Powertrain Assembly for Wind Turbines

Abstract

A wind turbine nacelle including an outer cover defining an interior volume and in which a powertrain assembly is housed includes a gearbox including an input shaft and an output shaft aligned on a common rotation axis, and a generator connected to the output shaft of the gearbox, the generator including a generator cabinet enclosing a stator at a radially outer position and a rotor at a radially inner position within an interior chamber, the rotor being rotatable about the common rotation axis, the rotor having a cylindrical field structure coupled to a rotor support frame and a gearbox connection flange coupled to the output shaft of the gearbox by a first fixed array, the generator cabinet including an opening allowing maintenance personnel to fully access the interior of the interior chamber, the interior chamber being configured to allow maintenance personnel to access at least the first fixed array coupling the gearbox output shaft to the gearbox connection flange from a fully interior position within the interior chamber.

Description

[Technical field]

[0001] The present invention relates in particular to a powertrain assembly for a wind turbine. [Background technology]

[0002] Wind turbines use a large rotor with many rotor blades to convert kinetic energy from the wind into electrical energy. A typical horizontal axis wind turbine (HAWT) includes a tower, a nacelle on the tower, a rotor hub attached to the nacelle, and multiple wind turbine rotor blades coupled to the rotor hub. Depending on the wind direction, the nacelle and rotor blades are rotated and pointed in the optimal direction by a yaw system that rotates the nacelle and a pitch system that rotates the blades.

[0003] The nacelle houses many of the functional components of the wind turbine, including, for example, the main rotor shaft, the gearbox and the generator, as well as a conversion device that converts the mechanical energy in the rotor into electrical energy for supply to the power grid. The gearbox increases the rotational speed of the low-speed main shaft and drives the gearbox output shaft. The gearbox output shaft then drives a generator that converts the rotation of the gearbox output shaft into electricity. The electricity produced by the generator may be converted as required before being supplied to appropriate consumers, for example to the power grid 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 the main rotor shaft.

[0004] Wind turbine generators are typically IPM (interior permanent magnet) electric machines consisting of an outer stator assembly surrounding an inner rotor assembly. The IPM inner rotor assembly typically consists of a ring-like structure containing multiple annular permanent magnet packages supported on a central shaft. A gearbox output shaft contacts the central shaft of the rotor assembly. Summary of the Invention Problems that the invention solves and constitutes

[0005] WO2020 / 143888A1 shows a particular type of IPM electric machine for use as a generator of a wind turbine. In this example, a ring-like structure is supported at one end by an annular support frame. The absence of a central hub in the rotor assembly provides many important advantages, such as reduced cost and weight, and improved cooling airflow. 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. However, it is desirable to further improve this design, for example to increase the maintainability of the assembly.

[0006] The object of the present invention is to provide a solution to one or more of the problems mentioned above.

[0007] According to one aspect of the present invention, there is provided a wind turbine nacelle including an outer cover defining an internal volume and in which a powertrain assembly is housed, the wind turbine nacelle including a gearbox including an input shaft and an output shaft aligned on a common rotation axis, and a generator connected to the output shaft of the gearbox, the generator including a generator cabinet enclosing in an internal chamber a stator at a radially outer position and a rotor at a radially inner position, the rotor being rotatable about the common rotation axis, the generator cabinet including an opening allowing maintenance personnel to fully access the interior of the internal chamber, the internal chamber being configured to allow maintenance personnel to access at least the first fixed array coupling the gearbox output shaft to the gearbox connection flange from a fully internal position of the internal chamber.

[0008] An advantage of the present invention is that the powertrain assembly includes a gearbox coupled to a generator that is specifically configured to facilitate the maintenance process. Typically, a powertrain system that includes a gearbox coupled to a generator requires all maintenance to be performed from an access point external to the generator. However, in the powertrain assembly of the present invention, the generator cabinet defines an interior chamber that a maintenance technician can fully climb into to access various components of the generator system from a position entirely inside the generator cabinet. This means that there is no need to access components from outside the generator, as full access is possible when the maintenance technician's entire body is located within the interior chamber. This is not possible with known systems.

[0009] In one embodiment the gearbox is an epicyclic gearbox with at least two stages. This provides a particularly space efficient system where the gearbox and generator are located in-line.

[0010] In addition to the first fixed array, the interior chamber can be configured to allow maintenance personnel full internal access to other components such as the second fixed array that couples the gearbox connection flange to the rotor support frame, the tie rod system, the rotor balance mass, the drive ring gear, etc.

[0011] Usefully, the rotor inner diameter defined by the cylindrical field structure may be greater than 2m, or even greater than 2.2m, to provide space for maintenance personnel.

[0012] The generator cabinet and rotor may be advantageously configured to maximize interior space for maintenance personnel. For example, the rotor connection flange of the rotor support frame may be spaced from the gearbox connection flange along the axis of rotation by a distance that is at least 25% of the maximum outer diameter of the rotor support frame. The gearbox connection flange may define a first diameter, where the tie rod system may define a second diameter, where the first diameter is smaller than the second diameter, where the first diameter may be smaller than 0.7m and the second diameter may be greater than 2m, and the rotor connection flange of the rotor support frame is spaced from the gearbox connection flange along the axis of rotation by a distance that is 20% to 60%, preferably 20% to 40%, of the inner diameter of the rotor connection flange.

[0013] In one embodiment, the rotor support frame may define access openings. These openings are particularly useful for accessing components outside of the rotor support frame. For example, the access openings may provide access to at least one of the following generator components: i) a stray current protection system, ii) one or more rotational sensor components associated with the gearbox output shaft, iii) an accelerometer system, iv) a temperature sensor, and v) a pitch tube seal component. In a preferred embodiment, access via the openings may be achieved to at least two of the aforementioned components, and at least three of the aforementioned components.

[0014] The present invention encompasses a wind turbine including the tower and nacelle described above.

[0015] The invention also extends to a method of maintaining a wind turbine powertrain in a nacelle of a wind turbine, the powertrain including a gearbox including an input shaft and an output shaft aligned on a common axis of rotation, and a generator connected to the output shaft of the gearbox, the generator including a generator cabinet defining an interior chamber allowing access for maintenance personnel into the generator cabinet, the generator cabinet housing a stator at a radially outer position and a rotor at a radially inner position, the rotor being rotatable about the common axis of rotation, the rotor including a cylindrical field structure coupled to a rotor support frame and a gearbox connection flange (80) coupled to the output shaft of the gearbox by a first fixed array, the interior chamber allowing access for maintenance personnel into the generator cabinet, the method including accessing the interior chamber of the generator through an opening defined by the generator cabinet and performing maintenance operations from a position entirely inside the interior chamber.

[0016] In a particularly beneficial aspect, the maintenance activity can include servicing at least one of: i) the second fixed array connecting the gearbox connection flange to the rotor support frame; ii) the tie rod system connecting the rotor support frame to the cylindrical field structure; iii) the plurality of balancing masses configured to provide rotational balance to the cylindrical field structure; and iv) the drive ring gear by maintenance personnel from a position entirely inside the inner chamber.

[0017] The generator cabinet may comprise one or more closure elements configured to selectively close the opening formed by the generator maintenance cabinet into the internal chamber. The generator cabinet thus results in a normally closed environment for service purposes to which service engineers can access when necessary. To ensure that access is only possible under safe conditions, a suitable access control system may be associated to the closure device. A closed environment therefore means that the service area can be more easily kept away from contamination.

[0018] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a front view schematic diagram of a known wind turbine configuration. [Diagram 2] FIG. 2 is a diagram of example powertrain components that may be housed within a nacelle of the wind turbine of FIG. 1. [Diagram 3] FIG. 1 is a cutaway view of a known arrangement including a generator coupled to a gearbox shown at axially spaced positions; [Figure 4] FIG. 4 is a perspective view of the generator rotor assembly of the known generator of FIG. 3, viewed from the non-drive end. [Diagram 5] FIG. 5 is a drive end perspective view of the generator rotor assembly shown in FIG. 4. [Figure 6] 1 is a longitudinal cross-sectional view of a generator rotor assembly according to an embodiment of the present invention, partially shown diagrammatically positioned within a generator service cabinet, the generator rotor assembly including a cylindrical field structure fitted to a rotor support hub or frame and usable within a generator as shown in the previous figure; [Figure 7] FIG. 7 is a perspective view of the generator rotor assembly of FIG. 6 with the generator service cabinet separated. [Figure 8] FIG. 7 is another front perspective view of the generator rotor assembly of FIG. 6, but with the cylindrical field structure omitted. [Figure 9] FIG. 8 is a perspective view of the generator rotor assembly of FIG. 7 from the non-drive end. [Figure 10] FIG. 10 is an end view of the generator rotor assembly of FIGS. 6-9 within its respective generator cabinet, showing a maintenance technician standing within the support frame to access the internal components. [Figure 11] 11A and 11B show end views similar to those of FIG. 10, but with the access door in a closed position in FIG. 11A and in an open position in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, specific embodiments of the present invention are described, with numerous details being set forth in order to provide a thorough understanding of the inventive concepts defined in the claims. However, it will be apparent to those skilled in the art that the present invention may be practiced without the specific details, and in some instances, well-known methods, techniques, and structures have not been described in detail in order not to unnecessarily obscure the present invention.

[0021] The present invention relates generally to a generator arrangement that has several advantages related to the serviceability of the generator and the associated gearbox to which it is connected. In particular, the generator arrangement provides maintenance technicians with improved access to the generator's interior, a key advantage within the confines of a wind turbine nacelle, allowing various types of adjustments to be made without the need to dismantle all or part of the generator.

[0022] To place embodiments of the present invention in the proper context, reference is first made to Figure 1, which illustrates a typical horizontal axis wind turbine (HAWT) in which a generator rotor assembly according to embodiments of the present invention may be implemented. While this particular image illustrates an onshore wind turbine, it will be understood that similar features are found in offshore wind turbines. Furthermore, although wind turbines are referred to as "horizontal axis," those skilled in the art will understand that for practical purposes, the axis is typically slightly tilted to prevent contact between the rotor blades and the wind turbine tower during high winds.

[0023] Wind turbine 1 includes a tower 2, a nacelle 4 rotatably coupled to the top of tower 2 by a yaw system, a rotor hub 8 attached to nacelle 4, and a number of wind turbine rotor blades 10 coupled to rotor hub 8. The nacelle 4 and rotor blades 10 are rotated and pointed into the direction of the wind by the yaw system.

[0024] The nacelle 4 houses many of the functional components of the wind turbine, including the generator, gearbox, and rotor brake assembly, as well as the conversion equipment that converts the mechanical energy of the wind into electrical energy for supply to the power grid. FIG. 2 shows an example of a layout within the nacelle 4, which includes a main bearing housing 20, a gearbox 22, and a main shaft 26 that extends through the generator 24. The main shaft 26 is connected to and driven by the rotor 8, providing input drive to the gearbox 22. Collectively, these components can be considered the powertrain of the wind turbine. The gearbox 22 increases the rotational speed of the low speed main shaft through internal gears (not shown), which drive the gearbox output shaft. The gearbox output shaft drives the generator 24, which converts the rotation of the gearbox output shaft into electricity. The electricity produced by the generator 24 may be converted as necessary by other components (not shown) before being supplied to appropriate consumers, such as the power grid distribution system.

[0025] The gearbox 22 and the generator 24 may be coupled together as an integrated unit. FIG. 3 shows the generator 24 in more detail. Referring initially to the gearbox 22, the gearbox housing is generally cylindrical in shape due to the particular type of gearbox used in the illustrated embodiment, a planetary gearbox. As those skilled in the art will know, a planetary gearbox comprises a series of planetary gears arranged around a central sun gear, which are generally arranged within a surrounding ring gear. A typical configuration of a gearbox is such that the input and output shafts are arranged on a common axis. The ratio of the number of teeth between the ring gear, the planetary gears, and the sun gear determines the gear ratio of the gearbox. For clarity, the details of the gearbox are not the focus of the present invention and will not be described in further detail here. Although other gearbox configurations may be used, it is currently believed that a planetary gearbox provides an elegant solution to meet the constraints of a wind turbine nacelle. Such a planetary gearbox may include multiple planetary gear stages, for example one, two or three planetary gear stages.

[0026] With further reference to the cutaway view of FIG. 3, but also with reference to FIGS. 4 and 5, the generator 24 is an IPM (interior permanent magnet) electric machine having an outer stator assembly 30 surrounding an inner rotor assembly 32. The stator assembly 30 includes stator windings 38, a stator core 40, and a stator frame (not shown) that surrounds and supports the stator windings 38 and the stator core 40. However, it should be noted that the present invention is not limited to a particular type of stator. In particular, the internal configuration of the generator 24 shown in FIG. 3 is provided herein as an example and to give a proper context for the present invention. The particular configuration of the generator rotor 32 in FIGS. 3-5 does not form part of the present invention, but is provided to better understand the configuration of a generator rotor according to an embodiment of the present invention, as described below with reference to FIGS. 6-11.

[0027] The gearbox 22 is coupled to the generator 24 via an output shaft 31 that connects to a rotor assembly 32 of the generator 24. The longitudinal axis of the gearbox output shaft 31 thus defines the axis of rotation of the generator 24. In particular, the gearbox also includes an input shaft 33 that is coaxially aligned with the gearbox output shaft 31. The generator rotor assembly 32 is shown in situ within the generator 22 in cross-section in Figure 3, but is shown separated in Figures 4 and 5.

[0028] The generator rotor assembly 32 has a drive end 34 and a non-drive end 36. The drive end 34 faces toward the gearbox 22 and the non-drive end 36 faces away from the gearbox 22. The non-drive end 36 of the generator rotor assembly 32 is shown in FIG. 4 and the drive end 34 of the generator rotor assembly 32 is shown in FIG. 5.

[0029] The generator rotor assembly 32 includes a cylindrical ring structure 40 that defines a hollow central region and is arranged to rotate about the axis of rotation. The cylindrical ring structure 40 includes a plurality of solid circular rotor bars 42 that house permanent magnet packages. The ring structure 40 thus serves to generate the rotating magnetic field of the generator when in use. Here, the bars 42 are shown as having equal circumferences and thicknesses, although this may vary. The bars 42 are arranged coaxially about the axis of rotation, and when assembled, the arrangement of the bars 42 is such that it defines a cylindrical structure having a central hollow region. The bars 42 are spaced equal distances apart such that gaps are defined between each pair of the bars 42. These gaps allow air supplied to the center of the generator to flow through the rotor structure to cool the generator rotor assembly and other components of the generator, including portions located radially outward of the rotor assembly 32. This air flow is further enhanced by the fact that a central hub is not required to provide structure and support for the rotor assembly 32.

[0030] The cylindrical ring structure 40 is connected to a rotor support frame 50. The rotor support frame 50 includes a first radially outer connection flange 52, best shown in FIG. 4, and a second radially inner connection flange 54, best shown in FIG. 5. The first connection flange 52 serves to connect the bar 42 to the rotor support frame 50 and may be considered the "rotor connection flange," and the second connection flange 54 serves to couple the rotor support frame 50 to the gearbox output shaft 31 and may be considered the "gearbox connection flange." A set of connection bolts 56 used to secure the support frame 50 to the gearbox output shaft 31 can be seen extending perpendicularly from the second connection flange 54 in FIG. 5.

[0031] The support frame 50 and the cylindrical ring structure 40 are connected together by a number of tie rods 58 (only two of which are shown in Figures 4 and 5) which extend axially through holes in each of the bars 42 and are secured via the rotor connection flange 52 of the support frame 50. A suitable mechanical fastener, such as a bolt, is provided at the end of each tie rod 58 and is tightened to place the package of bars 42 in compression, thereby rigidly securing the cylindrical ring structure 40 to the support frame 50 as an integral unit.

[0032] It should be noted that the rotor connection flange 52 and the gearbox connection flange 54 are axially facing surfaces that extend in respective parallel but spaced apart planes along the rotor axis. In this regard, the gearbox connection flange 54 extends somewhat into the hollow interior region defined by the cylindrical ring structure. Additionally, the circumference of the gearbox connection flange 54 is smaller than that of the rotor connection flange 52.

[0033] The support frame 50 further includes a transition section 69 extending between the rotor connection flange 52 and the gearbox connection flange 54. The transition section 60 is generally frusto-conical and extends at a steep angle relative to the rotor axis. As shown, the transition section 60 defines an angle of approximately 70 degrees to 80 degrees relative to the rotor axis. In other words, the transition section 60 has a cone angle of approximately 140 degrees to 160 degrees.

[0034] When the generator is assembled, the generator rotor assembly 32 is surrounded by the outer stator 30. Both the rotor assembly 32 and the stator 30 are then surrounded by a generator housing or cabinet 68, best seen in FIG.

[0035] With respect to the known configuration of generator rotor assembly 32 as described above, it should be appreciated that while this configuration offers various advantages with respect to generator design and efficiency, it also presents challenges, for example, limited access to the interior of the generator making it problematic for maintenance engineers to access the interior of the generator to check the internal components and take remedial action if necessary.

[0036] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention include improved configurations for generator rotor assemblies that address these issues.

[0037] The illustrated embodiment provides a generator rotor assembly 70 that is functionally equivalent to the known configuration of generator rotor assembly 32 described above. However, the embodiment of the present invention provides several advantageous aspects, as will be explained in further detail in this description.

[0038] 6 shows the generator rotor assembly 70 in partial schematic view with respect to the surrounding components of the generator housing or "cabinet" 81, while FIGS. 7-9 show the generator rotor assembly 70 separated from the generator cabinet 81. At this point it should be noted that the generator rotor assembly 70 of the illustrated embodiment shares many similarities with that previously described, and so only the differences will be focused on here.

[0039] In general terms, the generator rotor assembly 70 includes a rotor support frame 72 which supports a cylindrical field structure 74 which acts as a magnet carrier in use to generate a rotating magnetic field. The configuration of the cylindrical field structure 74 is similar to that described with reference to Figures 3 to 5 and therefore further detailed description of this assembly will be omitted.

[0040] The generator rotor assembly 70 includes a drive end 76 and a non-drive end 78. The drive end 76 is connectable to an output drive shaft 77 of the gearbox 22, and the non-drive end 78 is distal from the gearbox 22. In essence, the generator rotor assembly 70 can be considered to be rotatably suspended from the gearbox output shaft 77 in a cantilevered manner, as the non-drive end is not rotatably supported by a bearing.

[0041] Essentially, rotor support frame 72 provides a means for connecting gearbox output shaft 77 to cylindrical field structure 74. To this end, rotor support frame 72 includes a gearbox connection flange 80 and a rotor connection flange 82.

[0042] The gearbox connection flange 80 and the rotor connection flange 82 are both axially facing surfaces oriented perpendicular to and spaced apart from one another along the axis of rotation R of the generator rotor assembly 70. Thus, both flanges 80, 82 extend in a plane perpendicular to the axis of rotation R in the illustrated embodiment.

[0043] The gearbox connection flange 80 includes an annular locking slot arrangement 84, through which the rotor support frame 70 is connectable to the gearbox output shaft 77 by a set of suitable bolts (not shown). The locking slot arrangement 84 thus defines a first pitch diameter, shown in FIG. 10 as "D1."

[0044] The rotor connection flange 82 is coaxial with the gearbox connection flange 80 and has a larger diameter. The rotor connection flange 82 is fixed to the cylindrical field structure 74 by a tie rod system 86 comprising a plurality of circumferentially spaced tie rods 88 extending through the individual bars of the cylindrical field structure 74, as in the previous embodiment. The circular arrangement of the tie rods 88 thus defines a second pitch diameter, shown as D2 in FIG. 6. As shown, the first pitch diameter is smaller than the second pitch diameter D2. In the illustrated embodiment, the first pitch diameter D1 is about 30% of the second pitch diameter D2.

[0045] Preferably, the tie rod system 86 includes a balancing means for adjusting the rotational balance of the cylindrical field structure 74. The balancing means can be achieved by adding shims or washers captured between the rotor connection flange 82 and the tie rod fasteners 89, such as hex nuts. Tension of the tie rods 88 can be achieved by appropriately rotating the respective fasteners 89 that apply a compressive force to the cylindrical field structure 74, while adjustment of the rotational balance can be achieved by adding or removing balancing shims around the array of tie rods 88 until the optimum rotational balance is obtained.

[0046] A transition section 90 extends between the gearbox connection flange 80 and the rotor connection flange 82. The function of the transition section 90 is to provide rigidity to the rotor support frame 72 while maintaining the rotor connection flange 82 and the gearbox connection flange 80 in a spaced apart relationship to promote good airflow through the structure.

[0047] As can be readily seen, the transition section 90 includes two main portions, a first frusto-conical portion 92 and a second axially-facing surface portion 94. The frusto-conical portion 92 is adjacent the rotor connection flange 82 and the axially-facing surface portion 94 is adjacent the gearbox connection flange 80.

[0048] Because the frusto-conical portion 92 is oriented at a shallow angle relative to the axis of rotation, it includes a number of relatively flat regions 96 (not all of which are visible in the figures for clarity). Because each region 96 extends axially at a relatively shallow angle relative to the axis of rotation, they provide an area suitable for supporting a maintenance technician within the rotor support frame 72. Thus, each region 96 can be considered a stepping region. In the illustrated embodiment, there are a total of nine stepping regions 96.

[0049] Each stepping region 96 is distinguished from an adjacent region by a reinforcing rib or web 98. The reinforcing ribs 98 contribute to the stiffness of the transition section. Here, the stepping regions 96 are embodied as relatively thin plate-like portions.

[0050] Here, while the illustrated embodiment includes multiple step regions 96, it should be understood that this is not required and instead, the transition section 90 may define any number of step regions, including only a single continuous step region that defines a curved surface that extends circumferentially substantially uninterrupted around the transition section 90.

[0051] As seen in FIG. 11, the stepping area 96 provides an advantageously stable surface or platform that is sufficiently flat to support a maintenance technician within the internal chamber 97 that is also enclosed by the rotor support frame 72 and thus the generator cabinet 81. This aspect also benefits from various other aspects of the rotor support frame, particularly its internal dimensions. For example, the internal diameter of the rotor connection flange is greater than 1.8 m, but could be greater than 2.0 m or even greater than 2.2 m. This provides adequate headroom for the maintenance technician within the rotor support frame 72. This aspect can be further appreciated by observing the transition section 60 in FIGS. 3 to 5, which defines a much steeper angle with respect to the axis of rotation that limits the amount of space within the rotor assembly. Moreover, the steep surface provided by the transition section 60 does not allow a maintenance technician to stand comfortably or safely.

[0052] A further useful aspect of the rotor support frame 72 is the axial dimension between the rotor connection flange 82 and the gearbox connection flange 80. In the illustrated embodiment, the dimension designated "A" (see FIG. 6) denotes the length along the axis of rotation between the rotor connection flange 82 and the gearbox connection flange 80. Dimension A is preferably greater than 0.5 m, providing a useful "depth" to the interior chamber 97 of the rotor support frame 72 to accommodate maintenance personnel completely therein. Even more preferably, dimension A is greater than 0.6 m.

[0053] The depth of the internal chamber 97 of the rotor support frame 72 also benefits from the shallow angle of the stepped region 96. As seen in FIG. 6, the stepped region 96 defines an angle of less than 30 degrees with respect to a line parallel to the axis of rotation. This angle is shown as "B" in FIG. 6. Stated another way, a portion of the transition section 90 defines a cone angle of less than 60 degrees. The shallow angle that the truncated cone portion defines with the rotor axis R contributes to the depth of the internal chamber 97 of the cylindrical field structure 74.

[0054] As mentioned above, the internal dimensions of the internal volume 97 of the rotor support frame 70, both its inside diameter and depth "A", allow a maintenance technician to climb into its interior and access its various components and other components associated with the generator, a significant advantage as it means that the maintainability of the generator is significantly improved.

[0055] In addition to defining a step region 96, the transition section 90 further includes an axially-facing surface portion 94. The axially-facing surface portion 94 defines the drive end 76 of the transition section 90 such that the outer surface of the transition section 90 rotates approximately 90 degrees to present a flat end surface that is substantially perpendicular to the axis of rotation R. Advantageously, a reinforcing rib 98 extends along the step region 96 in a direction aligned with the axis of rotation and extends between the step region 96 and the axially-facing surface portion 94.

[0056] The axially facing surface portion 94 includes an array of access openings 100 extending through the depth of the axially facing surface portion 94 .

[0057] The access openings 100 are arranged in a circular array in this embodiment and are equally spaced angularly. In the illustrated embodiment, there are nine access openings 100 in total, arranged in one configuration per stepping region 96. The circular array of access openings 100 is radially inward of the stepping regions 96 and radially outward of the gearbox connection flange 80. In this sense, they can be considered to be radially disposed between the gearbox connection flange 80 and the stepping region 96.

[0058] The access openings 100 provide access through the rotor support frame 72 to allow a maintenance technician to perform a range of tasks such as monitoring components of the gearbox output shaft, such as bearing sensors (temperature sensors and accelerometers) and rotary encoders. To this end, the access openings should be of suitable cross-sectional area to allow a maintenance technician to reach through one of the openings and reach as far as necessary. To this end, each of the access openings should be at least 100 cm 2 If necessary, larger sizes should provide an opening area of ​​at least 200 cm 2 Advantages include providing a larger access area and improving visibility through the opening.

[0059] While the rotor support frame 70 functions as a single component connecting and transmitting drive between the gearbox output shaft and the cylindrical field structure 74, in the illustrated embodiment, the rotor support frame 72 preferably includes at least first and second components, here designated 102 and 104, respectively. If desired, the components may be cast, for example, from a suitable grade of steel. The first component 102 is radially inward of the second component, and together both components function as the hub of the cylindrical field structure 74. The first component 102 may therefore be considered the "inner hub component" 102, and the second component 104 may therefore be considered the "outer hub component" 104.

[0060] As can be seen, the gearbox connection flange 80 is part of the inner hub component 102 and is separate from the outer hub component 104 that defines the transition section 90 and the rotor connection flange 82. The two components 102, 104 are connected by a circular array 106 of bolts that is radially outside the access opening 100. Notably, the circular array 106 has a pitch diameter marked D3 in FIG. 6. The pitch diameter D3 of the circular array 106 is larger than the pitch diameter D1 of the fixed array 84. In this manner, manufacturing the rotor support frame 72 from at least two components provides manufacturing advantages. Moreover, this configuration allows convenient access to components associated with the generator. For example, it is possible to disassemble the inner hub component 102 from the rotor support frame 72 once the rotor assembly 70 is locked against rotational and radial movement. The inner hub component 102 can therefore be removed from the gearbox by removing the circular array of bolts 84 that connect the rotor support frame 72 to the gearbox output shaft 77, thereby allowing access, maintenance and removal / replacement of the bearing cassette (not shown) associated with the gearbox 22 without requiring complete disassembly of the generator.

[0061] The rotor support frame 72 further includes an extension 110. The extension 110 extends from an outer edge of the non-drive side of the rotor connection flange 82 and is cylindrical. The axial dimension of the extension 110 is approximately half the axial length of the cylindrical field structure 74. In the illustrated embodiment, the extension 110 is a thin-walled cylinder having a diameter approximately equal to the outer diameter of the rotor connection flange 82.

[0062] The non-drive end of the extension 110 also supports a ring gear 112 that engages one or more drive motors 114. Here, the ring gear 112 is shown bolted to the extension 110 with a bolt ring 111. The ring gear 112 and drive motor 114 provide a means by which the direction of rotation of the generator rotor assembly 70 can be controlled during maintenance. For example, a maintenance technician may need to access a particular portion of the generator that requires rotating the generator to a particular position. The ring gear 112 and drive motor 114 also provide a means for rotating the gearbox and main shaft through the generator rotor assembly 70. Thus, it can be considered that the axial dimension of the ring gear 110 is determined, at least in part, based on the required position of the ring gear 112. In the illustrated embodiment, the extension 110 also defines a plurality of air flow openings 115. The air flow openings 115 could in principle be any shape, but as shown here, there are a plurality of openings 115 distributed circumferentially around the extension 110 that allow air to flow radially outward. The airflow openings 115 may be configured to be completely open or may be provided with a perforated cover, such as a grill, to ensure that debris or loose parts cannot pass through the openings 115. In addition to the airflow openings 115 defined in the extension portion 110, the rotor support frame 72 also includes second airflow openings 116 (best shown in FIGS. 8 and 9) located at a radially inward position relative to the first airflow openings 115. The second airflow openings 116 are distributed circumferentially around the transition section 90 and are equiangularly spaced in this embodiment. More specifically, each opening 116 is located at an elbow where the transition section 90 is defined by a sharp bend in the rotor connection flange 82. Each opening 116 also includes an associated guide channel 117 that extends axially along the transition section 90 a short distance from the respective opening 116. The guide channels 117 are formed as recesses or notches in the surface of the transition section 90. The number of second air flow openings 116 is not critical, but in the illustrated embodiment, there are two openings 116 for each stepping region 96 .Note that the second airflow openings 116 are at an outer radial location compared to the access openings 100. Both sets of openings 100, 116 provide airflow advantages; however, having both sets of openings 100, 116 at spaced radial locations promotes a more uniform flow of air through the rotor support frame.

[0063] The extension 110 also supports a brake disc 118 which is fixed to the bolt ring 111 and thus at a radially outward position relative to the ring gear 112. The brake disc 118 is mounted in the generator service cabinet 81 and is actuated by a set of brake actuators 119 which are best seen in FIG.

[0064] From the above discussion, it will be appreciated that the configuration of various aspects of the generator rotor assembly in the illustrated embodiment enhances the serviceability of various components of the generator, particularly the generator rotor assembly. For example, the size of the interior volume of the rotor support frame 72 means that a maintenance technician can access the inside of the generator. This can be useful for at least one of the following purposes. First, it allows 360 degree access to the tie rod system 86, associated tension nuts 89, and balancing mass 87, allowing a technician to make appropriate adjustments to these components about the entire circumference of the rotor support frame 72 while remaining in a single location inside the generator. This provides a significant advantage since adjustments can be made quickly without disassembling the machine. Additionally, a technician inside the generator has 360 degree access to the circular array 106 of bolts connecting the gearbox connection flange 80 to the transition section 90, and also has 360 degree access to the circular array 84 of bolts connecting the rotor support frame 72 to the gearbox output shaft, allowing for quick inspection of these bolt connections, which is a significant advantage during the maintenance inspection process. Also, as mentioned above, this allows removal of the inner hub component 102 to provide access to the gearbox shaft 77, thereby allowing removal and replacement of the bearing cassette. Additionally, the large space inside the generator allows a technician 360 degree access to the bolted connection between the ring gear 112 and the extension 110, as well as similar access to the drive motor 114 which engages the ring gear 112.It should also be appreciated that in addition to the various components described and illustrated in the figures, the access openings 100 and the general configuration of the rotor support frame 72 facilitate access to other internal generator components, such as a radial rotor locking system provided to lock the rotor against radial movement during maintenance, an axial rotor locking system provided to lock the rotor against axial movement, a stray current protection system, a rotary encoder which may be provided on the gearbox output shaft, other sensor systems such as accelerometers and temperature sensors which may be located on the gearbox output shaft and elsewhere, brake disc components provided to apply a braking force to the rotor during maintenance, and pitch tube seal components provided to provide a suitable seal for the pitch tube components which extend through the center of the powertrain assembly to supply hydraulic pressure and / or power to a hydraulic pitching system located at the rotor hub.

[0065] Considered as a whole, the configuration of the rotor support frame 72 provides a relatively open volume therein that is advantageously sized and shaped to provide access for personnel to perform various maintenance activities. The volume may therefore be considered to define a maintenance room within the generator that is sized and shaped to accommodate maintenance personnel. This is in contrast to known approaches in which access to various components is achieved only from outside the generator or where access from within the generator is limited by the relative placement of the internal components.

[0066] Advantageously, the open volume inside the generator rotor assembly 70 can be sealed to provide a more protective environment, but still allow access for maintenance personnel if required. As shown in Figures 11a and 11b, the rear of the generator service cabinet 81 can be provided with a closure 120, such as a door or hatch. The closure 120 can be a single door panel that covers an opening 121 in the generator cabinet 81 to the interior chamber in which the generator rotor assembly 70 is housed. Alternatively, the closure 120 can comprise multiple panels. As shown, the closure 120 comprises two door panels 122, 124. These door panels 122, 124 can be attached in any suitable manner to allow opening. For example, the door panels 122, 124 can be attached by a fastening system that allows one or both of the panels to be lifted out of the cabinet opening when access to the generator interior is required. Alternatively, one or both of the door panels 122, 124 can be hinged so that they remain connected to the generator service cabinet 81, but can be moved to gain access if required. FIG. 11b shows one of the door panels 124 having hinged fastenings, it will be understood that the other door panel 122 may have similar fastenings.

[0067] Beneficially, the closure 120 encloses the internal volume of the generator, which means that the internal environment is isolated from the general interior of the nacelle in which the generator is installed.

[0068] The enclosure 120 achieves a further advantage in that it can provide a single service entry point to the internal volume of the generator for maintenance purposes. This means that closure can be performed with a single safety mechanism to allow controlled entry for maintenance. The safety mechanism can be by keypad, finger scanner, or other access control technology. Preferably, access through the enclosure is only allowed when the safety mechanism detects that there is no electrical risk associated with maintenance personnel accessing the inside of the generator, as one or more other safety means or interlocks have been activated, e.g. the rotor has been locked so that it is secured, and appropriate electrical systems have been deactivated.

[0069] The internal volume inside the generator is provided as a service room with sufficient space so that this area can be designed as a dedicated work space for accessing the many structures and systems associated with the generator, as described above. For example, a floor covering can be installed in the service room to catch any fallen items, thereby avoiding the risk of losing parts inside the generator. Furthermore, the closed environment of the service room means that the closure 120 allows the area accessible from the service room to be kept as clean as possible, which is easier to achieve on a small scale than requiring a fully clean nacelle boundary.

[0070] Many modifications may be made to the particular examples described above without departing from the scope of the invention as defined in the appended claims. Features of one embodiment may be used in other embodiments in addition to, or as an alternative to, such embodiments.

Claims

1. 1. A wind turbine nacelle including an outer cover defining an interior volume, a powertrain assembly housed within the outer cover, a gearbox (22) including an input shaft (33) and an output shaft (31) aligned on a common rotation axis (R); a generator (24) connected to the output shaft of the gearbox, the generator including a generator cabinet (81) enclosing within an internal chamber (97) a stator (38) at a radially outer position and a rotor (70) at a radially inner position, the rotors being rotatable about the common rotation axis; a cylindrical field structure (74) coupled to a rotor support frame (72); a gearbox connection flange (80) coupled to the output shaft of the gearbox by a first fastening array (84); 1. A wind turbine nacelle, comprising: a generator cabinet (81) having an opening (121) that allows maintenance personnel to fully access the interior of the internal chamber (97), the internal chamber being configured to allow maintenance personnel to access at least a first fixed array (84) coupling the gearbox output shaft (31) to a gearbox connection flange (80) from a position entirely within the internal chamber (97).

2. 2. The wind turbine nacelle of claim 1, wherein the rotor further includes a second fixed array (106) coupling the gearbox connection flange (80) to the rotor support frame (72), and the interior chamber (97) is configured to allow maintenance personnel to access the second fixed array (106) from within the interior chamber.

3. 3. The wind turbine nacelle of claim 2, wherein the first stationary array (84) has an associated pitch diameter (D1) and the second stationary array (106) has an associated pitch diameter (D3), the pitch diameter (D1) of the first stationary array (84) being smaller than the pitch diameter (D3) of the second stationary array (106).

4. 4. The wind turbine nacelle of claim 1, wherein the rotor support frame is coupled to the cylindrical field structure at a rotor connection flange by a tie rod system including a plurality of tie rod tensioners configured to provide tension to the tie rod system, and the interior chamber is configured to allow maintenance personnel to access the tie rod tensioners from within the interior chamber.

5. 5. The wind turbine nacelle of claim 4, wherein the tie rod system (86) includes a plurality of balancing masses (87) configured to provide rotational balance to the cylindrical field structure (74), and the interior chamber (97) is configured to allow maintenance personnel to access the balancing masses (87) from within the interior chamber.

6. 6. The wind turbine nacelle of claim 1, wherein the rotor further comprises a drive ring gear, and the interior chamber is configured to allow maintenance personnel to access the drive ring gear from within the interior chamber.

7. The wind turbine nacelle of any one of claims 1 to 6, wherein the cylindrical field structure (74) defines an inner rotor diameter greater than 2m.

8. A wind turbine nacelle according to any one of claims 1 to 7, wherein the gearbox is an epicyclic gearbox having at least two stages.

9. 6. The wind turbine nacelle of claim 4 or 5, wherein the gearbox connection flange (80) defines a first diameter (D1) and the tie rod system (86) defines a second diameter (D2), the first diameter (D1) being smaller than the second diameter (D2).

10. 10. The wind turbine nacelle of claim 9, wherein the first diameter (D1) is smaller than 0.7 m and the second diameter (D2) is larger than 2 m.

11. 11. The wind turbine nacelle of claim 4, 5, 9, or 10, wherein the rotor connection flange (82) of the rotor support frame (72) is spaced along the axis of rotation from the gearbox connection flange (80) by a distance of at least 25% of a maximum outer diameter of the rotor support frame (72).

12. The wind turbine nacelle of claim 11, wherein the rotor connection flange (82) of the rotor support frame (72) is spaced along the axis of rotation from the gearbox connection flange (80) by a distance less than 0.7 m.

13. 13. The wind turbine nacelle according to any one of claims 4, 5 and 9 to 12, wherein the rotor connection flange (82) of the rotor support frame (72) is spaced apart from the gearbox connection flange (80) along the rotation axis (R) by a distance between 20% and 60%, preferably between 20% and 40%, of an inner diameter of the rotor connection flange.

14. 14. The wind turbine nacelle of any one of claims 4, 5 and 9 to 13, wherein the rotor connection flange (82) and the gearbox connection flange (80) extend in planes parallel to each other.

15. 15. The wind turbine nacelle of claim 4, 5, or 9-14, wherein the rotor support frame (72) further comprises a transition section (90) extending between the rotor connection flange (82) and the gearbox connection flange (80).

16. The wind turbine nacelle of claim 15, wherein the transition section (90) includes a generally frusto-conical portion (92) defining a cone angle (B) less than 30 degrees.

17. The wind turbine nacelle of any one of the preceding claims, wherein the rotor support frame (72) includes a plurality of access openings (100).

18. The access opening (100) is at least 100 cm ２ , preferably at least 200 cm ２ The wind turbine nacelle of claim 17 defining an opening.

19. 19. The wind turbine nacelle of any one of claims 17 to 18, wherein the access opening (100) provides access to at least one of the following generator features: i) a stray current protection system, ii) one or more rotational sensor components associated with the gearbox output shaft, iii) an accelerometer system, iv) a temperature sensor, and v) a pitch tube seal component.

20. 20. The wind turbine nacelle of any one of claims 1 to 19, further comprising a closure (120) covering an opening (121) in the generator cabinet (81), the closure being openable for maintenance personnel to access the entire interior of the internal chamber (97) through the opening (121).

21. 21. A wind turbine comprising a tower and a wind turbine nacelle according to any one of claims 1 to 20 supported on top of the tower.

22. 1. A method of maintaining a powertrain of a wind turbine within a nacelle of the wind turbine, comprising: The power train includes a gearbox (22) including an input shaft (33) and an output shaft (31) aligned on a common rotation axis (R), and a generator (24) connected to the output shaft of the gearbox, the generator including a generator cabinet (81) defining an internal chamber (97) allowing access for maintenance personnel into the generator cabinet, the generator cabinet (81) housing a stator (38) at a radially outer position and a rotor (70) at a radially inner position, the rotor being rotatable about a common rotation axis, the rotor including a cylindrical field structure (74) coupled to a rotor support frame (72) and a gearbox connection flange (80) coupled to the output shaft of the gearbox by a first fixed array (84), The method comprises: accessing the interior chamber (97) of the generator (24) through an opening (121) defined by a generator cabinet (81); and performing maintenance operations from a location entirely inside said interior chamber (97).

23. 23. The method of claim 22, wherein the method of maintaining comprises maintaining, by maintenance personnel from a position entirely inside the interior chamber, at least one of: i) a second fixed array (106) coupling the gearbox connection flange (80) to the rotor support frame (72); ii) a tie rod system (86) coupling the rotor support frame (70) to a cylindrical field structure (74); iii) a plurality of balancing masses (87) configured to provide rotational balance to the cylindrical field structure (74); and a drive ring gear (112).

24. 24. The method of claim 22 or 23, wherein accessing the internal chamber of the generator (24) comprises opening a closure (120) covering an opening (121) in the generator cabinet (81) to expose the opening (121) for accessing the internal chamber (97).

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