Abstract
A rotor for an electrical machine with a central rotor axis, the rotor includes at least one superconducting coil arrangement, a cooling system for cooling the coil arrangement to a cryogenic operating temperature, and a carrying body which mechanically carries at least one coil arrangement from a radially inner side of the coil arrangement. The carrying body has a substantially cylindrical outer contour. The carrying body is predominantly composed of an amagnetic material which has a density of at most 4.6 g/cm3 and a thermal conductivity of at least 10 W/(m-K). The carrying body is designed to thermally couple the superconducting coil arrangement to the cooling system. An electrical machine has a rotor of this kind.
Claims
1.-15. (canceled)
16. A rotor for an electric machine having a central rotor axis, comprising: at least one superconducting coil assembly; a cooling system for cooling the coil assembly to a cryogenic operating temperature; and a carrying body which from a radially inward side of the coil assembly mechanically supports the at least one coil assembly; wherein the carrying body has a substantially cylindrical external contour; wherein the carrying body is composed largely of a non-magnetic material which has a density of at most 4.6 g/cm3 and a thermal conductivity of at least 10 W/(m-K); wherein the carrying body is designed for thermally coupling the superconducting coil assembly to the cooling system; and wherein the carrying body has an inner cylinder and an outer cylinder, wherein the outer cylinder radially surrounds the inner cylinder and on the external side of the former mechanically supports the at least one coil assembly.
17. The rotor as claimed in claim 16, wherein the non-magnetic material of the carrying body comprises aluminum.
18. The rotor as claimed in claim 16, wherein the non-magnetic material of the carrying body comprises a fiber-composite material.
19. The rotor as claimed in claim 16, wherein the carrying body when operating the rotor is designed to be at a cryogenic operating temperature.
20. The rotor as claimed in claim 16, wherein the carrying body comprises at least one coolant duct embedded in the former for transporting a fluid coolant.
21. The rotor as claimed in claim 16, wherein the carrying body in the region of the cylindrical external contour thereof is designed so as to be fluid-tight.
22. The rotor as claimed in claim 16, wherein at least one coolant duct in the contact region between the inner cylinder and the outer cylinder is formed by at least one elongate recess in the inner cylinder and/or in the outer cylinder.
23. The rotor as claimed in claim 16, wherein the carrying body is produced by an additive manufacturing process.
24. The rotor as claimed in claim 16, wherein the carrying body in addition to the mentioned non-magnetic material has a comparatively minor proportion of a ferromagnetic material.
25. The rotor as claimed in claim 16, wherein the carrying body as a sub-face of the external face thereof has at least one radially external bearing face on which the at least one coil assembly is mechanically held.
26. The rotor as claimed in claim 16, said rotor having a plurality of superconducting coil assemblies.
27. An electric machine, comprising: a rotor as claimed in claim 16, and a stator which is disposed so as to be stationary.
28. The electric machine as claimed in claim 27, wherein the external diameter of the rotor is at least 1 m.
29. The electric machine as claimed in claim 27, said electric machine being adapted for a rotating speed of the rotor of 1000 revolutions per minute or less.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] The invention will be explained hereunder by means of some advantageous exemplary embodiments with reference to the appended drawings in which:
[0048] FIG. 1 shows a schematic illustration of an electric machine having a rotor and a stator in a schematic longitudinal section;
[0049] FIG. 2 shows an electric machine in the schematic cross section;
[0050] FIG. 3 shows a superconducting coil assembly 15 in a schematic perspective illustration;
[0051] FIG. 4 shows a fragment of a machine in a schematic cross-sectional illustration;
[0052] FIG. 5 and FIG. 6 show similar fragments of machines according to two further alternative embodiments; and
[0053] FIG. 7 shows a schematic perspective illustration of a superordinate cooling duct system according to a further exemplary embodiment.
DETAILED DESCRIPTION OF INVENTION
[0054] Identical elements or elements with equivalent functions are provided with the same reference signs in the figures.
[0055] A schematic longitudinal section of an electric machine 1 along the central axis A of the machine is shown in FIG. 1. This herein is a machine according to a first exemplary embodiment of the invention. The electric machine comprises a rotor 7 and a stator 3. The rotor 7 by means of a rotor shaft 9 is mounted so as to be rotatable about a rotation axis A, the latter corresponding to the central machine axis A. To this end, the rotor shaft 7 by way of the bearings 10 is supported in relation to the machine housing 11. The electric machine can in principle be a motor or a generator, or else a machine which can be selectively operated in both modes.
[0056] The stator 3 has a plurality of stator windings 4. Above all, the axially internal regions of the stator windings 4 between the axially end-proximal coil ends interact in an electromagnetic manner with an electromagnetic field of the rotor 7 in the operation of the electric machine 1. This interaction takes place across an air gap 6 which in the radial terms lies between the rotor 7 and the stator 3. The stator windings 4 in the example shown are embedded in grooves of a stator lamination stack 5.
[0057] The electric machine of FIG. 1 in the rotor 7 has a superconducting winding having at least one superconducting coil assembly. This is advantageously a rotor winding with n poles and with n such superconducting coil assemblies. To this end, substantial parts of the rotor 7 in operation can be cooled to a cryogenic temperature which is below the transition temperature of the superconductor used. This operating temperature can be approximately 20 K, for example. The cooling can be achieved using a cooling system which is not illustrated in more detail in the image. The cryogenic components should moreover be thermally insulated in relation to the warm environment. In the exemplary embodiment shown this thermal insulation (not illustrated in more detail here) is in the external region of the rotor 7 such that the latter is thermally insulated in relation to the warm stator 3 which in radial terms lies further outside. The individual superconducting coil assemblies in the machine 1 of FIG. 1 are to be disposed on a cylindrical carrying body 13 in the radial external region of the rotor 7. Said individual superconducting coil assemblies are not plotted in FIG. 1 for reasons of clarity. The specific disposal and mechanical mounting of said individual superconducting coil assemblies is however to become evident in the context of the following figures.
[0058] FIG. 2 shows a similar electric machine according to one exemplary embodiment of the invention in a schematic cross section, thus having a section plane which is perpendicular to the central axis A. This machine can in principle be constructed in a manner similar to the machine shown in FIG. 1. Said machine also has an external stator 3 and are radially internal rotor 7. The rotor in this example has a superconducting rotor winding with eight poles, said rotor winding comprises eight individual coil assemblies 15. Each of these coil assemblies 15 comprises two axially running conductor limbs 17 and overall configures a coil shape in the manner of a racetrack. For example, each of these coil assemblies 15 can have a basic shape in the manner of a racetrack, similar to that shown in FIG. 3. For example, each of these coil assemblies can be wound from a superconducting tape conductor and have one or a plurality of sub-coils in the form of superconducting flat coils. As is indicated in FIG. 2, each of these coil assemblies can have a step-type profile in the cross section such that the circular-cylindrical external contour of the rotor on the external side is replicated by the respective coil shape. Alternatively however, the entire coil assembly 15 can be a superordinate flat coil having two opposite planar main faces, as is illustrated in FIG. 3.
[0059] The eight coil assemblies 15 in the machine in FIG. 2 in the exemplary embodiment shown are disposed on the radially external surface of an overall cylindrical carrier body 13. This carrying body 13 is configured in the form of a hollow cylinder having an overall circular basic structure. The carrying body 13 in this exemplary embodiment is formed substantially from aluminum or an aluminum-containing alloy. Said carrying body 13 in the example shown is illustrated as an integral cylinder; alternatively however, said carrying body 13 can also be assembled from a plurality of sub-components. In order to be able to mechanically support the individual coil assemblies 15, the carrying body in the region of the external face thereof has a corresponding number of flat spots such that a planar bearing face is available for each of the coil assemblies. These bearing faces have in each case an annular basic structure which matches the shape of the coil assembly 15. A protrusion which in the manner of a coil core fills the internal part of the respective coil assembly and thus mechanically supports the latter from the inside herein is formed from the material of the carrying body 13 in the interior of the respective ring.
[0060] The material of the carrying body 13 is chosen such that the carrying body in mechanical terms is sufficiently strong, such that said carrying body has a comparatively minor density, and that the individual coil assemblies 15 in thermal terms are sufficiently well coupled to a cooling system which is not illustrated in more detail here. On account of being coupled to the cooling system, the carrying body 13 per se is also at a cryogenic temperature level. The cooling of the individual coil assemblies is facilitated by the thermal conductivity of the material of the carrying body 13. To this end, the carrying body 13 can optionally have one or a plurality of cooling ducts through which a fluid coolant can flow. These coolant ducts are not explicitly illustrated in FIG. 2 but will still be described in more detail in the context of the following examples.
[0061] FIG. 4 thus shows a partial view of a rotor 7 according to a further exemplary embodiment of the invention, likewise in a schematic cross section. A small sub-portion of the stator 3 as well as the air gap 6 between the rotor and the stator are likewise illustrated in FIG. 4. Shown in terms of the rotor 7 is the fragment in the region of approximately one magnetic pole, thus the region of a complete coil assembly 15 having the two axial limbs thereof. Furthermore, another individual axial limb of an adjacent coil assembly is shown. The individual coil assemblies 15 here too are disposed on the external side of the cylindrical carrying body 13. Each of the coil assemblies 15 herein is configured as a flat coil in the manner of a racetrack, wherein each of the axial coil limbs has a rectangular cross section. The radially internal surface of the respective coil assembly 5 herein mechanically contacts a matching planar bearing face on the radially external side of the cylindrical carrying body 13. These planar bearing faces in turn are in each case configured as flat spots of the circular-cylindrical basic body. The carrying body 13 in the example of FIG. 4 is formed by two cylindrical bodies which are nested inside one another, specifically an inner cylinder 21 and an outer cylinder 23. The outer cylinder 23 herein, besides the flat spots for the bearing faces of the coil assemblies, also has a plurality of protrusions 25 which in the manner of a coil core fill in each case the internal region of the individual flat coils in the manner of racetracks. The cylindrical inner cylinder 21 and the cylindrical outer cylinder 23 are nested in one another in a substantially exact fit. Said inner cylinder 21 and said outer cylinder 23 are made as individual components but may thereafter have been fixedly connected to one another in mechanical terms. One or a plurality of recesses by way of which coolant ducts for the flow of fluid coolant are defined can be provided in one of the two cylinders, or else in both cylinders, in the region of the contact face between said cylinders. In the example of FIG. 4, such coolant ducts 27 are formed by corresponding recesses on the external face of the inner cylinder 21, for example. Alternatively or additionally, said coolant ducts 27 can also be formed by similar recesses on the internal face of the external cylinder 23. The individual duct segments 27 in the example of FIG. 4 advantageously run at a relatively minor spacing from the coil limbs 17 so as to be able to cool the latter as effectively as possible. The duct segments 27 shown here are correspondingly duct segments which are aligned in the axial direction. The superordinate duct system within the entire carrying body 13 branches such that the coolant can flow in parallel through the individual duct segments 27. Alternatively or additionally, a serial flow of coolant through individual such axial segments can in principle also be implemented. It is essential merely that a transport of coolant through the ducts (according to a closed or else an open circuit) is affected by means of a superordinate cooling system, and the coil assemblies 15 are thus effectively cooled to a cryogenic temperature by way of the comparatively positive thermal conductivity of the carrying body 13. The embodiment shown, having two sub-cylinders which are pushed inside one another, enables such a cooling duct system to be configured in a simple manner.
[0062] In the machine according to the exemplary embodiment of FIG. 4 the carrying body 13 is at a cryogenic operating temperature while the radially external stator 3 is operated at a significantly higher temperature. In order for the thermal insulation required for that purpose to be guaranteed, a vacuum chamber V is situated in the region between the carrying body 13 and the stator 3. In order for the configuration a sufficiently good vacuum to be enabled here, this vacuum chamber V has to be sufficiently sealed in relation to the coolant chamber within the coolant ducts 27. In the example of FIG. 4, this sealing is guaranteed by the carrying body per se and here in particular on account of the outer cylinder 23.
[0063] As an alternative to the embodiment having two sub-cylinders illustrated in FIG. 4, the carrying body 13 can in principle also be configured in an overall integral manner, and similar coolant ducts 27 can be embedded in the interior of the cylinder wall. Such a structure can be formed by an additive manufacturing method, for example.
[0064] In the example of FIG. 4, the inner cylinder 21 and the outer cylinder 23 can in each case be formed from a homogenous non-magnetic material having the properties stated further above in terms of density and thermal conductivity. Here too, this can again be aluminum, an aluminum alloy, or a fiber-reinforced composite material, for example. Guiding of the magnetic flux through the carrying body is not necessarily required by virtue of the high current-carrying capability in the superconducting conductors of the individual coil assemblies 15. Accordingly, the carrying body in this instance can be of a comparatively simple construction and be embodied so as to be correspondingly light.
[0065] A similar sub-region of the electric machine 1 according to a further exemplary embodiment of the invention is shown in FIG. 5. In a manner similar to the example of FIG. 4, the carrying body 13 here too is assembled from an inner cylinder 21 and an outer cylinder 23. Here too, a plurality of duct segments 27 are formed between these two sub-cylinders, said duct segments 27 in this case being formed by corresponding recesses in the outer cylinder 23, for example. The outer cylinder 23 here too, besides the flat spots for the contact faces of the coil assemblies, has a corresponding number of protrusions 25 which fill in each case the internal regions of the coil assemblies 15. By contrast to the preceding example, these protrusions 25 here are however formed from a ferromagnetic material. In a manner analogous to the preceding example, the inner cylinder 21 and the outer cylinder 23 are again in each case formed from a non-magnetic material having the mentioned further properties. The two cylinders 21 and 23 conjointly form the major proportion of material of the entire carrying body 13. Therefore, the entire carrying body 13 here too is formed largely from non-magnetic material. The ferromagnetic protrusions 25 which are additionally present in this hybrid form serve for additional guiding of the magnetic flux in the region of the local coil cores. The flux chain between the rotor 7 and the stator 3 can be even further improved on account of said protrusions 25. In the context of the present invention it is essential merely that the carrying body 13 in its majority is formed from non-magnetic material and that there is contact with non-magnetic material in particular in the region of the radially internal bearing faces for the coil assemblies. Here too, it is this non-magnetic material (specifically the non-magnetic material of the outer cylinder 23) which facilitates the thermal coupling of the coil assemblies 15 to the coolant flowing in the individual cooling ducts 27.
[0066] A similar sub-region of an electric machine 1 according to a further exemplary embodiment of the invention is shown in FIG. 6. As opposed to the preceding examples, the carrying body 13 here has only a single carrying cylinder 24 as a substantial load-bearing element for the coil assemblies. Here too, this carrying cylinder is formed from a corresponding non-magnetic material having the additional properties described further above. The carrying cylinder 24 in this example has been produced by an additive manufacturing method, and a plurality of cooling duct segments 27 are embedded in the interior of this cylinder. Here too, the individual duct segments are situated in the proximity of the coil limbs to be cooled such that the latter can be effectively cooled.
[0067] In a manner similar to the preceding example, the non-magnetic carrying cylinder 24 here too on the radial external side thereof is provided with a plurality of protrusions 25 from ferromagnetic material. Here too, each of the present coil assemblies in the interior thereof is in each case filled by such a ferromagnetic protrusion 25. As opposed to the preceding example, these ferromagnetic protrusions 25 for improved guiding of the flux additionally have roof-type overhangs 26 which according to the principle of a salient pole further amplify the guiding of flux between the rotor and the stator.
[0068] FIG. 7 shows a schematic perspective illustration of the superordinate cooling duct system 31 such as can be used in various embodiments of the electric machine in the interior of the carrying body 13. Such a cooling duct system can be implemented as has been described above, either by corresponding recesses between two cylinders which are pushed inside one another, or else by an additive manufacturing method within an integral cylinder. The cooling duct system 31 illustrated has a type of cylindrical cage structure. Said cooling duct system 31 comprises a plurality of dissimilar duct segments through which the cryogenic coolant can be distributed such that the latter in the various regions of the rotor can in each case reach the proximity of the individual coil assemblies. The cooling duct system illustrated here overall comprises a plurality of axial duct segments 31a as well as a plurality of annular duct segments 31b which extend in the circumferential direction, as well as a plurality of radial duct segments 31c. This superordinate duct system 31 can be supplied with a fluid cryogenic coolant by means of a central inflow and outflow 33 which are not illustrated in more detail here. In principle, either a common inflow and outflow is possible herein, or else an inflow and an outflow in separate configurations. For example, a common inflow and outflow can be formed in the central region of the rotor shaft, and the cryogenic coolant overall can circulate through the cage structure in the manner of a thermosiphon, and reach the direct proximity of the individual coil assemblies of the rotor through the corresponding branches and the plurality of segments running in parallel (in particular the parallel axial segments 31a).
