SUPERCONDUCTING ELECTRICAL COIL DEVICE AND ROTOR WITH COIL DEVICE

Description

[0001] The present invention relates to an electrical coil device designed as a coil device for an electrical machine, comprising a winding support and a winding made of a superconducting conductor mounted on the winding support, as well as a coolant channel for circulating a fluid coolant. Furthermore, the invention relates to a rotor for an electrical machine having such a coil device.

[0002] Superconducting electrical coil devices are known from the prior art and are used as excitation windings in the rotors of electrical machines. In order to cool the coil device to a cryogenic operating temperature below the critical temperature of the superconductor used during operation of such a machine, such a rotor often also has a cooling system. Such a cooling system can, for example, comprise one or more coolant channels in which a fluid (i.e., a liquid or gaseous) coolant circulates. In such cases, it is important that there is a good thermal connection between the coil device to be cooled and the fluid coolant. Many such rotors have a supporting rotor core on which one or more superconducting coil devices are mounted. In many cases, this rotor core is also cooled to the cryogenic operating temperature.The rotor is then essentially a completely cooled rotor.

[0003] Alternatively, however, it is fundamentally also possible for the rotor core to be at a comparatively warm temperature level during operation, with only the immediate vicinity of the superconducting coil device being locally cooled. One such variant is described in more detail in US patents US9431864B2 and US8664809B2, for example. According to these two documents, the superconducting excitation coils can be attached to a comparatively warm, soft-magnetic rotor core by means of retaining straps with comparatively poor thermal conductivity. Here, too, coolant channels are arranged in the area of the superconducting coils, through which a fluid coolant can flow, thus cooling the coils to a cold operating temperature. One advantage of such a warm rotor core is that no additional cooling effort is required for the cryogenic cooling system to compensate for the losses in this area of the rotor.However, good thermal insulation and reliable torque transmission for different spatial directions between the warm rotor core and the superconducting coils must be ensured. This can lead to comparatively high equipment costs for mounting the individual coils, for example, the need for retaining straps for different directions.

[0004] From JP H08 130134 A, a superconducting coil device for a transformer is known in which several superconductors in the form of a helix are applied to a hollow tube in the form of a ring through which a cooling fluid flows.

[0005] EP 3 292 554 A1 discloses a transformer with high-temperature superconducting strip conductor windings, each of which is wound in several turns around a common ring-like basic structure, in which the windings are cooled by an enclosing cryostat.

[0006] From DE 10 2014 114451 A1 an electrical machine is known which has a coil winding made of superconducting material, in which a cooling tube of a cooling device which is suitable for cooling superconducting material to below the transition temperature is wound tightly around the coil winding.

[0007] From DE 10 2011 056008 A1 an electrical machine is known which has a stator winding made of superconducting material, in which the stator winding is arranged within a cryostat.

[0008] From FR 1 270 987 A an electrical machine is known in which a winding conductor is designed such that a plurality of helically twisted conductor segments form a central cooling channel.

[0009] From DE 199 58 727 A1, a superconducting coil is known in which a ceramic heat sink, an electrical bypass and the winding of a superconductor are applied to a hollow tube through which a cooling fluid flows.

[0010] The essential requirements placed on a superconducting coil assembly of such a rotor, and in particular on the connection of the coil assembly to the other rotor components, lie, on the one hand, in the areas of thermal insulation and the coupling of the coils to a cooling system, and, on the other hand, in the area of the mechanical stability required for the operation of the rotor. This refers, on the one hand, to the mechanical stability of the coil suspension, which is exposed to strong centrifugal forces and strong electromagnetic forces, particularly at high speeds and / or high machine power. On the other hand, the mechanical stability of the superconducting coil assembly also means that the superconducting conductor itself does not experience any mechanical damage, either during the manufacture of the coil or during operation.This also includes ensuring that the tolerable bending radii of the superconducting conductor are not exceeded. Many known superconducting conductors, and in particular superconducting strip conductors, are sensitive to excessive local bending, especially bending within the strip conductor plane. Such boundary conditions must also be considered when designing the coil winding. On the other hand, however, in many applications it is desirable to achieve the most compact coil geometry possible, and in particular, the most compact winding heads possible. Winding heads are generally understood to mean those coil areas in which axial coil segments (aligned along the main axis of the machine) are electrically connected to one another by connecting segments.Compact winding heads are essential for providing machines that are as small and lightweight as possible, and especially machines with high power density. Especially for racetrack coils made of superconducting ribbon conductors, the space required for the winding heads is often comparatively high due to the low flexibility of the ribbon conductors.

[0011] The object of the invention is therefore to provide an electrical coil device that overcomes the aforementioned disadvantages. In particular, an electrical coil device is to be provided that is mechanically stable, in which the superconductor can be reliably cooled to a cryogenic operating temperature, and which simultaneously requires little space in the area of the winding heads. A further object is to provide a rotor for an electrical machine with the corresponding properties.

[0012] These objects are achieved by the electrical coil device described in claim 1 and the rotor described in claim 9.

[0013] The electrical coil device according to the invention has a winding support formed from an elongated hollow tube. This hollow tube is shaped like a ring, so that the ring shape of the winding support forms an overarching loop of the coil device. Furthermore, the coil device has a winding made of a superconducting conductor attached to the winding support. The superconducting conductor is wound helically around the hollow tube in a plurality of individual turns, so that the ring shape of the winding support forms at least one overarching turn of the entire helix. The interior of the hollow tube is designed as a coolant channel for the circulation of a fluid coolant.

[0014] In other words, two windings are nested within the coil device: A first, subordinate winding is provided by the multitude of individual turns of the conductor around the winding support, whereby an overall helical winding is present. A second, higher-order winding is predetermined by the ring shape of the winding support, whereby the helix wound on the winding support as a whole is present in at least one loop - and thus at least one higher-order winding. In particular, the helical winding can extend over a substantial part of the length of the ring-shaped hollow tube and, particularly advantageously, even over the entire circumference of the ring. This ensures that the (subordinate) helical winding forms a complete (higher-order) winding loop of the superconducting conductor. Overall, this results in a net current transport along the local direction of the hollow tube.

[0015] In principle and generally advantageously, the winding support can be designed as a closed ring, so that the shape of the winding support forms exactly one superordinate loop (and thus exactly one superordinate turn). Alternatively, however, it is also possible for the winding support to not be completely closed, but only largely ring-shaped. Thus, there can be a comparatively small open area of the winding support, which can optionally be closed by a separate connecting piece. In principle, however, it is also possible for the superordinate winding to comprise not just a single turn, but a plurality of such turns.For this purpose, in particular, several superimposed helical windings can be applied to a ring-shaped closed winding carrier, so that in turn a total of several superordinate windings (here consisting of the individual layers of the helix) are formed for the conductor.

[0016] The coolant channel inside the hollow tube can be designed, in particular, for the circulation of liquid or gaseous coolant within a completely closed coolant circuit of the rotor. For this purpose, the coolant channel can, in particular, have lateral (i.e., non-tangential) connections through which such a fluid coolant can be introduced or discharged.

[0017] A key advantage of the coil device according to the invention is that the winding support, designed as a hollow tube, provides mechanical stability to the superconducting conductor wound helically thereon and also enables reliable cooling. Unlike conventional excitation coils in superconducting rotors, where the superconducting coils are often impregnated or encapsulated flat coils made of superconducting strip conductors, the coil winding does not have to be self-supporting. In other words, the coil winding is not an intrinsically stable component; rather, the individual turns of the helical winding are mechanically held by the winding support, and without the support, the winding may not be dimensionally stable.This has the advantage that the superconducting conductor itself can be made mechanically less rigid and, in particular, thinner than in the prior art. In particular, the impregnating agent or potting compound for the coil winding, which is common in the prior art, can be omitted. A further advantage of such a non-intrinsically stable winding design is that the individual turns can be cooled more easily and efficiently.

[0018] This is generally advantageously achieved in the coil device according to the invention by providing cooling via the hollow tube itself supporting the winding. For this purpose, the interior of the hollow tube is designed as a coolant channel. This spatial proximity of a cryogenic coolant makes it particularly easy to achieve efficient cooling of the superconducting conductor. A further advantage of this particularly close thermal connection between the conductor and the fluid coolant is that, by means of cooling from within the winding, the short-term formation of local hotspots (i.e., hot spots formed during operation of the superconductor, either due to quenching processes or transient operating conditions or faults) can be tolerated and buffered without leading to a breakdown of the superconducting properties of the entire coil winding.Such a collapse can be avoided in the inventive design by thermally coupling the coil windings closely to the cryogenic coolant via the hollow tube of the winding support. Furthermore, the coil windings can be thermally well insulated radially outward from the warm external environment. A design of the hollow tube supporting the winding with comparatively high thermal conductivity and / or high heat capacity thus advantageously contributes to preventing such a collapse. The material as well as the inner and outer diameters of the hollow tube can advantageously be dimensioned to ensure good thermal connection while simultaneously providing sufficiently high heat capacity and low flow resistance for the coolant.

[0019] A further advantage of the embodiment according to the invention compared to the prior art can be seen in the fact that relatively small bending radii can be tolerated for at least one higher-order coil winding, at least in some areas, and thus relatively compact winding heads can be achieved for the winding as a whole. This advantage arises from the fact that when producing a helical winding from the superconducting conductor, smaller bending radii can be tolerated both for the uniform bending of the conductor within the subordinate helical windings and for the higher-order bending of the helix as a whole than, for example, for the bending of a strip conductor within the strip plane. However, even a locally narrow bend perpendicular to the conductor plane - for example, in one of the corners of a rectangular coil according to the prior art - can have a more critical effect than a uniformly tight winding with small bending radii within the helix.

[0020] Overall, the invention provides a coil device which is advantageously both mechanically stable and can be cooled effectively and reliably and can be designed with compact winding heads.

[0021] The rotor according to the invention has at least one such coil device according to the invention. The advantages of the rotor according to the invention are analogous to the previously described advantages of the coil device according to the invention.

[0022] Advantageous embodiments and further developments of the invention emerge from the claims dependent on claims 1 and 9 as well as the following description. The described embodiments of the coil device and the rotor can generally be advantageously combined with one another.

[0023] Thus, the coil device generally advantageously has a coil axis, which in particular can be a longitudinal coil axis of an elongated shaped coil. In this case, the coil device can have two axial coil legs that extend essentially in the axial direction. Particularly advantageously, these can be straight axial coil legs that extend parallel to the coil axis. Alternatively, however, the axial coil legs can also be curved or kinked, so that a slight angle with the coil axis can result for individual partial regions. Such an angle β can advantageously lie in a range up to β = arctan(W / L), where W is the maximum width of the coil (perpendicular to the longitudinal axis) and L is the length of the coil.

[0024] The general design with axial coil legs is particularly advantageous for use of the coil device as a rotor coil in a rotating electrical machine. In such an application, the coil legs oriented axially with respect to the machine axis are particularly crucial for the electromagnetic interaction between the rotor and stator. In such an application, the longitudinal coil axes of a plurality of such coil devices can each run parallel to the central rotor axis (and thus the machine axis).

[0025] Generally advantageously, within the axial coil legs, the superconducting conductor can form a local angle α with the coil axis, which is in the range of up to 89.4°. Although the coil legs as a whole are parallel to the coil axis, the superconducting conductor itself does not run parallel to this axis due to the subordinate helical winding. For electromagnetic interaction in an electrical machine, however, it is advantageous if the conductor in question forms the smallest possible angle with the machine axis. This is achieved by the aforementioned advantageous angular range for the conductor within the helical winding. Particularly advantageously, the absolute value of the angle of the conductor with the longitudinal axis is essentially the same within the axial conductor legs. Within the helix, only the local orientation of the conductor changes with respect to the longitudinal axis. However, it is also possible in principle for the absolute value of the angle to vary.In such cases, the specified angular range should not be exceeded for the entire axial coil limbs if possible.

[0026] The angle α can particularly advantageously lie in the range between 11° and 89.5°, in particular in the advantageous sub-range between 11° and 79° or in the particularly preferred sub-range between 11° and 22°. The values given as examples for the angle α can be achieved in particular with the following parameters: An angle α of approximately 11° can be realized, for example, with an outer radius of the hollow tube of 10 mm, a conductor width of 20 mm and a pitch of 200 mm. An angle α of approximately 22° can be realized, for example, with an outer radius of the hollow tube of 10 mm, a conductor width of 20 mm and a pitch of 100 mm. An angle α of approximately 79° can be realized, for example, with an outer radius of the hollow tube of 10 mm, a conductor width of 4 mm and a pitch of 8 mm.An angle α of approximately 89.5° can be achieved, for example, with an outer radius of the hollow tube of 50 mm, a conductor width of 2 mm, and a pitch of 2 mm. The parameter combinations of the examples mentioned are dimensioned such that the limit values for irreversible strain (ε irr ) of superconducting strip conductors are adhered to during torsion within the helical winding, which limit values can, for example, be in the range between ε irr = 0.2% and 2%. In general, and regardless of the combinations mentioned with other parameter values, the conductor width can advantageously be in the range between 2 mm and 20 mm, in particular between 4 mm and 12 mm. In general, and regardless of the combinations mentioned with other parameter values, the pitch of the helix can be in the range between 1 and 10 times the conductor width, in particular in the range between 2 and 5 times this value.To achieve the most axially aligned geometry of the individual conductors within the specified angular range, it is advantageous for the helical winding to be designed with a comparatively large pitch. In other words, the subordinate individual turns of the helical winding should not be wound too tightly overall. This applies in particular to the aforementioned axial legs, but optionally also to any additional connecting legs.

[0027] In general, the coil assembly can have two axially terminal connecting legs in addition to the two aforementioned axial conductor legs. These four coil legs can then define a closed, ring-shaped coil assembly. Such a coil assembly can, for example, have the basic shape of a rectangular coil (optionally with slightly rounded corners), an oval coil, or a racetrack coil.

[0028] According to a first advantageous embodiment, the terminal connecting legs can each be designed as straight legs. In this embodiment, the entire coil can then advantageously extend within a single coil plane. This results in a particularly simple coil geometry, which can also facilitate the arrangement and mounting of the coil device on a mechanically supporting rotor body.

[0029] Alternatively, according to a second advantageous embodiment, the terminal connecting legs can also be designed as curved legs. In particular, these connecting legs can be bent out of the plane of the axial legs. For example, such a bend can be a bend around a central rotor axis of a higher-level rotor, so that the coil legs of the coil device extend on a common cylindrical surface. This creates space for the rotor shaft, for example, in the center of a rotor unit.

[0030] Generally advantageously, the hollow tube carrying the subordinate helical winding can have a round cross-sectional shape. Such a round cross-sectional shape, particularly on the outside of the hollow tube, facilitates the application of a helical winding made of a superconducting conductor without the conductor having to be bent excessively. Particularly advantageously, the outside of the hollow tube can have an approximately circular cross-section, which then leads to a particularly symmetrical shape of the helical winding. Advantageously, the outside of the hollow tube can have one or more helical grooves surrounding it, into which the helically wound superconducting conductor can be inserted.

[0031] The inner surface of the hollow tube can also generally advantageously be designed with a round and in particular circular cross-section in order to enable a low-resistance circulation of fluid coolant inside the hollow tube.

[0032] Generally advantageously, the hollow tube can have an inner diameter of 50 mm or less. In particular, the inner diameter can be in the range of 2 mm to 20 mm. This defines a correspondingly narrow coolant channel. Within this range, a sufficiently high cooling performance can be achieved. The outer diameter can accordingly be in the range of 4 mm to 100 mm, for example, and particularly advantageously in the range between 10 mm and 50 mm. For pipe cross-sections that are not exactly circular, the stated diameters should be understood to be the largest inner or outer dimension.

[0033] The aforementioned superconducting conductor may generally comprise one or more superconducting strip conductors. Such a strip conductor may have a comparatively thin superconducting layer on a carrier substrate.

[0034] The superconducting conductor in general (and a superconducting tape conductor in particular) can particularly advantageously comprise a high-temperature superconducting material. High-temperature superconductors (HTS) are superconducting materials with a transition temperature above 25 K, and in some material classes, such as cuprate superconductors, above 77 K, where the operating temperature can be reached by cooling with cryogenic materials other than liquid helium. HTS materials are also particularly attractive because, depending on the choice of operating temperature, these materials can exhibit high upper critical magnetic fields as well as high critical current densities.

[0035] The high-temperature superconductor can, for example, comprise magnesium diboride and / or an oxide-ceramic superconductor, for example a compound of the type REBa 2 Cu 3 O x (abbreviated to REBCO), where RE stands for a rare earth element or a mixture of such elements.

[0036] In the embodiment with a superconducting strip conductor, the conductor can also be formed, in particular, by a stack of several strip conductors arranged one above the other and / or next to each other. In this embodiment, an even higher current-carrying capacity can be achieved for the individual conductor windings.

[0037] Each individual superconducting strip conductor (which may in particular be part of a stack) has a thickness of only 150 µm or less, in particular even in the range of 100 µm or less. Compared to typical superconducting rotor windings, this embodiment represents a comparatively thin version of the strip conductor. This is advantageously made possible in connection with the present invention because the strip conductor itself does not need to have inherently stable mechanical properties, but rather is mechanically supported by the hollow tube around which the helix is wound. One advantage of such a comparatively thin conductor design is that it allows the comparatively small bending radii required when winding the helical winding to be achieved without damaging the superconducting conductor.The thinner the individual strip conductor is overall, the tighter the bends are typically possible. Another independent advantage of comparatively thin conductor thicknesses is the comparatively higher current density of the resulting winding.

[0038] In order to achieve the aforementioned low overall thickness of the strip conductor, in particular a substrate of the strip conductor and / or one or more stabilizing layers of the strip conductor can be designed to be relatively thin compared to the prior art. For example, the carrier substrate of the strip conductor can have a thickness of only 75 µm or less, in particular even only 50 µm at most or even only 25 µm at most. The optionally present electrical stabilizing layers can, for example, have a combined thickness of only 100 µm or less, in particular even only 50 µm at most or even only 25 µm at most. Such stabilizing layers are typically formed as metallically conductive layers and can cover the layer system comprising the substrate, superconductor layer, and optional additional layers either on one side or on both sides.These stabilizing layers can assume the function of an electrical shunt in the event of a local breakdown of superconductivity. A certain minimum thickness is typically required for this. However, in the context of the present invention, this thickness can be chosen to be significantly smaller than in the prior art, since such a shunt function can also advantageously be performed by an optionally electrically conductive hollow tube.

[0039] In general, the superconducting conductor can have a comparatively small bending radius, at least in sections, which results from the outer diameter of the hollow tube and the selected pitch. This makes it possible to achieve a comparatively compact geometry of the entire coil device and in particular of the winding heads of the coil device. Alternatively or additionally, an overall compact geometry can also be achieved by the hollow tube carrying the helical winding having, at least in sections, a bending radius r of less than 100 mm, in particular even less than 50 mm. Such a tight bend of the supporting hollow tube is particularly expedient in the areas between the axial conductor legs and the terminal connecting legs, because it allows a particularly compact geometry of the winding heads to be achieved. This can be achieved in particular by winding the helix onto a preformed hollow tube.

[0040] According to the invention, the coil device is designed as a coil device for an electrical machine. In particular, it can be a coil device for the rotor of an electrical machine. In particular, it can be a coil device for the excitation winding of such a rotor. In the embodiment as a rotor winding, the aforementioned coil axis is expediently parallel to the central machine axis or the central rotor axis. In such an application of the coil device, the aforementioned advantages of the inventive design are particularly effective.

[0041] In general, the electrical coil device can advantageously also comprise further elements in addition to the hollow tube, the internal coolant channel, and the helical winding applied to the hollow tube. In particular, such additional elements can be radially outwardly located elements that concentrically surround the helical winding and the hollow tube. For example, one or more external holding elements can be arranged radially outside the helical conductor windings. Particularly advantageously, such holding elements can be electrically conductive and thus also have an electrically shielding effect. This can contribute in particular to avoiding electrical alternating current losses in the inner layers.Alternatively or additionally, a radially outer and in particular mechanically prestressed bandage can surround the helical winding (and optionally also one or more such holding elements) and in this way contribute to additional mechanical fixation. Such a bandage can be formed, for example, from an electrically non-conductive material and / or from a material with low thermal conductivity. Even further radially outward, a thermal insulation layer can optionally be provided, which can comprise, for example, an aerogel and / or multi-layer insulation and / or a vacuum space. All of these optionally present layers can be concentric elements, each of which is present within an associated cylinder jacket layer.In this way, one or more of the above-mentioned elements can be used to particularly advantageously achieve high mechanical stability combined with good thermal insulation.

[0042] The coil device can generally have coolant connections that serve to connect the coolant channel located inside the hollow tube with the remaining parts of a coolant circuit. For example, two such coolant connections can be provided for such a hollow tube, one of which can serve as an inlet and the other as an outlet. These connections can be arranged laterally with respect to the annular structure of the hollow tube, in other words, non-tangential to the ring.

[0043] Alternatively, or in addition to the lateral connections, the coil device can advantageously have a connecting piece that serves to connect two end regions of the hollow tube to form a completely closed ring. Such a connecting piece can alternatively be either a hollow tube or an internally closed connecting piece. Depending on the design, this results in either a completely closed, annular channel or only a nearly continuous, annular channel, which then extends, for example, from the inlet to the outlet.

[0044] In general, the helical winding of the superconducting conductor can be electrically closed across the main winding of the coil assembly to form a ring-shaped circuit. This is useful, for example, for operating the coil assembly in a continuous current mode.

[0045] Alternatively, the coil device can also be in the form of an open coil, which can be connected to an external electrical circuit via two electrical connections in the end regions of the coil.

[0046] The hollow tube of the winding support can generally advantageously be formed from a metallic material or comprise a metallic material. A metallic material is particularly advantageous for achieving good thermal coupling of the helical windings to the coolant flowing in the interior. For example, the hollow tube can be formed from copper or at least comprise copper, or alternatively, steel and / or aluminum. Alternatively or additionally, the material of the hollow tube can also comprise a fiber composite material, for example, a fiber-reinforced plastic. A low density can advantageously be achieved with the latter materials.

[0047] According to a preferred embodiment of the rotor, it can have a magnetic pole number n, where n can advantageously assume even values between 2 and 64. For this purpose, the rotor can generally comprise several coil devices according to the invention.

[0048] According to a further preferred embodiment of the rotor, it can have a cooling system for cooling the superconducting conductor to a cryogenic operating temperature, wherein the cooling system is designed to circulate a fluid coolant in the coolant channel of the coil device. This particularly advantageously allows an operating temperature of the superconducting conductor to be achieved that is below the critical temperature of the superconductor used.

[0049] The fluid coolant can be, in particular, liquid hydrogen, liquid helium, liquid neon, liquid nitrogen, liquid oxygen, and / or liquid methane. When using any of these cryogenic coolants, the liquid form can, in principle, be present alongside the gaseous form, and an additional cooling effect can be achieved by evaporating the liquid in the area of the components to be cooled. Thus, it is possible for the cryogenic coolant to circulate inside the hollow tube or in the higher-level cooling circuit, particularly according to the thermosiphon principle and / or in the manner of a heat pipe.

[0050] According to a generally preferred embodiment of the rotor, it can additionally have a rotor core on which the at least one coil device is mechanically held. In particular, this rotor core is then designed to be at a warm operating temperature during operation of the rotor. In the present context, such a warm operating temperature is to be understood as a temperature significantly above the transition temperature of the superconductor, which can in particular be close to or even above room temperature. This embodiment has the advantage that not the entire rotor needs to be cooled, but only one or more locally limited sub-regions in which one or more coil devices according to the invention are arranged.

[0051] In general, the rotor core (regardless of whether it is operated at a warm or cold temperature level) can be made of a soft magnetic material or at least comprise such a soft magnetic material. Such a rotor core is advantageous for magnetic flux guidance in the rotor. Alternatively, the rotor core can also be made of non-magnetic material, for example, aluminum and / or non-magnetic steel.

[0052] To enable the mounting of one or more cryogenic superconducting windings on a warm rotor core, it is expedient to attach the at least one coil device to the warm rotor core via (one or more) low-thermal-conductivity mounting elements. For example, mounting bars made of plastic, in particular fiber-reinforced plastic and / or ceramic, can be used. In principle, however, a metallic material (e.g., steel) can also be used, since the introduced heat is dissipated directly in the cooling tube and does not reach the superconducting conductor.

[0053] Alternatively or additionally, the individual cryogenic superconducting windings may be attached to the warm rotor body via thermally insulating retaining straps, similar to that described in documents US9431864B2 and US8664809B2.

[0054] Furthermore, the rotor core can advantageously have one or more slots to accommodate the coil device(s). For example, one such slot can be provided on the rotor core for each longitudinal leg of the coil device. Alternatively or additionally, slots can also be provided for the terminal connecting legs to guide the corresponding coil parts.

[0055] The invention will now be described by way of some preferred embodiments with reference to the attached drawings, in which: Figure 1 shows a schematic perspective view of a part of a helical winding on a hollow tube, Figure 2 shows a cross-section and a schematic side view of such a helical winding, Figure 3 shows a schematic cross-sectional view of a composite superconducting conductor, Figure 4 shows a schematic cross-sectional view of a helical winding according to a further example, Figure 5 shows a schematic plan view of a coil element according to an example of the invention, Figure 6 shows a schematic perspective view for a coil element on a rotor core, Figure 7 shows a detailed view of the coil element of the Figure 6 Figure 8 shows a schematic representation of a first embodiment of a rotor and Figure 9 shows a schematic representation of a second embodiment of a rotor.

[0056] In the figures, identical or identically acting elements are provided with the same reference symbols.

[0057] Figure 1 shows a schematic perspective view of a partial region of an electrical coil device 1 according to a first example of the invention. Shown is part of a helical winding made of a superconducting conductor 5, which is wound on a hollow tube 3. By way of example, only part of one turn w of the superconducting conductor around the hollow tube is shown here. Overall, however, there are a plurality of such turns w, which form a helical winding. Formed inside the hollow tube 3 is a coolant channel 7, through which a fluid coolant can flow, thus enabling cooling of the superconducting conductor to a cryogenic operating temperature. The hollow tube 3 can be formed from a material with good thermal conductivity, for example copper. The conductor 5 can be electrically insulated from the hollow tube 3, but this is not absolutely necessary.

[0058] Figure 2shows on the left side a cross-sectional view and on the right side a schematic side view of the coil device 1 from the Figure 1 . The cross-sectional view shows that the helical winding has a local axis a, around which the individual sub-elements of the coil device are arranged concentrically. The schematic side view shows a section with approximately two and a half turns w of the helical winding. The section shown can, for example, be part of an overall straight coil leg, and the subordinate helical turns w form subsections on this overall straight coil leg.

[0059] The superconducting conductor 5 from the Figures 1 and 2 can, for example, be composed of several sub-conductors 11. Figure 3shows a schematic cross-sectional representation of such a composite conductor 5, which rests on an outer surface of the hollow tube 3. In this example, the entire conductor 5 is formed by several adjacent stacks of several superconducting strip conductors 11, each one lying one above the other. These individual strip conductors 11 each comprise a carrier substrate and a comparatively thin superconducting layer, as well as optionally further intermediate layers and / or electrical stabilization layers. These individual strip conductors are each comparatively very thin, so that they can be bent with comparatively small bending radii to form the helical winding. By designing the entire conductor 5 with many individual partial conductors 11, a very high current-carrying capacity and thus a high current density is possible.

[0060] Figure 4shows a schematic cross-sectional view of an electrical coil device 1 according to a further example of the invention. This coil device also comprises a helical winding of a superconducting conductor 5 on a hollow tube 3. In addition to the elements already described in Figures 1 and 2In addition to the elements shown, this coil device also comprises further elements which are located radially outward with respect to the conductor 5 and are also arranged concentrically to the local axis a. These are, in the order from the inside to the outside, two holding elements 13, a bandage 15 and a thermal insulation layer 17. In general, each of these elements is only optional, although the radial sequence shown is expedient overall. The holding elements 13 are formed here by two cylindrical half-shells which, in this example, are each made of a metallic material and which mechanically hold the conductor windings w from the outside. At the same time, the electrically conductive property of these holding elements 13 fulfills the function of an electrical damper, so that high-frequency electric fields can be advantageously shielded.The bandage 15 serves for additional mechanical fixation and can, for example, be made of an electrically insulating and thermally poorly conductive material. Further radially outward, there is a thermal insulation layer 17, which can, in particular, comprise an aerogel, a multi-layer insulation, and / or a vacuum-insulating sheath.

[0061] Figure 5 shows a schematic plan view of a coil element 1 according to a further example of the invention. This coil element also comprises a helical winding of a superconducting conductor 5 on a hollow tube 3. Locally, this winding can be arranged similarly to the Figures 1 and 2 The conductor 5 can be constructed similarly to Figure 3 as a composite conductor. The optional layers from the example of the Figure 4can additionally be arranged radially outward around the conductor 5, but they are not shown here for the sake of clarity. It is important that the helical winding, made up of a large number of individual turns w, forms an overarching annular loop. In the example shown, this loop is given by an overall closed rectangular coil shape into which the helix is bent as a whole. In the example shown, this overarching coil shape has two straight axial coil legs 21, each of which runs parallel to the longitudinal axis A of the coil device. In addition, the coil has two axially terminal connecting legs 23, so that overall a closed ring is produced.Electrically, the superconducting conductor can either be closed to form a short-circuit ring, or electrical contact points not shown here can be provided so that the superordinate coil as a whole can be connected to an external circuit.

[0062] The coil device 1 of the Figure 5is not shown to scale. In particular, the length ratio of the individual coil legs can be selected to be significantly different and, for example, the axial coil legs 21 can be significantly longer than shown here. The pitch of the individual conductor turns within the helical winding is also not shown to scale. For the electromagnetic interaction of such a coil device 1 in an electrical machine, it is generally advantageous if the individual conductor sections of the superconducting conductor 5 (and in particular also the corresponding sections of the partial conductors present therein) enclose the smallest possible angle α with the longitudinal axis of the coil. For example, α can generally advantageously be below 79 degrees in the region of the axial coil legs.

[0063] The Figure 5The rectangular coil shown has the shape of a rectangle with rounded corners. The bending radii r in the area of the corners are comparatively small compared to conventional superconducting coils. This is made possible both by the use of comparatively thin strip conductors and by the fact that not the superconducting conductor 5 itself, but rather the hollow tube 3 carrying the helical winding, is bent within this tight bending radius r. The local bending radius of the superconducting conductor 5 within the helical winding can be selected to be different from the bending radius of the superior coil shape. Furthermore, even with a tight bend within the helical winding, an unfavorable bending of the strip conductor—namely, a tight bend within the strip conductor plane—is advantageously avoided.

[0064] The coil element 1 of the Figure 5Additionally, in the left-hand area of the figure, it has a connecting piece 25 and two lateral coolant connections 27. The connecting piece 25 can be made of copper or stainless steel, for example, and serves to connect the two end pieces of the hollow tube, which is formed into a loop, to form an overall closed ring. The coolant connections 27, arranged laterally relative to this ring, serve to introduce the fluid coolant into the internal coolant channel 7 and to discharge it from it.

[0065] Figure 6 shows a schematic perspective view of a coil element 1, which is arranged on a rotor core 31. Only an upper half of the rotor core 31 is shown here. The coil element 1 can be designed in a similar way to the example of Figure 5, whereby the two coil legs 21 are comparatively longer. The coil device 1 is held in a matching groove 43 of the rotor core. Advantageously, the superconducting conductor 5 can be cooled to a cryogenic operating temperature during operation of the rotor by the coolant flowing in the hollow tube. The rotor core 31, on the other hand, can be at a warm temperature level during operation. For this purpose, the suspension of the coil device 1 on the rotor core 31 can be mediated by elements with low thermal conductivity, such as in connection with the Figure 7 This will become even clearer. The small bending radii of the coil assembly 1 and the pronounced rectangular shape ensure that the overall space requirement for the axially terminal connecting legs 23 and thus for the winding heads is minimal in such a rotor. This enables an overall compact design of the rotor.

[0066] In Figure 7 is a detailed view of the coil element 1 of the Figure 6shown. Shown here is the suspension of this coil element 1 on the warm rotor core 31. In order to thermally insulate the cold superconducting conductor 5 and the likewise cold hollow tube 3 from the comparatively warm rotor core 31, a retaining pin 33 made of a material with comparatively low thermal conductivity is provided for mechanical suspension. This retaining pin can extend through the hollow tube 3, as indicated by dashed lines. In addition, there is an optional sleeve 37, which also has low thermal conductivity and acts as a spacer element between the coil device 1 and the rotor core 31. Optionally, one or more spring elements 39 can be provided between the sleeve 37 and the rotor core 31.In the area of the internal coolant channel 7, the retaining pin 33 can be guided through a guide tube 35 running perpendicular to the coolant channel, advantageously avoiding direct contact of the retaining pin 33 with the cryogenic coolant. Overall, the coil element 1 can be fixed to the warm rotor core 31 by a plurality of identical or similarly designed retaining devices. This achieves a mechanically stable and thermally decoupled suspension.

[0067] Figure 8shows a schematic representation of an embodiment of the rotor 41 according to the invention. Shown is a plan view of one of the axial end regions of the rotor. The rotor 41 shown comprises a rotor core 31, which has a substantially cylindrical shape and a central rotor axis B. This rotor 41 has two coil devices 1 according to the invention, which are each inserted in corresponding grooves 43 of the rotor core 31. The design of the coil device 1 can be overall similar to the previous examples. The suspension can also be similar to that described in connection with Figure 7 In the example of the Figure 8 the two coil devices 1 are each designed as flat rectangular coils, wherein the terminal coil legs 23 are each straight and lie within a common coil plane.

[0068] Figure 9shows a similar schematic diagram for an alternative embodiment of the rotor. This rotor 41 also has a warm rotor core 31 and two coil devices with cryogenically operated superconductors arranged thereon. In contrast to, for example, the Figure 8 Here, the axially terminal connecting legs are not designed as straight conductor legs, but as curved conductor legs with a constant bending radius. Therefore, the coil devices 1 each have a cylindrical basic shape.

[0069] The two different in the Figures 8 and 9 The basic shapes shown for the superordinate coil elements 1 can be easily realized by appropriately bending the hollow tubes supporting the windings. In principle, the appropriate shaping of these hollow tubes is possible either before or after the application of the helical winding. List of reference symbols

[0070] 1Coil assembly 3Hollow tube 5Superconducting conductor 7Coolant channel 11Individual conductor 13Holding element 15Bandage 17Thermal insulation layer 21Axial coil legs 23Terminal connecting legs 25Connecting piece 27Lateral coolant connections 31Rotor core 33Holding pin 35Guide tube 37Sleeve 39Spring element 41Rotor 43Groove αAngle aLocal helix axis ALongitudinal axis of the coil BRotor axis LLength of the coil rBending radius of the hollow tube wMinor turn of the helix WDepth of the coil

Claims

1. Electrical coil device (1) of an electric machine, comprising - a winding carrier which is formed from an elongate hollow tube (3) and which is shaped in the manner of a ring, such that, overall, a superordinate loop of the coil device (1) is formed by the ring shape of the winding carrier, - and a winding which is applied to the winding carrier and which is composed of a superconductive conductor (5), - wherein the superconductive conductor (5) is wound in a multiplicity of individual turns (w) helically around the hollow tube (3), such that the ring shape of the winding carrier results in at least one superordinate turn of the overall helix, - and wherein the interior of the hollow tube (3) is designed as a coolant channel (7) for the circulation of a fluid coolant, wherein the superconductive conductor (5) comprises at least one strip conductor (11) and the thickness of the strip conductor (11) is at most 150 µm.

2. Coil device (1) according to Claim 1, which has a longitudinal axis (A) and which has two axial coil members (21) which extend parallel to the longitudinal axis (A).

3. Coil device (1) according to Claim 2, in which, within the axial coil members (21), the superconductive conductor (5) forms a local angle α of at most 79 degrees with the coil axis (A).

4. Coil device (1) according to Claim 2 or 3, which, in addition to the two axial coil members (21), has two axially end-side connecting members (23) which are each formed as straight members.

5. Coil device (1) according to Claim 2 or 3, which, in addition to the two axial coil members (21), has two axially end-side connecting members (23) which are each formed as bent members.

6. Coil device (1) according to any of the preceding claims, in which the hollow tube (3) has a round cross-sectional shape.

7. Coil device (1) according to any of the preceding claims, in which the hollow tube (3) has an inner diameter of at most 50 mm.

8. Coil device (1) according to any of the preceding claims, in which the hollow tube (3) has, at least in certain portions, a bend radius of less than 100 mm.

9. Rotor (41) for an electric machine, having at least one coil device (1) according to any of the preceding claims.

10. Rotor (41) according to Claim 9, which has a cooling system for cooling the superconductive conductor (5) to a cryogenic operating temperature, wherein the cooling system is configured to circulate a fluid coolant in the coolant channel (7) of the coil device (1).

11. Rotor (41) according to any of Claims 1 to 9, which additionally has a rotor core (31) on which the at least one coil device (1) is mechanically held, wherein the rotor core (31) is designed to be kept at a warm operating temperature during the operation of the rotor (41).

12. Rotor (41) according to any of Claims 9 to 11, in which the rotor core (31) has at least one groove (43) for receiving the coil device (1).