Generator stiffener ring

Abstract

The present invention relates to an electric machine comprising a rotor (13), a stator (12), and a radial air gap (39) between the rotor (13) and the stator (12), wherein one of the rotor and the stator comprises an end plate driven on one side of the electric machine, a central support (32) radially surrounding the other of the rotor (13) and the stator (12), and a reinforcing ring (33) on the opposite side of the electric machine. The reinforcing ring comprises an outer ring (34) connected to the central support (32) and an inner ring (35) connected to the outer ring (34). The outer ring (34) comprises a plurality of outer segments (44) that are removablely mounted. The present invention also relates to a method for repairing parts of a wind turbine and an electric machine.

Description

Technology Field

[0001] The present invention relates to an electric machine, and more specifically to a generator for a wind turbine and a wind turbine comprising such a generator. The present invention also relates to a method for accessing active components of an electric machine, more specifically a wind turbine generator. Background Technology

[0002] Electric machines, such as motors and generators, generally include rotor structures and stator structures. Large generators can be, for example, permanent magnet excited generators (PMGs).

[0003] Such a generator can be used, for example, in a wind turbine. A wind turbine generally comprises a rotor hub and a rotor having a plurality of blades. The rotor is set to rotate under the influence of wind on the blades. The rotation of the rotor shaft is driven either directly ("direct drive") the generator rotor or using a gearbox. Such a direct drive wind turbine generator may have, for example, a diameter of 6 to 10 meters (236 to 328 inches) and a length of, for example, 2 to 3 meters (79 to 118 inches), and may be rotated at a low speed in the range of, for example, 2 to 20 rpm (revolutions per minute). Alternatively, the permanent magnet generator may also be coupled to a gearbox that increases the generator's rotational speed, for example, to 50 to 500 rpm or more.

[0004] An electric machine includes a rotor that rotates relative to a stator. The rotor may be an internal structure and the stator may be an external structure. Thus, in this case, the stator surrounds the rotor. Alternatively, it may have the opposite configuration, namely, the rotor surrounds the stator radially.

[0005] In the case of permanent magnet excitation generators (PMGs), permanent magnets (PMs) are typically contained in the rotor (whereas the permanent magnets may alternatively be arranged in the stator structure), while winding elements (e.g., coils) are typically contained in the stator (whereas the winding elements may alternatively be placed in the rotor structure). Permanent magnet generators are generally considered reliable and require less maintenance than other generator types. This is a key reason why permanent magnet generators are employed in offshore wind turbines, particularly direct-drive offshore wind turbines.

[0006] Multiple permanent magnets may be provided in a permanent magnet module, which may be attached to the rotor as a single item. The permanent magnet module may be limited to a unit having the plurality of permanent magnets so that the plurality of magnets can be mounted and detached together. Such a module may have a module base having a shape suitable for accommodating or mounting the plurality of permanent magnets that can be fixed to a base. The base may be configured to be fixed to a rotor structure, such as a rotor rim, in such a manner that the plurality of magnets are fixed together to the rotor rim through the module base. Using a permanent magnet module may facilitate the manufacture of the rotor. Similarly, stator coils may be grouped together into a coil module. The coil module may be fixed to a generator structure, such as a stator rim.

[0007] In larger electric machines, such as direct-drive wind turbines, one side of the electric machine may be closed by an end plate. Another side of the electric machine may be partially closed by a reinforcing flange. Such a reinforcing flange extends partially inwardly in a radial direction but is generally not supported. The reinforcing flange may be divided so that segments of the flange can be temporarily removed to access active parts (permanent magnets and / or coils) for maintenance or repair. Document EP2376776B1 discloses a generator for a wind energy facility having a rotor having permanent magnets. A generator is formed without a rotor or stator on its outer perimeter as a completely enclosed support housing, and the stacks of the stator are connected to each other by adhesive bonding and / or welding. Document GB1110420A discloses an amortisseur rotor comprising amortisseur bars that terminate at short-circuit end rings, which are reinforced by steel rings having flanges that protrude from each end of the rotor and are each oriented inward, so that the center of gravity of the protruding assembly is substantially the same as the center of gravity of the unreinforced assembly. Document EP2169220A2 discloses a disc brake device provided for a wind turbine generator comprising a support ring for a rotor winding that is surrounded by a stator winding inside the generator case and a rotor shaft that supports a rotor wheel. means of solving the problem

[0008] In one embodiment of the present invention, an electric machine is provided. The electric machine comprises a rotor, a stator, and a radial air gap between the rotor and the stator. One of the rotor and the stator comprises an end plate on one side of the generator and a central support surrounding the other of the rotor and the stator, and further comprises a reinforcing flange on the opposite side of the generator. The reinforcing flange comprises an outer ring connected to the central support and an inner ring connected to the outer ring. The outer ring comprises a plurality of outer annular segments that are removablely mounted.

[0009] According to the electric machine of the present embodiment, maintenance and repair of the rotor and stator can be facilitated. To provide access to the rotor and / or stator, a removable outer segment may be removed. The inner ring may provide sufficient rigidity so that the rotor is not deformed during such operation and the air gap between the stator and the rotor is not damaged. Additionally, the weight of the structure may be optimized due to a solution that includes, for example, avoiding an increase in the thickness and width of a reinforcing ring to increase rigidity.

[0010] Throughout the invention, "removably mounted" will mean that the components or segments to be removablely mounted are mounted in a manner such that they can be detached or removed without damaging said components or segments or surrounding structures. said components or segments may be mounted or attached with suitable fasteners, such as bolts or screws, and in other cases, said fasteners may be removed to allow the components or segments to be disassembled or removed.

[0011] In a further embodiment, a method for repairing a part of an electric machine having a rotor, a stator, and a radial air gap between said rotor and said stator is provided. The method comprises the steps of removing a segment of a reinforcing ring on the side of said electric machine to create an opening in the reinforcing ring, and accessing said rotor and / or said stator through the opening of said reinforcing ring, wherein said reinforcing ring is not supported at the radially inner end of said reinforcing ring. said reinforcing ring comprises an outer ring and an inner ring, and the step of removing a segment of said reinforcing ring comprises removing a segment of said outer ring without disassembling said inner ring.

[0012] According to the method of the present embodiment, access to the generator rotor and / or stator may be provided to perform repairs. In examples, active parts of the rotor and / or stator may be removed and replaced.

[0013] In another embodiment, a wind turbine is provided comprising a wind turbine rotor having a plurality of blades, a generator rotor operably connected to the wind turbine rotor, and a generator stator radially arranged within the generator rotor. The generator rotor comprises a front radial support rotatably mounted on a main frame, a rotor rim, and a rear reinforcing ring of the generator rotor. The reinforcing ring comprises an outer ring and an inner ring, and the outer ring comprises a plurality of outer ring segments that are removablely mounted. Brief explanation of the drawing

[0014] Figure 1 schematically illustrates a perspective view of an example of a wind turbine. Figure 2 illustrates an example of a direct-drive wind turbine. Figure 3 schematically illustrates an example of a generator for a direct-drive wind turbine. Figure 4 schematically illustrates an example of an axial drawing of a generator. Figure 5 schematically illustrates the details of the example generator of Figure 4. FIGS. 6 and 7 schematically illustrate examples of repair methods for the active parts of the generator of FIG. 4. FIG. 8 schematically illustrates an additional example of an electric machine according to the present invention. Specific details for implementing the invention

[0015] Now, one or more examples will be described in detail with reference to the embodiments of the invention illustrated in the drawings. Each example is provided in a manner that illustrates the invention, not with the intent to limit the invention. In practice, it will be obvious to those skilled in the art that various modifications and variations may be made to the invention without departing from the scope or spirit of the invention. For example, features exemplified or described as part of one embodiment may be used with another embodiment or may give rise to another embodiment. Accordingly, the invention is intended to include such modifications and variations within the scope of the appended claims and their equivalents.

[0016] FIG. 1 illustrates a perspective view of an example of a wind turbine (1). As illustrated, the wind turbine (1) comprises a tower (2) extending from a support surface (3), an engine room (4) mounted on the tower (2), and a rotor (5) coupled to the engine room (4). The rotor (5) comprises a rotatable hub (6) and at least one rotor blade (7) connected to the hub (6) and extending outwardly therefrom. For example, in the illustrated example, the rotor (5) comprises three rotor blades (7). However, in an alternative embodiment, the rotor (5) may comprise more than or fewer than three rotor blades (7). Each rotor blade (7) is spaced apart from the hub (6) to facilitate rotation of the rotor (5), thereby enabling kinetic energy to be converted from wind power into usable mechanical energy and subsequently into electrical energy. For example, the hub (6) may be located within the engine room (4) or rotatably coupled to a generator (10) (Fig. 2) that forms part of the engine room so that electrical energy can be generated. The rotation of the rotor may be transmitted directly, for example, from a direct-drive wind turbine or through the use of a gearbox for the generator.

[0017] FIG. 2 illustrates a simplified internal view of an example of an engine room (4) of a direct-drive wind turbine (1). As illustrated, the generator (10) may be placed inside the engine room (4) or between the engine room (4) and the rotor (5). Generally, the generator (10) may be coupled to the rotor (5) of the wind turbine (1) to generate power from the rotational energy generated by the rotor (5). For example, the rotor (5) of the wind turbine may include a hub (6) coupled to the rotor (9) of the generator (10) for rotation. Thus, the rotation of the hub (6) can drive the rotor (12) of the generator (10).

[0018] In FIG. 2, the wind turbine rotor (5) may be rotatably mounted on a support frame (9) via a rotor bearing (8) in a coupling area or on the front side. The generator (10) may include a rotor (12) and a stator (13). The stator may be rigidly mounted on the support frame (9). The rotor may be rotatably mounted on the stator via a generator bearing (14) so ​​that the rotor may rotate about an axis relative to the stator.

[0019] The generator (10) may be electrically coupled to a converter. The wind turbine converter may adjust the output power of the generator to meet the requirements of the power grid. In some examples, the converter may be placed inside the engine room (4); however, in other examples, it may be placed at a different location on the wind turbine.

[0020] It should be understood that the rotor (5) of the wind turbine and the generator (10) may be supported by a support frame (9) or a bedplate located on the upper part of the wind turbine tower (2).

[0021] The engine room (4) is rotatably coupled to the tower (2) via a yaw system (20). The yaw system includes a yaw bearing (not observed in FIG. 2) having two bearing elements configured to rotate relative to each other. The tower (2) is coupled to the first bearing element and the engine room (4), and, for example, the bedplate or support frame (9) is coupled to the second bearing element.

[0022] FIG. 3 schematically illustrates an example of a generator for a wind turbine. In one embodiment of the present invention, a wind turbine is provided comprising a wind turbine rotor (5) having a plurality of blades (7) (see FIG. 1 and FIG. 2). The wind turbine also comprises a generator rotor (13) operably connected to the wind turbine rotor (5) and a generator stator (12) radially arranged within the generator rotor (13). The generator rotor (13) comprises a forward-positioned radial support (31) rotatably mounted on a main frame (9), a rotor rim (32), and a rear-positioned reinforcing ring (33) of the generator rotor. The reinforcing ring (33) comprises an outer ring (34) and an inner ring (35), wherein the outer ring (34) comprises a plurality of outer ring segments (44) that are removablely mounted (e.g., see FIG. 4).

[0023] In the example of FIG. 3, the inner ring (35) is not supported from the inside. In this example, the rotor radially surrounding the stator is mounted cantilevered and supported only on one side of the generator. In the example of FIG. 3, the generator rotor can be driven directly by the wind turbine rotor (5), that is, there is no gearbox arranged between the rotor (shaft) and the generator rotor. In the example of FIG. 3, the rotor shaft (36) can be directly coupled to the hub (6) of the wind turbine, or the rotor shaft (36) can be an extension of the hub of the wind turbine.

[0024] In examples (such as those shown in FIG. 4), the outer ring may comprise 10 to 50 segments, particularly 20 to 40 segments. The optimal number of segments may be determined by the diameter of the generator rotor. The size of the segments may be selected so that a single segment can be removed to allow access to the rotor or stator of the generator. In particular, the segments may be shaped and sized so that active components can be removed through the opening created by the removal of the segment. The active components may be a single coil, a single permanent magnet, or a coil module or a permanent magnet module. In examples, different outer segments may have different sizes. However, to optimize manufacturing and logistics, all outer segments may have the same size and configuration.

[0025] In examples, the wind turbine may include a seal between outer ring segments that are removablely mounted.

[0026] Still relating to FIGS. 3 and 4, in a further embodiment, the present invention provides an electric machine (10) comprising a rotor (13), a stator (12), and a radial air gap (39) between the rotor (13) and the stator (12). According to the present embodiment, one of the rotor and the stator comprises an end plate (31) on one side of the generator (10), a central support (32), and a reinforcing flange (33) on the opposite side of the generator (10). The central support (32) is radially positioned outside of the other of the rotor and the stator or radially surrounds the other. The reinforcing ring or reinforcing flange (33) comprises an outer ring ("annular flange") (34) connected to the central support (32), and an inner ring ("inner annular flange") (35) connected to the outer ring (34). The outer ring (34) includes a plurality of outer annular segments (44) that are removablely mounted.

[0027] In the illustrated example, the rotor may radially surround the stator, and the rotor may form a protruding structure. In another example, the stator may radially surround the rotor. And, in such a case, the stator may be mounted cantilevered and includes a ring-shaped end plate on one side and a reinforcing ring on the other side.

[0028] The above end plate may substantially be ring-shaped or annular.

[0029] In the example illustrated, the electric machine is a generator, more specifically, a generator for a wind turbine. In this example, the rotor is driven by a wind turbine rotor. In another example, the electric machine may be a motor.

[0030] The ring-shaped end plate (31) can close the generator at one side, and in the example of FIG. 3, at the front side of the generator, i.e., the side of the generator where the rotor hub of the upstream wind turbine is mounted. The end plate (31) can be attached to the flange of the rotor shaft with a suitable fastener (37). The rotor shaft (36) is supported on the main frame (9). In the example of FIG. 3, the rotor shaft (36) can be rotatably mounted on the main frame (9) with a front bearing (8) and a rear bearing (14). In the example of FIG. 3, the front bearing (8) and the rear bearing (14) can be a single tapered roller bearing.

[0031] The stator may be mounted on the main frame (9). An internal support (22) may be formed integrally with the main frame (9). The internal support (22) extends outwardly in a radial direction. A stator rim may be mounted on the internal support (22). In such a specific example, the stator rim forms part of a central stator structure. The stator rim may support stator coils (26). A set of stator coils may be grouped into coil modules.

[0032] The end plate (31) and the central support structure (32) can be formed integrally as shown in the drawing. The central support structure can form an outer rotor rim that mounts permanent magnets (37). A set of permanent magnets (37) can be grouped together into a permanent magnet module.

[0033] In the radial inward direction of the reinforcing ring (33), elements of the cooling system may be arranged with cooling air ducts that supply cooling air toward the generator and cool the active components and thereby extract the air after it has been heated. Additional space is taken up by the electrical cable connected to the generator. Suitable seals may be provided to control the atmosphere inside the generator and to separate it from the rest of the engine room.

[0034] The generator (10) may additionally include a suitable cover for protecting and blocking the generator (not shown in FIG. 3).

[0035] FIG. 4 shows a rear view of an example of the generator (10). The inner support (22) and the stator rim can be seen in FIG. 4. The portion of the stator central structure having the rim and the active parts of the generator are closed by the reinforcing ring, which includes the outer ring or outer flange (34) and the inner ring or inner flange (35).

[0036] As can be seen in FIGS. 4 and 5, the removablely mounted outer annular segments (44, 44') may be mounted to the central support (32) and the inner annular flange (35). The removablely mounted annular segments (44, 44') may be mounted with removable fasteners such as bolts or screws. The central support or rotor rim (32) may include suitable fastener holes.

[0037] The inner ring (35) comprises a plurality of inner annular segments (49, 49') and connecting plates (45), wherein the connecting plates (45) are connected to the inner annular segments (49, 49'). The inner ring may be composed of a plurality of segments. By using the segment buildup of the inner annular flange, ergonomics, ease of manufacturing, and transport can be improved.

[0038] The individual segments (49, 49') may have recessed areas at both ends. The connecting plates (45) may be arranged on such recessed areas and may be secured to adjacent inner annular segments (49, 49') through bolts or similar fasteners.

[0039] In the examples of FIGS. 3 and 4, the inner ring is not supported at its radially inner end. That is, on the non-driving side of the generator rotor, the reinforcing member is not supported by bearings or the like. As can be seen, the end plate on the other side of the generator is supported at its radially inner end. In these examples, the main function of the reinforcing member is to provide rigidity, but also to allow access for repair and protect the interior of the generator from the external environment.

[0040] As can be seen in FIG. 6, one of the outer annular segments (44') is removed, and the outer annular segments (44, 44') may be positioned at the top of the recesses or recess regions (47) at the outer end of the inner annular segments (49). Although not shown in FIG. 4 through 6, the spaces between the outer annular segments (44, 44') may be sealed to maintain a protected environment inside the generator. Silicone may be used to seal such spaces.

[0041] In some examples, the outer annular segments (44, 44') may be configured to be equipped with a tool for removing the outer annular segments. Similarly, the inner ring may be configured to be equipped with a tool for removing the outer annular segments.

[0042] A robot or other tool may be used to separate the outer annular segment from the support (32) and the inner annular flange (35). To do this, the outer annular segments and / or the inner ring or flange (35) may be provided with suitable mounting holes (49) or fittings so that a robot or other tool can be attached. Once attached, the robot or other tool may remove fasteners, such as screws or bolts, to release the outer annular segment and to disassemble the outer ring.

[0043] Specifically, with reference to FIGS. 6 and 7, the present invention further provides a method (100) for repairing a part of an electric machine (10) having a rotor (13), a stator (12), and a radial air gap (39) between the rotor (13) and the stator. The method includes the step of removing a segment (44') of a reinforcing ring (33) located on the side of the generator (10) to create an opening in the reinforcing ring (33). The reinforcing ring is not supported at the radially inner end of the reinforcing ring.

[0044] The above method includes the step of accessing the rotor (13) and / or the stator (12) through an opening in the reinforcing ring (33). The reinforcing ring (33) comprises an outer ring (34) and an inner ring (35), and the step of removing a segment (44') of the reinforcing ring (33) includes removing a segment of the outer ring (34) without disassembling the inner ring (35). Thus, an opening is created in the reinforcing ring, which is at least partially defined by the inner ring. In the present example, the opening is defined by the rim (32) or central support, a part of the inner ring, and adjacent outer annular segments.

[0045] In this example, the electric machine (10) is a generator.

[0046] In some examples, one or more active parts of the generator (10) may be removed through an opening in the reinforcing ring (33). Stator coils or coil modules or permanent magnets or permanent magnet modules may be removed through the opening. Such active parts may be replaced with new active parts.

[0047] In some examples, more than one segment of the outer ring may be removed without disassembling the inner ring. In some examples, multiple segments may be removed to access other sections of the generator simultaneously. In order not to locally impair rigidity, particularly non-adjacent segments may be removed simultaneously.

[0048] In some examples, the step of removing the segments of the outer ring may include mounting a tool on the reinforcing ring and using the tool to separate the segments of the outer ring from other segments of the outer ring. The tool may be a robot or other automated device that can be used to disassemble the segments, particularly to remove bolts or other fasteners of the segments. In some examples, mounting the tool may include mounting the tool at least partially on the inner ring and / or the segments of the outer ring.

[0049] An example of a method (100) for repairing a generator is illustrated in the block diagram of FIG. 7. In block 110, a tool can be attached to the reinforcing ring of the generator. In block 120, a segment of the outer ring of the reinforcing ring can be removed using the tool, and in block 130, the inner ring of the reinforcing ring is now disassembled, that is, kept intact. Thus, the inner ring can provide sufficient rigidity and strength so that the generator rotor is not deformed and the air gap is not damaged.

[0050] After one or more segments of the outer ring are removed, access to the interior of the generator is provided in block 140. In examples, a worker can reach the interior of the generator and inspect the parts of the generator, particularly the active parts. In examples, minor repairs can be performed without the need to remove the active parts.

[0051] In other examples, in block 150, one or more active parts may be removed through an opening created by the removal of the outer ring segment. Next, in block 160, the removed active parts may be replaced with new parts. The same opening may be used to introduce the new parts and to mount them to the stator or rotor. Finally, in block 170, the segment of the outer ring may be reattached. The segment may be assembled with the inner ring and the rotor rim. The spaces between the segment and adjacent segments may be sealed. Once repair or inspection is completed, the wind turbine may resume normal operation.

[0052] In examples, the reinforcing ring may cover 20% to 60% of the generator rotor diameter. That is, 40% to 80% of the inner diameter of the generator is not covered by the reinforcing ring.

[0053] In the examples, the outer segments of the reinforcing ring may have a width (radially) of 50% to 150% of the radial width of the inner segments. Specifically, the width may be 75% to 125% of the width of the inner segments. In the examples of FIGS. 4 to 6, the outer segments have a width approximately equal to that of the inner segments in the radial direction, but the outer segments partially overlap with the inner segments.

[0054] FIG. 8 illustrates an additional example of an electric machine. In this example, the electric machine is a generator. The generator comprises a rotor (13) and a stator (12). The stator (13) radially surrounds the rotor (12) and forms a protruding structure. The protruding structure is supported on one side of the rotor (downstream of the generator rotor (13)) and is not supported on the other side (upstream of the generator rotor (13)).

[0055] The rotor (12) is operably connected to a wind turbine rotor (not shown, arranged on the left, upstream side of FIG. 8). The rotor (12) is supported on a stator (13) through one or more bearings (14). The rotor (12) may be equipped with a permanent magnet (37) on the rim of the rotor (12). The stator may include a plurality of electric coils (26). A radial air gap (39) is arranged between the rotor and the stator.

[0056] On the unsupported side of the stator (12), the reinforcing ring comprises an outer ring (34) and an inner ring (35). On the supported side of the stator (12), an end plate (22) closes the generator. The stator (12) further comprises a central support (24) for mounting coils.

[0057] For the rotor of FIG. 4, the outer ring (34) of the reinforcing ring comprises a plurality of removable outer segments. When access to the interior of the generator is required to inspect, repair, or replace active components of the generator, one or more of the segments of the outer ring may be removed. Thus, an opening is created in the reinforcing ring. The inner ring (35) may remain intact, define the boundaries of the opening, and provide the necessary rigidity to avoid deformation of the partially disassembled stator.

[0058] Although only a number of examples are disclosed herein, other alternatives, modifications, uses, and / or equivalents are possible. Also included are all possible combinations of the described examples. Accordingly, the scope of the invention should not be limited by specific examples but should be determined only by a fair interpretation of the following claims.

Claims

Claim 1 An electric machine (10) comprising a rotor (13), a stator (12), and a radial air gap (39) between the rotor (13) and the stator (12), wherein one of the rotor (13) and the stator (12) comprises an end plate (31) on one side of the electric machine and a central support (32) radially surrounding the rotor and the stator, and further comprising a reinforcing ring (33) on the opposite side of the electric machine, wherein the reinforcing ring (33) is not supported at the radial inner end of the reinforcing ring (33), wherein the reinforcing ring (33) comprises an outer ring (34) connected to the central support (32) and an inner ring (35) connected to the outer ring (34), and wherein the outer ring (34) comprises a plurality of outer annular segments (44) that are removablely mounted. Claim 2 In claim 1, the removablely mounted outer annular segments (44) are mounted on the central support (32) and the inner ring (35), an electric machine. Claim 3 An electric machine according to claim 1 or 2, wherein the inner ring (35) comprises a plurality of inner annular segments (49, 49') and connecting plates (45), and the connecting plates (45) are connected to the inner annular segments (49, 49'). Claim 4 An electric machine according to claim 1 or 2, wherein the outer annular segments (44) are configured to be equipped with a tool for removing the outer annular segments. Claim 5 An electric machine according to claim 1 or 2, wherein the inner ring (35) is configured to be equipped with a tool for removing the outer annular segments (44). Claim 6 An electric machine according to paragraph 1 or 2, wherein the electric machine is a generator. Claim 7 In paragraph 6, the above end plate (31) is connected to the rotor shaft (36), an electric machine. Claim 8 In claim 7, the rotor shaft (36) is an electric machine supported on a main frame (9). Claim 9 In claim 7, the rotor shaft (36) is supported by a front bearing (8) and a rear bearing (14), in an electric machine. Claim 10 An electric machine according to claim 6, wherein the stator (12) radially surrounds the rotor (13), and the end plate (22) of the stator (12) is arranged on the side of the rotor (13) on which the wind turbine rotor is arranged. Claim 11 A wind turbine comprising a generator in accordance with Paragraph 6, as a wind turbine. Claim 12 A method for repairing a part of an electric machine according to claim 1 or 2, comprising the steps of: removing a segment (44) of the reinforcing ring (33) on the side of the electric machine to create an opening in the reinforcing ring (33); and accessing at least one of the rotor (13) and the stator (12) through the opening of the reinforcing ring (33), wherein the step of removing the segment (44) of the reinforcing ring (33) includes removing the segment (44) of the outer ring (34) without disassembling the inner ring (35). Claim 13 A method according to claim 12, comprising removing one or more segments (44) of the outer ring (34) without disassembling the inner ring (35). Claim 14 A method according to claim 12, further comprising the step of removing one or more active parts (26; 37) of a generator through the opening of the reinforcing ring (33). Claim 15 A method according to claim 12, wherein removing the segment (44) of the outer ring (34) comprises mounting a tool on the reinforcing ring (33) and disassembling the segment (44) of the outer ring (34) with the tool.

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