Double-layer short-pitch flat wire stator and motor

Abstract

The application relates to a double-layer short-distance flat wire stator and motor, which comprises a stator core and a flat wire winding. A plurality of stator slots are formed in the stator core, and the layers of coils in the stator slots are sequentially the first, second, third, fourth, fifth, sixth, seventh and eighth layers from the slot bottom to the slot opening. The flat wire winding comprises three-phase windings. The three-phase windings are divided into three groups of parallel winding lines, each phase winding has three parallel branches, and each branch comprises a plurality of coils arranged in the stator slots and connected in series with each other. The coils are sequentially connected by a plurality of PIN lines. The fifth, sixth, seventh and eighth layers of PIN lines of each pole and each phase are rotated by one slot position clockwise or counterclockwise, so that the windings form a double-layer short-distance structure, and the slot number q of each pole and each phase is z / 2mp. The structure of the application not only balances the parallel branches in space and potential, but also adapts to more power and torque requirements, so that the design of the driving motor is more flexible.

Description

Technical Field

[0001] This invention relates to the field of motor technology, specifically to a flat wire stator structure for motors, and more particularly to a flat wire winding stator with a double-layer short-pitch arrangement and its application in motors. Background Technology

[0002] With the increasing demands for motor power density, efficiency, and reliability in fields such as new energy vehicles and industrial drives, flat wire winding stator technology has become one of the mainstream technologies for high-performance motors due to its advantages such as high slot fill factor, good heat dissipation, and short end dimensions. Flat wire windings, by embedding rectangular conductors with larger cross-sectional areas into the stator slots, can effectively improve the power and torque density of motors and enhance thermal management performance compared to traditional round wire windings.

[0003] In winding design, double-layer short-pitch windings are a widely used and mature technology. By making the coil pitch smaller than the pole pitch (i.e., short pitch), it can significantly reduce the high-order harmonic content in the air gap magnetic field, reduce additional losses and torque ripple, improve the vibration and noise performance of the motor during operation, and increase efficiency. For motors with a certain pole-slot configuration, how to design the winding connection method and conductor arrangement is the key to achieving optimal electromagnetic performance, process feasibility, and cost control.

[0004] However, existing technologies face a series of challenges when applying double-layer short-pitch windings to flat wire stators with multiple pole pairs and high slot counts:

[0005] Parallel branch balance issues: To meet the demand for high current capacity, winding designs with multiple branches connected in parallel are often adopted. Currently, the number of parallel branches in a 12-pole 72-slot flat wire stator is mostly 1, 2, or 4. However, with the differentiation of motor power requirements and voltage and current boundaries, the torque and power corresponding to 2 or 4 branches vary too much, making it difficult to match the increasingly diverse market demands. The design challenge lies in how to construct multiple parallel branches that are completely symmetrical in space and potential, ensuring that the induced electromotive force of each branch is equal in magnitude and phase, avoiding additional losses caused by circulating current, and adapting to more power and torque requirements.

[0006] End-connection complexity and manufacturability: Flat wire windings require end connections through twisting, welding, and other methods. In double-layer, short-pitch, multi-branch structures, the PIN wires (i.e., single flat copper conductors) have various span types and complex end routing. This can easily lead to spatial interference between the ends of different layers and phases, increasing the difficulty of twisting and welding processes, and affecting production efficiency and product consistency. In particular, the ends of the innermost layer conductors, if not handled properly, may encroach on the internal space of the motor, affecting rotor assembly or cooling airflow.

[0007] Harmonic optimization and performance balance: While simple short-pitch designs can suppress harmonics, they may come at the cost of sacrificing some of the fundamental winding coefficient. Careful design of the span combinations of conductors in different slot layers (e.g., a mix of full-pitch, long-pitch, and short-pitch PIN wires) is required to suppress specific harmonics (e.g., 5th, 7th) while maintaining a high fundamental coefficient, and to achieve a reasonable spatial layout at the ends of various span conductors.

[0008] Structural reliability and insulation risks: The complex three-dimensional spatial interlacing of the ends places higher demands on the mechanical strength of the conductor's insulation layer. Improper end forming may lead to insulation damage or fretting wear during long-term operation, resulting in reliability risks. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the first objective of this invention is to provide a winding structure for a multi-pole log flat wire stator. This structure can not only achieve spatial and potential balance of parallel branches, but also adapt to more power and torque requirements, making the design of the drive motor more flexible. The second objective of this invention is to provide a motor.

[0010] To achieve the first objective of the invention, the present invention adopts the following technical solution:

[0011] A double-layer short-pitch flat wire stator includes a stator core and flat wire windings. The stator core has multiple stator slots, and the number of coil layers in each slot, from the bottom to the top, is layer 1, 2, 3, 4, 5, 6, 7, and 8. The flat wire windings include three-phase windings. Each three-phase winding is divided into three sets of parallel winding lines, each set consisting of three parallel branches. Each branch includes multiple coils arranged in the stator slots and connected in series. Each coil is formed by multiple pin wires connected sequentially. The 5th, 6th, 7th, and 8th pin wires of each pole and phase rotate clockwise or counterclockwise by one slot position, forming a double-layer short-pitch structure. The number of slots per pole and phase is q = z / 2mp, where z represents the total number of stator slots, m represents the number of phases of the motor, and p represents the number of pole pairs of the motor.

[0012] As a preferred embodiment: the number of stator slots z is 72, the number of phases m of the motor is 3, the number of pole pairs p of the motor is 6, and the number of slots per pole per phase q=2.

[0013] As a preferred embodiment, the winding is based on a 72-slot, 12-pole, 8-layer PIN wire to form a 3Y winding structure with spatial and potential balance characteristics.

[0014] As a preferred embodiment: the three-phase winding includes multiple coils, which are evenly distributed around the stator core. The coils are wound in the stator slots of the stator core. Each coil includes a U-shaped end and a welded end, which are located at the two ends of the stator core, respectively. The welded ends of the lead-in and lead-out wires are located on the welded side of the stator core.

[0015] As a preferred embodiment: each phase of the three-phase winding of the flat wire winding includes a first branch, a second branch and a third branch. The first branch, the second branch and the third branch are all composed of a full-pitch PIN line spanning 6 slot pitches, a first long-pitch PIN line spanning 18 slot pitches, a second long-pitch PIN line spanning 7 slot pitches and a short-pitch PIN line spanning 5 slot pitches connected together.

[0016] As a preferred option: among the PIN lines arranged radially from the outside to the center of the stator core, the second long-pitch PIN lines are used for PIN lines spanning 1-1 layers, the full-pitch PIN lines are used for PIN lines spanning 2-3 layers, the short-pitch PIN lines are used for PIN lines spanning 4-5 layers, the full-pitch PIN lines are used for PIN lines spanning 6-7 layers, and the first long-pitch PIN lines are used for PIN lines spanning 8-8 layers.

[0017] As a preferred embodiment: the PIN wire spanning 8-8 layers is a PIN wire of the same layer arranged on the innermost side of the stator slot, and all of them are formed radially outward, making them larger than the inner diameter of the stator core.

[0018] As a preferred embodiment: the full-pitch PIN wire, the first long-pitch PIN wire, the second long-pitch PIN wire, and the short-pitch PIN wire have the same structure, each including a first welding end, a first twist section, a first straight section, a U-shaped end, a second straight section, a second twist section, and a second welding end. The U-shaped end includes a first oblique section, a cross-layer section, and a second oblique section connected in sequence. The first straight section and the second straight section are respectively inserted into the corresponding stator slot layers, and one end is connected to the first oblique section, the cross-layer section, and the second oblique section. The U-shaped end is located in the stator core. One end face is a U-shaped side. The first twisting section connects the first welding end and the other end of the first straight section. The second twisting section connects the second welding end and the other end of the second straight section. The first welding end, the first twisting section, the second twisting section, and the second welding end are located on the other end face of the stator core, which is the welding side. The first twisting section and the second twisting section twist after the PIN wire is inserted into the stator slot of the stator core. After twisting, each PIN wire is welded together through the corresponding first welding end or second welding end.

[0019] As a preferred embodiment: in the first long-pitch PIN line and the second long-pitch PIN line, the first twisting segment and the second twisting segment twist in the same direction; in the full-pitch PIN line and the short-pitch PIN line, the first twisting segment and the second twisting segment twist in opposite directions, twisting away from the center to both sides respectively.

[0020] To achieve the second objective of the invention, the present invention adopts the following technical solution:

[0021] An electric motor employing any of the flat wire stators described above.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. Under the same slot polarity and the same voltage, the output power of a three-branch circuit will be higher than that of a two-branch circuit.

[0024] 2. Under specific operating conditions, it can reduce conductor losses, improve efficiency and heat dissipation performance. Especially in the medium and high speed range, the reduction of copper loss improves the efficiency of the motor. The increase in current path: 1) The current distributed at the solder joints is reduced, which reduces the current load and thermal stress of the solder joints; 2) The peak temperature is reduced, which improves the continuous operation capability and reliability of the motor.

[0025] 3. Compared with two-branch systems, three-branch systems increase the number of branches. The back EMF voltage of each branch remains unchanged, but the inductance of each branch will decrease, thus optimizing high-speed performance and expanding the constant power operating range.

[0026] 4. Compared with the traditional motor winding structure, the winding line structure of the present invention is simple and has fewer components, which reduces the manufacturing cost of the motor. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute a limitation thereof.

[0028] Figure 1 This is a schematic diagram of the overall structure of the flat wire stator of the present invention;

[0029] Figure 2 This is a schematic diagram of the end face structure of the stator core of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of the stator core welding end of the present invention;

[0031] Figure 4 This is a schematic diagram of the structure of the U-end of the stator core of the present invention;

[0032] Figure 5 This is a side view of the stator core after a PIN wire has been inserted, according to the present invention.

[0033] Figure 6 This is a schematic diagram of the PIN wire of the same-direction twisting head of the present invention;

[0034] Figure 7 This is a schematic diagram of the PIN wire structure of the reverse-direction twisting head of the present invention;

[0035] Figure 8 This is the wiring diagram of the flat wire stator of the present invention;

[0036] Figure 9 This is the three-phase color distribution diagram within the double-layer short-pitch groove of the present invention;

[0037] Figure 10 This is a comparison chart of the torque and power performance of flat wire stators with 2-branch Y-connection and 3-branch Y-connection.

[0038] Figure 11 It is a MAP diagram of the efficiency of a flat wire stator with two-branch Y-connection;

[0039] Figure 12 This is a MAP diagram showing the efficiency of the flat wire stator with a 3-branch Y-connection according to the present invention. Detailed Implementation

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] Furthermore, in the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more, unless explicitly defined otherwise.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0047] like Figures 1 to 12 As shown, a double-layer short-pitch flat wire stator includes a stator core 1 and a flat wire winding 2. The stator core 1 has multiple stator slots 11, and the number of coil layers in the stator slots 11, from the bottom to the top, are the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, and 8th layers, respectively. The flat wire winding 2 includes a three-phase winding. The three-phase winding is divided into three sets of parallel winding lines. Each set of phase windings consists of three parallel branches, and each branch includes multiple coils arranged in the stator slots and connected in series. The coils are formed by multiple pin wires connected in sequence. The 5th, 6th, 7th, and 8th layers of pin wires in each pole and each phase are rotated clockwise or counterclockwise by one slot position to form a double-layer short-pitch structure. The number of slots per pole and each phase is q = z / 2mp, where z represents the total number of stator slots, m represents the number of phases of the motor, and p represents the number of pole pairs of the motor.

[0048] The aforementioned structure employs three sets of parallel windings, each with three branches (3Y). This specific parallel connection method is a key technical means to achieve high power and high current capabilities, providing the premise and design goal for achieving absolute potential and spatial balance in a complex 72-slot 12-pole structure. Furthermore, the "rotation of the PIN wires in layers 5-8 by one slot" is the core technical means to achieve "double-layer short-pitch." Traditional double-layer windings align the upper and lower layers; this invention cleverly alters the effective pitch of the coil by shifting the upper layer (layers 5-8) conductors as a whole, thereby achieving a short-pitch effect. This interlayer misalignment design is the physical basis for achieving excellent electromagnetic performance, and its regularity also makes automated production possible. The combination of "double-layer short-pitch" and "flat wire" establishes the basic architecture for high power density (flat wire high slot fill factor) and excellent electromagnetic performance (short-pitch reduces harmonics, losses, and noise).

[0049] In this embodiment, the number of stator slots z is 72, the number of phases m of the motor is 3, the number of pole pairs p of the motor is 6, and the number of slots per pole per phase q=2. The winding forms a 3Y winding structure with spatial and potential balance characteristics based on 72 slots, 12 poles, and 8 layers of PIN wire. 72 slots and 12 poles (q=2) is a typical configuration for multi-pole motors and also a challenge in the parallel branch balance design. The above structure clearly solves the parallel branch circulating current problem mentioned in the background art, ensures complete symmetry of the three-phase induced electromotive force, fundamentally eliminates the additional copper loss and heat generation caused by imbalance, and improves motor efficiency and reliability.

[0050] The three-phase winding includes multiple coils that are evenly distributed around the stator core. The coils are wound in the stator slots 11 of the stator core 1. Each coil includes a U-shaped end 24 and a welded end, with the U-shaped end 24 and the welded end located at both ends of the stator core 1, respectively. The welded ends of the lead-in and lead-out wires are located on the welded side 12 of the stator core 1.

[0051] The above structure clearly defines the physical separation of the "U-shaped side" and the "welding side," optimizing the production process and end-point management. The U-shaped end completes the span connection, while the welding end completes the electrical connection within the parallel branches and between phases. This partitioning makes the manufacturing processes (wire insertion, twisting, welding) clear and orderly; and by concentrating all welding points on one side, it is convenient to carry out centralized insulation treatment (such as coating or adding an insulating cover) and heat dissipation design in that area, improving process reliability and maintenance convenience.

[0052] Each phase of the three-phase winding of the flat wire winding includes a first branch, a second branch, and a third branch. The first branch, the second branch, and the third branch are all composed of a full-pitch PIN line spanning 6 slot pitches, a first long-pitch PIN line spanning 18 slot pitches, a second long-pitch PIN line spanning 7 slot pitches, and a short-pitch PIN line spanning 5 slot pitches.

[0053] Among the PIN lines arranged radially from the outside to the center along the stator core 1, the second long-pitch PIN lines are used for the PIN lines spanning layers 1-1, the full-pitch PIN lines are used for the PIN lines spanning layers 2-3, the short-pitch PIN lines are used for the PIN lines spanning layers 4-5, the full-pitch PIN lines are used for the PIN lines spanning layers 6-7, and the first long-pitch PIN lines are used for the PIN lines spanning layers 8-8.

[0054] The above structure employs a combination of "full pitch (6) + short pitch (5) + two types of long pitch (7, 18)," representing a targeted electromagnetic optimization design. The short pitch (5) effectively suppresses major low-order harmonics such as the 5th and 7th; specific long pitches (7) may be used to compensate for the fundamental frequency coefficient or adjust the magnetic field distribution; and ultra-long pitches (18) are typically used to achieve specific parallel branch connections. This combination aims to comprehensively optimize the winding coefficients, achieving the best balance between suppressing harmonics and maintaining a high fundamental frequency potential.

[0055] The above structure also fixes different span types at different radial positions, making the three-dimensional shape of the end highly regular and predictable, greatly reducing the risk of spatial interference between different PIN wires at the end, and providing a geometric basis for automated wire insertion and end forming.

[0056] The 8-8 layer PIN wires are the innermost PIN wires in the same layer arranged in the stator slot 11, and all of them are formed radially outward to make them larger than the inner diameter of the stator core 1. The end of the innermost PIN wire (8th layer) is formed outward to ensure that it does not intrude into the rotor space. This is a key structural feature to prevent stator-rotor scraping and ensure reliable motor assembly and safe operation. It directly solves the hidden danger of flat wire ends potentially encroaching on internal space in the prior art.

[0057] The full-pitch PIN wire, the first long-pitch PIN wire, the second long-pitch PIN wire, and the short-pitch PIN wire have the same structure, each including a first welding end 21, a first twist section 22, a first straight section 23, a U-shaped end 24, a second straight section 25, a second twist section 26, and a second welding end 27. The U-shaped end 24 includes a first oblique section 241, a cross-layer section 242, and a second oblique section 243 connected in sequence. The first straight section 23 and the second straight section 25 are respectively inserted into the corresponding slot layers of the stator slot 11, and one end is connected to the first oblique section 241, the cross-layer section 242, and the second oblique section 243. The U-shaped end 24 is located in the stator core 1. One end face, which is the U-shaped side 12, is connected to the other end of the first welding end 21 and the first straight section 23. The second twisting section 26 is connected to the other end of the second welding end 27 and the second straight section 25. The first welding end 21, the first twisting section 22, the second twisting section 26, and the second welding end 27 are located on the other end face of the stator core 1, which is the welding side 13. The first twisting section 22 and the second twisting section 26 twist after the PIN wire is inserted into the stator slot 11 of the stator core 1. After twisting, each PIN wire is welded to the corresponding first welding end 21 or second welding end 27.

[0058] The aforementioned PIN wire structure is a highly standardized and modular component. The uniform U-shaped end and straight section design facilitates mass production with precision. The "insertion, twisting, and then soldering" process is a mature and reliable technology for flat wire windings, ensuring connection quality and consistency.

[0059] In the first and second long-pitch PIN lines, the first twist segment 22 and the second twist segment 26 twist in the same direction. In the full-pitch and short-pitch PIN lines, the first twist segment 22 and the second twist segment 26 twist in opposite directions, twisting away from the center to both sides. Specifying different twist directions according to the PIN line span type is a key process design. This aims to ensure that the solder ends (twisted segments) of PIN lines with different spans are arranged in an orderly and layered manner on the soldering side, avoiding solder joint accumulation and mutual interference, ensuring soldering quality, and making the ends compact and neat overall, which is beneficial for reducing axial dimensions and enhancing insulation protection.

[0060] An electric motor employs the flat wire stator described in any of the preceding claims. The motor using the stator of this invention inherits and comprehensively embodies all the aforementioned technical effects, including: high power density, high efficiency (thanks to balanced windings and low harmonics), low vibration and noise, high reliability, and good manufacturability. The performance of this motor compared to that of a traditional 2Y winding motor is as follows: Figures 10 to 12 As shown.

[0061] This invention systematically solves core problems such as parallel branch balance, harmonic optimization, complex end-processing, and spatial conflicts in multi-pole logarithmic flat wire motors through a series of collaborative innovations from overall architecture (3Y balance), pole-slot matching (72 slots, 12 poles), electromagnetic design (hybrid span and short pitch), to physical structure (end partitioning, radial layout, and torsion direction). Ultimately, it realizes a high-performance, easy-to-manufacture, and highly reliable flat wire stator and motor.

[0062] In summary, this invention effectively reduces harmonics, optimizes the NVH performance of the motor, and achieves a balance between space and potential. The stator of this invention adopts a wave winding configuration, with the innermost and outermost sides interconnected via same-layer return pin lines. Furthermore, the lead-in and lead-out lines can be arranged on either the innermost or outermost two layers of pin lines, achieving advantages such as simple winding end connections, small space occupation, and a compact busbar connection structure.

[0063] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A double-layer short-pitch flat wire stator, comprising a stator core (1) and a flat wire winding (2); the stator core (1) has a plurality of stator slots (11), wherein the number of layers of coils in the stator slots (11) from the bottom of the slot to the top of the slot is the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, and 8th layers respectively; the flat wire winding (2) comprises a three-phase winding; the three-phase winding is divided into three sets of parallel winding lines, characterized in that: Each phase winding consists of three parallel branches, each branch including multiple coils arranged in stator slots and connected in series. The coils are formed by multiple pin wires connected in sequence. The 5th, 6th, 7th, and 8th layers of pin wires in each pole and each phase are rotated clockwise or counterclockwise by one slot position, so that the windings form a double-layer short-pitch structure. The number of slots per pole and each phase is q=z / 2mp, where z represents the total number of stator slots, m represents the number of phases of the motor, and p represents the number of pole pairs of the motor.

2. The double-layer short-pitch flat wire stator according to claim 1, characterized in that: The number of stator slots z is 72, the number of phases m of the motor is 3, the number of pole pairs p of the motor is 6, and the number of slots per pole per phase q = 2.

3. A double-layer short-pitch flat wire stator according to claim 2, characterized in that: The winding is based on 72 slots, 12 poles, and 8 layers of PIN wire, forming a 3Y winding structure with spatial and potential balance characteristics.

4. A double-layer short-pitch flat wire stator according to claim 1, characterized in that: The three-phase winding includes multiple coils, which are evenly distributed around the stator core. The coils are wound in the stator slots (11) of the stator core (1). Each coil includes a U-shaped end (24) and a welded end, and the U-shaped end (24) and the welded end are located at the two ends of the stator core (1), respectively. The welded ends of the lead-in and lead-out wires are located on the welded side (12) of the stator core (1).

5. A double-layer short-pitch flat wire stator according to claim 1, characterized in that: Each phase of the three-phase winding of the flat wire winding includes a first branch, a second branch, and a third branch. The first branch, the second branch, and the third branch are all composed of a full-pitch PIN line spanning 6 slot pitches, a first long-pitch PIN line spanning 18 slot pitches, a second long-pitch PIN line spanning 7 slot pitches, and a short-pitch PIN line spanning 5 slot pitches.

6. A double-layer short-pitch flat wire stator according to claim 5, characterized in that: Among the PIN lines arranged radially from the outside to the center along the stator core (1), the second long-pitch PIN line is used for the PIN lines spanning the 1st to 1st layers, the full-pitch PIN line is used for the PIN lines spanning the 2nd to 3rd layers, the short-pitch PIN line is used for the PIN lines spanning the 4th to 5th layers, the full-pitch PIN line is used for the PIN lines spanning the 6th to 7th layers, and the first long-pitch PIN line is used for the PIN lines spanning the 8th to 8th layers.

7. The flat wire stator according to claim 6, characterized in that: The 8-8 layer PIN wires are PIN wires arranged on the innermost side of the stator slot (11) and are all formed radially outward to make them larger than the inner diameter of the stator core (1).

8. A double-layer short-pitch flat wire stator according to claim 5, characterized in that: The full-pitch PIN wire, the first long-pitch PIN wire, the second long-pitch PIN wire, and the short-pitch PIN wire have the same structure, each including a first welding end (21), a first twist section (22), a first straight section (23), a U-shaped end (24), a second straight section (25), a second twist section (26), and a second welding end (27). The U-shaped end (24) includes a first oblique section (241), a cross-layer section (242), and a second oblique section (243) connected in sequence. The first straight section (23) and the second straight section (25) are respectively inserted into the corresponding stator slots (11), and one end is connected to the first oblique section (241), the cross-layer section (242), and the second oblique section (243). The U-shaped end (24) is located in the stator core (1). One end face side, this end face side is a U-shaped side (12), the first twisting section (22) connects the first welding end (21) and the other end of the first straight section (23), the second twisting section (26) connects the second welding end (27) and the other end of the second straight section (25), the first welding end (21), the first twisting section (22), the second twisting section (26) and the second welding end (27) are located on the other end face side of the stator core (1), this end face is a welding side (13); the first twisting section (22) and the second twisting section (26) twist after the PIN wire is inserted into the stator slot (11) of the stator core (1), and each PIN wire is welded and connected through the corresponding first welding end (21) or second welding end (27) after twisting.

9. A double-layer short-pitch flat wire stator according to claim 5, characterized in that: In the first long-pitch PIN line and the second long-pitch PIN line, the first twisting segment (22) and the second twisting segment (26) twist in the same direction. In the full-pitch PIN line and the short-pitch PIN line, the first twisting segment (22) and the second twisting segment (26) twist in opposite directions, twisting away from the center on both sides respectively.

10. An electric motor, characterized in that: The flat wire stator according to any one of claims 1-9 is adopted.

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