Conductor suited for a coil of superconducting material.

The present invention relates an assimilable conductor to a winding made of superconducting material.

Discloses superconducting coils made with son made from ductile materials, niobium-titanium, for example. These windings consist of coils, which implies the ability to bend the son without creating discontinuities (fractures, cracks, ...) within them.

The discovery of new superconducting materials with high critical temperature, from 30 to 90 K instead of 8 to 15 K for the niobium-based alloys, allows to consider the realization of superconducting systems operating at the temperature of liquid nitrogen 77 K instead of 4.2 K to liquid helium. These new materials are compounds of ceramic type: The Ba Cu O, The Sr Cu O, Y Ba Cu O. Like any ceramic these materials have a brittle behavior, that is to say, their rupture is practically done without deformation. It is not easy to achieve son with these materials; Moreover, the deformation of such son without breaking the electrical continuity is very random.

The present invention is intended to make drivers, similar to the coils, non ductile superconducting material whose preparation is easier than known coils.

The present invention relates to a driver assimilable to a winding of a superconducting material, characterized in that it is made from a solid element of sintered superconducting oxide, with high critical temperature, the shape of said conductor being obtained by machining said solid element and constituting a self-supporting structure.

by oxide superconductor refers to a superconductor material consists of one or more oxidic phases.

According to a first embodiment, said solid element is in the form of a hollow cylinder, subsequently cut to form a solenoid.

According to a second embodiment, said solid element is in the form of a rectangular plate subsequently cut to form a flat coil.

In a third embodiment, said solid element in the form of two hollow half-cylinders later be cut into two parts of a dipole.

These examples are for illustrative purposes only.

Any suitable machining mode can be used: mechanical cutting tools, technical EDM, laser machining ....

Other features and advantages of the present invention appear from the following description of various conductors of the invention description given in an illustrative but not limiting.

In the accompanying drawing:<ul><li>- Figure 1 shows schematically in perspective a solenoid according to the invention,</li><li>- Figure 2 shows schematically in perspective a flat coil according to the invention,</li><li>- Figure 3 is a schematic partial perspective view of an element belonging to a dipole according to the invention</li><li>- Figure 4 is a developed top view of the element of Figure 3.</li></ul>

To achieve the variants illustrated in the figures, part of the following commodities: Y2O3, BaCO3, CuO, mixed in the proper proportions; after heat treatment is obtained in air at 1000 ° C the YBa2Cu3O7 compound, the critical temperature of 91 K. Such a method is described for example by K. Wu et al in the article published in Phys. Rev. Lett. 5B (1987) 90B.

Is carried out on the powder obtained by grinding a liquid medium so as to obtain a median grain diameter of between 0.5 and 2 .mu.m.

For the solenoid 1 according to the invention illustrated in Figure 1, one takes the above powder by isostatic pressing and is carried out under a pressure of about 2 tons per cm2, a cylinder whose dimensions are: - External diameter: 38 mm - Internal diameter: 30 mm - Length: 250 mm.

After sintering under oxygen at 970 ° C for one hour, one obtains a hollow cylinder whose elements are the following: - Outer diameter: 32.6 mm - Inner diameter: 25.5 mm - Length: 213 mm.

Is cut, the circular diamond saw for example, the cylinder 1 in a helix pitch as the ribbon width is 3 to 14 mm so as to have a section 2 of about 50 mm 2 for the passage of current.

This gives a self-supporting structure comprising ten to twelve turns; the equivalent length of conductor is obtained of the order of 1 meter.

Of course the solenoid is described a laboratory model. One can consider a geometrically similar model previous to implement in machines. One can also provide a second solenoid fitted around the first.

These coils are intended to be used especially in the prédisjoncteurs and processors.

In Figure 2 there is shown a parallelepiped plate 4 obtained by uniaxial pressing at 4 tons per cm2 of the oxide powder defined above. This plate has the following dimensions: 24 x 12 x 0.6 mm.

After sintering under oxygen at 970 ° C for one hour, one obtains a tile dimensions 20.5 x 10.2 x 0.5 mm. Using the fact that this material is sufficiently conductive at room temperature, it is possible to cut this plate 4 using the electroerosion technique, following the route 10.

One obtains a flat coil whose input and output are referenced 5 and 6, substantially non-inductive. Again the illustrated element is the laboratory model types. Such coil can industrially applied in the field of power electronics, such as a power valve.

In Figures 3 and 4 is seen half of a dipole 21 obtained from a sintered hollow cylinder of the same material as the previous windings. A cutting using a diamond saw for example, by a plane passing through the axis provides two half-cylinders. Each element 21 is machined by electro-erosion by 20 more clearly visible trace in Figure 4 developed. The input and output windings are referenced 22 and 23.

In the two similar elements of the dipole directions of current flow are opposite one another.

Such dipoles in particular find industrial applications in the inductors machines.

Naturally, the invention is not limited to the forms of drivers just described, nor to the mentioned machining modes. It applies to all superconducting materials have the characteristics of ceramics.