Abstract:
A synchronous generator, in particular a multipole synchronous annular generator of a direct-drive wind turbine, for generating electricity, with a rotor and a stator, wherein the stator has multiple grooves in which a stator winding is arranged, wherein the stator winding releases heat energy as a result of the generation of power, and wherein a cooling body for absorbing and dissipating released heat energy is arranged in one groove, multiple grooves or all of the grooves.

Description:
BACKGROUND 
     Technical Field 
       [0001]    The present invention relates to a synchronous generator, in particular a multipole synchronous annular generator of a direct-drive wind turbine. The present invention moreover relates to a wind turbine having such a synchronous generator. 
       Description of the Related Art 
       [0002]    In the priority-establishing German application, a search made by the German Patent and Trademark Office identified the following documents: EP 2 752 578 A1, CH 357 797 A and DE 102 44 202 A1. 
         [0003]    Wind turbines are generally known. They generate electricity from the wind by means of a generator. Modern direct-drive wind turbines often comprise a multipole synchronous annular generator with a large air gap diameter. The diameter of the air gap is hereby at least four meters and usually is as great as almost five meters. It is absolutely possible for synchronous generators composed of multiple parts to have air gap diameters in the region of ten meters or more. 
         [0004]    The efficiency of the synchronous generator has a significant effect on the efficiency of the whole wind turbine when generating power. In order to achieve the highest possible degree of efficiency when generating power, it is therefore important for the stator winding to have an optimum design. This also includes in particular accommodating the highest possible number of bundles of wire in the stator winding. 
         [0005]    The greater the thickness of the material of the stator winding, and the greater the induced field of the synchronous generator, the greater the amount of heat generated in the stator winding. It is inevitable that the stator winding and the stator ring of the synchronous generator are heated during operation. It is essential to prevent predetermined temperature limits from being exceeded in order to obviate, for example, impairment of the degree of efficiency or mechanical problems caused by the generation of heat and its transmission to adjoining components. 
         [0006]    The generator, in particular the stator ring, accordingly needs to be cooled. 
         [0007]    The cooling of the stator ring by means of external cooling means arranged at the circumference of the stator ring is, for example, known from the prior art. 
         [0008]    Although this cooling method has been proven to be essentially reliable in practice, there is a requirement to improve the achievable cooling capacity at the synchronous generator of the wind turbine, and in particular at the stator ring. 
       BRIEF SUMMARY 
       [0009]    A synchronous generator is proposed in particular which has a rotor and a stator, wherein the stator has multiple grooves in which a stator winding is arranged, wherein the stator winding releases heat energy as a result of the generation of power, and wherein a cooling body for absorbing and dissipating released heat energy is arranged in one groove, multiple grooves or all the grooves. 
         [0010]    In the case of a synchronous annular generator of a direct-drive wind turbine, “multipole” is understood to mean multiple stator poles, in particular a design with at least 48 stator teeth, often even with considerably more stator teeth such as in particular 96 stator teeth or even more stator teeth. The magnetically active area of the generator, namely both the rotor and the stator, is arranged in an annular area about the axis of rotation of the synchronous generator. Thus in particular an area of 0 to at least 50 percent of the radius of the air gap contains no materials which conduct electricity or electrical field from the synchronous generator. In particular, this internal space is completely unobstructed and it is also in principle possible for staff to walk around within it. This area is often also more than 0 to 50 percent of the air gap radius, in particular up to 0 to 70 percent or even 0 to 80 percent of the air gap radius. Depending on the design, a support structure can be present in this inner area but in some embodiments it can be designed with an axial offset. Depending on their function, such synchronous generators of a direct-drive wind turbine are slowly rotating generators. Slowly rotating is here understood to mean, depending on the size of the turbine, a speed of less than 40 revolutions per minute, in particular between 4 and 35 revolutions per minute. 
         [0011]    Optimum heat dissipation succeeds in the heat being absorbed directly where it is generated. In the present case, when electricity is generated in the synchronous generator, the heat is released in the stator windings. Absorbing the released heat occurs at a place which is as close as possible to the stator windings. In the past the fitting of a cooling body inside the groove which holds the stator winding was never taken into consideration because it contradicted the primary approach of providing as many bundles of wires as possible in a groove or the greatest possible packing density of the stator winding in the groove. 
         [0012]    It has been proven that the presumed impairment of the generator efficiency owing to the “omission” of windings in favor of a cooling channel is compensated by the increased efficiency of a winding which is then cooler. 
         [0013]    In an advantageous development, the cooling body has at least one winding contact surface which is in contact with the stator winding. The greater the winding contact surface, the greater too the transmission of heat between the stator winding and the cooling body. 
         [0014]    The cooling body preferably has at least one wall contact surface which is contact with a groove wall. According to this preferred embodiment, by means of the cooling body it is additionally possible to actively cool the stator ring. It is also the case, with respect to the wall contact surface, that the amount of heat transmitted from the stator ring into the cooling body is greater the larger the wall contact surface. 
         [0015]    In a preferred embodiment, the cooling body has a hollow body which is fluidically connected to a cooling medium circuit, wherein the hollow body has a wall with an inner and an outer side. 
         [0016]    The cooling body preferably has a first wall contact surface, in contact with a first groove wall, and a second wall contact surface, in contact with a second groove wall opposite the first groove wall. The cooling body thus extends like a bridge completely from one groove wall to the next groove wall. In this embodiment, the cooling body preferably has not only two wall contact surfaces but also two winding contact surfaces, wherein the second winding contact surface is arranged on a side of the cooling body which is opposite the first winding contact surface. 
         [0017]    In a preferred embodiment, the wall contact surface is formed at least partially by the outer side of the wall of the hollow body. Alternatively or additionally, the winding contact surface is formed at least partially by the outer side of the wall of the hollow body. These embodiments allow a structurally simple design of the hollow body. 
         [0018]    In a further preferred embodiment, the cooling body has one or more projections which extend from the wall of the hollow body along the groove walls and have an outer side facing the respective groove wall, as well as an opposite inner side adjoining the stator winding. The wall contact surface is preferably formed at least partially by the outer side of the projections and the winding contact surface is formed at least partially by the inner side of the projections. 
         [0019]    In a further preferred embodiment of the synchronous generator, the inner side of the wall of the hollow body has one or more cooling ribs. Owing to the enlarged contact surface between the cooling medium and hollow body, the cooling ribs generate a greater heat transfer to the cooling medium in comparison with the surface of the hollow body provided with ribs. 
         [0020]    The hollow body can extend between the groove walls in the manner of a rectangle but can also have a surface which is enlarged in comparison with the rectangular shape, viewed from one groove wall towards the opposite groove wall. The hollow body preferably has a waisted design, or a bulge, in the radial direction of the groove. A waisted design is hereby understood to mean both a concave constriction and also an “angular” indentation with unrounded edges between surfaces. The same also applies, the other way round, for a bulge. Bulge is understood to mean both a convex curvature and an “angular” series of surfaces with no rounded edges. Such “angularly” bulging hollow bodies have an essentially polygonal shape in cross-section. 
         [0021]    In a further aspect, a wind turbine, in particular a direct-drive wind turbine with a synchronous generator for generating electricity which is in particular designed as a multipole synchronous generator is provided. 
         [0022]    Reference should be made to the above embodiments of the synchronous generator with respect to the advantages of the wind turbine. 
         [0023]    In a still further aspect, is provided the use of a cooling body for absorbing and dissipating released heat energy. The cooling body is used to absorb and dissipate heat energy released from a stator winding of a synchronous generator according to one of the preferred embodiments described herein, wherein the cooling body is arranged in a groove of the synchronous generator. 
         [0024]    The cooling body is preferably designed with the features of the cooling body of the abovedescribed synchronous generator. In this regard reference should also be made to the above embodiments of the synchronous generator according to the invention with respect to the advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0025]    The invention is described below with reference to the attached drawings with the aid of multiple preferred exemplary embodiments. Identical or functionally similar features are hereby provided with identical reference numerals. 
           [0026]    In the drawings: 
           [0027]      FIG. 1  shows a wind turbine schematically in a perspective view, 
           [0028]      FIG. 2  shows a nacelle of the wind turbine according to  FIG. 1  schematically in a perspective view in section, 
           [0029]      FIG. 3  shows a simplified schematic perspective view of a stator of the wind turbine according to  FIGS. 1 and 2 , 
           [0030]      FIG. 4  shows a partial view in section through the stator according to  FIG. 3 , and 
           [0031]      FIGS. 4 a - e    show different embodiments of a cooling body for use in a stator according to  FIGS. 3 and 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  shows a wind turbine  100  with a tower  102  and a nacelle  104 . A rotor  106  with three rotor blades  108  and a spinner  110  is arranged on the nacelle  104 . In operation, the rotor  106  is set in rotational movement by the wind and consequently drives a generator  1  ( FIG. 2 ) in the nacelle  104 . 
         [0033]    The nacelle  104  is shown in  FIG. 2 . The nacelle  104  is mounted rotatably on the tower  102  and driven in a generally known manner by means of an azimuthal drive  7 . In a further generally known manner, a machine frame  9 , which holds a synchronous generator  1 , is arranged in the nacelle  104 . The synchronous generator  1  is designed and in particular is a slowly rotating, multipole synchronous annular generator. The synchronous generator  1  has a stator  3  and a rotor  5  which rotates inside it. The rotor  5  is connected to a rotor hub  13  which transmits the rotational movement of the rotor blades  108  caused by the wind to the synchronous generator  1 . 
         [0034]      FIG. 3  shows the stator  3  on its own. The stator  3  has a stator ring  16  with an internal circumferential area  18 . Multiple grooves  17  are provided in the internal circumferential area  18  which are designed to receive the stator winding in the form of bundles of wires. 
         [0035]      FIG. 4  shows a view in cross-section through a groove  17  of the stator ring  16 . The groove extends in an essentially radial direction along a groove axis  21 . The groove  17  has a first groove wall  19   a  and a second groove wall  19   b  opposite the first groove wall. 
         [0036]    Different embodiments of a cooling body  25   a - e  for the synchronous generator  1 , each arranged in one of the grooves  17 , are shown in  FIGS. 4 a   - e.    
         [0037]    The cooling body  25   a  shown in  FIG. 4 a    is, as is apparent from its external contour, designed essentially in the shape of a curved x. The cooling body  25   a  has a first ending contact surface  31   a  and a second winding contact surface  31   b  which are in contact with a stator winding  23 . This also applies for the winding contact surface  31   a,b  of the cooling body  25   b - e  from  FIGS. 4 b - e    in which, however, the stator winding  23  has not been shown for greater clarity. 
         [0038]    The cooling body  25   a  also has a first wall contact surface  33   a  and a second wall contact surface  33   b  which each extend along the groove walls  19   a+b  and bear against them. According to  FIG. 4   a,  the wall contact surfaces  33   a,b  are formed partially by the outer side of the wall of the hollow body  27   a.  According to  FIG. 4   a,  the cooling body  25   a  also has multiple projections  29   a,  one of which is provided with a reference numeral for the sake of clarity. The projections extend from the wall of the hollow body  27   a  along the groove walls  19   a,b.  An outer side of the projections  29   a  also forms part of the wall contact surface  33   a,b,  whilst an inner side of the projections  29   a  in each case forms part of the winding contact surface  31   a,b  of the cooling body  25   a.  The total surface area of the cooling body  25   a  is increased as a result. 
         [0039]    The inner side of the wall of the hollow body  27   a  has multiple cooling ribs  35   a,b  which each serve to increase the surface area of the wall of the hollow body  27   a.    
         [0040]    The hollow body  25   a  has a waisted design or has concave constrictions on both sides in the direction of the groove  17  or in the direction of the groove axis  21 . 
         [0041]    The cooling body  25   b  shown in  FIG. 4 b    is structurally similar to the cooling head  25   a  from  FIG. 4 a    in as much as it has a hollow body  27   b  and multiple projections  29   b  extending from the hollow body  27   b,  wherein the wall contact surface  33   a,b  is in each case formed partially by the outer side of the wall of the hollow body  27   b  and by the outer side of the projections  29   b.  The winding contact surface is likewise partially formed by the outer side of the wall of the hollow body  27   b  and by the inner sides of the projections  29   b.    
         [0042]    In contrast to the cooling body  25   a,  the hollow body  27   b  of the cooling body  25   b  is designed as an essentially cylindrical tube on the outside of which the projections are arranged tangentially. The hollow body  27   b  has a bulbous shape in the direction of the grove axis  21 , i.e., thus has a bulge. 
         [0043]    The cooling body  25   c  from  FIG. 4 c    is formed with an essentially oval cross-section and has, at the sides facing the groove walls  19   a,b,  an uncurved outer wall portion which bears against the groove walls  19   a,b  and forms the wall contact surfaces  33   a,b  of the cooling body  25   c.  In contrast to  FIGS. 4   a,b,  the cooling body  25   c  does not have any projections. However, like the cooling body  25   b  according to  FIG. 4   b,  it has a bulbous shape in the radial direction or in the direction of the groove axis  21 , and thus has a bulge or is bulged convexly on both sides. 
         [0044]    The cooling body  25   d  shown in  FIG. 4 d    has a hollow body  27   d  which has an essentially rectangular profile in cross-section. The winding contact surfaces  31   a,b  extend essentially over the shortest distance from one groove wall  19   a  to the opposite groove wall  19   b,  from where in each case the wall contact surface  33   a,b,  in the form of the outer side of the wall of the hollow body  27   d,  extends along the groove walls  19   a,b.    
         [0045]    Indicative cross-sections of winding wires are labelled with the reference numeral  37 . 
         [0046]    The cooling body  27   d  neither has a waisted design nor has a bulbous bulge. 
         [0047]      FIG. 4 e    lastly shows a cooling body  25   e  which, like the cooling bodies  25   c,d  in  FIGS. 4   c,d,  has no projections such that the wall contact surfaces  33   a,b  are formed completely by the outside of the wall of the hollow body  27   e.  The essentially polygonal cross-section of the hollow body  27   e  is constricted in the direction of the arrows  39  which preferably lie on the groove axis  21 , so that a waisted design is formed. The latter can be designed with rounded corners, as in the example shown in  FIG. 4   e,  or alternatively with angular corners so that a double trapezium is formed which has the groove axis  21  as its axis of symmetry. 
         [0048]    Although the cooling bodies  25   c,d,e  are formed with no projections in the exemplary embodiments shown, it is nevertheless within the scope of the invention also to provide these cooling bodies with projections, and it is equally within the scope of the invention to provide cooling bodies which essentially have the same structural design as the cooling bodies  25   a,b  in  FIGS. 4 a,b    but with no projections. 
         [0049]    It is likewise within the scope of the invention that the cooling bodies in  FIGS. 4 b - e    each have one or more cooling ribs on the inside of the wall of the hollow bodies  27   b - e.    
         [0050]    Also within the scope of the invention are cross-sectional profiles in which a first winding contact surface is bulged bulbously and the opposite second winding contact surface is constricted, or alternatively is neither bulged nor constricted. Likewise within the scope of the invention are cross-sectional profiles in which only one winding contact surface is provided with a waisted design, i.e., is pressed inwards in the direction of the inside of the hollow body, whilst the opposite second winding contact surface is designed as straight, i.e., is neither bulged nor waisted. 
         [0051]    Where it is advantageous for the respective application, multiple or all grooves of the stator ring  16  have an identical cooling body  25   a - e  but alternatively different cooling body geometries  25   a - e  are provided for the stator ring  16  for different groups of grooves  17 . 
         [0052]    Other preferred embodiments can be derived from different combinations of the following patent claims.