Support structure for a generator of a wind turbine

Field of the invention

The invention relates to a support structure for a generator of a wind turbine and a generator of a wind turbine compris ing such support structure. Particularly, but not exclusive ly, the support structure may a be a segmented support struc ture.

Art background

Wind turbines typically include multiple blades for generat ing mechanical rotation energy. A generator within the wind turbine is configured to generate electrical power as the blades are driven to rotate by the wind. Wind turbines are therefore designed to efficiently translate wind energy into rotational motion, thereby providing the generator with suf ficient rotational energy for electrical power generation.

The generator of the wind turbine comprises a stator and a rotor.

The stator normally comprises a frame body longitudinally ex tending along a longitudinal axis and including a plurality of teeth protruding according to a radial direction from the stator yoke. In the stator a plurality of slots is also de fined, each slot being delimited circumferentially by two ad jacent teeth. Each slot houses a respective winding. Lamina tion sheets are attached one after another along the axial direction of the stator and form a lamination stack of the stator, where the coils for electrical power generation are provided. The rotor comprises a plurality of magnets. Upon rotation of the magnets, rotational energy is converted into electrical power.

There are designs, which have the rotor arranged radially outward with respect to the stator. In a different design the stator is arranged radially outward with respect to the ro tor.

The segmented lamination sheet stacks of the stator need to be placed at a specified distance to the magnets of the ro tor. To this end, a support structure is incorporated in the stator between the lamination sheet section of the stator and the rotor.

Such a support structure needs to provide versatile func tions, to prevent collision between the stator and rotor, in particular regarding the significant radial and tangential electromagnetic (EM) forces which are generated within the active generator. Further, it should prevent the occurrence of coinciding eigenfrequencies of the segmented assembly and electromagnetic excitation force frequencies. Furthermore, the support structure needs to withstand all generator load conditions in the long term, i.e. preferably during the whole lifetime of the generator, and should enable efficient cool ing by channelling of cooling air.

Support structures as part of a stator are known in the state of the art. The support structure may comprise a carrier ele ment. The carrier element is employed for coupling the sup port structure segment, and therefore the support structure as a whole, to the lamination sheet section of the stator.

The carrier elements in such support structures known from the state of the art are T-profile type carrier elements.

Such carrier elements have a base section, wherein at the centre of the base section a solid perpendicular element is placed. Alternatively, a net-plate, i.e. a plate which is welded and have cut-outs) may be used. Due to a limited surface area of the centre element, coupling of the support structure to the lamination sheet section of the stator may result in limited stability connections. Such connections may not be sufficient to meet the stability re quirements of modern wind turbines.

Further, conventional support structure may still be improved as far as radial stiffness is concerned. It may be desirable, for example, to provide the required level of radial stiff ness with less material or with a more simplified design.

Summary of the invention

It may be an object of the present invention to provide a support structure for a stator, in particular for use in a generator of a wind turbine, which fulfils the requirements regarding mechanical stability and which at the same time can be manufactured in a cost-efficient way.

This object may be solved by a support structure segment, a stator and a method for manufacturing the stator according to the subject matter of the independent claim.

One aspect of the invention relates to a support structure for a stator of a generator, in particular of a wind turbine, wherein the support structure extends along a longitudinal axis and comprises a plurality of carrier elements, each car rier element comprising a base section, a side section and a top section. The base section and the side section are ori ented relative to each other at an outer angle (f) in a range of 70° to 130°. The side section and the top section are ori ented relative to each other at an inner angle (Q) in a range of 70° to 130°. The base section is connected to the side section. The side section is connected to the top section.

The base section is spaced apart from the top section essen tially in a radial direction orthogonal to the longitudinal axis. The base section of at least one carrier element of the plurality of carrier elements is connected to the base sec tion of another one carrier element of the plurality of car rier elements. A plurality of circumferential connecting ele ments circumferentially protruding from the base section of one carrier element is connected to another plurality of con necting elements circumferentially protruding from the base section of another carrier element 200 in order to provide a connection between the one and the other carrier element, a plurality of cooling pockets being formed between the con necting elements for cooling air to pass.

The present invention provides high radial stiffness. At the same time less pre-machining of support elements is required, with respect to the prior art. Further, less circumferential ribs and less welding are also required, thus reducing costs for material and labor. Potential better cooling is achieved as less tangential ribs reduces the pressure drop. The carri er elements do not only allow for a stable connection of the support structure segment to the lamination structure but in addition allow for establishing a connection in the circum ferential direction to other circumferentially adjacent car rier elements.

The base section, the side section and the top section of the carrier element describe for example a Z-type profile. More preferably, in an exemplary embodiment as described further below, the base section, the side section, the top section, a further side section, and a further base section of the car rier element describe an W-type profile (omega type profile).

Thereby, the carrier element or a plurality of carrier ele ments form the support structure segment. One or a plurality of lamination sheets of the stator can be coupled to the sup port structure segment, and therefore the support structure as a whole forms a lamination sheet section of the stator.

The support structure segment is preferably used with a gen erator design, in which the stator is arranged radially out- ward with respect to the rotor but is not restricted thereto. The support structure segment may also be used in a generator design which has the rotor arranged radially outward with re spect to the stator.

According to embodiments of the present invention, the outer angle f may be in a range of approximately 85° to approxi mately 120° and more in particular in a range of approximate ly 85° to approximately 105°. Further, the inner angle Q may be in a range of approximately 85° to approximately 120° and more in particular in a range of approximately 85° to approx imately 105°. The inner angle Q and the outer angle f may take approximately the same value.

In particular, the base section essentially extends in the circumferential direction connecting directly to the side section. The side section essentially extends in radial di rection. An end of the side section is therefore oriented es sentially in radial direction. In this context, the term "es sentially extends in radial direction" means that the side section extends in radial direction within the boundaries ex pressed by the outer angle.

In particular, the side section connects directly to the top section. The top section essentially extends in circumferen tial direction. The ends of the top section are therefore oriented essentially in circumferential direction. In this context, the term "essentially extends in circumferential di rection" means that the top section extends in circumferen tial direction within the boundaries expressed by the inner angle. In particular, the base section, the side section and the top section form a Z-type profile when viewed along the axial direction.

In particular, the support structure comprises one or a plu rality of the above described carrier elements. The carrier elements are arranged spaced apart from each other along the circumferential direction and extend generally along the axi- al direction. Specifically, a carrier element comprises the above described top section, base section and side section. The top section is arranged within a top plane, the base sec tion is arranged within a base plane and the side section is arranged within the side plane. The top section, the base section and the side section extends parallel with respect to each other along a longitudinal direction, for example along the axial direction. The top plane and the side plane (i.e. their normals) have the inner angle between each other of ap proximately 70° to approximately 130°, in particular 90°. The base plane and the side plane (i.e. their normals) have an outer angle between each other of approximately 70° to ap proximately 130°, in particular 90°.

According to embodiments of the present invention, each cool ing pocket extends along the longitudinal axis between two connections, each connection being performed by joining two connecting elements of two respective circumferentially adja cent carrier elements.

According to an embodiment, the carrier element is a mono- lithically formed carrier element, in particular a monolithi- cally formed metal carrier element.

The manufacture of a monolithically formed carrier element is cost efficient and allows for easy adaptation of the size and measures of the carrier elements to the size and measures of the generator which it is provided for. Therefore, scaling of the support structure, i.e. adjusting the support structure to generators of different sizes and measure is efficiently possible.

According to an embodiment, the support structure comprises at least two carrier elements.

In particular, the support structure segment comprises at least 3, 4, 5, 6 or 7 or even more carrier elements. By providing a plurality of carrier elements a stable cou pling of the support structure to the lamination sheet sec tion may be achieved. Further, the individual carrier ele ments of the plurality of separate carrier elements may be spaced apart and openings may be formed between two adjacent carrier elements which allow for a flow of air in a radial direction.

The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodi ment but to which the invention is not limited.

Brief Description of the Drawings

Figure 1 shows a schematic section of a wind turbine includ ing an electrical generator with a stator according to the present invention.

Figure 2 shows an exploded view of an electrical generator with a stator according to the present invention.

Figure 3 shows an axonometric view of a segment of the stator of Fig. 2.

Figure 4 shows a first component of the segment of Fig. 3.

Figure 5 shows a second component of the segment of Fig. 3.

Figure 6 shows a support structure for the segment of figure 3, in a first axonometric view from the bottom.

Figure 7 shows a support structure for the segment of figure 3, in a second axonometric view from the top. Figure 8 shows a carrier element of the support structure ac cording to an embodiment of the invention, in a per spective view.

Detailed Description

The illustrations in the drawings are schematic. It is noted that in different figures, similar or identical elements are provided with the same reference signs.

Figure 1 shows a wind turbine 1 according to the invention. The wind turbine 1 comprises a tower 2, which is mounted on a non-depicted foundation. A nacelle 3 is arranged on top of the tower 2. The wind turbine 1 further comprises at least a wind rotor 5 having a hub and at least one blade 4 (in the embodiment of Figure 1, the wind rotor comprises three blades 4, of which only two blades 4 are visible). The wind rotor 5 is rotatable around a rotational longitudinal axis Y. The blades 4 extend substantially radially with respect to the longitudinal axis Y. In general, when not differently speci fied, the terms axial, radial and circumferential in the fol lowing are made with reference to the rotational longitudinal axis Y. The wind turbine 1 comprises at least one electric generator 11, including a stator 20 and a rotor 30. The rotor 30 is rotatable with respect to the stator 20 about the rota tional longitudinal axis Y. The wind rotor 5 is coupled with the rotor 30 and both are connected to an outer ring of a main bearing assembly 8. The outer ring of the main bearing assembly 8 rotates about the rotational longitudinal axis Y with respect to a static inner ring, which is coupled with a main shaft 9 extending along the longitudinal axis Y.

Figure 2 shows an exploded view of the electrical generator 11 with the rotor 30 and the stator 20. The stator 20 com prises a cylindrical inner core 21 to which six segments 45 are attached. Each segment 45 has a circumferential angular extension of 60°. According to other embodiments of the pre- sent invention, the stator 20 comprises a plurality of seg ments having a number of segments different from six. Accord ing to another possible embodiment of the present invention, the stator 20 is not segmented, i.e. the stator includes one single segment covering the entire angular extension of 360°. The rotor 30 has a conventional structure with a plurality of circumferentially distributed rotor permanent magnets 31.

Figures 3 to 5 show more in details a stator segment 45. The stator segment 45 has a conventional structure comprising a plurality of teeth circumferentially interposed between a plurality of slots. The teeth protrude according to the radi al direction. The stator segment 45 further comprises coil windings 48 inserted in the slots of the segment 45. Teeth, slots and windings 48 are not a specific object of the pre sent invention and therefore not described in further de tails. Each segment 45 includes a support structure 50 and a lamination stack 60 supported by the support structure 50.

The support structure 50 circumferentially extends between two circumferential ends 46. At each circumferential end 46, a respective flat bar 51 is provided. The flat bar 51 may be used for joining together the plurality of segments 45, for example by means of a plurality of bolted connections or by welding. The lamination stack 60 comprises a plurality of lamination sheets which are attached one after another along the longitudinal axis Y of the stator 20. The lamination stack 60 is fixed to the support structure 50 as better spec ified in the following. When the stator segments 45 are cir cumferentially joined together, the assembly made by all the support structures 50 and the lamination stack 60 constitutes a stator body. According to the possible embodiment of the present invention where the stator 20 is not segmented, the stator body is made of a single support structure 50 and a single lamination stack 60, both covering the entire angular extension of 360°. In the latter embodiment the flat bars 51 are not present. Figures 6 and 7 show a support structure 50 for a segment 45 according to an embodiment of the invention, in two perspec tive views from the bottom and the top, respectively. The support structure segment 50 is configured for use in a sta tor of a wind turbine. The support structure segment 50 com prises a plurality of carrier elements 200. Each carrier ele ment 200 has a section having approximately the shape of the Greek letter "Omega" (W), such section being extended along longitudinal axis Y. The carrier element 200 is symmetrical with respect to a mirror plane, with the mirror plane passing midway through the carrier element 200 in such a way that the top section 203 is essentially perpendicular to the mirror plane and with the mirror plane being perpendicular to the circumferential direction.

The support structure segment 50 further comprises two pres sure plates 240 at the two longitudinal ends of the support structure 50, respectively. Each of the two pressures plates 240 are fixed, for example by welding, to the inner core 21 of the stator 20. Each carrier element 200 extends longitudi nally from one to the other of the two pressures plates 240.

Figure 8 shows a plurality of carrier elements 200 of the support structure segment 50 according to an embodiment of the invention, in a perspective view. Each carrier element 200 comprises a first and a second base section 201, a first and a second side section 202 and a top section 203. The base section 201 and the top section 203 span circumferentially, while the side section span radially. Each base section 201 is connected to a respective side section 202, oriented rela tive to each other at an outer angle f having a value of ap proximately 90°. Each side section is connected to the top section 203. Each side section 202 forms with the top section 203 an inner angle Q having a value of approximately 90°. The base sections 201 are spaced apart from the top section 203 essentially in a radial direction. The first and the second side section are spaced apart from one another in the circum ferential direction. According to another embodiment of the present invention, at least one carrier element 200 comprises only one base section 201, in particular at the circumferential end section 51 (figure3), which may be formed by one side section 202 of the carrier element 200. In such case, the carrier element 200 has a section having approximately the shape of the Latin letter "Z", such section being extended along longitudinal axis Y.

The top section 203 is configured to be coupled to the lami nation stack 60. This connection is established by means of a fixing connection, for example by means of bolts. In order to establish such a fixing connection a bolt-hole may be provid ed in the top section 203. To this end, the top section 203 forms a plateau which has a suitably extended surface area to enable the formation of bolt-holes therein and to firmly se cure a bolt in the bolt-hole.

The carrier element 200 may be a single-piece carrier ele ment, in particular a monolithically formed carrier element of a metal or a metal alloy. The first base section 201, the first side section 202, the top section 203, the second side section 202 and the second base section 201 constitute the carrier element, in this order from one circumferential end to another circumferential end. At the transition interfaces between the sections the carrier element 200 forms rounded edges.

The base section 201 of at least one carrier element 200 of the plurality of carrier elements 200 is connected to the base section 201 of another one carrier element 200 of the plurality of carrier elements 200. Each connection may be performed for example by means of welding.

With reference to the embodiment of figures 6 to 8, a plural ity of connections (four connections shown in the figures) are established between each base section 201 of one carrier element 200 and the base section 201 of another circumferen tially adjacent carrier element 200. The plurality of connec tions is distributed along the longitudinal axis Y, for exam ple regularly distributed along the longitudinal axis Y, at constant distance between one connection and the following one. The connection is performed through a plurality of con necting elements 205 circumferentially protruding from one base section 201 of one carrier element 200 and connected, for example welded, to another plurality of connecting ele ments 205 circumferentially protruding from one base section 201 of another carrier element 200. Between the connecting elements 205 cooling pockets 206 are formed for cooling air to pass. Each cooling pocket 206 extends along the longitudi nal axis Y between two connections, each connection being performed by joining two connecting elements 205 of two re spective circumferentially adjacent carrier elements 200. Ac cording to other embodiments of the present invention (not shown), any number of connecting element may be provided be tween each base section 201 of one carrier element 200 and the base section 201 of another circumferentially adjacent carrier element 200, for example one connection or two or three connections or any number of connection greater of four. The number of cooling pockets 206 is determined conse quently, for example five cooling pockets 206 are provided in the embodiment of the attached figures.

According to another embodiment of the present invention (not shown), at least one base section 201 of one carrier element 200 extends circumferentially up to the base section 201 of another circumferentially adjacent carrier element 200, the two base sections 201 of the two circumferentially adjacent carrier elements 200 being connected together, for example by means of welding. In such embodiment no cooling pocket 206 is present.

The connections between the carrier element 200 provides a plurality of circumferential stiffeners, so that additional circumferential stiffeners may not be requested in the sup port structure 50.

It should be noted that the term "comprising" does not ex- elude other elements or steps and "a" or "an" does not ex clude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be con strued as limiting the scope of the claims.