Patent Publication Number: US-2023163666-A1

Title: Hairpin wire motor stator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to China Application Serial Number 202111406869.2, filed Nov. 24, 2021, which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     Field of Invention 
     The present disclosure relates to a motor stator, and more particularly to a motor stator including hairpin wires. 
     Description of Related Art 
     U-shaped hairpin wires are often utilized in a conventional hairpin wire motor stator. U-shaped hairpin wires are inserted into slots of the motor iron core so as to realize the designs of the required winding circuits. Generally speaking, the legs of the U-shaped hairpin wire are joined at the same side of the motor iron core for the convenience of welding. However, it is not easy to adjust the span of the wires on the welding side of the motor iron core in some cases, e.g., stators with odd-numbered slot-position layers, which increases the difficulty of welding construction and consumes man-hours. In view of this, motor manufacturers are actively looking for a better wire arrangement manner to effectively reduce the man-hours and production costs required to manufacture the motor stator. 
     SUMMARY 
     The present disclosure proposes a hairpin wire motor stator for overcoming or alleviating the problems of the prior art. 
     In one or more embodiments, a hairpin wire motor stator includes a ring-shaped stator core and a plurality of slot-positions. The ring-shaped stator core defines a rotor accommodation space at a center of the stator core, wherein the stator core includes a first side and a second side opposite to the first side. The slot-positions are arranged on the stator core and surrounding the rotor accommodation space circumferentially. The slot-positions form M radially-adjacent slot-position layers, wherein M is an odd number greater than or equal to 5. A plurality of hairpin wires are arranged into the slot-positions and connected to form windings. The hairpin wires include a plurality of first U-shaped wires, each first U-shaped wire includes two leg sections located at a radially-outmost one of the slot-position layers. The hairpin wires include a plurality of second U-shaped wires, and each second U-shaped wire includes two leg sections located at a radially-innermost one of the slot-position layers. The hairpin wires include a plurality of third U-shaped wires, and each third U-shaped wire includes two leg sections located at immediately-adjacent two of the slot-position layers between the radially-outmost one and the radially-innermost one of the slot-position layers. The hairpin wires include a plurality of first straight wires, and each first straight wire includes a middle straight section located at a second radially-inner one of the slot-position layers. The hairpin wires include a plurality of second straight wires, and each second straight wire includes a middle straight section located at the radially-outmost one of the slot-position layers. 
     In one or more embodiments, each first U-shaped wire includes a U-shaped section protruding from the first side of the stator core and two leg ends protruding from the second side of the stator core, wherein each second U-shaped wire includes a U-shaped section protruding from the second side of the stator core and two leg ends protruding from the first side of the stator core, and wherein each third U-shaped wire includes a U-shaped section protruding from the first side of the stator core and two leg ends protruding from the second side of the stator core. 
     In one or more embodiments, each first straight wire includes a first leg end protruding from the first side of the stator core and a second leg end protruding from the second side of the stator core, and wherein each second straight wire includes a first leg end protruding from the first side of the stator core and a second leg end protruding from the second side of the stator core. 
     In one or more embodiments, the first leg end of the second straight wire is connected to a phase terminal or a neutral terminal, and wherein the two leg ends of the second U-shaped wire are connected with immediately-adjacent ones of the first leg ends of the first straight wires respectively. 
     In one or more embodiments, the two leg ends of the first U-shaped wire are connected with immediately-adjacent ones of the two leg ends of the third U-shaped wires respectively, and wherein the second leg end of the first straight wire is connected with immediately-adjacent ones of the two leg ends of the third U-shaped wires respectively. 
     In one or more embodiments, the stator core includes a plurality of pole regions surrounding the stator core circumferentially, each pole region includes a plurality of the slot-positions, the two leg sections of the first U-shaped wire are spaced apart by a pole pitch across the slot-positions circumferentially, and the two leg sections of the second U-shaped wire are spaced apart by a pole pitch across the slot-positions circumferentially. 
     In one or more embodiments, the first U-shaped wires include a plurality of first U-shaped wire groups configured to be disposed into corresponding ones of the slot-positions circumferentially, wherein each first U-shaped wire group includes partially-overlapped ones of the first U-shaped wires. 
     In one or more embodiments, the second U-shaped wires include a plurality of second U-shaped wire groups configured to be disposed into corresponding ones of the slot-positions circumferentially, wherein each second U-shaped wire group includes partially-overlapped ones of the second U-shaped wires. 
     In one or more embodiments, an end connection of the two leg ends of the second U-shaped wire and the corresponding immediately adjacent first leg end of the first straight wire has an axial height protruding from the stator core which is greater than an axial height of the U-shaped section of the first U-shaped wire protruding from the stator core. 
     In one or more embodiments, the first leg end of the second straight wire has an axial height protruding from the stator core which is greater than an axial height of the U-shaped section of the first U-shaped wire protruding from the stator core. 
     In one or more embodiments, an end connection of one of the two leg ends of the first U-shaped wire and corresponding immediately adjacent one of the two leg ends of the third U-shaped wire has an axial height protruding from the stator core which is greater than an axial height of the U-shaped section of the second U-shaped wire protruding from the stator core. 
     In one or more embodiments, an end connection of the second leg end of the first straight wire and corresponding immediately adjacent one of the two leg ends of the third U-shaped wire has an axial height protruding from the stator core which is greater than an axial height of the U-shaped section of the second U-shaped wire protruding from the stator core. 
     In one or more embodiments, a hairpin wire motor stator includes a stator core and a plurality of slot-positions. The stator core the stator core includes a first side and a second side opposite to the first side. The slot-positions are arranged on the stator core circumferentially to form M radially-adjacent slot-position layers, wherein M is an odd number greater than or equal to 5. A plurality of hairpin wires is configured to be arranged into the slot-positions and connected to form windings. The hairpin wires includes first U-shaped wires located at a radially-outmost one of the slot-position layers and second U-shaped wires located at a radially-innermost one of the slot-position layers. Each first U-shaped wire includes a U-shaped section protruding from the first side of the stator core and located at the radially-outmost one of the slot-position layers. Each second U-shaped wire includes a U-shaped section protruding from the second side of the stator core and located at the radially-innermost one of the slot-position layers. 
     In one or more embodiments, the plurality of hairpin wires further comprises third U-shaped wires, each third U-shaped wire includes a U-shaped section protruding from the first side of the stator core and disposed at immediately-adjacent two of the slot-position layers between the radially-outmost one and the radially-innermost one of the slot-position layers. 
     In one or more embodiments, the plurality of hairpin wires further comprises first straight wires disposed at a second radially-inner one of the slot-position layers and second straight wires disposed at the radially-outmost one of the slot-position layers, wherein the first straight wire is connected between the second U-shaped wire and the third U-shaped wire, and wherein the second straight wire is connected between a phase terminal or a neutral terminal and the third U-shaped wire. 
     In one or more embodiments, the first straight wire protrudes from the first side of the stator core to connect the second U-shaped wire and protrudes from the second side of the stator core to connect the third U-shaped wire, and wherein the second straight wire protrudes from the first side of the stator core to connect the phase terminal or the neutral terminal and protrudes from the second side of the stator core to connect the third U-shaped wire. 
     In one or more embodiments, the stator core includes a plurality of pole regions surrounding the stator core circumferentially, each pole region includes a plurality of the slot-positions, the U-shaped section of the first U-shaped wire has a span of a pole pitch across the slot-positions circumferentially, and the U-shaped section of the second U-shaped wire has a span of a pole pitch across the slot-positions circumferentially. 
     In one or more embodiments, the first U-shaped wires include a plurality of first U-shaped wire groups configured to be disposed into corresponding ones of the slot-positions circumferentially, wherein each first U-shaped wire group includes partially-overlapped U-shaped sections of the first U-shaped wires. 
     In one or more embodiments, the second U-shaped wires include a plurality of second U-shaped wire groups configured to be disposed into corresponding ones of the slot-positions circumferentially, wherein each second U-shaped wire group includes partially-overlapped U-shaped sections of the second U-shaped wires. 
     In one or more embodiments, the stator core includes a plurality of pole regions surrounding the stator core circumferentially, each pole region includes a plurality of the slot-positions, the second U-shaped wire groups are disposed with equal spans into corresponding ones of the slot-positions circumferentially, each span is two pole pitches. 
     The hairpin wire motor stator disclosed herein utilizeds various types of U-shaped wires and various types of straight wires that are appropriately arranged on the motor stator core of an odd-numbered slot-position layers greater than or equal to 5 such that the wire span can be easily adjusted on two opposites sides of the stator core, thereby reducing the difficulty of welding and bonding as well as associated man-hours and costs for bonding and manufacturing. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG.  1    illustrates a circuit diagram of a motor stator according to an embodiment of the present disclosure; 
         FIG.  2    illustrates a top view of a stator core of a motor stator according to an embodiment of the present disclosure; 
         FIG.  3    illustrates a winding U 1  configured in U phases of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  4    illustrates a winding U 2  configured in U phases of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  5    illustrates a winding W 1  configured in W phases of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  6    illustrates a winding W 2  configured in W phases of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  7    illustrates a winding V 1  configured in V phases of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  8    illustrates a winding V 2  configured in V phases of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  9    illustrates windings configured in U, W, V phases at a first side of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  10    illustrates windings configured in U, W, V phases at a second side of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  11    illustrates a perspective view of a 48-slot motor stator according to an embodiment of the present disclosure; 
         FIG.  12    illustrates a first U-shaped wire configured in a stator core according to an embodiment of the present disclosure; 
         FIG.  13    illustrates a second U-shaped wire configured in a stator core according to an embodiment of the present disclosure; 
         FIG.  14    illustrates a third U-shaped wire configured in a stator core according to an embodiment of the present disclosure; 
         FIG.  15    illustrates a first straight wire configured in a stator core according to an embodiment of the present disclosure; 
         FIG.  16    illustrates a second straight wire configured in a stator core according to an embodiment of the present disclosure; 
         FIG.  17    illustrates a perspective view of a wire configuration at a first side of a motor stator according to an embodiment of the present disclosure; 
         FIG.  18    illustrates a side view of the wire configuration at a first side of a motor stator in  FIG.  17   ; 
         FIG.  19    illustrates a perspective view of a wire configuration at a second side of a motor stator according to an embodiment of the present disclosure; and 
         FIG.  20    illustrates a side view of the wire configuration at a second side of a motor stator in  FIG.  19   . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. The “clockwise winding” disclosed herein is to help understand the relative position of the inserting/protruding wire, and it can also be understood as “counterclockwise winding” based on the relative position of the inserting/protruding wire. In other words, from the perspective of mechanical configuration, there is no so-called inserting/protruding wire. From the perspective of the circuit configuration, the positive [⊕] contact can be referred as an inserting, and the negative [⊙] (neutral) contact can be referred as a protruding wire. 
     Reference is made to  FIG.  1   , which illustrates a circuit diagram of a motor stator according to an embodiment of the present disclosure. Circuit  50  includes U, V, and W phase windings. Each (U, V, W) phase winding includes two parallel-connected windings, e.g., U 1 , U 2 , W 1 , W 2 , V 1 , V 2 . The negative end ( ) of each winding is connected to the neutral terminal  52 , and the positive end (⊕) of each winding is connected to a corresponding phase terminal (for example, the phase terminals of the U, V, and W phases). 
     Reference is made to  FIG.  2   , which illustrates a top view of a 48 slot stator core of a motor stator according to an embodiment of the present disclosure. The stator core  110  is used to realize a motor stator with two parallel-connected windings configured in 8 pole regions, 48 (phase) slots, and 5 slot-position layers. Each (phase) slot, i.e., slot  1 - 48 , includes a plurality of radially adjacent slot-positions (i.e., “squares” in each (phase) slot), and each slot-position can accommodate one hairpin wire. All slot-positions surround the rotor accommodating space  150  in the circumferential direction, and form a plurality of slot-position layers (L 1  to L 5 ) adjacent in the radial direction. The 8 pole regions equally divide the stator core  110  in the circumferential direction, and each pole region has one of the U, V, and W phases. The pole region P 1  has slots  1 - 6 , the pole region P 2  has slots  7 - 12 , the pole region P 3  has slots  13 - 18 , the pole region P 4  has slots  19 - 24 , the pole region P 5  has slots  25 - 30 , the pole region P 6  has slots  31 - 36 , the pole region P 7  has slots  37 - 42 , and the pole region P 8  has slots  43 - 48 . A span across (phase) slots of a single pole region in the circumferential direction is defined as a pole pitch. Each (phase) slot allows 5 hairpin wires to be inserted into 5 slot-position layers from the outside to the inside for L 1  to L 5  layers. The ring-shaped stator core  110  defines a rotor accommodating space  150  for accommodating the rotor. The L 5  layer is closest to the rotor accommodating space  150  as a radially-innermost one of the slot-position layers, and the L 1  layer is the farthest from the rotor accommodating space  150  as a radially-outmost one of the slot-position layers. In some embodiments of the present disclosure, the (phase) slots in the pole regions have the same or nearly the same cross-sectional dimensions, and the spacing between the (phase) slots is also the same or nearly the same, but not being limited to thereto. 
     Reference is made to  FIG.  3   , which illustrates a winding U 1  configured in U phases of a 48-slot motor stator according to an embodiment of the present disclosure. Take the stator core  110  as an example to realize a motor stator with 8 pole regions, 48 slots, and 5 slot-position layers, and each of U, V, and W phases has two parallel windings respectively. The stator core  110  includes opposite sides. In the figure, the “view side” and the “opposite side” are supplemented with solid and dashed lines respectively to demostrate the wire connection and cross-slot winding configuration. Although the wire connection/cross-slot is shown in the straight line and V-shaped line in the figures, it is only for illustration and not limited to such shapes. 
     Take U phase as an example first, a leg end (U 1 ⊕) of the wire of winding U 1  is entered into the slot-position of slot-position layer L 1  of the U-phase slot  1  from the view side of stator core  110  (e.g., the first side  110   a  of  FIG.  11   ), and then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  7  on the opposite side of stator core  110  (e.g., the second side  110   b  in  FIG.  11   ), and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  14  on the view side of stator core, then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  20  on the opposite side of stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  26  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  32  on the opposite side of the stator core. The winding U 1  is wound here from slot  1  to slot  32  in a clockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  26  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  20  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  14  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  8  on the opposite side of stator core. The winding U 1  is wound here from the slot  32  to the slot  8  in a counterclockwise direction, and then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  14  on the view side of stator core in a clockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  20  on the opposite side of stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  25  on the view side of stator core, then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  31  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  37  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  43  on the opposite side of stator core. The winding U 1  is wound here from slot  8  to slot  43  in a clockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  37  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  31  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  25  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  19  on the opposite side of stator core. The winding U 1  is wound here from slot  43  to slot  19  in a counterclockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  25  on the view side of stator core in the clockwise direction, and then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  31  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  38  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  44  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  2  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  8  on the opposite side of stator core. The winding U 1  is wound here from slot  19  to slot  8  in a clockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  2  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  44  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  38  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  32  on the opposite side of stator core. The winding U 1  is wound here from slot  8  to slot  32  in a counterclockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  38  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  44  on the opposite side of stator core, then connected to the slot-position of slot-position layer L 3  of the U-phase slot  1  on the view side of stator core, then connected to the slot-position of slot-position layer L 4  of U-phase slot  7  on the opposite side of stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  13  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  19  on the opposite side of stator core. The winding U 1  is wound here from slot  32  to slot  19  in a clockwise direction. The winding U 1  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  13  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  7  on the opposite side of stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  1  on the view side of stator core, and then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  43  on the opposite side of stator core. The winding U 1  is wound here from slot  19  to slot  43  in a counterclockwise direction and its leg end (U 1 ⊙) exits at this slot-position. 
     Reference is made to  FIG.  4   , which illustrates a winding U 2  configured in U phases of a 48-slot motor stator according to an embodiment of the present disclosure. Continuing with the winding U 1  shown in  FIG.  3   , a leg end (U 2 ⊕) of the wire of the winding U 2  is entered into the slot-position of the slot-position layer L 1  of the slot  2  from the view side of the stator core, and then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  8  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  13  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  19  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  25  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  31  on the opposite side of the stator core. The winding U 2  is wound here from slot  2  to slot  31  in a clockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  25  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  19  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  13  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 1  of the U-phase slot  7  on the opposite side of the stator core. The winding U 2  is wound here from slot  31  to slot  7  in a counterclockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  13  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  19  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  26  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 4  of the U-phase slot  32  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  38  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 5  of the U-phase slot  44  on the opposite side of the stator core. The winding U 2  is wound here from slot  7  to slot  44  in a clockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  38  on the view side of the stator core, and is connected the slot-position of the slot-position layer L 3  of the U-phase slot  32  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  26  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 1  of the U-phase slot  20  on the opposite side of the stator core. Winding U 2  is here wound from slot  44  to slot  20  in a counterclockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  26  on the view side of the stator core in a clockwise direction, and then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  32  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  37  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 4  of the U-phase slot  43  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  1  on the view side of stator core, and then connected to slot-position of the slot-position layer L 5  of the U-phase slot  7  on the opposite side of stator core. The winding U 2  is wound here from slot  20  to slot  7  in a clockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  1  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  43  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  37  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 1  of the U-phase slot  31  on the opposite side of the stator core. The winding U 2  is here wound from slot  7  to slot  31  in a counterclockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 1  of the U-phase slot  37  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 2  of the U-phase slot  43  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  2  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  8  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 5  of the U-phase slot  14  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 5  of the U-phase slot  20  on the opposite side of the stator core. The winding U 2  is wound here from slot  31  to slot  20  in a clockwise direction. The winding U 2  is then connected to the slot-position of the slot-position layer L 4  of the U-phase slot  14  on the view side of the stator core, and then connected to the slot-position of the slot-position layer L 3  of the U-phase slot  8  on the opposite side of the stator core, then connected to the slot-position of the slot-position layer L 2  of the U-phase slot  2  on the view side of the stator core, and connected to the slot-position of the slot-position layer L 1  of the U-phase slot  44  on the opposite side of the stator core. The winding U 2  is wound here from slot  20  to slot  44  in a counterclockwise direction and its leg end (U 20 ) exits at this slot-position. All the wires of windings U 1  and U 2  occupy all U phase slot-positions of the stator core  110  to achieve two parallel-connected windings. 
     Reference is made to  FIG.  5   , which illustrates a winding W 1  configured in W phases of a 48-slot motor stator according to an embodiment of the present disclosure. The wires of winding W 1  are arranged in the slot-positions across W phases of the stator core, and the wire configurartions crossing the slots in the circumferential direction and the slot-position layers in the radial direction are the same as or similar to the wire configurartions of winding U 1 , so the description will not be repeated. 
     Reference is made to  FIG.  6   , which illustrates a winding W 2  configured in W phases of a 48-slot motor stator according to an embodiment of the present disclosure. The wires of winding W 2  are arranged in the slot-positions across W phases of the stator core, and the wire configurartions crossing the slots in the circumferential direction and the slot-position layers in the radial direction are the same as or similar to the wire configurartions of winding U 2 , so the description will not be repeated. 
     Reference is made to  FIG.  7   , which illustrates a winding V 1  configured in V phases of a 48-slot motor stator according to an embodiment of the present disclosure. The wires of winding V 1  are arranged in the slot-positions across V phases of the stator core, and the wire configurartions crossing the slots in the circumferential direction and the slot-position layers in the radial direction are the same as or similar to the wire configurartions of winding U 1 , so the description will not be repeated. 
     Reference is made to  FIG.  8   , which illustrates a winding V 2  configured in V phases of a 48-slot motor stator according to an embodiment of the present disclosure. The wires of winding V 2  are arranged in the slot-positions across V phases of the stator core, and the wire configurartions crossing the slots in the circumferential direction and the slot-position layers in the radial direction are the same as or similar to the wire configurartions of winding U 2 , so the description will not be repeated. 
     Reference is made to  FIG.  9   , which illustrates windings configured in U, W, V phases at a first side  110   a  of a 48-slot motor stator according to an embodiment of the present disclosure. After windings (U 1 , U 2 , W 1 , W 2 , V 1 , V 2 ) are all arranged in the stator core, the “U-shaped section” protruding from the U-shaped wire is represented by a solid line, the “leg end connection” is represented by a bold rectangle, and the “leg end” is represented by a dashed line on the first side  110   a  of the stator core  110 . Two ends of the U-shaped section of each first U-shaped wire are located in the radially outermost slot-position layer (i.e., slot-position layer L 1 ), and two ends of the U-shaped section of remaining each U-shaped wire (i.e., the third U-shaped wires described below) are located in the radially adjacent two middle slot-position layers (i.e., slot-position layers L 2 -L 3 ). The “leg end connection” of the first side  110   a  is located at the two inner slot-position layers (i.e., slot-position layers L 4 -L 5 ) that are radially adjacent to each other. The outermost slot-position layer (i.e., slot-position layer L 1 ) also has leg ends (U 1 ⊕, U 2 ⊕, W 1 ⊕, W 2 ⊕, V 1 ⊕, V 2 ⊕) connected to corresponding phase terminals (such as phase terminals of phase W, U, V), and other leg ends (U 1 ⊙, U 2 ⊙, W 1 ⊙, W 2 ⊙, V 1 ⊙, V 2 ⊙) connected to the neutral terminals (Neutral End). 
     Reference is made to  FIG.  10   , which illustrates windings configured in U, W, V phases at a second side  110   b  of a 48-slot motor stator according to an embodiment of the present disclosure. After windings (U 1 , U 2 , W 1 , W 2 , V 1 , and V 2 ) are all arranged on the stator core  110 , the “U-shaped section” protruding from the U-shaped wire is represented by a solid line and the “leg end connection” is represented by a bold rectangle on the second side  110   b  of the stator core  110 . Two ends of the U-shaped section of each U-shaped wire (i.e., the second U-shaped wire described below) are located in the radially innermost slot-position layer (i.e., the slot-position layer L 5 ). The “leg end connection” of the second side  110   b  is located at the radially adjacent two outer slot-position layers (i.e., slot-position layers L 1 -L 2 ) and radially adjacent two middle slot-position layers (i.e., slot-position layers L 3 -L 4 ). 
     Reference is made to  FIG.  11   , which illustrates a perspective view of a 48-slot motor stator  100  according to an embodiment of the present disclosure. The motor stator  100  is used to realize a three-phase motor stator with two parallel-connected windings configured in the stator core  110  with 8 pole regions, 48 (phase) slots, and 5 slot-position layers. The first side  110   a  and the second side  110   b  of the stator core  110 , which are axially opposite to each other, correspond to the first side  110   a  in  FIG.  9    and the second side  110   b  in  FIG.  10   , respectively. 
     Reference is made to  FIGS.  12 - 14   , which illustrate three types of U-shaped wires configured in a stator core according to an embodiment of the present disclosure. The first U-shaped wire  112  includes a U-shaped section  112   a,  two leg sections  112   b  and two leg ends  112   c.  The U-shaped section  112   a  protrudes from the first side  110   a  of the stator core  110 , the two leg ends  112   c  protrude from the second side  110   b  of the stator core  110 , and the two leg sections  112   b  are arranged in the slot-positions of the stator core  110 . The second U-shaped wire  114  includes a U-shaped section  114   a,  two leg sections  114   b  and two leg ends  114   c.  The U-shaped section  114   a  protrudes from the second side  110   b  of the stator core  110 , the two leg ends  114   c  protrude from the first side  110   a  of the stator core  110 , and the two leg sections  114   b  are arranged in the slot-positions of the stator core  110 . The third U-shaped wire  118  includes a U-shaped section  118   a,  two leg sections  118   b  and two leg ends  118   c.  The U-shaped section  118   a  protrudes from the first side  110   a  of the stator core  110 , the two leg ends  118   c  protrude from the second side  110   b  of the stator core  110 , and the two leg sections  118   b  are arranged in the slot-positions of the stator core  110 . Three types of U-shaped wires will be described in detail below about how they are associated with other components. 
     Reference is made to  FIGS.  15 - 16   , which illustrate two types of straight wires configured in a stator core according to an embodiment of the present disclosure. A first straight wire  116  includes a middle straight section  116   a  and two opposite leg ends  116   b  and  116   c.  The leg end  116   b  protrudes from the first side  110   a  of the stator core  110 , the leg end  116   c  protrudes from the second side  110   b  of the stator core  110 , and the middle straight section  116   a  is configured in the slot-position of the stator core  110 . A second straight wire  119  includes a middle straight section  119   a  and two opposite leg ends  119   b  and  119   c.  The leg end  119   b  protrudes from the first side  110   a  of the stator core  110 , the leg end  119   c  protrudes from the second side  110   b  of the stator core  110 , and the middle straight section  119   a  is configured in the slot-position of the stator core  110 . Two types of straight wires will be described in detail below about how they are associated with other components. 
     Reference is made to  FIG.  17   , which illustrates a perspective view of a wire configuration at a first side  110   a  of a motor stator according to an embodiment of the present disclosure. The wire configuration includes a plurality of first U-shaped wires  112 , and each first U-shaped wire  112  includes two leg sections  112   b,  both of which are arranged on the outermost slot-position layer L 1  in the radial direction, so the U-shaped section  112   a  protrudes from the outermost slot-position layer L 1  in the radial direction and is also arranged on the outermost slot-position layer L 1  on the first side  110   a  of the stator core  110 , and a distance between the two leg sections  112   b  in the circumferential direction is a pole pitch (also referring to the U-shaped section at the outermost slot-position layer in  FIG.  9   ). The first U-shaped wires  112  form three first U-shaped wire groups  500  on the first side  110   a  of the stator core  110 . Each first U-shaped wire group  500  includes  6  partially-overlapped U-shaped sections  112   a  of the first U-shaped wires  112 . The wire configuration also includes a plurality of third U-shaped wires  118 , and each third U-shaped wire  118  includes two leg sections  118   b,  which are located in two radially adjacent slot-position layers (i.e., L 2 -L 3 ) respectively, and the two radially adjacent slot-position layers L 2 -L 3  are located between the outermost slot-position layer (L 1 ) and the innermost slot-position layer (L 5 ). Therefore, when the U-shaped section  118   a  protrudes from the first side  110   a  of the stator core  110 , it is also arranged on the middle slot-position layers (also referring to the U-shaped section at the middle slot-position layers in  FIG.  9   ). The wire configuration also includes a plurality of second straight wires  119 , and each second straight wire  119  includes a middle straight section  119   a  located on the outermost slot-position layer (L 1 ) in the radial direction. Therefore, when its leg end  119   b  protrudes from the first side  110   a  of the stator core  110 , the leg end  119   b  is also arranged at the outermost layer in the radial direction (also referring to the leg end at the outermost slot-position layer in  FIG.  9   ). The wire configuration also includes a plurality of leg ends  114   c  of the second U-shaped wires  114  and a plurality of leg ends  116   b  of the first straight wires  116 . The two leg ends  114   c  of the second U-shaped wires  114  are connected to corresponding immediately-adjacent first leg ends  116   b  of the first straight wires  116  respectively. 
     Reference is made to  FIG.  18   , which illustrates a side view of the wire configuration at the first side  110   a  of a motor stator in  FIG.  17   . The two leg ends  114   c  of the second U-shaped wire  114  are flush with the first leg end  116   b  of the corresponding immediately adjacent first straight wire  116  in tops of all end connections C 1 , and an axial height H 2  protruding from the stator core  110  which is greater than an axial height H 1  of the U-shaped section  112   a  of the first U-shaped wire  112  protruding from the stator core  110  (i.e., H 2 &gt;H 1 ), so that welding the leg ends ( 114   c,    116   b ) is not affected by the U-shaped sections  112   a.  In addition, tops of the leg ends  119   b  of the second straight wires  119  are flush with one another, and its axial height H 3  protruding from the stator core  110  which is greater than the axial height H 1  of the U-shaped section  112   a  protruding from the stator core  110 , and also higher than the height H 2  (i.e., H 3 &gt;H 2 &gt;H 1 ), thereby facilitating the leg ends  119   b  of the second straight wires  119  to be connected to the corresponding phase terminals or neutral terminals. 
     Reference is made to  FIG.  19   , which illustrates a perspective view of a wire configuration at a second side  110   b  of a motor stator according to an embodiment of the present disclosure. The wire configuration includes a plurality of second U-shaped wires  114 , and each second U-shaped wire  114  includes two leg sections  114   b  (referring to  FIG.  13   ) that are arranged in the innermost slot-position layer (L 5 ) in the radial direction. Therefore, when the U-shaped section  114   a  protrudes from the second side  110   b  of the stator core  110 , it is also located on the innermost layer L 5  in the radial direction, and the two leg sections  114   b  are separated by a span across the slots in the circumferential direction by a pole pitch (referring to the U-shaped section at the innermost slot-position layer in  FIG.  10   ). The second U-shaped wires  114  include four second U-shaped wire groups  510 , which are arranged with equal spans across the slot-positions in the circumferential direction, and each second U-shaped wire group  510  includes 6 partially-overlapped U-shaped sections  114   a  of the U-shaped wires  114 . Each second U-shaped wire group  510  has an equal span of two pole pitches (the motor stator includes 8 pole regions, and 8 pole regions are equally divided by 4 second U-shaped wire groups  510 , such that each second U-shaped wire group  510  has the equal span of two pole pitches). The wire configuration further includes a plurality of leg ends  112   c  of the first U-shaped wires  112 , a plurality of leg ends  118   c  of the third U-shaped wires  118 , and a plurality of leg ends  116   c  of the first straight wires  116 . The middle straight section  116   a  (referring to  FIG.  15   ) of each first straight wire  116  is located in the second radially-inner slot-position layer (L 4 ) in the radial direction. The two leg ends  112   c  of the first U-shaped wire  112  are respectively connected to corresponding immediately adjacent one of the two leg ends  118   c  of the third U-shaped wire  118  on the second side  110   b  of the stator core  110 . The leg end  116   c  of the first straight wire  116  is connected to corresponding immediately adjacent one of the two leg ends  118   c  of the third U-shaped wire  118  on the second side  110   b  of the stator core  110 . 
     Reference is made to  FIG.  20   , which illustrates a side view of the wire configuration at the second side  100   b  of a motor stator in  FIG.  19   . The two leg ends  112   c  of the first U-shaped wire  112  and the two leg ends  118   c  of the third U-shaped wire  118  are flush with each other in tops of all end connections C 2 , and its axial height H 4  protrudes from the stator core  110  which is greater than an axial height H 5  of the U-shaped section  114   a  of the second U-shaped wire  114  protruding from the stator core  110  (H 4 &gt;H 5 ), so that welding the leg ends ( 112   c,    118   c ) is not affected by the U-shaped sections  114   a.  The second leg end  116   c  of the first straight wire  116  and corresponding immediately adjacent one of the two leg ends  118   c  of the third U-shaped wire  118  are flush with each other in tops of all end connections C 3 , and its axial height H 4  protrudes from the stator core  110  which is greater than axial height H 5  of the U-shaped section  114   a  of the second U-shaped wire  114  protruding from the stator core  110  (H 4 &gt;H 5 ), so that welding the leg ends ( 116   c,    118   c ) is not affected by the U-shaped sections  114   a.  In addition, the tops of all end connections C 2  are also flush with the tops of all end connections C 3  to speed up the welding of the leg ends ( 112   c,    116   c,    118   c ). 
     Although three types of U-shaped wires and two types of straight wires are only exemplified on the motor stator core with 48-slots and 5-slot-position layers, they can also be applied to a stator core with other odd-numbered slot-position layers greater than or equal to 5 and the number of slots and is not limited. 
     The hairpin wire motor stator disclosed herein utilizeds various types of U-shaped wires and various types of straight wires that are appropriately arranged on the motor stator core of an odd-numbered slot-position layers greater than or equal to 5 such that the wire span can be easily adjusted on two opposites sides of the stator core, thereby reducing the difficulty of welding and bonding as well as associated man-hours and costs for bonding and manufacturing. 
     Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.