Superconducting structure for connecting tape conductors, in particular having a corrugated or serrated seam

Abstract

A superconductor structure (10, 20, 30), having a first strip piece (1), a second strip piece (2) and a third strip piece (3). Each strip piece has a substrate (5) and a superconducting layer (6) deposited thereon. End sections of the second and third strip pieces are connected via a layer (7) made of a first normally conducting material to the first strip piece, the second and third strip pieces overlap with the first strip piece, the superconducting layers of the second and third strip pieces face the superconducting layer of the first strip piece, and a seam (4, 23, 24) with a defined path length is formed between the end sections of the second and third strip pieces. The seam extends over an extension region (8) of the superconductor structure. Splicing strip pieces together in this manner achieves a high current load capacity.

Claims

1. A superconductor structure, comprising: a first strip piece having a first width B1, a second strip piece having a second width B2, and a third strip piece having a third width B3, wherein the first, second and third strip pieces each comprises a substrate and a superconducting layer deposited on the substrate, wherein one end section of the second strip piece and one end section of the third strip piece are connected via a layer made from a first normally conducting material to the first strip piece, wherein the second and third strip pieces overlap with the first strip piece in a longitudinal direction of the structure, wherein the superconducting layers of the second and the third strip pieces face the superconducting layer of the first strip piece, wherein the end sections of the second and the third strip pieces form a seam, wherein the seam has a path length PL such that PL>2*B2 and PL>2*B3, and wherein the seam extends in the longitudinal direction over an extension region of the superconductor structure having a longitudinal length LBN such that 0.5*PLLBN.

2. The superconductor structure according to claim 1, wherein the seam passes through the extension region or a partial region of the extension region, which selects a section of the extension region in the longitudinal direction, multiple times with respect to the longitudinal direction.

3. The superconductor structure according to claim 1, wherein at least half of the seam has a non-linear and/or polygonal course.

4. The superconductor structure according to claim 1, wherein the seam has at least a partial section, in which a course direction of the seam changes by at least 180.

5. The superconductor structure according to claim 1, wherein the seam in at least one partial section thereof is jagged or wavy.

6. The superconductor structure according to claim 5, wherein the seam in the partial section is in a wedge form with jagged or wavy edges on both sides of the seam.

7. The superconductor structure according to claim 1, wherein the seam has at least a partial section in which the seam is helical.

8. The superconductor structure according to claim 1, wherein: the seam forms a number of substantially identical partial structures, which have a maximal size MG, and the superconductor structure has a current drop distance SAD, with MG<SAD wherein SAD is determined as follows:
SAD={square root over (R.sub.St/.sub.0)} where R.sub.S is the specific contact resistance of a shunt layer and the superconducting layer of the first strip piece in Ohm*m.sup.2; t is the thickness or effective thickness of the shunt layer in m; .sub.0 is the specific resistance or effective specific resistance of the shunt layer in Ohm*m; and wherein the shunt layer comprises at least the layer made from the first normally conducting material.

9. The superconductor structure according to claim 1, wherein the seam is formed with rounded corners, so that for a minimal radius of curvature KKR of the seam,
KKR0.01*B2 and KKR0.01*B3,

10. The superconductor structure according to claim 9, wherein 0.2*B2KKR0.01*B2 and 0.2*B3KKR0.01*B3.

11. The superconductor structure according to claim 1, wherein
PL5*B2 and PL5*B3.

12. The superconductor structure according to claim 11, wherein PL25*B2 and PL25*B3.

13. The superconductor structure according to claim 1, wherein the second strip piece has a thickness D2, the third strip piece has a thickness D3, and the seam (4, 23, 24) has a width WT, and wherein
0.01*D2WT3*D2 and 0.01*D3WT3*D3.

14. The superconductor structure according to claim 13, wherein 0.02*D2WT2*D2 and 0.02*D3WT2*D3.

15. The superconductor structure according to claim 1, wherein 2*B1LBN100*B1.

16. The superconductor structure according to claim 1, wherein the seam with respect to a plane of symmetry, which runs along the longitudinal direction through a center of the superconductor structure and perpendicular to the substrates, is symmetrically formed.

17. The superconductor structure according to claim 1, wherein the seam is filled at least partially with a second normally conducting material.

18. The superconductor structure according to claim 17, wherein the second normally conducting material is a low-melting solder with a melting temperature of 80-350 C.

19. The superconductor structure according to claim 18, wherein the second normally conducting material is an alloy containing Bi, Sn, Pb, Cd, and/or Sn with precipitates of Ag, Au, and/or Cu.

20. The superconductor structure according to claim 1, wherein the seam has at least one partial section at which the second strip piece and the third strip piece mutually overlap.

21. The superconductor structure according to claim 1, wherein the material of the superconducting layers of the strip pieces has an anisotropy of the respective critical currents (Ic.sup.II, Ic.sup.) in the respective layer along the longitudinal direction to perpendicular to the longitudinal direction of 1.5 or less.

22. A superconductor structural group comprising at least two superconductor structures according to claim 1, wherein the two superconductor structures are electrically series connected to one another via their respective second or third strip piece.

23. The superconductor structure according to claim 1, wherein the first strip piece has a critical current strength Ic1, the second strip piece has a critical current strength Ic2, and the third strip piece has a critical current strength Ic3, and wherein the superconductor structure is acted on with a load current IA, wherein
Ic1<IA<Ic1+Ic2 and Ic1<IA<Ic1+Ic3.

24. The superconductor structure according to claim 23, wherein the superconductor structure, is an electronic component incorporated into a magnetic coil, an electric motor or a generator, a transformer, or a conductor.

25. The superconductor structure according to claim 23, wherein 1.1*Ic1IA0.9*(Ic1+Ic2) and 1.1*Ic1IA0.9*(Ic1+Ic3).

26. The superconductor structure according to claim 1, wherein the layer made from the first normally conducting material extends under the seam, and wherein 0.25*PLLBN.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is shown in the drawing and is further explained with reference to the exemplary embodiments.

(2) FIG. 1: a first embodiment of a superconductor structure according to the invention in schematic oblique view, with a helical seam;

(3) FIG. 2: a schematic view of a second embodiment of a superconductor structure according to the invention, with jagged seam;

(4) FIG. 3: a schematic view of a third embodiment of a superconductor structure according to the invention, with wavy seam;

(5) FIG. 4: a schematic view of a fourth embodiment of a superconductor structure according to the invention, with a mirror-symmetrical, overlap forming seam;

(6) FIG. 5: a schematic view of a fifth embodiment of a superconductor structure according to the invention, with a seam forming several loops;

(7) FIG. 6 a schematic longitudinal section of an embodiment of a superconductor structure according to the invention with through layer from a first normally conducting material, wherein the seam is partially filled with a second metallic material;

(8) FIG. 7 a schematic longitudinal section of an embodiment of a superconductor structure, with through layer from a first normally conducting material, with unfilled seam;

(9) FIG. 8 a schematic longitudinal section of an embodiment of a superconductor structure, with a layer interrupted at the seam made from a first normally conducting material;

(10) FIG. 9 a schematic top view of an embodiment of a superconductor structure according to the invention, with current flow lines in the region of the seam;

(11) FIG. 10 a schematic longitudinal section of an embodiment of a superconductor structural group according to the invention.

DETAILED DESCRIPTION

(12) The present invention relates to a connection of strip conductors with a superconducting coating, in particular HTS coating. The strip pieces here are arranged on one another with superconductor layers facing one another with mutual overlapping, so that there is an overlap over long distances, in particular 10 m or more, both before and after a joint. At a joint, a first strip piece in a first plane bridges the ends of two strip pieces (second and third strip piece) in a second plane. Between the strip pieces of the different planes, a normally conducting layer is arranged, whose ohmic resistance can be neglected owing to a long overlap. The second and third strip piece form a seam (joint) in the second plane. In accordance with an aspect of the invention, the seam is designed such that in sum an improved, in particular approximately galvanic transparency of the joint regions of the second and third strip piece is obtained. This is substantially achieved with a long path length of the seam and a suitable course of the seam with numerous direction changes, in particular with a jagged and/or wavy seam or also with seam sections at which the second and third strip piece mutually overlap.

(13) Typically there are at least 4, preferably at least 8, especially preferably at least 12 direction changes of the seam course by at least 60, preferably by at least 90. Furthermore, the seam typically has at least 1, preferably at least 2, especially preferably at least 4 overlapping seam sections.

(14) FIG. 1 shows a first embodiment of a superconductor structure 10 according to the invention. The superconductor structure 10 comprises a first strip piece 1 in a first, here lower plane E1, which overlaps with a second strip piece 2 and a third strip piece 3 in a here upper, second plane E2. The strip pieces 1, 2, and 3 are as a rule of the same design. The widths B1, B2, and B3 of the strip pieces 1, 2, and 3 here are identical and typically are 7-40 mm.

(15) Between the second strip piece 2 and the third strip piece 3 is a seam 4, on which the strip pieces 2, 3 form a joint. The seam 4 is here wound approximately in a helical fashion; the course direction of the seam varies generally ten times by 90 or more, wherein in the interior of the helix the second and third strip piece 2, 3 mutually overlap. The width WT of the seam 4 typically is 10-50 microns.

(16) The strip pieces 1, 2, and 3 each have a substrate 5, here made from sheet steel, on which a superconducting layer 6, here made from YBCO, is deposited. The superconducting layers 6 of the strip pieces 1 on the one side and 2, 3 on the other side face one another. Between the superconducting layers 6, a layer 7 made from a first normally conducting material (an Sn alloy with noble metal precipitates, for example) is arranged. The thickness of the layer 7 is relatively small, typically 5-20 microns, in order to not impede a current transfer between the superconducting layers 6 of the strip conductors 1 and 2, 3. The superconducting layers 6 each have a thickness t of typically 1-3 microns. The strip pieces 2, 3 usually have a thickness D2, D3 of around 200-400 microns, which is substantially determined by the substrate 5.

(17) The seam 4 extends in the longitudinal direction LR (which runs parallel to the main current direction) of the superconductor structure 10 via an extension region 8 with a length LNB. If one advances from the front end NE1 along the seam to the rear seam end NE2, a path length PL is covered.

(18) In the shown embodiment, LNB is twice as long as B2 or B3, and furthermore, PL is around eight times as long as B2 or B3.

(19) FIG. 2 shows a second embodiment of a superconductor structure 10 in top view, so that here above all the seam 4 at the joint is illustrated between the second strip piece 2 and third strip piece 3.

(20) The seam 4 here has a jagged course over two convergent arms, so that the path length in comparison with two straight convergent arms is greatly extended. With the two arms, the seam 4 runs through its extension region 8 in the longitudinal direction LR two times. The seam thus has a wedge-shaped course that is jagged on both sides. On each jag tip and on each jag base, the seam 4 forms an angle of around 90.

(21) The jags can each be understood as (approximately) equal partial structures 9 of the seam, which repeat several times on the arms. These partial structures 9 have a maximal size (maximum diameter) MG that is smaller than a current drop distance SAD of the superconductor structure, which is provided by
SAD={square root over (R.sub.St/.sub.0)}
with R.sub.S being the specific contact resistance of a shunt layer, here the layer 7 made from the first normally conducting material (see FIG. 1) and the superconducting layer 6 (see FIG. 1) of the first strip piece 1 (see FIG. 1) in Ohm*m.sup.2; t is the thickness of the shunt layer, here layer 7, in m; po is the specific resistance of the shunt layer, here layer 7, in Ohm*m. With for example R.sub.S=4*10.sup.8 Ohm*m.sup.2, t=2*10.sup.6 m and 0=2*10.sup.8 Ohm*m, there is a SAD of 2 mm.

(22) Alternatively, for example with R.sub.S=10.sup.1 Ohm*m.sup.2, t=10.sup.5 m and .sub.0=10.sup.9 Ohm*m (at temperatures of 4.2 K), SAD is 1 mm.

(23) In addition, at an overlapping partial section 27 of the jag flanks it is achieved that a local current direction LSR at the transition from the second strip piece 2 to the third strip piece 3 in the top view has a vectorial component opposed to the main flow direction HSR. Hereby in the first strip piece (covered in FIG. 2) locally the effective current strength is reduced due to the local current direction LSR, which can improve the current load capacity of the superconductor structure 10.

(24) FIG. 3 shows a third embodiment of a superconductor structure 10 according to the invention similar to the embodiment shown in FIG. 2. However, here the corners of the seam 4 are generally rounded, in order to avoid current spikes. In other words, the partial structures 9 here are designed as waves. The smallest radius of curvature KKR here is around 1/20*B2 or 1/20*B3; see also the magnified sector in this regard.

(25) At each wave, the course direction of the seam 4 changes by around 270. The local current direction LSR at a transition from strip piece 2 to strip piece 3, which is approximately perpendicular to the local seam course, accordingly changes strongly at each wave. This can lead in overlap to a local reduction in the current load, so that the current load capacity of the superconductor structure 10 is increased.

(26) FIG. 4 shows a fourth embodiment of a superconductor structure 10 according to the invention, in which the seam 4 is symmetrical with respect to a mirror plane SE. The mirror plane SE runs through the middle of the superconductor structure 10, parallel to the longitudinal direction LR. The seam 4 here has two overlapping partial sections 27, at which the local current flow direction LSR is in part vectorially counter to the main current flow direction HSR.

(27) Also in the embodiment of FIG. 5, the seam 4 of the superconductor structure 10 is mirror-symmetrical with respect to a mirror plane SE. The seam 4 is in a dendritic shape, with a plurality of loop-shaped partial sections 11, at which the course direction changes in each case by more than 180, cf. in this regard the directional arrows shown on a loop. In this way through the seam 4, a plurality of overlapping partial sections 27 are formed.

(28) FIG. 6 shows in a longitudinal section through a superconductor structure 10 as an example the course of currents in the region of the seam 4 at the change from the second strip piece 2 to the third strip piece 3, between the planes E1 and E2.

(29) Electrical currents, that here run in the strip piece 2 in the plane E2 toward the seam 4, largely penetrate the layer 7 made from the first normally conducting material and submerge in the first strip piece 1 in the plane E1 under the seam 4. Past the seam 4, they go back to the upper plane E2 into the third strip piece 3, cf. partial currents 12, 13. A part of the current, cf. partial current 14, penetrates only into the layer 7 made from the first normally conducting material, without penetrating the first strip piece 1. A further part of the current here also can penetrate a (partial) filling 16 of the seam 4 from a second normally conducting material, such as can be used for the layer 7.

(30) In the first plane E1 a base current also flowsapart from the partial currents 12, 13which is re-directed at the seam 4 (not further illustrated). This base current in the main current direction and the partial currents 12, 13 may not in the (vector) sum exceed the critical current Ic1 of the first strip piece 1 locally under the seam 4. Therefore, it is advantageous if the seam 4 runs transversely to the main current direction or is even overlapping, because then the current load in the first plane E1 can be kept low.

(31) FIG. 7 illustrates an embodiment of a superconductor structure 10 similar to the embodiment of FIG. 6 but in which the seam (the joint) 4 is not filled. In this case only the partial currents 12, 13 through the first strip piece 1 and a partial current 14 through the layer 7 are possible.

(32) In the embodiment of a superconductor structure 10 of FIG. 8, which is likewise similar to the embodiment of FIG. 6, the layer 7 is interrupted in the region of the seam 4. But filling 17 made from a second superconducting material is provided, which extends over the height of the layer 7, as well as a part of the height of the strip pieces 2, 3. In this case, partial currents 12, 13 through the first strip piece 1 and a partial current 18 through the layer 7 and the filling 17 can arise.

(33) FIG. 9 shows in top view the current flow 26 at a superconductor structure 10 according to the invention in the region of a seam 4, which runs transversely to a main current flow direction HSR (simultaneously the longitudinal direction of the superconductor structure 10). The current flow 26 is broken or diverted by the seam 4, typically so that the current flow 26 is approximately perpendicular to the local seam 4. Hereby the current flow 26 increases a total current flow in the first strip piece (comprising a base current flow in the main current flow direction and the current flow 26) in the main current flow direction HSR effectively less intensely in comparison with an (additional) current flow in the main current flow direction HSR. This effect is greater the more intense the divergence with respect to the main current flow direction at the seam 4; at an overlapping seam section (not shown), the total current flow in the main current flow direction HSR is even reduced.

(34) Preferably the superconducting layers of the strip pieces and in particular of the first strip piece, regarding to the respective critical current strength Id, Ic2, Ic3 are approximately isotropic (that is, the critical current Ic.sup.II parallel to the main current flow direction HSR is at most slightly over the critical current Ic.sup. perpendicular to the HSR, for example with Ic.sup.II/Ic.sup.1.5 or preferably Ic.sup.II/Ic.sup.1.1), so that the divergence can also be readily used for a higher current load capacity.

(35) FIG. 10 shows as an example a superconductor structural group 19 according to the invention, comprising a number of linked strip pieces 1, 2, 3, 21, 22 with superconducting layers 6 or comprising a number of superconductor structures 10, 20, 30 according to the invention.

(36) A superconductor structure 10 is formed with the strip pieces 1 (as first strip piece), 2 (as second strip piece), and 3 (as third strip piece), and with the seam 4 at the joint of the strip pieces 2 and 3.

(37) A further superconductor structure 20 is formed by the strip pieces 3 (as first strip piece), 1 (as second strip piece), and 21 (as third strip piece) with the seam 23 at the joint of strip pieces 1 and 21.

(38) Yet another superconductor structure 30 is formed by the strip pieces 21 (as first strip piece), 3 (as second strip piece), and 22 (as third strip piece), with seam 24 at the joint of the strip pieces 3 and 22.

(39) It is understood that the superconductor group 19 can be analogously extended by further strip pieces analogously. With the superconductor group 19, very long superconducting lines can be designed with high current load capacity.