DK177956B1 - Wind turbine with cable support system arranged in main shaft - Google Patents

Description

Wind turbine with cable support system arranged in main shaft Field of the Invention

The present invention relates to a wind turbine comprising: - a wind turbine tower having at least a top end; - a nacelle arranged at the top end of the wind turbine tower, wherein the nacelle comprises at least a drive train which comprises at least a generator configured to generate an electrical power output; - a rotor comprising a rotor hub configured to be rotatably connected to the nacelle, e.g. via a bearing assembly for transferring loads deriving from the weight of the rotor and the wind acting on the rotor, wherein the rotor further comprises at least one wind turbine blade mounted to the rotor hub and having a tip end connected to a blade root via an aerodynamic profile; and - a rotatable main shaft connected to the rotor hub at one end and connected directly to the generator at another end for at least transferring rotational torque from the rotor to the drive train, wherein the main shaft comprises a hole connected to openings at both ends in which hole a cable support system is arranged for holding any number of electrical cables, e.g. power cables or data cables, extending through at least the main shaft.

The present invention also relates to a method of assembling a cable support system for a wind turbine, such as defined in any one of the preceding claims, where the assembly method comprises the steps of: - arranging any number of electrical cables, e.g. power cables or data cables, relative to at least one support element; - positioning the cable support system in a through hole of a main shaft; and - mounting at least a first end element and a second end element of the cable support system to the main shaft.

Background of the Invention

It is well-known that wind turbines have large aerodynamically designed blades for capturing the incoming wind passing the wind turbine. Typically two or three wind turbine blades are connected to the rotor hub which rotates around a centre axis of a main shaft connected to the drive train in the nacelle. The rotor is supported by the nacelle by means of an interface, such as a rotating bearing assembly, arranged between the nacelle and the rotor. The interface is designed to transfer the weight of the rotor and the loads acting on the rotor to the mainframe of the nacelle and thus the wind turbine tower. The rotor hub is connected to a relative flexible main shaft which in turn extends through the generator. The main shaft is designed to mainly transfer the rotational torque to the drive train located in the nacelle.

Modem wind turbine blades often have any number of sensors, like load sensors or wind speed sensors, arranged along the length of the blades. The blade or a part thereof may further be connected to pitching means for pitching the blade or blade part into a desired pitch angle. These sensors and pitching means are connected to any number of electrical power and/or control cables which extend through a central hole or bore in the main shaft. However, the main shaft may twist up to two degrees during operation which means that the electrical cables are subjected to loads and stresses which could result in a failure. Furthermore, the cables need to be fixed in a relative stable position so that they do not twist or come into contact with the rotating main shaft having a nominal rotation speed, such as 14 rpm. This could change the characteristics of the cable or damage the isolation of the cable.

An alternative embodiment is disclosed in US 4,757,211 A that teaches the use of a main shaft that does not extend through the generator. The rotor hub comprises a cylindrical shaped frame section in which the free end of a tapered frame section of the nacelle is located. The tapered frame section is in turn rigidly connected to the rest of the housing of the nacelle. Two annular bearing units are arranged between the two frame sections so that stmctural load of the rotor hub is supported by the nacelle. The main shaft is connected to a mounting flange in the rotor hub and extends through a central hole in the tapered frame section. The other end of the main shaft is coupled to a gearbox unit which in turn is connected to the generator via a flexible coupling. The generator and gearbox unit must be mounted to vibration damping elements located on the housing in order to compensate for vibrations and bending moments transferred through the main shaft. The vibration damping elements may also be used to compensate for any misalignment in the drive train. However, such elements are subjected to considerable wear and tear and need to be replaced every three to five years which increases the maintenance costs and the downtime. Such vibration damping elements further introduce a variable element when modelling the stresses and loads experienced by the wind turbine, and this makes it more difficult to predict the values of the stresses and loads experienced in the components of the wind turbine.

The main shaft in this configuration comprises a central through hole having an inner diameter that allows the rotor hub to rotate around a tube located in the through hole. The tube extends outwards from the rotor hub and carries the electrical cables for a wind vane located at the end of the tube. The electrical cables are loosely arranged inside the tube, thus allowing dust, moisture or water to enter the nacelle through the opening located outside the rotor hub. The tube is only able to carry the cables to the wind vane, since cables for the sensors at the blades and the pitch mechanisms cannot be arranged in the tube because it extends outside the rotor hub.

Other wind turbines use a main shaft in the form of a rigid support shaft designed to transfer both the rotational torque and the weight and loads of the rotor to the nacelle. Such a wind turbine is disclosed in WO 2012/052023 A1 having a drive train transmission system comprising a hollow generator shaft extending through the generator and the gearbox unit. The generator shaft is in turn coupled to the main shaft that is connected to the rotor hub via the gearbox unit. The hollow generator shaft allows hydraulic tubes and electrical cables to be guided through the generator and the main shaft and into the rotor hub. The two shafts have different internal diameters which mean that the cables and tubes need to be supported inside the larger main shaft; otherwise the tubes and cables are able to move freely around the inside of the rotating shaft during operation. This increases the risk of the tubes or cables hitting the inner surface of the main shaft potentially causing a failure or leakage in the hydraulic tubes. EP 2078856 A2 discloses a cable fixation system arranged inside the main shaft of the wind turbine where the system comprises an elongated support element located at both ends of the main shaft. A plurality of wires are suspended between the two support elements and tensioned by using tensioning means located on one of the support elements. The electrical cables are connected to a plurality of slidable rings or roller bearings distributed along the length of the wires. The support elements are firmly connected to the end flanges of the main shaft so that the cable fixation system follows the rotation of the main shaft. Although the cables are suspended in a number of points along the length of the main shaft, the cables may still move or bend in between the points during operation due to gravity. This could cause the cable to hit the inner surface of the main shaft or break or slide out of the fixation at one or more points. EP 1921310 A1 discloses a gearbox coupled to a rotor wherein a hollow shaft extends through the gearbox, thereby allowing power cables to be guided through the hollow shaft. The cables are fixed to a cable support arranged inside the shaft in a plurality of points, the cable support system being a plate or a rib. This plate or rib may bend or twist along with the deformation of the shaft, thereby causing added wear to the cables. Furthermore, the cables are able to bend or move as they are only supported in a number of points, thus there is a risk that the cables will hit the inner surface of the shaft.

Object of the Invention

It is an object of the invention to provide a wind turbine that improves the above-mentioned drawbacks of the prior art.

An object of this invention is to provide a cable support system that reduces the loads and stresses on the electrical cables.

An object of this invention is to provide a cable support system that supports the cables along the length of the main shaft.

An object of this invention is to provide a method for assembling a cable support system that allows for a quick and simple assembly.

Description of the Invention

An object of the invention is achieved by a wind turbine characterised in that the cable support system comprises at least one support element, e.g. a support rod, having a length which at least corresponds to the length of the main shaft, wherein the support element has any number of receiving sub-elements, e.g. grooves, which extend in an axial direction along the support element and are configured to receive and hold the electrical cables, and the cable support system further comprises at least one outer tube extending along the length of the main shaft in which the support element is arranged.

This provides a cable support system for a wind turbine which maintains the electrical cables in a stable position along the entire length of the main shaft. This prevents the electrical cables from moving or flexing during operation, and thus reduces the stresses experienced in the cables and the risk of the characteristics of the electrical cables changing over time due to fatigue. This configuration is well suited for all types of wind turbines having any number of sensors arranged on or in the wind turbine blades, such as load sensors, displacement sensors, pressure sensors, vibration sensors, or the like. This configuration is also well suited for wind turbines comprising pitchable wind turbine blades (where the entire blade pitches) or partial-pitchable wind turbine blades (where only a part of the blade pitches).

The electrical cables may comprise: power cables for driving the pitch mechanisms, the sensors, or the lightings located in the rotor or blades; data cables for the transmission of control signals between the sensors and the controller of the wind turbine; or other types of electrical cables connected to other types of electrical components located in the rotor hub and/or wind turbine blades. The electrical cables may be arranged in any number of bundles comprising at least two electrical cables. The electrical cables may at the other end be connected to a power source or circuit and/or the controller located in the nacelle.

The term "main shaft" is defined as a rotatable shaft for at least transferring the rotational torque from the rotor to the generator of the drive train, either directly or indirectly, e.g. via an intermediate rotating shaft or a generator shaft. The drive train may further comprise a gearbox unit arranged between the generator and the main shaft for transforming the relative slow rotation of the main shaft into a faster rotation of an intermediate shaft or generator shaft that is connected to the rotor assembly of the generator. The present invention is particularly well-suited for direct-drive wind turbines, i.e. wind turbines in which the gearbox unit is omitted and the rotor is directly coupled to the generator, e.g. via the main shaft.

The structural frame of the rotor hub may be connected to the structural frame of the nacelle, i.e. the main frame, via a rotating coupling, such as one, two or more bearing systems. The rotor hub may comprise a rotor beam or similar frame structure arranged inside the rotor hub. The rotor beam or frame structure may be configured to carry the structural loads of the rotor and the dynamic loads of the wind acting on the rotor. The rotor hub and thus the rotor beam or frame structure may comprise an opening facing the nacelle and a mounting flange for mounting the main shaft located towards the front of the rotor hub, e.g. at the bottom of the cavity connected to the opening. The cavity is configured to receive the main shaft and/or a free end part of the frame structure of the nacelle. The loads may then be transferred to the main frame of the nacelle via the bearing systems and further onto the tower structure, e.g. via the yaw mechanism. The main shaft may then be configured to mainly transfer the rotational torque from the rotor to the generator. This allows the size and weight of the main shaft to be reduced, thereby saving costs.

In another configuration, the internal rotor beam or frame structure may be omitted and the outer housing of the rotor hub may be configured to carry the structural loads of the rotor and the dynamic loads of the wind acting on the rotor. In this configuration, the mounting flange may be located at the opening facing the nacelle. The main shaft may in this configuration be configured to carry the rotational torque and optionally the bending moments, i.e. the loads of the rotor and the wind acting on the rotor.

In yet another configuration, the main shaft may be an intermediate shaft or generator shaft coupled to another shaft which is configured to carry both the rotational torque and the bending moments, such as in WO 2012/052023 Al. The intermediate shaft may be arranged between the rotor and the generator. The generator shaft may be connected to the generator at the rotor side and/or extend through the generator and optionally be connected to the grid side of the generator. In this configuration, the cable support system may be arranged only inside the main shaft or also extend at least partly into the other shaft.

The receiving sub-elements may be arranged along an outer or inner periphery of the support element. The support element may be shaped as a solid or hollow cylindrical element, e.g. a rod or tube. The sub-elements may be configured as grooves or slots extending in a direction parallel to the centre axis of the support element, e.g. located at the periphery of the support element. The sub-elements may instead be configured as through holes connected to openings located at both ends of the support element. The grooves or through holes may have different sizes depending on the type of electrical cable intended to be placed in the groove or through hole. The number of subelements may be between two to twenty, or four to ten. This allows the electrical cables to be placed in the sub-element either from the end surface or the side surface of the support element. The sub-elements may additionally or alternatively be configured to receive any number of hydraulic holes extending through the main shaft.

The support element may be positioned inside an outer tube having an inner diameter or width that more or less corresponds to the outer diameter or width of the support element. The inner surface of the tube is configured to follow the outer contours of the support element. The support element may be a circular, elliptical, squared, triangular, or polygonal shaped cross-sectional profile. This allows the outer tube to help keeping the electrical cables in place during assembly and operation. It also protects the electrical cables and the support element from any external shocks or impacts. The outer tube may have an outer diameter that is no greater than the inner diameter of the main shaft. The support element and/or the outer tube may be made of metal, such as steel, or plastic, such as nylon, or another suitable material.

According to one embodiment, the cable support system comprises a first end element, e.g. a plate, and a second end element, e.g. a plate, wherein the two end elements are located at the openings of the main shaft respectively and connected to the main shaft.

The support element and/or outer tube may be connected to two end elements configured to hold the cable support system in a predetermined position relative to the main shaft, e.g. in a position which more or less corresponds to the centre axis of the main shaft. The end elements may be shaped as plates, elongated elements, X-shaped or Y-shaped elements, wheels with a plurality of spokes, or another suitable shape. The end element may comprise any number of cut-outs for saving material. The end element may be mounted to or form part of the support element and/or the outer tube. The end elements may comprise mounting means, e.g. mounting holes, for mounting the end elements to the main shaft, e.g. an end flange of the main shaft, by using fastening means, such as bolts, nuts, screws, rivets or the like. One or both end elements may comprise a contact surface for contacting a mating contacting surface located on the inner side surface of the through hole in the main shaft.

At least one of the end elements may comprise a bushing or bearing connected to the outer tube so that the end element is able to move, i.e. rotate, relative to the outer tube. This allows the end elements to decouple from the twisting of the main shaft during operation without breaking or damaging the support element or outer tube. This also allows the tube to deform axially independent of the axial deformation of the main shaft.

In one configuration, a gap, e.g. an air gap, may be formed between the outer surface of the support element and/or the outer tube and the inner surface of the through hole in the main shaft. The ratio between the outer diameter of the support element and/or the outer tube and the inner diameter of the through hole in the main shaft may be at least 1:2. The ratio may be 1:2, 1:3, 1:5, 1:10, or any values therein between. This allows the wall thickness of the main shaft to be reduced, thus saving weight and material. The main shaft may have a wall thickness, e.g. measured at a medial point of the main shaft, between 10 and 500 millimetres, 20 and 250 millimetres, or 30 and 100 millimetres.

According to a special embodiment, at least one middle support unit is arranged between the first and second end elements and comprises at least one contact surface for contacting a mating contact surface on a side wall of the through hole.

One or more middle support units may be distributed along the length of the outer tube and thus the support element. The middle support unit may be configured to hold the outer tube and support element in place during the rotation of the main shaft. The middle support units may be connected to the outer tube by means of a mounting flange or form part of the outer tube. The outer tube may comprise a mating mounting flange for mounting the middle support to the outer tube, e.g. via fastening means such as bolt, nuts, screws, rivets, or the like.

In a simple embodiment, the middle support unit may comprise a support plate and/or any number of fingers, preferably at least three, extending outwards from a centre axis of the middle support unit in a radial direction. The fingers may form part of the support plate or be connected directly to the support plate, e.g. by fastening means like bolt, nuts, screws, rivets, or the like. The fingers may project outwards from an outer periphery of the middle support unit, i.e. the support plate. A second support plate may be arranged relative to the first support plate and connected to the first support plate and/or the fingers via a spacer element. The fingers may be arranged between the two support plates. One or two sets of fingers may be used depending on the desired configuration. Each finger or support plate may comprise at least one contact surface for contacting a mating contact surface on a side wall of the through hole in the main shaft. The side wall defines the inner dimensions of the through hole in the main shaft. This allows the middle support unit to contact the side wall of the main shaft in a number of points, thus reducing the amount of force needed to move the middle support unit into the correct position relative to the main shaft. The middle support unit may contact the main shaft more or less along the entire periphery of the side wall, if desired. A friction reducing material, e.g. a lubricant, may be used to position the middle support unit. This allows for an easier installation of the cable support system.

The end elements and/or the middle support element may be of metal, such as steel, or plastic, such as nylon (e.g. polyamide).

According to further special embodiment, the middle support unit further comprises at least two projecting elements, e.g. fingers, extending outwards from an outer periphery of the middle support, wherein at least one of the two projecting elements is a moveable element configured to move in a radial direction relative to a centre axis of the middle support unit.

At least one of the fingers or a second type of fingers may be shaped as a moveable element or finger which is configured to be moved in a radial direction relative to the centre axis of the middle support unit. The moveable element may be configured to be guided along a track and/or groove. All or some of the fingers may be shaped as moveable elements. The moveable finger may be connected to the support plate(s) by one or more adjusting mechanisms arranged on the finger and/or the support plate(s).

The adjusting mechanism may comprise one or more bolts connected to at least one of the fingers and support plates or comprise separate bolts extending though a mounting hole in the fingers or support plates. The free end of the bolt may be arranged in an elongated hole or a series of holes on the adjacent element for adjusting the position of the moveable finger. A nut may be used to fix the moveable element in a desired position.

According to a special embodiment, an adjusting mechanism is connected to the movable element and configured to move that element when the adjusting mechanism is activated.

The adjusting mechanism may be configured to be activated by means of a tool which allows the moveable finger to be moved when the adjusting mechanism is activated. The adjusting mechanism may be spring loaded by means of a spring element, e.g. a compression spring of torsion spring, arranged relative to one of the bolts or the moveable finger. The spring force stored in the spring element by activating the mechanism may be used to move the finger in a radial direction, e.g. by means of a second moveable element. The second moveable element, e.g. a wedge-shaped element, may have a contact surface, e.g. an inclined surface, for contacting a mating contact surface on the moveable finger, e.g. another inclined surface. When the mechanism is activated, the second moveable element causes the moveable finger to be moved away from or towards the centre axis. Another type of adjusting mechanism may be used instead.

The adjusting mechanism may be shaped to function as a release mechanism which allows the moveable finger to be placed in a retracted position and then locked. When the middle support unit is placed in the desired position relative to the main shaft, the release mechanism may then be activated so that the moveable finger is brought into contact with the side wall of the through hole of the main shaft. Two or more of the fingers extending radically outwards from the middle support unit may be shaped as moveable fingers. This allows for an easier positioning of the middle support unit and thus positioning of the cable support system relative to the main shaft.

According to one embodiment, the main shaft is connected to a gearbox unit or a generator in the drive train and/or at least one of the support elements, and the outer tube comprises two or more sections that are placed in a consecutive order and connected to each other.

The generator may be arranged in the opposite end of the nacelle relative to the rotor where the main shaft may at least extend from the rotor to the generator or a gearbox unit. The main shaft may be connected to the mounting flange of the rotor hub, e.g. located at the bottom of the rotor beam. The main shaft may be connected to a mounting flange located at the rotor side or grid side of the generator or the gearbox unit. The main shaft may extend through the gearbox unit and may optionally be coupled to a generator shaft which in turn is connected to the rotor assembly arranged inside the generator. The main shaft or generator shaft may at the grid side be connected to a slip ring unit having any number of phases or terminals connected to the electrical cables located inside the main shaft. Another set of electrical cables may be connected to the slip ring unit and to another electrical component in the wind turbine structure. This allows the weight distribution of the nacelle to be balanced and provides easier access to the generator. This allows for an easier installation and servicing of the generator compared to a generator located at the rotor end.

The support element and/or the outer tube may comprise any number of sections distributed along the length of the cable support system. The sections may be distributed in a consecutive order and interconnected to each other, e.g. via fastening means. The fastening means, e.g. a threaded bolt or nut, may be arranged at the junction between two adjacent sections. Another fastening mean, e.g. a mating threaded bolt or nut, located in the junction on the opposite facing end surface may be used to connect the two sections. Alternatively or additionally a separate fastening mean in the form of a threaded rod may be arranged in a central hole of the support element and used to connect the two sections. The outer tube sections may be connected by means of mounting flanges located at one or both ends of the tube sections.

In one embodiment, the middle support unit may be connected to at least one of the mounting flanges of the outer tube sections located at the junction. This allows for a simple and easy connection of the middle support unit to the outer tube, since no addi tional mounting flanges are needed. Additionally or alternatively, another mounting flange located on the outer tube may be used to keep the middle section in the desired position. This allows the middle support unit or multiple middle support units to be arranged along the length of the outer tube.

The outer tube and/or the support element may have a length that at least corresponds to the length of the main shaft. The outer tube and/or the support element may further comprise a section that extends through the generator, i.e. has a length that at least corresponds to the length of the generator. The length of the outer tube and/or support element may be at least 3 meters or between 3 and 15 meters, 4 and 12 meters, or 5 and 10 meters. Each section of the outer tube and/or the support element may have a length of at least 400 millimetres or at least 1000 millimetres. The sections of the support element may have a length that differs from the length of the outer tube.

According to one embodiment, the main shaft is made of a composite material.

The main shaft may be configured as a relative flexible main shaft capable of flexing or bending relative to its initial position while having a high torsional strength. The main shaft may be made of a composite material, such as a filament wound shaft, a pre-impregnated fibre composite shaft, a slatted-construction shaft (shaft formed by a plurality of slats arranged in a longitudinal or helical order connected to each other by using a suitable flexible adhesive) or another suitable composite shaft. Fibres in such a shaft may be chosen among different types of fibres e.g. glass, carbon, basalt, aramid, or organic fibres. In one exemplary configuration, the main shaft may be made a nanocomposite material, e.g. comprising nano clay, carbon nano tubes, nano silica, or another suitable nanocomposite material. This allows the main shaft to prevent the transfer of bending moments from the rotor to the drive train, particularly the generator. This allows the components of the drive train to be mounted to the main frame without having to take into account the bending loads, thus making the servicing as well as the removal and replacement of the various components easier.

The material of the main shaft may be selected so that one end of the shaft is capable of twisting within a predetermined angular interval relative to the other end when the main shaft is loaded by the rotor and/or the generator. The main shaft may be made of metal, such as steel for adding structural strength, or an electrically insulating material, such as fibre reinforced composite material, for preventing the transmission of current in the event of a lightning strike.

An object of the invention is also achieved by a method of assembling a cable support system for a wind turbine characterised in that, the electrical cables, e.g. power cables or data cables, are placed in any number of receiving sub-elements located in the support element, wherein the sub-elements extend in an axial direction along the cable support system.

This allows for a simple and easy method of assembling a cable support system that supports the electrical cables along the entire length of the main shaft unlike the system of EP 2078856 A2. This configuration allows the electrical cables to be placed in the receiving sub-elements before or after the cable support system is placed in the main shaft. The support element may be shaped as a cylindrical or solid element, e.g. a rod or tube, where the sub-elements are shaped as grooves located at the periphery of the outer side surface or through holes located inside the support element. This allows for an easier placement of the electrical cables, since they do not have to be connected to a plurality of slidable rings or roller bearings as in EP 2078856 A2. This configuration allows the cable support system to be assembled and installed in the main shaft before it is installed in the nacelle.

According to one embodiment, the support element is further positioned in at least one outer tube enclosing the support element either before or after placing the electrical cables in the sub-elements of the support element.

The outer tube may be used to keep the electrical cables in place in the grooves and protects the electrical cables from external shocks and impacts unlike the slidable rings or roller bearings of EP 2078856 A2. The support element and/or the outer tube may comprise two or more sections that may be interconnected before placing the electrical cables in the sub-elements. The sectional configuration of the support element and/or the outer tube allows the length of the cable support system to be adapted to the desired length in a simple and easy manner. It also allows the support element and/or the outer tube to be assembled section by section, as the electrical cables are guided into place on the support element.

According to one embodiment, at least one middle support element is positioned in a first position relative to at least one of the end elements.

The main shaft may comprise a through hole that has an inner diameter which is greater than the outer diameter of the outer tube so that a gap, e.g. an air gap, is formed between the two units. One or more middle support units may be positioned along the length of the outer tube before installing the cable support system in the main shaft. The middle support unit may comprise a central hole that allows it to be slided into position on the outer tube. The middle support units may then be connected to one or more mounting flanges located at the ends of the tube sections or therein between. This allows the cable support system to be supported in a number of points along the length of the main shaft. This configuration also allows the cable support system to be installed in a quick and simple manner, since the middle support unit only contacts the side wall of the through hole in the main shaft in a number of points which reduces the amount of friction between the two units. A first and second end element in the form of an end plate may then be connected to the outer tube at both ends of the main shaft. Alternatively, one of the end elements may be connected to the outer tube before positioning the cable support system in the main shaft. This allows the through hole of the main shaft to be at least partly closed off.

According to a special embodiment, the position of at least one of the end elements or middle support units is adjusted relative to a centre axis of the through hole of the main shaft, e.g. by moving at least one moveable element of that end element or middle support unit in a radial direction relative to a centre axis of that end element or middle support unit.

After the cable support system have been positioned in the main shaft, the position of the support element and the outer tube may be adjusted by activating an adjusting mechanism located on one or more of the middle support units and/or the end ele- ments. The support element and the outer tube may be aligned with the centre axis of the main shaft by moving a moveable element in the form of a finger in a radial direction relative to the centre axis of the middle support unit and/or end element. The adjusting mechanism may be activated by means of a tool before, under or after the positioning of the cable support system in the main shaft. The adjusting mechanisms may be activated individually after the cable support system has been positioned in the main shaft. This allows the support element and thus the electrical cables to be placed in a central position in the main shaft which reduce the centrifugal forces acting on the cable support system during the rotation of the main shaft.

The moveable finger may be locked in a retracted position before the cable support system is positioned in the main shaft, and then released thereafter. This allows for an easier positioning of the cable support system and allows each middle support unit to be centralised before or during the positioning of the cable support system.

The present invention may further relate to a wind turbine comprising: - a wind turbine tower having at least a top end; - a nacelle arranged at the top end of the wind turbine tower, wherein the nacelle comprises at least a drive train which comprises at least a generator configured to generate an electrical power output; - a rotor comprising a rotor hub configured to be rotatably connected to the nacelle, e.g. via a bearing assembly for transferring loads deriving from the weight of the rotor and the wind acting on the rotor, wherein the rotor further comprises at least one wind turbine blade mounted to the rotor hub and having a tip end connected to a blade root via an aerodynamic profile; - a rotatable main shaft connected to the rotor hub at one end and connected directly to the generator at another end for at least transferring rotational torque from the rotor to the drive train, wherein the main shaft comprises a hole connected to openings at both ends in which hole a cable support system is arranged and comprises at least one outer tube for holding any number of electrical cables, e.g. power cables or data cables, extending through at least the main shaft; characterised in that: - the cable support system comprises a first end element, e.g. a plate, and a second end element, e.g. a plate, located at the openings of the main shaft respectively, wherein at least one middle support unit is arranged between the first and second end elements and comprises at least one contact surface for contacting a mating contact surface of the through hole in the main shaft.

This provides a cable support system for a wind turbine which maintains the cable support system in a predetermined position relative to the main shaft along the entire length of the main shaft. The outer tube protects the electrical cables and the support element from any external shocks or impacts. The outer tube may have an outer diameter that is no greater than the inner diameter of the main shaft. The outer tube holds the electrical cables in a position more or less corresponding to the centre axis of the main shaft. This configuration is well suited for all types of wind turbines having any number of sensors arranged on or in the wind turbine blades, such as load sensors, displacement sensors, pressure sensors, vibration sensors, or the like. This configuration is also well suited for wind turbines comprising pitchable wind turbine blades (where the entire blade pitches) or partial-pitchable wind turbine blades (where only a part of the blade pitches).

According to one embodiment, the through hole of the main shaft has a side wall defining an inner diameter and the element holding the electrical cables has an outer surface defining an outer diameter, wherein a gap, e.g. an air gap, is formed between the outer surface and the side wall, wherein the ratio between the outer diameter and the inner diameter is at least 1:2.

This configuration allows a gap, e.g. an air gap, to be formed between the outer surface of the element holding the electrical cables, e.g. an outer tube or a support element in which the cables are arranged, and the inner surface of the through hole in the main shaft. The ratio between the outer diameter of the support element and/or the outer tube and the inner diameter of the through hole in the main shaft may be at least 1:2. The ratio may be 1:2, 1:3, 1:5, 1:10, or any values therein between. This allows the wall thickness of the main shaft to be reduced, thus saving weight and material. The main shaft may have a wall thickness, e.g. measured at a medial point of the main shaft, between 10 and 500 millimetres, 20 and 250 millimetres, or 30 and 100 millimetres. The end elements and/or the middle support element may be of metal, such as steel, or plastic, such as nylon (e.g. polyamide).

According to a special embodiment, the middle support unit further comprises at least two projecting elements, e.g. fingers, extending outwards from an outer periphery of the middle support, wherein at least one of the two projecting elements is a moveable element configured to move in a radial direction relative to a centre axis of the middle support unit.

At least one of the fingers or a second type of fingers may be shaped as a moveable element or finger which is configured to be moved in a radial direction relative to the centre axis of the middle support unit. The moveable element may be configured to be guided along a track and/or groove. All or more of the fingers may be shaped as moveable elements. The moveable finger may be connected to the support plate or plates by one or more adjusting mechanisms arranged on the finger and/or the support plate(s). The adjusting mechanism may comprise one or more bolts connected to at least one of the finger and the support plates or separate bolts extending though a mounting hole in the finger or support plate. The free end of the bolt may be arranged in an elongated hole or a series of holes on the adjacent element for adjusting the position of the moveable finger. A nut may be used to fix the moveable element in a desired position.

According to a special embodiment, an adjusting mechanism is connected to the movable element and configured to move that element when the adjusting mechanism is activated.

The adjusting mechanism may be configured to be activated by means of a tool which allows the moveable finger to be moved when the adjusting mechanism is activated. The adjusting mechanism may be spring loaded by means of a spring element, e.g. a compression spring of torsion spring, arranged relative to one of the bolts or the moveable finger. The spring force stored in the spring element by activating the mechanism may be used to move the finger in a radial direction, e.g. by means of a second moveable element. The second moveable element, e.g. a wedge-shaped element, may have a contact surface, e.g. an inclined surface, for contacting a mating contact surface on the moveable finger, e.g. another inclined surface. When the mechanism is activated, the second moveable element causes the moveable finger to be moved away or towards from the centre axis. Another type of adjusting mechanism may be used instead.

The adjusting mechanism may be shaped to function as a release mechanism which allows the moveable finger to be placed in a retracted position and then locked. When the middle support unit is placed in the desired position relative to the main shaft, the release mechanism may then be activated so that the moveable finger is brought into contact with the side wall of the through hole of the main shaft. Two or more of the fingers extending radially outwards from the middle support unit may be shaped as moveable fingers. This allows for an easier positioning of the middle support unit and thus the cable support system relative to the main shaft.

According to one embodiment, the cable support system comprises at least one support element, e.g. a support rod, having a length corresponding at least to the length of the main shaft, wherein the support element has any number of receiving subelements, e.g. grooves, which extend in an axial direction along the support element and are configured to receive and hold the electrical cables.

This provides a support element that maintains the electrical cables in a stable position along the entire length of the main shaft. This configuration also prevents the electrical cables from moving or flexing during operation, thus reduces the stresses experienced in the cables and the risk of the characteristics of the electrical cables changing over time due to fatigue.

Description of the Drawing

The invention is described by example only and with reference to the drawings, wherein:

Fig. 1 shows an exemplary embodiment of a pitchable wind turbine according to the invention;

Fig. 2 shows an exemplary embodiment of a partial-pitch wind turbine according to the invention;

Fig. 3 shows an exemplary embodiment of the rotor connected to the nacelle;

Fig. 4 shows the grid side of the generator shown in fig. 3;

Fig. 5 shows a cable support system according to the invention;

Fig. 6 shows the outer tube of the cable support system shown in fig. 5;

Fig. 7 shows the support element of the cable support system shown in fig. 5;

Fig. 8 shows the outer tube and the support element when assembled;

Fig. 9 shows the outer tube and support element shown in fig. 8 seen from one end;

Fig. 10 shows an exploded view of the middle support unit shown in fig. 5.

Fig. 11 shows a cut-out of the middle support unit shown in fig. 10; and Fig. 12 shows the mounting of the middle support unit to the outer tube.

In the following text, the figures will be described one by one and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure.

Reference list 1 Pitchable wind turbine 2 Ground level 3 Foundation 4 Wind turbine tower 5 Nacelle 6 Rotor hub 7 Wind turbine blades 8 Tip end 9 Blade root 10 Pressure side 11 Suction side 12 Leading edge 13 Trailing edge 14 Partial-pitch wind turbine 15 Wind turbine blades 16 Inner blade section 17 Outer blade section 18 Pitch junction 19 Main shaft 20 Generator 21 Opening in main shaft 22 Cable support system 23 Main frame of nacelle 24 Yaw bearing 25 Openings of main frame 26 Rotor beam of rotor 27 Opening of rotor beam 28 Mounting flange 29 Front end 30 Mounting flange of main shaft 31 Mounting flange of generator 32 Grid side 33 Rotor side 34 Slip ring unit 35 Outer tube 36 Openings of outer tube 37 First end element 38 Second end element 39 Mounting flange of generator 40 Bushing 41 Middle support unit 42 Contact surface 43 Support element 44 Tube sections 45 Mounting flanges 46 Sections of support element 47 Treated rod 48 Nut, nut extension 49 Fastening means, bolts 50 Sub-elements, grooves 51 Outer periphery, contact surface 52 Side wall, contact surface 53 Support plates 54 Spacer element 55 Fingers 56 Peripheral edge 57 Moveable finger 58 Radial direction 59 Recesses 60 Adjusting mechanism 61 Elongated hole 62 Fastening mean, bolt 63 Bushings

Detailed Description of the Invention

Fig. 1 shows an exemplary embodiment of a pitchable wind turbine 1 according to the invention. The wind turbine 1 is arranged relative to a ground level 2 or even a sea level. The wind turbine 1 comprises a wind turbine tower 3 having a top end and a bottom end facing away from the top end. The bottom end is configured for mounting to a mounting end of a foundation 4. The wind turbine tower 3 may comprise two, three or more tower sections (not shown) that are mounted together to form the wind turbine tower 3. A nacelle 5 is arranged at the top of the wind turbine tower 3 and is rotatably connected to the wind turbine tower 3, e.g. via a yaw mechanism (not shown). A rotor having a rotor hub 6 is rotatably connected to the nacelle 5, e.g. via a bearing assembly between the rotor hub 6 and the main frame structure of the nacelle 5. Two or more wind turbine blades 7 (three wind turbine blades are shown), in the form of pithable wind turbine blades are connected to the rotor hub 6, e.g. via one or more pitch mechanisms (not shown). The wind turbine blades 7 extend outwards from the centre of the rotor hub 7 to form a plane of rotation where each blade 7 comprises a tip end 8 and a blade root 9. Each blade 7 comprises a first surface defining a pressure side 10 connected to a second surface defining a suction side 11 via a leading edge 12 and a trailing edge 13.

Fig. 2 shows an exemplary embodiment of a partial-pitch wind turbine 14 according to the invention. In this configuration, the wind turbine blades 15 are configured as partial-pitch blades having at least an inner blade section 16 and an outer blade section 17. The outer blade section 17 is connected to the inner blade section 16 via another pitch mechanism (not shown) arranged at a pitch junction 18. The pitch mechanism is configured to pitch the outer blade section 17 relative to the inner blade section 16 according to a pitch angle. The inner blade section 16 has a first blade end, i.e. an outer blade end, facing the tip end 8. The outer blade section 17 has a second blade end, i.e. an inner blade end, facing the blade root 9. The blade sections 16, 17 may have the same aerodynamic profile or different aerodynamic profiles, e.g. a stall-controlled inner blade section 16 and a pitch-controlled outer blade section 17.

Fig. 3 shows an exemplary embodiment of the rotor and the nacelle 5 where a part of the structures is removed for illustrating the interior of the structures. A main shaft 19, for transferring at least a rotational torque from the rotor to a generator 20 in the nacelle 5, is connected to the rotor hub 6 at one end. The main shaft 19 is at the other end connected directly to the generator 20. The main shaft 19 comprises a through hole (not shown) connected to an opening 21 in both ends. A cable support system 22 is arranged in the through hole, as shown in fig. 3. The main shaft 19 is a relative flexible main shaft capable of flexing relative to its initial position whilst having a high torsional strength. The main shaft 19 is made of a composite material, such as a filament wound shaft, a pre-impregnated fibre composite shaft, a slatted-construction shaft or another suitable composite shaft. The material of the main shaft 19 is selected so that one end of the shaft is capable of twisting within a predetermined angular interval relative to the other end, when the main shaft 19 is loaded by the rotor and/or the generator 20.

The nacelle 5 comprises a support structure in the form of a main frame 23 connected to a yaw mechanism having a yaw bearing 24 arranged at the top of the wind turbine tower 3. The main frame 23 has a cavity connected to an opening 25a facing the generator 20 and an opening 25b facing the rotor hub 6. The main frame 23 is configured to carry the structural loads and the loads generated by the incoming wind acting on the nacelle 5. These loads are then transferred to the wind turbine tower 3 via the yaw bearing 24.

The rotor hub 6 comprises a support structure in the form of a rotor beam 26 arranged inside an outer housing of the rotor hub 6. The rotor beam 26 is configured to carry the structural loads and the loads generated by the incoming wind acting on the rotor hub 6. The rotor beam 26 comprises a cavity connected to an opening 27 facing the nacelle 5. A mounting flange 28 for mounting to a mating mounting flange of the main shaft 19 is located towards the front 29 of the rotor hub 6, e.g. at the bottom of the cavity of the rotor beam 26. The rotor beam 26 is rotatably connected to the main frame 23 via a rotating coupling in the form of two bearing systems for transferring the loads of the rotor to the main frame 23 of the nacelle 5.

The main shaft 19 is arranged in the cavities of the rotor beam 26 and the main frame 23 and extends through the openings 25b, 27 of the nacelle 5 and the rotor hub 6. The main shaft 19 comprises a mounting flange 30 located at the opposite end for mounting to a mating mounting flange 31 of the generator 19.

Fig. 4 shows the generator 20 having a grid side 32 and a generator side 33. The generator 20 is configured to generate an electrical power output and comprises a rotor assembly (not shown) arranged relative to a stator assembly (not shown).

The cable support system 22 is arranged inside the through hole of the main shaft 19 and extends through the rotor assembly of the generator 20, as shown in fig. 4. The cable support system 22 is at the grid side 32 connected to a slip ring unit 34. The slip ring unit 34 comprises any number of phases, i.e. terminals, which are electrically connected to any number of electrically cables (not shown) located in the main shaft 19. The phases of the slip ring unit 34 is further connected to another set of electrical cables having any number of cables which are connected to various electrical components located in the wind turbine structure.

Fig. 5 shows the cable support system 22 according to the invention before it is installed in the main shaft 19. The cable support 22 comprises an outer tube 35 having a first part 35a extending along the length of the main shaft 19 and a second part 35b extending through the generator 20.

The outer tube 35 comprises a first opening 36a at which a first end element 37 in the form of an end plate is arranged and a second opening 36b located at the grid side 32 of the generator 20. A second end element 38 in the form of an end plate is arranged at a predetermined position on the outer tube 35 relative to the second opening 36b. The end elements 37, 38 comprise mounting means, e.g. mounting holes, for mounting to the mounting flange 28 and a mounting flange 39 of the generator 20, e.g. the rotor assembly.

The end elements 37, 38 are configured to hold the cable support system 22 in a predetermined position relative to the main shaft 19, e.g. in a position more or less corresponding to a centre axis of the main shaft 19. Both end elements 37, 38 comprises a contact surface 39 for contacting a mating contacting surface (not shown) located on the side wall of the through hole in the main shaft 19. At least one of the end elements 37 comprises a bushing 40 connected to the outer tube 35 so that the end element 37 is able to move, i.e. rotate, relative to the outer tube 35.

One or more middle support units 41 are distributed along the length of the outer tube 35 and are arranged between the end elements 37, 38, as shown in fig. 5. The middle support unit 41 is configured to hold the cable support system 22 in the predetermined position relative to the main shaft 19, e.g. in a position more or less corresponding to a centre axis of the main shaft 19. The middle support unit 41 comprises a contact surface 42 for contacting a mating contact surface (not shown) located on the side wall of the through hole in the main shaft 19.

Fig. 6 shows the outer tube 35 of the cable support system 22 separated from a support element 43 of the cable support system 22. The outer tube 35 comprises a first tube section 44a connected to a second tube section 44b. Each tube section 44a, 44b comprises a mounting flange 45a, 45b for mounting the two tube sections 44a, 44b together by using fastening means, such as bolts and nuts.

Fig. 7 shows the support element 43 of the cable support system 22 which is arranged inside the outer tube 35 when assembled. The support element 43 comprises any number of sections 46 (three sections are shown), connected together by using fastening means, such as bolts and nuts. A threated rod 47 is positioned along the centre axis of the support element 43 and is connected to a mating threated nut or nut extension 48.

The support element 43 and/or the outer tube 35 have a total length defined by the sections 44, 46 of at least 3 metres. The end elements 37, 38 and/or the middle support element 41 may be of metal, such as steel, or plastic, such as nylon.

Figs. 8 and 9 show the outer tube 35 and the support element 43 when assembled. The outer tube 35 is connected to the support element 43 by using fastening means 49, such as bolts. The support element 43 is shaped as a support rod having any number of sub-elements 50 configured to receive and hold the electrical cables, as shown in fig. 8.

The sub-elements 50 are shaped as grooves arranged along an outer periphery 51 of the support rod 43. The periphery 51 comprises a contact surface for contacting a mating contact surface of the inner side wall 52 of the outer tube 35, as shown in fig. 9. The sub-elements 50 are arranged in different groups 50a, 50b, 50c having different sizes for receiving different types of electrical cables. A first group 50a is configured to receive power cables, a second group 50b is configured to receive data cables, and a third group 50c is configured to receive a third type of electrical cables, e.g. cables for controlling the lightings located in the rotor.

Fig. 10 shows an exploded view of the middle support 41 comprising two support plates 53 spaced apart by a spacer element 54 in the form of an annular shaped element. Any number of fingers 55, (three fingers are shown), are arranged between the two support plates 53. The fingers 55 project outwards from a centre axis of the middle support unit and/or a peripheral edge 56 of the support plate 53 in a radial direction where the contact surface 42 is located on the peripheral edge of each finger 55. Each finger 55 comprises mounting means in the form of mounting holes for mounting the fingers 55 to the mating mounting means, e.g. mounting holes, on the support plates 53 by using fastening means 56, e.g. bolts and nut.

At least one of the fingers is a moveable finger 57 configured to move in a radial direction (marked by arrow 58) relative to the centre axis of the middle support unit 41. One of the support plates 53 and/or the spacer element 54 comprises a recess 59 for receiving an adjusting mechanism 60, e.g. a wedge shaped element 60a. The moveable finger 57 comprises a contact surface, e.g. an inclined surface, located in the recess 59 for contacting a mating contact surface 61 of the wedge shaped element 60a. The wedge shaped element 60a is connected to activating means in the form of a bolt 60b arranged relative to a bushing 60c and a spring element 60d, e.g. a compression spring. The spring element 60d applies a spring force to the bolt 60b so that the wedge shaped element 60a is moved relative to the support plate 53a. An elongated hole 62 is arranged in the moveable finger 57 for adjustably mounting the finger 57 to the support plates 53 by using a fastening mean 63 in the form of a bolt and a nut.

Fig. 11 shows a cut-out of the middle support unit 41 of the cable support system 22 when positioned relative to the length of the outer tube 35. The middle support unit 41 is mounted to the mounting flanges 45a, 45b of the tube sections 44a, 44b by means of fastening means extending through the middle support unit 41 and the mounting flanges, as shown in fig. 11. Bushings 64 are used to align the middle support unit 41 with the mounting flanges 45a, 45b.

Fig. 12 shows an assembly step of mounting the middle support unit 41 to the outer tube. Firstly, the sections 46 of the support element 43 are connected to each other to form the desired length. The electrical cables (not shown) are then placed in the subelements 50 of the support element 43. The support element 43 with the electrical cables is then positioned in the outer tube 35 so that the outer tube 35 encloses the entire outer side surface of the support element 43.

The middle support unit 41 is moved, e.g. slided, into position on one of the tube sections 44a and aligned with the mounting flange 45a of that tube section 44a. The middle support unit 41 and the tube sections are then connected to each other by using the fastening means.

The cable support system 22 is then positioned in the main shaft 19. The position of the support element 43 and the outer tube 35 is then adjusted by activating the adjusting mechanism 60 located on the middle support unit 41 by using a tool configured to engage the bolt 60b. When activating the adjusting mechanism 60, the wedge shaped element 60a is moved relative to the support plate 53a causing the moveable finger 57 to be moved in the radial direction 58. The position of the support element 43 and the outer tube 35 is thereby aligned with the centre axis of the through hole in the main shaft 19. The end elements 38 are finally connected to the support element 43 and/or the outer tube 35 and the mounting flanges 28, 39.

Claims (11)

1. Vindturbine omfattende: - vindturbinetåm (4) med mindst en topende, - en maskinkabine (5) arrangeret ved vindturbinetårnets (4) topende, hvori maskinka-binen (5) omfatter mindst en transmission, der omfatter mindst en generator (20) konfigureret til at generere en elektrisk udgangseffekt, - en rotor omfattende et rotomav (6) konfigureret til at være roterbart forbundet med maskinkabinen (5), f.eks. via en lejesamling for overføring af belastninger fra rotorens vægt og vindpåvirkningen på rotoren, hvori rotoren yderligere omfatter mindst et vindturbineblad (7), som er monteret på rotornavet og har en spidsende (8) forbundet med en bladrod via et aerodynamisk profil, - en roterbar hovedaksel (19) forbundet med rotornavet (6) ved en ende og forbundet direkte på generatoren (20) ved en anden ende for i det mindst delvist at overføre drejningsmoment fra rotoren til transmissionen, hvori hovedakslen (19) omfatter et hul forbundet med åbninger i begge ender, i hvilket hul et kabelstøttesystem (22) er arrangeret for at holde ethvert antal elektriske kabler, f.eks. strømkabler eller datakabler, der strækker sig gennem i det mindste hovedakslen, kendetegnet ved, at - kabelstøttesystemet (22) omfatter mindst et støtteelement (43), f.eks. en støttestang, der har en længde mindst svarende til længden af hovedakslen (19), hvori støtteelementet (43) har et antal optagende delelementer (50), f.eks. riller, som strækker sig i en aksialretning langs støtteelementet (43) og er konfigureret til at optage og holde de elektriske kabler, og at kabelstøttesystemet (22) yderligere omfatter mindst et yderrør (35), der strækker sig i hovedakslens (19) længde, i hvilken støtteelementet (43) er arrangeret.

2. Vindturbine ifølge krav 1, kendetegnet ved, at kabelstøttesystemet (22) omfatter et første endeelement (37), f.eks. en plade, og et andet endeelement (38), f.eks. en plade, hvori de to endeelementer henholdsvis er placeret ved hovedakslens (19) åbninger og forbundet med hovedakslen (19).

3. Vindturbine ifølge krav 2, kendetegnet ved, at mindst en midterstøtteenhed (41) er arrangeret mellem de første og andre elementer (37, 38) og omfatter mindst en kon taktflade (42) for anlæg mod en dertil passende kontaktflade på en sidevæg af det gennemgående hul.

4. Vindturbine ifølge krav 3, kendetegnet ved, at midterstøtteenheden (41) yderligere omfatter mindst to fremspringende elementer (55), f.eks. fingre, der strækker sig udad fra en ydre periferi af midterstøtten (41), hvori mindst et af de to fremspringende elementer er et bevægeligt element (57), som er konfigureret til at bevæges i radiel retning (58) i forhold til en centerakse af midterstøtteenheden (41).

5. Vindturbine ifølge krav 4, kendetegnet ved, at en justeringsmekanisme (60) er forbundet med det bevægelige element (57) og konfigureret til at bevæge dette element, når justeringsmekanismen (60) aktiveres.

6. Vindturbine ifølge ethvert af de foregående krav, kendetegnet ved, at hovedakslen (19) er forbundet med en gearkasseenhed eller en generator i transmissionen og/eller mindst en af støtteelementerne (43), og at yderrøret (35) omfatter to eller flere sektioner (44, 46), der er placeret i rækkefølge og forbundet med hinanden.

7. Vindturbine ifølge ethvert af de foregående krav, kendetegnet ved, at hovedakslen (19) er lavet af kompositmateriale.

8. Fremgangsmåde til samling af et kabelstøttesystem (22) til en vindturbine ifølge ethvert af de foregående krav, hvor samlingsfremgangsmåden omfatter trinene: - arrangering af et antal elektriske kabler, f.eks. strømkabler eller datakabler, i forhold til mindst et støtteelement (42), - placering af kabelstøttesystemet (22) i et gennemgående hul i en hovedaksel (19), - montering af mindst et første endeelement (37) og et andet endeelement (38) af kabelstøttesystemet (22) på hovedakslen (19), kendetegnet ved, at - de elektriske kabler, f.eks. strømkabler eller datakabler, placeres i et antal optagende delelementer (50) placeret i støtteelementet (43), hvori delelementerne (50) strækker sig i en aksialretning langs kabelstøttesystemet (22).

9. Fremgangsmåde ifølge krav 8, kendetegnet ved, at støtteelementet (43) er yderligere placeret i mindst et yderrør (35), der indeslutter støtteelementet (43) enten før eller efter placering af de elektriske kabler i delelementerne (50) af støtteelementet (43).

10. Fremgangsmåde ifølge krav 8 eller 9, kendetegnet ved, at mindst et midterstøtteelement (43) er placeret i en første position i forhold til mindst et af endeelementerne (37, 38).

11. Fremgangsmåde ifølge ethvert af krav 8 til 10, kendetegnet ved, at positionen af mindst et af endeelementerne (37, 38) eller midterstøtteenhedeme (41) justeres i forhold til en centerakse af hovedakslens (19) gennemgående hul, f.eks. ved at bevæge mindst et bevægeligt element (57) af dette endeelement eller denne midterstøtteenhe-den i en radialretning (58) i forhold til en centerakse af endeelementet eller midterstøt-teenheden.