Patent Publication Number: US-2011062720-A1

Title: Control box for a wind turbine

Description:
The invention relates to a control box to be placed inside a rotor hub of a wind turbine, which can be rotated about a rotational axis. Such control boxes house electrical components such as relays, inverters, sensors and the like within the inner space of the box created by a wall, the said components being required for control of blade adjustment systems, also known as pitch systems. The electrical, hydraulic or mechanical pitch systems turn the turbine rotor blades about their longitudinal axis. 
     Control boxes of the kind mentioned in the introduction are well known in the current state-of-the-art of technology and are used to control pitch control drives in wind turbines and will be referred to as pitch control boxes in the following text. Regulating the temperature of the pitch control boxes is problematic when high power exists in the circuit and high power losses take place within the control box simultaneously while the ambient temperature in rotor hub is high at times, since the heat dissipation through the surface of the control box is itself not sufficient. Based on the heat dissipation of the control box components, the control boxes are cooled passively or actively. A passively cooled control box can be constructed to be hermetically isolated from the environment. In general, an active cooling requires a cooling medium to exchange the heat between the interior of the control box to be cooled and a cooler external environment. Very often this cooling is accomplished by using fans to provide a targeted and forced blast of atmospheric air. In this process the safety class requirements are met by protecting the air inlets and outlets by means of grids and/or filters. 
     In general, after component assembly and commissioning, the control boxes are opened only for their periodical maintenance. In case of any operational problems, it may be necessary to carry out an unplanned maintenance work. 
     Spurious particles can find their way into the control box in the course of maintenance or even via air inlets and outlets. In such a case, especially dangerous are the electro-conductive spurious particles that can trigger a short circuit (wires, cable parts, washers, screws etc.) and mechanically relevant bodies that can choke objects like fans, for example. Due to the constant rotation of the entire system, there is a high degree of hazard of component damage caused by the freely moving spurious particles, since these particles are kept in constant motion due to rotation and can certainly lead to problems. 
     Moreover, in the current state-of-the-art there are wind turbines known wherein magnets are provided in the control boxes in the rotor hub, and as a result ferro-magnetic spurious particles can be held firmly inside the control box. This process, where magnets are used, suffers from the drawback that they can capture exclusively spurious magnetic particles and moreover it has a low capacity to collect such particles. This means that the captured spurious particles significantly reduce the capacity of a capturing device of the state-of-the-art to capture any other particles. For example, any spurious particles of aluminum or austenitic alloys cannot be captured. Such particles, which also are electrically conductive, can lead to short-circuits within the control box or to mechanical destructions. 
     The objective of the invention is to provide a control box for a wind turbine, whereby the drawbacks of the current state of the art can be avoided. 
     This should especially enhance the fault tolerance of the control boxes, by restraining the electrical or mechanical defects caused by the spurious particles. 
     The invention achieves the objective through the features given in the main claim  1 , wherein the catching device in the control box has a cavity for receiving spurious particles and an opening for spurious particles to get into the cavity. This causes the spurious particles to be collected by the catching device only by means of gravity and the rotation of the rotor hub. Furthermore, the cavity ensures that the spurious particles caught are held within the catching device. 
     A first embodiment reveals that the opening is essentially facing the main direction of rotation. To illustrate this it should be stated that such a cross-section or area is considered as the opening which describes the transition between the inner space of the control box and the cavity of the catching device. Firstly this cross section or area should not be designed to be a level surface and it does not correspond to the smallest cross-sectional area between the catching device and the inner space. The orientation of this opening should be defined from the point of its effectiveness in capturing the spurious particles. Now if the opening is facing the main direction of rotation, then during the transition from the inner space of the control box into the cavity of the catching device a spurious particle performs a movement that is essentially a tangential movement against the main direction of rotation with respect to the rotor axis. As such, the driving movement for the capturing process is predominantly the rotation in conjunction with gravity. The direction of rotation intended for the wind turbine&#39;s operation is considered as the main direction of rotation. 
     Another embodiment reveals that the opening is facing a radial direction inward to the rotor axis of the rotor hub. In such a case, the driving force for the capture process is predominantly the gravitational force in conjunction with the rotation. During the transition from inner space into the capturing direction, the spurious particles perform now essentially a radial movement with reference to the rotor axis. 
     The capturing device can be placed in a radially external, essentially axially located corner of the wall. This placement helps to save space and does not have any negative impact on the placement of the electrical components within the control box. In doing so, the cavity of the capturing device can be advantageously built up using the lateral surfaces of the walls of the control box and a separate limb wall. The opening is provided in the limb wall. 
     It is also possible to think of essentially placing the capturing device in the inner space of the control box, whereby this arrangement is found to be especially favorable if the capturing device is placed in a corner of the control box. 
     In an alternative method the capture device can be placed on a lateral surface of the wall. This is especially advantageous, but it is not restricted to the case when the capture device is essentially arranged outside the control box and at least in some cases the opening is created by a cut out in the wall. 
     One possible layout of the embodiments described above reveals that the capture device includes at least one baffle plate to capture the spurious particle. This serves to capture the spurious particles with ease by enlarging the working surface area of the effective opening. The baffle plate is advantageously placed at the opening itself. 
     Furthermore, the above-mentioned baffle or an additional baffle can be partially provided within the inner space of the capturing device in such a manner that the captured spurious particles are held securely within the inner space. For example, the cavity can be formed at least partially as a trap or labyrinth by dividing and arranging the baffle. The rotation of the rotor hub causes the spurious particles to get deeper and deeper into the capturing device. 
     In order to ensure that the collected spurious particles are not lost, such a magnet or an adhesive element can be provided within the cavity of the capturing device, which is suitable for retaining the magnetic and/or also non-magnetic spurious particles in place. 
     The capturing device also includes an opening for maintenance purposes, which serves to remove the captured spurious particles from the cavity of the capturing unit regularly. 
     The capturing device can extend over the entire depth of the control box or the capturing device is extended by fitting baffles over the entire depth of the box. In this way, it is ensured that the spurious particles do not circulate in the capturing device and that there are no “dead zones” in which spurious particles could get deposited and thus present an unsafe/dangerous situation. 
     The invention also covers a wind turbine with a nacelle mounted on a tower while a rotor is fitted on the nacelle so that it can rotate on it, including a rotor hub and at least one rotor blade fitted on it, whereby at least a control box with a capturing device is placed within the hub as described earlier. 
    
    
     
       The other details of the invention emerge from the drawings in accordance with the descriptive text. In the drawings, 
         FIG. 1  shows a schematic cross-section through a rotor hub of a wind turbine, 
         FIG. 2   a  schematic control box with a capturing device, 
         FIG. 3   a ) shows a schematic control box with three design versions of a capturing device ( b - d ), 
         FIG. 4   a )- f ) the process of capturing the spurious particles in the control box according to  FIG. 3   a ) and  b ), 
         FIG. 5   a - c  embodiments of a capturing device in various views, 
         FIG. 6   a ) a schematic control box with three embodiments of a capturing device ( b - d ), 
         FIG. 7   a ) a schematic control box with three embodiments of a capturing device ( b - d ), and 
         FIG. 8   a ) a schematic control box with two embodiments of a capturing device ( b - c ). 
     
    
    
     The view represented in  FIG. 1  shows a rotor  11  and the nacelle  8  of a wind turbine  6 . The rotor  11  includes the rotor hub  12 , rotor blades  13  and a rotor shaft  14 , which is mounted on a bearing to be able to rotate about the rotor axis of the nacelle  8 . The nacelle  8  is mounted on a tower  7 , so that it can be rotated for wind tracking. A rotor hub  12  with adjustable rotor blades  13  is shown in the figure. The rotor blades  13  are mounted in a blade bearing  18 , so that they can be rotated and adjusted about the rotor blade axis  21 . 
     Within the rotor hub  12 , each of the rotor blades  13  can be driven via an electric motor  16  and a gear box  17  (as shown in the example) to enable them to rotate. Alternatively, one drive can be used for several rotor blades or several drives for one rotor blade. These alternatives are not shown. Likewise, it is also possible to use other types of drives (such as hydraulic systems, for instance) rather than a combination of motor and gear box. 
     According to  FIG. 1  the electrical motors  16  are controlled from a main control box  1 . Optionally, several distributed control boxes too can be used instead of a single main control box  1 . In an emergency due to voltage drop, the motors  16  are supplied through an electrical energy storage device and this allows the rotor blades  13  to be positioned reliably. Various accumulator types and condensers are known to be used as electrical energy storage devices. All control boxes  1  for components, such as control devices and electrical energy storage unit for back-up systems, are equipped with capturing devices  30 ,  40 ,  50  or  60 . These devices absorb all the spurious particles  19  that are found within the control box and retain them. In this manner, the danger of an interruption or a defect triggered by the conductive spurious particles  19  or mechanical choking caused by spurious particles  19  is minimized. 
     A schematic representation of the control box  1  fitted with a capturing device  30 ,  40 ,  50  or  60  as per the invention is depicted in  FIG. 2 . The capturing device  30 ,  40 ,  50  or  60  consists of a box, which produces a cavity  32 ,  42 ,  52  or  62  and has an opening  33 ,  43 ,  53  or  63  and extends over the entire depth of the control box. The capturing device  30 ,  40 ,  50  or  60  is formed according to the design geometries and their shapes shown in  FIG. 3 ,  5 ,  6 ,  7  or  FIG. 8 , whereby their size is proportional to the size of the control box. 
     In  FIG. 3   a , a control box  1  is shown as per  FIG. 2 , whereby  FIG. 3   b  to  FIG. 3   d  reveals three usable designs of the capturing device  30 . Each of the capturing devices  30  can be mounted in an axial corner  9  in the inner space  3  of the control box  1 . The capturing unit  30 , as per  FIG. 3   b , has a wall  31  that creates the cavity  32  and an opening  33 , whereby the opening  33  faces the main direction of rotation  9 . At the opening  33  a baffle  34  is provided, which produces a labyrinth  36  within the capturing device  30 . 
     As an example, the process of capturing the spurious particles  19  by the capturing device as per  FIG. 3   a  can be illustrated with the help of  FIG. 4 . The same principle holds good for the other embodiments of capturing devices  40 ,  50 ,  60  too. In  FIG. 4   a , spurious particles  19  are found in a free state in the inner space  3  of the control box  1  and therefore they are in a position to cause destructions within the control box  1 . The gravitational force  20  (represented here by arrow  20 ) causes the spurious particles  19  to move towards the bottom and to deposit on a lateral surface  5  of the wall  2  ( FIG. 4   b ). If the control box  1  rotates further ( FIG. 4   c ), then, driven by gravity, the spurious particles  19  slip through the opening  33  of the capturing device  30 . 
     The spiral shaped baffle  34  conveys the spurious particles  19  deeper into the labyrinth  36  ( FIG. 4   d, e ). In  FIG. 4   f , the control box  1  is found in the initial position in accordance with  FIG. 4   a . In such case, the spurious particles  19  are present in the cavity of the capturing device  30 , as a result of the rotation, the shape of the capturing device  30  and that of the baffles  34 . Moreover, the spurious particles  19  are prevented from going back to the inner space of the control box  1 . 
     The capturing devices  30 , as per  FIG. 3   c  and  FIG. 3   d , have baffles  34 ,  35 ,  34 ′,  35 ′ designed to have another shape, but the principle of capture of the spurious particles  19  is maintained as same. The twisted baffles  34 ,  34 ′,  35  allow an improved process of collecting the particles, whereby the second baffle  35 ,  35 ′ also guarantees holding the captured spurious particles  19  in place, if the rotor hub  12  should rotate against the main direction of rotation  9 . 
       FIG. 5   a  shows an improved embodiment of the capturing device  30  according to  FIG. 3   b . The opening  33  is placed in the main direction of rotation  9  of the control box  1  or that of the rotor hub  12  and thus it accepts the free moving spurious particles  19 . In this process the spurious particles  19  are guided to the opening  33  by a baffle  34 . The baffle  34  is folded inwards to the interior in a spiral shape, so that the spurious particles  19  are prevented from going out. If necessary, an adhesive element  37 , preferably a permanent magnet or any other temperature and aging resistant adhesive element, can ensure, in addition, that the spurious particles  19  are brought to a form and remain intact until maintenance. Additionally, the lip edge  38  prevents the captured spurious particles  19  from escaping from the capturing device  30 . 
       FIG. 5   b  and  FIG. 5   c  show other embodiments of the capturing device  30  in accordance with  FIG. 3   c  or  FIG. 3   d . Here the openings  33  are placed in the centre. Over and above this, in  FIG. 5   c , not only the upper and lower baffles  34 ,  34 ′,  35 ′,  34 ″  35 ″ are folded inwards in a spiral shape, but also baffles  34 ,  34 ′,  35 ′,  34 ″,  35 ′, which are formed inwards in spiral shape, are placed on the right and left of the opening  33 . 
     The design shapes of the capturing devices  40  from  FIG. 6  are placed at a corner  4 , outside of the control box  1 . This enables the control box  1  to accommodate more components. A cut out in a side surface  5  of wall  2  of control box  1  serves as the opening between the inner space  3  of the control box  1  in the cavity  42  of the capturing device  40 . The capturing devices  30 , as per  FIG. 6   a  and  FIG. 5   b,  are in a position to collect the spurious particles  19  independent of the main direction of rotation  9  from the inner space  3  of the box. The capturing device  30  in  FIG. 6   c  and  FIG. 6   d  shows a labyrinth-like feature of the baffles  45 ′  44 ′,  44 ″. 
       FIG. 7  shows a control box  1  in which a embodiment of the capturing device  50  is placed in the corner  4  according to the three design arrangements ( FIGS. 7   b  -  7   d ). Unlike the previous cases, the cavity  53  of capturing device  50  is created by two or three lateral surfaces  5  of the wall  2  of the control box  1  and by a limb wall  57 . In this way, it is possible to produce the capturing device  50  with advantages and to save space. The capturing devices  50  as per  FIG. 7   b  and  c  show a baffle at the opening  53 , which firstly is projecting into the interior  3  of the control box  1 , and as such serves to capture the spurious particles better. Secondly, the baffle  54 ,  54 ′ produces a labyrinth-like construction in cavity  52 . As a result, the spurious particles  19  are held firmly within the capturing device  1 . 
     Similar to the design in  FIG. 6 , the capturing devices  60  as per  FIG. 8   b  and  c  are fitted outside the control box  1 , however on a lateral surface  5  of the wall  2 . The capturing device  60 , as per  FIG. 8   c , is in a position to collect the spurious particles  19  from the inner space  3  independent of the direction of rotation  9 . 
     The application of the combination of features depicted in the embodiment examples should not be restricted only to the invention itself; rather it should also be possible to combine the features of different versions with one another. 
     LIST OF REFERENCES 
     
         
         
           
               1  Control box 
               2  Wall 
               3  Inner space 
               4  Corner 
               5  Lateral surface 
               6  Wind turbine 
               7  Tower 
               8  Nacelle 
               9  Main direction of rotation 
               10  Rotor axis 
               11  Rotor 
               12  Rotor hub 
               13  Rotor plate 
               14  Rotor shaft 
               15  Direction of rotation 
               16  Electrical motor 
               17  Gear box 
               18  Blade bearing 
               19  Spurious particles 
               20  Gravity 
               21  Rotor blade axis 
               30  Capturing device 
               31  Wall 
               32  Cavity 
               33  Opening 
               34  Baffle 
               35  Baffle 
               36  Labyrinth 
               37  Adhesive element 
               38  Lip 
               40  Capturing device 
               41  Wall 
               42  Cavity 
               43  Opening 
               44  Baffle 
               45  Baffle 
               46  Labyrinth 
               50  Capturing device 
               51  Wall 
               52  Cavity 
               53  Opening 
               54  Baffle 
               55  Baffle 
               56  Labyrinth 
               57  Limb wall 
               60  Capturing device 
               61  Wall 
               62  Cavity 
               63  Opening 
               64  Baffle 
               65  Baffle 
               66  Labyrinth 
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