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 more particularly to stator assemblies and motors. [Background technology]

[0002] Currently, most stator windings in drive motors use rectangular wire with an even number of layers. To better accommodate the technical requirements of various motors, it is necessary to use rectangular wire with an odd number of layers. Traditionally, rectangular wire windings with an odd number of layers use full-pitch connections, which means that hairpin coils in the same layer are present on both the welded and non-welded ends of the stator winding. When skewed, the hairpin coils in the same layer occupy the radially inner space of the stator slot, meaning the rotor assembly can only be assembled from one side of the stator assembly. Furthermore, the full-pitch connection structure increases the fifth- and seventh-order harmonic content in the motor, resulting in increased motor noise. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION In view of the above problems, a stator assembly and a motor are disclosed in the present invention to overcome or at least partially solve the above problems. [Means for solving the problem]

[0004] To achieve the above object, the present invention employs the following technical solutions.

[0005] In one aspect of the present invention, a stator assembly is disclosed, the stator assembly including a stator core and a stator winding, the stator winding including a U-phase winding, a V-phase winding, and a W-phase winding; n stator slots are provided on the inner circumferential surface of the stator core, and each stator slot is divided into m accommodation layers along the radial direction of the stator core, the U-phase winding is provided in the stator slot, and is provided in the same layer in the mth accommodation layer and is provided across the remaining accommodation layers, wherein 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, and 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 by 120° clockwise, and the W-phase winding is obtained by rotating the U-phase winding by 240° clockwise.

[0006] Furthermore, each stator slot is divided into five receiving layers, which are layer a, layer b, layer c, layer d, and layer e from the slot opening to the slot bottom of the stator slot, respectively; 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 drawer coil group and a plurality of full-pitch hairpin coil groups, the S-shaped drawer coil group being located at a starting end of the first coil unit and being connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit being provided across the a-th housing layer and the b-th housing layer; the second coil unit includes a plurality of full-pitch hairpin coil groups connected in series with the plurality of full-pitch hairpin coil groups, the second coil unit being provided across the c-th housing layer and the d-th housing layer, and the starting end of the second coil unit being connected to the end of the first coil unit via the 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, and the short-pitch hairpin coils and the long-pitch hairpin coils are alternately connected in series with the plurality of short-pitch hairpin coils; the third coil unit is provided across the e-th housing layer and the e-th housing layer, and the third coil unit is connected to the end of the second coil unit via the full-pitch hairpin coil group.

[0007] Furthermore, the coil connection route from the positive inlet end to the negative outlet end of the first branch winding is 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, in this order. The coil connection route from the positive inlet end to the negative outlet end of the second branch winding is, 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 receiving layers, and the layers from the slot opening to the slot bottom are layer a, layer b, layer c, layer d, layer e, layer f, and layer g, in this order; 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 drawer coil group and a plurality of full-pitch hairpin coil groups, the S-shaped drawer coil group being located at a starting end of the first coil unit and being serially connected to the plurality of full-pitch hairpin coil groups, the first coil unit being provided across an a-th housing layer and a b-th housing layer, the second coil unit including a plurality of full-pitch hairpin coil groups serially connected to the end of the first coil unit via the full-pitch hairpin coil group, the third coil unit including a plurality of full-pitch hairpin coil groups serially connected to the end of the first coil unit via the full-pitch hairpin coil group, the third coil unit is provided across the e-th layer and the f-th layer, and the starting end of the third coil unit is connected to the end of the second coil unit via the long-pitch hairpin coil group; the fourth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, and the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils are alternately connected in series; the fourth coil unit is provided across 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 the full-pitch hairpin coil group.

[0010] Furthermore, each stator slot is divided into nine receiving layers, and the layers from the slot opening to the slot bottom are layer a, layer b, layer c, layer d, layer e, layer f, layer g, layer h, and layer i, in that order; 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 drawer coil group and a plurality of full-pitch hairpin coil groups, the S-shaped drawer coil group being located at a starting end of the first coil unit and being serially connected to the plurality of full-pitch hairpin coil groups, the first coil unit being provided across an a-th housing layer and a b-th housing layer; the second coil unit includes a plurality of full-pitch hairpin coil groups serially connected to the c-th housing layer and a d-th housing layer, the starting end of the second coil unit being connected to the end of the first coil unit via the full-pitch hairpin coil group; the third coil unit includes a plurality of full-pitch hairpin coil groups serially connected to the f-th housing layer; The starting end of the third coil unit is connected to the ending end of the second coil unit via a long-pitch hairpin coil group, the fourth coil unit includes a plurality of full-pitch hairpin coil groups arranged in series, and the fourth coil unit is arranged across the gth storage layer and the hth storage layer, and the starting end of the fourth coil unit is connected to the ending 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, and the short-pitch hairpin coils and the long-pitch hairpin coils are arranged in series alternately, and the fifth coil unit is arranged across the ith storage layer and the ith storage layer, and the fifth coil unit is connected to the ending 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 in a star connection or a delta connection.

[0013] In another aspect of the present invention, a motor is disclosed that includes a rotor assembly and the above-described stator assembly, the rotor assembly being coaxially disposed within 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 achieves a short-pitch connection of an odd number of layers of rectangular wire windings, significantly reducing the fifth and seventh harmonics of the stator winding and improving the motor's torque ripple and noise performance. Furthermore, in this stator assembly, the hairpin coils of the same layer 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 of the stator slot. This allows the rotor assembly to be assembled on either side of the stator assembly, improving motor assembly flexibility. Furthermore, the first and second branch windings are formed by connecting the same number and type of coils in series, eliminating circulating currents and phase differences between the branches. As a result, excessive heat generation during motor operation is avoided, further improving the motor's operating efficiency and reliability. [Brief explanation of the drawings]

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

[0017] Various other benefits and advantages will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Furthermore, like reference numerals refer to like parts throughout the drawings.

[0018] In order 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 corresponding drawings. Obviously, the described embodiments are only some embodiments of the present invention, and are 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, technical solutions according to various embodiments of the present invention will be described in detail with reference to the drawings.

[0020] In one embodiment of the present invention, a stator assembly is provided, and 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 opening toward the axial center of the stator core, and each stator slot 2 is divided into m storage layers along the radial direction of the stator core 1, with the storage layer closest to the slot opening of the stator slot 2 being the first layer and the storage layer closest to the slot bottom of the stator slot 2 being the last layer (i.e., the mth layer), where n is a multiple of 6 and m is an odd number greater than 3, and a U-phase winding is provided in the stator slot 2 and is provided in the same layer in the mth storage layer and is provided across layers in the remaining storage layers. In this way, a short-pitch connection of the stator windings in the odd-numbered layers is achieved, which can effectively attenuate the fifth and seventh harmonics of the stator winding.

[0022] It should be noted that for a winding with slots per pole per phase 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] 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 in the stator slots, and the first branch winding and the second branch winding are formed by connecting the same number and type of coils in series, thereby eliminating circulating current and phase difference between the 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 the first coil unit to the (m-1) / 2-th coil unit connected in series in sequence, the first coil unit being provided across the first and second housing layers, i.e., across layers, and including one S-shaped pull-out coil group at its starting end and a plurality of full-pitch hairpin coil groups connected in series in sequence; the second coil unit being provided across the third and fourth housing layers, including a plurality of full-pitch hairpin coil groups connected in series in sequence, the starting end of the second coil being connected to the end of the first coil unit via the long-pitch hairpin coil group or the full-pitch hairpin coil group; by analogy therewith, the (m-1) / 2-1-th coil unit is provided across the m-2-th housing layer and the m-1-th housing layer. The (m-1) / 2-1-th coil unit is arranged across the m-th storage layer and the m-th storage layer, and the (m-1) / 2-1-th coil unit includes a plurality of full-pitch hairpin coil groups arranged in series, and the starting end of the (m-1) / 2-1-th coil unit is connected to the end of the (m-1) / 2-2-th coil unit via a long-pitch hairpin coil group or a full-pitch hairpin coil group, and the (m-1) / 2-th coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, and the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils are arranged in series alternately, and the (m-1) / 2-th coil unit is arranged across the m-th storage layer and the m-th storage layer, i.e., it is arranged in the same layer, and the (m-1) / 2-1-th coil unit is connected to the end of the (m-1) / 2-1-th coil unit via a full-pitch hairpin coil group. As shown in Figures 4 to 6, the full-pitch hairpin coil group is obtained by arranging two full-pitch hairpin coils in a staggered position, the long-pitch hairpin coil group is obtained by arranging two long-pitch hairpin coils in a staggered position, and the S-shaped drawer coil group is obtained by arranging two S-shaped drawer coils in a staggered position.

[0025] The stator winding with the above structure and installation has same-layer hairpin coils formed only radially outside the stator slots, which facilitates flexible assembly of the rotor assembly. That is, the same-layer hairpin coils connected to the winding are only present in the mth layer and its outer layer space, and the welded ends of the stator winding are all full-pitch hairpin coils, while the non-welded ends of the stator winding have both long-pitch and short-pitch hairpin coils. Furthermore, the three-phase lead-out wires and three-phase neutral point of this winding connection method are distributed and concentrated in the same layer space, eliminating the need for complex busbars and allowing the lead-out wires to be simply bent by flat copper wire. This simplifies the structure and manufacturing process of the stator assembly and further reduces motor production costs.

[0026] In summary, the stator assembly of this embodiment achieves a short-pitch connection of the odd number of layers of rectangular wire windings, significantly reducing the fifth and seventh harmonics of the stator winding and improving the motor's torque ripple and noise performance. Furthermore, in this stator assembly, the same layer of hairpin coils is 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 of the stator slot. This allows the rotor assembly to be assembled on either side of the stator assembly, improving motor assembly flexibility. Furthermore, because the first and second branch windings are formed by connecting the same number and type of coils in series, there is no circulating current or phase difference between the branches. This results in reduced heat generation during motor operation and improved motor 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, i.e., the outside of the mth layer of accommodating layer, 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, i.e., the inside of the mth layer of accommodating layer.

[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 FIGS. 1 to 3, each stator slot is divided into five accommodation layers, which are layer a, layer b, layer c, layer d, and layer e from the slot opening to the slot bottom, respectively. The first branch winding includes a first coil unit, a second coil unit, and a third coil unit.

[0029] The first coil unit includes one S-shaped drawer coil group and a plurality of full-pitch hairpin coil groups, the S-shaped drawer coil group being located at a starting end of the first coil unit and being connected in series with the plurality of full-pitch hairpin coil groups, the first coil unit being provided across the a-th housing layer and the b-th housing layer, the second coil unit including a plurality of full-pitch hairpin coil groups connected in series with the plurality of full-pitch hairpin coil groups being provided across the c-th housing layer and the d-th housing layer, the starting end of the second coil unit being connected to a terminal end of the first coil unit via the long-pitch hairpin coil group, the third coil unit including 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 being connected in series alternately, the third coil unit being provided across the e-th housing layer and the e-th housing layer, the third coil unit being connected to a terminal end of the second coil unit via the full-pitch hairpin coil group.

[0030] Specifically, the coil connection route from the positive inlet end to the negative outlet end of the first branch winding is, 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 end to the negative outlet end of the second branch winding are 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, in this order.

[0031] In this way, the windings of each phase are arranged in a concentrated manner within the stator slots, and there are no problems caused by spaced arrangements, which reduces the complexity of winding installation and makes it easier to realize automated winding arrangements.

[0032] In the third coil unit, the long-pitch hairpin coil and the short-pitch hairpin coil are skewed by the same distance, which ensures that the long-pitch hairpin coil and the short-pitch hairpin coil can be produced automatically.

[0033] Of course, it is also within the scope of protection of the present invention to connect the lead wire ends of U1 and X1 in Figure 2, and also connect the lead wire ends of U2 and X2, and then cut them as lead wires of the stator winding at the winding of the eth layer at the welding end of the stator winding.

[0034] In another embodiment, as shown in FIG. 9 , each stator slot is divided into seven receiving layers, which are layer a, layer b, layer c, layer d, layer e, layer f, and layer g from the slot opening to the slot bottom, respectively, 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 draw coil group and a plurality of full-pitch hairpin coil groups, the S-shaped draw coil group being located at the beginning of the first coil unit and being serially connected to the plurality of full-pitch hairpin coil groups, the first coil unit being provided across the a-th housing layer and the b-th housing layer, the second coil unit including a plurality of serially connected full-pitch hairpin coil groups being provided across the c-th housing layer and the d-th housing layer, the beginning of the second coil unit being connected to the end of the first coil unit via the full-pitch hairpin coil group, and the third coil unit including a plurality of full-pitch hairpin coil groups being serially connected to the end of the first coil unit via the full-pitch hairpin coil group. the third coil unit is provided across the e-th and f-th storage layers, and the starting end of the third coil unit is connected to the end of the second coil unit via the long-pitch hairpin coil group; the fourth coil unit includes a plurality of short-pitch hairpin coils and a plurality of long-pitch hairpin coils, and the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils are sequentially and alternately arranged in series; the fourth coil unit is provided across the g-th and g-th storage layers, and the fourth coil unit is connected to the end of the third coil unit via the full-pitch hairpin coil group.

[0036] In another embodiment, as shown in FIG. 10 , each stator slot is divided into nine receiving layers, which are layer a, layer b, layer c, layer d, layer e, layer f, layer g, layer h, and layer i from the slot opening to the slot bottom, respectively, 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.

[0037] Specifically, the first coil unit includes one S-shaped draw coil group and a plurality of full-pitch hairpin coil groups, the S-shaped draw coil group being located at the beginning of the first coil unit and being serially connected to the plurality of full-pitch hairpin coil groups, the first coil unit being provided across the a-th housing layer and the b-th housing layer, the second coil unit including a plurality of full-pitch hairpin coil groups serially connected to the c-th housing layer and the d-th housing layer, the beginning of the second coil unit being connected to the end of the first coil unit via the full-pitch hairpin coil group, the third coil unit including a plurality of full-pitch hairpin coil groups serially connected to the f-th housing layer, The starting end of the third coil unit is connected to the ending end of the second coil unit via a long-pitch hairpin coil group, the fourth coil unit includes a plurality of full-pitch hairpin coil groups arranged in series in sequence, and the fourth coil unit is arranged across the gth storage layer and the hth storage layer, and the starting end of the fourth coil unit is connected to the ending end of the third coil unit via the 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, and the short-pitch hairpin coils and the long-pitch hairpin coils are arranged in series in an alternating sequence, and the fifth coil unit is arranged across the ith storage layer and the ith storage layer, and the fifth coil unit is connected to the ending end of the fourth coil unit via the 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] As shown in FIGS. 7 and 8, the U-phase winding, the V-phase winding, and the W-phase winding are connected in a star connection or a delta connection to finally form the stator winding.

[0040] In another embodiment of the present invention, there is provided a motor, the motor including a rotor assembly and the stator assembly of the above embodiment, the rotor assembly being coaxially disposed inside the stator assembly, the motor having advantages of low vibration noise, high operating efficiency, high reliability, flexible assembly, simple manufacturing process and low cost.

[0041] The above are merely specific embodiments of the present invention, and those skilled in the art can make other improvements or modifications based on the above teachings of the present invention. Those skilled in the art should understand that the above specific descriptions are for better understanding the purpose of the present invention, and the protection scope of the present invention is based on the protection scope of the claims. [Explanation of symbols]

[0042] 1. Stator core, 2. Stator slot, 3. Stator winding

Claims

1. a stator assembly including a stator core and stator windings, the stator windings including a U-phase winding, a V-phase winding, and a W-phase winding; n stator slots are provided on the inner circumferential surface of the stator core, each stator slot is divided into m accommodation layers along the radial direction of the stator core, the U-phase winding is provided in the stator slot, and is provided in the same layer in the mth accommodation layer and is provided across the remaining accommodation layers, wherein 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 in series the same number and type of coils, the V-phase winding being obtained by rotating the U-phase winding by 120° clockwise, and the W-phase winding being obtained by rotating the U-phase winding by 240° clockwise.

2. Each stator slot is divided into five receiving layers, which are layer a, layer b, layer c, layer d, and layer e from the slot opening to the slot bottom, respectively. The first branch winding includes a first coil unit, a second coil unit, and a third coil unit.

2. The stator assembly according to claim 1, wherein the first coil unit includes one S-shaped draw coil group and a plurality of full-pitch hairpin coil groups, the S-shaped draw coil group being located at a starting end of the first coil unit and being connected to the plurality of full-pitch hairpin coil groups in series, the first coil unit being provided across an a-th housing layer and a b-th housing layer, the second coil unit including a plurality of full-pitch hairpin coil groups connected in series, the second coil unit being provided across an c-th housing layer and a d-th housing layer, and the starting end of the second coil unit being connected to the end of the first coil unit via a long-pitch hairpin coil group, the third coil unit including 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 being connected in series alternately, the third coil unit being provided across an e-th housing layer and a e-th housing layer, and the third coil unit being connected to the end of the second coil unit via a full-pitch hairpin coil group.

3. The coil connection route from the positive inlet end to the negative outlet end of the first branch winding is 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, respectively.

3. The stator assembly according to claim 2, wherein the coil connection routes from the positive inlet end to the negative outlet end of the stator are 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, in this order.

4. 3. The stator assembly of claim 2, wherein 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 receiving layers, which are layer a, layer b, layer c, layer d, layer e, layer f, and layer g from the slot opening to the slot bottom, respectively; 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 drawer coil group and a plurality of full-pitch hairpin coil groups, the S-shaped drawer coil group being located at a starting end of the first coil unit and being connected to the plurality of full-pitch hairpin coil groups in series, the first coil unit being provided across an a-th encasing layer and a b-th encasing layer, the second coil unit including a plurality of full-pitch hairpin coil groups connected in series, the second coil unit being provided across an c-th encasing layer and a d-th encasing layer, the starting end of the second coil unit being connected to the end of the first coil unit via the full-pitch hairpin coil group, and the third coil unit including a plurality of full-pitch hairpin coil groups connected in series 2. The stator assembly of claim 1, wherein the third coil unit includes a group of full-pitch hairpin coils, the third coil unit being arranged across the e-th and f-th housing layers, and a starting end of the third coil unit being connected to a terminal end of the second coil unit via a group of long-pitch hairpin coils, the fourth coil unit including 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 being alternately arranged in series, the fourth coil unit being arranged across the g-th and g-th housing layers, and the fourth coil unit being connected to a terminal end of the third coil unit via a group of full-pitch hairpin coils.

6. Each stator slot is divided into nine receiving layers, which are arranged in order from the slot opening to the slot bottom, namely, layer a, layer b, layer c, layer d, layer e, layer f, layer g, layer h, and layer 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 drawer coil group and a plurality of full-pitch hairpin coil groups, the S-shaped drawer coil group being located at a starting end of the first coil unit and the plurality of full-pitch hairpin coil groups being sequentially connected in series, the first coil unit being provided across an a-th housing layer and a b-th housing layer, the second coil unit including a plurality of full-pitch hairpin coil groups being sequentially connected in series, the second coil unit being provided across an c-th housing layer and a d-th housing layer, the starting end of the second coil unit being connected to the end of the first coil unit via the full-pitch hairpin coil group, the third coil unit including a plurality of full-pitch hairpin coil groups being sequentially connected in series, the third coil unit being provided across an e-th housing layer and an f-th housing layer, the starting end of the third coil unit being 2. The stator assembly of claim 1, wherein the fourth coil unit is connected to an end of the second coil unit via a long-pitch hairpin coil group; the fourth coil unit includes a plurality of full-pitch hairpin coil groups arranged in series, the fourth coil unit is provided across the g-th housing layer and the h-th housing layer, and a starting end of the fourth coil unit is connected to an 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, and the plurality of short-pitch hairpin coils and the plurality of long-pitch hairpin coils are arranged in series alternately, the fifth coil unit is provided across the i-th housing layer and the i-th housing layer, and the fifth coil unit is connected to an end of the fourth coil unit via a full-pitch hairpin coil group.

7. 7. The stator assembly according to claim 1, wherein the first branch winding and the second branch winding are connected in series or in parallel.

8. 7. The stator assembly according to claim 1, wherein the U-phase winding, the V-phase winding, and the W-phase winding are connected in a star connection or a delta connection.

9. A motor comprising a rotor assembly and a stator assembly according to any one of claims 1 to 8, wherein the rotor assembly is coaxially arranged inside the stator assembly.

Images