A motor winding and stator assembly

Abstract

The application provides a motor winding and a stator assembly, and the motor winding comprises: a multi-phase winding, each phase winding comprises a plurality of branches, each branch comprises: a forward coil group comprising a plurality of U-shaped coils; a reverse coil group comprising a plurality of U-shaped coils, wherein the span of the U-shaped coils of the forward coil group and the U-shaped coils of the reverse coil group is y+1, y-2, or y+2, y-1, y represents the pole pitch of the motor; and a same-layer jumper with a span of y, the same-layer jumper connects the forward coil group and the reverse coil group; wherein the U-shaped coils of the forward coil group are connected in a circumferential direction after one round and are connected to the next round in a radial direction; the reverse coil group has the same winding mode as the forward coil group and has an opposite winding direction. The application suppresses the circulating current between the parallel branches, reduces the temperature rise of the winding, reduces the vibration of the motor and suppresses the increase of noise.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric machines, in particular to a stator assembly and an electric machine using the same. BACKGROUND

[0002] New energy vehicle drive motors using flat wire windings have the advantages of light weight, high power density, high efficiency, etc., and have gradually become the development direction of drive motors. With the increase of motor power and speed, the number of slots per pole per phase and the number of parallel branches also increase.

[0003] In the prior art, a commonly used wave winding method is to wind from the outermost layer to the innermost layer with full-pitch coils, and then wind from the innermost layer to the outermost layer with full-pitch coils in the opposite direction. In this way, when the number of slots per pole per phase and the number of parallel branches increase, the flat wire coils in the stator slots of each parallel branch are distributed asymmetrically, and there is circulating current between the parallel branches, which not only aggravates the temperature rise of the winding, but also causes the vibration and noise of the motor to increase. SUMMARY

[0004] The present application proposes an electric machine winding and a stator assembly to solve the problem of asymmetric distribution of flat wire coils in the stator slots of each parallel branch when the number of slots per pole per phase and the number of parallel branches increases, and proposes the following technical solutions.

[0005] The present application proposes an electric machine winding, comprising:

[0006] A multi-phase winding, each phase of the winding comprising a plurality of branches, each branch comprising:

[0007] a forward coil group comprising a plurality of U-shaped coils;

[0008] a reverse coil group comprising a plurality of U-shaped coils, wherein the span of the U-shaped coils of the forward coil group and the U-shaped coils of the reverse coil group is y+1, y-2, or y+2, y-1, y representing the pole pitch of the motor; and

[0009] a same-layer jumper with a span of y, the same-layer jumper connecting the forward coil group and the reverse coil group;

[0010] wherein the U-shaped coils of the forward coil group are connected circumferentially after one turn, and then connected radially to the next turn; the reverse coil group has the same winding method as the forward coil group, but the winding direction is opposite.

[0011] In an embodiment of the present application, each forward coil group or reverse coil group under one magnetic pole has a radial difference of two slot layers between radially adjacent U-shaped coils.

[0012] In an embodiment of the present application, the U-shaped coil comprises a welding portion, and the U-shaped coil welding portion extends by y / 2 at the end face of the iron core, and adjacent U-shaped coils are connected by the welding portion.

[0013] In an embodiment of the present application, the welding portions of the U-shaped coils extend away from each other and in opposite directions.

[0014] In an embodiment of the present application, the branches are arranged in parallel, and the number of the branches is a positive integer greater than or equal to 3.

[0015] In an embodiment of the present application, the incoming wire ends of each branch are sequentially different by one stator slot.

[0016] The present application provides a stator assembly, comprising:

[0017] An iron core is provided with a plurality of stator slots, and the stator slots are distributed along the circumference of the iron core;

[0018] A multi-phase winding is wound on the iron core, and each phase of the winding comprises a plurality of branches, and each branch comprises:

[0019] A forward coil group comprises a plurality of U-shaped coils;

[0020] A reverse coil group comprises a plurality of U-shaped coils, wherein the span of the U-shaped coils of the forward coil group and the U-shaped coils of the reverse coil group is y+1, y-2, or y+2, y-1, and y represents the pole pitch of the motor; and

[0021] A same-layer jumper with a span of y connects the forward coil group and the reverse coil group;

[0022] Wherein, the U-shaped coils of the forward coil group are connected in a circumferential direction for one turn and then connected in a radial direction to the next turn, and the reverse coil group has the same winding mode as the forward coil group but in the opposite direction.

[0023] In an embodiment of the present application, the stator slots of the iron core are provided with M slot layers, and M is an even number.

[0024] In an embodiment of the present application, two straight sections of one U-shaped coil are located in the mth slot layer and the m+1th slot layer, respectively, and m+1≤M.

[0025] In an embodiment of the present application, the same-layer jumper is located in the Mth slot layer.

[0026] The present application provides a motor winding and a stator assembly, and the U-shaped coils in the stator slots of each parallel branch are symmetrically distributed, which suppresses the circulating current between the parallel branches, reduces the temperature rise of the winding, and reduces the vibration and noise of the motor. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structure diagram of a stator assembly of the present application.

[0028] Figure 2 It is a structure diagram of a stator slot in a stator assembly of the present application.

[0029] Figure 3 It is a wiring diagram of a phase winding in an embodiment of a stator assembly of the present application.

[0030] Figure 4 It is an unfolded diagram of a branch of a phase winding in an embodiment of a stator assembly of the present application.

[0031] Figure 5 It is an unfolded diagram of another branch of a phase winding in an embodiment of a stator assembly of the present application.

[0032] Figure 6 It is an unfolded diagram of another branch of a phase winding in an embodiment of a stator assembly of the present application.

[0033] Figure 7 It is a structure diagram of a forward coil group in a stator assembly of the present application.

[0034] Figure 8 It is a structure diagram of a reverse coil group in a stator assembly of the present application.

[0035] Figure 9 It is a structure diagram of a long-pitch U-shaped coil in a stator assembly of the present application.

[0036] Figure 10 It is a structure diagram of a short-pitch U-shaped coil in a stator assembly of the present application.

[0037] Figure 11 It is a structure diagram of a same-layer jumper in a stator assembly of the present application.

[0038] Figure 12 It is a structure diagram of a lead coil in a stator assembly of the present application.

[0039] Figure 13 It is a wiring diagram of a phase winding in another embodiment of a stator assembly of the present application.

[0040] Figure 14 It is an unfolded diagram of a branch of a phase winding in another embodiment of a stator assembly of the present application.

[0041] Figure 15 It is an unfolded diagram of another branch of a phase winding in another embodiment of a stator assembly of the present application.

[0042] Figure 16 Unfolded view of another branch of one phase winding in another embodiment of a stator assembly of the present application.

[0043] Figure 17 Schematic view of three parallel branch structure with star connection in a stator assembly of the present application.

[0044] In the figure: 100, stator winding; 1001, hairpin end; 1002, soldering end;

[0045] 111, long-pitch U-shaped coil;

[0046] 121, short-pitch U-shaped coil;

[0047] 131, same-layer jumper wire;

[0048] 141, lead-out coil;

[0049] 101, head; 102, first straight section; 103, second straight section;

[0050] 104, first soldering part; 105, second soldering part;

[0051] 200, stator core; 210, stator slot. DETAILED DESCRIPTION

[0052] The embodiments of the present application will be described in detail with specific reference felt to the drawings. The advantages and effects of the present application can be easily understood by those skilled in the art from the description of the present application. The present application can also be implemented or applied in other different embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0053] It should be noted that the diagrams provided in the embodiments only schematically illustrate the basic concept of the present application, and the diagrams only show the components related to the present application, not the number, shape and size of the components in actual implementation. The shape, number and proportion of the components in actual implementation can be arbitrarily changed, and the layout pattern of the components can be more complex.

[0054] Referring to Figures 1-17 The present application provides a motor winding and a stator assembly, which can be applied to the field of electrical servo transmission and the field of transportation, for example, the motor winding and the stator assembly of the present application can be applied to an electric vehicle. The parallel branches of the present application are symmetrically distributed in the flat wire coils in the stator slots, which suppresses the circulating current between the parallel branches, reduces the temperature rise of the winding, and has the advantages of reducing the vibration of the motor and suppressing the increase of noise. The present application will be described in detail through specific embodiments.

[0055] Referring toFigure 1 As shown in some embodiments, the present application proposes a stator assembly, which can include a stator winding 100 and a stator core 200. The stator winding 100 can include a plurality of phase windings, which are different from each other in electrical phase, for example, the stator winding 100 can include three phase windings. The stator core 200 can be provided with a plurality of stator slots 210, which can be formed on the inner wall of the stator core 200. The stator slots 210 can be arranged along the circumferential direction of the inner wall of the stator core 200, and the stator slots 210 can be spaced apart at a predetermined slot pitch on the stator core 200. The upper and lower end faces of the stator core 200 can be defined as the hairpin end 1001 and the welding end 1002, respectively, and the stator winding 100 can be inserted into the stator core 200 from the side of the hairpin end 1001, and the stator winding 100 can be welded at the welding end 1002.

[0056] Please refer to Figures 2-8 As shown in some embodiments, the plurality of stator slots 210 in the circumferential direction of the stator core 200 can be defined as the first stator slot 210, the second stator slot 210, the third stator slot 210, the fourth stator slot 210, and so on. For example, the stator core 200 can be arranged with 54 stator slots 210 along the circumferential direction. Each stator slot 210 can be provided with a plurality of slot layers, and each stator slot 210 can be provided with M slot layers, M being an even number. For example, each stator slot 210 can be provided with 6 slot layers. For example, the 6 slot layers along the radial direction of the stator core 200 from the inside to the outside can be sequentially defined as the L1 layer slot layer, the L2 layer slot layer, the L3 layer slot layer, the L4 layer slot layer, the L5 layer slot layer, and the L6 layer slot layer, that is, the L1 layer slot layer can be located near the slot opening side of the stator slot 210, and the L6 layer slot layer can be located near the slot bottom side of the stator slot 210. In addition, the specific label of the slot layer of each stator slot 210 is not limited, and the embodiments in the present application are arranged in the order of 1-6 from the slot opening of the stator slot 210 to the slot bottom of the stator slot 210, and in other embodiments, the slot layers can also be arranged in the order of 1-6 from the slot bottom of the stator slot 210 to the slot opening of the stator slot 210.

[0057] Please refer to Figures 9-10As shown, in some embodiments, the U-shaped coils include long-pitch U-shaped coils 111 and short-pitch U-shaped coils 121. The long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 can include one connecting portion, two straight segment portions, and two welding portions. The two ends of the connecting portion are respectively connected with one straight segment portion. The two straight segment portions pass through the stator slots 210 of the stator core 200 and are twisted at the welding end 1002 to form two welding portions. The two welding portions of the long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 extend the same distance along one side of the welding end 1002 of the stator core 200, which can be equal to half of the pole pitch. For example, the long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 can include a head portion 101, a first straight segment portion 102, a second straight segment portion 103, a first welding portion 104, and a second welding portion 105. The first straight segment portion 102 and the second straight segment portion 103 can be inserted into the stator slots 210, and the first straight segment portion 102 and the second straight segment portion 103 can be inserted into different stator slots 210. One end of the first straight segment portion 102 can be connected with the first welding portion 104, and one end of the second straight segment portion 103 can be connected with the second welding portion 105. The other end of the first straight segment portion 102 and the other end of the second straight segment portion 103 can be connected with the head portion 101.

[0058] As shown in FIGS. 9 and 10, in some embodiments, in each branch of each phase winding, the two straight segment portions of the long-pitch U-shaped coils 111 can be radially different by one slot layer, i.e., the two straight segment portions of the long-pitch U-shaped coils 111 are located at the mth slot layer and the m+1th slot layer, and m+1≤M. The two straight segment portions of the short-pitch U-shaped coils 121 can be radially different by one slot layer, i.e., the two straight segment portions of the short-pitch U-shaped coils 121 are located at the mth slot layer and the m+1th slot layer. The span of the long-pitch U-shaped coils 111 is represented as y1, which can be greater than the pole pitch of the stator winding 100, and the pole pitch of the stator winding 100 is represented as y, for example, y1=y+1. The span of the short-pitch U-shaped coils 121 is represented as y2, which can be less than the pole pitch of the stator winding 100, for example, y2=y-2.

[0059] As shown in FIGS. 9 and 10, Figures 9-10 As shown, in some embodiments, the first welding portions 104 and the second welding portions 105 of the long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 can be away from each other, and the extension directions of the first welding portions 104 and the second welding portions 105 of the long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 can be towards opposite directions, for example, the extension directions of the plurality of first welding portions 104 can be towards the clockwise direction or the counterclockwise direction, and the extension directions of the plurality of second welding portions 105 are opposite.

[0060] As shown in FIGS. 9 and 10, Figure 11As shown, in some embodiments, the same-layer jumper 131 can include a head 101, a first straight section 102, a second straight section 103, a first welding portion 104, and a second welding portion 105. The first straight section 102 and the second straight section 103 can be used to be inserted into the stator slot 210, and the first straight section 102 and the second straight section 103 can be inserted into different stator slots 210. One end of the first straight section 102 can be connected with the first welding portion 104, and one end of the second straight section 103 can be connected with the second welding portion 105. The other end of the first straight section 102 and the other end of the second straight section 103 can be connected with the head 101. The two welding portions of the same-layer jumper 131 can extend the same distance along one side of the stator core 200 welding end 1002, which can be equal to half of the pole pitch.

[0061] As shown in FIG. 11, in some embodiments, in each branch of each phase winding, the two straight section portions of the same-layer jumper 131 can be radially different by one slot layer. The span of the same-layer jumper 131 is denoted as y3, which can be equal to the pole pitch of the stator winding 100, for example, y3=y. The first welding portion 104 and the second welding portion 105 of the same-layer jumper 131 can extend in the same direction, for example, the extension direction of the plurality of first welding portions 104 and the plurality of second welding portions 105 can be towards the clockwise direction or the counterclockwise direction.

[0062] As shown in FIG. 11, in some embodiments, in each branch of each phase winding, the two straight section portions of the same-layer jumper 131 can be radially different by one slot layer. The span of the same-layer jumper 131 is denoted as y3, which can be equal to the pole pitch of the stator winding 100, for example, y3=y. The first welding portion 104 and the second welding portion 105 of the same-layer jumper 131 can extend in the same direction, for example, the extension direction of the plurality of first welding portions 104 and the plurality of second welding portions 105 can be towards the clockwise direction or the counterclockwise direction. Figure 12 As shown, in some embodiments, the lead-out coil 141 is a half-U-shaped coil, and the lead-out coil 141 can include a head 101, a first straight section 102, and a first welding portion 104. The first straight section 102 can be used to be inserted into the stator slot 210. One end of the first straight section 102 can be connected with the first welding portion 104, and the other end of the first straight section 102 can be connected with the head 101. The first welding portion 104 of the lead-out coil 141 can extend a distance along one side of the stator core 200 welding end 1002, which can be equal to half of the pole pitch. In each branch of each phase winding, the first welding portions 104 of the two lead-out coils 141 can extend in the same direction. For example, the extension direction of the two first welding portions 104 can be towards the clockwise direction or the counterclockwise direction. In each branch of each phase winding, the two lead-out coils 141 can be located in the L1 slot layer.

[0063] Please refer to 1-12, in some embodiments, each phase winding can include multiple branches, for example, in this application, each phase winding can include three branches. Each branch can include a forward coil group, a reverse coil group, a same layer jumper 131 and two outgoing coils 141. Among them, the same layer jumper 131 can be connected between the forward coil group and the reverse coil group, one outgoing coil 141 can be connected with the welding part of the forward coil group, and the other outgoing coil 141 can be connected with the welding part of the reverse coil group to form a complete branch. One outgoing coil 141 as a lead end, and the other outgoing coil 141 as an outgoing end. A forward coil group can include multiple long-pitch U-shaped coils 111 and multiple short-pitch U-shaped coils 121, and the long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 in the forward coil group are connected in a circumferential direction for one turn and then connected in a radial direction to the next turn. A reverse coil group can include multiple long-pitch U-shaped coils 111 and multiple short-pitch U-shaped coils 121, and the long-pitch U-shaped coils 111 and the short-pitch U-shaped coils 121 in the reverse coil group are connected in a circumferential direction for one turn and then connected in a radial direction to the next turn. In Figures 7-8 , the winding direction of the forward coil group and the reverse coil group is opposite.

[0064] Please refer to Figures 3-6 , in some embodiments, under each magnetic pole, each forward coil group or each reverse coil group has radially adjacent U-shaped coils that are radially different by two slot layers. For example, the straight section of the radially adjacent long-pitch U-shaped coils 111 is radially different by two slot layers, or the straight section of the radially adjacent short-pitch U-shaped coils 121 is radially different by two slot layers.

[0065] Please refer to Figures 3-6 , in some embodiments, in order to more clearly express the wiring of the application, only the expansion diagram of the A-phase winding is drawn in the winding expansion diagram, and the windings of the B-phase and C-phase are not involved. The winding method of the B-phase winding and the C-phase winding is the same as that of the A-phase winding, and the only difference is that the slot numbers of the lead-in end and the lead-out end are different. For example, the lead-in end of the A-phase winding is the 46th stator slot 210, the 47th stator slot 210 and the 48th stator slot 210, and the lead-in end of the B-phase winding can be the 40th stator slot 210, the 41st stator slot 210 and the 42nd stator slot 210, and the lead-in end of the C-phase winding can be the 34th stator slot 210, the 35th stator slot 210 and the 36th stator slot 210.

[0066] The specific winding method of the first branch A1X1 of the A-phase winding is as follows, wherein 46(1) represents the L1 layer of the 46th stator slot 210.

[0067] A1 -> 46(1) -> 37(2) -> 30(1) -> 21(2) -> 11(1) -> 2(2) -> 46(3) -> 37(4) -> 30(3) -> 21(4) -> 11(3) -> 2(4) -> 46(5) -> 37(6) -> 30(5) -> 21(6) -> 11(5) -> 2(6) -> 47(6) -> 2(5) -> 12(6) -> 21(5) > 28(6) -> 37(5) -> 47(4) -> 2(3) -> 12(4) -> 21(3) -> 28(4) -> 37(3) -> 47(2) -> 2(1) -> 12(2) -> 21(1) -> 28(2) -> 37(1) -> X1.

[0068] The specific winding mode of the second branch A2X2 of the A-phase winding is as follows:

[0069] A2 -> 47(1) -> 38(2) -> 28(1) -> 19(2) -> 12(1) -> 3(2) -> 47(3) -> 38(4) -> 28(3) -> 19(4) -> 12(3) -> 3(4) -> 47(5) -> 38(6) -> 28(5) -> 19(6) -> 12(5) -> 3(6) -> 48(6) -> 3(5) -> 10(6) -> 19(5) > 29(6) -> 38(5) -> 48(4) -> 3(3) -> 10(4) -> 19(3) -> 29(4) -> 38(3) -> 48(2) -> 3(1) -> 10(2) -> 19(1) -> 29(2) -> 38(1) -> X2.

[0070] The specific winding mode of the third branch A3X3 of the A-phase winding is as follows:

[0071] A3 -> 48(1) -> 39(2) -> 29(1) -> 20(2) -> 10(1) -> 1(2) -> 48(3) -> 39(4) -> 29(3) -> 20(4) -> 10(3) -> 1(4) -> 48(5) -> 39(6) -> 29(5) -> 20(6) -> 10(5) -> 1(6) -> 46(6) -> 1(5) -> 11(6) -> 20(5) -> 30(6) -> 39(5) -> 46(4) -> 1(3) -> 11(4) -> 20(3) -> 30(4) -> 39(3) -> 46(2) -> 1(1) -> 11(2) -> 20(1) -> 30(2) -> 39(1) -> X3.

[0072] As can be seen from the winding method above, the input terminal A1 of the first parallel branch A1X1 is in the L1 slot layer of stator slot 210 (46th slot), and the output terminal X1 is in the L1 slot layer of stator slot 210 (37th slot). The input terminal A2 of the second parallel branch A2X2 is in the L1 slot layer of stator slot 210 (47th slot), and the output terminal X2 is in the L1 slot layer of stator slot 210 (38th slot). The input terminal A3 of the third parallel branch A3X3 is in the L1 slot layer of stator slot 210 (48th slot), and the output terminal X3 is in the L1 slot layer of stator slot 210 (39th slot). The input terminals A1, A2, and A3 of the three parallel branches are separated by one stator slot 210, and the input terminals A1, A2, and A3 and the output terminals X1, X2, and X3 of each parallel branch are distributed in the same slot layer. In each branch of each phase winding, the input and output terminals are located within slot L1, and are circumferentially separated by y stator slots 210. That is, in each branch of each phase winding, the two lead coils 141 are circumferentially separated by y stator slots 210 along the stator core 200. It should be noted that "phase difference" can refer to the difference between two slot numbers, for example, a difference of 6 slots between stator slot 3 210 and stator slot 9 210. Additionally, "phase difference" can also refer to the difference between two slot layers, for example, a difference of 3 slot layers between slot layer L1 and slot layer L4.

[0073] Please see Figures 1-12 As shown, in some embodiments, in the forward coil group and the reverse coil group, the span of the long-pitch U-shaped coil 111 is: y1=y+1, and the span of the short-pitch U-shaped coil 121 is: y2=y-2.

[0074] Please see Figures 1-2 , Figures 7-8 and Figures 13-16 As shown, in some other embodiments, in the forward coil group and the reverse coil group, the span of the long-pitch U-shaped coil 111 is: y1=y+2, and the span of the short-pitch U-shaped coil 121 is: y2=y-1.

[0075] Please see Figure 17 As shown, in some embodiments, the three branches can be connected in parallel to form a single-phase winding. In each phase winding, the lead terminals A1, A2, and A3 of the three branches are connected, and the output terminals X1, X2, and X3 of the three branches are connected. The lead terminals of the three-phase windings A, B, and C are connected, and the output terminals of the three-phase windings A, B, and C are connected, forming a star connection between the three-phase windings A, B, and C.

[0076] In summary, the motor winding and stator assembly are provided, through the arrangement of the winding, the distribution of the flat wire coil in each parallel branch stator slot is symmetrical, the circulating current between the parallel branches is inhibited, the temperature rise of the winding is reduced, the motor vibration is reduced and the noise increase is inhibited. In addition, the flat wire coil in each stator slot belongs to each parallel branch of the same phase, and the same phase distribution is realized between each flat wire coil, so that the interphase insulation between the flat wire coils is cancelled, the copper fullness of the winding is increased, and the efficiency of the motor is further improved.

[0077] The above description is only the preferred embodiment of the application and the explanation of the applied technical principles, and those skilled in the art should understand that the application range involved in the application is not limited to the technical solutions formed by the specific combination of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, for example, the technical solutions formed by replacing the above features with the technical features disclosed in the application (but not limited to) having similar functions.

[0078] In addition to the technical features described in the specification, the remaining technical features are known to those skilled in the art, and in order to highlight the innovative features of the application, the remaining technical features will not be described here.

Claims

1. An electrical machine winding, characterized by, The application relates to a multi-phase winding, each phase of the winding comprising a plurality of branches, each branch comprising: a forward coil group comprising a plurality of U-shaped coils; a reverse coil group comprising a plurality of U-shaped coils, wherein the U-shaped coils of the forward coil group and the U-shaped coils of the reverse coil group are arranged in a manner that the span of long-distance U-shaped coils is y+1 and the span of short-distance U-shaped coils is y-2, or the span of long-distance U-shaped coils is y+2 and the span of short-distance U-shaped coils is y-1, y representing the pole pitch of the motor; and a same-layer jumper with a span of y, the same-layer jumper connecting the forward coil group and the reverse coil group; wherein the U-shaped coils of the forward coil group are connected in a circumferential direction for one turn and then connected in a radial direction to the next turn, the reverse coil group has the same winding mode as the forward coil group but has an opposite winding direction; the U-shaped coil comprises a head, a straight segment and a welding portion; in each branch of each phase winding, the two straight segments of long-distance U-shaped coils are radially different by one slot layer, the two straight segments of short-distance U-shaped coils are radially different by one slot layer, and the extension distance of the first welding portion and the second welding portion of long-distance U-shaped coils and short-distance U-shaped coils is half of the pole pitch; in each forward coil group or each reverse coil group under one magnetic pole, radially adjacent U-shaped coils are radially different by two slot layers. the U-shaped coil comprises a welding portion, the extension distance of the welding portion of the U-shaped coil on the end surface of the iron core is y / 2, and adjacent U-shaped coils are connected through the welding portion.

2. The motor winding of claim 1, wherein, the welding portions of the U-shaped coils are away from each other and extend in opposite directions.

3. The motor winding of claim 2, wherein, the branches are arranged in parallel, and the number of the branches is a positive integer greater than or equal to 3.

4. The motor winding of claim 1, wherein, the incoming wire ends of each branch are sequentially different by one stator slot.

5. The motor winding of claim 1, wherein, The application relates to a multi-phase winding, each phase of the winding comprising a plurality of branches, each branch comprising:

6. A stator assembly characterized by, an iron core provided with a plurality of stator slots, the stator slots being distributed in a circumferential direction of the iron core; a multi-phase winding, the winding being wound on the iron core, each phase of the winding comprising a plurality of branches, each branch comprising: a forward coil group comprising a plurality of U-shaped coils; a reverse coil group comprising a plurality of U-shaped coils, wherein the U-shaped coils of the forward coil group and the U-shaped coils of the reverse coil group are arranged in a manner that the span of long-distance U-shaped coils is y+1 and the span of short-distance U-shaped coils is y-2, or the span of long-distance U-shaped coils is y+2 and the span of short-distance U-shaped coils is y-1, y representing the pole pitch of the motor; and a same-layer jumper with a span of y, the same-layer jumper connecting the forward coil group and the reverse coil group; wherein the U-shaped coils of the forward coil group are connected in a circumferential direction for one turn and then connected in a radial direction to the next turn, the reverse coil group has the same winding mode as the forward coil group but has an opposite winding direction; the U-shaped coil comprises a head, a straight segment and a welding portion; in each branch of each phase winding, the two straight segments of long-distance U-shaped coils are radially different by one slot layer, the two straight segments of short-distance U-shaped coils are radially different by one slot layer, and the extension distance of the first welding portion and the second welding portion of long-distance U-shaped coils and short-distance U-shaped coils is half of the pole pitch; in each forward coil group or each reverse coil group under one magnetic pole, radially adjacent U-shaped coils are radially different by two slot layers. Each positive coil group or each negative coil group under one magnetic pole is composed of radially adjacent U-shaped coils which are radially different by two slot layers.

7. The stator assembly of claim 6, wherein, The stator slot of the iron core is provided with M slot layers, and M is an even number.

8. The stator assembly of claim 7, wherein, Two straight line sections of one U-shaped coil are respectively located in the mth slot layer and the m+1th slot layer, and m+1≤M.

9. The stator assembly of claim 7, wherein, The same-layer jumper is located in the Mth slot layer.

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