Patent Publication Number: US-8125114-B2

Title: Dynamoelectric machine locking wedge for maintaining a winding in a slot

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 12/607,385, filed on Oct. 28, 2009 and titled “Locking Wedge For Maintaining A Winding In A Slot And Dynamoelectric Machine incorporating Same”. 
     BACKGROUND OF THE INVENTION 
     This invention relates generally to dynamoelectric machines and more particularly, to a locking wedge for maintaining a winding in a slot of a dynamoelectric machine. 
     Armature windings, also known as stator bar or rotor windings, are routinely inspected in at least some known electrical power generators, to verify their operation. In some known generators, a stator yoke in the generator surrounds an armature core and partially encloses the armature windings. The armature windings are formed from a plurality of copper conductors that are wound in the armature to form loops. The armature windings may be arranged within a stator slot in such a manner that desired voltage and current characteristics may be maintained by the generator during operation. 
     At least one known generator includes a wedge system to induce a radial retaining force (RRF) to the stator from wedges to facilitate reducing movement of the stator bar windings within the stator slot. The wedge system typically includes various filler strips disposed above and/or below the windings and a series of wedges located at the top of the slot. However, if the wedge system itself becomes loose, the amount of RRF is reduced such that the stator bar windings may move during operation. Accordingly, locking wedges have been used at the axial ends of the stator core to retain a series of interposed body wedges within a groove in the stator slot. However, known locking wedges are difficult to remove without sustaining damage during the removal process. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect of the invention, a locking wedge is provided for a slot of a dynamoelectric machine. The locking wedge includes a main body extending in an axial direction. The main body has a top surface and a bottom surface with a greater surface area than the top surface, and a first end surface and a second end surface opposed to the first end surface. First and second locking slots extend in the axial direction into a portion of the main body. The first locking slot begins in the first end surface and the second locking slot begins in the second end surface. A first locking member is disposed to fit into the first locking slot, and a second locking member is disposed to fit into the second locking slot. The first and second locking members can be inserted into the first and second locking slots, respectively, to lock the locking wedge in the slot. 
     In another aspect of the invention, a locking wedge is provided for a slot in a dynamoelectric machine. The dynamoelectric machine includes a core having a slot extending in an axial direction. The locking wedge has a wedge body extending in an axial direction, a top surface and a bottom surface having a greater surface area than the top surface, and a first end surface and a second end surface opposed to the first end surface. A first locking slot is disposed in at least a portion of the wedge body, and begins in the first end surface and extends in an axial direction. A second locking slot is disposed in at least a portion of the wedge body, and begins in the second end surface and extends in an axial direction. At least one locking member is configured to engage at least one of the first and second locking slots. 
     In a further aspect of the present invention, a dynamoelectric machine is provided having a core with at least one slot extending in an axial direction. The dynamoelectric machine includes at least one locking wedge having a wedge body extending in an axial direction. The wedge body has a top surface and a bottom surface having a greater surface area than the top surface, and first and second end surfaces, where the second end surface is opposed to the first end surface. A first locking slot is disposed in at least a portion of the wedge body, and begins in the first end surface and extends in an axial direction. A second locking slot is disposed in at least a portion of the wedge body, and begins in the second end surface and extends in an axial direction. A first locking member is disposed to fit into said the locking slot; and a second locking member is disposed to fit into the second locking slot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective end illustration of an exemplary electric generator; 
         FIG. 2  is a partial isometric illustration of a portion of the stator core in the electric generator stator shown in  FIG. 1 ; 
         FIG. 3  is an enlarged partial isometric illustration of a portion of the stator core shown in  FIG. 2 ; 
         FIG. 4  is an isometric illustration of a locking end wedge, according to an aspect of the present invention; 
         FIG. 5  is a top plan illustration of the locking end wedge of  FIG. 4 ; 
         FIG. 6  is an isometric illustration of a locking member that can be used with the locking end wedge of  FIG. 4 , according to an aspect of the present invention; and 
         FIG. 7  is a partial isometric illustration of a portion of the stator core in the electric generator stator shown in  FIG. 1 , according to an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A dynamoelectric machine is defined as any apparatus that converts electrical energy between the electrical and the mechanical state by means of an electromagnetic effect. As non-limiting examples, a dynamoelectric machine may include motors and/or generators. Windings are employed in the armature and field of a dynamoelectric machine, and may be held in place by a retaining system incorporating various components (e.g., wedges, ripple springs, etc.). 
       FIG. 1  is a perspective end view of an exemplary electric generator  100 . A rotor  102  is transparently represented by dashed lines. A plurality of stator bar windings  104  are positioned in slots  106  defined around an inner circumference of a stator core  108 . In the exemplary embodiment, stator bar windings  104  are formed from a plurality of flat bar conductors or stator bars that are coupled together to form a pre-determined winding path through winding  104 . In one embodiment, the stator bars are fabricated from copper. 
       FIG. 2  illustrates a partial, perspective illustration of a stator core  108 . The stator core  108  has a plurality of slots  106 , generally extending in an axial direction, which contain the windings  210 . As one example, two windings  210  may be contained within each slot  106 . The windings  210  are housed in the lower portion of the slots  106 . Various filler strips  220 , slides  230 , body wedges  240  and end wedges  250  may be installed above the windings  210 . 
       FIG. 3  is an enlarged, partial perspective illustration of a stator core, and shows the interrelation between the slots  106 , slides  230 , body wedges  240  and locking wedges  250 . The dovetail shaped wedge  240  engages a dovetail groove  315  and a slide  230  is normally driven under the wedge  240 . The stator core  108  may be comprised of many laminations of magnetic steel or iron material. The laminations form groups, and these groups are separated by spacers. The spacers define cooling vent slots  350 , which are generally orthogonal to the slots  106 . The cooling vents  350  between the groups of laminations allow for ventilation and cooling of the stator core. Typically, the vent gaps  242  in the wedges  240  are aligned with the cooling vents  350 . 
     The locking wedge  250  has a plurality of channels or cuts  255 . These cuts  255  allow the angled end portions  257  to compress inward during installation as the locking wedge  250  is axially inserted through dovetail groove  315 . Once the angled end portions  257  extend past the first cooling vent they snap into place and lock the wedge in position. The cuts  255  face in an axially-inward direction, towards the center of the slot or core. A disadvantage to this design is that the cuts  255  remain un-secured and the possibility exists that the locking wedge  250  could work loose or become damaged. 
       FIG. 4  illustrates an isometric view of an improved locking wedge  400 , according to aspects of the present invention. The locking wedge  400  has a main body  405  that extends in an axial direction  410 . The wedge has a top surface  420  and a bottom surface  425 . The bottom surface  425  may have a larger surface area than top surface  420 . In this variation, the sides  430  of the locking wedge may have angled surfaces. A first end surface  470  faces in an axially-inward direction and a second end surface  475  faces in an axially-outward direction. The locking wedge may also include angled vent gaps  440  which can be aligned with the cooling vents  350  in the core if desired. 
     A projection  450  may be included in one or both sides of the wedge and can be used to lock or snap into a cooling vent slot  350 . Locking slots  460  are axially disposed in at least a portion of the wedge body  420 . The locking slot  460  may also include a pair of axial oriented grooves  465  formed in the sides thereof. In one embodiment, the locking slot  460  may extend into about one quarter to about one half or more of the length of the wedge  400 . Alternatively, the locking slots  460  may have different lengths, and/or may have any length as desired for the specific application. A first locking slot  460  is preferably disposed in the axially-outward direction when the locking wedge is installed in the slot  106 , and a second locking slot, opposed to the first locking slot, is disposed in an axially-inward direction. As can be seen in  FIG. 4 , two locking slots  460  are located at each end of wedge  400 . The locking slots  460  gives the portions of the wedge on either side of the locking slot flexibility so that they may flex inward during insertion of the wedge  400  into dovetail groove  315 . 
       FIG. 5  illustrates a top view of wedge  400 . The locking slots  460  extend in the axial direction and include a groove  465  on both sides thereof. The locking slot can extend past projections  450  and enable the side portions  570  to flex inward during installation of the locking wedge  400 . 
       FIG. 6  illustrates an isometric view of a locking member  600  that is configured to fit into locking slot  460 . The locking member  600  includes a main body  610  and side rails  620 , both of which extend in an axial direction. The side rails  620  are configured to fit into the grooves  465  of the locking slot  460 . Once the locking wedge  400  is inserted into the dovetail groove  315 , the locking member  600  can be inserted into locking slot  460 , according to one aspect of the present invention. In another aspect, the locking member  600  may be inserted into locking slot  460  before wedge  400  is inserted into dovetail groove  315 . The locking member  600  locks the locking wedge into slot  106  and dovetail groove  315  by preventing the side portions  570  from flexing inward. 
       FIG. 7  illustrates a partial view of stator core  108 . The locking wedges  400  can be inserted into slot  106 . The locking wedge  400  has a double-ended locking mechanism (incorporating locking members  600 ), which enables the wedge to be locked from both ends, and enables the wedges  400  to be spaced from one another (if desired) rather than having them butted up against each other. The wedge  400  is longer than prior known wedges, and this allows fewer wedges to be used per core. One advantage of using fewer wedges is the reduction of labor and material costs. The dimensions of the wedge  400  may have any desired dimension as required in the specific application, but as non-limiting examples, wedge  400  may have a width of about one inch and a length of about 15 inches. Body wedges  240  could also be used with the present invention if desired. 
     The grooves  465  and rails  620  are shown with a rectangular profile, but could be designed to have any suitable shape or profile. As non-limiting examples, the groove  465  could have an arcuate, dovetail or trapezoidal shape. Accordingly, the rails  620  should be designed to have a complementary shape to fit into grooves  465  (e.g., an arcuate, dovetail or trapezoidal shape, respectively). Further, the overall cross-sectional profile of the locking slot and  460  and locking member  600  are generally rectangular, but could be configured to have any desired cross-sectional profile, including but not limited to polygonal, circular, hexagonal, trapezoidal, etc. 
     The locking wedge  400  and locking member  600  may be constructed of any suitable material, such as but not limited to, fiberglass, fiberglass laminates, fiberglass composites, magnetic materials, cotton phenolic, woven aramid fabrics, etc. In addition, the locking wedge  400  may have any suitable length as desired in the specific application, and as non-limiting examples, may include lengths from about one inch to about sixteen inches or more. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.