Patent Publication Number: US-2010127592-A1

Title: Stator-slot wedge and dynamoelectric-machine stator having stator slots and wedges

Description:
TECHNICAL FIELD 
     The present invention relates generally to dynamoelectric machines, and more particularly to a stator-slot wedge and to a dynamoelectric-machine stator having stator slots and wedges. 
     BACKGROUND OF THE INVENTION 
     Conventional dynamoelectric machines include motors and generators having a stator lamination stack. The stator lamination stack includes outwardly-extending or inwardly-extending steel stator teeth which are circumferentially spaced apart creating a stator slot between circumferentially-adjacent stator teeth. The motor/generator also includes a rotor which surrounds the outwardly-extending stator teeth or which is surrounded by the inwardly-extending stator teeth. 
     The sides of a corresponding stator tooth are parallel in some small stators (such as those of some small motors and generators), and the narrowly-spaced-apart tooth sides of a corresponding stator tooth are without any performance-limiting cutouts. The tooth sides bounding an intervening stator slot taper. In some designs, adjacent teeth each have a tooth tip which circumferentially projects from the corresponding tooth side into the intervening stator slot to partially close the intervening stator slot. 
     Coil windings having an electrically-insulative (dielectric) coating are randomly wound in the partially-closed stator slots. An electrically-insulative (dielectric) slot liner separates the randomly wound coil windings from the surrounding steel of the stator lamination stack. An electrically-insulative (dielectric) nonmagnetic stator wedge is attached to adjacent tooth tips to fully close the corresponding stator slot to restrain the randomly wound coil windings in the corresponding stator slot. 
     The insulation of the randomly-wound coil windings is subject to chafing during installation and from coil movement. In the absence of the coil liner or if the stator wedge were electrically-conductive and electrically contacted the adjacent tooth tips, such chafed insulation could eventually ground (electrically ground) the motor/generator. 
     What is needed is an improved dynamoelectric-machine stator having stator slots and wedges. 
     SUMMARY OF THE INVENTION 
     An expression of a first embodiment of the invention is for a dynamoelectric-machine stator including a stator lamination stack, a plurality of electrically-conductive magnetic wedges, a plurality of electrically-insulative nonmagnetic wedges, and coil windings. The stator lamination stack has a central longitudinal axis and a plurality of circumferentially spaced apart and outwardly-extending stator teeth. Adjacent stator teeth each have a tooth side bounding an intervening stator slot. The tooth sides bounding an intervening stator slot taper as one moves radially inward in the corresponding stator slot. Adjacent stator teeth each have a radially-outermost tooth tip which circumferentially projects from the corresponding tooth side into the intervening stator slot to partially close the intervening stator slot. The tooth sides of a corresponding stator tooth are planar and parallel. The coil windings are randomly wound in the stator slots. The nonmagnetic wedges are each positioned in a corresponding stator slot radially outward of the randomly-wound coil windings in the corresponding stator slot. The magnetic wedges are each positioned in a corresponding stator slot radially outward of the corresponding nonmagnetic wedge and physically and solid-magnetically contact the corresponding tooth tips to fully close the corresponding stator slot proximate the corresponding tooth tips. 
     An expression of a second embodiment of the invention is for a dynamoelectric-machine stator including a stator lamination stack, a plurality of electrically-conductive magnetic wedges, a plurality of electrically-insulative nonmagnetic wedges, and coil windings. The stator lamination stack has a central longitudinal axis and a plurality of circumferentially spaced apart and inwardly-extending stator teeth. Adjacent stator teeth each have a tooth side bounding an intervening stator slot. The tooth sides bounding an intervening stator slot taper as one moves radially inward in the corresponding stator slot. Adjacent stator teeth each have a radially-innermost tooth tip which circumferentially projects from the corresponding tooth side into the intervening stator slot to partially close the intervening stator slot. The tooth sides of a corresponding stator tooth are planar and parallel. The coil windings are randomly wound in the stator slots. The nonmagnetic wedges are each disposed in a corresponding stator slot radially inward of the randomly-wound coil windings in the corresponding stator slot. The magnetic wedges are each disposed in a corresponding stator slot radially inward of the corresponding nonmagnetic wedge and physically and solid-magnetically contact the corresponding tooth tips to fully close the corresponding stator slot proximate the corresponding tooth tips. 
     An expression of a third embodiment of the invention is for apparatus including a stator-slot electrically-conductive magnetic wedge having, as seen in an end view: a longer planar surface, a shorter planar surface which is parallel to the longer planar surface and which lacks an undercut., two planar surface portions disposed between the longer and shorter planar surfaces, and first, second, and third radius portions. The first radius portion extends from an edge of the shorter planar surface to the corresponding planar surface portion. The second radius portion extends from the corresponding planar surface portion to the third radius portion. The third radius portion extends from the second radius portion to the longer planar surface. The first radius portion is concave as seen from outside the magnetic wedge, and the second radius portion and the third radius portion each are convex as seen from outside the magnetic wedge. 
     Several benefits and advantages are derived from one all of the expressions of embodiments of the invention. In one example, the stator is a stator of a small motor whose stator-slot magnetic losses should be reduced and hence whose efficiency should be increased by the magnetic wedge which physically and solid-magnetically contacts the tooth tips to fully close the corresponding stator slot wherein the nonmagnetic wedge provides electrical insulation of the randomly-wound coil windings in a stator slot from the corresponding magnetic wedge. 
    
    
     
       SUMMARY OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a portion of a first embodiment of a dynamoelectric-machine stator showing two outwardly-extending stator teeth bounding an intervening stator slot containing randomly wound coil windings, an electrically-insulative nonmagnetic wedge, and a magnetic wedge; 
         FIG. 1A  is enlarged view of the top area of the stator of  FIG. 1 ; 
         FIG. 2  is a view as in  FIG. 1  but with the stator slot empty; 
         FIG. 3  is an end view of the entire stator lamination stack of  FIG. 1  with a complete set of stator teeth and stator slots and with the stator slots empty; 
         FIG. 4  is an enlarged perspective view of the magnetic wedge of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of a portion of a second embodiment of a dynamoelectric-machine stator showing two inwardly-extending stator teeth bounding an intervening stator slot containing randomly wound coil windings, an electrically-insulative nonmagnetic wedge, and a magnetic wedge; 
         FIG. 6  is a view as in  FIG. 5  but shown in smaller scale and with the stator slot empty; 
         FIG. 7  is an enlarged perspective view of the magnetic wedge of  FIG. 5 ; and 
         FIG. 8  is a perspective view of an embodiment of apparatus including a stator-slot magnetic wedge. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings,  FIGS. 1-4  show a first embodiment of the present invention. An expression of the embodiment of  FIGS. 1-4  is for a dynamoelectric-machine stator  10  including a stator lamination stack  12 , a plurality of electrically-conductive magnetic wedges  14 , a plurality of electrically-insulative nonmagnetic wedges  16 , and coil windings  18 . The stator lamination stack  12  has a central longitudinal axis  20  and a plurality of circumferentially spaced apart and outwardly-extending stator teeth  22 . Adjacent stator teeth  22  each have a tooth side  24  bounding an intervening stator slot  26 . The tooth sides  24  bounding an intervening stator slot  26  taper as one moves radially inward in the corresponding stator slot  26 . Adjacent stator teeth  22  each have a radially-outermost tooth tip  28  which circumferentially projects from the corresponding tooth side  24  into the intervening stator slot  26  to partially close the intervening stator slot  26 . The tooth sides  24  of a corresponding stator tooth  22  are planar and parallel. The coil windings  18  are randomly wound in the stator slots  26 . The nonmagnetic wedges  16  are each disposed in a corresponding stator slot  26  radially outward of the randomly-wound coil windings  18  in the corresponding stator slot  26 . The magnetic wedges  14  are each disposed in a corresponding stator slot  26  radially outward of the corresponding nonmagnetic wedge  16  and physically and solid-magnetically contact the corresponding tooth tips  28  to fully close the corresponding stator slot  26  proximate the corresponding tooth tips  28 . 
     It is noted that a tooth side  24  of a stator tooth  22  does not include any circumferentially-projecting tooth tip  28  or base of the stator tooth  22 . It is also noted that a tooth side having a wedge groove is not a tooth side which is planar. It is further noted that the free end of a stator tooth  22  is curved. 
     In one enablement of the expression of the embodiment of  FIGS. 1-4 , the nonmagnetic wedges  16  are disposed radially inward of the corresponding tooth tips  28 . In one variation, the dynamoelectric-machine stator  10  also includes a plurality of electrically-insulative slot liners  30  each disposed in a corresponding stator slot  26  between the randomly-wound coils windings  18  of the corresponding stator slot  26  and the corresponding tooth sides  24  and each contacting the corresponding nonmagnetic wedge  16 . 
     In one implementation of the expression of the embodiment of  FIGS. 1-4 , the nonmagnetic wedges  16  each have a planar, outward-facing surface  32  oriented substantially perpendicular to a radius  34  which bisects the corresponding stator slot  26 . In one variation, the magnetic wedges  14  each have a planar, inward-facing surface  36  which contacts the outward-facing surface  32  of the corresponding nonmagnetic wedge  16 . In one modification, the magnetic wedges  14  each have an exposed, planar, outward-facing surface  38  which is parallel to the inward-facing surface  36  of the corresponding magnetic wedge  14 . 
     In one application of the expression of the embodiment of  FIGS. 1-4 , the tooth tips  28  each have an exposed, outward-facing surface  40 , and the outward-facing surface  38  of the magnetic wedges  14  each are disposed radially inward of the outward-facing surface  40  of the corresponding tooth tips  28 . In one variation, the outward-facing surface  38  of each magnetic wedge  14  lacks an undercut. 
     In one employment of the expression of the embodiment of  FIGS. 1-4 , the tooth tips  28  each have a planar surface portion  42  inclined from the outward-facing surface  40  of the corresponding tooth tip  28 , disposed radially inward of the outward-facing surface  40  of the corresponding tooth tip  28  and radially outward of the corresponding tooth side  24 . In this employment, the magnetic wedges  14  each have two planar surface portions  44  disposed radially inward of the outward-facing surface  38  of the corresponding magnetic wedge  14  and radially outward of the inward-facing surface  36  of the corresponding magnetic wedge  14 . In this employment, the planar surface portions  44  of the magnetic wedges  14  each substantially completely physically and solid-magnetically contact the corresponding planar surface portion  42  of the corresponding tooth tips  28 . 
     In one arrangement of the expression of the embodiment of  FIGS. 1-4 , the magnetic wedges  14  each include first, second, and third radius portions  46 ,  48 , and  50 . In this arrangement, the first radius portion  46  extends from an edge  52  of the outward-facing surface  38  of the corresponding magnetic wedge  14  to the corresponding planar surface portion  44  of the corresponding magnetic wedge  14 , the second radius portion  48  extends from the corresponding planar surface portion  44  of the corresponding magnetic wedge  14  to the third radius portion  50 , and the third radius portion  50  extends from the second radius portion  48  to the inward-facing surface  36  of the corresponding magnetic wedge  14 . In this arrangement, the first radius portion  46  is concave as seen from outside the magnetic wedge  14 , and the second radius portion  48  and the third radius portion  50  each are convex as seen from outside the magnetic wedge  14 . 
     In one construction of the expression of the embodiment of  FIGS. 1-4 , an electrically-insulative nonmagnetic separator  54  is disposed in the stator slot  26  and divides the coil windings  18  into a radially-inner group and a radially-outer group. In one variation, the dynamoelectric-machine stator  10  has seventy-two stator teeth  22  and seventy-two stator slots  26 . In one modification, the width of each stator tooth  22  (the distance between the tooth sides  24 ) is less than one-third of an inch, and the radial extent of each stator slot  26  is less than three inches. 
     Referring again to the drawings,  FIGS. 5-7  show a second embodiment of the present invention. An expression of the embodiment of  FIGS. 5-8  is for a dynamoelectric-machine stator  110  including a stator lamination stack  112 , a plurality of electrically-conductive magnetic wedges  114 , a plurality of electrically-insulative nonmagnetic wedges  116 , and coil windings  118 . The stator lamination stack  112  has a central longitudinal axis  120  and a plurality of circumferentially spaced apart and inwardly-extending stator teeth  122 . Adjacent stator teeth  122  each have a tooth side  124  bounding an intervening stator slot  126 . The tooth sides  124  bounding an intervening stator slot  126  taper as one moves radially outward in the corresponding stator slot  126 . Adjacent stator teeth  122  each have a radially-innermost tooth tip  128  which circumferentially projects from the corresponding tooth side  124  into the intervening stator slot  126  to partially close the intervening stator slot  126 . The tooth sides  124  of a corresponding stator tooth  122  are planar and parallel. The coil windings  118  are randomly wound in the stator slots  126 . The nonmagnetic wedges  116  are each disposed in a corresponding stator slot  126  radially inward of the randomly-wound coil windings  118  in the corresponding stator slot  126 . The magnetic wedges  114  are each disposed in a corresponding stator slot  126  radially inward of the corresponding nonmagnetic wedge  116  and physically and solid-magnetically contact the corresponding tooth tips  128  to fully close the corresponding stator slot  126  proximate the corresponding tooth tips  128 . 
     It is noted that a tooth side  124  of a stator tooth  122  does not include any circumferentially-projecting tooth tip  128  or base of the stator tooth  122 . It is also noted that a tooth side having a wedge groove is not a tooth side which is planar. It is further noted that the free end of a stator tooth  122  is curved. 
     In one enablement of the expression of the embodiment of  FIGS. 5-7 , the nonmagnetic wedges  116  are disposed radially outward of the corresponding tooth tips  128 . In one variation, the dynamoelectric-machine stator  110  also includes a plurality of electrically-insulative slot liners  130  each disposed in a corresponding stator slot  126  between the randomly-wound coils windings  118  of the corresponding stator slot  126  and the corresponding tooth sides  124  and each contacting the corresponding nonmagnetic wedge  116 . 
     In one implementation of the expression of the embodiment of  FIGS. 5-7 , the nonmagnetic wedges  116  each have a planar, inward-facing surface  132  oriented substantially perpendicular to a radius  134  which bisects the corresponding stator slot  126 . In one variation, the magnetic wedges  114  each have a planar, outward-facing surface  136  which contacts the inward-facing surface  132  of the corresponding nonmagnetic wedge  116 . In one modification, the magnetic wedges  114  each have an exposed, planar, inward-facing surface  138  which is parallel to the outward-facing surface  136  of the corresponding magnetic wedge  114 . 
     In one application of the expression of the embodiment of  FIGS. 5-7  the tooth tips  128  each have an exposed, inward-facing surface  140 , and the inward-facing surface  138  of the magnetic wedges  114  each are disposed radially outward of the inward-facing surface  140  of the corresponding tooth tips  128 . In one variation, the inward-facing surface  138  of each magnetic wedge  114  lacks an undercut. 
     In one employment of the expression of the embodiment of  FIGS. 5-7 , the tooth tips  128  each have a planar surface portion  142  inclined from the inward-facing surface  140  of the corresponding tooth tip  128 , disposed radially outward of the inward-facing surface  140  of the corresponding tooth tip  128  and radially inward of the corresponding tooth side  124 . In this employment, the magnetic wedges  114  each have two planar surface portions  144  disposed radially outward of the inward-facing surface  138  of the corresponding magnetic wedge  114  and radially inward of the outward-facing surface  136  of the corresponding magnetic wedge  114 . In this employment, the planar surface portions  144  of the magnetic wedges  114  each substantially completely physically and solid-magnetically contact the corresponding planar surface portion  142  of the corresponding tooth tips  128 . 
     In one arrangement of the expression of the embodiment of  FIGS. 5-7 , the magnetic wedges  114  each include first, second, and third radius portions  146 ,  148 , and  150 . In this arrangement, the first radius portion  46  extends from an edge  152  of the inward-facing surface  138  of the corresponding magnetic wedge  114  to the corresponding planar surface portion  144  of the corresponding magnetic wedge  114 , the second radius portion  148  extends from the corresponding planar surface portion  144  of the corresponding magnetic wedge  114  to the third radius portion  150 , and the third radius portion  150  extends from the second radius portion  148  to the outward-facing surface  136  of the corresponding magnetic wedge  114 . In this arrangement, the first radius portion  146  is concave as seen from outside the magnetic wedge  114 , and the second radius portion  148  and the third radius portion  150  each are convex as seen from outside the magnetic wedge  114 . 
     In one construction of the expression of the embodiment of  FIGS. 5-7 , an electrically-insulative nonmagnetic separator  154  is disposed in the stator slot  126  and divides the coil windings  118  into a radially-inner group and a radially-outer group. In one variation, the dynamoelectric-machine stator  110  has seventy-two stator teeth  122  and seventy-two stator slots  126 . In one modification, the width of each stator tooth  122  (the distance between the tooth sides  124 ) is less than one-third of an inch, and the radial extent of each stator slot  126  is less than three inches. 
     With reference to  FIG. 8 , an expression of a third embodiment of the present invention is for apparatus including a stator-slot electrically-conductive magnetic wedge  214  having, as seen in an end view: a longer planar surface  236 , a shorter planar surface  238  which is parallel to the longer planar surface  236  and which lacks an undercut, two planar surface portions  244  disposed between the longer and shorter planar surfaces  236  and  238 , and first, second, and third constant radius portions  246 ,  248 , and  250 . The first radius portion  236  extends from an edge  252  of the shorter planar surface  238  to the corresponding planar surface portion  244 . The second radius portion  248  extends from the corresponding planar surface portion  244  to the third radius portion  250 . The third radius portion  250  extends from the second radius portion  248  to the longer planar surface  236 . The first radius portion  246  is concave as seen from outside the magnetic wedge  214 , and the second radius portion  248  and the third radius portion  250  each are convex as seen from outside the magnetic wedge  214 . 
     In one construction of the embodiment of  FIG. 8 , the magnetic wedge  214  comprises (and in one example consists essentially of) powdered iron. In one variation, the magnetic wedge  214 , as seen in the end view, is symmetrical about a line which bisects the longer planar surface  236  and the shorter planar surface  238 . In one application, the magnetic wedge  214  is used in place of magnetic wedge  14  and/or magnetic wedge  114 . 
     Several benefits and advantages are derived from one all of the expressions of embodiments of the invention. In one example, the stator is a stator of a small motor whose stator-slot magnetic losses should be reduced and hence whose efficiency should be increased by the magnetic wedge which physically and solid-magnetically contacts the tooth tips to fully close the corresponding stator slot wherein the nonmagnetic wedge provides electrical insulation of the randomly-wound coil windings in a stator slot from the corresponding magnetic wedge. 
     The foregoing description of expressions of embodiments has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise forms and steps disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.