Loading and unloading equipment

Abstract

The invention describes a handling device (1) for a wind turbine generator (2), the handling device (1) comprising: a holding frame (11, 12) adapted to receive and hold the generator (2); a height-adjustable platform (14) adapted to engage with a drive end (2DE) of the generator (2); a stator suspension assembly (13) adapted to be mounted on said holding frame (11, 12) and connected to a non-driving end (2NDE) of the stator (22); and a rotation device (131) adapted to rotate the stator suspension assembly (13) about a rotation axis (2A) of the generator (2). The invention also describes a method of performing a generator maintenance process using such a generator handling apparatus (1).

Description

Background Art

[0001] The extended service life of modern, large-scale wind turbines can exceed the lifespan of various major components. Therefore, at some point during the wind turbine's service life, a defective component may need to be replaced. The duration and cost of the maintenance process depend significantly on the accessibility of the defective component. For example, the main bearings of a generator, located at the drive end between the rotor and stator, are difficult to access. In very large-capacity wind turbines with generator diameters of several meters, the bearing replacement process (involving generator disassembly, removal of the defective bearing, installation of a new bearing, and subsequent reassembly of the generator) can take several days. This undesirably long duration is particularly problematic in offshore wind turbines, as chartering jack-up vessels (to carry the heavy equipment and accommodate the replacement process) is prohibitively expensive. Another issue is that the air gap between the rotor and stator is very small (only a few millimeters) but can vary slightly around the circumference of the generator. The "shape" of this air gap is primarily determined by the configuration of the rotor, stator, and main bearings and can be considered unique to each generator. Therefore, after any maintenance task involving removal of the main bearing, it is necessary to restore the shape of the air gap of an already operating wind turbine generator.The known process of monitoring and restoring the air gap is time consuming and expensive.

[0002] It is therefore an object of the present invention to provide a faster and more economical way of performing maintenance procedures for such a wind turbine.

[0003] This object is achieved by the claimed generator handling device and by the claimed method of performing a generator maintenance procedure. Summary of the Invention

[0004] Wind turbine generators of the type discussed herein are understood to have a diameter of approximately 8 m and may weigh hundreds of metric tons. In generator designs with a rotating field winding arranged around a stationary armature, the bearings between the rotor and stator may have a diameter approaching the rotor diameter.

[0005] According to the present invention, the loading and unloading device comprises: a holding frame adapted to receive and hold the generator with its drive end facing downward; a height-adjustable platform adapted to receive the drive end of the stator; a stator suspension assembly adapted to be mounted on the holding frame and connected to the non-drive end of the stator; and a rotating device adapted to rotate the stator suspension assembly about the rotation axis of the generator.

[0006] The generator is loaded and unloaded with its drive end facing downwards, ie the generator is loaded and unloaded in an orientation with its axis of rotation vertical and its drive end facing downwards.

[0007] One advantage of the generator handling apparatus of the present invention is that it significantly reduces the duration of generator maintenance procedures. The primary difficulty in performing maintenance on generators of the type described herein stems from the large size of the components, the weight of the rotor, stator, and main bearings, and the need to avoid any deformation of these components. The handling apparatus of the present invention, with its stator suspension assembly and rotating device, facilitates relatively rapid separation of the front-end assembly for maintenance tasks and restoration of the highly critical air gap shape.

[0008] According to the present invention, a method for performing a maintenance procedure using such a handling device comprises the following steps: placing the generator in the handling device; measuring the generator air gap by means of a rotatable stator suspension assembly; removing the front end assembly from the drive end of the generator and performing the intended maintenance operation; reinstalling the front end assembly; and restoring the generator air gap by means of the rotatable stator suspension assembly.

[0009] Particularly advantageous embodiments and features of the invention are given by the dependent claims, as revealed in the following description. Features from different claim categories can be combined as appropriate to give further embodiments not described herein.

[0010] The generator handling equipment can be used for any part of the generator that may need maintenance during the lifetime of the wind turbine. In the following, a process for replacing a main bearing of a generator is described, and the expressions "generator handling equipment" and "main bearing replacement equipment" are used interchangeably herein.

[0011] In an initial step, the generator is lowered into the holding frame of the handling equipment. After the lifting equipment (e.g., a self-elevating ship crane) is released, the handling equipment must support the entire weight of the generator. However, most of the generator's mass is concentrated in the stator. Therefore, in a particularly preferred embodiment of the present invention, the holding frame is designed to carry the weight of the rotor (rotor housing, magnet assembly, etc.), while the height-adjustable platform is designed to carry the weight of the stator (stator frame, windings, etc.) as well as the weight of the front-end assembly, which can include the front plate, main bearings, and anti-ovalization ring.

[0012] The retaining frame can be any suitable structure large enough to surround or enclose the generator, such as a frame having several upright structures arranged (equidistant or otherwise) around the rotor housing. The stator suspension assembly is understood to be supported by the retaining frame, for example, by a suitable arrangement of beams carried by the upright structures of the retaining frame. In one straightforward implementation, the retaining frame comprises a square or rectangular arrangement with four uprights at each corner.

[0013] The holding frame preferably includes means to securely hold the rotor housing, such as clamps or clips at each of its uprights. These clamps are preferably arranged at a suitable height above the ground so that there is enough space for a height-adjustable platform under the generator.

[0014] The platform is preferably part of a platform assembly, which is preferably equipped with a secure means for raising and lowering the platform, such as an arrangement of hydraulic jacks. In one exemplary embodiment, the platform base or bed (which can travel along rails or tracks) can accommodate four hydraulic jacks arranged to raise and lower the platform as needed. The sides of the platform that receives the front end of the generator are preferably shaped to complement the shape of the front cover, so that when the front end assembly rests on the platform, its weight is evenly distributed across the platform's upper surface.

[0015] The rotation means may be implemented to rotate the stator suspension assembly by any suitable amount, such as a full revolution or a fraction thereof. In a preferred embodiment of the invention, the rotation means is adapted to rotate the stator suspension assembly by 180°, as this is sufficient for the air gap measurement process, as will be explained below.

[0016] During the method of the present invention, the platform is required during the initial and final stages, as well as for certain intermediate stages. However, between these stages, full access to the generator drive end is required. Therefore, in a preferred embodiment of the present invention, the platform is removable from the retaining frame, for example using a ground-level rail system extending from the interior to the exterior of the retaining frame between two uprights.

[0017] A fundamental principle of the present invention is that the handling apparatus can be used to ensure that the air gap is maintained, i.e., the air gap restored between the rotor and stator after the main bearing is replaced is the same as the air gap before the main bearing was removed. This advantageous aspect is facilitated by the stator suspension assembly and rotation device of the handling apparatus of the present invention, as explained below.

[0018] The initial process of placing the generator in the loading and unloading equipment includes: arranging the height-adjustable platform within the holding frame to receive the drive end of the stator; lowering the generator into the holding frame until its drive end rests on the height-adjustable platform; and then connecting the stator suspension assembly to the lifting bracket present at the non-drive end of the stator.

[0019] In a subsequent step, the weight of the stator is transferred to the stator suspension assembly. This can be facilitated by a vertical displacement device suitable for raising the stator suspension assembly. For example, a hydraulic jack can be arranged at the upper end of each column of the holding frame. In such an embodiment, it can be assumed that the handling equipment includes means for actuating these hydraulic jacks collectively and / or individually. To transfer the weight of the stator to the stator suspension assembly, the jacks are carefully extended upwards while monitoring the load on the holding frame and the platform. Eventually, the weight of the stator will be completely carried by the stator suspension assembly, and the platform can then be lowered, and the process of separating the front-end assembly can begin.

[0020] Before removing the front-end assembly from the generator, the method of the present invention includes a step of measuring the generator air gap. To do this, a technician measures the distance between the rotor and stator at several points around the generator circumference and records the measurements. The technician then activates a rotation mechanism to rotate the suspended stator a partial rotation, for example, 180°. The technician again measures the distance between the rotor and stator at several points around the generator circumference and records the measurements. The technician then activates the rotation mechanism to return the suspended stator to its original position.

[0021] The front end assembly can now be removed by first removing the platform, removing the first set of fasteners (which would otherwise be hidden by the platform), returning the platform and raising it to receive the front end assembly, and removing the remaining fasteners. The separated front end assembly, resting on the platform, is now moved out of the holding frame to facilitate maintenance operations, such as replacement of the main bearings.

[0022] After the new bearings are secured to the generator front plate, the front end assembly is reinstalled by moving the height adjustable platform back into the retaining frame and bolting to the drive end of the generator using the reverse order of the above process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed for purposes of illustration only and not as a definition of the limits of the present invention.

[0024] Figure 1 A wind turbine generator is shown; Figure 2 An exemplary embodiment of the generator loading and unloading equipment of the present invention is shown; Figure 3-5 shows the various stages in the maintenance process according to the present invention; Figure 6 The front end assembly is shown on a platform after being moved from under the generator; Figure 7 An exemplary embodiment of a height-adjustable platform tool of the generator handling equipment of the present invention is shown.

[0025] In the drawings, like reference numerals refer to like objects throughout. Objects in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0026] Figure 1 A portion of a wind turbine generator 2 of the type that can be handled using the generator handling apparatus 1 of the present invention is shown. The figure shows the housing 210 of the outer rotor 21, or field winding (which carries the arrangement of magnets), and the stator frame 220 of the inner stator 22, or armature (which carries the arrangement of coils). For clarity, the actual field winding and armature are not shown. The outer rotor is rotated by the wind turbine's aerodynamic rotor; that is, the wind turbine hub is directly connected to the drive end of the generator 2. The generator 2 can have an outer diameter of approximately 8 m and, when equipped with the field winding and armature, can weigh in the order of several hundred metric tons.

[0027] At the drive end, the main bearing 25 of generator 2 ensures smooth rotation of the field winding around the fixed armature. The drive end of generator 2 is enclosed by a front cover 24, and an anti-ovalization ring 26 is mounted to prevent deformation of rotor 21, which would otherwise lose its desired circular shape due to its own weight. The bearing 25, front cover 24, and anti-ovalization ring 26 at the drive end 2DE of the generator are collectively referred to below as the "front end assembly" 24, 25, 26.

[0028] At some point in time during the life of a wind turbine, the bearings 25 may require maintenance. In order to avoid loss of revenue during downtime, it is desirable to minimize the duration of any bearing maintenance or replacement procedure.

[0029] In order to perform a replacement or repair process on such a wind turbine generator main bearing, the generator 2 is removed from the wind turbine nacelle, as explained above. For example, in the case of an offshore wind turbine, the bearing replacement or repair process can be performed on the deck of a jack-up vessel after the generator has been transferred from the nacelle to the deck.

[0030] Figure 2 An exemplary embodiment of a generator handling apparatus 1 of the present invention is shown, which allows the main bearings to be removed and replaced without having to dismantle the entire generator 2. The handling apparatus 1 comprises three main parts: a lower part 11, which facilitates access to the front end components 24, 25 of the generator; a middle part 12, which is used to support the rotor 21; and an upper part 13, which facilitates handling of the stator 22.

[0031] In this exemplary embodiment, the lower portion 11 has four support structures 112 that support the middle portion 12, i.e., the middle portion 12 can be assembled on the lower portion 11 in a preliminary step. These four support structures 112 of the lower portion are designed to allow the front end assemblies 24, 25 of the generator to be moved into and out of the space between them. Here, the lower portion 11 includes a set of tracks or rails 15 to allow the movable platform 14 to be moved into and out of the space between these four support structures 112.

[0032] The middle section 12 also includes four support structures 122 or columns that rest on corresponding columns 112 of the lower section 11. In this embodiment, the columns 122 of the middle section 12 are used to support the framework 130 of the upper section 13. These four support structures 122 also carry clamps 120 that can be actuated to clamp the rotor housing 210.

[0033] The upper portion 13 includes a suspension assembly 13 adapted to be secured to a lifting bracket 23 of the stator 22, thereby allowing the stator 22 to be suspended from the upper portion 13. The suspension assembly 13 can be rotated using a rotation drive unit 131 configured to rotate the suspension assembly 13 and the suspended stator 22 a desired amount, for example, 180°.

[0034] Figure 3-5 The various stages in a maintenance process according to the invention are shown.

[0035] exist Figure 3 In the figure, generator 2 is being lowered into position between the support structures 112, 122 of the middle section 12 and the lower section 11. The platform 14 is raised to receive the generator drive end. To this end, the platform assembly 14 is equipped with a suitable number of hydraulic jacks 141 that can be actuated to extend in a vertical direction. After the generator 2 is lowered into position, the lower edge of the rotor housing 210 rests on the clamp 120, and the generator drive end rests on the raised platform 140, so that the platform assembly 14 substantially supports the weight of the stator.

[0036] exist Figure 4 In the embodiment, the upper part 13 is placed onto the support structure 122 of the middle part 12 and the lifting bracket 23 of the stator 22 is fixed to the suspension assembly 13 .

[0037] exist Figure 5During the transfer process, the four jacks 121 of the middle section 12 are actuated, extending them upward until the weight of the suspended stator 22 is transferred from the platform 140 to the stator suspension assembly 131. Since both the upper section 13 and the middle section 12 are elastic structures, the load distribution needs to be monitored during this load transfer process. This can be achieved by monitoring the pressure using appropriate pressure sensors deployed in the hydraulic circuits of the jacks 121 and 141. After this stage is complete, the weight of the stator 22 is borne solely by the upper section 13, and the platform 140 can be lowered. The platform assembly can then be removed to prepare for the next stage, in which the air gap between the armature and the field winding is measured. This air gap can be measured at multiple points, for example, at equally spaced intervals around its circumference. The rotation drive unit 131 is then actuated to rotate the stator an appropriate amount, for example, 180°, and the air gap is measured again. Finally, the rotation drive 131 is actuated to rotate the stator back to its initial position. Subsequently, in a process that will be known to the skilled person, air gap brackets are placed around the non-drive end 2NDE and the drive end 2DE of the generator 2 to maintain the air gap and make any necessary corrections to the air gap.

[0038] The front end assemblies 24, 25, 26 can now be separated from the drive end 2DE of the generator 2. After removing most of the fasteners from the front plate end assembly, the platform 14 is moved back under the generator 2 and raised to receive the front end assemblies 24, 25. The remaining set of external fasteners are removed to complete the front end assembly separation step.

[0039] The platform 14 is then lowered again, now carrying the separated front end components 24 , 25 , 26 .

[0040] Figure 6 The front end components 24 , 25 are shown on the platform 14 after being moved from under the generator 2 .

[0041] The defective main bearing 25 is now removed, and a new main bearing 25 is attached to the front plate 24. The platform 14, along with the refurbished front end assemblies 24, 25, is then moved back underneath the generator. After the platform 14 is raised, the external fasteners securing the front end assemblies 24, 25 to the generator 2 are replaced. The platform 14 is lowered and removed. The technician then tightens the remaining fasteners to complete the front end reattachment procedure.

[0042] The air gap is then checked again by removing the air gap bracket and measuring all around, actuating the rotary drive 131 to rotate the stator 22 180°, measuring the air gap again, and actuating the rotary drive to rotate the stator 22 back 180°.

[0043] The platform 14 is again raised to the front end 2DE of the generator 2 and the hydraulic jacks 121 are actuated to slowly lower the upper part 13 until the weight of the stator 22 is transferred from the suspension assembly 13 to the platform 14. Again, the load distribution is carefully monitored during this process.

[0044] In a final stage, following the reverse order of the above steps, the upper and middle parts 13, 12 of the handling apparatus 1 are lifted off the lower part 11, making the refurbished generator 2 accessible for a subsequent reinstallation process.

[0045] Figure 7 An exemplary embodiment of a height adjustable platform tool 14 is shown. The platform bed 142 carries the platform 140 and is slidable along the rails 15 of the handling apparatus 1. The platform 140 itself can be described as being substantially circular with gaps between the radially extending arms. These gaps facilitate access to the platform for use above. Figure 5 The platform 140 is raised or lowered relative to the platform bed 142 as required by an arrangement of hydraulic jacks 141.

[0046] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0047] For the sake of clarity, it is to be understood that the use of "a", "an" or "an" throughout this application does not exclude a plurality, and "comprising" does not exclude other steps or elements.

Claims

1. A loading and unloading device (1) for a wind turbine generator (2), comprising: - a holding frame (11, 12) suitable for receiving and holding the generator (2); - a height-adjustable platform (14) adapted to engage with the drive end (2DE) of the generator (2); - a stator suspension assembly (13) adapted to be mounted on said retaining frames (11, 12) and connected to the non-driven end (2NDE) of the stator (22); and - Rotation means (131) adapted to rotate the stator suspension assembly (13) about the axis of rotation (2A) of the generator (2).

2. The handling device according to the preceding claim, wherein: The retaining frames (11, 12) are suitable for bearing the weight of the rotor (21).

3. A handling device according to any one of the preceding claims, wherein: The height-adjustable platform (14) is adapted to bear the weight of the stator (22) and front-end components (24, 25, 26) of the generator (2).

4. A handling device according to any one of the preceding claims, wherein: The holding frame (11, 12) is adapted to accommodate the height-adjustable platform (14) below the generator (2).

5. The handling device according to any of the preceding claims, comprising an arrangement of guide rails (15) extending to the sides of the holding frames (11, 12), and wherein: The height-adjustable platform (14) is adapted to move along the guide rail (15).

6. Handling arrangement according to any of the preceding claims, comprising vertical displacement means (121) adapted to raise and lower the stator suspension assembly (13).

7. Handling equipment according to any one of the preceding claims, comprising means (141) for raising and lowering the height-adjustable platform (14).

8. A handling device according to any one of the preceding claims, wherein: The rotating device (131) is suitable for rotating the stator suspension assembly (13) by 180°.

9. A method for performing a generator maintenance procedure using the generator handling apparatus (1) according to any one of claims 1 to 8, the method comprising: - arranging the generator (2) in the loading and unloading equipment (1); - Monitoring of generator air gap; - removing the front end assembly (24, 25, 26) from the drive end (2DE) of the generator (2); - reinstalling the front end assembly (24, 25, 26) after the maintenance task is completed; and - Restore the generator air gap.

10. The method according to the preceding claim, wherein The step of arranging the generator (2) in the loading and unloading equipment (1) comprises: - arranging a height-adjustable platform (14) within the holding frame (11, 12) to receive the drive end (2DE) of the stator (22); - lowering the generator (2) into the holding frame (11, 12) until its drive end (2DE) rests on the height-adjustable platform (14); and - connecting a stator suspension assembly (13) to the non-drive end (2NDE) of the stator (22); and - Transferring the weight of the stator (22) to the stator suspension assembly (13).

11. The method according to the preceding claim, wherein The steps of monitoring the generator air gap include: - measuring said air gap; - actuating the rotating device (131) to rotate the suspended stator (22) a fraction of a revolution; - measuring said air gap; and - actuating the rotating device (131) so as to cause the suspended stator (22) to rotate a portion of the revolution.

12. The method according to the preceding claim, wherein The steps of removing the front end components (24, 25, 26) include: - decoupling the front end assembly (24, 25, 26) from the drive end of the generator (2); and - Moving the height-adjustable platform (14) out of the holding frames (11, 12) to facilitate maintenance operations.

13. The method according to the preceding claim, wherein The maintenance operation includes the step of replacing the main bearing (25).

14. The method according to the preceding claim, wherein The steps of reinstalling the front end assembly (24, 25, 26) include: - moving the height-adjustable platform (14) back into the holding frame (11, 12); and - Reattaching the front end assembly (24, 25, 26) to the drive end (2DE) of the generator (2).

Images