Generator Rotor Assembly

Abstract

The generator rotor assembly includes a cylindrical ring structure defining a central hollow and arranged to rotate about a rotational axis. The cylindrical ring structure includes a plurality of permanent magnet packages arranged coaxially about the rotational axis, the permanent magnet packages including a coaxially stacked annular segment layer, a plurality of tie rod holes, and a plurality of tie rods. The coaxially stacked annular segment layer includes a plurality of consecutive segment sheets arranged about the rotational axis to form a ring-shaped layer, the stacked layers being staggered such that a segment separation between two consecutive segment sheets in one layer is angularly offset relative to a segment separation between two consecutive segment sheets in an adjacent layer. The tie rod holes extend axially through the layers of the permanent magnet packages, and the plurality of tie rod holes of adjacent permanent magnet packages are complementary in size and position to define a plurality of tie rod holes. A tie rod extends through each of the plurality of tie rod holes.

Description

Technical Field

[0001] The present invention relates to a generator rotor assembly. More particularly, the present invention relates to a generator rotor assembly for a wind turbine.

Background Art

[0002] A wind turbine converts kinetic energy from the wind into electrical energy using a large rotor with a number of rotor blades. A typical horizontal axis wind turbine (HAWT) includes a tower, a nacelle on top of the tower, a rotor hub attached to the nacelle, and a plurality of wind turbine rotor blades coupled to the rotor hub. A yaw system that rotates the nacelle and a pitch system that rotates the blades rotate and orient the nacelle and rotor blades in an optimal direction according to the direction of the wind.

[0003] The nacelle houses many functional components of a wind turbine, such as, for example, a generator, a gearbox, a drive train, and a rotor brake assembly, as well as a conversion device for converting mechanical energy in the rotor into electrical energy for supply to the grid. The gearbox increases the rotational speed of the low-speed main shaft and drives the gearbox output shaft. The gearbox output shaft further drives a generator, which converts the rotation of the gearbox output shaft into electricity. The electricity generated by the generator can then be converted as necessary before being supplied to an appropriate consumer, such as a power distribution system. So-called "direct drive" wind turbines that do not use a gearbox are also known. In a direct drive wind turbine, the generator is directly driven by a shaft connected to the rotor.

[0004] Typically, the generator of a wind turbine is an IPM (Interior Permanent Magnet) electrical machine consisting of an external stator assembly surrounding an internal rotor assembly. The IPM internal rotor assembly typically consists of a plurality of annular permanent magnet packages supported on a central axis. The gearbox output shaft interfaces with the central axis of the rotor assembly.

[0005] Like other electrical machines, a permanent magnet package typically consists of a stack of annular metal layers having aligned holes for receiving permanent magnets that generate the required magnetic field. In the case of large generators such as those of large wind turbines, the manufacture of the permanent magnet package is difficult because the rings are simply too large to be manufactured integrally. It is known to assemble the metal layers from a number of smaller segment sheets, all of which are provided on a central hub to form an annular layer. The segmented layer may not have the same strength and structural integrity as a layer made of a single layer metal piece, but the central hub provides the rotor with sufficient structural support to withstand all the centrifugal and other forces acting on the rotor during use.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] Another technical consideration for the design of a wind turbine generator is that the efficiency of the generator decreases when the generator is heated during use. This also applies to other major components of a wind turbine, such as a gearbox. The performance and lifespan of a wind turbine thus depend on the efficient cooling of the generator.

[0007] Air cooling is a cost-effective way to cool the generator. However, a megawatt-scale generator within the limited space of the generator housing generates excessive heat for current air cooling methods to effectively cool the generator. The lack of efficient cooling of the generator results in temperature rises inside and around generator components such as the rotor assembly.

[0008] The object of the present invention is to provide a solution to one or more of the above problems.

MEANS FOR SOLVING THE PROBLEMS

[0009] According to a first aspect of the present invention, the above object is achieved by providing a generator rotor assembly for a wind turbine, the generator rotor assembly comprising a cylindrical ring structure defining a central hollow portion and arranged to rotate about a rotation axis. The cylindrical ring structure includes a plurality of permanent magnet packages coaxially arranged around the rotation axis, the permanent magnet packages including a plurality of coaxially stacked annular segmented layers, a plurality of tie rod holes, and a plurality of tie rods. The coaxially stacked annular segmented layers include a plurality of continuous segment sheets arranged around the rotation axis to form an annular layer, and the stacked layers are staggered such that a segment break (segment separation) between two consecutive segment sheets in one of the layers is angularly offset with respect to a segment break between two consecutive sheets in an adjacent layer. The tie rod holes extend axially through the layers of the permanent magnet packages, and the plurality of tie rod holes of adjacent permanent magnet packages are complementary in dimension and position such that a plurality of tie rod holes are defined. The tie rods extend through each of the plurality of tie rod holes.

[0010] The staggering of the annular segmented layers increases the friction between the stacked layers of the permanent magnet packages. In addition, the axial tie bolt preload increases the strength structure and structural integrity of the individual permanent magnet packages and the cylindrical ring structure as a whole. These advantages make it possible to manufacture large permanent magnet packages having a strength similar to that of a solid ring and capable of withstanding the centrifugal force (and other forces) applied thereto in a typical wind turbine generator. As a result, this enables the manufacture of a large generator rotor assembly structure without the need to assemble the permanent magnet packages on a central hub.

[0011] Not having a central hub within the rotor assembly offers many important advantages such as cost and weight reduction and improved cooling air flow. The cooling air supplied to the center of the generator can flow freely axially and radially, effectively cooling the rotor and the generator components located in its immediate vicinity. A further important advantage of the rotor structure according to the present invention is the modular nature of the rotor assembly. The technical specifications of the rotor assembly can be easily adapted to the required performance, for example, by selecting the appropriate number of permanent magnet packages and the number of layers per package.

[0012] In a preferred embodiment, at least one of the end faces of the generator rotor assembly is at least partially open to allow the cooling air flow to flow from the outside of the generator rotor assembly into the central hollow portion. The cooling flow path is provided between at least a part of the plurality of permanent magnet packages to allow the cooling air flow to flow from the central hollow portion through the cooling flow path and out of the generator rotor assembly.

[0013] Preferably, the generator rotor assembly further includes a plurality of spacers disposed on the tie rods and between adjacent permanent magnet packages. Such spacers provide a void between subsequent permanent magnet packages through which the cooling air flow can also reach any part close to the stator and the outer housing of the generator.

[0014] In a preferred embodiment, all segment sheets include a number of tie rod holes spaced over the tie rod separation angle, and the angular offset between two adjacent layers is a multiple of the tie rod separation angle. It is important that the tie rod holes of adjacent layers are aligned to ensure that the tie rods can extend through all the permanent magnet packages, and it is also important when the layers are staggered and an angular offset between the layers is introduced. If all segment sheets have a plurality of tie rod holes, this allows for more different angular offsets that make it possible to form the required tie rod holes.

[0015] According to one embodiment, the angular offset between any two adjacent layers within the permanent magnet package is at least two tie rod separation angles. The greater the distance between the segment breaks of adjacent layers, the greater the overlap of each segment sheet and the greater the friction between the two layers. The increase in friction leads to an improvement in the strength and structural integrity of the entire magnet package.

[0016] In a particular embodiment, for all layers within the permanent magnet package, the angular offset with an adjacent layer is greater than the angular offset with a subsequent layer. The resulting zigzag arrangement further enhances the strength and structural integrity of the permanent magnet package.

[0017] To further improve these aspects, the number of non-angularly offset layers for every two layers within the permanent magnet package is equal to the total number of tie rod holes per segment sheet minus one. In such an embodiment, all available different angular offsets are used.

[0018] For example, a stronger and more powerful permanent magnet package can be obtained by adhering multiple layers together using an adhesive varnish such as an adhesive or a backing lacquer.

[0019] The cylindrical ring structure may further comprise an annular flange with a rotor connection that is securely attached to one of the end packages of the cylindrical ring structure. This flange further includes a drive shaft connection configured to connect directly or indirectly to a drive shaft. This flange enables the connection of a hubless rotor to, for example, the output shaft of a gearbox without obstructing the flow of cooling air to the permanent magnet package and the stator through the rotor center.

[0020] The annular flange may be securely attached to the end package at the non-driven end of the rotor. The flange can be connected to the end package via tie rods.

[0021] According to a further aspect of the present invention, the wind turbine comprises a generator having a generator rotor assembly as described above or below.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 8A

Figure 8B

Figure 9

Figure 10

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Figure 13

Best Mode for Carrying Out the Invention

[0023] Hereinafter, with reference to the accompanying drawings, the present invention will be described as an example.

[0024] Next, specific embodiments of the present invention will be described. In this embodiment, in order to provide a complete understanding of the inventive concept defined in the claims, a number of features will be examined in detail. However, it will be apparent to those skilled in the art that the present invention can be practiced without specific details, and in some instances, well-known methods, techniques, and structures have not been described in detail so as not to unnecessarily obscure the present invention.

[0025] To place the embodiments of the present invention in an appropriate context, first refer to FIG. 1, which shows a typical horizontal axis wind turbine (HAWT) on which a generator rotor assembly according to an embodiment of the present invention can be implemented. This particular image shows an onshore wind turbine, but it will be understood that similar features are also found in offshore wind turbines. Further, although the wind turbine is referred to as "horizontal axis", for practical purposes, those skilled in the art will understand that the axis is usually slightly inclined to prevent contact between the rotor blade and the wind turbine tower in the case of strong winds.

[0026] The wind turbine 1 includes a tower 2, a nacelle 4 rotatably connected to the top of the tower 2 by a yaw system, a rotor hub 8 attached to the nacelle 4, and a plurality of wind turbine rotor blades 10 connected to the rotor hub 8. The nacelle 4 and the rotor blades 10 are pivoted in the wind direction by the yaw system.

[0027] The nacelle 4 houses many functional components of a wind turbine, including a generator, a gearbox, a drive train, and a rotor brake assembly, as well as a conversion device for converting the mechanical energy of the wind into electrical energy for supply to the grid. Referring to FIG. 2, the nacelle 4 can include a shaft housing 20, a gearbox 22, and a generator 24. The main shaft 26 extends through the shaft housing 20 and is supported by bearings (not shown). The main shaft 26 is connected to and driven by the rotor 8 to provide an input drive to the gearbox 22. The gearbox 22 increases the rotational speed of the low-speed main shaft via internal gears (not shown) and drives the gearbox output shaft. The gearbox output shaft then drives the generator 24, and the generator converts the rotation of the gearbox output shaft into electricity. The electricity generated by the generator 24 can then be converted by other components (not shown) as necessary before being supplied to a suitable consumer, such as a power distribution system. So-called "direct drive" wind turbines that do not use a gearbox are also known. Thus, the gearbox can be considered optional.

[0028] The gearbox 22 and the generator 24 may be coupled together within an integrated unit. FIG. 3 shows the generator 24 in more detail. In FIG. 3, the housing of the final stage of the gearbox 22 is also shown as being connected to the housing of the generator 24.

[0029] Referring initially to the gearbox 22, the gearbox housing has a generally cylindrical shape and is oriented such that its main axis of rotation is horizontal in the orientation of the drawing. The cylindrical shape of the gearbox housing is due to the particular type of gearbox used in the illustrated embodiment, which is an epicyclic gearbox. As is known to those skilled in the art, an epicyclic gearbox consists of a series of planet gears arranged around a central sun gear, and these planet gears are collectively arranged within an annular ring gear. The gear ratio of the gearbox is determined by the ratio of the number of teeth between the annular gear, the planet gears, and the sun gear. Since the gearbox is not the main subject of the present invention, a detailed description of the gearbox is omitted here for clarity. At present, it is considered that the epicyclic gearbox provides an elegant solution that fits into the area of the wind turbine nacelle, but it is sufficient to state that other gearbox configurations can also be used.

[0030] The output shaft of the gearbox 22 is connected to the rotor 32 of the generator 24. Thus, the main axis of the gearbox output shaft defines the axis of rotation of the generator 24. In FIG. 4, only a cross-sectional view of the generator 24 is provided. The generator 24 in the illustrated embodiment is an IPM (Interior Permanent Magnet) electrical machine having an outer stator surrounding the rotor 32. The stator includes a stator winding 38, a stator core 40, and a stator frame surrounding and supporting the stator winding 38 and the stator core 40. However, it should be noted that the present invention is not limited to a particular type of stator.

[0031] According to an embodiment of the present invention, a generator rotor assembly 42 that forms a part of the rotor 32 of the generator 24 is provided. Such a generator rotor assembly 42 will be described below with reference to FIGS. 6 to 11. The generator rotor assembly 42 has a non-driven end, whereby the non-driven end faces in a direction opposite to the wind turbine drive line when the wind turbine is in use, and also has a driven end that faces in the direction of the drive line when the turbine is in use. A non-driven end face view of the generator rotor assembly 42 is shown in FIG. 5, and a driven end face view of the generator rotor assembly 42 is shown in FIG. 6.

[0032] The generator rotor assembly 42 consists of a cylindrical ring structure 46 that defines a central hollow portion and is arranged to rotate about a rotation axis. The cylindrical ring structure 46 includes a plurality of permanent magnet packages 48. In this embodiment, all the permanent magnet packages 48 have the same circumference and thickness. In some embodiments, the thicknesses of the permanent magnet packages 48 may be different from each other. For example, the rotor can include two permanent magnet packages 48 with different thicknesses, where the permanent magnet packages 48 with different thicknesses are arranged alternately. The permanent magnet packages 48 are coaxially arranged around the rotation axis, and when assembled, the arrangement of the permanent magnet packages 48 defines a cylindrical structure having a central hollow portion. The permanent magnet packages 48 are spaced apart by an equal distance such that a gap is defined between each pair of the permanent magnet packages 48. These gaps allow air supplied to the center of the generator to flow through the rotor structure and cool other parts of the generator, including the generator rotor assembly and the parts located radially outside the rotor assembly 42. This air flow is further enhanced by the fact that a central hub is not required to provide the structure and support of the rotor assembly 42.

[0033] The cylindrical ring structure 46 is defined by two end packages and a plurality of permanent magnet packages 48 provided therebetween. The two end packages include a first end package 50 and a second end package disposed at opposite ends of the cylindrical ring structure 46. That is, as shown in FIG. 5, the first end package 50 is located at the non-driven end of the cylindrical ring structure 46, and the second end package is located at the driven end of the cylindrical ring structure 46.

[0034] The end package 50 is generally just a normal permanent magnet package, similar to the other permanent magnet packages 48 within the cylindrical ring structure 46, but note that the only exception is that it is provided at the end of the cylindrical ring structure 46. Alternatively, one or both of the end packages may have a greater thickness than the other permanent magnet packages 48. The end package 50 may further comprise additional features that enable connection to other parts of the generator of the cylindrical ring structure 46 or a coating covering the outer surface of the cylindrical ring structure 46. The end ring 52 may be connected to one or both of the end packages 50, and the end ring 52 may contain the permanent magnet itself.

[0035] The permanent magnet package 48 includes a plurality of tie rod holes extending axially through the permanent magnet package 48. The holes are disposed around the body of each permanent magnet package 48. The holes are preferably spaced apart by equal distances, i.e., angles. The holes of adjacent permanent magnet packages 48 are complementary in dimension and position such that a plurality of tie rod holes are defined. The tie rod holes are arranged concentrically around the axis of rotation. The tie rod holes extend through the packages 48 of the cylindrical ring structure 46 from the first end package 50 to the second end package and, in some cases, also through any additional end ring 52 or other structural elements directly connected to the cylindrical ring structure 46.

[0036] The plurality of tie rods 54 extend through respective ones of the plurality of tie rod holes. A plurality of spacers or washers 56 are disposed on the tie rods 54 and between adjacent permanent magnet packages 48. Accordingly, the tie rod holes are defined by a repeating pattern of the inner surface of the tie rod holes and the washers 56. Note that in other embodiments, no washers 56 are used, thereby providing a single permanent magnet package rotor also supported by the plurality of rods 54.

[0037] One embodiment of the permanent magnet package 48 is shown in FIGS. 7-9 and includes a plurality of coaxially stacked annular segmented layers 80, each segmented layer including a plurality of continuous segment sheets 82 disposed about the axis of rotation to form the annular layer 80. Tie rod holes 86 extend axially through the layers of the permanent magnet package 48, and the plurality of tie rod holes 86 of adjacent permanent magnet packages 48 define a plurality of tie rod holes, and the tie rods 54 are dimensioned and positioned to extend through respective ones of the plurality of tie rod holes in a complementary manner.

[0038] A front view of the complete annular layer 80 is shown in FIG. 7. Enlarged views of the segment sheets 82 are shown in FIGS. 8A and 8B. The annular layer 80 consists of a plurality of segment sheets 82 arranged concentrically about the axis of rotation. The annular layer 80 of the present embodiment is composed of six segment sheets 82, but in other embodiments, other numbers of segment sheets 82 may be used. Effectively, the permanent magnet package 48 of the generator rotor assembly is formed from the stacked layers 80, whereby each layer 80 is formed from a plurality of segment sheets 82 that are joined to each other at their segment ends to form an annular layer 80 having segment separations. Preferably, all of the segment sheets 82 are identical and dimensioned such that all of the segment sheets 82 constitute 360 degrees of the complete annular layer 80.

[0039] As shown in FIG. 8A, the segment sheet 82 is an arc defined by an outer circumference 90, an inner circumference 92, and an apex angle 94 (see FIG. 7). The apex angle 94 is preferably equal to 360 degrees divided by the number of segment sheets 82 per layer 80 so that all the segment sheets 82 used can be identical. The segment sheet 82 has two segment ends disposed at both ends of the segment sheet 82 and connecting the outer circumference 90 and the inner circumference 92. The two segment ends are adjacent to the ends of the adjacent segment sheets 82.

[0040] The segment sheet 82 shown in FIG. 7 includes the same number of tie rod holes 86 as the six magnet pairs 84. Six consecutive segment sheets 82 form an annular layer 80 having six separate segments, 36 magnetic poles, and 36 tie rod holes 86. Here, the magnetic poles are formed by a pair of permanent magnets disposed in the magnet holes 88. In this example, each segment sheet 82 has six tie rod holes 86 and is provided with six N - pole magnetic poles and six S - pole magnetic poles. In an alternative embodiment, the number of tie rod holes 86 per segment sheet 82, unlike the amount of magnet pairs, will be different in the number of tie rod holes 86 and / or magnet holes 88 per segment sheet 82. Also, the number of permanent magnets used to provide the magnetic poles can vary. The number of magnet holes 88 is preferably a multiple of the number of tie rod holes 86.

[0041] In the embodiment shown here, the position of the tie rod holes 86 in the segment sheet 82 is such that partial tie rod holes 86 are disposed at the segment ends. When assembled into a complete annular layer 80, the partial tie rod holes 86 on each side of the segment join together to form a complete tie rod hole 86. In another arrangement, the segment sheet 82 will have only complete tie rod holes 86. For example, the separation of the segments may be provided between the two magnet holes 88 of the magnet pair or in the middle of the magnet holes 88.

[0042] The annular layer 80 composed of segment sheets 82 is coaxially laminated to form the permanent magnet package 48 as shown in FIG. 9. The layers 80 are laminated such that the segment sheets 82 of adjacent layers 80A to 80F are angularly offset from each other. As shown in FIG. 9, this causes the layers 80 of the permanent magnet package 48 to be in a staggered pattern.

[0043] To enable the formation of tie rod holes through the permanent magnet package 48, the angular offset between two adjacent layers 80 needs to be equal to or a multiple of the tie rod separation angle, i.e., the angular distance between two adjacent tie rod holes 86. In a symmetric setup, the tie rod separation angle is equal to the value obtained by dividing 360 degrees by the total number of tie rods used in the cylindrical ring structure 46, i.e., the segment sheet apex angle 94 divided by the number of tie rod holes 86 per segment sheet. In this example, since each segment sheet 82 has six tie rod holes 86, five different angular offsets are possible with respect to the first layer 80A (i.e., six different possible orientations per layer 80A to 80F).

[0044] According to the preferred embodiment shown in FIG. 9, the angular offset between any two adjacent layers 80A - 80F within the permanent magnet package 48 is at least twice the tie rod separation angle. Compared to an offset corresponding only to the tie rod separation angle, this configuration provides additional friction between adjacent layers 80, improving the strength and structural integrity of the magnet package 48 as a whole. The angular offset of the second layer 80B with respect to the first layer 80A, starting from the left side in the figure, is two tie rod separation angles. The angular offset of the third layer 80C with respect to the first layer 80A is five tie rod separation angles. The angular offset of the fourth layer 80D with respect to the first layer 80A is three tie rod separation angles. The angular offset of the fifth layer 80E with respect to the first layer 80A is one tie rod separation angle. The angular offset of the sixth layer 80F with respect to the first layer 80A is four tie rod separation angles. These translate to interlayer offsets between six consecutive layers 80A - 80F of two, three, two, two, and three tie rod separation angles, still using all six available orientations. After the six layers 80A - 80F, the same pattern may be repeated until the package 48 is complete. As a result, there are always five layers 80 with the same orientation between two layers, thereby increasing the strength and structural integrity of the entire magnet package 48 again. More generally, the number of layers that are not angularly offset from each other between the layers within the permanent magnet package 48 is equal to the total number of tie rod holes 86 per segment sheet 82 minus one.

[0045] To add further friction between layers 80A - 80F and improve the overall strength and structural integrity of the permanent magnet package 48, all offsets in one direction follow the offsets in the other direction. In other words, for each layer 80A - 80F within the permanent magnet package 48, the angular offset at adjacent layers 80A - 80F is greater than the angular offset at subsequent layers 80A - 80F. Adding directionality to the already listed inter - layer offsets (measured by the tie - rod separation angle) between six consecutive layers 80A - 80F gives [+2, +3, -2, -2, +3, +2], such that +3 and -3 result in the same offset in a symmetric nacelle up having six tie - rod holes 86 per layer 80. This zig - zag arrangement strengthens the frictional bonding between different layers 80 of the permanent magnet package 48 much more than if all offsets were in the same direction.

[0046] In this embodiment, the number of available angular directions (equal to the number of tie - rod holes 86, which is 6) is less than the number of layers within the permanent magnet package (12). Thus, the angular offset between adjacent layers 80 can be different up to the sixth layer. Starting from the seventh layer, the pattern of rotation repeats for the remaining layers 80 of the permanent magnet package 48. Note that the permanent magnet package 48 can include any number of layers 80, and that number does not necessarily have to be a multiple of the number of tie - rod holes 86 per segment sheet 82. Alternatively, in a thinner permanent magnet package 48, when using thicker layers 80, or when using a larger segment sheet 82 with more tie - rod holes 86 per segment sheet, the total number of possible orientations can be equal to or less than the number of layers 80 within the permanent magnet package 48. In this case, all layers 80 within the permanent magnet package 48 can be angularly offset from each other.

[0047] By being in a zigzag shape, the frictional force between the annular layers 80 increases, and by further increasing it with a special zigzag pattern, a laminate of layers 80 having the same strength and structural integrity as a single solid ring of the same dimensions is obtained. To further improve the structural integrity, the laminated annular layers 80 may be adhered to each other by an adhesive or adhesive varnish such as a back rack.

[0048] This zigzag configuration has the same strength as a solid ring and enables the manufacture of a large permanent magnet package 48 that can withstand the centrifugal force (and other forces) applied to it in a typical wind turbine generator. Thus, it enables the manufacture of a large generator rotor assembly structure for which it is impossible to manufacture a generator rotor assembly from a solid ring without the need to assemble the permanent magnet package 48 on a central hub. The absence of a central hub in the rotor assembly provides many important advantages such as cost and weight reduction and improved cooling air flow. The absence of a central hub means that the air supplied to the center of the generator can flow freely axially and radially, cooling the generator rotor assembly 42 and other parts of the generator located in its immediate vicinity. In combination with the zigzag arrangement of the split annular layers 80, the tie rods 54 and washers 56 may function as shear pins to further prevent the layers from slipping relative to each other.

[0049] The rods 54 and the permanent magnet package 48 preferably, together with the washers 56, provide the main structure of the rotor. To enable the hubless rotor to be connected to a drive shaft, such as the output shaft of a gearbox, the cylindrical ring structure 46 includes an annular flange 57, as seen in FIG. 5, which is firmly attached to the first end package 50 at the non-driven end. In some embodiments, the annular flange may be securely attached to the second end package at the drive end. An end ring 52 may be provided between the end package and the annular flange 57.

[0050] The annular flange 57 includes a rotor connection portion 58 firmly fixed to the first end package 50 and a drive shaft connection portion 60 configured to be indirectly connected to a gearbox output shaft, also referred to as a drive shaft. The generator rotor assembly 42 is interfaced with a connector 44 (see FIG. 5) for additional components, such as a brake disc.

[0051] The rotor connection portion 58 of the annular flange 57 is attached to the first end package 50 using tie rods 54 that together hold the permanent magnet package 48 to form a cylindrical ring structure 46. The circumference of the rotor connection portion 58 of the annular flange 57 is substantially the same as the circumference of the first end package 50. The rotor connection portion 58 has a plurality of holes that penetrate axially through the rotor connection portion 58. The plurality of holes in the rotor connection portion 58 are arranged to receive the plurality of tie rods 54 and attach the annular flange 57 to the first end package 50. The rotor connection portion 58 is attached parallel to and in direct contact with the first end package 50. This can be seen particularly clearly in the partial cross-sectional view and side cross-sectional view of the generator rotor assembly shown in FIGS. 10 and 11, respectively.

[0052] The drive shaft connection portion 60 of the annular flange 57 is clearly shown in FIGS. 10 and 11 and extends in a plane parallel to the rotor connection portion 58. The circumference of the drive shaft connection portion 60 is shorter than the circumference of the rotor connection portion 58. The drive shaft connection portion 60 consists of an annular element. Also, the drive shaft connection portion 60 is located within a central hollow portion formed by the cylindrical ring structure 46.

[0053] The annular flange 57 may be a single ring whose radially outer portion forms the rotor connecting portion 58 and whose radially inner portion forms the drive shaft connecting portion 60. Alternatively, the annular flange 57 may further include an intermediate portion 62 (see Fig. 10) that connects the rotor connecting portion 58 to the drive shaft connecting portion 60. This intermediate portion 62 may be angled with respect to the two connecting portions 58, 60 such that the annular flange 57 projects partially into the hollow portion of the generator rotor assembly 42. In the embodiment of Fig. 10, the angle centered on the common point (apex) between the intermediate portion 62 and the rotor connecting portion 58 is approximately 135 degrees. The angle centered on the common point between the intermediate portion 62 and the drive shaft connecting portion 60 is approximately 135 degrees.

[0054] The intermediate portion 62 has a plurality of bridge portions 64 arranged concentrically about the rotation axis at a predetermined interval along the rotor connecting portion 58, and a bridge gap 66 is formed between adjacent bridge portions 64. The bridge gap 66 allows the cooling air flow to pass through the annular flange 57 and enter the internal structure of the generator.

[0055] Also, the annular flange 57 has a drive shaft connecting frame 68 connected to the drive shaft connecting portion 60. The drive shaft connecting frame 68 extends into the central hollow portion. In this example, the connecting frame 68 has a frustoconical shape with an outer surface substantially parallel to the intermediate portion 62 of the annular flange 57. The outer surface preferably includes openings that allow the cooling air flow to flow through and reach the internal structure of the generator. The drive shaft connecting frame 68 is configured to connect the annular flange 57 to the drive shaft. The annular flange 57 and the drive shaft connecting frame 68 provide a stable and space-saving structure for connecting the cylindrical ring structure 46 of the generator rotor assembly 42 to the drive shaft.

[0056] The drive shaft connecting frame 68 can be seen more clearly in FIG. 12, which is a perspective view of the non-driven end of the generator rotor assembly of FIG. 5 with the connector 44 removed. The drive shaft connecting frame 68 has a generally frustoconical shape, and the circular outer edge 72 of the base of the frame 68 is joined to the circular outer edge 74 of the drive shaft connecting portion 60. The frame 68 extends from the drive shaft connecting portion 60 into the hollow portion of the cylindrical ring structure 46. The frame 68 includes a circular channel 76 that is arranged to rotate about the axis of rotation together with the cylindrical ring structure 46 of the generator rotor assembly 42. The circular channel 76 is for receiving the gearbox output shaft. The frame 68 also includes a perforated wall 78 that extends from the circular outer edge 72 of the base of the frame 68 to the circular channel 76. The perforations in the perforated wall 78 facilitate the air flow through the generator rotor assembly.

[0057] The permanent magnet packages 48 within the generator rotor assembly are connectable within the modular structure to vary the number of permanent magnet rings contained within the cylindrical ring structure. Thus, the structure of the generator rotor assembly of the present invention enables a modular approach that can use rotors with any desired number and type of permanent magnet packages 48.

[0058] During assembly of the generator, the generator rotor assembly 42 is surrounded by the external stator assembly 36, which includes the stator core 40 and a stator frame that surrounds and supports the stator core 40. Both the generator rotor assembly 42 and the generator stator assembly 36 are surrounded by the generator housing 70, which can be seen in the exploded view of the generator housing 70, the generator rotor assembly 42, and the generator stator assembly 36 of FIG. 13.

[0059] The generator rotor assembly 42 and the connection to the drive shaft allow the cooling air flow to pass through the central hollow portion defined by the cylindrical ring structure 46 and between adjacent permanent magnet packages 48.

[0060] Many modifications can be made to the above-described specific embodiments without departing from the scope of the invention as defined in the appended claims. The features of one embodiment can be used in other embodiments, either as an addition to such embodiments or as an alternative thereto.

[0061] For example, a part of the permanent magnet package 48 within the cylindrical ring structure 46 may have a different circumference from other permanent magnet packages within the cylindrical ring structure 46. A part of the permanent magnet package 48 within the cylindrical ring structure 46 may have a different thickness from other permanent magnet packages within the cylindrical ring structure 46.

[0062] For example, the cylindrical ring structure 46 of the generator rotor assembly can include an annular flange having a rotor connection portion firmly attached to a second end ring at the drive end of the rotor assembly. The drive shaft connection portion may be configured to be directly connected to the drive shaft.

[0063] The annular flange may be attached to either end package by means other than the tie rod 54 used for that purpose in the above-described embodiments.

[0064] The drive shaft connection portion may not only be parallel to the rotor connection portion, but may also extend within a plane that coincides with the rotor connection portion.

[0065] The intermediate portion formed between the rotor connection portion and the drive shaft connection portion is 90 to 180 degrees, preferably 105 to 165 degrees, more preferably 120 to 150 degrees with respect to the rotor connection portion, and is also at a similar angle with respect to the drive shaft connection portion. When the angles are the same but the directions are different, it is practical in terms of connecting the gearbox output shaft and the rotor assembly, with the rotor connection portion and the drive shaft connection portion being located within a parallel plane. However, it should be noted that the two angles are not necessarily equal and may be different if desired.

[0066] The rotor connecting portion may further include a plurality of clamps that clamp the rotor connecting portion to the respective end rings. The rotor connecting portion may be attached parallel to one of the end packages, but may not be in direct contact. For example, a spacer may be disposed between the end package and the rotor connecting portion.

Claims

Claim 1 A generator rotor assembly (42) for a wind turbine, said generator rotor assembly (42) comprising a cylindrical ring structure (46) that defines a central hollow portion and is arranged to rotate about a rotation axis, said cylindrical ring structure (46) comprising a plurality of permanent magnet packages (48) coaxially arranged around said rotation axis, said permanent magnet packages (48) comprising a plurality of coaxially stacked annular segment layers (80) each including a plurality of continuous segment sheets (82) arranged around said rotation axis to form an annular layer, said stacked layers (80) being arranged in a staggered pattern such that a segment separation between two consecutive segment sheets (82) in one layer is angularly offset with respect to a segment separation between two consecutive segment sheets (82) in an adjacent layer; a plurality of stacked annular segment layers, a plurality of tie rod holes (86) extending axially through the layers of said permanent magnet packages (48), said plurality of tie rod holes (86) of adjacent permanent magnet packages (48) being complementary in dimension and position such that said plurality of tie rod holes are defined; a plurality of tie rod holes, a plurality of tie rods (54) extending through each of said plurality of tie rod holes, and a generator rotor assembly having at least one of its end faces at least partially open to allow a cooling air flow to flow from outside the generator rotor assembly (42) into said central hollow portion. Claim 2 The generator rotor assembly according to claim 1, wherein all of said segment sheets (82) include a number of tie rod holes (86) spaced apart over a tie rod separation angle, and an angular offset between two adjacent layers is a multiple of the tie rod separation angle. Claim 3 The generator rotor assembly according to claim 1 or 2, wherein an angular offset between any two adjacent layers in said permanent magnet package (48) is at least two tie rod separation angles. Claim 4 The generator rotor assembly according to any one of claims 1 to 3, wherein for each layer of said permanent magnet package (48), an angular offset with an adjacent layer is greater than an angular offset with a subsequent layer. Claim 5 The number of layers within the permanent magnet package (48) that are not angularly offset from each other is equal to the total number of tie rod holes (86) per segment sheet minus one, for the generator rotor assembly according to any one of claims 2 to 4.

6. The total number of tie rod holes (86) per segment sheet is less than or equal to the number of layers within the permanent magnet package (48), and all layers within the permanent magnet package (48) are angularly offset from each other, for the generator rotor assembly according to any one of claims 2 to 4.

7. Each of the segment sheets further includes a plurality of pairs of magnet holes (88) for receiving internal permanent magnets to establish magnetic poles, and the number of pairs of magnet holes (88) is equal to or a multiple of the number of tie rod holes (86), for the generator rotor assembly according to any one of claims 2 to 6.

8. The plurality of stacked annular segment layers are adhered to each other, for the generator rotor assembly according to any one of claims 1 to 7.

9. The tie rod (54) further includes a plurality of spacers (56) disposed between adjacent permanent magnet packages (48), for the generator rotor assembly according to any one of claims 1 to 8.

10. The plurality of permanent magnet packages (48) include two end packages (50) disposed at opposite ends of the cylindrical ring structure (46), The cylindrical ring structure (46) further includes an annular flange (57) including a rotor connection portion (58) firmly attached to one of the end packages (50), and a drive shaft connection portion (60) configured to be directly or indirectly connected to a drive shaft, for the generator rotor assembly according to any one of claims 1 to 9.

11. The end packages (50) are disposed at the drive end and the non-drive end of the cylindrical ring structure (46), The non-drive end faces away from the drive line of the wind turbine during use, and the annular flange (57) is firmly attached to the end package (50) at the non-drive end, for the generator rotor assembly according to claim 10.

12. The rotor connection portion (58) includes a plurality of tie rod holes extending axially through the rotor connection portion (58), The plurality of tie rod holes of the rotor connecting portion (58) are arranged to receive the plurality of tie rods (54) and attach the annular flange (57) thereto, according to claim 10 or 11 of the generator rotor assembly.

13. The rotor connecting portion (58) is attached in parallel to and in direct contact with the end package (50), according to any one of claims 10 to 12 of the generator rotor assembly.

14. The drive shaft connecting portion (60) extends in a plane that coincides with or is parallel to the rotor connecting portion (58), according to any one of claims 10 to 13 of the generator rotor assembly.

15. The perimeter of the drive shaft connecting portion (60) is shorter than the perimeter of the rotor connecting portion (58), according to any one of claims 10 to 14 of the generator rotor assembly.

16. The annular flange (57) further includes an intermediate portion (62) that connects the rotor connecting portion (58) to the drive shaft connecting portion (60). The intermediate portion (62) is arranged at 90 degrees to 180 degrees, preferably 105 degrees to 165 degrees, more preferably 120 degrees to 150 degrees with respect to the rotor connecting portion (58), and at 90 degrees to 180 degrees, preferably 105 degrees to 165 degrees, more preferably 120 degrees to 150 degrees with respect to the drive shaft connecting portion (60), according to any one of claims 10 to 15 of the generator rotor assembly.

17. The intermediate portion (62) includes a plurality of bridge portions (64) arranged at a predetermined interval along the rotor connecting portion (58) and concentrically around the rotation axis, and a bridge gap (66) is defined between adjacent bridge portions (64), according to claim 16 of the generator rotor assembly.

18. The rotor connecting portion (58) further includes a plurality of clamps for clamping the rotor connecting portion (58) to the end package (50), according to any one of claims 10 to 17 of the generator rotor assembly.

19. The perimeter of the annular flange (57) is substantially equal to the perimeter of the end package (50), according to any one of claims 10 to 18 of the generator rotor assembly.

20. The drive shaft connecting portion (60) includes an annular element, according to any one of claims 10 to 19 of the generator rotor assembly.

21. The annular flange (57) further includes a drive shaft connection frame (68) connected to the drive shaft connection portion (60). The drive shaft connection frame (68) extends into the central hollow portion, and the drive shaft connection frame (68) is configured to connect the annular flange (57) to the drive shaft. The generator rotor assembly according to any one of claims 10 to 20.

22. The generator rotor assembly according to any one of claims 1 to 21, further comprising a cooling flow path provided between at least some of the plurality of permanent magnet packages (48) to enable generation of a cooling air flow from the central hollow portion toward the outside of the generator rotor assembly (42).

23. Each of the segment sheets (82) includes at least two magnet pairs (84). The generator rotor assembly according to any one of claims 1 to 22.

24. Each of the segment sheets (82) is sized such that all the segment sheets (82) constitute 360 degrees to form an annular layer (80). The generator rotor assembly according to any one of claims 1 to 23.

25. The generator rotor assembly according to any one of claims 1 to 24, having no central hub for supporting the generator rotor assembly and being configured to be self-supporting.

26. A wind turbine comprising a generator having the generator rotor assembly (4) according to any one of claims 1 to 25.

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