A SET OF UNITS FOR MAKING A WIND TURBINE NACELLE

Abstract

A set of units for assembly to form a wind turbine nacelle. The nacelle comprises a rotor-supporting assembly and generator, and a power conversion assembly and the set of units comprises a main unit arranged to be connected to a wind turbine tower and housing the rotor-supporting assembly and the generator, and at least two different auxiliary units each housing an operative component forming part of the power conversion assembly. To allow different wind turbine configurations, one of the auxiliary units can be selected from the at least two auxiliary units and assembled with the main unit to form the nacelle.

Claims

1. A set of units for assembly to form a nacelle for a wind turbine, the nacelle comprising a rotor-supporting assembly, and a power conversion assembly, the set of units comprising: a main unit arranged to be connected to a wind turbine tower and housing the rotor-supporting assembly, and at least two different auxiliary units each housing an operative component forming part of the power conversion assembly, wherein the at least two different auxiliary units have identical interfaces towards the main unit whereby one of the auxiliary units can be selected from the at least two auxiliary units and assembled with the main unit to form the nacelle.

2. The set of units according to claim 1, wherein at least one of the at least two auxiliary units does not form part of the nacelle.

3. The set of units according to claim 2, wherein a generator of the wind turbine is operational with the operative component in each of the auxiliary units, to deliver power from the generator in a converted form without the use of the auxiliary unit not forming part of the nacelle.

4. The set of units according to claim 1, wherein the main unit defines a first interface allowing selectively connection of one of said at least two different auxiliary units, such that each auxiliary units can be attached on the same location on the main unit.

5. The set of units according to claim 4, wherein the main unit defines a second interface on an opposite side of the main unit and allowing selectively connection of one or the other of said at least two different auxiliary units.

6. The set of units according to claim 4, wherein the identical interfaces of the at least two different auxiliary units can be assembled with the first and the second interfaces.

7. The set of units according to claim 5, comprising at least two different auxiliary units configured for the first interface and/or at least two auxiliary units configured for the second interface.

8. The set of units according to claim 1, wherein one of the at least two auxiliary units houses an operative component of a type selected from the group consisting of: transformers, converters, batteries, electrolysis cells, and switch gears, and wherein another of the at least two auxiliary units houses a different operative components of a type selected from the group consisting of: transformers, converters, batteries, electrolysis cells, and switch gears.

9. The set of units according to claim 8, wherein both auxiliary units house an operative component of the same type.

10. The set of units according to claim 9, wherein both operative components of the same type have different power rating.

11. The set of units according to claim 8, wherein the auxiliary units house an operative component of different type.

12. The set of units according to claim 11, wherein the set of units comprises a first line of auxiliary units each housing an operative component of a first type and each operative component having different capacity, and wherein the set of units comprises a second line of auxiliary units housing operative components of a second type, the operative components of the second type interacting with the operative component of the first type during operation of the wind turbine nacelle, and each operative component of the second type having a capacity matching a capacity of one of the operative components of the first type housed in one of the auxiliary units of the first line of auxiliary units.

13. The set of units according to claim 1, wherein the two different auxiliary units having identical interfaces towards the main unit facilitate attachment to at least two different locations on the main unit.

14. The set of units according to claim 13, wherein the at least two different locations on the main unit is a right side location and a left side location on opposite sides of the rotor supporting assembly.

15. The nacelle according to claim 1, wherein the wind turbine comprises a generator located outside the nacelle.

16. The nacelle according to claim 1, wherein the nacelle further houses a generator.

17. A wind turbine comprising a nacelle according to claim 1.

18. A method of making a nacelle by use of a set or units according to claim 1, the method comprising: selecting a main unit and one of the at least two different auxiliary units, and making the nacelle by connecting the selected auxiliary unit to the main unit.

19. The method according to claim 18, comprising leaving at least one of the at least two auxiliary units as an auxiliary unit which does not form part of the nacelle.

20. The method according to claim 18, comprising the step of attaching the nacelle to a wind turbine tower by assembling the main unit and the wind turbine tower.

21. The method according to claim 20, comprising a subsequent step of assembling the auxiliary unit and the main unit after the main unit is attached to the wind turbine tower.

22. The method according to claim 18, comprising defining for each auxiliary unit, constraints defining other auxiliary units configured for interaction with the auxiliary unit in question, or defining other auxiliary units not capable of interaction with the auxiliary unit in question.

23. The method according to claim 18, comprising defining: a desired nacelle configuration; determining a plurality of combinations between at least one main unit and different auxiliary units; defining, for each combination, the resulting nacelle configuration; and selecting a combination based on a comparison of the resulting nacelle configuration and the desired nacelle configuration.

24. The method according to claim 23, wherein the defined desired nacelle configuration and the defined resulting nacelle configuration comprises at least one of a desired grid frequency, an output rated power, and a specific desired climate condition.

25. The method according to claim 18, comprising selecting a combination between a main unit and an auxiliary unit based on a generator power and mean wind speed defined for the main unit and a total rated power of a conversion assembly defined for the auxiliary unit.

26. The method according to claim 18, wherein the main unit and the auxiliary unit is selected to provide a nacelle which produces a chemical substance based on power from the generator.

27. The method according to claim 26, wherein the main unit and the auxiliary unit is selected to provide a nacelle which produces electrical power for a grid in addition to the chemical substance which is produced based on power from the generator.

28. The method according to claim 18, wherein the main unit and the auxiliary unit is selected to provide a nacelle which produces electrical power based on an airborne unit.

29. The method according to claim 18, comprising defining a plurality of combinations of a main unit with different auxiliary units for the left side of the main unit.

30. The method according to claim 18, comprising defining a plurality of combinations of a main unit with different auxiliary units for the right side of the main unit.

31. The method according to claim 18, comprising defining a plurality of combinations of different main units with one or more auxiliary units for the right side of the main unit.

32. The method according to claim 18, comprising defining a plurality of combinations of different main units with one or more auxiliary units for the left side of the main unit.

Description

LIST OF DRAWINGS

[0094] In the following, embodiments of the disclosure will be described in further details with reference to the drawing in which:

[0095] FIGS. 1a and 1b illustrate wind turbines;

[0096] FIG. 2 illustrates the nacelle of the wind turbine;

[0097] FIG. 3 illustrates a perspective view of the nacelle 2 of FIG. 2;

[0098] FIG. 4 illustrates the nacelle from FIG. 3 but seen from above;

[0099] FIG. 5 illustrates an embodiment where the left and right side auxiliary units contain identical components;

[0100] FIG. 6 illustrates an embodiment where two auxiliary units 61, 62 are located one above the other;

[0101] FIGS. 7a and 7b illustrate several units forming a set of units for assembly to form the wind turbine nacelle by selection of one out of at least two units;

[0102] FIG. 8-9 illustrate an embodiment, where the first fixation structure is constituted by bolt shaped fixation pins;

[0103] FIGS. 10, 11 illustrate in further details another embodiment of the first and second fixation structures;

[0104] FIGS. 12-15 illustrate 4 different embodiments of interfaces between the main unit and the auxiliary unit.

[0105] FIGS. 16-18 illustrate an embodiment where the main unit and auxiliary units are assembled by a hinge structure;

[0106] FIGS. 19, 20 illustrate further details of a hook for attaching the auxiliary unit to the main unit;

[0107] FIG. 21 illustrates the hook in an open position where the auxiliary unit is free to be lowered to the ground;

[0108] FIG. 22 illustrates a cross section with two bolt holes for attachment of the auxiliary unit on the main unit;

[0109] FIGS. 23, 24, 25 illustrate an embodiment where the hook is slidingly suspended; and

[0110] FIGS. 26-28 illustrate embodiments of cranes on the main unit for hoisting the auxiliary units.

DESCRIPTION OF EMBODIMENTS

[0111] The detailed description and specific examples, while indicating embodiments, are given by way of illustration only, since various changes and modifications within the spirit and scope of this disclosure will become apparent to those skilled in the art from this detailed description.

[0112] FIGS. 1a and 1b illustrate wind turbines 1 with a nacelle 2 mounted on a tower 3. A hub 4 carrying three rotor blades 5 forms a rotor and is carried by a rotor-supporting assembly in the nacelle 2. Typically, the rotor-supporting assembly comprises a rotor shaft connecting a gear arrangement and a generator to the hub. A gear is, however, not always required since the generator could be directly driven by the shaft. FIG. 1b illustrates a direct drive wind turbine with the generator 6 located outside the nacelle.

[0113] FIG. 2 illustrates that the nacelle comprises a main unit 20 and two auxiliary units 21, 22. A cooling area 23 is arranged on top of the nacelle. The cooling area is formed by a heat exchanger which may form part of the main unit, and/or any of the auxiliary units The main unit 20 is mounted on the tower 3 via a yawing arrangement (not shown), allowing the nacelle 2 to rotate in order to direct the rotor into the wind.

[0114] FIG. 3 illustrates a perspective view of the nacelle 2 of FIG. 2. In FIG. 3 the outer walls of the nacelle 2 are (for the sake of explanation) transparent, thereby revealing the interior parts of the nacelle 2 and the wind turbine components accommodated therein. The main unit 20 accommodates a main bearing unit 31, a gear arrangement 32 and a generator 33, arranged sequentially behind the hub 4, along a direction defined by the rotational axis of the hub 4. The components in the main unit primarily form part of the drivetrain.

[0115] The auxiliary unit 22 accommodates a transformer unit 34, and a converter unit 35 which herein constitute two different operative components being accommodated in the auxiliary unit. In alternative embodiments, the operative component could be an electrolysis cell stack, or a battery.

[0116] Each auxiliary unit 21, 22 is mounted along a side of the main unit 20 via an interface. In the disclosed embodiment, they are mounted in such a manner that one auxiliary unit 21 is mounted along a right side of the main unit 20 and the other auxiliary unit 22 is mounted along a left side of the main unit 20, as seen in a direction along a rotational axis of the hub 4 from the hub 4 towards a rear wall of the main unit 20.

[0117] FIG. 5 illustrates an embodiment where the left and right side auxiliary units contain at least one identical component establishing a weight balance and a double function. The double function means that the wind turbine comprises two identically functioning components, one contained in each of the auxiliary units. In case of failure, the wind turbine may continue operation on reduced power while the operative component in one of the auxiliary units is replaced.

[0118] FIGS. 4 and 5 illustrate a transport system comprising a rail 42 extending from the main unit into the auxiliary unit and allowing easy handling of spare parts etc.

[0119] In FIGS. 2-5, the auxiliary units are constituted by elements having generally the shape and size of standardized freight containers such as a 40 foot shipping freight containers having a dimension and structural specifications as provided by the ISO standard, ISO 668:2013 for series 1 freight containers. The auxiliary units are attached to the main unit by the ISO-corner lifting structure, typically molded in steel and constituting a particularly strong interface to the container. In this embodiment, the one side of the main unit has an auxiliary unit selected between two different auxiliary units such that the resulting nacelle comprises a main unit with a generator and two auxiliary units each housing identical operative components. The two auxiliary unit may not only contain identical operative components, but could be completely identical, i.e. also with respect to the interface towards the main unit and with respect to other parts than the operative component.

[0120] FIG. 6 illustrates an embodiment where two auxiliary units 61, 62 are located one above the other. In this embodiment, the upper auxiliary unit 61 is constituted by unit having the size and shape of a 40 foot shipping freight container, and the lower auxiliary unit 62 is constituted by a unit having the size and shape of a 20 foot shipping freight container. Both containers have a dimension and structural specifications as provided by the ISO standard, ISO 668:2013, and the auxiliary units are attached to each other mainly by the corner lifting arrangements of the 20 foot container, and partly by the corner lifting arrangement of the 40 foot container.

[0121] FIG. 7a illustrates several units forming a set of units for assembly to form the wind turbine nacelle. In this illustration, it is seen that the set comprises a plurality of different auxiliary units which can be selected individually. The set contains more units than needed for making the nacelle, and the set of units therefore allows different configurations based on the selection of units for a nacelle. The units marked with number 71 are main units. The units marked with 72 are left side auxiliary units for attachment to the left side of the main unit, and the units marked with 73 are right side auxiliary units for attachment to the right side of the main unit.

[0122] The set of units additionally comprises a number of drivetrains 74 configured differently, e.g. with respect to main bearing, drive shaft, or gearbox etc. e.g. to provide a desired nacelle configuration, e.g. for a particular climatic condition etc., i.e. e.g. to match a specific wind condition.

[0123] The set of units further comprises several hubs 75 matching rotors of different sizes, e.g. to match different power requirements or climatic conditions. The set further comprises different heat exchangers 76 for matching different needs for cooling and/or different climatic conditions.

[0124] By means of an example, the following units and combinations of units may be defined:

[0125] RX=Right side mount auxiliary unit number X, example: R1 is an auxiliary unit for mounting on the right side of the main unit and having identification number 1 in the set of units.

[0126] LX=left side mount auxiliary unit number X, example: L3 is an auxiliary unit for mounting on the left side of the main unit and having identification number 3 in the set of units

[0127] Main unit/Auxiliary configuration example with Asynchronous or synchronous generator and full converter AC/DC to DC/AC

TABLE-US-00001 Transformer and Rotor Gener- Mean Converter Converter/ dia- Main ator wind- module auxiliary meter unit power speed total units 100 1 3 high 3 MW L1 110 1 2.5 MW medium 2.5 MW L2 120 1 2.0 MW low 2 MW L3 150 2 6 MW high 2 × 3 MW L1 + R1 160 2 5 MW medium 2 × 2.5 MW L2 + R2 165 2 4 MW low 2 × 2 MW L3 + R3 180 3 5.5 MW medium 3 MW + 2.5 MW L1 + R2 170 3 7 MW high 3 + 4 MW L1 + R4

[0128] Main unit/auxiliary units configuration example with a doubly-fed induction generator (DFIG) Generator and partly power converter AC/DC DC/AC:

TABLE-US-00002 Rotor Gener- Converter Converter/ Trans- dia- Main ator module auxiliary former meter unit power total units power 100 1 3 0.6 MW L5 3 MW 110 1 2.5 MW 0.5 MW L6 2.5 MW 120 1 2.0 MW 0.4 MW L7 2 MW 150 2 .sub. 6 MW 2 × 0.6 MW MW L1 + R5 2 × 3 MW

[0129] Main unit/auxiliary units configuration example with AD/DC( ) converter(generator side) and Hydrogen

TABLE-US-00003 Hydrogen AC/DC auxiliary Rotor Gener- Converter Converter/ units With dia- Main ator module auxiliary electrolysis meter unit power 3 MW units cell 100 1 3 MW 3 MW R5 L

[0130] Main unit/auxiliary units configuration example with AD/DC( ) converter(generator side) and storage

TABLE-US-00004 AC/DC Rotor Gener- Converter Converter/ dia- Main ator module auxiliary Flow meter unit power 3 MW units battery 100 1 3 MW 0.6 MW L8 R7

[0131] Main unit/Auxiliary configuration example with Asynchronous or synchronous generator and full converter AC/DC to DC/AC and Kite unit

TABLE-US-00005 AC/DC to Rotor Gener- DC/AC Converter/ dia- Main ator Converter auxiliary Airborne meter unit power module 3 MW units unit 100 1 3 MW 3 MW R1 L9

[0132] The Module L9 is an auxiliary module hosting an airborne unit which is an energy harvesting system where an airborne unit, e.g. a kite or foil, can harvest energy while being airborne, e.g. connected by a cable to the auxiliary unit.

[0133] FIG. 7b illustrate a main unit 20 with an auxiliary unit 73 attached on a right side of the main unit. This auxiliary unit contains a transformer and a converter. On the opposite left side, the nacelle is made with either one of the auxiliary units 72′, 72″ which have identical interfaces towards the main unit. The wind turbine can therefore be configured differently by selection of one or the other of the two auxiliary units 72′, 72″.

[0134] At least one of the two auxiliary units 72′ is an auxiliary unit which does not form part of the nacelle but which allows replacement with a different auxiliary unit.

[0135] The two auxiliary units 72′, 72″ each make the main unit operational and therefore provides two alternative configurations. The upper auxiliary unit 72′ comprises essentially the same components included in auxiliary unit 73 and can therefore be used for changing the power rating. The lower auxiliary unit 72″ contains a different power conversion module, e.g. a fuel cell for converting electric power from the generator into other forms of energy such as hydrogen etc. FIGS. 8-11 illustrate in different embodiments how the operative component can be attached to one or both of the main unit and auxiliary unit.

[0136] In FIG. 8, bolt shaped fixation pins 78 engage into the strengthening feature 79. The bolt shaped fixation pins carry the operative component directly to the main unit and creates a load path from the operative component into the tower.

[0137] FIG. 9 illustrates an embodiment, where the operative component is supported by support legs 91 between a bottom of the operative component and the bottom of the auxiliary unit.

[0138] FIG. 10 illustrates in further details another embodiment where the operative component 104 is carried by the support frame 105 resting on the bottom of the auxiliary unit 102 and it is suspended directly on the main frame 106 inside the main unit 101. The main frame thereby forms part of the load path for the operative component into the tower.

[0139] At least 50 percent of the weight of the transformer 104 is thereby carried by the main unit 101 and the remaining weight is carried by the auxiliary unit 102, which is again carried by the main unit 101. That remaining part of the weight is thereby not carried directly by the main unit 101.

[0140] FIG. 11 illustrates an embodiment comparable to the embodiment in FIG. 10 but where the support frame 111 is suspended via a bracket 1102 which is placed on the main frame 106 inside the main unit 101. The main frame thereby forms a load path for the operative component into the tower.

[0141] FIGS. 12-15 illustrate 4 different embodiments of the unit fixation structure forming the interfaces between the main unit and the auxiliary unit. In each of these four illustrations, the main unit 121 and the auxiliary unit 122 are connected by cooperating structures forming the unit fixation structure and being described in further details below.

[0142] In FIG. 12, the cooperating structures are constituted by brackets 123 by which the main and auxiliary units are joined by bolts.

[0143] In FIG. 13, the cooperating structures are constituted by a lower bracket 123 similar to the one used in FIG. 12. At the upper edge, the main unit and auxiliary unit are assembled by a hook 131 pivotally joined to the main unit at the hinge point 132. The hook can rotate as indicated by the arrow 133 and engages the edge-bracket 134 of the auxiliary unit when in the illustrated position. When the lower bracket 123 is removed, and the hook 131 is rotated into the main unit, the auxiliary unit can be lowered to the ground.

[0144] The embodiment in FIG. 14 is comparable to the embodiment in FIG. 13, but where the lower bracket is replaced with an upper bracket 141, and the hook is placed at a lower edge.

[0145] In FIG. 15, a lower and an upper bracket is used for bolting auxiliary unit to the main unit, and a slidable support 151 supports the lower surface of the auxiliary unit while the bolts are attached. If it is desired to lower the auxiliary unit to the ground, e.g. for replacement of the operative component with a different operative component, the slidable support can be slided to the left and the auxiliary unit can be lowered down, e.g. by use of a crane build into the main unit.

[0146] In any of the embodiments shown in FIGS. 12-15, the brackets or hooks direct the load from the auxiliary unit into a rigid part of the main unit, e.g. into load carrying column e.g. a corner column of the main unit. Various structural features may connect the brackets or hooks which carry the auxiliary unit directly to the main frame in the main unit to thereby establish a load path into the tower.

[0147] In addition to the hook and bracket interface illustrated in FIGS. 12-15, a first fixation structure (not shown) connects an operative component (not shown) directly to the main frame inside the main unit.

[0148] FIGS. 16-18 illustrate an embodiment where the main unit and auxiliary units are assembled by a hinge structure comprising hinge elements 163, 164, 165 with a hole for receiving a hinge pin 166 extending through the hinge elements. FIG. 16 further shows that the interface forms a gap 167 allowing air to pass e.g. from beneath the nacelle to above the nacelle, through the gap. The gab is held open at the bottom by the distance element 168, which could be constituted by a number of pins or an open structure allowing air to pass between the units.

[0149] Such a gap may increase thermal convection and thus cooling of the space inside the main and auxiliary units.

[0150] The gap is not limited to the embodiment with the hinge structure but could be combined with any other assembly method.

[0151] FIGS. 17 and 18 illustrate the hinge elements 163, 164, 165 and the hinge pin 166. In FIG. 17, the hinge elements are positioned correctly relative to the each other such that the hinge pin can be slided into the hinge elements. In FIG. 18, the hinge pin is inserted through the holes of the hinge elements.

[0152] FIG. 19 illustrates further details of a hook for attaching the auxiliary unit 191 to the main unit 192. The hook 193 is suspended rotationally at the hinge 194 in the main unit. The hook can rotate through the opening 195 in the auxiliary unit and catch a recess or edge 196 in the auxiliary unit. The hook could also be attached in the auxiliary unit and catch a recess or edge in the main unit, in which case it may be attached reversely, i.e. as illustrated in FIG. 20.

[0153] FIG. 21 illustrates the hook in an open position where the auxiliary unit is free to be lowered to the ground.

[0154] FIG. 22 illustrates a cross section where two bolt holes 221 can be seen. The bolt holes facilitate attachment of the auxiliary unit on the main unit by use of bolts for solid fixation. In this embodiment, the hook is mainly for positioning the auxiliary unit in the correct height relative to the main unit, and the bolts are for joining the units.

[0155] In FIGS. 19, 21 and 22, the hook is preferably supported by the main frame of the main unit, e.g. via column or support posts arranged along an inner surface of the main unit. In FIG. 19, the column 197 extends along an inner surface of the main unit and supports the hook on the main frame in the bottom part of the main unit.

[0156] In FIG. 20, where the hook forms part of the auxiliary unit, the edge in the main unit where the hook engages, may preferably be carried by the main frame in the main unit. Again, this could be via posts or columns arranged along an inner surface of the main unit.

[0157] The hook could be moved between the open position (FIG. 21) and the closed position (FIG. 19, 20, 22) by power driven means, e.g. including a hydraulically driven actuator.

[0158] FIGS. 23, 24, 25 illustrate an embodiment where the hook is not rotationally suspended but slidingly suspended. The function is similar to the embodiment of FIGS. 19-22. In FIGS. 23 and 24, a cross sectional view illustrates a bolt hole 231 which can be used for solid, bolted fixation of the auxiliary unit on the main unit. The hook in FIG. 23 is attached to the main unit and the hook in FIG. 24 is attached to the auxiliary unit.

[0159] In FIG. 25a, the hook 251 is slided to the left thereby disengaging the edge of the auxiliary unit and allowing the auxiliary unit to be lowered to the ground. In FIG. 25b, the hook 251 is slided to the right, thereby engaging the edge of the auxiliary unit and holding the two units fixed to each other. The hook may be slided by power driven means, e.g. by a hydraulic actuator.

[0160] In the description above, FIGS. 19-25 are explained as parts of the unit fixation structure for fixing the auxiliary unit to the main unit. Similar structures may constitute the first fixation structure by which the operative component is releasably fixed to the main unit. Similar structures may also constitute the second fixation structure by which the operative component is releasably fixed to the auxiliary unit, and similar structures may constitute the third fixation structure by which two auxiliary units are fixed to each other.

[0161] FIG. 26 illustrates hoisting of an auxiliary unit up or down during replacement for reconfiguration purpose. The auxiliary unit is hoisted by use of a crane 261 forming part of the main unit. Movement is essentially only in the vertical plane, illustrated by the arrow 263, and the attachment of the auxiliary unit on the main unit may be facilitated by a unit fixation structure as described previously, including movable fixation features such as hinged or slidable hooks etc.

[0162] FIG. 27 illustrates the internal crane 261 in an enlarged view. The crane is attached to a roof part of the main unit and by its location, it can hoist the auxiliary unit in a vertical direction to a position where said unit fixation structures can form engagement between the main and the auxiliary units. This procedure may not require movement in other directions than the vertical direction and therefore facilitates a simple assembly procedure with reduced need for external crane assistance. For adjustment in a horizontal plane, the crane 261 may have the option of moving horizontally, e.g. as illustrated by the arrow 262.

[0163] FIG. 28 illustrates schematically, another crane structure with a double cantilever beam 281 on the roof of the main unit 282. The cantilever beam 281 can extend sideways in telescopic section 283. The cantilever beam facilitates lifting and connection of the auxiliary unit 284 to the main unit 282. Even though the unit fixation structures disclosed herein, including pivotable or slidable hooks, generally facilitate attachment of the auxiliary unit by hoisting only in the vertical direction, the in and out movement facilitates fine adjustment of a horizontal distance between the main unit and the auxiliary unit.

DEFINITIONS

[0164] Herein, the term “nacelle” means the generally accepted term describing the machine house for a wind turbine, i.e. that part which carries the rotor and drivetrain, and which is carried by the wind turbine tower.

[0165] The terms “main unit” and “auxiliary unit” herein refers to units which can be transported separately, and which can be assembled with one or more other units to form the nacelle.

[0166] Herein, the term “rotor-supporting assembly” refers to those parts of the nacelle which carries the rotor, typically a drivetrain, a main bearing and a main frame. The drivetrain may include different components depending on the type of wind turbine, e.g. a rotor shaft, the generator, and optionally a gearbox between the rotor shaft and the generator.