Abstract:
A wind power installation has a (ring) generator which has a stator in which grooves are provided at the inner or outer periphery in mutually spaced relationship to receive a stator winding. In order to provide a stator having a winding, in which the susceptibility to trouble as a consequence of the high loading on the generator is substantially reduced, the stator winding is wound without interruption continuously throughout.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a wind power installation having a generator which has a stator in which grooves are provided at the inner or outer periphery in mutually spaced relationship to receive a stator winding. Such wind power installations are known and are produced and marketed for example by ENERCON. 
     2. Description of the Related Art 
     A known process for the production of stator windings in generators includes the use of what are referred to as former-wound coils. Those former-wound coils are individual windings of the stator winding, which are already adapted in respect of their form to the grooves and groove spacings of the stator and which are firstly individually inserted into the grooves and then connected together. 
     It will be appreciated however that wind power installations are always exposed to high levels of loading during operation thereof. With an increasing wind speed the power output of the wind power installation increases but at the same time the mechanical loading also rises. That means that the stress on the wind power installation increases substantially simultaneously, from the mechanical and the electrical point of view. At high wind speeds the mechanical stress on the installation is high and at the same time a great deal of electrical power is generated so that the stress on the electrical components is also high. 
     In that situation, the generator of the wind power installation, which is subjected to mechanical and electrical stresses, is particularly stressed. That combination gives rise to problems if for example, as a consequence of high electric currents generated, the temperature in the region of the generator is also high and, as a consequence of mechanical stress, connections between individual components are subjected to the effect of vibration. If thermal expansion also gives rise to a small amount of play or a loosening effect, the mechanical loadings can here result in a defect or even damage. 
     If that trouble involves the stator winding or a phase thereof, at least that phase is out of commission in terms of energy production. Furthermore this involves an additional asymmetrical loading in the generator as, as a consequence of the interruption, that phase acts as in the no-load mode of operation. In that respect mechanical damage due to released and freely movable components such as connecting sleeves is not even taken into consideration. 
     In the case of a stator, wound in six-phase configuration, of a generator with 72 poles, there are 432 former-wound coils which are connected together by 864 connecting locations. Those connecting locations are usually in the form of screw, clamping or solder connections. 
     Having regard to statistical probabilities (of no matter how small magnitude), the high number of connecting locations and the permanent changes in load mean that, even if the connection between the former-wound coils is carefully made, this involves a serious source of trouble. In that respect only one stator is taken into account in the foregoing considerations. The aspect of mass production clearly reveals the actual probability of such a problem occurring. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore one object of the present invention is to provide a stator having a winding, in which the above-discussed problems are substantially reduced. 
     In a wind power installation of the kind set forth in the opening part of this specification, that object is attained by a stator winding which is of a continuous nature throughout. That arrangement avoids in particular the need for a connector between individual portions of a stator winding. 
     In a preferred embodiment of the invention all phases are respectively wound continuously throughout on the stator. 
     In order to be able to compensate for current-displacement effects in the individual turns, the turns are produced from at least two conductor bundles, wherein a plurality of mutually insulated conductors is present in each conductor bundle. Those conductor bundles are introduced into grooves in the stator in a predetermined sequence and the sequence is altered at also predetermined spacings so that each of the conductor bundles is alternately affected as uniformly as possible by those effects. It is possible to forego compensation measures by virtue of that uniform influence in respect of all conductor bundles of a phase. 
     In order to facilitate handling of the stator during production of the winding and to provide a situation which is favorable in work-physiological terms, the stator is kept in a mounting apparatus in which the grooves are at a favorable working height for production of the winding and which permits rotation of the stator in the peripheral direction by a desired amount. This can preferably be effected using a motor drive. 
     In a particularly preferred development of the invention there is further provided at least one carrier apparatus for carrying at least one coil with winding wire. That carrier apparatus makes it possible to handle the winding wire, for example in the form of conductor bundles, the length of which, in accordance with the invention, is such that the phase can be wound continuously throughout on the stator. The conductor bundle length required for that purpose results in a considerable weight which can no longer be handled manually. 
     In a particularly preferred embodiment two respective drums with winding wire are handled in pairs in order in that way to be able to handle both conductor bundles at the same time and a carrier apparatus carries three pairs of the drums with winding wire so that, using such a carrier apparatus, a three-phase system with two respective conductor bundles per phase can be wound on the stator. 
     In a particularly preferred development of the invention the drums with the winding wire are arranged pivotably about a central axis of rotation of the carrier apparatus. That arrangement makes it possible to compensate for twisting of the conductor bundles, which arises out of the rotation of the stator in the holding apparatus, by virtue of the drums being correspondingly rotationally entrained on the carrier apparatuses. 
     Further advantageous embodiments of the invention are set forth in the appendant claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in greater detail hereinafter with reference to the drawings in which: 
         FIG. 1  is a simplified view of a stator of a ring generator in a holding apparatus, 
         FIG. 2  is a view in cross-section through a conductor bundle, 
         FIG. 3   a  shows a part of the stator grooves according to the invention with inserted conductor bundles, 
         FIG. 3   b  shows a part of the stator grooves according to one alternative of the invention with inserted conductor bundles, 
         FIG. 3   c  shows a known structure of a stator winding, 
         FIG. 3   d  shows a structure according to the invention of a stator winding, 
         FIG. 4  is a simplified side view of the carrier apparatus according to the invention, 
         FIG. 5  is a front view of a carrier apparatus, and 
         FIG. 6  shows the arrangement of carrier apparatuses and stator for the production of a stator winding according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1  reference numeral  10  denotes the stator which has grooves  12  extending in the axial direction at the inner periphery. That is the most frequent structural configuration of a generator. The rotor (not shown) is within the stator  10 . That structural configuration is referred to as an internal rotor. Alternatively, in the case of a so-called external rotor in which the rotor encloses the stator  10 , the grooves  12  can be provided at the outer periphery of the stator. The grooves  12  are shown on an enlarged scale in  FIG. 3   a . The stator  10  is held in a holding apparatus  14  which stands on the ground and thus holds the stator  10  and in particular the grooves  12  at a height which forms a working position which is favorable in terms of working physiology. 
     As such a stator  10  of a ring generator is of a diameter of several meters and accordingly is high in weight, the stator  10  is supported rotatably on rotary mountings  16  and can be rotated for example in the direction of the arrow by a desired amount in order to move the grooves  12  to be worked upon, into a desired position. It will be appreciated that this rotary movement of the stator  10  can also be produced by using a drive motor (not shown). 
       FIG. 2  shows a conductor bundle  20  comprising a plurality of individual conductors  22  which are fitted in the form of a bundle into the grooves  12  of  FIGS. 1 and 3 . In this case the individual conductors  22  are insulated in relation to each other by a coating. 
     Forming conductor bundles  20  from individual conductors  22  has the advantage that those conductor bundles are not fixed in respect of their cross-sectional shape but are variable so that on the one hand they can be passed through a relatively narrow groove opening but on the other hand, by virtue of suitable deformation, they can fill the wider groove cross-section to the greatest possible extent in order to achieve a good filling factor for the groove  12  of  FIGS. 1 and 3 . 
       FIG. 3   a  shows an unwound section of the inner periphery of the stator  10 . Here, the grooves  12  are arranged horizontally one beside the other. Fitted into the grooves  12  are the conductor bundles which are shown here in simplified form as circular conductor bundles  20 . Each two of those conductor bundles  20  are combined to form a turn of a phase. This is shown in  FIG. 3   a  by arms  24  which connect a respective pair of the conductor bundles  20 . Accordingly as shown in  FIG. 3   a , two turns of a phase are inserted into each groove. For greater ease of viewing the drawing, the individual conductor bundles are numbered by  FIGS. 1–4  in an upward direction. In order to distinguish the individual phases of the six-phase system illustrated here, they are identified by the identifications P 1 –P 6  beneath the groove. 
     It will be clearly seen from  FIG. 3   a  that the conductor bundles  1  and  2  always form the first turn while the conductor bundles  3  and  4  always form the second turn which is inserted into the corresponding groove  12 . 
     Beginning by looking at the left in  FIG. 3   a , the phases P 1 –P 6  are shown in mutually juxtaposed relationship in a rising sequence and the succession of the conductor bundles is specified by references  4 ,  3 ,  2 ,  1 . After the groove  12  with the phase P 6 , that phase sequence is repeated again beginning with P 1 . In the second groove  12  with the phase P 5  illustrated in  FIG. 3   a  the sequence of the conductor bundles  20  is now altered. The first turn arranged in the groove  12  at the bottom thereof still consists of the conductor bundles  1  and  2 , but they are now interchanged in their sequence. Equally, the second turn still consists of the conductor bundles  20  identified at  3  and  4  but the sequence thereof is also interchanged. The phase P 6  arranged therebeside again involves the succession of conductor bundles, which is already known. 
     The phases P 1 –P 6  are shown once again in the right-hand part of  FIG. 3   a . In addition to the interchange of the conductor bundles  20  of the phase P 5 , which are identified by  1  and  2 , and  3  and  4  respectively, in this case the conductor bundles of the phase P 3  are also shown as being interchanged. It will be appreciated that, in this case also, the conductor bundles  20  identified by  1  and  2  form the first turn and the conductor bundles identified by  3  and  4  form the second turn of that phase, but it will be appreciated that within the turn, the position of the conductor bundles is again interchanged. 
     The reason for this interchange will be apparent if it is realized that the magnetic field lines extend not only in the longitudinal direction of the limbs  26  laterally delimiting the grooves  12 , but also through the grooves between two limbs  26  of differing polarities. That results in a skin or current-displacement effect in the individual conductor bundles  20  in dependence on the position thereof in the groove  12 . 
     If now the position of the conductor bundles is interchanged at given spacings, both conductor bundles  20  of a turn are correspondingly alternately subjected to that effect so that, with a suitable choice in respect of the interchange position and the frequency thereof, both conductor bundles  20  of a phase are subjected approximately uniformly to that effect so that no serious compensating currents resulting from non-uniform action flow and thus the maximum possible current can be delivered by the generator. A similar switching also occurs in other phases in subsequent phase series, not shown, but which can be easily understood from the description provided herein. 
       FIG. 3   b  therefore shows an illustration of the stator grooves with stator windings or stator conductors inserted therein, in which it can be seen that the stator grooves are very substantially filled with the windings and in which it is also possible to see the direction of current flow in the conductors (the arrow head and the arrow cross). In addition, the arrangement of the phases is altered in comparison with  FIG. 3   a  in order also better to show the change in the direction of winding. The view in  FIG. 3   b  however also makes it clear that more than 80% and preferably more than 95% of the total space of the stator groove is filled with windings and thus the proportion of air in the stator groove is extremely slight. 
       FIG. 3   c  shows a part of a conventionally produced winding, although without illustrating the stator and the grooves in which the winding is inserted. In this case the winding is formed from former-wound coils  40  having two turns  41 ,  42 . For the sake of improved clarity of the drawing those turns  41 ,  42  are shown in mutually displaced relationship. It will be appreciated that in the groove (not shown in  FIG. 3   c ), they are arranged exactly one over the other. 
       FIG. 3   c  shows three former-wound coils  40  of a phase. The spacing arises out of the fact that arranged alternately between former-wound coils of this phase are former-wound coils of the other phases of the stator, but they are not shown in the Figure. The former-wound coils  40  of a phase can be connected to each other by solder connections or screw-clamp connections or similar devices. 
     Those connections which are shown in  FIG. 3   c  are potential sources of trouble. 
       FIG. 3   d  shows the configuration according to the invention of a phase which is wound continuously throughout. In this case also, corresponding to the view in  FIG. 3   b ,  FIG. 3   d  again shows a part of the winding of a phase. In this case the individual turns  41 ,  42  are also shown in mutually displaced relationship in order clearly to show the nature of the design. 
     It can be seen immediately in this embodiment that the transitions illustrated as potential sources of trouble in  FIG. 3   b  are eliminated with this invention. Therefore, an interruption can no longer occur at the transitions between the individual winding portions. 
       FIG. 4  shows a side view of a carrier apparatus  30  for the conductor bundles used as the winding wires. An L-shaped base frame  31  provides that the entire carrier apparatus  30  stands securely. A carrier plate  32  is connected to the base frame  31  by way of a rotary mounting  33 . Fixed on the carrier plate  32  are carrier arms  34  which extend from the center of the carrier plate  32  a predetermined distance towards the periphery of the carrier plate  32  and which extend substantially horizontally away from the carrier plate  32  by a predetermined length. 
     Drums  36  with the conductor bundles used as the winding wire are rotatably fixed to those horizontally extending portions of the carrier arms  34 . 
     A rotary mounting (not shown) is provided between the vertical portion of the carrier arm  34 , which portion extends parallel to the carrier plate  32 , and the horizontally extending portion of the carrier arm. That rotary mounting co-operates with a drive  35  and permits a rotary movement of the horizontal portion of the carrier arm  34  about its longitudinal axis together with the drum  36  arranged thereon. That makes it possible to counteract a twist effect which occurs upon winding of the stator winding between the conductor bundles of that winding. 
       FIG. 5  shows a front view of that carrier apparatus  30 .  FIG. 5  shows a base frame  31  which tapers from the base towards the tip. Two transverse portions  38  and  39  are provided to enhance the stability of the structure. 
     The carrier plate  32  is arranged rotatably on the base frame  31 . Arranged on the carrier plate  32  are three carrier arms  34  which are respectively displaced by the same angle (120°) and to the substantially horizontally extending cantilever portions of which are fixed two respective drums  36  for the conductor bundles. By virtue of the rotatable mounting of the carrier plate  32 , with the drums  36  fixedly connected thereto by way of the carrier arms  34 , the unit can be rotated by a second motor  37 . 
     In the operation of producing the winding on the stator  10  each conductor bundle  20  is inserted into a groove  12 , it is bent over at the end of the groove  12  in the winding head and it is passed to a new, parallel-extending groove  12  in the winding head. The conductor bundle  20  is then bent over again in such a way that it can be inserted into that groove  12 . At the exit of that groove  12  the conductor bundle  20  is again bent over in the winding head in such a way that it can be passed to the next groove  12 . It will be appreciated that a corresponding twist is also produced in the conductor bundle  20  which is passing to the drum  36 . 
     The drums  36  are arranged in pairs on the horizontal portions of the carrier arms  34 . As those horizontal portions are rotatable by the drives  35  about the longitudinal axis thereof, the drums  36  are also rotated. It is possible in that way to counteract a twist in the conductor bundles, by rotation of the corresponding carrier arm  34 . 
     A second drive  37  is arranged between the base frame  31  and the carrier plate  32  and permits rotation of the carrier plate  32  with all carrier arms  34  disposed thereon and the drums  36  in order also to implement rotation of the stator  10  in the stator holder  14  and in that way to avoid twisting of the conductor bundles. 
       FIG. 6  shows in simplified form and without a conductor bundle between the carrier apparatuses  30  and the stator  10  the arrangement of two carrier apparatuses  30  and a stator  10  to be wound. The stator  10  is stored in a holding apparatus  14  and is rotatable in the peripheral direction (the direction of the arrow). As each of the carrier apparatuses  30  also has rotatably supported drums  36 , they can also perform or implement the rotary movement of the stator by virtue of a corresponding rotary movement. Therefore, the provision of two carrier apparatuses  30  each with three pairs of drums means that it is possible for six phases to be wound simultaneously on a stator. 
     It will be apparent that the present invention can be applied not only to ring generators for wind power installations but basically to any synchronous machine, in which respect it must be made clear that this does not involve very small-scale machines but machines which involve a considerable spatial extent and which usually have connected loads of under some circumstances several 100 kW and more. For a ring generator of a wind power installation for example a rated output of more than 500 kW is typical, even generators with a rated output of more than 4 MW have already been tested and will be used in the future. Just the stator alone of the described synchronous machine weighs several tons, while in the case of ring generators of over 4 MW, under some circumstances it weighs even more than 50 tons. 
     All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. 
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.