Patent Publication Number: US-2021167668-A1

Title: Thermally-conductive slot divider

Description:
TECHNICAL FIELD 
     The present application relates to electrical machines and, more particularly, to stators used with electrical machines. 
     BACKGROUND 
     Electrical machines use a rotor coupled with a shaft and a stator that concentrically receives the rotor. The stator includes electrical windings that receive electrical current from an electrical source. The electrical current flowing through the windings induces rotational movement of the rotor through electromagnetic induction. The flow of electrical current through the windings produces heat as a byproduct. It is helpful to remove at least some of the heat generated by the windings from electrical machines. 
     SUMMARY 
     In one implementation, a stator assembly used in an electrical machine includes a stator core having an axial length and a plurality of stator slots that each are configured to receive electrical windings; a slot liner, received by each stator slot, that includes an aperture exposing a portion of the stator core; and a slot divider, positioned adjacent to each slot liner and partitioning each stator slot, comprising an electrically-non-conductive and thermally-conductive material, wherein the slot divider extends through the aperture in the slot liner to abut the stator core thereby communicating thermal energy from the electrical windings to the stator core. 
     In another implementation, a stator assembly used in an electrical machine includes a stator core having an axial length and a plurality of stator slots that each are configured to receive electrical windings; a rotor coupled with an output shaft; a slot liner, received by each stator slot, that includes an aperture exposing a portion of the stator core and extends axially along an axis of shaft rotation beyond the stator core; and a slot divider, positioned adjacent to each slot liner and partitioning each stator slot, comprising an electrically-non-conductive and thermally-conductive material, wherein the slot divider extends through the aperture in the slot liner to abut the stator core thereby communicating thermal energy from the electrical windings to the stator core and a portion of the slot divider receives fluid from the output shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view depicting an implementation of an electrical machine with a stator assembly; 
         FIG. 2  is a cross-sectional view depicting an implementation of an electrical machine with a stator assembly; 
         FIG. 3  is another cross-sectional view depicting an implementation of an electrical machine with a stator assembly; 
         FIG. 4  is another cross-sectional view depicting an implementation of an electrical machine with a stator assembly; and 
         FIG. 5  is another cross-sectional view depicting an implementation of an electrical machine with a stator assembly. 
     
    
    
     DETAILED DESCRIPTION 
     A stator assembly used in an electrical machine, such as an electrical motor, includes a stator core having a plurality of stator slots that receive electrical windings, a slot liner positioned in each stator slot, that includes an aperture exposing a portion of the stator core, and a slot divider, received by each slot liner. The slot liners may be made of electrically insulating material whereas the slot dividers can be made from a thermally-conductive material yet electrically isolating and partition each stator slot into separate sections. The slot dividers extend through the apertures in the slot liners to abut the stator core and communicate thermal energy from the electrical windings to the stator core. The stator assembly can be used with electrical machines having a stator with concentrated windings and, optionally, electrical machines that are cooled with fluid, such as oil. Electrical machines can be implemented using any one of a number of different designs. Some electrical machine designs use stators having concentrated windings. The slot dividers can separate concentrated windings. In some implementations, oil emitted from a shaft bearing of a rotor or a shaft coupled to the rotor can be directed so that the oil flows across an outer surface of the slot divider and conduct heat away from the electrical windings. 
     Turning to  FIGS. 1-3 , an electrical machine  10  having slot liners  12  and slot dividers  14  is shown. The electrical machine  10  is an electrical motor. But the concepts described herein can also be applied to other electrical machines, such as alternators and generators. The electrical machine  10  includes a stator assembly  16 . The stator assembly  16  comprises a stator core  18  having a plurality of slots  20  that are circumferentially arranged around the stator core  18 . The stator core  18  can be made in a variety of different ways. For example, the stator core  18  can be assembled from laminated layers of a ferric material that may be referred to as lamination steel or electrical steel. The layers can be stacked together and then welded or otherwise bonded together to form a unitary item. The slots  20  can be formed in the stator core  18  between radially-inwardly-facing arms  22 . Surfaces  24  of the radially-inwardly-facing arms  22  can at least partially define a slot  20 ; the slot  20  can have an open end  26  proximate an axis (x) of rotor rotation and a closed end  28  distal to the axis (x). The number of radially-inwardly-facing arms  22 , as well as the number of slots  20 , can be selected based on the number of poles of the electrical machine  10 . The stator core  18  and the slots can have a defined axial length measured parallel to the axis (x). A rotor assembly  30  can be positioned radially-inwardly from the slots  20  and concentric with the electrical windings  32  held by the slots  20 . The rotor assembly  30  can include a plurality of permanent magnets  34  and couple with a motor shaft  36 . As alternating current (AC) electrical current flows through the electrical windings  32  included with the stator assembly  16 , a rotating magnetic field is induced in the electrical windings  32  thereby forcing angular movement in the rotor assembly  30 . The AC current can be received directly from an AC electrical power source (not shown), or supplied by converting direct current (DC) supplied by a DC electrical power source (not shown) to AC electrical current. In this implementation, the electrical machine  10  includes six slots  20  formed by six radially-inwardly-facing arms  22 . The six slots accommodate electrical windings  32  for a six-pole electric motor. However, other implementations of electrical machines are possible using a different quantity of slots and poles. The electrical windings  32  will be discussed in more detail below. 
     The slots  20  receive slot liners  12  that can insulate electrical windings  32  from the stator core  18 , including the radially-inwardly-facing arms  22  and closed end  28 . The slot liners  12  can be substantially U-shaped in a way that closely conforms with and abuts a slot surface  38 . That is, the shape of the slot liner  12  can mimic the shape of the surfaces of the radially-inwardly-facing arms and the closed end  28  of the slot  20 . After insertion into the slot  20 , an outer surface  40  of the slot liner  12  presses against the slot surface  38  and the closed end  28  thereby providing a material having a thickness that electrically insulates at least a portion of the stator core  18  from the electrical windings  32 . 
     The slot liners  12  include an aperture  42  that exposes a portion of the closed end  28  so that a slot divider  14  can be positioned in the slot  20  so that the slot divider  14  extends through the aperture  42  to abut and contact the closed end  28  thereby touching the material of the stator core  18 . The aperture  42  in the slot liner  12  can be sized and shaped to closely conform to the length and width of the slot divider  14  such that the aperture  42  encircles an outer surface of the slot divider  14 . After insertion into the slot  20 , the slot divider  14  can extend from the closed end  28  of the stator core  18  toward the axis of rotor rotation (x) bifurcating the slot  20  into a first section  44  and a second section  40 . In addition, the slot divider  14  can extend beyond the slot  20  along the axis of rotor rotation (x) so that at least a portion of the slot divider  14  extends outside of the slot  20 . The slot divider  14  can be longer than the stator assembly  16  measured along the axis of rotor rotation (x). The slot divider  14  can be constructed from an electrically non-conductive material that is also thermally conductive. That is, the slot divider  14  electrically isolates adjacent concentrated windings yet readily communicates heat away from the electrical windings. For example, the slot divider  14  can be formed from sintered metal with electrically isolated metal grains in a particular shape and cross-section. It is possible to retain the slot divider  14  in the aperture  42  using an adhesive, such as potting compound or other similar material. The slot divider  14  can conduct heat away from the electrical windings  32  and into the stator assembly  16 . 
     The slots  20  can receive the electrical windings  32  used by the stator assembly  16 . Each radially-inwardly-facing arm  22  can include an electrical winding  32  (or pole of the winding) of metal wire that encircles or is wrapped around the arm  22  and have a portion of the electrical winding  32  in the first section  44  of the slot  20  and another portion of the electrical winding  32  in the second section  44  of the slot  20 . The electrical windings  32  of the electrical machine  10  can be arranged in a concentrated winding pattern with concentrated electrical windings  32  at each radially-inwardly-facing arm  22 . The slot dividers  14  can physically isolate an electrical winding  32  wrapped around one radially-inwardly-facing arm  22  from the electrical winding  32  wrapped around another adjacent radially-inwardly-facing arm  22 . As AC electrical current is supplied to the electrical windings  32 , the rotor assembly  30  is angularly displaced relative to the stator assembly  16 . Heat is generated by the electrical winding  32  as a byproduct of AC electrical current flow. The heat can be absorbed by the slot divider(s)  14  and communicated from the electrical windings  32  to the stator assembly  16  through the aperture  42  in the slot liner  12 . It is also possible for the portion of the slot divider(s)  14  extending outside of the slots  20  of the stator assembly  16  to receive a flow of fluid that removes heat from the slot divider  14  and thereby reduces the temperature of the electrical windings  32 . For example, the motor shaft  36  of the electrical machine  10  can produce a flow of oil or other lubricant. As the motor shaft  36  rotates, the oil can move radially-outward relative to the motor shaft  36  and flow across an outer surface of the slot divider(s)  14 . The flow of oil over the outer surface can carry out a cooling effect and reduce the temperature of the electrical windings  32 . 
     Another embodiment of a slot divider  48  and a stator core  50  used with the electrical machine  10  is shown in  FIG. 4 . The slot divider  48  can include a keyed end  52  that may help couple the slot divider  48  to the stator core  50 . The slot surface  38  can include a socket  54  having a shape that closely conforms to the keyed end  52 . The slot liner  12  includes the aperture  42  that exposes the socket  54  so that the slot divider  48  can be positioned in the slot  20  so that the slot divider  48  extends through the aperture  42  and the keyed end  52  is received by the socket  54 . The depth of the socket  54  can be selected based on the magnetic flux flowing around the stator core  50  so that the presence of the slot divider  48  in the stator core minimizes interruption of the flux. In this implementation, the keyed end  52  includes a semi-circular keyway that corresponds to a semi-circular key way included in the socket  54 . The engagement of these semi-circular keyways can prevent radially-inward movement of the slot divider  48  toward the rotor assembly  30 . 
     Turning to  FIG. 5 , another implementation of a slot divider  60  and a stator core  62  used with the electrical machine  10  is shown. The slot divider  60  can include the keyed end  52  discussed above with respect to  FIG. 4 . The stator core  62  can include a raised socket  64  that extends radially-inwardly toward the rotor assembly  30  through an aperture  66 . In some implementations, the raised socket  64  can extend into the slot  20 . In this implementation, the keyed end  52  includes a semi-circular keyway that corresponds to a semi-circular key way included in the raised socket  64 . The engagement of these semi-circular keyways can prevent radially-inward movement of the slot divider  60  toward the rotor assembly  30 . 
     It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. 
     As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.