WO2019101763A1

WO2019101763A1 - Superconducting strip conductor having a planar protective layer

Info

Publication number: WO2019101763A1
Application number: PCT/EP2018/082000
Authority: WO
Inventors: Mykhaylo Filipenko; Michael Frank; Jörn GRUNDMANN; Peter Van Hasselt
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-11-27
Filing date: 2018-11-21
Publication date: 2019-05-31
Also published as: DE102017221129A1

Abstract

The invention relates to a superconducting strip conductor (1) comprising a strip-like substrate (3) having two main surfaces (31a, 31b) and at least one planar superconducting layer (5) applied to a first main surface (31a) of the substrate (3), and at least one planar protective layer (11) which is applied to at least one of the main surfaces (33a) of the composite conductor (9) thus formed, the protective layer (11) being formed from a material which has a specific thermal conductivity of at least 2 W/(m.K) and which has a specific electrical resistance of at least Ohm.m. The invention further relates to an electrical coil device having such a strip conductor, and to a method for producing such a strip conductor.

Description

description

Superconducting band conductor with flat protective layer

The present invention relates to a superconducting tape conductor comprising a band-shaped substrate having two main surfaces and at least one applied to a first major surface of the substrate surface superconducting layer and at least one planar protective layer which is placed on at least one of the main surfaces of the conductor composite thus formed.

From the state of the art, superconducting band conductors, in particular high-temperature superconducting band conductors, are known, in which a superconducting material is deposited in a planar manner on a metallic substrate band. When electric coils are wound from such tape conductors, the individual turns of the winding are normally electrically isolated from each other. For this purpose, the band conductor inserted during winding is typically coated or encased with an electrically insulating material prior to the manufacture of the winding. Such an insulating layer also causes a defined distance between the electrically conductive components of the windings is maintained. Such a well-defined distance between the conductor turns is relatively difficult to achieve with other methods. Supralei tend coils are often provided either during winding with an impregnating resin between the turns or after winding with an insulating potting Vergos sen. In the first case one speaks of wet wraps, in the second case one speaks of dry wraps with subsequent Spu lenverguss. In both cases, however, it is difficult to produce a well-defined distance between the conductive regions of the individual windings by the impregnating resin or the potting compound. For a reliable and well-defined electrical insulation between the individual windings, it is therefore advantageous to provide an insulating layer of defined nished thickness between the electrically conductive components of the windings.

In conventional insulated strip conductors, the substrate provided with the superconducting layer is typically provided either by extrusion or by wrapping with an electrically insulating polymer layer. For this purpose, the head structure can be wrapped, for example, with a kapton tape. Alternatively, an electrically insulating plastic tape can be loosely inserted between the individual conductive windings.

A disadvantage of the known coil windings is that the current density of such a coil even at very high

Current carrying capacity of the superconducting layer through the un circumstances circumstances quite high layer thicknesses of substrate, Isola tion layer and optionally existing metallic cover layers is limited. Because of all these contributions, the total thickness of the strip conductor (including insulation) is much higher than the thickness of the superconducting layer alone. However, using conventional stripline constructions makes it difficult to use thinner layer thicknesses. In particular, certain minimum layer thicknesses must be maintained for the metallic substrate and the often present metallic cover layer in order to ensure good thermal bonding to the coil to a cooling system. This is necessary in order to cool the coil reliably and permanently to an operating temperature which lies below the crack temperature of the superconductor material used. In particular, special if the coil turns not (only) by direct thermal contact with a fluid coolant, but (also) cooled by a thermally conductive connection to a heat sink, then a relatively high proportion of the metallic components of the strip conductor is needed. Another difficulty with this type of cooling over a heat sink is that a good thermal contact between the metallic parts of the strip conductor and the heat sink must be ensured at all points. If For example, when wrapping the conductor structure with an electrically insulating polymer film, a cavity is formed, then there is in this place a worse heat transfer from the conductor structure on the polymer film to the adjacent heat sink.

Furthermore, additional metallic cover layers may be present, which fulfill the function of electrical stabilization of the strip conductor. This is done by bridging eventual small areas with reduced current carrying capacity.

The object of the invention is therefore to provide a superconducting strip conductor, which overcomes the disadvantages mentioned. In particular, a band conductor is to be made available ge, which allows in a winding made therewith a high current density with simultaneous effective cooling of the strip conductor. Another object is to provide an electrical coil device with such a ribbon conductor available. Furthermore, a method for producing such a strip conductor should be specified.

These objects are achieved by the belt conductor described in claim 1, the len device described in claim 12 electric Spu and solved by the method described in claim 14.

The superconducting band conductor according to the invention comprises a band-shaped substrate having two main surfaces and at least one planar superconducting layer applied to a first main surface of the substrate. The strip conductor further comprises at least one planar protective layer, which is applied to at least one of the main surfaces of the thus formed conductor composite. This protective layer is formed from a material which has a specific thermal conductivity of at least 2 W / (mK) and which has a specific electrical resistance of at least 10 ⁵ ohm-m. The named conductor assembly thus comprises the substrate and the superconducting layer and thus represents the conductor structure prior to application of the protective layer. In this case, one or more further intermediate layers may optionally be present between the substrate and the superconducting layer. These intermediate layers are then also part of the aforementioned conductor network. Such an intermediate layer may, for example, be a so-called buffer layer, the crystallographic structure of which predetermines a growth structure for the following superconducting layer. Furthermore, optionally on the superconducting layer (and / or opposite), a further sheet-like cover layer to be applied, which is then also to belong to the conductor assembly on which the said protective layer is applied to closing.

Said substrate may be formed normal conducting and formed in particular of a metallic material. It is essential in any case that the substrate forms a supporting band-shaped structure, which carries the (directly or indirectly indirectly via at least one intermediate layer) brought up on it planar superconducting layer. This planar superconducting layer can then be made very thin and does not have to be intrinsically stable, since it is held mechanically by the substrate. In principle, it is also possible that the superconducting layer is applied on both main surfaces of the sub strate. It is only essential in connection with the present invention that such a layer is formed on at least one of these main surfaces of the substrate.

Since the band-shaped substrate has two major surfaces, wei sen also both together with the other mentioned

Layers (except the protective layer) formed conductor composite and the total formed band conductor two such main surfaces on. The stated minimum value for the specific resistance should apply in particular at room temperature. Analogously, the said range of values for the thermal conductivity should be maintained, in particular at room temperature. Alternatively or alternatively, however, it may also be advantageous if the respective values given for the physical parameters are met even at a cryogenic operating temperature, that is to say for example at about 77 K or even lower operating temperature.

At the same time as the said resistance properties, the material of the protective layer should have a specific heat conductivity of at least 2 W / (m-K). In this way, advantageously, a good thermal connection of a coil winding formed from the strip conductor is achieved at a kopkop popping heat sink thereto. This is an essential part before part of the prior art, in which by thermally poorly conducting insulator layers between the windings, the thermal coupling of the entire winding package and in particular the superconducting layer is significantly deteriorated to an outer heat sink.

The main advantages of the invention are thus achieved in particular by the fact that the same layer, which ensures an electrical separation of adjacent turns, simultane- ously has a sufficiently high thermal conductivity for a good thermal connection of the entire winding package to a heat sink. In contrast, according to the prior art, these two properties (electrical insulation on the one hand and thermal conductivity on the other hand) are distributed over several superimposed layers. For the thermal cal connection of the entire winding package to a Kühlkör by the embodiment of the invention, however, is much more advantageous before, as a thermally very poorly conductive

Layer is completely avoided and thus an interruption tion of the thermal contact between the superconducting layer and the heat sink is also avoided. The electrical coil device according to the invention comprises at least one coil winding, which is formed from a fiction, contemporary superconducting band conductor. In particular, such a coil winding comprises a plurality of Windun conditions of such a strip conductor. The advantages of the inventions to the invention coil means are analogous to the advantages of the invention described above Bandlei age. An additional advantage may be seen in the fact that the protective layer described, which is part of the Bandlei age, compared to a subsequently introduced impregnating agent or a potting compound allows a significantly con stant winding distance. In particular, the distance of the superconducting layer, which results between the Weil each adjacent windings at different Umfangspo positions, over the entire winding are kept very constant ge when the layer thickness of the protective layer is accordingly constant. Further advantages of the device Spuleneinrich are given by the fact that in the band conductor structure according to the invention, the total thickness of the strip conductor can be kept very low and thus in the coil means a very high current density can be achieved. In this case, nevertheless, as described above, a sufficient electrical insulation from turn to turn and effective heat dissipation can be ensured.

The inventive method is used to produce a superconducting strip conductor according to the invention. In this method, the protective layer is deposited as a direct coating on the underlying layer. Such a direct coating should be understood to mean that the protective layer is formed as a solid layer only in situ on the conductor composite. In particular, it should not be present as a prefabricated solid layer, which is connected only nachträg Lich with the ladder network. In this case, different coating methods are conceivable, for example from the gas phase, from an aerosol or, in principle, also from a solution or melt. Optionally, the protective layer may also generally be affected by a chemical reaction of the material of the relevant main surface with a surrounding medium arise. A particular advantage of Direktbe coating the strip conductor is that the protective layer thereby very closely clings to the other layers of the Lei terverbundes and thus larger gaps between the conductor assembly and the protective layer can be avoided. Such gaps occur in the prior art easily when solid insulation bands are subsequently connected to the Leiterver bund and in particular at the edges of Lei terverbundes a perfect adaptation of the geometry of the Isola tion layer is not possible. By avoiding such gaps, an even better thermal connection of the winding package and in particular its superconducting can be achieved

Layer to be ensured to an outer heat sink.

Advantageous embodiments and further developments of the inven tion go from the dependent of the claims 1, 12 and 14

Claims and the following description. In this case, the described embodiments of the strip conductor, the coil device and the manufacturing method can generally be advantageously combined with each other.

Thus, the superconducting layer may in particular be a high-temperature superconductive layer. High temperature superconductors (HTS) are superconducting materials with a transition temperature above 25 K and in some material classes, for example the cuprate superconductors, above 77 K, where the operating temperature can be reached by cooling with cryogenic materials other than liquid helium , HTS materials are particularly attractive because these materials can have high upper critical magnetic fields and high critical current densities, depending on the choice of operating temperature. Therefore, the benefits of the invention, especially in connection with Hochtemperatursupralei tern come particularly to fruition.

The high-temperature superconductor may be, for example, magnesium diboride or an oxide-ceramic superconductor, for example have a compound of the type REBa2Cu30 _{x (} REBCO for short), where RE stands for a rare earth element or a mixture of such elements.

In a generally advantageous manner, the protective layer can be arranged at least on the side of the strip conductor which carries the superconducting layer. In other words, therefore, the sup raleitende layer (directly or indirectly, ie on a inter mediate layer) be covered by the protective layer.

In this embodiment may be particularly advantageous between tween the superconducting layer and the protective layer, an additional flat normal-conducting cover layer may be arranged. This cover layer may particularly preferably be connected directly to the superconducting layer. An essential advantage of such a normally conductive cover layer is that it forms a normally conducting parallel resistor for superconducting the layer, which in particular is electrically connected directly to it. Such a normally conductive cover layer may particularly preferably be formed from a metallic material (ie a metal or a metal alloy). The material of the cover layer may particularly preferably comprise copper or silver or even consist essentially of one of these materials. In this embodiment, then applied on the top layer protective layer causes sufficient electrical insulation between the top layer of a given conductor winding and the typically also electrically conductive bottom layer of the next adjacent conductor winding (ie, for example, the next substrate layer). Alternatively or additionally, such a cover layer but can also be placed on the side facing away from the superconductor side of the substrate. It can also encase the entire underlying layer structure.

In general, and independently of the optional presence of a cover layer, the protective layer may advantageously be arranged on the side of the strip conductor which contains the superconducting layer Layer carries. Alternatively or additionally, however, the protective layer can also be arranged on the side of the strip conductor which faces away from the superconducting layer. In particular, it is possible that the protective layer is arranged on at the main surfaces of the strip conductor. In this embodiment, the protective layer can wrap the conductor composite in particular on its entire cross-section, so that the sides of the conductor composite are covered by this protective layer abge. This covering of the sides is not absolutely necessary in the case of the two-sided execution of the protective layer. However, it may be advantageous to provide even more reliable electrical isolation, and in particular avoidance of short circuits or flashovers on the sides of the ribbon conductor.

Particularly preferably, in the band conductor, the protective layer may be applied as a direct coating on the underlying layer. The advantages of this embodiment are analogous to the advantages of the method according to the invention described above. In the combination of these from guide die having the above-mentioned version with double-sided, or even wrap-around application of the protective layer can orkommen _V that said "underlying layer" wech rare. For example, the protective layer may be applied as a direct coating on the substrate on the bottom of the stripline while on the upper side of the tape conductor it is applied as a direct coating either on the superconducting layer or on the overlying cover layer "Underlying layer" the "underlying" one

Layer "to understand.

The protective layer can generally advantageously have a layer thickness in the range between 1 μm and 100 μm, in particular between 2 μm and 20 μm or even between 2 μm and 10 μm. A layer thickness in the mentioned range is in particular that is large enough to ensure a sufficient electrical insulation from turn to turn with homogeneous deposition. On the other hand, the layer thicknesses are low enough to still allow a comparatively high current density of a coil winding formed with the ribbon conductor. In particular in combination with the variant of direct coating, the comparatively thinner layer thicknesses are advantageous in order to be able to achieve very high current densities in the winding.

Particularly preferably, the protective layer is formed from a material which has a specific thermal conductivity of at least 5 W / (mK), in particular at least 25 W / (mK) or even at least 100 W / (mK), particularly advantageously at least 1000 W / (mK). A protective layer with such a high thermal conductivity contributes particularly effectively to an effective heat dissipation of the entire stack of windings. There are some electrically insulating materials with such high thermal conductivities known.

The strip conductor is particularly preferably designed in such a way that the said protective layer is the electrically most insulating layer of the entire layer structure of the strip conductor, which has a layer thickness of more than 5 μm. In other words, in addition to the aforementioned protective layer, there is no essential additional insulator by means of which adjacent turns of the superconductor layer are electrically insulated from one another. Excluded from this consideration should be an intermediate layer between substrate and superconductor layer, which is often formed of electrically insulating oxidic materials. However, such an intermediate layer does not contribute to the electrical insulation of the turns with each other (since it is disposed between the substrate and the superconducting layer, which are typically both conductive and conductively connected to each other). These intermediate layers typically have a total layer thickness of less than 5 ym.

In this embodiment, without additional further isolator Layer between the conductive parts of adjacent windings, the advantages of the invention come particularly to bear because the limitation of the transverse conductivity by said

Protective layer is sufficient and without an additional

Layer an advantageously small overall thickness of the strip conductor can be achieved.

It is also particularly preferred in general if the band conductor is designed overall such that the said protective layer of all layers with more than 5 μm thickness is the layer which has the lowest specific thermal conductivity. In other words, in addition to the ge called protective layer no significant additional layer may be present, which forms an even weaker thermal bridge for the thermal connection of the superconducting layer to an outer heat sink.

Advantageously, the material of the protective layer may comprise diamond or a ceramic material, in particular an oxide and / or a nitride. For example, it may be aluminum oxide or aluminum nitride. In general, it may be preferred to be electrically insulating inorganic Metallverbin applications or to appropriate organometallic Verbindun conditions that meet the requirements for the thermal conductivity. In particular, it may be a compound (or optionally also a mixture of several compounds) of a metal which forms (or at least is contained in) the substrate and / or which forms the normally conductive covering layer (or at least is contained in this) , In particular, it may therefore be an anor ganic and / or an organometallic copper compound, iron compound or nickel compound. In this type of embodiment, the protective layer may be formed by in situ reaction on the surface of the substrate or the cover layer of the material contained therein. For example, a copper oxide can be formed by oxidation of the Kup fers, which forms the substrate or the cover layer. Similarly, from other metal len other oxides or nitrides are formed. It is also possible, for example, to form inorganic salts (for example copper sulphate) by reaction of the metal with a corresponding inorganic reactant or organometallic compounds in situ on the respective metal surface by reaction with a corresponding organic reactant. According to a first preferred embodiment, it is possible to provide the substrate already coated with the superconducting layer with the additional protective layer. It is important to observe such reaction conditions (in particular a low reaction temperature) in which the superconducting layer is not damaged. Alternatively, however, it is also possible in principle to apply the protective layer even before coating with the superconductor on the back side of the substrate, so that the reaction conditions can be selected without regard to the superconducting layer. Alternatively or additionally, it is also possible to apply the protective layer on one side to an intrinsically stable covering layer before this covering layer is then connected on the other side to the superconductor-coated substrate. Even then, the reaction conditions can be selected without regard to the superconductive layer, and higher reaction temperatures of, for example, 200 ° C. and more may also be used. The latter variants, in which the reaction conditions can be chosen without regard to a sensitive superconductor, are particularly suitable for the deposition of ceramic layers such as oxides and nitrides. Such ceramic layers are generally well suited to achieve a good electrical insulation effect while high thermal conductivity. For the deposition of ceramic

Layers are generally suitable, for example, methods of chemical and physical vapor deposition, for example MOCVD (metal-organic chemical vapor deposition) and sputtering.

Generally and independently of the exact choice of material, the protective layer can either be majority or substantially consist entirely of one or more of the said material classes.

The use of diamond in the material of the protective layer is particularly advantageous because diamond has a very high specifi cal thermal conductivity. At room temperature, this is in the range between 1000 W / m-K and 2500 W / m-K, which is particularly favorable for the heat coupling of the remaining layer system.

According to an advantageous embodiment, the

Protective layer of an electrically insulating material forms ge, which was a specific electrical resistance of even at least 10 ⁷ ohm-m. The use of such a well-insulating protective layer can be particularly advantageous especially if a very thin

Layer thickness for the protective layer is to be used, for example, a layer thickness of less than 20 ym, we less than 10 ym or even less than 5 ym.

It is generally particularly preferred if the total thickness of the strip conductor is not more than 130 μm, in particular not more than 100 μm or even not more than 60 μm. One of the art low overall thickness of the strip conductor leads to a correspondingly low winding spacing between the individual superconducting layers in a coil made therewith, which in turn leads to a particularly high current density in the winding. Such a low total thickness of the strip conductor can be achieved, for example, if the layer thicknesses that are as small as possible are used for the substrate and / or the optional cover layer. For example, the substrate may have a layer thickness of 20 ym or less. Alternatively or additionally, the optio normal existing normally conductive cover layer also have a layer thickness of 20 ym or less. Especially before geous materials for the substrate are stainless steel or nickel-containing alloys. When using tape conductors with conventional, ther mix poorly conductive insulation layers is the rich staltung with very thin substrates and layers often not possible because then thermal coupling to an outer heat sink is increasingly dominated by the insulating layer and thus only a poor thermal coupling before lies. The inventive design of the protective layer (instead of a conventional insulation layer) thus allows for many applications only the use of very thin NEN layer thicknesses in the said metallic layers, since here also on the protective layer is given a comparatively good thermal conductivity.

Further advantageously, the band conductor can be formed so that the thickness of the protective layer over the length of the strip conductor within +/- 5ym and in particular even within +/- 2ym constant. In this case, the smaller tolerance range for the above-mentioned comparatively thin band conductors is particularly preferred. Likewise, the thickness of the entire ribbon conductor over its length within +/- 10 ym and in particular even within +/- 5 ym kon be constant.

In the electric coil device, it may be advantageous for example, a coil device in an electric booster machine (in the rotor and / or in the stator), in a transformer and / or in a superconducting Energiespei cher (for example in a SMES = Superconducting Magneti shear energy storage) act.

According to a particularly advantageous variant of the method, the protective layer can be applied by a direct coating, in particular special by means of a vapor deposition and / or an aerosol deposition. In the Gasphasenab circuit may in particular generally a procedural ren chemical vapor phase shutdown (CVD method) or more specifically a plasma-enhanced CVD method (= PE-CVD method) act. Such methods have especially when exposed to coating with a thin diamond layer before geous. With diamond layers but also with other materials, particularly uniform and well-defined layer thicknesses are obtained with such processes.

However, in general and independently of the material of the protective layer, other methods may also be used, in particular methods for powder coating. Here, an amorphous, polycrystalline or monocrystalline powder of the material to be used can be applied on one side or beidsei TIG or even enveloping on the conductor assembly and converted here to a solid coating who the. This conversion can be done, for example, by a thermal treatment. The powder for the formation of the protective layer can be introduced, for example, by an additional thin layer of an adhesive on the ladder composite to stick ge.

In the following, the invention will be described by means of some preferred embodiments with reference to the appended drawings, in which:

1 shows a schematic sectional view through a Spu leneinrichtung according to the prior art,

FIG. 2 shows a schematic cross-sectional view of a band conductor according to a first exemplary embodiment of the invention,

Figure 3 is a schematic cross-sectional view of a Bandlei age according to a second embodiment of the invention He shows and

Figure 4 shows a schematic sectional view through a Spu leneinrichtung according to an example of the invention shows.

In the figures, identical or functionally identical elements are provided with the same reference numerals. FIG. 1 shows a detail of a coil device 21 with a coil winding 23 according to the prior art. Ge shows is a portion of a cross section of the coil Wick development 23 in an edge region of the winding. The coil winding 23 here comprises a plurality of turns w _± , of which only the edge regions of two turns are shown here as an example and the edge regions of the two adjacent turns partially. The individual turns w _± are formed by winding a strip conductor 1, whose structure will now be explained in more detail. Thus, the strip conductor 1 has a metalli cal substrate 3, on whose one major surface a flat-type superconducting layer 5 is formed. This superconducting layer 5 is covered by a normal-conducting covering layer 7, which may likewise be formed from a metallic material, for example copper and / or silver. Each of the layers shown may comprise multiple sublayers and additional interlayers may also be interposed between the individual layers, in particular one or more buffer layers between substrate 3 and superconducting layer 5. In this prior art stripline 1, the so formed Ladder composite wrapped by an electrically insulating plastic tape 10. This insulator is used for the electrical separation of the adjacent coil turns w _± .

1 is the cooling of the coil winding 23. In order to cool the material of the superconducting layer to an operating temperature below the critical temperature of the superconductor, the heat generated during operation must be effectively dissipated to an external cooling system. This cooling system is represented in FIG. 1 by a heat sink 25. The single ones

Layers of the strip conductor 1 are not directly in con tact with this heat sink 25, but indirectly via a potting compound 27, which may be a resin, for example. The heat sink 25 may be, for example, a copper plate. As schematically indicated in FIG. 1, essentially three cha characteristic heat paths pl, p2 and p3 are relevant. In this case, the heat path pl represents the heat dissipation from the substrate 3 to the heat sink 25. This heat dissipation is mediated in the edge region of the coil winding by the frontal part of the insulator 10 wound around it and by the casting compound 27 in between. Although these two materials 10 and 27 have a poorer thermal conductivity than the metal metallic materials 3 and 7, so is path pl but a total of the high thermal conductivity of metalli's substrate an important path for the cooling of the winding. The same applies to the parallel heat path p2, which extends from the metallic cover layer 7 (also via the short intermediate sections of the insulator 10 and the potting compound 27) to the heat sink 25. The third heat path p3 extends from the GE to the conductor composite wound insulator 11 via the potting compound 27 to the heat sink 25. However, this third heat path p3 contributes least to the cooling of the coil winding, since the insulator 10 as her conventional plastic material only a very low heat conductivity having. Typical specific thermal conductivity of insulating plastic tapes are only a few 0.1 W / mK. For this reason, it must be avoided in a Bandlei ter according to the prior art that this insulator 10 forms a too high proportion of the volume of the coil Wick development 23. If a certain minimum thickness of insulator is neces sary for the electrical separation of the individual turns NEN (for example, 5 ym or 10 ym), then also substrate 3 and metallic cover layer 7 may not be too thin, so this volume fraction of insulating plastic is not too high. However, such a lower limit for the thickness of the strip conductor also prevents very high current densities in the coil winding 23 can be achieved. Typical overall thicknesses for such prior art ribbon conductors are from 150 ym to 200 ym or slightly below.

Another disadvantage of the conventional design of Figure 1 is that, especially in the edge region of the coil winding 23 gaps may occur. For example, here is a first one Gap 29a, which has arisen between the conductor assembly and the enclosing insulator 10. This gap is in particular due to the fact that between substrate 3 and cover layer 7, a step-like offset has arisen, which can not be tightly covered during the wrapping with a prefabricated insulator tape. Another gap 29b has been formed at this point on the outside of the insulator band 10, since the potting compound 27 could not fully penetrate into the entste immediate tight depression. Both types of gaps also hinder the heat flow from the strip conductor 1 to the heat sink 25.

Figure 2 shows a schematic cross-sectional view of a strip conductor 1 according to a first embodiment of the invention. The strip conductor 1 comprises a metallic substrate 3, which has two main surfaces 31a and 31b. On the first main surface 31a, a planar superconducting layer 5 is deposited over a stack of buffer layers, not shown here. This superconducting layer 5 is in turn covered by a metallic cover layer 7. This cover layer 7 may for example consist of copper or silver or a stack of both materials. The substrate, the superconducting layer 5 and the cover layer 7 and the buffer layers, not shown together form a conductor composite 9. This conductor assembly 9 is wrapped on its entire cross-section of a protective layer 11. The protective layer is electrically insulating and is formed here as a thin diamond layer. But there are also many other Ma materials for this protective layer 11 conceivable. Essential in the context of the present invention is that the specific electrical resistance and the specific heat conductivity lie in the areas mentioned above. As a result, the described electrical separation of the Win is achieved achievements, at the same time in the same layer effective cooling is guaranteed. By this addi tional cooling a parallel heat path is used (analogous to p3 in Figure 1), which provides only a very insignificant contribution to the heat dissipation according to the prior art. This makes it possible, the thickness of the substrate d3

and / or to choose the thickness of the cover layer d7 and thus also the thickness of the entire conductor composite d9 enclosed by the insulator 11 to be significantly thinner than would be possible with the use of materials according to the prior art. Thus, the total also a very low thickness dl of the entire Bandlei age be provided, which allows very high current densities in a built-up with such a strip conductor 1 Spulenwick development. Furthermore, thin Bandlei ter also allow much lower bending radii, which can have a very positive effect, especially in the formation of compact end windings.

Figure 3 shows a schematic cross-sectional view of a strip conductor according to a second embodiment of the inven tion. The underlying conductor assembly 9 is similar or very similar to the structure of the conductor assembly 9 of Figure 2. The protective layer 11 is formed of a material with ähnli chen properties. In contrast to the example of Figure 2, however, this protective layer is not separated abge as enveloping layer, but only on one side on the ladder composite. In the example of Figure 3, the protective layer on the first main surface 33a of the conductor assembly 9 is the abgeschie the which the first main surface 31a of the substrate 3 speaks ent. This first major surface of the substrate is the surface on which the superconductive layer 5 is applied. It also corresponds to the first side 35a of the strip conductor 1. By such a protective layer 11 on this first side of the strip conductor 1, a sufficient insulation of the aufein other subsequent turns is also achieved in producing a winding from the strip conductor, since the metallic

Layers are always separated by the insulating protective layer 11 ge. Analogously to the example of Figure 2, the individual layer thicknesses can be made very thin here as well. Since the protective layer 11 is applied here only on one side, the total thickness dl of the strip conductor 1 can be even selected thinner ge. Alternatively, for example, Figure 3 but it is in principle Lich also possible that an analogous protective layer 11 is applied to the second side of the substrate 31b, which then the second side 33b of the conductor structure and the side facing away from the sup rondeitenden layer 5 side 35b of the strip conductor equivalent. Even with such a one-sided coating can be achieved by the insulating properties of the protective layer sufficient electrical separation of the adjacent Win applications. As a further alternative, a two-sided coating of the conductor assembly 9 is possible, wel che in contrast to Figure 2 but not wrapped around the edges with.

Figure 4 shows a schematic sectional view through a coil device 21 according to an example of the invention. The representation is analogous to the representation of the conventional Spu leneinrichtung in Figure 1. Again, the edge region egg ner coil winding 23 is shown, which is connected by a Vergussmas se 27 to a heat sink 25. In contrast to the coil device of Figure 1 here is the band conductor 1, from which the winding is formed, formed according to the inven- vorlie invention. In the example shown here, this strip conductor 1 is analogous to the strip conductor of Figure 2 out forms, namely with encircling wrapping with an elec- trically insulating protective layer 11. Because this protective layer 11 is applied as a direct coating on the conductor assembly 9, no gaps of the type arise here 29a, as seen in FIG. Even by this Ef fekt the cooling of the coil winding 23 is improved.

Another and possibly even more substantial improvement tion is due to the fact that the third heat path p3 of the protective layer 11 to the heat sink 25 in comparison with the ent speaking heat path p3 of Figure 1 is significantly enhanced. This is achieved by the significantly increased thermal conductivity of the protective layer 11 in comparison to the insulator 10.

Thus, in the conductor structure of Figure 4, the thickness of the sub strate 3 and or the cover layer 7 (absolute and / or ratio in relation to the thickness of the protective layer) chosen significantly lower be as in the prior art, without here the thermal coupling of the coil winding 23 is too much reduced.

Claims

claims

1. Superconducting band conductor (1) comprising

- A band-shaped substrate (3) with two major surfaces

(31a, 31b) and

- At least one on a first main surface (31 a) of the sub strate (3) applied surface superconducting layer (5)

- And at least one planar protective layer (11) which is applied to at least one of the main surfaces (33 a) of the so-th th conductor composite (9),

- wherein the protective layer (11) is formed of a material which has a specific thermal conductivity of at least 2 W / (mK) and which has a specific electrical resistance of at least 10 ⁵ ohm-m,

- wherein the protective layer (11) has a layer thickness (dll) of less than 20 ym.

2. strip conductor (1) according to claim 1, wherein between the superconducting layer (5) and the protective layer (11) an additional flat normal-conducting cover layer (7) is angeord net.

3. strip conductor (1) according to any one of claims 1 or 2, wherein wel chem the protective layer (11) on the side () of the strip conductor (1) is arranged, which carries the superconducting layer (5) and / or on the side ( 35 b) of the strip conductor (1) is arranged, which is abge of the superconducting layer (5).

4. strip conductor (1) according to any one of the preceding claims, wherein the protective layer (11) is applied as a direct coating on the underlying layer (7).

5. stripline (1) according to any one of the preceding claims, wherein the protective layer (11) has a layer thickness (dll) in the range between 2 ym and 10 ym.

6. stripline (1) according to any one of the preceding claims, wherein the protective layer (11) is gebil det of a material having a specific thermal conductivity of at least 25 W / (m-K).

7. strip conductor (1) according to any one of the preceding claims, wherein the protective layer (11) is gebil det of a material having a specific thermal conductivity of at least 100 W / (m-K), in particular even at least

1000 W / (m-K).

8. strip conductor (1) according to any one of the preceding claims, wherein the protective layer (11) is the most electrically insulating most layer of the entire layer structure of the strip conductor (1).

9. strip conductor (1) according to any one of the preceding claims, wherein the protective layer (11) comprises diamond.

10. strip conductor (1) according to any one of claims 1 to 9, wherein wel chem, the protective layer (11) comprises an inorganic Metallverbin tion and / or an organometallic compound.

11. strip conductor (1) according to any one of the preceding claims, which has a total thickness (dl) of at most 130 ym, in particular of at most 100 ym.

12. An electrical coil device (21) with at least one coil winding (23) made of a superconducting strip conductor (1) according to one of claims 1 to 11.

13. An electrical coil device (21) according to claim 12, wel che a coil device for an electrical machine, a transformer and / or a superconducting energy storage is.

14. A method for producing a superconducting Bandlei age (1) according to one of claims 1 to 11, wherein the Protective layer (11) is deposited as a direct coating on the underlying layer (7).

15. The method of claim 14, wherein the direct coating is applied by means of a vapor deposition and / or an aerosol deposition or by a chemical reaction of the surface with a surrounding medium in situ arises.