Abstract:
A slip-ring arrangement of a rotating electrical machine includes a plurality of slip-rings disposed concentrically about an axis of the electrical machine one behind the other in an axial direction, the plurality of slip-rings configured to be self-supporting.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a continuation of International Patent Application No. PCT/EP2010/061569, filed on Aug. 10, 2010, which claims benefit to German Patent Application Nos. 10 2009 037 052.8, filed on Aug. 13, 2009 and 10 2009 048 265.2, filed on Oct. 5, 2009. The entire disclosure of each of these applications is incorporated by reference herein. 
     
    
     FIELD 
       [0002]    The present invention relates to the field of rotating electrical machines. 
       BACKGROUND 
       [0003]    In the case of rotating electrical machines having slip-rings, for example a polyphase asynchronous motor in the form of a slip-ring rotor, currents are transmitted by means of appropriate brushes via the slip-rings which rotate with the shaft. One example of a rotating electrical machine such as this is illustrated, partially, in  FIG. 1 . The rotating electrical machine  10  illustrated there, with its machine axis  17 , comprises a rotor, which can rotate about the machine axis  17 , with a central body  11  which merges at the end into a shaft  16 . A rotor laminated body  12  is seated on the central body  11  and a rotor winding  13  is accommodated in it, which rotor winding  13  has a rotor end winding  13 ′ at the end. The rotor  11 ,  12 ,  13  is concentrically surrounded by a stator laminated body  15 , in which a stator winding with a corresponding stator end winding  15 ′ is accommodated. A plurality of (four) slip-rings  14  are arranged on the outside of the shaft  16  and are used to transmit current between the rotor and the outside world. In the case of the machine illustrated in  FIG. 1 , the power loss must be dissipated by means of specific cooling devices. 
         [0004]    When machines of this type are highly loaded, particular attention must be paid to cooling in the area of the slip-rings. Because of the high electric and mechanical (friction) load on the brushes and the slip-rings  14 , an increased temperature development occurs in this area. Since the brushes react by increased wear to any discrepancy from the optimum operating temperature, and can be completely destroyed above a critical temperature, appropriate cooling must be provided for these components. 
         [0005]    As is shown in  FIG. 2 , the conventional design of the slip-ring area envisages a continuous shaft  16  on which the slip-rings  14  are mounted. With this design, the slip-rings  14  can be cooled only to a highly restricted extent. The cooling air (or some other cooling medium) would have to flow onto the slip-rings  14  from the outside. However, this is difficult because the slip-rings  14  rotate. Cooling from the interior, with the air flowing radially outwards from the interior of the shaft  16 , is impossible because of the closed shaft  16 . On the other hand, it is problematic for mechanical strength reasons to provide the shaft  16  with an appropriately large number of openings. 
         [0006]    EP-A1-0 052 385 describes a slip-ring arrangement for electrical machines, in which the slip-rings are provided with axial cooling gas holes, which are cut in the form of grooves or slots in the slip-ring surface. Cooling gas passes radially outwards via the grooves or slots into the cooling gas holes, with heat being absorbed, and is dissipated via these holes by means of a suction fan. However, the design of a cooling configuration such as this is very complex. 
         [0007]    In order to improve the cooling in the area of the slip-ring arrangement, DE-A1-32 32 102 describes that each slip-ring be subdivided into a number of individual slip-rings, which are shrunk onto intermediate shrink rings which are isolated from the slip-ring shaft. Cooling air fans are arranged in front and behind the slip-rings on the intermediate shrink rings. This solution also involves a complicated design, and very demanding cooling air routing. 
       SUMMARY 
       [0008]    In an embodiment, the present invention provides a slip-ring arrangement of a rotating electrical machine. The slip-ring arrangement includes a plurality of slip-rings disposed concentrically about an axis of the electrical machine one behind the other in an axial direction, the plurality of slip-rings configured to be self-supporting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
           [0010]      FIG. 1  shows a detail of an example of a rotating electrical machine with a slip-ring arrangement of a conventional type; 
           [0011]      FIG. 2  shows the section through a slip-ring arrangement of a conventional type, in the form of a dashed illustration and a flat illustration; 
           [0012]      FIG. 3  shows an illustration, comparable to that in  FIG. 2 , of a slip-ring arrangement according to a first exemplary embodiment of the invention; 
           [0013]      FIG. 4  shows a detail view of the slip-ring arrangement shown in  FIG. 3 ; 
           [0014]      FIG. 5  shows a perspective side view of a slip-ring arrangement according to a second exemplary embodiment of the invention; 
           [0015]      FIG. 6  shows a section through the slip-ring arrangement shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    An aspect of the present invention is to provide a slip-ring arrangement which avoids the disadvantages of the known slip-ring arrangements in terms of cooling and which is distinguished in particular by a simple design and very simple and effective cooling, and to specify a method for cooling of this arrangement. 
         [0017]    One feature according to an embodiment of the invention is that the slip-ring arrangement is designed to be self-supporting. The self-supporting design of the slip-ring arrangement makes it possible to dispense with a supporting shaft in this area. On the one hand, this results in the slip-rings being highly accessible from all sides, for the contact with a cooling medium. On the other hand, the slip-ring arrangement can be designed to be flexible with a major weight saving, resulting in considerable advantages with respect to the bearing for the machine shaft. 
         [0018]    One embodiment of the slip-ring arrangement according to the invention is distinguished in that the slip-rings are connected to one another forming through-flow openings, which are arranged between the slip-rings, for a cooling medium, in particular cooling air, and are kept separated by spacers which are arranged between the slip-rings. 
         [0019]    In particular in an embodiment, the spacers may comprise spacer rings which have additional spacing elements distributed over the circumference. 
         [0020]    In this case, the cooling medium is routed in a particularly advantageous manner if the additional spacing elements project in the axial direction on both sides of the respective spacer ring, and the additional spacing elements are integrally formed on the respective spacer ring. 
         [0021]    According to another embodiment of the invention, however, it is also feasible for the spacers to have spacing elements which are arranged distributed over the circumference. 
         [0022]    In this case, preferably, the slip-ring arrangement is held together by a plurality of axial tie bolts which are arranged distributed over the circumference, with the tie bolts being passed through the slip-rings and the spacing elements. 
         [0023]    In an embodiment, the slip-ring arrangement is particularly robust if the slip-rings and the spacing elements which are arranged between the slip-rings are pressed together by means of the tie bolts between two end rings which act as pressing flanges. 
         [0024]    In a further embodiment of the invention, the slip-rings are each subdivided into a plurality of separate sub-rings which are arranged concentrically and one behind the other in the axial direction, are connected to one another forming through-flow openings which are arranged between the sub-rings for a cooling medium, in particular cooling air, and kept separated by spacers which are arranged between the sub-rings. 
         [0025]    This allows the slip-rings to be cooled even more effectively. 
         [0026]    Preferably, the spacers for the sub-rings comprise spacing elements which are arranged distributed over the circumference. 
         [0027]    In another embodiment of the invention, the slip-ring arrangement surrounds an internal area, and in that output conductors are routed from the slip-rings to the machine-side end of the slip-ring arrangement in the internal area. This makes it possible to also extend the effective cooling to the output conductors. 
         [0028]    In an embodiment, a method according to the invention for cooling of a slip-ring arrangement according to the invention is characterized in that a cooling medium, in particular cooling air, is introduced in the axial direction into the interior of the slip-ring arrangement, and emerges radially again between the slip-rings and sub-rings. 
         [0029]    In an illustration comparable to  FIG. 2 ,  FIG. 3  and  FIG. 4  show a slip-ring arrangement according to a first exemplary embodiment of the invention. In the new design of the slip-ring arrangement  20 , there is no shaft whatsoever as a support for the slip-ring  18 . The slip-rings  18  can be arranged concentrically one above the other, that is to say one behind the other in the axial direction, and can be spatially separated from one another by means of spacer rings  21  located between them. The slip-rings  18  and the spacer rings  21  thus form a self-supporting slip-ring arrangement. Spacing elements  22  which project on both sides of the spacer ring  21 , distributed uniformly over the circumference, are integrally formed on the spacer rings  21  and ensure that annular gap sections are created between each of the spacer rings  21  and the adjacent slip-rings  18 , through which a cooling medium can flow radially along the sides of the slip-rings  18 , and can absorb heat. 
         [0030]    However, in the slip-ring arrangement  20  shown in  FIG. 3  and  FIG. 4 , not only are the individual slip-rings  18  separated from one another by spacer rings  21 , but the individual slip-rings  18  also consist of a plurality of sub-rings  19 , which are separated from one another by spacing elements  23  which are distributed uniformly over the circumference. This allows the cooling medium or the cooling air not only to flow up between the slip-rings  18  and the spacer rings  21  but also “through” the slip-rings  18  themselves, that is to say through the annular gap sections, which are formed by the spacing elements  23 , between the sub-rings  19 . On the one hand, this results in a more homogeneous distribution of the cooling air and, on the other hand, the surface area via which heat is emitted is considerably enlarged. 
         [0031]    However, the self-supporting embodiment of the slip-ring arrangement according to the invention also makes it possible to comply with the requirement to cool the output conductors, which are routed on the inside of the shaft or of the slip-rings. This can be seen from the exemplary embodiments of the invention illustrated in  FIG. 5  and  FIG. 6 : The slip-ring arrangement  30  in  FIGS. 5 and 6  is likewise designed in a self-supporting manner from four slip-rings  18 , the four which are themselves each subdivided into three sub-rings  19 . In this case, block-like spacing elements  24  distributed over the circumference are used instead of the spacer rings  21  in  FIG. 3 , in order to create the required separations and through-flow openings  31  between the individual slip-rings  18 . This results in a larger opening cross section for the cooling air in this area. 
         [0032]    In this exemplary embodiment as well, the sub-rings  19  are separated from one another by spacing elements, thus creating through-flow openings in the form of narrow annular gap sections, through which cooling air can flow. The self-supporting slip-ring arrangement  30  is held together by a plurality of axial tie bolts  27 , which are arranged distributed over the circumference and are passed through the slip-rings  18 , and sub-rings  19 , and the spacing elements  24 . The slip-rings  18  and sub-rings  19  and the spacing elements  24  arranged between the slip-rings  18  are pressed together by means of the tie bolts  27  between two end rings  25 ,  26 , which act as pressing flanges, and thus form a mechanically robust unit. The through-flow openings  31  are also provided between the outer slip-rings  18  and the end rings  25  and  26 , in order to ensure adequate cooling on the outside. 
         [0033]    The slip-ring arrangement  30  surrounds an internal area  28 , into which cooling air is introduced axially for cooling, and then emerges radially through the through-flow openings  31  and  32  (cooling medium  33  in  FIG. 5 ). The output conductors  29 , which are electrically connected to the slip-rings, can advantageously be laid in the internal area  28 . Since all of the cooling air flows over the output conductors  29 , they are cooled. 
         [0034]    The spacing elements  24  and the spacer rings  21  should be designed to allow insulation, for electrical isolation of the slip-rings  18 . This also applies to the tie bolts  27 . 
         [0035]    In addition to the improved cooling capability, material can also be saved in the described manner because there is no longer any need for a shaft to support the slip-rings  18 . The material saved leads to a cost reduction, and contributes to reducing the load on the machine bearings. Since the slip-rings  18  are generally not located between the bearing points but outside them, they represent a major load on the bearings (tumbling movements). The weight reduction in this area makes it possible to advantageously reduce the forces which act on the bearings. 
         [0036]    While the invention has been described with reference to particular embodiments thereof, it will be understood by those having ordinary skill the art that various changes may be made therein without departing from the scope and spirit of the invention. Further, the present invention is not limited to the embodiments described herein; reference should be had to the appended claims. 
       LIST OF REFERENCE SYMBOLS 
       [0037]      10  Rotating electrical machine (for example a synchronous machine) 
         [0038]      11  Central body 
         [0039]      12  Rotor laminated body 
         [0040]      13  Rotor winding 
         [0041]      13 ′ Rotor end winding 
         [0042]      14 ,  18  Slip-ring 
         [0043]      15  Stator laminated body 
         [0044]      15 ′ Stator end winding 
         [0045]      16  Shaft 
         [0046]      17  Machine axis 
         [0047]      19  Sub-ring 
         [0048]      20 ,  30  Slip-ring arrangement 
         [0049]      21  Spacer ring 
         [0050]      22 ,  23 ,  24  Spacing element 
         [0051]      25  End ring (inner) 
         [0052]      26  End ring (outer) 
         [0053]      27  Tie bolt 
         [0054]      28  Internal area 
         [0055]      29  Output conductor 
         [0056]      31 ,  32  Through-flow opening 
         [0057]      33  Cooling medium