Abstract:
An electrical machine includes a coolable stator having an annular laminated stator core formed of a number of stator laminations having stator teeth which point radially inwards and form stator slots therebetween for accommodating a field winding wound onto the stator teeth. The laminated stator core has peripheral passage openings aligned with one another and forming cooling ducts.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation, under 35 U.S.C. §120, of copending International Application No. PCT/EP2012/004518, filed Oct. 29, 2012, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2011 118 917.7, filed Nov. 21, 2011; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an electrical machine having a rotor and a stator which can be cooled, which coaxially surrounds the rotor and which has an annular laminated stator core with stator teeth which are directed radially inward and between which stator slots are formed for accommodating a field winding which is wound onto the stator teeth. The laminated stator core is formed from a number of stator laminations with passage openings which are formed in the periphery of the stator laminations in a stator yoke region which surrounds the stator teeth and which are aligned with one another in the laminated stator core and form cooling channels. The electrical machine may be a motor or a generator. 
         [0004]    German Patent DE 44 11 055 C2 discloses providing a cooling circuit in which a liquid coolant circulates in order to cool a highly dynamic electric motor. The coolant flows into two sleeves which are at least partially spaced apart from one another and surround a stator in an approximately concentric manner. An inner sleeve of the two sleeves bears against the outer face of the stator by way of its entire surface. A stator winding head cooling device is connected to the cooling circuit for the coolant which flows in the sleeves. 
         [0005]    German Utility Model DE 20 2005 021 025 U1 discloses a cooled electro dynamic machine having a stator and having a can which bears against an inner wall of the cylindrical stator and seals off slots which are provided in the stator and in which flow channels that run in the slots are formed. 
         [0006]    German Patent Application DE 101 03 447 A1, corresponding to U.S. Pat. No. 6,822,352, discloses a stator cooling device of an electrical machine, wherein the stator is formed from an electrical laminated core and has one or more cooling channels for a flowing cooling medium and the cooling channels can be flexibly deformed and act on the laminated core. The cooling channels are formed by flexible corrugated metal tubes. 
         [0007]    German Patent Application DE 100 05 128 A1 discloses a stator, which can be cooled, for an electrical machine having a rotating internal rotor, wherein the stator, which can be cooled, has a cross section of rectangular shape with beveled corner regions. Cooling channels with cooling pipes which are inserted therein for conducting a coolant stream are disposed in corner regions, with the cooling channels passing through the stator parallel to a rotation axis. 
       SUMMARY OF THE INVENTION 
       [0008]    It is accordingly an object of the invention to provide an electrical machine, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known machines of this general type, which has a stator that can be cooled as effectively as possible and which, in particular, may form a cooling space in the region of stator-end winding heads in as optimum a manner as possible. 
         [0009]    With the foregoing and other objects in view there is provided, in accordance with the invention, an electrical machine, comprising a rotor and a stator coaxially surrounding the rotor and having an annular laminated stator core and a stator yoke region. The laminated stator core has an end face and radially-inwardly directed stator teeth. The stator teeth form stator slots therebetween and the stator teeth are surrounded by the stator yoke region. The laminated stator core is formed of a number of stator laminations having peripheries with passage openings incorporated therein in the stator yoke region. The passage openings are mutually aligned in the laminated stator core and form cooling channels having end faces and being configured to receive a flow of a cooling medium. A field winding is wound onto the stator teeth and accommodated in the stator slots, the field winding having winding heads projecting out of the end face of the laminated stator core and being contacted by a flow of the cooling medium around the winding heads. A potential compensation cable is provided and at least one hollow screw is inserted into the end face of at least a respective one of the cooling channels functioning to accommodate the at least one respective hollow screw, with the at least one hollow screw securing the potential compensation cable and maintaining functioning of the respective cooling channel to cool the stator. 
         [0010]    To this end, the stator includes a laminated, preferably annular, core including stator laminations. Stator slots, which are intended to accommodate coils or coil turns of a field winding (stator winding) which is wound onto the stator teeth, are formed between stator teeth which are directed radially inward. A number of passage openings are made in each stator lamination, with the passage openings being aligned with one another in the laminated stator core and forming cooling channels. 
         [0011]    The passage openings or cooling channels are used directly for a cooling medium, in particular oil. The passage openings or cooling channels within the laminated stator core not only provide comparatively good stator cooling, but also provide a comparatively large cooling space in the region of the stator-end winding heads. 
         [0012]    The passage openings are disposed in the stator yoke region which surrounds the stator teeth, in particular in the region between two adjacent stator slots. The stator laminations within the laminated core and/or the laminated stator core are/is transposed, offset or rotated, in particular, by a total of one tooth width. Due to the transposition, the cooling channels which are formed by the passage openings run within the laminated stator core or within the yoke region of the laminated stator core in a helical manner. 
         [0013]    The electrical machine has a machine housing for accommodating the stator and a rotor. A can for forming a stator-end coolant space (cooling space) for a cooling medium, in particular oil, or for sealing off the rotor from the coolant space is advantageously disposed in an air gap between the rotor and the stator. Cooling medium flows around winding heads of the field winding. The winding heads project out of the end face of the laminated stator core, with the cooling medium flowing through the laminated stator core by way of the cooling channels of the laminated stator core. 
         [0014]    The advantages achieved by the invention are, in particular, that effective cooling is achieved and a particularly compact construction of the wound stator is also possible due to the introduction of the cooling openings into the individual stator laminations and the orientation of the cooling openings in alignment with one another within the laminated stator core and also preferably over the circumference of the stator yoke region. 
         [0015]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0016]    Although the invention is illustrated and described herein as embodied in an electrical machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0017]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0018]      FIG. 1  is a diagrammatic, perspective view of a stator, which is constructed as a laminated core, with an annular cross section, stator teeth which project radially inward and stator slots which are provided between the stator teeth; 
           [0019]      FIG. 2  is a plan view of a stator lamination of the laminated stator core according to  FIG. 1 ; 
           [0020]      FIG. 3  is a perspective view of the stator according to  FIG. 1  including winding heads and connection cables for potential compensation; and 
           [0021]      FIG. 4  is a longitudinal-sectional view of an electric motor having a stator according to  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Referring now in detail to the figures of the drawings, in which parts that correspond to one another are provided with the same reference symbols, and first, particularly, to  FIG. 1  thereof, there is seen a perspective view of a stator  1  of an electric motor  2  as the electrical machine, which is illustrated in a longitudinal section in  FIG. 4 . The stator  1  is constructed as a laminated core  3  including a number of annular stator laminations  4  (seen in  FIG. 2 ) which are stacked in the axial direction  5  and connected to one another, for example welded or joined to one another in some other way. In this case, the stator laminations  4  are preferably assembled directly, that is to say without material application, a coating layer or the like. 
         [0023]    According to  FIG. 2 , the individual stator laminations  4  have stator teeth  6  which are directed radially inward and between which stator slots  7  are formed. Coils of a field or stator winding  8  ( FIGS. 3 and 4 ) are wound onto the stator teeth  6 . The stator slots  7 , which are formed between the stator teeth  6 , serve to accommodate the coil windings. 
         [0024]    A number of passage or cooling channel openings  9  are made in each of the stator laminations  4 . The openings  9  are aligned with one another within the laminated stator core  3  where they form cooling channels  10  ( FIG. 1 ). The openings  9  and therefore the cooling channels  10  are suitably disposed in a stator yoke (or stator yoke region)  11  which surrounds the stator teeth  6  and is integral or formed in one-piece with the stator teeth. 
         [0025]    The laminated stator core  3  is preferably cylindrical, so that the stator yoke region  11  is in the form of a ring. The passage openings  9  within the individual stator laminations  4  are preferably located between adjacent stator slots  7  and also, with reference to the stator teeth  6 , radially between connections  12  of the stator teeth to the stator yoke region  11  and an outer circumference, periphery or outer circumferential edge  13  of the stator yoke region. The free ends of the stator teeth  6  form a so-called pole shoe  14  radially on the inside. The pole shoe delimits an annular air gap (annular gap) between the stator  1  and a rotor  15  of the electric motor  2  (which is illustrated in  FIG. 4 ) at the stator end. 
         [0026]    As shown in  FIG. 1 , the laminated stator core  3  is expediently transposed or offset by a total of one tooth width of a stator tooth  6 . To this end, the stator laminations  4  within the laminated stator core  3  are rotated in relation to one another, preferably in the clockwise direction. Therefore, both the stator slots  7  and the stator teeth  6  and, in particular, the cooling channels  10  within the stator yoke region  11 , run in a virtually helical manner. 
         [0027]      FIG. 3  shows the laminated stator core  3  according to  FIG. 1  in the mounted state provided with the field or stator winding  8 . During the course of winding onto the stator teeth  6 , winding heads  8   a  and  8   b  of the field or stator winding  8  are formed at end faces  3   a  and  3   b  of the stator core  3 , with the winding heads projecting beyond the laminated stator core  3  in the axial direction  5 . As can be seen in  FIG. 3 , the winding heads  8   a ,  8   b  extend in the radial direction  16 , at the end face  3   b  of the laminated stator core  3 , in such a way that the stator yoke region  11  is accessible, in particular to a cooling medium. As can also be seen, coil or winding ends  17  of the typically three-phase field or stator windings  8  are routed outward at the winding head  8   b.    
         [0028]    Furthermore,  FIG. 3  shows that some of the cooling channels  10  are used, at the mouth end, to accommodate preferably hollow screws as fastening elements  18 . The fastening elements fasten cables or lines  19  for potential compensation to the laminated stator core  3  and make contact with them there. Each cable  19  is provided, for example, with a respective protective tube  20 . Therefore, three cooling channels  10  from amongst the cooling channels  10  are used for potential compensation. The fastening elements  18 , which are preferably constructed as hollow screws, allow the function of the cooling channel  10  to be maintained, with the cooling channel additionally assuming the function of accommodating the fastening element  18  for potential compensation. 
         [0029]    The electric motor  2  (illustrated in a longitudinal section in  FIG. 4 ) has a motor housing  21  in which the stator  1  and the rotor  15  are disposed. The rotor  15  sits on a motor shaft  22 . The motor shaft is mounted within the motor housing  21 , preferably by using rolling or ball bearings  25  or  26 , in the region of end plates  23 ,  24  which are connected to an end face of the motor housing  21 , and the motor shaft is routed out of the motor housing  21  at one end. 
         [0030]    A cylindrical, closed can  30  is disposed in the air gap which remains between the stator  1  and the rotor  15 . The can  30  delimits a stator-end cooling space  27  for a cooling medium, in particular oil. Cooling medium flows around the winding heads  8   a ,  8   b  of the field winding  8 . The winding heads  8   a ,  8   b  project out of the end face of the laminated stator core  3  and the cooling medium additionally flows through the cooling channels  10  which are formed by the passage openings  9  in the stator laminations  4 . 
         [0031]    It can be seen that the stator yoke region  11  is accessible and therefore serves as an abutment face  28  against which an apparatus, for example in the form of a cylindrical mold or the like, can bear. The apparatus or mold serves to introduce or apply an insulating medium, for example wax or the like, in or into the winding heads  8   a ,  8   b . Further insulating material  29  is also introduced into the motor housing  21  between the stator  1  or the laminated stator core  3  of the stator and the inner wall of the motor housing. 
         [0032]    The invention is not restricted to the exemplary embodiment described above. Rather, other variants of the invention can also be derived from the exemplary embodiment by a person skilled in the art, without departing from the subject matter of the invention. In particular, all of the individual features which are described in connection with the exemplary embodiment can further be combined with one another in another way, without departing from the subject matter of the invention.