The invention relates to wind turbine with an integrated segmented permanent magnet generator, according to the preamble of claim 1.

BACKGROUND

The use of wind turbines to produce electricity from wind is one of several methods to utilize renewable energy sources. Wind turbines with a geared transmission between the turbine rotor and the generator have so far been the dominating driveline layout for wind turbines, but with a high risk for mechanical breakdown and unnecessary driveline complexity. In addition a gear based driveline needs extra control and maintenance even if there is no driveline breakdown.

To overcome these challenges a direct drive wind turbine is preferable due to its simpler design with few moving components and high reliability, no risk for gearbox breakdown and lower maintenance budgets compared to geared wind turbines. Using permanent magnets instead of traditionally electromagnets in the rotor of the generator add another simplification to the design.

So far the main challenge has been to construct direct drive wind turbines to the same cost level as for geared wind turbines with comparable power output, and with the same flexibility for road transport and site installation.. Especially the manufacturing costs of large direct drive generators and the extra costs for the transportation and their field installation due to the physical size and weight have threatened the all over installation costs of direct drive wind turbines compared to geared wind turbines in spite of their other attractive properties in a lifetime perspective.

Several configurations already exist for direct-drive wind turbines:

US2004041407A to Pettersen & al. describes a solution where a direct drive permanent magnet generator is fixed to the wind turbine shaft where only small external forces from the wind turbine shaft is acting on the generator, except for the varying shaft torque giving no deformation forces around the air gap of the generator. But the generator is a traditional permanent magnet generator with end covers, bearings and shaft, and impractical to transport and install in separate pieces, even if the stator is segmented.

Publication US 2007284959A to Kurronen & al. describes the stator segments, but they are built to be positioned between generator end covers.

Publication No. WO 02/057624 to Wobben is concerning how a double tapered bearing can be fixed to a hollow stationary shaft carrying the blades, hub, and generator rotor and stator with carrier to maintain a constant air gap between the stator and rotor in a traditionally electro magnetized generator. No details regarding segmentation of the turbine is described. Nothing is said about how this can be realized with a permanent magnet rotor technology where rotor and stator segments are already positioned to each other as road transportable and lifting elements to be assembled individually to a bearing system and a stator carrier to form a complete generator.

Publication No. WO 01/21956 to Lagerwey discloses another single-bearing, direct drive wind turbine, but the stator and permanent magnet rotor is not segmented and are road transported into the field as a complete generator with a bearing system in one piece limiting this design in power size.

Publication No. US 2009/0026771 Al to Bevington & al. describes one way of making a direct drive generator for wind turbines, but says nothing about how the generator can be built up from segments to reduce manufacturing, transport and handling challenges along with how to scale the generator in electrical size and diameter.

Object

The main object of the invention is to provide a wind turbine which overcomes the mentioned obstacles. It is further an object of the invention to provide a wind turbine which reaches the installation costs for geared wind turbines in combination with the much more favourable risk profile and maintenance costs compared to geared wind turbines.

It is an object of the invention to provide a wind turbine in parts/segments making it possible to integrate generator segments to a wind turbine rotor with bearings independent from the wind turbine itself.

It is further an object of the invention to provide a wind turbine which generator can be assembled before mounting and with no need for repositioning the air gap.

It is finally an object of the invention that a complete generator formed by generator segments arranged to a bearing unit can be arranged to a wind turbine support structure as a complete unit, and where the stator can be connected directly to the wind turbine support structure and the wind turbine rotor, hub and blades can be connected directly to the rotating part of the bearing unit without any shaft.

The invention

A wind turbine according to the invention is described in claim 1. Advantageous features of the wind turbine are described in claims 2-15.

The invention discloses how to integrate a permanent magnet generator having close to horizontal rotating axis from separately manufactured generator segments, and how to connect the segments to a bearing unit to form a complete generator with bearings to be arranged to a support structure of a wind turbine, without any need for repositioning the air gap of the generator after final assembly. The generator is formed by generator stator and rotor segments. The generator stator segments preferably include a cantilevered stator housing which is adapted to be arranged to one side of the periphery of the bearing unit. Inside the cantilevered stator housing different solutions for the stator windings divided into segments can be arranged. The rotor segments preferably include magnet supports for the fixation of magnets. The rotor segments with magnets in place are positioned with special tools to the right air gap relative to the stator windings inside each generator stator segment, and the generator stator segments and generator rotor segments are locked relative to each other by a preliminary locking system.

Assembled together around the periphery of the bearing unit these separate components form a complete ring generator with a generator rotor rotating with the right air gap inside the cantilevered generator stator. This makes it possible to assemble the entire generator before it is fixed to the wind turbine support structure and to a wind turbine rotor.

The invention also includes a combined inching, braking and locking device which can be arranged to the rotary part of the bearing unit. The combination device makes it possible to exactly position the wind turbine rotor in any position when in great unbalance, such as under individual blade installation, and makes it possible to exactly position the generator rotor in any position for inspection and maintenance.

Further advantages and preferable features of the invention will appear from the following example description.

Example

The invention will now be described in detail with references to the attached drawings, where:

Figure 1 shows a complete generator fixed to a wind turbine support structure, while a hub is fixed to a rotating part of a bearing unit,

Figure 2 shows a typical generator segment with generator stator and rotor positioned to each other before assembly to a complete generator,

Figure 3 shows a perspective view of a wind turbine bearing unit,

Figure 4 shows how the generator stator and rotor segments assembled to the bearing unit before the complete generator, inclusive the wind turbine bearing unit, is lifted up for fixation to a wind turbine support structure on top of a tower,

Figure 5 shows a device for inching, braking and locking the rotor, and

Figure 6 shows an example of a hydraulic jig for adding a stator segment into a rotor segment. Reference is now made to Figure 1 which shows an upper part of a wind turbine 10 according to the invention, where a generator 11 built up by generator segments 12 (see Figures 2 and 4), is arranged to a wind turbine support structure 13, and a hub 14 is arranged to a rotating part of a bearing unit 30 (see Figure 3) via a wind turbine rotor 15. No wind turbine blades are shown arranged to hub 14 to provide a better view of the invention. The tower is neither shown, as this can be realized in different ways, such as steel tubular tower, concrete tower, lattice tower, or combination of these.

Reference is now made to Figure 2 which shows a perspective view of a generator segment 12 of a generator 11 containing both generator stator 16' (hereinafter called stator) and rotor 17' (hereinafter called rotor) segments of the generator 11. The stator 16' segments are assembled to form a complete generator stator 16 and the rotor 17' segments are assembled to form a complete generator rotor 17. The stator segments 16' preferably include a cantilevered stator housing 18 at the outer periphery. The stator segments 16' are further at the inner periphery provided with a flange 19, via which the stator segments 16' are arranged to the wind turbine support structure 13. The rotor segments 17' are provided with a flange 20, via which the hub 14 and the wind turbine rotor 15 are attached to the generator rotor 17. The generator 11, can based on the main principals of the present invention, also be realised with the rotor 17 placed outside of the stator 16 forming a generator with the outer periphery rotating.

As mentioned the stator segments 16' includes a stator housing 18 which is such designed that different winding solutions 21 can be chosen and fixed to the stator segments 16'.

The same apply to the outer periphery of the rotor segments 17' where different fixations of permanent magnets 22 may be applied by means of magnet supports 23. The stator housing 18, stator windings 21, as well as the magnets 22 and magnet supports 23 may be segmented in an appropriate number depending of generator size and practical ways for manufacturing, transport and assembly to form one complete generator.

The exterior of the stator housing 18 can be provided with different cooling solutions for the stator winding, i.e. cooling ribs for direct air cooling, water jacket for combination with water to air heat exchangers, special shrouds for increased air circulation around the cooling ribs with the help of fans or similar.

In addition to being fixed to the static and rotating parts of the wind turbine at flanges 19 and 20, both the stator 16' and rotor 17' segments are fixed, for example by bolting, individually to each other at the ends 24. The connections should be carried out in a way so that the tolerances of the construction can be adapted.

The radial position of an air gap 25 and the width of the same air gap 25 may vary depending of the electrical size of the generator 11 and the rpm rating. The same apply to the diameters of the flanges 19 and 20 that may vary depending on the size of the generator 11 and the bearing solution of the wind turbine 10.

The rotor segments 17' with permanent magnets 22 installed are positioned into the stator segments 16' after fabrication and kept in position to each other with a positioning device 26 until both the stator 16' and rotor 17' segments are integrated to a complete generator 11 on the bearing unit 30 and the support structure 13 by means of an assembly tool.

The rotor segments 17' can be manufactured and assembled in a way such that sufficient tolerances are achieved from the manufacturing process itself for positioning of the rotor and stator flange. This can be carried out using, for instance, a hydraulic tool where the rotor is put into the stator, or the other way around, either radially, axially or rotationally. Another option is to place the rotor and stator together using temporary brackets that allow adjustment of the segments after assembly. Figure 6 shows an example of a hydraulic jig 46 made for adding the stator segment (inner) 17 into the rotor segment (outer) 16, axially and positioned with high tolerances.

Reference is now made to Figure 3 which shows a perspective view of the wind turbine bearing unit 30 which can involve several types of bearings inside. The bearing unit 30 can be a double row tapered bearing, different types of conical bearings or slide bearings. The bearing unit is assembled in a controlled environment with the right positioning between stationary and rotating parts, where only the fixation of the stator and the rotor part of the generator is left for field assembly to form a complete generator with bearings. The bearing unit includes a rotating part 31 and a stationary part 32. The rotary part 31 is provided with a flange 33 at the outer circumference and the stationary part 32 is provided with a flange 34 at the outer circumference.

To assemble the generator segments 15 to a complete generator 11, the segments 15 are attached to the bearing unit 30 at the flange 33 for the stator segments 16', and at flange 34 for the rotor segments 17'. The segments 15 can either be positioned radially or axially on the bearing unit 30 depending on the flange diameters.

Reference is now made to Figure 4 which shows the generator 11 when one stator 16' and rotor 17' segment are still missing on the bearing unit 30. The number of both stator 16' and rotor 17' segments may vary in numbers from two or more depending on manufacturing and

electrotechnical considerations.

After the integration of the complete generator 11 to the bearing unit 30, the stator 16 to rotor 17 positioning device 26 can be removed, and the generator rotor 17 is free to rotate inside the generator stator 16, and to be lifted in one piece for fixation to the wind turbine support structure 13 without any specific tolerance need for positioning to the wind turbine support structure to maintain the right air gap 25 Reference is now made to Figure 5 which shows a device 40 for inching, braking and locking of the wind turbine rotor 15 for different purposes, which device 40 is adapted to be arranged between the bearing unit 30 and the wind turbine rotor 15. The device 40 includes a support bracket 41, to which support bracket 41 arranged are locking pins 42 and brake callipers 43. The device 40 also includes one or more inching cylinders 44, in the shown example two, which are supported by the support bracket 41 in one end. To the free moving end of the inching cylinders 44 is arranged a connecting piece 45. The wind turbine rotor 15 is for this provided with a flange 35 provided with holes 36 for the locking pins 41 of the device 40 for normal parking in addition to be a brake disc for the brake callipers 43.

The connecting piece 45 of the inching cylinders 44 are provided with holes and a separate set of locking pins (not shown). The free moving end of the cylinders 44 are connected to the locking holes 36 of the wind turbine rotor 15 by the holes and set of locking pins of the connecting piece 45. When these parts are aligned, the wind turbine rotor 15 is brought to standstill and the brakes are engaged. Engagement of the locking pins of connecting piece 45 can be either manual or automatic.

The cylinders 44 have two functions. One function is to lock one or both cylinders 44 to the wind turbine rotor 15 under severe weather conditions or wind turbine rotor inspections in addition to the locking pins 42. The other function is when inching the wind turbine rotor 15 under for instance installation of each wind turbine blade individually or in connection with maintenance on all rotating parts. With the normal locking pins 42 not engaged, one cylinder 44 can keep the wind turbine rotor 15 in position, while the other cylinder 44 is positioned to take over the circumferential movement of the wind turbine rotor 15 when the first cylinder 44 has reached its outmost position.

The complete wind turbine can be installed in a variation of ways. One method is to install it in five steps; - First installation of a tower, then installation of the support structure on top of the tower, then installation of the generator inclusive the bearing unit to the support structure, then installation of the rotor, then individual installation of the blades. The blades can either be installed by a crane, where the blades are installed horizontally or by a winching system where the blades are installed vertically. Modifications

Generators of different electrical sizes and rpm can be integrated with the same generator segment method with just varying air gap diameters and lengths and flange diameters for assembly to the bearing unit in different sizes.

The invention can also be used for generators not equipped with permanent magnets, but by other means foV generating electric current.

In the bearing unit shown in the example several types of bearing can also be used, for instance a double row tapered bearing, hydrostatic or hydrodynamic bearing, double conical bearings, or two roller bearings where one of them can take full thrust force from the wind turbine rotor. The magnet support of the rotor segments can be adapted to give the possibility to use different permanent magnet installation methods.

The stator housing can support stator lamination and stator windings of different shapes and electrical properties, and with different redundancy strategies.

An inching system where either the inching can be carried out by linear electric motors or by electric inching by the generator itself

An inching system placed on a larger diameter so fewer brakes can be used.

An inching system where brakes, inching cylinders and locks is separated to three different systems.

A cooling solution for the generator where forced air cooling by fans inside a circumferential shroud is used instead of free air flow over the turbine cooling fins

A cooling solution using either a water jacket outside the stator structure or by an air/liquid heat exchanger, where the generator is cooled by circulating air inside the generator.

Assembly of the generator segments where the segments can be assembled radially or axially, using regular cranes or other lifting methods or by using a custom made jig for the operation

The bearing unit, the generator segments and the hub itself can be made with different material solutions, for instance welded steel, casted steel, forged steel, or by other material such as fibre glass or other fibre resins

Installation of the turbine where the turbine is assembled from the main components on ground and lifted by crane as a whole unit

Installation of the turbine on a sliding lift on the tower, for instance on a concrete tower

The stator can be double supported with an extra support bearing connecting an end cover on the generator with the rotating part 15. By this, neither the rotor nor the stator will be

cantilevered.

The generator may have the rotor outside or inside the stator, also changing which of the components that are cantilevered. The generator stator can be connected directly to the support structure, while the static part of the bearing unit can be connected to the generator stator, or vice versa.

The generator is equipped with a retaining device, for instance made of bronze or other low friction material, so that excessive deformations in the generator air-gap is not harming the generator itself.