (1). In addition, the insulating material (1
2) A piece of metal such as stainless steel (1
Due to 3), the strength of the spacer (11) does not deteriorate even after high temperature heat treatment. Furthermore, by impregnating the epoxy resin (14) after the high temperature heat treatment, the epoxy resin (14) is impregnated inside and in the insulation (7) of the superconducting wire (2) and the insulating material (12) of the spacer (11). Since the superconducting wire (2) is firmly fixed to the spacer (11), the winding part (4) has a strong coil structure, and the superconducting wire (2) has an electrode force.
Can be prevented from moving. Further, even if an AC loss occurs due to a pulsed or AC magnetic field change, that is, even if there is a thermal loss, the superconducting state can be stably maintained without raising the temperature of the superconducting wire (2).

In the above examples, the case where ceramic-based fibers are used as the insulating material (12) constituting the spacer (11) is described. However, the material strength after high temperature heat treatment is slightly inferior to that of ceramics, but the heat resistance is high. It may be used as an insulating material (12) formed by knitting a certain glass fiber into a bag shape, and has the same effect as in the above-mentioned embodiment.

Further, in the above-mentioned embodiment, the case where the spacer (11) is inserted in each layer of the windings has been described, but when the amount of heat generation is small, it is also possible to arrange the layers in each of a plurality of layers. When the plurality of superconducting wires (2) are arranged, the space factor of the superconducting wire (2) increases and the superconducting coil (1) becomes compact.

Further, in the above-mentioned embodiment, the case where the insulating material (12) is formed by knitting the ceramic fiber or the glass fiber into a bag shape is described, but it goes without saying that other heat resistant fiber may be used.

[Effects of the Invention] As described above, according to the present invention, the cooling is formed by inserting the metal piece into the inside of the insulating material that is arranged between the winding layers and is formed by knitting the heat-resistant fiber into a bag shape. Since a spacer for a channel is provided and the spacer for a cooling channel is placed between winding layers and wound, high temperature heat treatment for producing a superconducting substance is performed, and then an epoxy resin is impregnated so that the machine is inexpensive. It is possible to obtain a superconducting coil that is relatively strong.

[Brief description of drawings]

FIG. 1 is a perspective view showing a spacer for a cooling channel of a superconducting coil according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a superconducting coil according to an embodiment of the present invention.
Fig. 2 is an enlarged view of part A in Fig. 2, Fig. 4 is a sectional view showing a conventional superconducting coil, Fig. 5 is an enlarged view of part B in Fig. 4 and Fig. 6 is a sectional view showing another conventional superconducting coil. FIG. 7 and FIG. 7 are enlarged views of part C in FIG. In the figure, (1) is a superconducting coil, (2) is a superconducting wire, (11) is a spacer, (12) is an insulating material, (13) is a metal piece, and (14) is an epoxy resin. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kiyoshi Hasegawa 3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture 3-22 Kansai Electric Power Co., Inc. (72) Inventor Katsuyoshi Toyota 1-chome Wadazaki-cho, Hyogo-ku, Kobe-shi, Hyogo 1-2 Mitsubishi Electric Co., Ltd. Kobe Works (72) Inventor Takashi Sasaki 1-2 1-2 Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Electric Co., Ltd. Kobe Works

Claims (1)

[Claims] 1. A superconducting coil which uses a compound-based superconducting wire and is heat-treated at a high temperature after winding to produce a superconducting material. An insulating material which is arranged between winding layers and formed by knitting heat-resistant fibers into a bag shape. After the spacer for cooling channel configured by inserting a metal piece into the inside of the coil and the spacer for cooling channel are arranged and wound between the winding layers, high temperature heat treatment for superconducting substance generation is performed, and then impregnation is performed. A superconducting coil comprising an epoxy resin as described above.