Superconduting coil device comprising coil winding and contacts

Abstract

A superconducting coil device includes at least one coil winding, including at least one first and one second superconducting strip conductor, the first and second strip conductors each having a superconducting layer and a contact side provided with a contact layer; at least one first contact electrically connecting the contact side of the first strip conductor to an external circuit via a first contact piece; at least one second contact electrically connecting the contact side of the second strip conductor to the external circuit via a second contact piece; and a third contact electrically connecting the first and second strip conductors via the contact layer of the first and the second strip conductor within the coil winding, wherein the contact side of the first strip conductor has a different orientation relative to a center of the coil winding than the contact side of second strip conductor.

Claims

1. A superconducting coil device, comprising: at least one coil winding, which comprises a first stack formed by at least two first superconducting strip conductors, and a second stack formed by at least two second superconducting strip conductors, said first and second strip conductors each having a superconducting layer and a contact side provided with a contact layer; at least two first contacts each individually electrically connecting the contact side of a first one of the first strip conductors and a second one of the first strip conductors respectively to an external circuit via respective first contact pieces; at least two second contacts each individually electrically connecting the contact side of a first one of the second strip conductors and a second one of the second strjp conductors respectively to the external circuit via respective second contact pieces; and at least two third contacts located adjacent one another, each individually electrically connecting the corresponding individual first strip conductor respectively with the corresponding individual second strip conductor via the contact layers of the first and the second strip conductors within the coil winding, wherein the contact side of the first strip conductors has a different orientation relative to a center of the coil winding than the contact side of second strip conductors.

2. The coil device of claim 1, wherein the first and second strip conductors each have turns, wherein the at least two first contacts are disposed on a side of the first strip conductors facing away from the turns of the first strip conductors, and wherein the at least two second contacts are disposed on a side of the second strip conductors facing away from the turns of the second strip conductors.

3. The coil device of claim 1, wherein the at least two first contacts are formed between respective first contact pieces and the contact layer on the contact side of the first strip conductors and the at least two second contacts are formed between respective second contact pieces and the contact layer on the contact side of the second strip conductors.

4. The coil device of claim 1, wherein the at least two first contacts are disposed on an inner side of the coil winding and the at least two second contacts are disposed on an outer side of the coil winding.

5. The coil device of claim 1, wherein the at least two third contacts are formed between the first strip conductors and the second strip conductors via a soldered connection.

6. The coil device of claim 1, wherein a contact resistance of the at least two third contacts is less than 1 Ohm.

7. The coil device of claim 1, wherein a contact resistance of the at least two third contacts is less than 100 nOhm.

8. The coil device of claim 1, wherein the at least two third contacts are formed between the first and the second strip conductors over a length of from 1 cm to 5 cm.

9. The coil device of claim 1, further comprising a cooling device for cooling the windings, wherein in an area of the at least two third contacts, a thermal coupling to the cooling device is more pronounced than in remaining areas of the winding.

10. The coil device of claim 1, wherein the first and second strip conductors each include a superconducting layer containing a second-generation high-temperature superconductor, especially ReBa.sub.2Cu.sub.3Ox.

11. The coil device of claim 1, wherein the contact layer and/or the at least two first and second contact pieces contain copper.

12. The coil device of claim 1, wherein the first and the second strip conductors each include a substrate, and another contact layer provided on a side of the substrate that faces away from the superconducting layer and/or are enveloped on all sides by a contact layer.

13. The coil device of claim 1, wherein the coil winding is constructed as a disk winding.

14. The coil device of claim 13, wherein the coil winding is constructed as one of a race-track coil, as a rectangular coil and a cylindrical disk winding.

15. The coil device of claim 1, wherein the turns are mechanically fixed with a casting compound and/or with an adhesive.

16. The coil device of claim 1, comprising an even number of the first and second strip conductors, said first and second strip conductors being connected to one another via an odd number of multiple said third contact.

Description

(1) The invention is described below on the basis of two preferred exemplary embodiments, which refer to the appended drawings, in which:

(2) FIG. 1 shows a schematic cross-section of a superconducting strip conductor,

(3) FIG. 2 shows a schematic view of a coil winding according to the prior art,

(4) FIG. 3 shows a schematic view of a coil winding according to a first exemplary embodiment, and

(5) FIG. 4 shows a schematic view of a coil winding according to a second exemplary embodiment.

(6) FIG. 1 shows a cross-section of a superconducting strip conductor 1 in which the layer structure is presented schematically. The strip conductor in this example comprises a substrate strip 2, which is a 100 m thick substrate strip made of a nickel-tungsten alloy. As an alternative steel strips or strips made of an alloy such as Hastelloy for example can be used. Disposed above the substrate strip is a 0.5 m thick buffer layer 4 which here contains the oxidic materials CeO.sub.2 and Y.sub.2O.sub.3. Above this is the actual superconducting layer 6, here a 1 m thick strip of YBa.sub.2Cu.sub.3O.sub.x, which in its turn is covered by a 50 m thick contact layer 8 made of copper. As an alternative to the material YBa.sub.2Cu.sub.3O.sub.x the corresponding compounds REBa.sub.2Cu.sub.3O.sub.x of other rare earths RE can be used. On the opposite side of the substrate strip here a further 50 m thick cover layer 10 made of copper is disposed, followed by an insulator 12, which is embodied in this example as a 25 m thick Kapton strip. The insulator 12 can however also be constructed from other insulating materials such as other plastics for example. In the example shown the width of the insulator 12 is somewhat larger than the width of the other layers of the strip conductor 1, so that with a winding of the coil device, turns which lie above one another are reliably insulated from one another. As an alternative to the example shown it is possible to not wind an insulator strip into the coil device as a separate strip until the coil winding is being manufactured. This is especially advantageous if a number of strip conductors are wound in parallel which do not have to be insulated from one another. Then for example a stack of 2 to 10 strip conductors lying one above the other without an insulation layer can be wound together with an additionally inserted insulation strip into common turns.

(7) Contacting of the strip conductor 1 is advantageously possible via the contact layer 8. The side of the strip conductor 1 lying at the top in FIG. 1 is therefore also referred to as the contact side 13.

(8) FIG. 2 represents a highly schematic view of a coil winding 15 according to the prior art. Here a strip conductor 1 is wound in two turns W.sub.1 and W.sub.2 to the coil winding 15. The number of turns is only to be understood as an example here. In typical applications the number of turns is usually between 10 and 500. In the coil winding shown the strip conductor 1 is wound so that the contact side 13 lies on the inside. In order to connect the coil winding 15 to an external circuit, two contacts 17, 21 with two contact pieces 19 and 23 are needed. The first contact 17 in such cases lies on the outside of the coil and the second contact 21 lies on the inside of the coil. Since the contact side 13 of the strip conductor 1 lies on the inside with the second contact, simple contacting in a free area of the strip conductor is possible. On the outside on the other hand the first contact 17 is made by the first contact piece 19 being pushed into the coil winding. With gluing of the coil during the winding process this area must be kept free from adhesive. After the first contact 17 is established, to guarantee the mechanical stability of the coil, there must be a retroactive gluing and/or reinforcement (not shown here). The contact pieces 19, 23 are typically massive blocks of copper having a large cross-section in order to make available the very high operating currents for the superconducting coil device. This means that the first contact piece 19 inserted into the winding requires a large amount of space which is mostly significantly greater than that shown in the schematic view of FIG. 1.

(9) FIG. 3 shows a highly schematic view of a coil winding 25 according to a first exemplary embodiment of the invention. Here too only two turns W.sub.1 and W.sub.2 are shown once again, which are intended to stand for a significantly larger number of turns, for example between 10 and 500 turns. The coil winding 25 is once again able to be connected via two contacts 17, 21 and contact pieces 19, 23 to an external circuit. The coil winding 25 contains a first strip conductor 31 and a second strip conductor 32, which are connected to one another via a third contact 33. The third contact 33 is realized in this example via a soldered connection between the contact sides 13 of the two strip conductors, with indium-based solder as the solder material. The connection is thus made between the contact layers 8 of the strip conductors. The contact resistance of the third contact is less than 100 nOhm. The third contact is embodied over a length of 3 cm. The connection of the first and second strip conductors leads to the contact side 13 being freely accessible both on the inside and also on the outside of the coil winding. This enables the contacts 17 and 21 for connection to an external circuit to be made in a simple manner. Both contacts 17 and 21 can be made for example by establishing soldered connections to the contact pieces 19 and 23 without a contact piece having to be introduced into the winding. To guarantee the mechanical stability of the coil device, the coil winding 25 can be fixed either during or after the winding of the coil with an adhesive or a casting compound. The fixing can be undertaken before or after the external contacts 17 and 21 are established. With gluing or casting before the contacts are established only the freely accessible contact surfaces for the contact 17 and 21 have to be kept free of adhesive or casting medium.

(10) FIG. 4 shows a highly schematic view of a coil winding 35 according to a second exemplary embodiment of the invention. In the coil winding 35 a stack 37 consisting of two layers of strip conductors is wound to the coil. Once again only two turns W.sub.1, W.sub.2 are shown by way of example, which are intended to stand for a larger number of windings. Likewise the two layers within the stack are also representative of a larger number of layers, for example 3 to 10 layers. Each of the layers comprises a first strip conductor 41, 42 and a second strip conductor 43, 44, which are connected to one another within each layer by way of a third contact 38, 39.

(11) The third contact is once again realized as a soldered connection on the contact sides 13 of the respective strip conductors 41 to 44. The connection is thus made between the contact layers 8 of the strip conductors. The connection of the first 41, 42 and second 43, 44 strip conductors within each layer via the third contacts 38, 39 achieves the result that both on the inside and also on the outside of the coil winding the contact sides 13 are freely accessible for all strip conductors from both layers. Thus the first contact 17 with the first contact pieces 19 and the second contacts 19 with the second contact pieces 23 can be made in a similar way to the first exemplary embodiment without inserting contact pieces into the winding.

(12) In the second exemplary embodiment the strip conductors each have a substrate 2, a buffer layer 4, a superconducting layer 6, a contact layer 8 and a cover layer 10, similar to the layout shown in FIG. 1. When a stack of strip conductors is used, the individual strip conductors however expediently have no separate insulation layer 12. Instead, to insulate the windings from one another, during the manufacturing of the coil, a separate insulator strip (not shown here) is inserted into the winding.