Stator assembly and motor

Abstract

To realize improvement of torque pulsation and noise performance of a motor, enhancement of flexibility of assembly of the motor and absence of cyclic current and phase difference between branches.SOLUTION: A stator assembly comprises a stator core and a stator winding. The stator winding comprises U-phase, V-phase and W-phase windings. n stator slots are provided on an inner circumferential surface of the stator core, each stator slot is divided into m housing layers in a radial direction of the stator core, and the U-phase winding is provided in the stator slot, provided in the same layer in the m-th housing layer, and provided over layers in the remaining housing layers, where n is multiples of six, m is an odd number larger than three, the U-phase winding includes first and second branch windings, the first and second branch windings being formed by serially connecting the same number and the same kinds of coils, the V-phase windings rotates the U-phase winding clockwise by 120° and the W-phase winding rotates the U-phase winding clockwise by 240°.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and particularly to a stator assembly and a motor.

Background Art

[0002] Currently, many of the stator windings of drive motors are even-layer flat wire windings. In order to widely adapt to various technical index requirements of motors, it is necessary to use odd-layer flat wire windings. Many of the conventional odd-layer flat wire windings use full pitch connections, and there are hair-pin coils of the same layer at both the welded end and the non-welded end of the stator winding. Since the hair-pin coils of the same layer occupy the radial inner space of the stator slot during skewing, the rotor assembly can only be assembled from one side of the stator assembly. And due to the structure installation of the full pitch connection, the content of the 5th and 7th harmonics in the motor is high, and the motor noise is large.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Regarding the above problems, the present invention discloses a stator assembly and a motor to solve or at least partially solve the above problems.

Means for Solving the Problems

[0004] To achieve the above object, the following technical solutions are used in the present invention.

[0005] In one aspect of the present invention, a stator assembly is disclosed. The stator assembly includes a stator core and a stator winding. The stator winding includes a U-phase winding, a V-phase winding, and a W-phase winding. The inner circumferential surface of the stator core is provided with n stator slots, each stator slot is divided into m housing layers along the radial direction of the stator core, the U-phase winding is provided within the stator slot, and within the m-th housing layer it is provided in the same layer, and within the remaining housing layers it is provided across layers, where n is a multiple of 6 and m is an odd number greater than 3. The U-phase winding includes a first branch winding and a second branch winding, the first branch winding and the second branch winding being formed by connecting the same number and type of coils in series, the V-phase winding being obtained by rotating the U-phase winding 120° clockwise, and the W-phase winding being obtained by rotating the U-phase winding 240° clockwise.

[0006] Furthermore, each stator slot is divided into five housing layers, with the layers from the slot opening to the slot bottom being, in order, a, b, c, d, and e, and the first branch winding includes a first coil unit, a second coil unit, and a third coil unit. The first coil unit includes one S-shaped lead coil group and a plurality of full-pitch hairpin coil groups, the S-shaped lead coil group is located at the starting end of the first coil unit and is sequentially connected in series with the plurality of full-pitch hairpin coil groups, and the first coil unit is provided spanning the a-th layer and the b-th layer housing layer. The second coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, and the second coil unit is provided spanning the c-th layer and the d-th layer housing layer, with the starting end of the second coil unit connected to the end of the first coil unit via a long-pitch hairpin coil group. The third coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, with the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils sequentially and alternately connected in series, with the third coil unit provided spanning the e-th layer housing layer and the e-th layer housing layer, and the third coil unit is connected to the end of the second coil unit via a full-pitch hairpin coil group.

[0007] Furthermore, the coil connection routes from the positive inlet terminal to the negative outlet terminal in the first branch winding are, in order, 1a, 7b, 13a, 19b, 25a, 31b, 37a, 43b, 2c, 8d, 14c, 20d, 26c, 32d, 38c, 44d, 2e, 44e, 39e, 33e, 26e, 20e, 15e, 9e, 3d, 45c, 39d, 33c, 27d, 21c, 15d, 9c, 2b, 44a, 38b, 32a, 26b, 20a, 14b, and 8a. The coil connection routes from the positive inlet terminal to the negative outlet terminal in the second branch winding are, in order, 2a, 8b, 14a, 20b, 26a, 32b, 38a, 44b, 3c, 9d, 15c, 21d, 27c, 33d, 39c, 45d, 3e, 45e, 38e, 32e, 27e, 21e, 14e, 8e, 2d, 44c, 38d, 32c, 26d, 20c, 14d, 8c, 1b, 43a, 37b, 31a, 25b, 19a, 13b, and 7a.

[0008] Furthermore, in the third coil unit, the long-pitch hairpin coil and the short-pitch hairpin coil are skewed by the same distance.

[0009] Furthermore, each stator slot is divided into seven housing layers, and from the slot opening to the slot bottom of the stator slot are, in order, layers a, b, c, d, e, f, and g, and the first branch winding includes a first coil unit, a second coil unit, a third coil unit, and a fourth coil unit. The first coil unit includes one S-shaped lead coil group and a plurality of full-pitch hairpin coil groups, the S-shaped lead coil group is located at the starting end of the first coil unit and is sequentially connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit is provided spanning the a-layer and the b-layer housing, the second coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the second coil unit is provided spanning the c-layer and the d-layer housing, the starting end of the second coil unit is connected to the end of the first coil unit via the full-pitch hairpin coil group, and the third coil unit is a plurality The third coil unit includes a group of full-pitch hairpin coils arranged in series, the third coil unit spans the e-th layer and the f-th layer, the starting end of the third coil unit is connected to the end of the second coil unit via a group of long-pitch hairpin coils, the fourth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, the plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils are arranged alternately in series, the fourth coil unit spans the g-th layer and the g-th layer, and the fourth coil unit is connected to the end of the third coil unit via a group of full-pitch hairpin coils.

[0010] Furthermore, each stator slot is divided into nine housing layers, and from the slot opening to the slot bottom of the stator slot, the layers are, in order, a, b, c, d, e, f, g, h, and i, and the first branch winding includes a first coil unit, a second coil unit, a third coil unit, a fourth coil unit, and a fifth coil unit. The first coil unit includes one S-shaped lead coil group and a plurality of full-pitch hairpin coil groups, the S-shaped lead coil group is located at the starting end of the first coil unit and is sequentially connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit is provided spanning the a-th layer and the b-th layer housing layer, the second coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the second coil unit is provided spanning the c-th layer housing layer and the d-th layer housing layer, the starting end of the second coil unit is connected to the end of the first coil unit via the full-pitch hairpin coil group, the third coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the third coil unit is provided spanning the e-th layer housing layer and the f-th layer housing layer, and The starting end of the third coil unit is connected to the end of the second coil unit via a long-pitch hairpin coil group, the fourth coil unit includes a plurality of sequentially series-connected full-pitch hairpin coil groups, the fourth coil unit is provided spanning the g-th layer and the h-th layer, the starting end of the fourth coil unit is connected to the end of the third coil unit via a full-pitch hairpin coil group, the fifth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils are sequentially and alternately series-connected, the fifth coil unit is provided spanning the i-th layer and the i-th layer, and the fifth coil unit is connected to the end of the fourth coil unit via a full-pitch hairpin coil group.

[0011] Furthermore, the first branch winding and the second branch winding are connected in series or in parallel.

[0012] Furthermore, the U-phase winding, the V-phase winding, and the W-phase winding are connected using either a star connection or a delta connection method.

[0013] In another aspect of the present invention, a motor is disclosed which includes a rotor assembly and the stator assembly, wherein the rotor assembly is coaxially mounted inside the stator assembly. [Effects of the Invention]

[0014] The advantages and beneficial effects of the present invention are as follows.

[0015] The stator assembly of the present invention enables short-pitch connection of odd-numbered layer flat wire windings, significantly reducing the 5th and 7th harmonics of the stator windings and improving the motor's torque pulsation and noise performance. Furthermore, in this stator assembly, the same layer of hairpin coils are located only on the radially outer side of the stator slot, occupying only the radially outer space of the stator slot and not the radially inner space. This allows the rotor assembly to be assembled on either side of the stator assembly, improving the flexibility of motor assembly. In addition, since the first branch winding and the second branch winding are formed by connecting the same number and type of coils in series, it is possible to achieve no circulating current or phase difference between branches. As a result, excess heat generation during motor operation is avoided, further improving the motor's operating efficiency and reliability. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a radial cross-sectional view of a stator assembly in one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of the arrangement of U-phase windings in a stator slot in one embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of the U-phase winding connection in one embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram of the structure of a full-pitch hairpin coil group in one embodiment of the present invention. [Figure 5] Figure 5 is a schematic diagram of the structure of a long-pitch hairpin coil group in one embodiment of the present invention. [Figure 6]FIG. 6 is a schematic structural diagram of an S-shaped extraction coil group in one embodiment of the present invention. [Figure 7] FIG. 7 is a schematic structural diagram in which three phases are connected in a delta connection method. [Figure 8] FIG. 8 is a schematic structural diagram in which three phases are connected in a star connection method. [Figure 9] FIG. 9 is a schematic layout diagram of the U-phase winding in the stator slot in another embodiment of the present invention. [Figure 10] FIG. 10 is a schematic layout diagram of the U-phase winding in the stator slot in yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] By reading the following detailed description of the preferred embodiments, various other advantages and merits will become apparent to those skilled in the art. The drawings are only for illustrating the preferred embodiments and should not be construed as limiting the present invention. Also, throughout the drawings, the same parts are denoted by the same reference numerals.

[0018] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments of the present invention are within the protection scope of the present invention.

[0019] Hereinafter, with reference to the drawings, the technical solutions according to each embodiment of the present invention will be described in detail.

[0020] In one embodiment of the present invention, a stator assembly is provided. As shown in FIG. 1, the stator assembly includes a stator core 1 and a stator winding 3, and the stator winding 3 includes a U-phase winding, a V-phase winding, and a W-phase winding.

[0021] The inner circumferential surface of the stator core 1 is provided with n stator slots 2, each stator slot 2 opening toward the axis of the stator core, and each stator slot 2 is divided into m layers along the radial direction of the stator core 1, with the layer closest to the slot opening being the starting layer and the layer closest to the slot bottom being the ending layer (i.e., the mth layer), where n is a multiple of 6 and m is an odd number greater than 3, and the U-phase winding is provided within the stator slot 2, provided in the same layer within the mth layer, and provided across layers within the remaining layers. In this way, short-pitch connections of odd-numbered stator windings are realized, and the 5th and 7th harmonics of the stator windings can be effectively attenuated.

[0022] What needs to be explained is that for a winding with q = number of stator slots / 2 * number of pole pairs * number of phases = 2, short-pitch connection means that each phase of the motor is distributed within three adjacent stator slots, while full-pitch connection means that each phase of the motor is distributed within two adjacent stator slots.

[0023] Furthermore, the U-phase winding includes a first branch winding and a second branch winding, that is, the first branch winding and the second branch winding are provided within the stator slot, and the first branch winding and the second branch winding are formed by connecting the same number and type of coils in series, thereby achieving no circulating current or phase difference between branches. The V-phase winding is obtained by rotating the U-phase winding 120° clockwise, and the W-phase winding is obtained by rotating the U-phase winding 240° clockwise.

[0024] Specifically, the first branch winding includes a first coil unit and a second (m-1) / 2 coil unit arranged in series, the first coil unit spans the first and second accommodating layers, that is, it spans layers, the first coil unit includes a group of S-shaped lead coils located at the starting end and a group of full-pitch hairpin coils arranged in series, the second coil unit spans the third and fourth accommodating layers, the second coil unit includes a group of full-pitch hairpin coils arranged in series, the starting end of the second coil is connected to the end of the first coil unit via a group of long-pitch hairpin coils or a group of full-pitch hairpin coils, and by analogy, the (m-1) / 2-1 coil unit spans the m-2 accommodating layer and the m-1 accommodating layer The (m-1) / 2-1 coil unit spans the m-th layer and the m-th layer, that is, it is provided in the same layer, and the (m-1) / 2 coil unit is connected to the end of the (m-1) / 2-2 coil unit via a long-pitch hairpin coil group or a full-pitch hairpin coil group. The (m-1) / 2 coil unit consists of a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, with the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils being connected alternately in series. The (m-1) / 2 coil unit spans the m-th layer and the m-th layer, that is, it is provided in the same layer, and the (m-1) / 2 coil unit is connected to the end of the (m-1) / 2-1 coil unit via a full-pitch hairpin coil group. As shown in Figures 4 to 6, a full-pitch hairpin coil group is obtained by staggering the positions of two full-pitch hairpin coils, a long-pitch hairpin coil group is obtained by staggering the positions of two long-pitch hairpin coils, and an S-shaped draw coil group is obtained by staggering the positions of two S-shaped draw coils.

[0025] With the stator winding structure described above, since the same-layer hairpin coils are formed only on the radially outer side of the stator slot, flexible assembly of the rotor assembly is facilitated. Specifically, the same-layer hairpin coils connected to the winding exist only in the m-th layer and its outer layer space, and all welded ends of the stator winding are full-pitch hairpin coils, while both long-pitch and short-pitch hairpin coils exist at the non-welded ends of the stator winding. Furthermore, the three-phase lead wires and three-phase neutral points of this winding connection method are distributed and concentrated in the same layer space, eliminating the need for complex busbars. Lead wires can be easily drawn by simply bending flat copper wires, simplifying the structure and manufacturing process of the stator assembly and further reducing the production cost of the motor.

[0026] In summary, the stator assembly of this embodiment achieves short-pitch connections of odd-numbered layers of flat wire windings, significantly reducing the 5th and 7th harmonics of the stator windings and improving the motor's torque pulsation and noise performance. Furthermore, in this stator assembly, the same layer of hairpin coils are located only on the radially outer side of the stator slot, occupying only the radially outer space of the stator slot and not the radially inner space. This allows the rotor assembly to be assembled on either side of the stator assembly, improving the flexibility of motor assembly. In addition, since the first branch winding and the second branch winding are formed by connecting the same number and type of coils in series, it is possible to achieve no circulating current or phase difference between branches. As a result, excess heat generation during motor operation is avoided, further improving the motor's operating efficiency and reliability.

[0027] Of these, the radially outer side of the stator slot is the side of the stator slot that is farther from the axis of the stator core along the radial direction of the stator core, that is, the outside of the m-th layer housing, and the radially inner side of the stator slot is the side of the stator slot that is closer to the axis of the stator core along the radial direction of the stator core, that is, the inside of the m-th layer housing.

[0028] In this embodiment, the number of stator slots is 48, the number of poles is 2p=8, and the number of slots per pole per phase is q=2. As shown in Figures 1 to 3, each stator slot is divided into 5 housing layers, and from the slot opening to the slot bottom of the stator slot are, in order, the a, b, c, d, and e layers, and the first branch winding includes the first coil unit, the second coil unit, and the third coil unit.

[0029] The first coil unit includes one S-shaped lead coil group and multiple full-pitch hairpin coil groups, with the S-shaped lead coil group located at the beginning of the first coil unit and sequentially connected in series with the multiple full-pitch hairpin coil groups, and the first coil unit is provided spanning the a-layer and b-layer housings. The second coil unit includes multiple sequentially connected full-pitch hairpin coil groups, and the second coil unit is provided spanning the c-layer and d-layer housings, with the beginning of the second coil unit connected to the end of the first coil unit via a long-pitch hairpin coil group. The third coil unit includes multiple short-pitch hairpin coils and multiple long-pitch hairpin coils, with the multiple short-pitch hairpin coils and multiple long-pitch hairpin coils sequentially and alternately connected in series, and the third coil unit is provided spanning the e-layer and e-layer housings, and the third coil unit is connected to the end of the second coil unit via a full-pitch hairpin coil group.

[0030] Specifically, the coil connection routes from the positive inlet terminal to the negative outlet terminal in the first branch winding are, in order: 1a, 7b, 13a, 19b, 25a, 31b, 37a, 43b, 2c, 8d, 14c, 20d, 26c, 32d, 38c, 44d, 2e, 44e, 39e, 33e, 26e, 20e, 15e, 9e, 3d, 45c, 39d, 33c, 27d, 21c, 15d, 9c, 2b, 44a, 38b, 32a, 26b, 20a, 14b, 8a. Yes, the coil connection routes from the positive inlet terminal to the negative outlet terminal in the second branch winding are, in order: 2a, 8b, 14a, 20b, 26a, 32b, 38a, 44b, 3c, 9d, 15c, 21d, 27c, 33d, 39c, 45d, 3e, 45e, 38e, 32e, 27e, 21e, 14e, 8e, 2d, 44c, 38d, 32c, 26d, 20c, 14d, 8c, 1b, 43a, 37b, 31a, 25b, 19a, 13b, and 7a.

[0031] In this way, the windings of each phase are concentrated within the stator slots, eliminating the problems caused by spaced-out arrangements. This reduces the complexity of winding installation and facilitates the realization of automated winding arrangement.

[0032] Furthermore, in the third coil unit, the long-pitch hairpin coil and the short-pitch hairpin coil are skewed by the same distance. This ensures that automated production of both long-pitch and short-pitch hairpin coils is possible.

[0033] Of course, connecting the lead wire ends of U1 and X1 in Figure 2, and connecting the lead wire ends of U2 and X2, and then cutting them as lead wires of the stator winding at the e-th layer winding at the welded end of the stator winding is also within the scope of protection of the present invention.

[0034] In another embodiment, as shown in Figure 9, each stator slot is divided into seven housing layers, from the slot opening to the slot bottom of the stator slot being, in order, layer a, layer b, layer c, layer d, layer e, layer f, and layer g, and the first branch winding includes a first coil unit, a second coil unit, a third coil unit, and a fourth coil unit.

[0035] Specifically, the first coil unit includes one S-shaped lead coil group and multiple full-pitch hairpin coil groups, the S-shaped lead coil group is located at the beginning of the first coil unit and is sequentially connected in series with the multiple full-pitch hairpin coil groups, the first coil unit spans the a-layer housing layer and the b-layer housing layer, the second coil unit includes multiple sequentially connected full-pitch hairpin coil groups, the second coil unit spans the c-layer housing layer and the d-layer housing layer, the beginning of the second coil unit is connected to the end of the first coil unit via the full-pitch hairpin coil group, and the third coil unit is multiple The coil unit includes a group of full-pitch hairpin coils arranged in series in sequence, with the third coil unit spanning the e-th layer and the f-th layer, and the beginning of the third coil unit connected to the end of the second coil unit via a group of long-pitch hairpin coils. The fourth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, with the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils arranged alternately in series in sequence, with the fourth coil unit spanning the g-th layer and the g-th layer, and the fourth coil unit connected to the end of the third coil unit via a group of full-pitch hairpin coils.

[0036] In other embodiments, as shown in Figure 10, each stator slot is divided into nine housing layers, and from the slot opening to the slot bottom of the stator slot are, in order, the a, b, c, d, e, f, g, h, and i layers, and the first branch winding includes the first coil unit, the second coil unit, the third coil unit, the fourth coil unit, and the fifth coil unit.

[0037] Specifically, the first coil unit includes one S-shaped lead coil group and multiple full-pitch hairpin coil groups, with the S-shaped lead coil group located at the beginning of the first coil unit and sequentially connected in series with the multiple full-pitch hairpin coil groups, and the first coil unit is provided spanning the a-layer and b-layer housings; the second coil unit includes multiple sequentially connected full-pitch hairpin coil groups, and the second coil unit is provided spanning the c-layer and d-layer housings, with the beginning of the second coil unit connected to the end of the first coil unit via the full-pitch hairpin coil group; and the third coil unit includes multiple sequentially connected full-pitch hairpin coil groups, and the third coil unit is provided spanning the e-layer and f-layer housings. The starting end of the third coil unit is connected to the end of the second coil unit via a long-pitch hairpin coil group, the fourth coil unit includes a plurality of sequentially series-connected full-pitch hairpin coil groups, the fourth coil unit is provided spanning the g-th layer and the h-th layer, the starting end of the fourth coil unit is connected to the end of the third coil unit via a full-pitch hairpin coil group, the fifth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, the plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils are sequentially and alternately series-connected, the fifth coil unit is provided spanning the i-th layer and the i-th layer, and the fifth coil unit is connected to the end of the fourth coil unit via a full-pitch hairpin coil group.

[0038] In this embodiment, the first branch winding and the second branch winding are connected in series or in parallel.

[0039] Then, as shown in Figures 7 and 8, the U-phase winding, V-phase winding, and W-phase winding are connected using either a star connection or a delta connection method to finally form the stator winding.

[0040] In another embodiment of the present invention, a motor is provided which comprises a rotor assembly and the stator assembly of the above embodiment, wherein the rotor assembly is coaxially mounted inside the stator assembly. The motor has advantages such as low vibration and noise, high operating efficiency, high reliability, flexible assembly, simple manufacturing process, and low cost.

[0041] The above is merely a specific embodiment of the present invention, and those skilled in the art can make further improvements or modifications based on the above examples under the above teachings of the present invention. Those skilled in the art should understand that the above specific description is intended to better interpret the purpose of the present invention, and that the scope of protection of the present invention is based on the scope of protection of the claims. [Explanation of symbols]

[0042] 1 Stator core, 2 Stator slots, 3 Stator windings

Claims

1. A stator assembly comprising a stator core and stator windings, wherein the stator windings include U-phase windings, V-phase windings and W-phase windings. The inner circumferential surface of the stator core is provided with n stator slots, each stator slot is divided into m layers along the radial direction of the stator core, the U-phase winding is provided within the stator slot, and within the m-th layer near the bottom of the stator slot, it is provided in the same layer, and within the remaining layers, it is provided across layers, with hairpin coils of the same layer only on the radially outer side of the stator slot, where n is a multiple of 6 and m is an odd number greater than 3. A stator assembly characterized in that the U-phase winding includes a first branch winding and a second branch winding, the first branch winding and the second branch winding are formed by connecting the same number and type of coils in series, the V-phase winding is obtained by rotating the U-phase winding clockwise by 120°, and the W-phase winding is obtained by rotating the U-phase winding clockwise by 240°.

2. Each stator slot is divided into five housing layers, and from the slot opening to the slot bottom of the stator slot are, in order, layer a, layer b, layer c, layer d, and layer e, and the first branch winding includes a first coil unit, a second coil unit, and a third coil unit. The stator assembly according to claim 1, wherein the first coil unit includes one S-shaped lead coil group and a plurality of full-pitch hairpin coil groups, the S-shaped lead coil group is located at the starting end of the first coil unit and is sequentially connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit is provided spanning the a-th layer housing layer and the b-th layer housing layer, the second coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the second coil unit is provided spanning the c-th layer housing layer and the d-th layer housing layer, the starting end of the second coil unit is connected to the end of the first coil unit via a long-pitch hairpin coil group, and the third coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, the plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils are sequentially and alternately connected in series, the third coil unit is provided spanning the e-th layer housing layer and the e-th layer housing layer, and the third coil unit is connected to the end of the second coil unit via a full-pitch hairpin coil group.

3. The coil connection routes from the positive inlet terminal to the negative outlet terminal in the first branch winding are, in order, 1a, 7b, 13a, 19b, 25a, 31b, 37a, 43b, 2c, 8d, 14c, 20d, 26c, 32d, 38c, 44d, 2e, 44e, 39e, 33e, 26e, 20e, 15e, 9e, 3d, 45c, 39d, 33c, 27d, 21c, 15d, 9c, 2b, 44a, 38b, 32a, 26b, 20a, 14b, 8a, and in the second branch winding... The stator assembly according to claim 2, characterized in that the coil connection routes from the positive inlet terminal to the negative outlet terminal are, in order, 2a, 8b, 14a, 20b, 26a, 32b, 38a, 44b, 3c, 9d, 15c, 21d, 27c, 33d, 39c, 45d, 3e, 45e, 38e, 32e, 27e, 21e, 14e, 8e, 2d, 44c, 38d, 32c, 26d, 20c, 14d, 8c, 1b, 43a, 37b, 31a, 25b, 19a, 13b, and 7a.

4. The stator assembly according to claim 2, characterized in that, in the third coil unit, the long-pitch hairpin coil and the short-pitch hairpin coil are skewed by the same distance.

5. Each stator slot is divided into seven housing layers, and from the slot opening to the slot bottom of the stator slot are, in order, the a, b, c, d, e, f, and g layers, and the first branch winding includes a first coil unit, a second coil unit, a third coil unit, and a fourth coil unit. The first coil unit includes one S-shaped lead coil group and a plurality of full-pitch hairpin coil groups, the S-shaped lead coil group is located at the starting end of the first coil unit and is sequentially connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit is provided spanning the a-layer housing layer and the b-layer housing layer, the second coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the second coil unit is provided spanning the c-layer housing layer and the d-layer housing layer, the starting end of the second coil unit is connected to the end of the first coil unit via the full-pitch hairpin coil group, and the third coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups The stator assembly according to claim 1, comprising a group of hairpin coils, wherein the third coil unit spans the housing layer of the e-th layer and the housing layer of the f-th layer, the starting end of the third coil unit is connected to the end of the second coil unit via a group of long-pitch hairpin coils, and the fourth coil unit comprises a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, wherein the plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils are sequentially and alternately arranged in series, the fourth coil unit spans the housing layer of the g-th layer and the housing layer of the g-th layer, and the fourth coil unit is connected to the end of the third coil unit via a group of full-pitch hairpin coils.

6. Each stator slot is divided into nine housing layers, and from the slot opening to the slot bottom of the stator slot, the layers are, in order, a, b, c, d, e, f, g, h, and i, and the first branch winding includes a first coil unit, a second coil unit, a third coil unit, a fourth coil unit, and a fifth coil unit. The first coil unit includes one S-shaped lead coil group and a plurality of full-pitch hairpin coil groups, the S-shaped lead coil group is located at the starting end of the first coil unit and is sequentially connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit is provided spanning the a-layer housing layer and the b-layer housing layer, the second coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the second coil unit is provided spanning the c-layer housing layer and the d-layer housing layer, the starting end of the second coil unit is connected to the end of the first coil unit via the full-pitch hairpin coil group, the third coil unit includes a plurality of sequentially connected full-pitch hairpin coil groups, the third coil unit is provided spanning the e-layer housing layer and the f-layer housing layer, and the starting end of the third coil unit is The stator assembly according to claim 1, characterized in that the end of the second coil unit is connected via a long-pitch hairpin coil group, the fourth coil unit includes a plurality of sequentially series-connected full-pitch hairpin coil groups, the fourth coil unit is provided spanning the g-th layer housing layer and the h-th layer housing layer, the start end of the fourth coil unit is connected to the end of the third coil unit via a full-pitch hairpin coil group, the fifth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, the plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils are sequentially and alternately series-connected, the fifth coil unit is provided spanning the i-th layer housing layer and the i-th layer housing layer, and the fifth coil unit is connected to the end of the fourth coil unit via a full-pitch hairpin coil group.

7. The stator assembly according to any one of claims 1 to 6, characterized in that the first branch winding and the second branch winding are connected in series or in parallel.

8. The stator assembly according to any one of claims 1 to 6, characterized in that the U-phase winding, the V-phase winding, and the W-phase winding are connected by a star connection method or a delta connection method.

9. A motor comprising a rotor assembly and a stator assembly according to any one of claims 1 to 6, wherein the rotor assembly is coaxially provided inside the stator assembly.

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