High-temperature superconducting coil and method of manufacturing thereof

Abstract: A high temperature superconducting coil includes an oxide superconducting wire 2 wound in a coil, a container 3 for accommodating the superconducting wire 2, and a filling resin portion 4 for fixing the superconducting wire 2 in the container 3 by being injected into the container 3 and then cured.

Description: The present invention relates to a high temperature superconducting coil where an oxide superconducting wire is wound in a coil and also relates to a method of manufacturing thereof. From Patent Abstracts of Japan, Vol. 13, No. 97 (E-723)(3445) March 7, 1989, JP-A-63-272017, it is known to form a superconducting coil by using a spraying process of fine particles of superconductive ceramic. A filament substance is wound in the form of solenoid at an outer circumference of a cylindrical spool and fine particles consisting of a ceramic superconductor are flame-sprayed at the outer circumference of the spool. After the filament substance is removed and the flame-sprayed fine particles at the outer circumference of the spool is sintered by heat treatment, an insulator is filled at a part where the filament substance is removed. For example, the fine particles of the superconductive ceramic consisting of Y-Ba-Cu-O and the like are flame-sprayed and a coil obtained by removing a spacer out of the spool is treated in the air and then, a solenoid coil is formed by sintering the fine particles again. After that, an epoxy resin is filled in gaps between the outer circumference of the coil and a cylindrical container. Then, the epoxy resin is set so as to form a hardened layer. Then a magnet is formed by providing a stainless reinforcing layer. From Patent Abstracts of Japan, Vol. 13, No. 352 (E-801)(3700) August 8, 1989, JP-A-1-110 710 it is known to wind an oxide superconductor wire in coil-form. A complex is formed by filling into a metal tube at least one of the raw material powder of an oxide superconducting body or superconducting powder or the molded body of these powder. Then, a diameter-reducing work is conducted on the complex, and a wire material, equipped with the metal covered layer consisting of the metal tube and the core wire consisting of powder or a molded body, is formed. Then, after the wire material has been wound in coil form, the core wire is exposed by removing the metal coated layer from the wire material. Then, after heat-treatment has been conducted on the core wire, a resin layer is formed covering the coil-formed core wire, and a cylindrical superconducting coil is formed. As the material for the above-mentioned resin layer, the highly insulative synthetic resin such as epoxy resin, silicone resin, vinyl chloride resin, polyethylene and the like, and the coating material and the like to be used for enamel wire is used. A high temperature superconductive material known as a ceramics based superconductor is under study to be used as a thin tape type wire by applying plastic working to a high temperature superconductor while being metal-coated (see for example EP-A-0 282 286). The combination of such plastic working and thermal treatment can result in obtaining a tape type oxide superconducting wire having high critical density. The application of such a tape type oxide superconducting wire is now being considered to bus bar conductors, cable conductors, coils, etc. However, such an oxide superconducting wire had a characteristic problem of low resistance to mechanical strain. Therefore, a coil formed of an oxide superconducting wire as known from EP-A-0 282 286 had a problem of degraded performance caused by thermal strain during a thermal heat cycle and mechanical strain by the electromagnetic force of the coil itself. SUMMARY OF THE INVENTION An object of the present invention is to provide a high temperature superconducting coil showing high critical density and that can have thermal strain and mechanical strain reduced. Another object of the present invention is to provide a method of manufacturing such a high temperature superconducting coil. These objects are achieved by a superconducting coil as defined in claim 1 and with a method for manufacturing same as defined in claim 4. A high temperature superconducting coil according to the present invention includes: a metal-sheathed oxide superconducting wire wound in a coil; a container for accommodating the superconducting wire; and a filling resin portion for fixing the superconducting wire within the container by being injected into the container and then cured. In the present invention, the container accommodating the superconducting wire is preferably a non-magnetic material such as stainless and FRP (Fiber Reinforced Plastics). The resin injected into the container is preferably an organic based material such as an epoxy based resin. Also, the resin injected into the container is preferably cured without any additional treatment. The filling resin portion preferably has a thermal expansion coefficient substantially identical to that of the container or the metal coating of the oxide superconducting wire. Also, one having great mechanical strain at the time of low temperature is preferable. A method of manufacturing a high temperature superconducting coil according to the present invention comprises the steps of: winding a metal-sheathed oxide superconducting wire in a coil, accommodating said wound superconducting wire in a container, and injecting a filling resin into said container and curing the resin for fixing said superconducting wire in the container. The high temperature superconducting coil according to the present invention can have the behavior caused by difference in temperature of the wire suppressed at the time of the heat cycle to reduce mechanical strain, since the oxide superconducting wire wound in a coil is fixed by a resin filling portion of epoxy based resin. Furthermore, mechanical reinforcement is established even towards the electromagnetic force of the coil itself to prevent degradation of the coil performance, by being accommodated into a container of non-ferrous metal such as stainless, followed by injection, impregnation and curing of an epoxy type resin and the like. Therefore, the high temperature superconducting coil according to the present invention can be applied to super high magnetic field magnetic in liquid helium and the like. It is known that an oxide superconducting wire is superior to the current alloy based and compound based superconducting wires in high magnetic field. The oxide superconducting wire can be used in magnetic coils or inner coils for superhigh magnetic fields that cannot be achieved with alloy based or compound based superconducting wires. The foregoing and the objects, features aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of an embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a sectional view showing an embodiment of the present invention. Referring to Fig. 1, an oxide superconducting wire 2 is wound in a coil around a stainless bobbin 1. The coiled oxide superconducting wire 2, as well as stainless bobbin 1, is accommodated in stainless container 3. After being accommodated in stainless container 3, an epoxy based adhesive 4 is injected into stainless container 3 and then cured. Thus, epoxy based adhesive 4 becomes the filling resin portion. A double pancake coil was created placing ten layers of silver-sheathed Bi based high temperature superconducting wire of a thickness of 0.15mm, a width of 4mm, and a length of 2.7m. This double pancake coil was placed in a stainless container having a wall thickness of 3mm, where Stycast 2850FT (a product of Grace Japan Ltd.) is injected as the epoxy based adhesive to be completely cured. The performance was verified in liquid nitrogen, and the critical current Ic was 85A, and the maximum magnetic flux density Bm was 0,0876 tesla (876 gauss). This high temperature superconducting coil was dipped into liquid helium to which an external magnetic field was applied and measured. An external magnetic field having a magnetic flux density of 1 tesla - 6 tesla was applied to energize this superconducting coil. When an external magnetic field having a magnetic flux density of 6 tesla was applied, the high temperature superconducting wire had an Ic of 400A, and a Bm of 0,412 tesla (4120 gauss). The electromagnetic force was 164 kg/cm 2 . When the performance in liquid nitrogen was verified again afterwards, the Ic was 85A, the Bm was 0,0876 tesla (876 gauss), where no degradation in the coil performance was recognized. As a comparison example, a double pancake coil similar to that used in the above embodiment was created and dipped in liquid nitrogen, wherein the performance was verified. The critical current Ic was 70A, and the maximum magnetic flux density was 0,072 tesla (720 gauss). An external magnetic field was applied in liquid helium, and then measured. When an external magnetic field having a magnetic flux density of 6 tesla was applied, the high temperature superconducting coil had an Ic of 250A, and a Bm of 0,257 tesla (2570 gauss). The electromagnetic force at this time was 164 kg/cm 2 . When the performance was verified again in liquid nitrogen, as in the above embodiment, the Ic was 32A, the Bm was 0,0379 tesla (329 gauss), exhibiting degradation in coil performance. It is apparent from the above-described embodiment and the comparison example that a high temperature superconducting coil can be obtained according to the present invention without degradation in performance caused by mechanical strain by thermal heat cycle and electromagnetic force. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims: A high temperature superconducting coil comprising: a metal-sheathed oxide superconducting wire (2) wound as a coil, characterized by further comprising a container (3) for accommodating said superconducting wire (2), and a filling resin portion (4) for fixing said superconducting wire (2) in the container (3) by being injected into said container (3) and then cured. A high temperature superconducting coil recited in claim 1, wherein said container (3) ist formed of non-magnetic material. A high temperature superconducting coil recited in claim 1 or 2, wherein said filling resin portion (4) has a thermal expansion coefficient substantially identical to that of the container (3). A method of manufacturing a high temperature superconducting coil, comprising the step of winding a metal-sheathed oxide superconducting wire (2) in a coil, characterized by further comprising the steps of accommodating said wound superconducting wire (2) in a container (3), and injecting a filling resin (4) into said container (3) and curing the resin for fixing said superconducting wire (2) in the container (3).

Inventors: MASUDA TAKATO, MUKAI HIDEHITO, SATO KENICHI, SHIBUTA NOBUHIRO, MASUDA, TAKATO, MUKAI, HIDEHITO, SATO, KENICHI, SHIBUTA, NOBUHIRO, Masuda, Takato, c/o Osaka Works, MUKAI, HIDEHITO, C/O OSAKA WORKS, SATO, KENICHI, C/O OSAKA WORKS, SHIBUTA, NOBUHIRO, C/O OSAKA WORKS
Applicants: SUMITOMO ELECTRIC INDUSTRIES, SUMITOMO ELECTRIC INDUSTRIES, LIMITED
Application year: 1992
Main classification: H01F6
IPC codes: H01F6