Patent Publication Number: US-7586231-B2

Title: End cap for segmented stator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/806,560 filed Mar. 23, 2004, the entire disclosure of which is incorporated herein by reference. 

   FIELD OF THE PRESENT DISCLOSURE 
   The subject matter of the present disclosure relates to stator assemblies for electromagnetic machines. More particularly, the subject matter of the present disclosure relates to “loose” segmented stator assemblies having discrete and individually wound stator segments and end caps. In one example, the “loose” segmented stator assembly of the present disclosure can be used in a hermetic motor of a compressor for a refrigeration system. 
   BACKGROUND OF THE PRESENT DISCLOSURE 
   Segmented stators for use in electromagnetic machines, such as hermetic compressor motors of a refrigeration system, are known in the art. The segmented stator assemblies typically include a plurality of segments that form the stator of the motor. The stator is typically contained within a shell, and a rotor and shaft are positioned for rotation within a bore of the stator. Each segment of the stator includes a yoke portion and a tooth portion. As is known in the art of electromagnetic machines, such as induction motors, brushless permanent magnet (BPM) motors, and switched reluctance (SR) motors, the stator teeth are wound with magnet wires to form winding coils having a plurality of phases. 
   End caps fit on the ends of segments of a stator to facilitate the placement of wire on the segments. For example, U.S. Pat. No. 6,584,813 to Peachee et al. and entitled “Washing machine including a segmented stator switched reluctance motor,” which is incorporated herein by reference in its entirety, discloses a segmented stator assembly that uses end caps on the segments. In addition, U.S. Pat. No. 2,688,103 to Sheldon; U.S. Pat. No. 2,894,157 to Morrill; U.S. Pat. No. 6,127,753 to Yamazaki; U.S. Pat. No. 6,509,665 to Nishiyama et al and U.S. Patent Application No. 2002/0084716 to Harter et al. disclose various examples of end caps for stators. The prior art end caps are typically glued to the segments, and winding coils are wound about the tooth portions of each segment and on portions of the end caps. Therefore, any problems with the end caps can produce poor winding characteristics in the winding coils, such as undesirable overlap of the winding coils or inefficient density of the winding coils about the tooth portions. 
   Segmented stators require various manufacturing steps to interconnect all the individually wound coils on the segments to form the phase windings. To interconnect the winding coils of the stator, it is known in the art to use a printed circuit board to interconnect the various winding coils of the stator. The printed circuit board is generally circular and has a plurality of terminal pads that connect to terminal pins on each end cap of the stator. 
   Rather than using a printed circuit board, interconnect wires can be used to connect the various winding coils of opposing electrical phases (voltages). Ends of the interconnect wires can be welded or soldered to terminal pins on the end caps of the stator, such as disclosed in U.S. Pat. No. 2,688,103 to Sheldon. The interconnect wire can be routed on the stator in several different ways. In one example, the interconnect wires can be routed around the outside portions of the segments. It is known in the art to provide hooks on the outboard side of a stator for routing the wires to route interconnect wires on the outside portion of the stator. In a compressor motor, however, routing wires on the outside portion of the stator is not desirable. 
   In another example, the interconnect wires can be routed within the inside portion of the stator. It is known in the art to use a stitcher ring to guide the wires to route interconnect wires on the inside portion of the stator. For example, a stitcher ring, having part no. 280138 and manufactured by Emerson Electric Co, is used in motors to route interconnect wires. The stitcher ring is a disc with a central opening for passage of a rotor shaft. The stitcher ring positions on a lead-end of the stator and fits partially over the bore of the stator. A plurality of hooks are provided on one side of the stitcher ring and are used to route wire between winding coils. In another example, U.S. Pat. No. 5,900,687 to Kondo et al. discloses an end plate having grooves for arranging the conducting wires between the coils of the various phases. The end plate is fixed onto an upper portion of the winding coils of the stator in the area of the bore. 
   Because the interconnect wires routed on a stator are positioned adjacent one another, a large voltage differential between the adjacent interconnect wires can produce phase-on-phase conditions in the motor and can cause premature failure of the insulation on the wires. In a compressor motor, any large voltage differential between adjacent wires can be magnified because the motor is used as a magnetization fixture where upwards of 1600 Volts and 1200 Amps may be passed through the stator at a given instant. In addition, a compressor motor can be used with a Pulse Width Modulated (PWM) drive. The waveform from the PWM drive may have high voltage spikes on the leading and trailing edges of the waveform, creating the need to separate the phase wires. Traditionally, motors use insulation made of MYLAR® or NOMEX® between the magnetic wires forming the separate winding coils. It is also known in the art to use secondary insulation between the interconnect wires interconnecting the winding coils. Unfortunately, such secondary insulation can increase the manufacturing costs and production time of the motor. 
   Some segmented stator assemblies use interlocking features or hinges on the segments to hold them together. For example, U.S. Pat. No. 6,127,753 to Yamazaki et al. discloses segments having hinged ends that connect adjacent segments together. Unlike the segmented stators having interlocking segments, some prior art segments for stators are not formed to directly interlock with other segments of the stator. Instead, such segments have ridged and slotted ends. The ends merely fit together on adjacent segments so that the segments are not physically held together in the absence of some other retaining structure. Hence, the stator segments are used to form a stator of the “loose” segmented type. “Loose” segmented stators typically require a secondary retention device, such as a heavy metal band, to hold the segments together when the segments are formed into the annular shape of the stator. The heavy band is positioned around the outside diameter of the segments to hold them together when manufacturing the motor or when transporting the stator as a separate part to customers. In addition, conventional segmented stators do not provide a ready way to axially align the segments to prevent unacceptable differences in tolerances during manufacture. Currently, no form of axial alignment for “loose” segmented stators is thought to exist in the art. 
   As noted above, segmented stators can be used in hermetic motors for a compressor of a refrigeration system. The compressor has an oil pump on the bottom of the compressor, which is known as the oil sump. Typically, oil is pumped up through a shaft of the hermetic motor, past the stator and rotor, and to the main bearing of the compressor. From the bearing, the oil is let loose on a lead end of the motor to drain back to the oil sump. The contours of the motor, such as the contours of the segmented stator, can determine how the oil is allowed to return to the oil sump from the lead end of the motor. In addition, oil from the oil sump in the hermetic motor can also pool in cavities and recesses of typical end caps, which can prevent the return of oil to the oil sump. If the motor does not have sufficient drain area, for example, the oil will become dammed on the lead-end of the motor. The damming of oil can cause higher oil circulation in the refrigeration system, can starve the oil pump of oil, and can hinder the performance of the compressor. On the other hand, if the motor has too much drain area for the return of the oil, then the stator may have less back iron than desired. A stator with less back iron can have higher magnetic flux saturation and reduced performance. 
   Typical stators for hermetic motors in compressors have flat areas defined on the outside diameter of the stator. The flat areas of the stator provide a drain area for the oil to pass from the lead-end of the motor to the oil sump. In some stators, the flat areas are made very large so that the material used to form the stator can be used efficiently. However, the large size of these flat areas in the stator can deform the shell of the motor. For example, the progression of the laminations forming the stator with the flat areas can create issues with shell deformation. In addition, the scroll shear pattern when used in a compressor can create issues with shell deformation because of the physical size of the flat areas on the outside of the stator. Thus, a trade off is typically made between the size of the flat areas in the stator and the efficient use of material used to make the stator. 
   The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above. 
   SUMMARY OF THE PRESENT DISCLOSURE 
   A stator for an electromagnetic machine includes a plurality of discrete and individually wound stator segments having end caps positioned on the segments. In one aspect, the end caps have legs for positioning the end cap on the segments with an interference fit. In another aspect, the end caps have angled surfaces to facilitate winding of wire on the segments. In another aspect, the end caps have male and female couplings that mate together to couple adjacent segments together. In yet another aspect, the end caps have fingers and slots for aligning the segments on substantially the same plane. In a further aspect, the end caps have wire isolation features, including hooks, shelves and ledges, for separating the interconnect wires routed on the stator to electrically interconnect the segments. In another aspect, the segments include scalloped contours on their outer edges for draining oil, and the end caps have passages for draining oil. 
   The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, preferred embodiments, and other aspects of subject matter of the present disclosure will be best understood with reference to a detailed description of specific embodiments, which follows, when read in conjunction with the accompanying drawings, in which: 
       FIG. 1  illustrates a plan view of an embodiment of a segmented stator assembly according to certain teachings of the present disclosure positioned in a shell. 
       FIGS. 2A through 2B  illustrate top and bottom perspective views of the disclosed segmented stator assembly. 
       FIGS. 3A through 3B  illustrate a plan view and a perspective view of a laminated segment for the disclosed segmented stator assembly. 
       FIG. 4  illustrates a detailed plan view of a portion of the disclosed segmented stator assembly. 
       FIGS. 5A through 5D  illustrate various views of an embodiment of a lead end cap on a segment of the disclosed stator assembly. 
       FIGS. 6A through 6F  illustrate various isolated views of the lead end cap for the disclosed stator assembly. 
       FIGS. 7A through 7C  illustrate an alternative embodiment for coupling ends of adjacent lead end caps together. 
       FIGS. 8A and 8B  illustrate another alternative embodiment for coupling ends of adjacent lead end caps together. 
       FIGS. 9A through 9C  illustrate various views of an embodiment of a base end cap on a segment of the disclosed stator assembly. 
       FIGS. 10A through 10F  illustrate various isolated views of the base end cap for the disclosed stator assembly. 
       FIG. 11  illustrates the disclosed lead and base end caps on adjacent segments having different stack heights. 
       FIGS. 12A through 12D  illustrates an exemplary stitching pattern for the interconnect wires on the disclosed stator assembly. 
       FIG. 13  schematically illustrates flux density paths on an example of the disclosed stator assembly. 
       FIG. 14  illustrates a plan view of the disclosed segment relative to a circumference of a shell. 
   

   While the disclosed end caps, segments, stator, and associated methods are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. The figures and written description are not intended to limit the scope of the inventive concepts in any manner. Rather, the figures and written description are provided to illustrate the inventive concepts to a person skilled in the art by reference to particular embodiments, as required by 35 U.S.C. § 112. 
   DETAILED DESCRIPTION 
   A. Stator Assembly 
   Referring to FIGS.  1  and  2 A- 2 B, an embodiment of a segmented stator assembly  10  according to certain teachings of the present disclosure is illustrated.  FIG. 1  illustrates a plan view of the disclosed stator assembly from the lead-end, and  FIGS. 2A and 2B  illustrate perspective views of the disclosed stator assembly  10  from the lead-end and the base-end, respectively. The disclosed stator assembly  10  is of the “loose” segmented stator type. The disclosed stator assembly  10  can be used in variable speed motor applications, such as a hermetic compressor for a refrigeration system of a vehicle or a residence, for example. However, certain teachings of the present disclosure can be used with other types of stator and used in other motor applications. 
   The segmented stator assembly  10  includes a plurality of discrete stator segments  20 . The segments  20  have lead end caps  50  and base end caps  150 . In the present example, the segmented stator assembly  10  has nine segments  20  that are individually wound with wire to form winding coils  92 , although alternate embodiments with a different number of segments and end caps are envisioned and possible. The segmented stator assembly  10  is typically contained within a motor shell (not shown), and a rotor and shaft (not shown) are positioned for rotation within a bore  11  of the stator  10 . 
   B. Segments 
   Referring to  FIGS. 3A-3B , a laminated segment  20  for the disclosed stator assembly  10  is shown in a plan view and a perspective view, respectively. The construction of each segment  20  is generally similar to the construction of segments used in conventional segmented stators. For example, each segment  20  is formed from a plurality of substantially identical laminations  21 . The laminations  21  are made of stamped steel and stacked together to form the segment  20 . 
   Each segment  20  includes a yoke portion  22  and a tooth portion  24 . The yoke portion  22  has an outboard edge  30  that defines a rear channel  38 . The rear channel  38  receives a portion of the end caps  50  and  150  in a press-fit relationship to help couple the end caps  50  and  150  to the stator segments  20 , which is described in more detail below. In the present embodiment, each segment  20  includes a slotted end  32  and a ridged end  34  defined in the yoke portion  22 . The slotted and ridged ends  32  and  34  of adjacent segments  20  interfit with one another when the segments  20  are formed into the annular shape of the stator  10 , as best shown in FIGS.  1  and  2 A- 2 B. In particular, the slotted ends  32  receive the ridged ends  34  when adjacent stator segments  20  are brought together. The adjacent ends  32  and  34  inhibit relative movement of the adjacent stator segments  20  in at least one direction. Unlike prior art stator assemblies having interlocking hinges or puzzle pieces that serve to directly connect adjacent stator pieces together, the slotted and ridged ends  32  and  34  of the present embodiment do not physically hold together adjacent stator segments  20  in the absence of some other retaining structure. Hence, the stator segments  20  in the present embodiment form a stator of the “loose” segmented type. 
   In the present embodiment, the tooth portion  24  of the segment  20  has a pole end  26 , which is generally “T” shaped. The inboard face of the pole end  26  (i.e., the surface of the pole end  26  facing away from the yoke portion  22 ) forms the bore of the assembled stator within which the rotor is positioned for rotation. As is known in the art, wire (not shown) is wound about the tooth portion  24  of the stator segments  20  to form a winding coil. The outboard face of the pole end  26  (i e., the surface of the pole end  26  facing the yoke portion  22 ) at least partially helps to position and retain the winding coil in a desired position on the tooth portion  24 , as described in more detail below. 
   C. Lead End Caps 
   As noted above, each of the discrete stator segments  20  of the assembled segmented stator  10  as shown in FIGS.  1  and  2 A- 2 B has a lead end cap  50  and a base end cap  150 . Referring to  FIGS. 5A-5D , a discrete stator segment  20  having end caps  50 ,  150  is shown in a number of isolated views to reveal relevant details of the lead end cap  50  for the disclosed stator assembly. The lead end cap  50  is used on the lead-end of the stator segment  20  (i.e., the end of the stator segment  20  positioned toward the main bearing or “top” of the motor). The lead end cap  50  is composed of non-conductive material and is preferably composed of RYNITE® FR530 by Dupont. 
   The lead end cap  50 , which is also shown in various isolated views in  FIGS. 6A-6F , includes a body portion  60 , a winding portion  74 , and an inboard wall  76 . The lead end cap  50  fits on the stator segment  20  so that a substantially flat surface  52  of the end cap  50  positions adjacent the lead-end of the segment  20 . In particular, the body portion  60  positions onto the yoke portion  22  of the segment  20 , the winding portion  74  positions on to the tooth portion  24  of the segment  20 , and the inboard wall  76  positions of the pole end  26  of the segment  20 . As best shown in the side views of  FIGS. 6D and 6F , both the body portion  60  and inboard wall  76  of the lead end cap  50  extend well beyond the winding portion  74  and form a winding pocket  70 , and both the body portion  60  and inboard wall  76  have substantially the same height above the tooth portion. As schematically shown in  FIGS. 5A-5D , wire of the winding coil  92  is wound within the winding pocket  70  about the tooth portion  24  so that a portion of the winding coil  92  is partially positioned between the body portion  60  and the inboard wall  76  and is partially positioned on the winding portion  74  of the end cap  50 . 
   As best shown in  FIG. 6A , the winding portion  74  of the lead end cap  50  defines a plurality of ribs, which are partly necessary for molding the end cap  50 . Preferably, the winding portion  74  defines five ribs for providing sufficient strength to the end cap  50 . The ribs may be formed in the winding pocket  70  where wire is intended to be wound, as shown in  FIG. 6A . In an alternative embodiment, the bottom surface  52  (shown in  FIG. 6B ) may instead define the plurality of ribs. Forming the ribs in the bottom surface  52  may be beneficial in strengthening the end cap  50  because the ribs will be under compression when positioned against the surface of a segment. In addition, the connection of the winding portion  74  with the inboard wall  76  on the top surface of the winding portion  74  may be a high stress point. By forming the ribs in the bottom surface  52  of the winding portion  74 , the potentially “high stress” connection of the winding portion  74  to the inboard wall  76  will be uniform, which can reduce the chances of breakage between the winding portion  74  with the inboard wall  76 . 
   1. Retaining Features 
   As best shown in  FIGS. 5A-5D , the lead end cap  50  positions on the stator segment  20  with a plurality of legs. In the present embodiment, the lead end cap  50  includes two tooth legs  82  and a body leg  88 . The tooth legs  82  are attached to the inboard wall  76 , the body leg  88  is attached to the edge of the body portion  60 , and the legs  82  and  88  extend from the flat surface  52  of the end cap  50  for fitting on the segment  20 . When the end cap  50  is positioned on the segment  20 , the tooth legs  82  fit on either side of the tooth portion  24 , and the body leg  88  fits in the channel  38  formed on the outboard edge  30  of the segment  20 . The edges of the tooth legs  82  fit on either side of the tooth portion  24  an interference fit, and an outboard surface of the tooth legs  82  position against the inboard face of the pole end  26 . 
   The three legs  82  and  88  substantially hold the end cap  50  on the segment  20  and sufficiently align the end cap  50  on the segment  20 . With the end cap  50  substantially stabilized on the segment  20  by the legs  82  and  88 , the end cap  50  is prevented from moving during winding procedures or other manufacturing steps. For example, the legs  82  and  88  minimize any axial and tangential movement of the end cap  50  and eliminate the need to glue the end cap  20  to the segment  20 . Conventionally, end caps known in the art are glued on the segment to keep the end cap from moving side to side or into the bore during manufacture. On the disclosed end cap  50 , however, the tooth legs  82  and the body leg substantially hold the end caps  50  in place on the segment  20  without the need for glue. 
   2. Undercut Areas 
   Because the legs  82  and  88  of the lead end cap  50  have edges that form an interference fit with the segment  20 , the edges pass against edges of the stator segment  20  as the end cap  50  is positioned on the segment  20 . Consequently, the edges of the segment  20  can scrape material of the plastic legs  82  and  88  as the end cap  50  is positioned on the segment  20  and can force skived material against the flat surface  52  of the end cap  50 . Any skived material collected between the surface  52  and the segment  20  can prevent the end cap  50  from fitting properly flat against the lead-end of the segment  20 . Accordingly, the disclosed end cap  50 , as best shown in the bottom view of  FIG. 6B , defines under-cut channels  54  on the flat surface  52  adjacent the tooth legs  82  and adjacent the body leg  88 . These under-cut channels  54  collect any skived material from the legs  82  and  88  when the end cap  50  is fit onto the segment so that the flat surface  52  of the end cap  50  can fit snugly against the lead-end of the segment. 
   As also shown in the bottom view of  FIG. 6B , the flat surface  52  of the lead end cap  50  defines a divot  57  to accommodate an interlock tab (element  37  shown in  FIG. 3A ) that is conventionally used for stacking laminations of the segment. Furthermore, the outboard edge of the body portion  60  defines passages  67  that also accommodate the other interlock tabs (elements  37  shown in  FIG. 3A ) on the segment. As best shown in  FIG. 6B , the passages  67  on the lead end cap  50  communicate a hollow  61  of the body portion  60  with the outboard edge of the end cap  50  so that the passages  67  also serve as drain holes, as described in more detail below. 
   3. Pocket Features 
   In the present embodiment and as best shown in the detailed view of  FIG. 4 , the lead end caps  50  each preferably include first and second pockets  68 + and  68 − for insulation displacement connectors (IDCs) (not shown). The IDC pockets  68 + and  68 − each have an inboard slit  69 -I and an outboard slit  69 -O. A leading portion  93 L of the wire used to form the winding coil  92  fits in one of the IDC pockets  68 +, and the trailing end  93 T of the wire  90  of the winding coil  92  fits in the other IDC pocket  68 −. In an exemplary interconnect scheme described in more detail below, a phase interconnect wire  94 A used to interconnect the winding coils between segments  20  of the same phase also fits into the one IDC pocket  68 + on the end cap  50 . In the exemplary interconnect scheme, a neutral or common interconnect wire  96  used to interconnect the common ends of the winding coils  92  of the stator fit into the other IDC pocket  68 −. Thus, the slits  69 -I,  69 -O pass the wires  90 ,  94 ,  96  through the IDC pockets  68 +,  68 − between the inboard and the outboard sides of the stator assembly  10 . 
   The outboard slits  69 -O position the wire in a defined relationship to the outboard side of the stator assembly  10  and to any exterior shell (not shown) into which the stator assembly  10  may be positioned. As best shown in the top view  FIG. 6A , posts  148  extend from the body portion  60  adjacent the outboard slits  69 -O. These posts  148  are used during winding procedures and are eventually removed during later assembly. 
   The inboard slit  69 -I of the IDC pockets  68 +,  68 − are specifically positioned to ensure that the wire  90  that forms the winding coil  92  is positioned in a defined relationship to the tooth portion  24  of the segment  20 . In particular and as best shown in  FIG. 6A , the inboard slit  69 -I of the IDC pockets  68 + is substantially aligned with the edge of the winding portion (not shown) that fits adjacent the tooth portion  24  of the segment  20 . A groove  65  is preferably formed in the body portion  60  of the end cap  50  from the slit  69 -O to the edge of the winding portion  74 . As best shown in  FIG. 4 , the groove  65  is used to guide and hide the leading portion  93 L for the winding coil  92  to the tooth portion of the segment. On the other hand and as best shown in  FIG. 6A , the inboard slit  69 -I of the other IDC pockets  68 − is positioned further from the edge of the winding portion  74 . As best shown in  FIG. 4 , the inboard slit  69 -I of the other IDC pockets  68 − receives the trailing portion  93 T of the winding coil  92 . 
   In addition to the slits  69 -I,  69 -O, the lead end cap  50  includes a connection reference walls  140  on an inboard side of the body portion  60 , as best shown in  FIG. 4 . The connection reference wall  140  is positioned away from IDC pockets  68 +,  68 − and is used to align wire with the slits  69 -I,  69 -O when positioning the wire on the stator  10  during manufacture. Edges  142  of the wall  140  are substantially aligned with the inboard slits  69 -I and are used to bend wire relative to the inboard slits  69 -I. The connection reference wall  140  also has tips or portions  144  that extend beyond the body portion  60 . The tips  144  create a reference point for aligning the wire in the slits  69 -I,  69 -O of the IDC pockets  68 +,  68 −. For example, the tips  144  of the wall  140  extends far enough beyond the body portion  60  to allow a winding probe or nozzle to bend the wire above the IDC pocket  68 +,  68 − before the wire is put into the slits  69 -I,  69 -O. Having the extending tips  144  of the wall  140  eliminates the need to have a hook extending above the body portion  60 , which could interfere with an automated winding process. 
   As best shown in  FIG. 4 , the lead end cap  50  also has alignment slots  146  adjacent each of the IDC pockets  68 +,  68 −. The alignment slots  146  facilitate automated assembly of the stator  10  by providing a reference point for aligning automated devices that embed IDCs (not shown) in the IDC pockets  68 +,  68 −. For example, the present embodiment preferably uses insulation displacement connectors (IDCs) manufactured by Tyco. The IDCs fit into the pockets  68 +,  68 −. Preferrably, the IDC pockets  68 +,  68 − have upward posts within the pockets to facilitate positioning of the IDCs. Once installed, the IDCs electrically connect the winding coil wires (e.g.,  92 ) and the interconnect wires (e.g.,  94 A and  96 ) passing through the pocket  68 +,  68 −. In addition, the IDCs provide a terminal for a wire lead to connect to the motor. The end cap  50  also includes a mounting hole  66  in which a cable tie for holding the wire lead can be snapped. 
   D. Base End Caps 
   As noted above, the discrete segments  20  of the stator  10  have base end caps  150 . Referring to  FIGS. 9A through 9C , a stator segment  20  having end caps  50 ,  150  is shown in a number of isolated views to reveal relevant details of the base end caps  150  for the disclosed stator assembly. The base end cap  150  is used on the base end of the stator segment  20  (i.e., the end of the stator segment positioned toward the oil sump or “bottom” of the motor). The base end cap  150  is substantially similar to the lead end cap discussed above. For example, the base end cap  150 , which is shown in a number of isolated views in  FIGS. 10A through 10F , includes a body portion  160 , a winding portion  174 , an inboard wall  176 , and a substantially flat surface  152 . 
   The base end cap  150  fits on the base-end of the stator segment  20  in a similar fashion to the fitting of the lead end cap on the lead-end. For example, the base end cap  150  has two tooth legs  182  attached to the inboard wall  176  and extending from the flat surface  152 . The disclosed end cap  150  also has a body leg  188  attached to the body portion  160  and extending from the bottom surface  152 . When positioned on the segment  20 , the tooth legs  182  of the base end cap  150  fit one either side of the tooth portion and against the pole end  26  with an interference fit, and the body leg  188  fits in the channel  38  formed on the outboard edge  30  of the segment  20 . The legs  182  and  188  securely hold the base end cap  150  on the segment  20 , thus not allowing the end cap  150  to move during winding procedures or other manufacturing steps. 
   Similar to the lead end cap discussed above, the base end cap  150 , as best shown in the top view of  FIG. 10A , includes under-cut channels  154  on the flat surface  152  adjacent the legs  182  and  188  for collecting skived material from the legs  182  and  188  when the base end cap  150  is positioned onto a segment. Furthermore, the flat surface  152  of the base end cap  150  defines a divot  157 , and the edge of the body portion  60  defines nooks  167  to accommodate the interlock tabs (elements  37  in  FIG. 3A ) conventionally used for stacking laminations of a segment. 
   E. Winding Procedure 
   During assembly of the disclosed stator  10 , the segments  20  are formed from a plurality of stacked laminations in a process known in the art, such as shown in  FIGS. 3A and 3B , for example. Then, the lead and base end caps  50  and  150  are positioned on the discrete segment  20 . Next, strips of MYLAR® or other such material (not shown) are attached to the sides of the tooth portions  24  of the segments  20 , as known in the art. The strips typically have an adhesive backing for attachment and provide protection and insulation for wire to be wound on the tooth portion  24 . Then, a winding coil  92 , which is schematically shown in  FIGS. 5C and 5D , for example, is formed on the segment  20 . The windings coils  92  are formed by techniques known in the art, such as fly or needle winding. Preferably, the present embodiment uses a winding technique having a spindle and bobbin where a winding coil  92  is individually wound about each discrete stator segment  20 . 
   In the present embodiment, one of benefits of the “loose” segmented stator is that the discrete stator segments  20  can be freely handled and can be individually rotated to wind with wire to form the winding coil. Thus, access to the slot area of the discrete stator segments  20  enhances precision in the winding procedure and offers denser slot fills. In addition, the access to the discrete segment  20  allows the segments  20  to be wound at high speeds. 
   Briefly, the spindle/bobbin winding technique begins by placing the segment  20  having the attached insulation strips and end caps  50 ,  150  in an arbor machine that latches onto the ends  32  and  34  of the segment  20 . A leading portion of wire is bent about the projecting post  148  on the outboard side of the lead end cap  50  to position the wire in a fixed location on the end cap  50 . The wire is then inserted into the slits  69  of the IDC pocket  68 +. The arbor machine rotates the segment  20 , and a movable wire nozzle feeds wire to the segment  20 . While the segment  20  is rotated, the wire is wound about the tooth portion  24  of the segment  20  and the winding portions  74 ,  174  of the end caps  50 ,  150  to form the winding coil  92 . 
   At completion of the coil  92 , the wire is then run out towards the outboard side of the end cap  50  through the slits  69  of the neutral IDC pocket  68 − on the lead end cap  50  where the wire is then trimmed. Preferably, the wire is bent at an angle from the outboard slit  69 -O to prevent the wire from coming out of the pocket  68 − after trimming. As those of skilled in the art will appreciate, winding a coil about a tooth portion  24  of a segment  20  in a given direction achieves an electromagnet of a polarity when the winding is energized in that given direction. Such a winding process is repeated individually on the various segments  20  for the stator. 
   As schematically shown in  FIGS. 5C and 5D , wire of the winding coil  92  is wound so that portions of the winding coil  92  are also partially positioned between the body portions  60 ,  160  and the inboard walls  76 ,  176  of the end caps  50 ,  150 . The wire of the winding coil  92  is also wound so that portions of the coil  92  are partially positioned between the legs  82 ,  182  and the yoke portion  22  of the segment  20 . The distal ends of opposing legs  82  and  182  on the lead and base end caps  50  and  150  preferably substantially meet one another so as to not allow metal of the pole end  26  to be substantially exposed, as best shown in  FIGS. 5C and 5D . Thus, the legs  82  and  182  add substantial insulation for the winding coil  92  from the metal that forms the pole end  26  of the segments  20 . 
   To facilitate winding of the wire during the winding procedure, the lead end cap  50 , as best shown in the side views of  FIGS. 6D and 6F , has a winding pocket  70  that gives a substantially constant slot dimension about the end cap  50  and tooth portion (not shown) of a segment when positioned thereon. The body portion  60  on the lead end cap  50  has an inboard side that is substantially perpendicular to the winding portion  74  that fits onto the tooth portion of the segment. The inboard wall  76  has an outboard side that is substantially perpendicular to the winding portion  74  and that opposes the inboard side of the body portion  60 . 
   An angled surface  75  of the end cap  50  angles from the winding portion  74  to the inboard side of the outboard wall  76 . The angled surface  75  is configured to position wire of the winding coil (not shown) in the slot area between the body portion  60  and inboard wall  76 . Furthermore, the tooth legs  82  each have an angled surface  85  on an outboard side of the legs  82 . The angled surface  85  angles from a side of the tooth portion (not shown) of the segment. This angled surface  85  is similarly configured to position wire of the winding coil in the slot area between the pole end  26  and the yoke portion  22  of the segments, as shown in  FIGS. 5C and 5D , for example. 
   The wire pocket  70  of the end cap  50  is contoured to have substantially the same cross-sectional slot area in both the axial and circumferential directions. As shown in  FIG. 6D , the angled surface  75  near the inboard wall  76  defines an angle α 1 . As shown in  FIG. 6B , the angled surfaces  85  on the legs  82  defines an angle α 2 . The angle α 1  is preferably substantially equivalent to the angle α 2 . In addition, these angled surfaces  75  and  85  preferably transition smoothly where they meet with one another so that the transition between the angled surfaces also define the same angle as angles α 1  and α 2  relative to the tooth portion of the segment. In one embodiment, the angles α 1  and α 2  are about 110-degrees. 
   As shown in  FIGS. 3A and 3B , for example, the sides of the tooth portion  24  are preferably substantially perpendicular to the lead-end and base-end of the segment  20 . As noted above, the bottom surface  52  of the lead end cap  50  is positioned parallel against the lead-end of the segment, and the edges of the winding portion  72  are aligned with the edges of the tooth portion of the segment. Because the wire pocket  70  of the end cap  50  is contoured to have substantially the same cross-sectional slot area in both the axial and circumferential directions. Thus, the wire is given a substantially constant slot dimension as the segment  20  is rotated during a winding procedure. As a result, the wind of the winding coil on the segment can be performed faster, tighter, and more consistently. In addition, the wire forming the winding coil can comfortably fall into place in the wire pocket  70  as the wire is layered during the winding procedure and can reduce or eliminate “wire collapse” and cross over of the wire in the coil during the winding procedure, which achieves a denser winding coil. 
   To facilitate winding of the wire during the winding procedure, the base end cap  150 , as best shown in the side views of  FIGS. 10D and 10F , also has a winding pocket  170  that gives a substantially constant slot dimension about the end cap  150  and tooth portion (not shown) of the segment when positioned thereon. The winding pocket  170  is substantially similar to that disclosed above for the lead end cap. For example, the body portion  160  on the base end cap  150  has an inboard side that is substantially perpendicular to the winding portion  174  that fits onto the tooth portion of the segment. The inboard wall  176  has an outboard side that is substantially perpendicular to the winding portion  174  and that opposes the inboard side of the body portion  160 . An angled surface  175  of the end cap  150  angles from the winding portion  174  to the inboard side of the outboard wall  176  to position wire of the winding coil. Furthermore, the tooth legs  182  each have an angled surface  185  on an outboard side of the legs  182  to position wire of the winding coil. As with the lead end cap described above, the angled surfaces  175  and  185  are similarly configured to position wire, and each surface  175  and  185  defines a substantially equivalent angle with respect to the tooth portion. 
   F. Mechanical Assembly of Stator 
   After the segments  20  are individually wound according to certain teachings of the present disclosure detailed herein, the individually wound segments  20  are assembled into a generally annular configuration to form the stator. As noted in the Background Section of the present disclosure, some segmented stator assemblies use interlocking features or hinges on the segments to hold them together. In another type of segmented stator assembly, co-pending U.S. patent application Ser. No. 10/427,450, entitled “Segmented Stator With Improved Handling And Winding Characteristics And Method Of Winding The Same” and filed Apr. 30, 2003, which is incorporated herein by reference in its entirety, discloses a segmented stator assembly that uses flexible containment structures on the segments to hold them together. In contrast, the stator segments  20  of the present embodiment preferably have the ridged and slotted ends  32  and  34  that are positioned into physical contact with one another to form a closed magnetic circuit, and no direct, segment-to-segment attachment exists between the stator segments  20 . 
   1. Coupling between End Caps 
   As noted in the Background Section of the present disclosure, typical “loose” segmented stators (e.g., those stators with segments that do not interlock together by a hinge) need a heavy band that is typically made of metal to be placed around the outside of the segments to hold the segments together, especially during the manufacturing process. In the present embodiment, however, respective ends  62 / 64  and  162 / 164  of the disclosed end caps  50  and  150  couple together to interconnect or substantially hold the individually wound stator segments  20  together. The respective ends  62 / 64  and  162 / 164  of the disclosed end caps  50  and  150  can be coupled together by hand or by automation. On the lead end cap  50  best shown in  FIGS. 5A-5D , one end  62  of the end cap body portion  60  preferably includes a male coupling  62 , and another end  64  preferably includes a female coupling  64 . The male and female coupling  62  and  64  are preferably features incorporated into the body portion  60  of the end cap  50 . The male coupling  62  preferably extends from the end of the body portion  60  adjacent a slotted end  32  of the yoke portion  22  of the segment  20 . In addition, the female coupling  64  is preferably defined in the end of the body portion  60  positioning adjacent the ridged end  32  of the yoke portion  22 . 
   These male and female couplings  62  and  64  mate together between adjacent end caps  50  to substantially hold the segments  20  together, as best shown in  FIG. 4 , for example. In the present embodiment, the male and female couplings  62  and  64  are snap features. The male coupling  62  includes deformable, bifurcate catches, and the female coupling  64  includes a grooved slot. When the pressed into the female coupling  64 , teeth on the ends of the bifurcate catches  62  engage inside the grooves of the female coupling  64 . The male and female couplings  62  and  64  eliminate the need for a heavy metal band or any other special fixture to independently hold the segments together during manufacturing or during transportation of the assembled stator. 
   In alternative embodiment illustrated in  FIGS. 7A and 7B , ends  62 ′ and  64  of adjacent end caps  50 ,  50 ′ can couple together using a separate C-clamp  100 . The ends  62 ′,  64  of the adjacent end caps  50 ,  50 ′ can each define a pocket  102 . The separate C-clamp  100 , which can be stainless steel, for example, can fit within the pockets  102  of the adjacent end caps  50 ,  50 ′ to couple them together. The pockets  102  can each include a retaining rib  103  formed on the inner wall of the cavity  61  of the end caps  50 ,  50 ′. The retaining ribs  103  can engage the C-clamp  100  and can hold it in place. In contrast to the retaining ribs  103  and as shown in  FIG. 7B , the pockets  102  can each include a retaining slot  103 ′ formed on the inner wall of the cavity  61  of the end caps  50 ,  50 ′. The C-clamp  100 ′ can have hooked ends that can fit within the retaining slots  103 ′ to hold the clamp  100 ′ in place. The slots  103 ′ can be elongated along the height of the end caps  50 ,  50 ′ to allow for adjustment between the adjacent end caps  50 ,  50 ′ due to differences in tolerances from the laminated segments  20 ,  20 ′ and end caps  50 ,  50 ′. 
   In another alternative embodiment illustrated in  FIGS. 8A and 8B , ends  62 ′,  64  of the adjacent end caps  50 ,  50 ′ can couple together using a separate cotter pin  104 . One end  62 ′ of an adjacent end cap  50 ′ can include a stem  107  that extends from the side of the end cap  50 ′ and that has a retaining hole  108 . The other end  64  of the adjacent end cap  50  can define a hole  105  in which the cotter pin  104  inserts. The stem  107  on the one end cap  50 ′ can fit into an opening  106  in the sidewall of the adjacent end cap  50 . The cotter pin  104  can then be fit through the hole  105  of the end cap  50 , and the end of the cotter pin can connect into the hole  108  in the stem  107 . In this way, the cotter pin  104  and stem  107  can substantially hold the adjacent end caps  50 ,  50 ′ together. Moreover, the opening  106  in the sidewall through which the stem  107  inserts can be elongated along the height of the end caps  50 ,  50 ′ to allow for adjustment between the adjacent end caps  50 ,  50 ′. 
   2. Alignment Features 
   As best shown in  FIGS. 9A through 9C , the base end cap  150  similarly has ends  162  and  164  that mate together to hold adjacent segments  20  together. The ends  162  and  164  in the present embodiment are substantially similar to those on the lead end cap described above. In addition to the mating ends  162  and  164 , the base end cap  150  has a feature for aligning adjacent segments  20 . The alignment feature includes an alignment slot  192  on one end of the body portion  160  and includes an alignment finger  194  on another end. 
   Preferably, the finger  194  extends from the end of the body portion  160  having the female coupling  164 . The finger  194  extends from the body portion  60  for inserting into the slot  192  of an adjacent base end cap  150 . As best shown in  FIG. 10C , the alignment finger  194  has a side  195  that is substantially on the same plane as the substantially flat surface  152  of the end cap  150 . When the base end cap  150  is positioned on a segment, the side  195  of the finger  194  lies on substantially the same plane as the base-end of the segment. Preferably, the slot  192  is defined in the same side of the body portion  160  having the male coupling  162 . As best shown in  FIG. 10A , the alignment slot  192  is open toward the end of the end cap  150  for inserting a finger  194  of an adjacent base end cap  150 . In addition, the alignment slot  192  has an open side  193  towards the flat surface  152  of the base end cap  150 . When the base end cap  150  is positioned on a segment, the open side  193  of the slot  192  exposes the base-end of the segment. 
   Referring to  FIG. 11 , lead and base end caps  50  and  150  are shown coupled together on adjacent segments  20  of an assembled stator. The end caps  50 ,  150  on the various segments  20  of the stator may have different tolerance values. In addition, the stack heights of the various segments  20  can vary as much as plus or minus two (2) lamination thicknesses per stack, which can be caused by variations in the plurality of laminations used to form the segments  20 . Differences in tolerances and stack heights can create unevenness in the axial direction A (e.g., the direction generally parallel to a central axis of the assembled stator) when the various segments  20  are put together to assemble the stator. For illustrative purposes, the adjacent segments  20  in  FIG. 11  are shown with different stack heights SH 1  and SH 2 . 
   The disclosed end caps  50  and  150  have features to overcome differences in tolerances and stack heights. When the base end caps  150  of the adjacent segments  20  are brought together, the finger  194  on one end cap  150  fits within the slot  192  on the adjacent end cap  150 . The end of the finger  194  is preferably chamfered as shown because the finger  194  inserts into the slot  192 . When positioned in the slot  192 , the side  195  of the finger  194  positions against the substantially flat, base surface  28  of the adjacent segment  20  exposed by the open side (not labeled) of the slot  192 . As a result, the substantially flat, base surfaces  28  of the adjacent segments  20  lie substantially on the same plane P. 
   In addition, the male and female couplings  62 , 64  and  162 , 164  can adjust relative to one another in the axial direction A when the end caps  50  and  150  are mated together. In particular and as best shown in  FIGS. 5A-5D  or  9 A- 9 C, the male and female couplings  62 , 64  and  162 , 164  are formed substantially along the height of the end caps  50  and  150 , and the female couplings  64  and  164  are open ended in the axial direction. Thus, the male and female couplings  62 , 64  and  162 , 164  can adjust relative to one another in the axial direction once mated together to accommodate for differences in tolerances and stack heights between the various segments  20  and end caps  50 ,  150  of the stator when assembled. 
   Furthermore, the male and female couplings  62  and  64  on the lead end caps  50  preferably do not extend to the substantially flat surface on the bottom of the lead end cap  50 , as shown in  FIG. 11  and also in  FIGS. 6B-6F . In this way, undercuts, generally indicated as  63 , are formed beneath the couplings  62  and  64 . With the adjacent segments  20  and lead end caps  50  coupled together as shown in  FIG. 11 , these undercuts  63  provide space for any differences in tolerances or stack height between the adjacent segments  20 . Thus, if one segment  20  has a greater stack height SH 1  than the stack height SH 2  of the adjacent segment  20 , the coupling  62  or  64  on the adjacent end cap  50  will not contact the top of the greater stacked segment  20 . Instead, the undercut  63  will accommodate any excess stack height on the greater stacked segment  20 . 
   These features of the disclosed end caps  50  and  150  can reduce the effects of certain problems associated with a segmented stator. In one exemplary problem, unevenness in the segmented stator can cause problems when a shell is pressed on the stator during manufacture. The shell may hit certain segments  20  first, causing the segments  20  to possibly pull away from each other or possibly forcing the shell to be improperly pressed on the stator. The alignment slots  192  and fingers  194  on the base end caps  150  provide the assembled stator with a substantially level base for holding the stator when pushing a shell over the stator. In another exemplary problem associated with a segmented stator, tolerance values of the various components of the stator, motor, and compressor can accumulate during manufacture. Aligning the base end cap  150  and base surfaces  28  of the segments  20  with the alignment slots  192  and fingers  194  provides a reference point for tolerances. In this way, the manufacturer can better accommodate or control the stacking of tolerance values when building the stator, motor, and compressor. 
   Furthermore, aligning the base end cap  150  and base surfaces  28  of the segments  20  can reduce unevenness in the segmented stator that can cause problems when the motor is stitched with interconnect wire, as described below. As alluded to in the Background Section of the present disclosure, any unevenness of the segmented stator  10  can cause problems when the stator  10  is stitched. An automated stitching device may place a force on each individual laminated segment  20  as the stator is positioned to perform the interconnections between the segments  20 . If one of the segments  20  were “up” from the lower supporting datum (e.g., the base surface of the one segment  20  is above the general plane P of the other segments  20 ), the force of the stitch operation could cause the segment  20  to move and can possibly create a mis-stitch or scrap part. Having the segments  20  lie substantially on one plane P as discussed in  FIG. 11  and supporting the stator  10  from that plane P or a plane parallel thereto during the stitching operation can substantially avoid any of these manufacturing issues. For this reason, the consistent datum between each of the individual segments  20  provided by the alignment slots and fingers  192  and  194  can be beneficial. 
   G. Wire Isolation 
   As noted above in the Background Section of the present disclosure, all three types of Induction, BPM, or SR motors can have phase-on-phase issues where adjacent wires of opposing electrical phases produce a large voltage differential between the adjacent wires. Such phase-on-phase issues can be aggravated when the motor is used as a magnetization fixture having large voltages and amps passed through the stator at one given instant. In addition, a drive (not shown) operates to control energization of the winding coils of the stator  10 . In one embodiment, a Pulse Width Modulated (PWM) drive can be used with the disclosed stator assembly  10 . However, other conventional techniques for controlling the energization of the winding coils can be used. As noted above, phase-on-phase issues can be aggravated when a PWM drive is used to drive the motor, because the waveform from the PWM drive may have high voltage spikes on the leading and trailing edges of the wave form, creating a need to separate the phases. 
   In the present embodiment, conventional insulation is preferably used between adjacent winding coils  92 . As noted previously, however, prior art solutions not only use insulation between adjacent winding coils but also use additional insulation, such as MYLAR® or NOMEX® sheets and tubes, between adjacent interconnect wires to potentially reduce effects of phase-on-phase issues. Unfortunately, the additional insulation increases the cost and time of manufacturing the motor. As also noted previously, prior art solutions may simply route wire on the outside of the stator to interconnect the winding coils of the various phases. In addition, prior art solutions may merely use posts on the end caps to bend wire or may use rings with various hooks to route wire between the coils. Such prior art solutions allow wires of different phases to pass next to each other or even touch, which can produce undesirable phase-on-phase issues. 
   1. Routing Features on Lead End Caps 
   In the present embodiment, the lead end cap  50  includes a plurality of wire isolation features for routing and separating the interconnect wires. In contrast to the prior art, the wire isolation features are intended to substantially eliminate or reduce such phase-on-phase issues between adjacent interconnect wires without the use of additional insulation by keeping the interconnect wires of any given phase from touching another wire of a different phase or from positioning substantially close to another wire of a different phase. In one example, the wire isolation features create a minimum of 0.030-inch (one wire diameter) air clearance between adjacent interconnect wires. In addition, the wire isolation features on the disclosed end caps  50  are designed for automated stitching. In the present embodiment of the lead end cap  50 , as shown in  FIGS. 5A-6F , the wire isolation features include an inboard router or hook  110 , an outboard router or hook  120 , and another inboard router or wall shelf  130  positioned on the disclosed end cap  50 . 
   a. Inboard Hook 
   As best shown in  FIG. 5B , for example, the inboard hook  110  is positioned on the inboard wall  76  of the lead end cap  50  and extends from one side edge of the inboard wall  74 . The inboard hook  110  has a high ledge  112 , a low ledge  114 , and a catch  116 . The high ledge  112  routes wire a further distance from the segment  20  of the stator, and the low ledge  114  routes wire a closer distance from the segment  20  of the stator. Thus, the high and low ledges  112 ,  114  on the inboard hook  110  separate interconnect wires routed from one portion of the stator to another. The catch  116  positions the interconnect wires on the ledges  112 ,  114  and can used to bend the interconnect wire. 
   b. Outboard Hook 
   As shown in  FIG. 5C , for example, the outboard hook  120  is positioned on the body portion  60  of the lead end cap  50  adjacent one of the IDC pockets  68 +. The outboard hook  120  extends beyond the body portion  60  and has a high ledge  122  and a low ledge  124 . The high ledge  122  routes interconnect wire a further distance from the segment  20  of the stator, and the low ledge  124  routes interconnect wire a closer distance from the segment  20  of the stator. Thus, the high and low ledges  122 ,  124  on the outboard hook  120  separate interconnect wires routed from one portion of the stator to another. The high ledge  122  preferably defines a notch  126  for positioning the wire on the high ledge  122 . As noted above, the end cap  50  is preferably injection molded without the need of side pulls during the molding process so that the surfaces of the end cap  50  can be formed from two dies that are pulled apart. To form the low ledge  124  that passes adjacent to the body portion  60 , a window  125  (shown in  FIGS. 6A and 6B ) is defined in the body portion  60  adjacent the low ledges  124 . The window  125  communicates with the hollow  61  of the body and allows the end cap  50  to be molded without the use of a side pull, which can reduce the time and costs associated with manufacturing. 
   c. Wall Shelf 
   As best shown in  FIG. 5A , for example, the wall shelf  130  is positioned on the outboard side of the inboard wall  76 . In the present embodiment, the inboard wall  76  is relatively higher than found on existing end caps and is intended to prevent interconnect wire from interfering with the rotating rotor (not shown). In addition, the high inboard wall  76  helps guide the interconnect wires so that they do not touch one another. The wall shelf  130  includes a high ledge  132  and a low ledge  134  for separating interconnect wire routed past the inboard wall  76  from one portion of the stator to another. The high ledge  132  routes interconnect wire a further distance from the segment  20  of the stator, and the low ledge  134  routes interconnect wire a closer distance from the segment  20  of the stator. The high ledge  132  is preferably positioned adjacent the inboard hook  110  on the side edge of the inboard wall  76 , and the low ledge  134  is preferably positioned adjacent an opposite side end of the inboard wall  76 . While winding the phases of the motor, the interconnect wires are able to rest on the wall shelf  130  on the inboard wall  76 , which can prevent the interconnect wires from interfacing with the rotor while the wire is tightened. 
   2. Exemplary Stitching Operation 
   With the individually wound segments  20  fit together, the assembled stator can proceed through the manufacturing processes without the need for a shell or metal band to hold the segments  20  together. As shown in  FIG. 1 , a conventional plastic cable tie  12  can be positioned about the stator assembly  10  for temporary retention of the stator assembly during further manufacturing steps. 
   In a further manufacturing step, the various winding coils of the segments are interconnected to form a desired phase arrangement of the motor. A number of techniques for connecting the winding coils of a segment stator are known and used in the art. In the present embodiment, however, a stitching process is used to electrically connects the individual winding coils to form the desired phase pattern. The stitching process can be done manually or automatically by techniques known in the art. Preferably, the stitching process for the disclosed stator  10  is preformed by an automated stitching device for positioning interconnect wire on the stator to interconnect the winding coils. Details of an automated stitching device and stitching techniques are disclosed in co-pending U.S. patent application Ser. No. 10/193,515, filed Jul. 11, 2002 and entitled “Improved Interconnection Method for Segmented Stator Electric Machines,” which is incorporated herein by reference in its entirety. 
   Briefly, the automated stitching device may be similar to conventional winding equipment used to wind the individual stator segments, because the mechanisms for routing the interconnect wires are substantially similar to those used for winding wire around the segments. The automated stitching device is preferably a computer numerical controlled (CNC) machine. The automated stitching device can have a wire nozzle to feed wire, a stationary or movable spindle to position the wire, and a rotating or stationary mount for supporting the stator, for example. The needle and/or the stator are moved in a programmable fashion to position interconnect wires from end cap to end cap on the stator. For example, the automated stitching device can be moved by a controller and motor arrangement, while the stator is held stationary. On the other hand, the automated stitching device can be stationary, while the stator is positioned by a controller and motor arrangement. Alternatively, both the automated stitching device and the stator can be moved by controller and motor arrangements. 
   To avoid phase-on-phase issues, the inboard hooks  110 , outboard hooks  120 , and wall shelves  130  on the lead end caps  50  are used in the automated stitching operation to connect the various phases of the motor. The automated stitching operation may use a wire nozzle, which can have a 4-mm diameter, to position interconnect wire between the various end caps  50 . Because wire nozzle may require extra spacing for internal clearances as the nozzle is moved relative to components of the stator  10 , the features of the lead end cap  50  preferably provide at least 4-mm clearance for passage of such a wire nozzle. 
   In  FIGS. 12A through 12D , preferred steps of a stitching operation on the disclosed stator assembly  10  are schematically illustrated. As shown in  FIG. 12A , the present example of the disclosed stator assembly  10  has nine stator segments that are numbered consecutively in a clockwise direction. Each segment  20  of the stator  10  is identified with a label identifying a phase of a winding coil on the segment  20 . The winding coils are not shown in  FIGS. 12A through 12D  for clarity. Having nine segments  20  in the present embodiment, each phase winding A, B, C includes a winding coil wound about the tooth portion of three stator segments  20  that are alternatingly positioned about the stator  10 . The number of segments and the number of phases in  FIGS. 12A through 12D  are only exemplary, and other arrangements can be used without departing from the teachings of the present disclosure. 
   a. Phase-C Interconnect 
   When the segments  20  are initially formed into the annular stator  10  as shown in  FIG. 12A , the winding coils (not shown) of the phases A, B, C are not electrically connected to one another. A first stitching step to connect the winding coils for the exemplary stator assembly  10  involves connecting the phase C winding coils in a reverse direction (e.g., counterclockwise in the example). In the Figures that follow, any stitched interconnect wires between steps are not shown for clarity. In addition, any excess portion of wire used in the stitching operation that is eventually removed is also not shown for clarity. In this first stitching step, portion of the phase-C interconnect wire  94 C is positioned through the pocket IDC+ on the end cap for segment S- 3 . As noted above, a leading portion of the winding coil  92  for S- 3  is already routed through pocket IDC+ so that the phase-C interconnect wire and the wire for the winding coil can be electrically connected by an IDC (not shown) that will be positioned in the pocket IDC+ during later stages of assembly. 
   From the pocket IDC+ on S- 3 , the interconnect wire  94 C is then routed in the counterclockwise direction to the low outboard ledge  124  on S- 3 , past the outboard wall on S- 2 , to low inboard ledge  114  on S- 1 , and to low inboard ledge  114  on S- 9 . At S- 9  having phase C, the interconnect wire  94 C is routed around the edge  142  of the connection reference wall and positioned through the slits in pocket IDC+. Next, the wire  94 C is routed to low outboard ledge  124  on S- 9 , past the outboard wall on S- 8 , to low inboard ledge  114  on S- 7 , and to low inboard ledge  114  on S- 6 . At S- 6  also having phase C, the wire  94 C is routed around the edge  142  of the connection reference wall and positioned through the slits in pocket IDC+. Thus, the phase-C interconnect wire  94 C interconnects all of the pockets IDC+ of the segments S- 3 , S- 9 , S- 6  for phase C. The phase-C interconnect wire  94 C is eventually trimmed on the outboard sides of the end caps  50  at the outboard slits of pockets IDC+ on S- 3  and S- 6 , and the stitching procedure continues to the next steps. 
   b. Phase-B Interconnect 
   As shown in  FIG. 12B , a subsequent stitching step involves connecting phase B in a reverse direction (e.g., counterclockwise in the example). In this stitching step, portion of the phase B interconnect wire  94 B is positioned through pocket IDC+ on the end cap for segment S- 2 . The wire  94 B is then routed in the counterclockwise direction to low outboard ledge  124  on S- 2 , past the inboard wall on S- 1 , to high inboard ledge  112  on S- 9 , and to high inboard ledge  112  on S- 8 . At S- 8  having phase B, the wire  94 B is routed around the edge  142  of connection reference wall and positioned through the slits in pocket IDC+. Next, the wire is routed to low outboard ledge  124  on S- 8 , past the outboard wall on S- 7 , to high inboard ledge  112  on S- 6 , and to low inboard ledge  114  on S- 5 . At S- 5  also having phase B, the wire  94 B is routed around the edge  142  of connection reference wall and positioned through pocket IDC+. Thus, the phase-B interconnect wire  94 B interconnects all of the pockets IDC+ of the segments S- 2 , S- 8 , S- 5  for phase B. The interconnect wire  94 B is eventually terminated at the outboard slits of pockets IDC+ on S- 2  and S- 5 . 
   c. Phase-A Interconnect 
   As shown in  FIG. 12C , a next step of the process involves connecting phase A in a reverse direction (e.g., counterclockwise in the example). In the stitching step, portion of the phase A interconnect wire  94 A is positioned through pocket IDC+ on the end cap for segment S- 7 . From pocket IDC+, the interconnect wire  94 A is routed in the counterclockwise direction past the inboard wall on S- 6 , to high inboard ledge  112  on S- 5 , and to high inboard ledge  112  on S- 4 . At S- 4  having phase A, the wire  94 A is routed around the edge  142  of the connection reference wall and positioned through the slits in pocket IDC+. Form pocket IDC+, the wire is routed to low outboard ledge  124  on S- 4 , past the inboard wall on S- 3 , to high inboard ledge  112  on S- 2 , and to high inboard ledge  112  on S- 1 . At S- 1  also having phase A, the wire  94 A is routed around the edge  142  of the connection reference wall and positioned through the slits in pocket IDC+. Thus, the phase-A interconnect wire  94 A interconnects all of the pockets IDC+ of the segments S- 1 , S- 4 , S- 7  of phase A. The interconnect wire  94 A is eventually terminated at the outboard slits of the pockets IDC+ on S- 1  and S- 7 . 
   d. Common Interconnect 
   As shown in  FIG. 12D , a neutral or common interconnect wire  96  is connected in a forward direction. In this stitching step, portion of the common interconnect wire  96  is positioned in the common pocket IDC− on the end cap for segment labeled S- 1 . As noted above, a trailing end of the wire for the winding coil of segment S- 1  is also positioned through pocket IDC− so that the interconnect wire  96  and the wire of the winding coil can be electrically connected by an IDC (not shown) that will be positioned in the pocket IDC− during later stages of assembly. From the pocket IDC−, the wire  96  is then routed in the clockwise direction around the edge  142  of the connection reference wall on segment S- 2 , positioned in pocket IDC− on S- 2 , to high outboard ledge  122  on S- 3 . The same routing steps for the common interconnect wire  96  are then repeated on each of the segments S- 3  through S- 9 . Thus, the common interconnect wire  96  interconnects all of the neutral pockets IDC− of the segments S- 1  through S- 9 . The interconnect wire  96  is eventually terminated at the outboard slits of neutral pockets IDC− on segments S- 1  and S- 9 . 
   In  FIGS. 12A-12D , the preferred stitching patterns for the phase and common interconnect wires to connect the winding coils into the desired phase arrangement are only exemplary. Other stitching patterns can be used without departing from the teachings of the present disclosure. In one example, one or more of the above stitching patterns for the phases may be performed in an opposite direction around the stator  10 . For example, another stitching pattern can involve first connecting phase C winding coils of  FIG. 12A  in a forward direction (e.g., clockwise), second connecting phase B winding coils of  FIG. 12B  in a backward direction (e.g., counterclockwise), third connecting phase A winding coils of  FIG. 12C  in a forward direction, and lastly connecting the neutral ends of all the winding coils of  FIG. 12D  in a backward direction. Furthermore, with the benefit of the present disclosure and the exemplary stitching pattern disclosed above, a person skilled in the art can develop such a pattern for a stator having more or less segments and/or more or less phases than those of the exemplary embodiment. 
   e. Positioning of IDCs and other Assembly Steps 
   After stitching the interconnect wires as described above, IDCs are positioned in the IDC pockets IDC+, IDC− and forced onto the wires positioned through the pockets IDC+, IDC−. As is known in the art, IDCs electrically connect the plurality of wires positioned in the IDC pocket and provide a terminal coupling for connecting to a terminal end of the wire leads for the phases. Preferably, insulation displacement connectors (IDCs) manufactured by Tyco are used with the disclosed stator assembly  10  and end caps  50 . Excess portions of the interconnect wire as well as the posts  148  on the outboard side of the stator  10  are trimmed, and the stator  10  may be positioned in a shell. 
   Final assembly steps involve connecting power leads to the stator assembly. For a three phase machine, for example, ¼-inch IDCs can be inserted into three of the IDC pockets IDC+ on the lead end caps  50 , such as those on the end caps of segments S- 1 , S- 2 , and S- 3 . Terminal connectors on the ends of three power leads can then be connected to these ¼-inch IDCs. Finally, the power leads can be attached to the stator assembly using poke-in tie wraps having ends that insert into the holes ( 66  in  FIG. 12D ) in the lead end caps  50 . 
   H. Scalloped Stator 
   In addition to the features disclosed above, the disclosed segmented stator  10  includes additional features related to the contour of the stator  10 , oil cooling and draining, material efficiency, and uniform fit of the stator  10  in a shell. As discussed in the Background Section of the present disclosure, hermetic motors used in compressors have an oil pump on the bottom of the compressor, known as the oil sump. Typically, the oil is pumped up through a hollow in the rotor shaft, past the motor, and to the main bearing. After lubricating the main bearing, the oil is let loose on the lead-end or “topside” of the motor to drain back to the oil sump. 
   Returning oil is substantially prevented from returning through the bore  11  of the stator  10  due to the winding coils  92  and the rotating rotor. Therefore, the outboard contour of the stator  10  can play a significant role in how the oil is allowed to return to the oil sump from the lead-end of the motor. If there is not enough drain area in the motor, for example, the oil can become dammed on the topside of the motor, causing higher oil circulation in the refrigeration system, starvation of oil to the pump, and poor performance of the compressor due to the compression of oil rather than gas in the system. On the other hand, if there is too much drain area in the stator, then the stator may be formed with less stator back iron than desired, which can create higher magnetic flux saturation in the stator core and can reduce the performance of the motor. 
   Referring to  FIG. 13 , flux density paths are schematically illustrated on an exemplary embodiment of the disclosed segmented stator  10  according to certain teachings of the present disclosure. In the present example, the disclosed stator  10  includes nine segments  20 . The segments  20  are electrically connected together into the annular shape of the stator  10  and contained in a shell S, which is shown in outline in the  FIG. 13 . The segments  20  have winding coils (not shown) that are wound about their tooth portions  24  and that are separated by insulation material, such as plastic strips. The pole ends  26  of the segments  20  define a bore  11 , and a rotor  14  is positioned within the bore  11  for rotation relative to the stator  10 . In the present embodiment, the rotor  14  includes a plurality of interior permanent magnets  16  and can be similar to the rotors disclosed in U.S. patent application Ser. No. 10/229,506, entitled “Permanent Magnet Machine” and filed Aug. 28, 2002, which is incorporated herein by reference in its entirety. 
   Each segment  20  of the stator assembly  10  in the present embodiment includes features for oil draining. In contrast to the use of flat portions or cutaways on the outside of a stator as is typically done in the prior art, each segment  20  defines a scalloped contour  36  formed in the outside edge  30  of the segment. Consequently, the disclosed stator  10  formed from the plurality of segments  20  has a plurality of such scalloped contours  36  arranged symmetrically around the outside of the stator  10 . The scalloped contours  36  in the segments  20  of the stator  10  provide a symmetrical drain area around the circumference of the stator  10  and shell S for oil to drain past the motor. The symmetrical drain area may also provide the additional benefit of uniform motor cooling. 
   Referring to  FIG. 14 , an embodiment of a segment  20  for the disclosed stator assembly is shown in plan view relative to the circumference of the shell S. The circumference of the shell S is defined by a large radius R 1 , and the pole end  26  of the segment  20  is defined by a smaller, concentric radius R 2 . The tooth portion  24  of the segment  20  has a width W. Preferably, the scalloped contour  36  is defined in the outboard edge  30  of the segment  20  by a third radius R 3 . The segment  20  is preferably symmetrical about a central line C, except for the ridged and slotted ends  32  and  34 . 
   1. Contact Area 
   The amount of contact area between the stator  10  and the circumference of the shell S is one concern in designing the scalloped contour  36  of the disclosed segment  20 . In  FIG. 13 , for example, at least a minimum contact area is required between the outboard edges  30  of the plurality of segments  20  and the shell S that holds the stator  10  in place. Typically, the contact area of about 18-25% of the total circumference of the shell S is desired to hold the stator  10  in place. As shown in  FIG. 14 , the outboard edge  30  of the disclosed segment  20  contacts the circumference of the shell S with a contact area A 1 +A 2 . Therefore, the scalloped contour  36  is preferably formed in the segment  20  so that the contact area A 1 +A 2  between the outboard edge  30  and the circumference of the shell S is about 18-25% of the entire angular expanse of the segment  20 . In this way, the stator  10  of  FIG. 13  formed from the plurality of segments  20  can have the desired contact area between the outboard edges  30  and the shell S, and the radius R 3  of the scalloped contours  36  as shown in  FIG. 14  can also be selected to maximize the drain area A 3  provided by the contour  36 . 
   2. Shell Deformation 
   Returning to  FIG. 13 , potential deformation of the shell S by the stator  10  is another concern in designing the scalloped contours  36  on the segments  20 . Being symmetrical about the circumference of the stator  10 , the scalloped contours  36  of the segments  20  can give a superior fit between the stator  10  and shell S. Furthermore, the scalloped contours  36  being symmetrical about the circumference of the stator  10  can equally deform the shell S if potential deformation occurs. As noted in the Background Section of the present disclosure, the prior art that uses flat portions around the outboard edge of a stator. Unlike the prior art, the symmetrically arranged scalloped contours  36  on the stator  10  reduce the flat length of the stator  10  that can interferes with the shell S, which can reduces undesirable deformation of the shell S. As best shown in  FIG. 14 , the scalloped contour  36  in the segment  20  preferably has sweeping radii R 4  on both ends of the contour  36  where it meets with the outside edge  30  that contacts the shell S. The sweeping radii R 4  substantially removes sharp edges on the outboard edge  30  of the segment  20  and can potentially reduce deformation of the shell S. 
   3. Flux Density 
   In the example alignment between the rotor  14  and stator  10  shown in  FIG. 13 , the segments S- 2 , S- 5 , and S- 8  have concentrated flux paths. Maintaining a sufficient amount of back iron on the stator  10  to avoid flux saturation in the segments  20  is yet another concern when designing the scalloped contours  36  of the stator  10 . As noted above, prior art solutions can reduce the amount of back iron on a stator needed for desired performance of a motor. Not only does the present embodiment of the scalloped contours  36  give more oil drain area and substantially reduce shell deformation, but the disclosed scalloped contours  36  substantially maintain the back iron in the segments  20  at a preferred level. 
   In  FIG. 14 , the segment  20  is shown with the central line C that symmetrically divides the segment  20 . A first line P 1  is shown from an inner corner  31  of the tooth portion  24  to the central line C of the segment  20  and is substantially perpendicular to the central line C. A second line P 2  is shown from the inner corner  31  to the edge  30  of the segment  20  and is substantially parallel to the central line C. Flux paths are schematically shown in  FIG. 14  passing through the first and second lines P 1  and P 2  as the flux paths pass around the corner  31  between the tooth portion  24  and the end  32  of the segment  20 . The first line P 1  defines a cross-sectional area represented by half of the width W of the tooth portion  20 . 
   To avoid issues with saturation, the second line P 2  preferably defines a cross-sectional area at least equal to that defined by the first line P 1 . The flux paths are also shown in  FIG. 14  passing through arbitrary lines U and U′ that extend from the corner  31  of the segment  20  to the central line C and the scalloped contour  36 . To avoid issues with saturation, these arbitrary lines U and U′ preferably define cross-sectional areas at least equal to that defined by the first line P 1 . In this way, the scalloped contour  36  is formed in the segment  20  so that the portion of the segment  20  between the corner  31  and the scalloped contour  36  has a sufficient amount of back iron for the flux passing between the tooth portion  24  and the ends  32  and  34  of the segment  20 . 
   I. Drain Holes in Lead End Caps 
   Returning again to  FIGS. 6A through 6F , the lead end cap  50  in the present embodiment also includes features for oil cooling and draining. As best shown in  FIG. 6B , the body portion  60  on the lead end cap  50  defines the cavity  61  for molding purposes because the end cap  50  is injection molded from plastic. The body portion  60  also defines the mounting hole  66  for a cable tie (not shown). Not all of the mounting holes  66  on the lead end caps  50  on the completed stator assembly will have a cable tie attached. For example, on the exemplary three-phase motor, only three cable ties will be coupled in mounting holes  66 . Thus, a number of open mounting holes  66  will expose the cavities  61  of the end caps  50 . Because the motor in a hermetic compressor application is in an oil environment, oil can pass into the cavity  61  of the end cap  50  through the mounting hole  66  when the cable tie is absent. Also, oil can pass through other holes in the end cap  50 , such as the alignment holes  146  or window  125  best shown in  FIGS. 6A and 6B . Consequently, oil can collect in the cavity  61  of the end cap  50  and can accumulate on the lead-end of the stator, which is undesirable. 
   To prevent the collection of oil, the disclosed end cap  50  includes drain holes  67  along the bottom edge of the end cap  50 . Oil drawn into the cavity  61  from the exposed mounting hole  66  or other holes in the top of the end cap  50  can drain out the bottom of the end cap  50  through the drain holes  67 . The drain holes  67  substantially eliminate any pooling of oil on the lead-end of the stator segments  20  and on the top of the end cap  50 . The drain holes  67  can reduce the amount of oil caused to circulate through the compressor system by letting some of the oil to flow through the end cap  50  rather than traveling down through the bore of the stator  10 . When oil travels through the bore of the stator, the spinning motion of the rotor can force the oil back up to the top end of the compressor where the oil is then picked up by the flow of gas and circulated through the refrigeration system. Although the drain holes  67  offer a small path for returning oil to the oil sump of a compressor, it has been found that the drain holes  67  on end caps  50  of a stator assembly  10  may prevent about 1-2 ounces of oil from pooling in the end caps  50  if the drain holes  67  were not provided. In addition, it is believed that the drain holes  67  can aid in cooling of the winding coil on the segments by facilitating the drain of oil. Moreover, the drain holes  67  at the bottom edge of the end cap  50  also beneficially act as relief areas for the interlock tabs (element  37  in  FIG. 3A ) on the segment. 
   As used herein and the appended claims, reference to words, such as top, bottom, above, below, inboard, outboard, lead-end, base-end, etc. have been used merely for clarity to show the relative locations of components on the disclosed end caps and stator assembly. Such words of relative location do not limit the orientation of the components and do not limit the overall orientation or operation of the disclosed end caps and stator in a motor. 
   The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.