Abstract:
A permanently-excited dynamoelectric machine includes a stator and a rotor supported for rotation about an axis. The stator has a winding system, which is embedded in grooves of a material forming a magnetic return path and interacts electromagnetically with permanent magnets of the rotor via an air gap between the stator and the rotor. The permanent magnets are disposed on the rotor, with each individual permanent magnet, on a side facing towards the air gap, having a North and South pole. The rotor, viewed in the circumferential direction, has a pole coverage by the permanent magnets of 100%, i.e. that the permanent magnets viewed in the circumferential direction, are arranged substantially without gaps.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of European Patent Application, Serial No. 14183004.2, filed Sep. 1, 2014, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a permanently-excited dynamoelectric machine. 
         [0003]    The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention. 
         [0004]    Permanently-excited dynamoelectric machines have permanent magnets on their rotors. Depending on the arrangement of the permanent magnets and their distribution on the rotor, a rotor with more or fewer poles is created. For certain areas of application small pole spacings are extremely sensible, but because of the manufacturability of this type of rotor, especially handling small permanent magnets, this is extremely complex and thus time-consuming. Furthermore these types of magnetic materials are attached to the rotor. However, the magnet material is not utilized 100%. 
         [0005]    Furthermore a rotor can principally be constructed with magnetized magnet rings; However this is only possible with comparatively small diameters of the rotor. Even with magnetic rings which essentially follow a Halbach magnet arrangement, there is a comparatively high proportion of the magnet volume which is not actively used. 
         [0006]    It would therefore be desirable and advantageous to provide an improved permanently-excited dynamoelectric machine to obviate prior art shortcomings and to create a magnet arrangement with small pole spacing, high air gap induction with simultaneously optimized magnet use, and yet with an inertia of the rotor that is comparatively small. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one aspect of the present invention, a permanently-excited dynamoelectric machine includes a rotor supported for rotation about an axis and having a circumference, permanent magnets disposed on the rotor about the circumference at a pole coverage of 100% substantially in the absence of a gap between adjacent one of the permanent magnets, and a stator having a winding system embedded in grooves of a material forming a magnetic return path and interacting electromagnetically with the permanent magnets of the rotor via an air gap between the stator and the rotor, with each of the permanent magnets having a North and South pole on a side facing towards the air gap. 
         [0008]    The present invention resolves prior art problems by providing special permanent magnets having a lateral magnetization. In such cases one side of the individual permanent magnets has both poles, i.e. North and South pole. Advantageously in such cases the magnet material is reduced to the materials of the permanent magnet through which the field lines pass and no magnetic return path via a laminated core, as with classical permanent magnets, is necessary. 
         [0009]    According to another advantageous feature of the present invention, the rotor can have a low-inertia structure in a torsion-proof manner with a shaft of the permanently-excited dynamoelectric machine to hold, fix and position the permanent magnets. A structure of comparatively low rotor inertia, i.e. the low-inertia structure of the rotor, bears the permanent magnets in the direction of the air gap of the dynamoelectric machine and on the other side is positioned on the shaft, especially on an amagnetic shaft, in a torsion-proof manner. 
         [0010]    According to another advantageous feature of the present invention, the rotor can have a laminated configuration, with the permanent magnets being disposed on its surface. Thus, the rotor can still be embodied with a laminated core, with the permanent magnets being disposed in corresponding cutouts/depressions or on the surface of the rotor, so that a cylindrical rotor is produced which has a constant air gap to the stator of the permanently-excited dynamoelectric machine. 
         [0011]    According to another advantageous feature of the present invention, the permanent magnets can have a lens-shaped, trapezoidal or shell-shaped configuration, such that, independently of a number of poles of the rotor, a section of the permanent magnets facing away from the air gap essentially follows a magnetic preferred direction. The permanent magnets can thus be configured as magnetic lenses or also as magnetic shells and disposed on the circumference of the rotor. As a result of the arrangement according to the invention, especially a pole coverage of 100% of the permanent magnets on the circumference of the rotor, a corresponding torque increase is created with simultaneous optimization of the magnet volume. This reduces manufacturing costs and makes it possible to manufacture rotors which can be embodied with a large diameter and also with low inertia. These high-pole rotors exhibit a high air gap induction and are thus equipped with a high torque. 
         [0012]    Likewise a tapering and/or staggered arrangement of the magnetic poles, viewed over the axial length of the rotor, is possible. 
         [0013]    Advantageously the permanent magnets are embodied as regards their side facing away from the air gap such that they follow a shape which embraces the magnetic preferred direction of this one permanent magnet. 
         [0014]    According to another aspect of the present invention, a wind power plant includes a generator having a dynamoelectric machine which includes a rotor supported for rotation about an axis and having a circumference, permanent magnets disposed on the rotor about the circumference at a pole coverage of 100% substantially in the absence of a gap between adjacent one of the permanent magnets, and a stator having a winding system embedded in grooves of a material forming a magnetic return path and interacting electromagnetically with the permanent magnets of the rotor via an air gap between the stator and the rotor, with each of the permanent magnets having a North and South pole on a side facing towards the air gap. 
         [0015]    Thus, a permanently-excited dynamoelectric machine according to the present invention can advantageously be used as wind power generator, since a high polarity and a corresponding high air gap induction are demanded there in order to convert the available wind into electrical energy highly efficiently. In such cases, both internal rotor generators and also external rotor generators are to be used. Advantageously, the generator can also be embodied as a direct drive or as a generator with upstream gearing. Likewise further applications for E-aircraft and E-cars are conceivable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0016]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0017]      FIG. 1  shows a basic longitudinal section of a dynamoelectric machine according to the present invention; 
           [0018]      FIG. 2  shows a cross-section of a rotor; 
           [0019]      FIG. 3  shows a further cross-section of a rotor with a support structure; 
           [0020]      FIG. 4  shows a perspective view of a laminated core of a rotor; 
           [0021]      FIG. 5  shows a perspective view of a permanent magnet; 
           [0022]      FIG. 6  shows a perspective view of a rotor; 
           [0023]      FIG. 7  shows a longitudinal section of a gondola of a wind power plant, 
           [0024]      FIG. 8  shows a cross-sectional view of a detail of a dynamo electric machine with external rotor, 
           [0025]      FIGS. 9 to 11  show exemplary embodiment of permanent magnets; and 
           [0026]      FIG. 12  shows a cross-section of a rotor. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0027]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0028]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown a basic longitudinal section of a dynamoelectric machine according to the present invention, generally designated by reference numeral  1  and positioned in a housing  6 . The dynamoelectric machine  1  can also be configured without housing. The housing  6  is supported via bearings  7  on a shaft  4  connected in a torsion-proof manner to a rotor  3 . In operation of the dynamoelectric machine  1 , the rotor rotates around an axis  5 . A winding system  10  is disposed in grooves  9  running essentially axially in a stator  2  of the dynamoelectric machine  1 . The winding system  10  forms winding heads on the end face sides of the stator  2 . The winding system  10  is designed as an extended winding system or with toothed coils. 
         [0029]    On its surface and on the side facing towards an air gap  8  between the rotor  3  and the stator  2 , the rotor  3  has permanent magnets  11 . Through electromagnetic interaction between the rotor  3  and its permanent magnets  11  with the winding system  10  of the stator  2 , the dynamoelectric machine  1  either acts as a generator or as a drive motor. 
         [0030]      FIG. 2  shows a cross section the rotor  3  with six poles formed by essentially asymmetrical lens-shaped permanent magnets  11 . The permanent magnets  11  are magnetized laterally, i.e. a bar magnet of which the ends, i.e. the poles, are facing towards one another—in the extreme case are almost folded together—can be imagined in this regard. 
         [0031]    Basically one magnetic pole N or S of the rotor  3  is thus formed by two poles of the permanent magnet  11  with the same name NN or SS lying next to one another. 
         [0032]    These permanent magnets  11  are accommodated in an essentially star-shaped carrier structure  14 , wherein, viewed in the circumferential direction, a volume  12  which is magnetically not active and does not contribute to torque generation is present between the permanent magnets  11 . This volume  12  is disposed between the permanent magnets  11  in the direction of axis  5 . 
         [0033]      FIG. 3  shows a further illustration of the rotor  3  with an arrangement of the lens-shaped permanent magnets  11  in a spoke-like carrier structure  14 . This is positioned in a torsion-proof manner on the shaft  4  and is thus disposed for rotation around the axis  5 . On the outer circumference of the rotor  3 , viewed in the circumferential direction, North and South poles thus occur alternately. Through the spoke-type carrier structure  14  the moment of inertia is reduced compared to comparatively constructed rotors with conventional permanent magnets and magnetic material can be saved in the volume  12 , so that the inertia further reduces. Furthermore this structure allows low-cost production. 
         [0034]    Likewise suitable as the carrier structure  14  is a laminated core  15  of the rotor  3  in accordance with  FIG. 4 . The laminated core  15  has cutouts or depressions, which each correspond to the shape of the permanent magnets  11  and into which the permanent magnets  11  can thus be inserted in a form fit. Advantageously in such cases the permanent magnets  11  are pre-fixed by an adhesive, wherein the entire rotor  3  is subsequently bandaged during the complete equipping of the rotor  3  or of the carrier structure  14 . Inter alia this bandaging guarantees that, even at high speeds, the positioning of its permanent magnets  11  in the motor or generator is guaranteed. 
         [0035]      FIG. 5  shows a laterally magnetized permanent magnet  11  with its magnetic preferred direction  16 . This lens-shaped magnet body, viewed in this case in cross-section, has two curved surfaces. The surface with the comparatively large radius is in this case the side facing towards the air gap  8  which has the North Pole and South pole. The side embodied with the smaller radius faces towards the laminated core  15  or the carrier structure  14 . 
         [0036]      FIG. 9  and  FIG. 10  show various embodiments of permanent magnets  11  which will be described in greater detail further below, with the shape of the permanent magnet according to  FIG. 10  departing from a strict lens-shaped embodiment of the permanent magnet  11 . 
         [0037]      FIG. 6  shows a perspective view of the rotor  3  with permanent magnet  11  on a carrier structure  14 . The respective North and South poles N, S of the rotor  3  are disposed at the contact areas of the permanent magnets  11 . Each permanent magnet  11  thus has a North pole and the South Pole towards the air gap  8 . There is an almost 100% pole coverage. 
         [0038]      FIG. 7  shows the use of such a dynamoelectric machine  1  in a wind power plant  17 . The dynamoelectric machine  1  used as a generator can hereby be driven directly (as direct drive) or via a transmission. 
         [0039]    This type of a dynamoelectric machine  1  according to the invention can, as  FIG. 7  principally shows in a longitudinal section, be disposed in a gondola of the wind power plant. The dynamoelectric machine  1  of this type has a high polarity which is especially important for directly-driven generators. The dynamoelectric machine  1  is easy to manufacture and has a comparatively high air gap induction in the air gap  8  of the dynamoelectric machine  1 , which for its part increases the energy efficiency of the wind power plant. 
         [0040]      FIG. 8  shows a dynamoelectric machine  1 , which is embodied as an external armature of a generator or motor. In order to conform to the air gap  8  of the dynamoelectric machine  1 , the permanent magnets  11  are no longer embodied lens-shaped but instead sickle-shaped or shell-shaped. Also in this case, the side of the permanent magnet  11  facing away from the air gap  8  is aligned to the preferred direction of magnetization. North and South pole of the permanent magnet  11  point to the air gap  8 . The stator  2  in this case is principally provided with grooves  9  in which winding systems are positioned. 
         [0041]      FIG. 8  shows by way of example a version of a dynamoelectric machine  1  with an external armature. The inventive idea is adapted to these circumstances, i.e. the winding system of the stator  2  is located on an inner carrier element, wherein the grooves point towards the air gap  8 . The permanent magnets  11  are accordingly adapted in their shape (radii) to the demands of the external armature. 
         [0042]      FIGS. 9 and 10  show embodiments of a permanent magnet  11  for an internal armature motor, in which the section  13  of the permanent magnet  11  facing towards the air gap  8  is adapted to the radius of the stator bore. The shape of the side of the permanent magnet  11  facing away from the air gap  8  is also preferably rounded, as  FIG. 9  shows, but for reasons of the manufacturing process, as shown in  FIG. 10 , can be embodied trapezoidal in principle. The deciding factor here is that through the lateral magnetization of this magnet  11  no additional return path material has to be provided within the rotor, since both the magnetic polarization and also the magnetic field guidance are undertaken in the permanent magnet  11 . 
         [0043]      FIG. 11  shows a further embodiment of a permanent magnet  11  for an internal armature motor, in which the section  13  of the permanent magnet  11  facing towards the air gap  8  is embodied concave to the radius of the stator bore. In this case the end sections  20  form the curved shape of the rotor  3 . 
         [0044]      FIG. 12  shows by way of a cross-section of a rotor  3  six poles which are formed by essentially asymmetrical shell-shaped permanent magnets  11  in accordance with  FIG. 11 . These permanent magnets  11  are likewise laterally magnetized, i.e. in the actual case at the ends the bar magnet. A magnetic pole N or S of the rotor  3  is thus also formed here by two poles of the same name NN or SS of the permanent magnet  11  in contact with one another. 
         [0045]    The sections  20  of the permanent magnets  11  are shaped in this case so that a rounded shape is produced which is adapted to the stator bore. In this case an almost constant air gap  8  is produced in the area of these sections  20 . 
         [0046]    The inventive idea of the laterally magnetized permanent magnets  11  is also suitable for ferrite materials, permanent magnets  11  with rare earth materials and Dysprosium-reduced materials especially neodymium-iron-boron-magnetized materials which are referred to as high-energy magnets. The shape of the permanent magnets  11  depends on the required torque generation, the geometrical dimensions of the stator bore and thus of the rotor  3  and on the required or desired air gap induction. 
         [0047]    In order to design the cross-section of the rotor  3  with such permanent magnets  11  in accordance with  FIG. 11 , round or roundish, advantageously the roundish depressions  13  of these permanent magnets  11  in accordance with  FIG. 11  are provided with amagnetic material. This avoids the air resistance or noise emissions above all at high speeds of the rotor  3 . 
         [0048]    80-pole rotors are provided for example as an application, which above all, because of the low-inertia spoke construction of a carrier structure  14 , are able to be used for E-aircraft, E-cars and also for wind power plants. In this context for example E-aircraft, E-car applications are to be seen as aircraft, helicopters, electrically-driven locos, power trains, streetcars, trucks and electrically-driven buses. 
         [0049]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.