Synchronous Superconductive Rotary Machine Having a Consecutive Pole Arrangement

Abstract

The invention relates to a synchronously excited rotary machine with a superconductive rotor comprising a plurality of projecting first pole units of a magnetic material and a plurality of second pole units having superconductive coils wrapped around a core element of a magnetic material. Each second pole unit is positioned between two adjacent first pole units. The second pole units are spaced apart from aback iron and the first pole units via a plurality of thermally insulating support elements, wherein this spacing is evacuated so that it acts as magnetic air gap. An enclosed housing is provided on the back iron in which the first and second pole units are arranged, where-in the superconductive coils of the second pole units are in fluid communication with a cooling system. The first pole units and back iron are operated at an ambient temperature while the second pole units are operated at a cryogenic operating temperature.

Claims

1. A synchronous superconductive rotary machine comprising: a rotor arranged rotatably relative to a stator, wherein the rotor comprises at least a back iron configured to be connected to a drive axis, e.g. via a rotor structure, the rotor further comprises a plurality of first pole units arranged on the back iron, the first pole units extend in at least a radial direction relative to the back iron, wherein a gap, e.g. a magnetic air gap, is formed between a side surface of one of said first pole units and a corresponding side surface of an adjacent first pole unit in which at least one second pole unit is arranged, wherein the at least one second pole unit comprises at least one superconductive rotor coil, the at least one rotor coil is configured to interact with at least one stator coil arranged in the stator via an electromagnetic field when the rotor is rotated relative to the stator, wherein the first pole units and the at least one second pole unit are arranged inside an evacuated chamber defined by a housing, wherein the first pole units and the back iron are configured to be operated at an ambient temperature, and wherein the at least one second pole unit is configured to be operated at a cryogenic temperature, wherein the at least one second pole unit is spaced apart from the back iron by means of at least one thermally insulating support element so a first magnetic air gap is formed between the at least one second pole unit and the back iron and at least a second magnetic air gap is formed between the at least one second pole unit and at least one front wall of the housing.

2. A synchronous superconductive rotary machine according to claim 1, wherein the first pole units are shaped as magnetic pole elements projecting from an outer surface of the back iron, wherein said magnetic pole elements have a radial height which at least corresponds to the thickness of the at least one second pole unit.

3. A synchronous superconductive rotary machine according to claim 1, wherein the at least one front wall is facing the stator and the housing further comprises at least one end wall connected to the at least one front wall, wherein the at least one end wall is further connected to at least one of the back iron and the rotor structure.

4. A synchronous superconductive rotary machine according to claim 1, wherein the at least one second pole unit comprises at least one thermal shield surrounding the respective second pole unit, wherein the at least one thermal shield is actively cooled by means of a first cooling system.

5. A synchronous superconductive rotary machine according to claim 4, wherein the first cooling system is connected to the at least one thermal shield by means of a set of heat transferring elements configured to remove heat from the at least one thermal shield, wherein at least one of the heat transferring elements is further connected to said at least one thermally insulating support element via another heat transferring element.

6. A synchronous superconductive rotary machine according to claim 1, wherein the at least one second pole unit comprises at least one thermal shield surrounding the respective second pole unit, wherein the at least one thermal shield is a passive thermal shield comprising at least one heat insulating layer.

7. A synchronous superconductive rotary machine according to claim 1, wherein the superconductive coils are made of a high temperature superconductive material and configured to be operated at a cryogenic operating temperature of no more than 70 K.

8. A synchronous superconductive rotary machine according to claim 7, wherein the at least one second pole unit further comprises at least: at least one spacer element arranged between a core element and the superconductive coils.

9. A synchronous superconductive rotary machine according to claim 1, wherein the at least one thermally insulating support element has a thermal conductivity below 40 W/.sub.m.Math.K.

10. A synchronous superconductive rotary machine according to claim 1, wherein the first magnetic air gap has a radial height of 1 mm to 30 mm and/or the at least second magnetic air gap has a radial height of 15 mm to 50 mm.

11. A synchronous superconductive rotary machine according to claim 1, wherein the at least one second pole unit is further connected to a second cooling system configured to cool the superconductive coils to the cryogenic operating temperature.

12. A synchronous superconductive rotary machine according to claim 1, wherein the rotary machine is configured as a generator.

13. A wind turbine comprising: a nacelle arranged on a wind turbine tower; a rotatable hub arranged relative to the nacelle, which hub is connected to at least two wind turbine blades; a generator connected to the hub, where the generator comprises a rotor arranged rotatably relative to a stator, wherein the generator is a synchronous superconducting generator configured according to claim 1.

Description

DESCRIPTION OF THE DRAWING

[0066] The invention is described by example only and with reference to the drawings, wherein:

[0067] FIG. 1 shows an exemplary embodiment of a wind turbine;

[0068] FIG. 2 shows an exemplary embodiment of a rotary machine with a stator and a rotor according to the invention;

[0069] FIG. 3 shows a cross-sectional view of the rotor seen in an axial direction;

[0070] FIG. 4 shows an enlarged section of the cross-sectional view of FIG. 3; and

[0071] FIG. 5 shows a cross-sectional view of the rotor seen in a lateral direction.

[0072] In the following text, the figures will be described one by one, and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure.

POSITION NUMBER LIST

[0073] 1. Wind turbine [0074] 2. Wind turbine tower [0075] 3. Foundation [0076] 4. Nacelle [0077] 5. Hub [0078] 6. Wind turbine blades [0079] 7. Generator [0080] 8. Stator [0081] 9. Rotor [0082] 10. Stator coils [0083] 11. Gap between stator and rotor [0084] 12. Rotor structure [0085] 13. Drive shaft [0086] 14. First cooling units, second cooling units [0087] 15. Connection points of first compressor unit and second compressor unit [0088] 16. First line, third line [0089] 17. Second line, fourth line [0090] 18. Back iron [0091] 19. Outer surface of back iron [0092] 20. First pole units [0093] 21. Second pole units [0094] 22. Outer surface of first pole unit [0095] 23. Rotor coils, superconductive coils [0096] 24. Chamber [0097] 25. Front wall of housing [0098] 26. Superconductive coil arrangement [0099] 27. Winding core element, core element [0100] 28. Spacer element [0101] 29. Plate shaped elements [0102] 30. Thermal shield, passively cooled [0103] 31. Thermal shield, actively cooled [0104] 32. Second space, magnetic air gap [0105] 33. First space, magnetic air gap [0106] 34. Support elements [0107] 35. Mounting point [0108] 36. Thermal conductive elements of first set [0109] 37. Shielding elements [0110] 38. Thermal conductive elements of second set [0111] 39. Connecting element [0112] 40. Connection point [0113] 41. End wall

DETAILED DESCRIPTION OF THE INVENTION

[0114] FIG. 1 shows an exemplary embodiment of a wind turbine 1. The wind turbine 1 comprises a wind turbine tower 2 provided on a foundation 3. A nacelle 4 is arranged on top on the wind turbine tower 2 and configured to yaw relative to the wind turbine tower 2 via a yaw system (not shown). A hub 5 is rotatably arranged relative to the nacelle 4, wherein at least two wind turbine blades 6 are mounted to the hub 5 (here three wind turbine blades are shown).

[0115] A rotary machine in the form of a generator 7 is arranged relative to the nacelle 4, here the generator is enclosed by a nacelle housing. The generator 7 is rotatably connected to the hub 5 via a drive shaft (shown in FIG. 2) for producing a power output.

[0116] FIG. 2 shows an exemplary embodiment of the rotary machine comprising a stator 8 and a rotor 9 arranged rotatably relative to the stator 8. The stator 8 comprises a back iron (not shown) having an inner surface facing the rotor 9. A plurality of pole units each having at least one stator coil 10 are positioned relative to this inner surface and configured to interact via an electromagnetic field with a plurality of rotor coils (shown in FIGS. 3 and 4) when the rotor 9 is rotated relative to the stator 8. A physical gap 11 is formed between the stator 8 and the rotor 9 to allow for rotation of the rotor 9.

[0117] The rotor 9 further comprises a back iron (shown in FIGS. 3 and 4) facing the stator 8 which in connected to a rotor structure 12. The rotor structure is further connected to a drive shaft 13 and enables torque to be transferred from the back iron to the drive shaft 13. The drive shaft 13 is rotatably connected to the hub 5, e.g. directly or via a gear-box unit (not shown).

[0118] A number of first cooling units 14 in the form of cold heads are arranged relative to the rotor 9 for removing heat from a thermal shield (shown in FIG. 4) surrounding the exterior surfaces of a second pole unit (shown in FIGS. 3 and 4). The first cooling units 14 are connected to a first compressor unit 15, here only the connection point (e.g. a rotary feed-through) of the first compressor unit 15 is shown. The first compressor unit 15 is configured to circulate a first working fluid through the first cooling units 14 via a first line 16 and a second line 17. The first cooling units 14, first compressor unit 15, first line 16, and second line 17 form part of a first cooling system for actively cool down the thermal shield (shown in FIG. 4) to an intermediate operating temperature.

[0119] In a similar manner, a number of second cooling units 14 in the form of cold heads are arranged relative to the rotor 9 for removing heat from the rotor coils (shown in FIG. 4) of the second pole unit (shown in FIGS. 3 and 4). Here, a total of six of cooling units 14, 14 are shown. The second cooling units 14 are connected to a second compressor unit 15, here only the connection point (e.g. a rotary feed-through) of the second compressor unit 15 is shown. The second compressor unit 15 is configured to circulate a second working fluid through the second cooling units 14 via a third line 16 and a fourth line 17. The second cooling units 14, the second compressor unit 15, the third line 16, and the fourth line 17 form part of a second cooling system for actively cool down the superconductive coils to a cryogenic operating temperature.

[0120] FIG. 3 shows the rotor 9 seen in an axial direction from one end of the rotor 9. The rotor structure 12 is connected to a back iron 18 which has an outer surface 19 facing the stator 8. The rotor 9 comprises a plurality of first pole units 20 and a plurality of second pole units 21 arranged relative to the outer surface 19 of the back iron 18. Each first pole unit 20 is configured as a pole element made of a magnetic material with no rotor coils (shown in FIG. 4). The first pole unit 20 projects in a radial direction outwards from the outer surface 19 and has an outer surface 22 located at its free end. A gap is formed between opposite facing side surfaces of two adjacent first pole units 20 as indicated in FIG. 3. Here, one second pole unit 21 is arranged within this gap. The second pole unit 21 comprises at least one rotor coil 23 in form of a superconductive coil made of a high temperature superconductive material configured to operate at a cryogenic operating temperature of no more than 70 K.

[0121] FIG. 4 shows an enlarged section of the rotor 9 wherein an end wall (shown in FIG. 5) is omitted for illustrative purposes. The rotor structure 12 is connected to a housing which forms an enclosed chamber 24 in which the first pole units 20 and the second pole units 21 are arranged. The chamber 24 can be connected to a vacuum system (not shown) configured to evacuate the chamber 24 so that it acts as a vacuum chamber. The end wall (shown in FIG. 5) forms part of the housing and is connected to the rotor structure 12 at one end. A front wall 25 of the housing is positioned about the first and second pole units 20, 21 and is connected to the other end of the end wall (shown in FIG. 5). The back iron 18 and, in part, the rotor structure 12 act as the back wall of the housing.

[0122] The second pole unit 21 comprises a superconductive coil arrangement 26 wherein a number of second cooling elements (not shown) are arranged relative to the superconductive coils. The second cooling elements are connected to the second cooling system via a second set of heat transferring elements for removing heat from the superconductive coils. The individual superconductive coils are wound around a winding core element 27 made of a magnetic material. At least one spacer element 28 is arranged between the superconductive coils and the winding core element. This spacer element 28 extends around the core element 27 and at least follows the shape of the individual superconductive coils. This allows for a higher operating current compared to other coil arrangements.

[0123] An optional plate shaped element 29 is arranged at the respective top and bottom ends of the superconductive coil arrangement 26. The spacer element 28 and/or the plate shaped element 29 is/are made of a non-magnetic material.

[0124] A passive thermal shield 30 is applied around the exterior surfaces of the second pole 21. The thermal shield 30 is a thermally insulating laminate comprising at least two layers made of a superinsulation material having good insulating properties. Alternatively, an actively cooled thermal shield 31 is applied around the exterior surfaces of the second pole unit 21. The thermal shield 31 is a laminate with at least one layer made of a heat insulating film and at least one first cooling element (not shown). The thermal shields 30, 31 act as thermal barriers and reduce the heat transfer between the warm back iron 18, the rotor structure 12, the housing, and the first pole units 20 and the cold second pole units 21.

[0125] The first cooling elements are connected to the first cooling system via a first set of heat transferring elements for removing heat from the thermal shield 31. The thermal shield 31 is spaced apart from the superconductive coil arrangement 26 by 5 mm or less.

[0126] Each of the second pole units 21 is spaced apart from the outer surface 19 of the back iron 18 and the first pole units 20 by at least one thermally insulating support element (shown in FIG. 5) so that several spaces are formed. A first space 32 is located between the second pole unit 21 and the back iron 18. A second space 33 is located between the second pole unit 21 and the front wall 25. The first and second spaces 32, 33 contribute to the magnetic air gap of rotary machine. A third space is further located between the second pole unit 21 and either one of the adjacent first pole units 20 as shown in FIG. 4.

[0127] FIG. 5 shows a cross-sectional view of one end of the rotor 9 seen in a lateral direction. Here, the second pole unit 21 is shown with the actively cooled thermal shield 31.

[0128] At least one support element 34 extends in a radial direction and is at one end connected to the second pole unit 21. The support element 34 is at the other end connected to a mounting point 35, e.g. a reinforced element, on the rotor structure 12. At least one support element 34 (not shown) extends in a lateral direction and is at one end connected to the second pole unit 21. This support element 34 is at the other end connected to the first pole unit 20. The individual support elements 34 comprise at least one heat insulating element which acts as a thermal barrier between the warm end and the cold end. The heat insulating element preferably has a thermal conductivity below 40 W/.sub.m.Math.K and provide structural strength to the support element 34.

[0129] Here, the heat transferring elements connected to the first cooling system and the thermal shield 31 are configured as thermal conductive elements 36, only one is shown. The thermal conductive element 36 is connected two shielding elements 37 arranged on opposite sides which extend into the evacuated chamber 24 to form an intermediate space. Here, the heat transferring elements connected to the second cooling system and the second pole unit 21 are also configured as thermal conductive elements 38; only one is shown. The thermal conductive element 38 is arranged within this intermediate space so that the shielding elements 37 protect the second set of thermal conductive elements 38 from heat radiating from the warmer components situated around these cold components. An optional connecting element 39 is arranged between the thermal conductive element 38 and the second pole unit 21 so that the thermal conductive element 38 can be positioned in this intermediate space.

[0130] Another heat transferring element in the form of a thermal conductive element (indicated by dotted line) is connected to a selected thermal conductive element 36 and to a connection point 40 located on a selected support element 34. This allows heat introduced into the support element to be dissipated into the first cooling system.

[0131] The end wall 41 of the housing is here shown as a L-shaped wall connected to the front wall 15 and the rotor structure 12.