ROTOR, MACHINE AND METHOD FOR MAGNETIZATION

Abstract

The disclosure relates to a rotor for an electrical machine, having a central rotor axis. The rotor includes a rotor carrier and at least one superconducting permanent magnet carried mechanically by the rotor carrier. The rotor further includes a magnetization device having at least one superconducting coil element which surrounds the superconducting permanent magnet and which is suitable for magnetization of the superconducting permanent magnet. Furthermore, an electrical machine including such a rotor and a method for magnetization of at least one superconducting permanent magnet of such a rotor are disclosed.

Claims

1. A rotor for an electrical machine with a central rotor axis, the rotor comprising: a rotor support; at least one superconducting permanent magnet mechanically supported by the rotor support; and a magnetization apparatus having at least one superconducting coil element surrounding the at least one superconducting permanent magnet and configured to magnetize the at least one superconducting permanent magnet.

2. The rotor of claim 1, wherein the at least one superconducting permanent magnet comprises a stack of superconducting strip conductors, a superconducting bulk element, or a combination thereof.

3. The rotor of claim 1, wherein the at least one superconducting permanent magnet is a plurality of superconducting permanent magnets, and wherein each superconducting permanent magnet of the plurality of superconducting permanent magnets is associated either individually or combined in groups with individual magnetic poles of the rotor.

4. The rotor of claim 3, wherein the magnetization apparatus has a plurality of superconducting coil elements, and wherein each superconducting coil element of the plurality of superconducting coil elements encloses either one superconducting permanent magnet or a group of superconducting permanent magnets of the plurality of superconducting permanent magnets.

5. The rotor of claim 1, wherein the at least one superconducting coil element has two axially oriented straight coil legs arranged azimuthally adjacent to the associated superconducting permanent magnet.

6. The rotor of claim 1, wherein the magnetization apparatus has a contacting apparatus for electrically connecting the at least one superconducting coil element to an external current source, and wherein the contacting apparatus is configured to connect to the external current source only in a stationary state of the rotor.

7. The rotor of claim 1, wherein the at least one superconducting coil element comprises a low-temperature superconducting material.

8. The rotor of claim 1, wherein the at least one superconducting coil element comprises a high-temperature superconducting material.

9. The rotor of claim 1, further comprising: a cooling apparatus configured to cool both the at least one superconducting permanent magnet and the at least one superconducting coil element to an operating temperature below a critical temperature of a respective superconducting material of the at least one superconducting permanent magnet and the at least one superconducting coil element.

10. The rotor of claim 9, wherein the superconducting permanent magnet and the associated superconducting coil element are thermally coupled such that, in a normal operating state of the cooling apparatus, the superconducting permanent magnet and the superconducting coil element are together cooled to a cryogenic operating temperature.

11. The rotor of claim 9, further comprising: a heating element in a region of the superconducting permanent magnet, wherein the superconducting permanent magnet and the associated superconducting coil element are thermally decoupled such that the superconducting coil element is configured to be brought into a superconducting state by cooling with the cooling apparatus, while the superconducting permanent magnet is brought into a warm, normally conducting state by heating with the heating element.

12. An electrical machine comprising: a stator arranged in a fixed manner, and a rotor with a central rotor axis, the rotor comprising: a rotor support, at least one superconducting permanent magnet mechanically supported by the rotor support; and a magnetization apparatus having at least one superconducting coil element surrounding the at least one superconducting permanent magnet and configured to magnetize the at least one superconducting permanent magnet.

13. A method for magnetizing at least one superconducting permanent magnet of a rotor, the method comprising: providing a rotor having a rotor support, at least one superconducting permanent magnet mechanically supported by the rotor support, and a magnetization apparatus having at least one superconducting coil element surrounding the at least one superconducting permanent magnet; cooling the magnetization apparatus of the rotor to an operating temperature below a critical temperature of a superconducting material of the at least one superconducting coil device; connecting the magnetization apparatus to an external current source in a stationary state of the rotor; feeding a magnetization current into the at least one superconducting coil element of the magnetization apparatus, whereby a magnetic flux is formed in the at least one superconducting permanent magnet; and disconnecting the magnetization apparatus from the external current source.

14. The method of claim 13, wherein the feeding of the magnetization current is carried out in a state of the rotor in which the at least one superconducting permanent magnet has also been cooled to a cryogenic temperature below the critical temperature of a superconducting material of the at least one superconducting permanent magnet.

15. The method of claim 13, wherein the feeding of the magnetization current is carried out in a state of the rotor in which the at least one superconducting permanent magnet is at a temperature above a critical temperature of a superconducting material of the at least one superconducting permanent magnet.

16. The rotor of claim 1, wherein the magnetization apparatus has a plurality of superconducting coil elements, and wherein each superconducting coil element of the plurality of superconducting coil elements encloses a superconducting permanent magnet of the at least one superconducting permanent magnet.

17. The rotor of claim 6, further comprising: a cooling apparatus configured to cool both the at least one superconducting permanent magnet and the at least one superconducting coil element to an operating temperature below a critical temperature of a respective superconducting material of the at least one superconducting permanent magnet and the at least one superconducting coil element.

18. The rotor of claim 17, wherein the superconducting permanent magnet and the associated superconducting coil element are thermally coupled such that, in a normal operating state of the cooling apparatus, the superconducting permanent magnet and the superconducting coil element are together cooled to a cryogenic operating temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The disclosure will be described below using two exemplary embodiments with reference to the appended drawings, in which:

[0051] FIG. 1 depicts a schematic cross section of a first exemplary embodiment of an electrical machine and

[0052] FIG. 2 depicts a schematic cross section of a second exemplary embodiment of an electrical machine.

[0053] In the figures, elements that are identical or have the same function are provided with the same reference signs.

DETAILED DESCRIPTION

[0054] FIG. 1 shows a schematic cross section of an electrical machine 1, that is to say shows the electrical machine perpendicularly to the central axis A. The machine includes an external stator 3, which is arranged in a fixed manner, and an internal rotor 5 which is rotatably mounted about the central axis A. The electromagnetic interaction between the rotor 5 and the stator 3 takes place across the air gap 6 situated between them. The machine is a permanently excited machine which has a plurality of superconducting permanent magnets 9 in order to form an excitation field in the region of the rotor. In the cross section of FIG. 1, here by way of example four permanent magnets of this type are distributed over the circumference of the rotor. They are arranged in corresponding radially outer recesses of a rotor support 7, wherein the rotor support 7 mechanically supports the permanent magnets 9. However, yet further permanent magnets than the four shown here may also be present in the axial direction, not shown here, wherein the number of magnetic poles of the electrical machine is not increased by such an axial subdivision however.

[0055] The rotor support 7, together with the permanent magnets 9 held thereon, is cooled by a cooling apparatus to a cryogenic operating temperature, which is below the critical temperature of the superconductor material used in the permanent magnets. In order to maintain this cryogenic temperature, the rotor support 7 and the permanent magnets 9 are arranged in the interior of a cryostat 11 together. There is an annular vacuum space V for thermal insulation between the cryostat and the rotor support 7.

[0056] In the exemplary embodiment in FIG. 1, the individual permanent magnets 9 are each in the form of a strip conductor stack composed of individual superconducting strip conductors 10. In this case, a respective plurality of such superconducting strip conductors 10 are stacked one on top of the other in a radial direction.

[0057] The four individual permanent magnets 9 are each surrounded by an associated superconducting coil element 19. The permanent magnets 9 are thus each arranged in the center of such a coil element 19. The individual coil elements 19 are here in the form of, for example, rectangular coils. Each of the coil elements 19 has two straight axial coil legs, which in the cross-sectional representation of FIG. 1 are shown azimuthally next to the respective permanent magnets 9 on both sides. In the axial end regions, not shown here, of the rotor, these axial coil legs associated in pairs are in each case closed by terminal connecting legs to form an annular coil. Overall, each of the coil elements 19 is thus positioned in an annular manner around an associated permanent magnet 9, wherein in each case both the radially inner region and the radially outer region of the permanent magnets 9 remain free.

[0058] In the example of FIG. 1, the superconducting coil elements 19 are arranged very closely next to the associated permanent magnets 9. In some circumstances, the superconducting coil elements 19 may even be in contact with one another. In the example of FIG. 1, superconducting coil elements 19 are in any case thermally closely coupled with one another, so that they may jointly be cooled to a cryogenic temperature level by the cold rotor support 7. A thermal coupling layer may optionally also be arranged between the permanent magnets 9 and the associated coil element 19, as is shown here by way of example for the permanent magnet shown at the top.

[0059] Not only the permanent magnets 9 but also the superconducting coil elements 19 are cooled to a cryogenic temperature below the critical temperature of the respective superconducting material by the cooling apparatus of the rotor.

[0060] In order to magnetize the superconducting permanent magnets 9, a magnetization current is fed into the individual associated coil elements 19. A magnetic flux is thereby generated in the inner superconducting permanent magnets 9. This magnetic flux is permanently maintained even after the magnetization current has been switched off, as long as the permanent magnets 9 remain in the superconducting state.

[0061] Feeding in of the magnetization current takes place during a magnetization phase in which the rotor is in a stationary state. In this stationary state, the superconducting coil elements 19 may be connected via a contacting apparatus, not shown here, to a superordinate current circuit and, in particular, to a fixed external current source. This current source is thus located outside the rotor 5. The contacting apparatus is not provided for the electrical contacting of the rotating rotor but only for the electrical contacting of the stationary rotor. The coil elements 19 form together a magnetization apparatus of the rotor. In this example, they are electrically connected to one another in series. Thus, during the feeding in, a uniform magnetization current flows into all four coil elements. The number of windings of the individual coil elements is also chosen so as to be mutually equal. As a result, a mutually equal magnetic flux profile is imprinted into the individual permanent magnets 9.

[0062] FIG. 2 shows a schematic cross section of an alternative embodiment of an electrical machine 1. This machine is configured similarly to the machine of FIG. 1 in principle. In contrast to FIG. 1, however, the individual permanent magnets 9 are thermally slightly decoupled from the respective associated coil element 19. For this purpose, a thermal insulation layer 21 is in each case arranged between these two elements. This has the effect that, during the magnetization phase, the permanent magnets 9 may be maintained at a slightly higher temperature level, at which the superconducting material present here is maintained above the critical temperature. In order to make such relative warming possible, additional heating elements 22 are arranged in the region of the permanent magnets 9. In the example shown, these heating elements are heating foils which are arranged on the radially inner side and the radially outer side of the respective permanent magnets. These sides are not enclosed by the associated coil elements 19 and are therefore available for local warming.

[0063] In order to magnetize the permanent magnets 9 in the example of FIG. 2, the procedure is similar, in principle, to that already described in connection with FIG. 1. However, before the magnetization current is fed in, the permanent magnets 9 are here heated locally by the heating elements 22 to such an extent that they are no longer superconducting. Only after the magnetic flux has been imprinted into the permanent magnets 9 are they also cooled to a cryogenic temperature below the critical temperature of the superconducting material used here.

[0064] Merely in order to illustrate that, instead of the superconducting strip conductor stacks, different configurations for the permanent magnets are possible, the permanent magnet shown on the right in FIG. 2 is shown by way of example as a superconducting bulk element 9a. In a real rotor, however, the individual permanent magnets are advantageously of the same form.

[0065] In both exemplary embodiments, comparatively simple magnetization of the permanent magnets 9 is thus made possible by the superconducting coil elements 19 arranged in the region of the rotor, wherein the coil elements 19, in a stationary state of the rotor 5, are connected to a fixed external current source. After disconnection from this fixed current source, the rotor may for the first time or again be set into a rotating state. The superconducting permanent magnets 9 thereby remain in a permanently magnetized state, as long as they are maintained below the critical temperature of the superconducting material used here.

[0066] Although the disclosure has been illustrated and described more specifically in detail by the exemplary embodiments, the disclosure is not restricted by the disclosed examples and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the disclosure.

[0067] It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present disclosure. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.

LIST OF REFERENCE DESIGNATIONS

[0068] 1 Electrical machine [0069] 3 Stator [0070] 5 Rotor [0071] 6 Air gap [0072] 7 Rotor support [0073] 9 Superconducting permanent magnet [0074] 9a Superconducting bulk element [0075] 10 Strip conductor [0076] 11 Cryostat wall [0077] 13 Thermal coupling layer [0078] 19 Superconducting coil element [0079] 21 Thermal insulation layer [0080] 22 Heating element [0081] A Central rotor axis [0082] N Magnetic north pole [0083] S Magnetic south pole [0084] V Vacuum space