Flat wire short-pitch winding with 72 slots, 8 poles and 3 parallel branches and motor

Abstract

The invention discloses a 72-slot 8-pole three-parallel-branch flat wire short-pitch winding and a motor, the 72-slot 8-pole three-parallel-branch flat wire short-pitch winding comprises a U-phase winding, a V-phase winding and a W-phase winding, the number of stator slots of the motor and the number of rotor poles meet the condition that the number of slots of each phase of each pole is 3, and the number of parallel branches of each phase of winding is 3; 2n layers of flat wires are arranged in a single stator slot, two adjacent layers of flat wires form a slot layer group, the two layers of flat wires of the same slot layer group correspond to three slot positions and are staggered by one slot, and the slot positions occupied by different slot layer groups are the same; the three slot positions of each pole and each layer respectively correspond to three parallel branches, the left slot, the middle slot and the right slot, the flat wire conductor in each slot layer group is bridged by two layers, the crown end span of the three parallel branches is a first preset span combination comprising at least three different spans, and the welding end span is a second preset span; the welding ends adopt the corresponding connection mode of left grooves, middle grooves and right grooves, 8n welding connections are formed, and the number of the corresponding connections of the three types of groove positions is 8n / 3. According to the invention, the power density and efficiency of the motor are improved.

Description

Technical Field

[0001] This invention relates to a flat wire short-pitch winding and a motor, and more particularly to a flat wire short-pitch winding and a motor with 72 slots, 8 poles, and 3 parallel branches. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the requirements for drive motors in terms of power density, operating efficiency, and vibration and noise (NVH) performance are becoming increasingly stringent. Hairpin flat wire motors, due to their advantages such as high slot fill factor, high power density, and good heat dissipation performance, are gradually becoming the mainstream technical solution.

[0003] In existing technologies, flat-wire motors using full-pitch windings suffer from high harmonic content, large torque fluctuations, high electromagnetic force density, and high-frequency eddy current losses, severely impacting the motor's NVH performance and operating efficiency. To address these issues, short-pitch windings have been gradually adopted. However, in motors with 3 parallel branches (3 slots per pole per phase, and 8 poles or multiples of 8), a new technical bottleneck arises: existing wave-wound winding schemes struggle to achieve balanced arrangement of parallel branches, leading to phase differences and potential imbalances between branches, easily generating large circulating currents. These circulating currents cause decreased motor power performance, increased additional losses, reduced efficiency, and even localized overheating, significantly reducing the motor's reliability and lifespan.

[0004] Furthermore, the inconsistent welding end span design of existing short-pitch windings makes tooling head shaping difficult and hinders large-scale production. Therefore, developing a flat wire winding that can suppress harmonics through short-pitch design, achieve balanced arrangement of three parallel branches, and optimize the production process has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to propose a 72-slot, 8-pole, 3-parallel-branch flat wire short-pitch winding and motor. By reducing harmonic content through short-pitch design, suppressing circulating current through balanced branch arrangement, and optimizing the production process through unified welding end span, the invention achieves a synergistic improvement in motor power density, efficiency, and NVH performance.

[0006] Technical solution: The present invention includes three-phase windings of U, V and W. The number of stator slots and rotor poles of the motor satisfy the requirement that there are 3 slots per pole per phase and 3 parallel branches per phase winding. There are 2n layers of flat wires in a single stator slot. Two adjacent layers of flat wires form a slot layer group. The two layers of flat wires in the same slot layer group correspond to 3 slots and are staggered by one slot. Different slot layer groups occupy the same slot position.

[0007] Each pole and each layer has 3 slots corresponding to 3 parallel branches, defined as left slot, middle slot and right slot. The flat wire conductor in each slot layer group is connected across two layers. The crown end span of the 3 parallel branches is a first preset span combination containing at least three different spans. The welding end span is a second preset span. The welding ends adopt the corresponding connection method of left slot to left slot, middle slot to middle slot, and right slot to right slot, forming a total of 8n welding connections. The number of connections corresponding to the three types of slots is 8n / 3.

[0008] The motor has 72 stator slots and 8 rotor poles.

[0009] The first preset span combination is a combination of at least three of the following: 8, 9, 10, 11, and 12, and the second preset span is 8.

[0010] Of the three parallel branches, one branch has a crown end span of 8, 10, 11, and 12, while the other two branches have crown end spans of 8, 9, 10, and 11.

[0011] Each parallel branch has a single-layer cross conductor. The span of the single-layer cross conductor is the same and it is located in the innermost or outermost layer. The torsion direction of the single-layer cross conductor is the direction of motor rotation or the opposite direction of motor rotation.

[0012] The V-phase winding is obtained by moving the U-phase winding along the motor rotation direction by a predetermined number of slots, and the W-phase winding is obtained by moving the V-phase winding along the motor rotation direction by the same predetermined number of slots; or, the V-phase winding is obtained by moving the U-phase winding along the motor rotation direction by a predetermined number of slots, and the W-phase winding is obtained by moving the V-phase winding along the motor rotation direction by the same predetermined number of slots, with the torsion direction of the same-layer cross conductor opposite to that of the V-phase winding; or, the V-phase winding is obtained by moving the U-phase winding along the motor rotation direction by a predetermined number of slots, with the torsion direction of the same-layer cross conductor opposite to that of the U-phase winding, and the W-phase winding is obtained by moving the U-phase winding along the motor rotation direction by twice the predetermined number of slots; or, the V-phase winding is obtained by moving the U-phase winding along the motor rotation direction by a predetermined number of slots, with the torsion direction of the same-layer cross conductor opposite to that of the U-phase winding, and the W-phase winding is obtained by moving the V-phase winding along the motor rotation direction by the predetermined number of slots.

[0013] The preset number of slots is matched with the number of slots per pole per phase, and the preset number of slots is 6.

[0014] The outgoing terminals and neutral points of each parallel branch are located on the innermost or outermost flat wire.

[0015] An electric motor includes a stator, a rotor, and a flat wire short-pitch winding with 72 slots, 8 poles, and 3 parallel branches, wherein the flat wire short-pitch winding is embedded in the stator slots and works with the rotor to realize electromagnetic energy conversion.

[0016] A method for winding a flat wire short-pitch winding, used to prepare a 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding, includes the following steps:

[0017] S1: The stator core is manufactured according to the specification that the number of stator slots and rotor poles meet the requirement of 3 slots per pole per phase, and the installation space for 2n layers of flat wires is preset in the stator slots;

[0018] S2: Divide the flat conductor into n slot layers in a way that two adjacent layers are grouped together. The two layers of flat conductor in the same slot layer group correspond to 3 slots and are staggered by one slot.

[0019] S3: Assign slots for three parallel branches according to the definitions of left slot, middle slot and right slot, and wind the crown end of each branch according to the first preset span combination, so that the crown end span of the three branches includes at least three different spans.

[0020] S4: Connect the welding ends of each branch in the manner of left slot-left slot, middle slot-middle slot, and right slot-right slot, ensuring that the span of the welding ends is the second preset span and that the number of the three types of connections is 8n / 3.

[0021] S5: Complete the three-phase winding.

[0022] Beneficial effects: The present invention has the following advantages:

[0023] (1) Significant harmonic suppression effect: Through the short-pitch design (slot layer group staggered arrangement) and the crown end design of multi-span combination, the harmonic content of the motor is effectively reduced, the torque fluctuation and high-frequency eddy current loss are reduced, the low-harmonic electromagnetic force density is significantly reduced, and the motor vibration noise (NVH) performance is greatly improved.

[0024] (2) The problem of circulating current is completely solved: Based on the parameter matching basis of "slot number per pole per phase = 3", the "left / middle / right slot" slot allocation and corresponding connection method are adopted to make the no-load back EMF amplitude and phase of the three parallel branches completely consistent, suppressing the generation of circulating current from the root, avoiding the decrease of motor efficiency and local overheating, and improving the reliability and service life of the motor.

[0025] (3) Production process optimization: The welding end span is uniformly fixed, which makes it easier for the tooling to twist and shape, reducing the difficulty of large-scale production; the span of the conductor in the same layer of each branch is the same, realizing material sharing and reducing manufacturing costs;

[0026] (4) High structural flexibility: It supports arbitrary combination of windings in different embodiments, and can realize the centralized arrangement of the output terminal and neutral point, optimizing the busbar space layout; the number of flat wire layers can be adjusted according to power requirements (2n layers), adapting to motor designs of different power levels; at the same time, it is compatible with a variety of slot pole number combinations that meet the requirement of "slot number per pole per phase = 3", making the protection range more reasonable;

[0027] (5) Synergistic improvement of power density and efficiency: The combination of flat wire structure with high slot fill factor and balanced branch design improves the power density of the motor while ensuring operating efficiency and meeting the core performance requirements of drive motors for new energy vehicles. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the U1 branch winding connection in Embodiment 2 of the present invention (solid lines represent crown ends, and dashed lines represent welded ends).

[0029] Figure 2 This is a schematic diagram of the U2 branch winding connection according to Embodiment 2 of the present invention;

[0030] Figure 3 This is a schematic diagram of the U3 branch winding connection in Embodiment 2 of the present invention;

[0031] Figure 4 This is a schematic diagram of the U1 branch winding connection in Embodiment 3 of the present invention;

[0032] Figure 5 This is a schematic diagram of the U2 branch winding connection in Embodiment 3 of the present invention;

[0033] Figure 6 This is a schematic diagram of the U3 branch winding connection in Embodiment 3 of the present invention. Detailed Implementation

[0034] The invention will now be further described with reference to the accompanying drawings.

[0035] Example 1

[0036] The 72-slot, 8-pole, 3-parallel-branch flat wire short-pitch winding of this embodiment includes three phases: U, V, and W. For the U-phase winding, the number of stator slots and rotor poles of the motor satisfy the condition that the number of slots per pole per phase = 3, that is, the number of slots / (number of poles × 3) = 3. The number of parallel branches of each phase winding is 3. This parameter matching relationship is the basis for achieving a balanced arrangement of the 3 branches and meets the design requirements of a high power density motor.

[0037] A single stator slot contains 2n layers of flat wires (n is a positive integer), radially labeled a, b, c, d, e, f… from the outside in. Two adjacent layers of flat wires form a slot group (e.g., ab group, cd group, etc.). Two layers of flat wires within the same slot group correspond to three slots, and the two layers are staggered by one slot. This staggered design achieves short-pitch winding functionality and effectively suppresses harmonics. The slot positions occupied by different slot groups remain consistent, ensuring the symmetry of the winding structure.

[0038] Each pole and each layer has three slots corresponding to three parallel branches, defined by their relative positions as left slot, middle slot, and right slot. This allocation method ensures that the branches are evenly distributed in space, laying the structural foundation for balanced branch distribution.

[0039] The crown end span of the three parallel branches adopts the first preset span combination, which includes at least three different spans. The harmonics are further reduced through span differentiation optimization. The welding end span of all branches is uniformly designed as the second preset span, which facilitates tooling to twist and shape, reduces the difficulty of production process, and improves the efficiency of large-scale production.

[0040] The welding ends adopt a corresponding connection method of "left slot-left slot", "middle slot-middle slot", and "right slot-right slot", forming a total of 8n welding connections (8n is divisible by 3), and the number of connections corresponding to the three types of slots is 8n / 3. This design ensures that the number of conductors, end lengths, and magnetic circuit paths of each parallel branch are completely consistent, realizing the synchronization of the amplitude and phase of the branch no-load back EMF, fundamentally suppressing the generation of circulating current. Each parallel branch has one same-layer cross conductor, which can be set in the innermost or outermost layer, and the span of the same-layer cross conductor in each phase and branch is the same, realizing material sharing and reducing the motor manufacturing cost.

[0041] The V-phase winding is obtained by moving the U-phase winding along the direction of motor rotation by a preset number of slots, and the W-phase winding is obtained by moving the V-phase winding along the direction of motor rotation by a preset number of slots. The preset number of slots matches the number of slots per pole and per phase to ensure the symmetrical distribution of the three-phase windings and avoid three-phase imbalance problems.

[0042] Example 2

[0043] This embodiment takes a 72-slot, 8-pole, 6-layer flat wire winding as an example. The number of stator slots is 72, the number of rotor poles is 8, the number of slots per pole per phase is 3, the number of parallel branches is 3, and there are 6 layers of flat wire in a single stator slot. The radial directions from the outside to the inside are a, b, c, d, e, and f. a and b are the first slot layer group, c and d are the second slot layer group, and e and f are the third slot layer group.

[0044] The first preset span combination is a combination of one branch with 8, 10, 11, and 12, and the other two branches with 8, 9, 10, and 11; the second preset span is 8; the preset number of slots is 6 (matching the number of slots per pole per phase).

[0045] The three branch windings of phase U are respectively as follows: Figure 1 , Figure 2 and Figure 3 As shown, there are 3 slots per layer of each pole, corresponding to 3 different branches. Based on the relative positions of these 3 slots, they can be defined as "left slot", "middle slot" and "right slot".

[0046] In branch U1, for the winding welding ends, a10→b2, c10→d2, e10→f2, b11→a19, d11→c19, f11→e19, e64→f56, and d65→c1 form 8 "right slot"-to-right slot connections, while a26→b18, c26→d18, e26→f18, b27→a35, d27→c35, f27→e35, c62→d54, and b63→a71 form 8 "left slot"-to-left slot connections. The circuits a45→b37, c45→d37, e45→f37, b46→a54, d46→c54, f46→e54, a63→b55, and f64→e72 achieve eight "middle slot"-to-middle slot connections. The windings of a single branch are evenly distributed in three slots, effectively avoiding phase differences between branches.

[0047] The winding of the parallel branch U1 of phase U is as follows: Figure 1 As shown, the solid lines represent the crown end and the dashed lines represent the welding end. The outgoing terminal U1 is in the innermost layer f64. In the same slot layer, the span of the crown end is a combination of 8, 10, 11, and 12, the span of the welding end is 8, and the neutral point X1 is in the innermost layer f56. The specific winding connection of branch U1 is as follows: f64→e72→f11→e19→f27→e35→f46→e54→d65→c1→d11→c19→d27→c35→d46→c54→b63→a71→b11→a19→b27→a35→b46→a54→a45→b37→a26→b18→a10→b2→a63→b55→c45→d37→c26→d18→c10→d2→c62→d54→e45→f37→e26→f18→e10→f2→e64→f56.

[0048] The winding of the parallel branch U2 of phase U is as follows: Figure 2 As shown, the outgoing terminal U2 is in the innermost layer f63. In the same slot layer, the span of the crown end is a combination of 8, 9, 10, and 11, the span of the welding end is 8, and the neutral point X2 is in the innermost layer f55. The specific winding connection of branch U1 is as follows: f63→e71→f10→e18→f29→e37→f45→e53→d64→c72→d10→c18→d29→c37→d45→c53→b65→a1→b10→a18→b29→a37→b45→a53→a44→b36→a28→b20→a9→b1→a62→b54→c44→d36→c28→d20→c9→d1→c64→d56→e44→f36→e28→f20→e9→f1→e63→f55.

[0049] The winding of the parallel branch U3 of phase U is as follows: Figure 3As shown, the outgoing terminal U3 is in the innermost layer f65. In the same slot layer, the span of the crown end is a combination of 8, 9, 10, and 11, the span of the welding end is 8, and the neutral point X3 is in the innermost layer f54. The specific winding connection of branch U3 is as follows: f65→e1→f9→e17→f28→e36→f47→e55→d63→c71→d9→c17→d28→c36→d47→c55→b64→a72→b9→a17→b28→a36→b47→a55→a46→b38→a27→b19→a8→b72→a64→b56→c46→d38→c27→d19→c8→d72→c63→d55→e46→f38→e27→f19→e8→f72→e62→f54.

[0050] The V-phase winding is obtained by moving the U-phase winding 6 slots along the direction of motor rotation, and the W-phase winding is obtained by moving the V-phase winding 6 slots along the direction of motor rotation.

[0051] Example 3

[0052] This embodiment takes a 72-slot, 8-pole, 6-layer flat wire motor as an example. Each pole and phase has 3 slots and 3 parallel branches. Each stator slot contains 6 layers of flat wire, radially numbered a, b, c, d, e, and f from the outside to the inside. a and b form the first slot layer group, c and d form the second slot layer group, and e and f form the third slot layer group. The three branch windings of phase U are as follows... Figure 4 , Figure 5 and Figure 6 As shown, each pole has 3 slots per layer, corresponding to 3 different branches. Based on the relative positions of these 3 slots, they can be defined as "left slot," "middle slot," and "right slot." In branch U1, for the winding welding ends, a10→b2, c10→d2, e10→f2, b11→a19, d11→c19, f11→e19, e64→f56, and d65→c1 form 8 "right slot"-"right slot" connections, while a26→b18, c26→d18, e26→f18, b27→a35, d27→c35, f27→e35, c62→d54, and b63→a71 form 8 "left slot"-"left slot" connections. The connections a45→b37, c45→d37, e45→f37, b46→a54, d46→c54, f46→e54, a63→b55, and f64→e72 achieve eight “middle slot”-to-middle slot connections. The windings of a single branch are evenly distributed in three slots, effectively avoiding phase differences between branches.

[0053] The winding of the parallel branch U1 of phase U is as follows: Figure 4As shown, the solid lines represent the crown end and the dashed lines represent the welding end. The outgoing terminal U1 is in the innermost layer f64. In the same slot layer, the span of the crown end is a combination of 8, 10, 11, and 12, the span of the welding end is 8, and the neutral point X1 is in the innermost layer f2. The specific winding connection of branch U1 is as follows: f64→e72→f11→e19→f27→e35→f46→e54→d65→c1→d11→c19→d27→c35→d46→c54→b63→a71→b11→a19→b27→a35→b46→a54→a63→b55→a45→b37→a26→b18→a10→b2→c62→d54→c45→d37→c26→d18→c10→d2→e64→f56→e45→f37→e26→f18→e10→f2.

[0054] The winding of the parallel branch U2 of phase U is as follows: Figure 5 As shown, the outgoing terminal U2 is in the innermost layer f63. In the same slot layer, the span of the crown end is a combination of 8, 9, 10, and 11, the span of the welding end is 8, and the neutral point X2 is in the innermost layer f1. The specific winding connection of branch U1 is as follows: f63→e71→f10→e18→f29→e37→f45→e53→d64→c72→d10→c18→d29→c37→d45→c53→b65→a1→b10→a18→b29→a37→b45→a53→a62→b54→a44→b36→a28→b20→a9→b1→c64→d56→c44→d36→c28→d20→c9→d1→e63→f55→e44→f36→e28→f20→e9→f1.

[0055] The winding of the parallel branch U3 of phase U is as follows: Figure 6 As shown, the outgoing terminal U3 is in the innermost layer f65. In the same slot layer, the span of the crown end is a combination of 8, 9, 10, and 11, the span of the welding end is 8, and the neutral point X3 is in the innermost layer f72. The specific winding connection of branch U3 is as follows: f65→e1→f9→e17→f28→e36→f47→e55→d63→c71→d9→c17→d28→c36→d47→c55→b64→a72→b9→a17→b28→a36→b47→a55→a64→b56→a46→b38→a27→b19→a8→b72→c63→d55→c46→d38→c27→d19→c8→d72→e62→f54→e46→f38→e27→f19→e8→f72.

[0056] The V-phase winding is formed by moving the U-phase winding 6 slots in the direction of motor rotation, and the W-phase winding is formed by moving the V-phase winding 6 slots in the direction of motor rotation.

[0057] In practical applications, the three-phase windings of the motor can be the U, V, and W windings of Embodiment 2, the U, V, and W windings of Embodiment 3, a combination of any two phase windings of Embodiment 2 and the remaining one phase winding of Embodiment 3, or a combination of any one phase winding of Embodiment 2 and the remaining two phase windings of Embodiment 3. The latter two combination schemes can concentrate the output terminals and neutral point of the three-phase windings, reduce the space size of the busbar, and save motor costs.

[0058] Example 4

[0059] The specific steps of the flat wire short-pitch winding method in this embodiment are as follows:

[0060] S1: The stator core is manufactured according to the specification that the number of stator slots and rotor poles meet the requirement of 3 slots per pole per phase, ensuring that the size of the stator slots matches the cross-section of the flat wires, and the installation space for 2n layers of flat wires is preset in the stator slots;

[0061] S2: Select hairpin flat wire of appropriate specifications, divide it into n slot layer groups in the manner of two adjacent layers as a group, arrange the two layers of flat wire in the same slot layer group to correspond to 3 slots and stagger them by one slot to ensure short distance effect.

[0062] S3: Assign slots for three parallel branches according to the definitions of left slot, middle slot and right slot, and wind the crown end of each branch according to the first preset span combination (including at least three different spans) to ensure span accuracy.

[0063] S4: Connect the welding ends of each branch in the manner of left slot-left slot, middle slot-middle slot, and right slot-right slot. Use special tooling to ensure that the span of the welding ends is a uniform and fixed second preset span. The number of the three types of connections is 8n / 3. Use appropriate welding technology to ensure the reliability of the connection.

[0064] S5: Complete the three-phase winding: The V-phase winding is obtained by moving the U-phase winding by a preset number of slots along the motor rotation direction, and the W-phase winding is obtained by moving the V-phase winding by a preset number of slots along the motor rotation direction; or, the V-phase winding is obtained by moving the U-phase winding by a preset number of slots along the motor rotation direction, and the W-phase winding is obtained by moving the V-phase winding by a preset number of slots along the motor rotation direction, with the torsion direction of the cross conductors in the same layer opposite to the torsion direction of the cross conductors in the same layer of the V-phase winding; or, the V-phase winding is obtained by moving the U-phase winding by a preset number of slots along the motor rotation direction. The W-phase winding is obtained by moving the preset number of slots, with the torsion direction of the cross conductor in the same layer opposite to the torsion direction of the cross conductor in the same layer of the U-phase winding. The W-phase winding is obtained by moving the U-phase winding along the motor rotation direction by twice the preset number of slots. Alternatively, the V-phase winding is obtained by moving the U-phase winding along the motor rotation direction by the preset number of slots, with the torsion direction of the cross conductor in the same layer opposite to the torsion direction of the cross conductor in the same layer of the U-phase winding. The W-phase winding is obtained by moving the V-phase winding along the motor rotation direction by the preset number of slots. The preset number of slots matches the number of slots per pole per phase.

[0065] S6: Perform insulation treatment and withstand voltage test on the completed winding to ensure that the electrical performance meets the design requirements.

[0066] Example 5

[0067] This embodiment also provides a motor, including a stator, a rotor, and the aforementioned flat wire short-pitch windings. The flat wire short-pitch windings are embedded in the stator slots, and the stator and rotor are arranged coaxially. The rotor adopts a permanent magnet structure or an electrically excited structure, which works in conjunction with the stator windings to achieve electromagnetic energy conversion, making it suitable for scenarios such as new energy vehicle drives and industrial drives.

Claims

1. A 72-slot, 8-pole, 3-parallel-branch flat wire short-pitch winding, characterized in that, It includes three-phase windings of U, V, and W. The number of stator slots and rotor poles of the motor meet the requirement that there are 3 slots per pole per phase and 3 parallel branches per phase winding. There are 2n layers of flat wire in a single stator slot. Two adjacent layers of flat wire form a slot layer group. The two layers of flat wire in the same slot layer group correspond to 3 slots and are staggered by one slot. Different slot layer groups occupy the same slot position. Each pole and each layer has 3 slots corresponding to 3 parallel branches, defined as left slot, middle slot and right slot. The flat wire conductor in each slot layer group is connected across two layers. The crown end span of the 3 parallel branches is a first preset span combination containing at least three different spans. The welding end span is a second preset span. The welding ends adopt the corresponding connection method of left slot to left slot, middle slot to middle slot, and right slot to right slot, forming a total of 8n welding connections. The number of connections corresponding to the three types of slots is 8n / 3.

2. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 1, characterized in that, The motor has 72 stator slots and 8 rotor poles.

3. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 1, characterized in that, The first preset span combination is a combination of at least three of the following: 8, 9, 10, 11, and 12, and the second preset span is 8.

4. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 3, characterized in that, Of the three parallel branches, one branch has a crown end span of 8, 10, 11, and 12, while the other two branches have crown end spans of 8, 9, 10, and 11.

5. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 1, characterized in that, Each parallel branch has a single-layer cross conductor. The span of the single-layer cross conductor is the same and it is located in the innermost or outermost layer. The torsion direction of the single-layer cross conductor is the direction of motor rotation or the opposite direction of motor rotation.

6. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 1, characterized in that, The V-phase winding is obtained by moving the U-phase winding by a predetermined number of slots along the motor rotation direction, and the W-phase winding is obtained by moving the V-phase winding by a predetermined number of slots along the motor rotation direction; or, the V-phase winding is obtained by moving the U-phase winding by a predetermined number of slots along the motor rotation direction, and the W-phase winding is obtained by moving the V-phase winding by a predetermined number of slots along the motor rotation direction, with the torsion direction of the cross conductor in the same layer opposite to the torsion direction of the cross conductor in the same layer of the V-phase winding; or, the V-phase winding is obtained by moving the U-phase winding by a predetermined number of slots along the motor rotation direction, with the torsion direction of the cross conductor in the same layer opposite to the torsion direction of the cross conductor in the same layer of the U-phase winding, and the W-phase winding is obtained by moving the U-phase winding by twice the predetermined number of slots along the motor rotation direction. Alternatively, the V-phase winding is obtained by moving the U-phase winding by a preset number of slots along the direction of motor rotation, and the torsion direction of the cross conductor in the same layer is opposite to the torsion direction of the cross conductor in the same layer of the U-phase winding. The W-phase winding is obtained by moving the V-phase winding by a preset number of slots along the direction of motor rotation.

7. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 6, characterized in that, The preset number of slots is matched with the number of slots per pole per phase, and the preset number of slots is 6.

8. The 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding according to claim 1, characterized in that, The outgoing terminals and neutral points of each parallel branch are located on the innermost or outermost flat wire.

9. An electric motor, characterized in that, It includes a stator, a rotor, and a 72-slot, 8-pole, 3-parallel flat wire short-pitch winding as described in any one of claims 1-8, wherein the flat wire short-pitch winding is embedded in the stator slots and cooperates with the rotor.

10. A method for winding a flat wire short-pitch winding, used to prepare the 72-slot, 8-pole, 3-parallel branch flat wire short-pitch winding as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: The stator core is manufactured according to the specification that the number of stator slots and rotor poles meet the requirement of 3 slots per pole per phase, and the installation space for 2n layers of flat wires is preset in the stator slots; S2: Divide the flat conductor into n slot layers in a way that two adjacent layers are grouped together. The two layers of flat conductor in the same slot layer group correspond to 3 slots and are staggered by one slot. S3: Assign slots for three parallel branches according to the definitions of left slot, middle slot and right slot, and wind the crown end of each branch according to the first preset span combination, so that the crown end span of the three branches includes at least three different spans. S4: Connect the welding ends of each branch in the manner of left slot-left slot, middle slot-middle slot, and right slot-right slot, ensuring that the span of the welding ends is the second preset span and that the number of the three types of connections is 8n / 3. S5: Complete the three-phase winding.

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