A slotted flat wire winding based on layered suppression and mixed section and a design method thereof

Abstract

The application discloses a slotted flat wire winding based on layered suppression and mixed section and a design method, and relates to the technical field of electric vehicle drive motors. The stator slot is divided into three loss areas of high eddy current, medium eddy current and high direct current along the radial direction, the collaborative design of partition customization mixed section and magnetic field matching differential slotting is adopted, the different regions of the conductor are subjected to differential segmentation and section optimization, and the slot fill factor is kept through global copper area balance. The application can effectively suppress the skin effect and the proximity effect, significantly reduce the alternating current loss under high-frequency working conditions, balance the high-frequency eddy current loss and the high-torque direct current loss, and is simple in process, controllable in cost, suitable for super-high-speed flat wire motors driven by SiC inverters, and has high power density and operation reliability.

Description

Technical Field

[0001] This invention belongs to the field of electric vehicle drive motor technology, specifically relating to a slotted flat wire winding structure based on layered suppression and hybrid cross section, which is particularly suitable for flat wire stator windings and their AC loss suppression and system optimization in SiC inverter drive, high frequency high voltage, and ultra-high speed conditions. Background Technology

[0002] This application relates to the field of flat wire motor drive systems for electric vehicles, and particularly to the suppression of AC losses and system optimization of flat wire motors.

[0003] Flat-wire motors are a core component of electric vehicle drive systems and have replaced traditional round-wire motors as the mainstream, with a market penetration rate expected to reach 67% by 2025. They offer significant advantages in slot fill factor, power density, and heat dissipation. However, as electric drive systems evolve towards higher frequencies and higher voltages, the skin effect and proximity effect of flat-wire motor windings lead to a dramatic increase in AC losses (AC copper losses can be more than twice that of DC copper losses under high-frequency conditions). This reduces motor efficiency, affects range, and easily causes localized overheating, threatening insulation and operational reliability. Especially under SiC inverter drive, high switching frequencies exacerbate current harmonics and pulse overvoltage problems, making AC losses and insulation stress even more pronounced.

[0004] To address the AC loss problem in flat-wire motors, existing technologies are mainly optimized in three directions: conductor structure optimization and parameter adjustment: balancing losses and performance through unequal cross-section conductors, conductor subdivision (such as Litz wire), and size / parallel branch number adjustment; winding topology and transposition technology: adopting 8-layer windings (lower losses in high-speed areas), new inter-layer transposition, hybrid transposition windings (HTHW), and winding position optimization; and manufacturing process and material innovation: utilizing 3D printing to manufacture complex windings and improving insulation materials to cope with electrothermal stress.

[0005] While existing technologies can reduce AC losses to some extent, they have significant limitations: insufficient adaptability to high-frequency operating conditions; as the drive frequency of SiC inverters increases, the effectiveness of existing conductor optimization schemes drops sharply; the skin effect becomes more pronounced with increasing frequency, and conductor subdivision (such as Litz wire) reduces slot fill factor due to the space occupied by thin wire insulation; in ultra-high-speed (above 12000 r / min) fields, even 8-layer windings face the problem of significantly increased losses, which existing technologies struggle to address; there is an imbalance between process complexity and cost-effectiveness, with high-performance solutions accompanied by high costs and process difficulties: 8-layer windings... Complex processes and low yield rates; HTHW winding manufacturing requires specialized equipment; 3D printed windings are still in the laboratory stage with low mass production efficiency; conductors with unequal cross-sections require customized raw materials, resulting in a complex supply chain; local overheating and insulation reliability issues make it difficult to balance losses and heat / insulation problems: local hot spots are easily formed in the slot area at high speeds and high frequencies, and the upper conductor loss is higher than the lower layer, resulting in a large temperature gradient; under high dv / dt conditions in SiC inverters, the interlayer voltage stress is uneven, and traditional transposition can easily lead to coil overvoltage; existing insulation designs do not fully consider multi-physics coupling, making them prone to aging or breakdown.

[0006] In related technologies, CN11586523B discloses an AC loss suppression structure combining Litz flat wire and interlayer transposition for flat-wire motors. This structure reduces AC losses caused by the skin effect and proximity effect by dividing a large-section flat wire into multiple strands of fine Litz wire and employing interlayer cross-transposition. However, while this solution can reduce winding losses at low and medium frequencies, the insulation layer between the fine Litz wire conductors occupies a significant amount of space within the slots, reducing the slot fill factor of the flat-wire motor by approximately 15%, thus weakening its core advantage of high power density. Simultaneously, during interlayer cross-transposition, the bending radius at the ends of the flat wire windings decreases, making the insulation layer more susceptible to damage and increasing the risk of short circuits. Furthermore, as the driving frequency increases to the kHz level, the high-frequency circulating current loss between the fine conductors increases significantly, resulting in a substantial decrease in the loss suppression effect.

[0007] In summary, the key to overcoming the technical bottleneck of excessive AC loss in flat wire motors under high-frequency and high-voltage conditions lies in developing an optimized scheme for efficiently suppressing AC losses without reducing the slot fill factor and power density of the flat wire motor, while also considering process feasibility and cost control. Summary of the Invention

[0008] This invention addresses the aforementioned industry pain points by proposing a slotted flat wire winding and its design method based on layered suppression and hybrid cross-section. Based on the radial gradient distribution of the leakage magnetic field within the slot, it precisely divides the stator slot into three loss regions: high eddy current, medium eddy current, and high DC. Employing a collaborative design of "regionally customized hybrid cross-section + magnetic field matching differentiated slotting," it precisely suppresses AC losses in different regions without compromising slot fill factor or power density. This completely resolves the contradiction between "high-frequency eddy current loss and high torque DC loss being mutually exclusive." Furthermore, the process is simple, cost-effective, and perfectly compatible with ultra-high-speed electric vehicle drive motors driven by SiC inverters.

[0009] The specific technical solution is as follows: A slotted flat wire winding based on layered suppression and mixed cross-section includes stator slots and multi-layer winding conductors placed therein; the multi-layer winding conductors are sequentially divided into a high eddy current loss region, a medium eddy current loss region, and a high DC loss region along the radial direction of the slot from the slot opening to the slot bottom; the conductors in the high eddy current loss region are divided radially, tangentially, or a combination of both to form multi-strand insulator conductors with parallel ends; the conductors in the medium eddy current loss region are divided tangentially to form multi-strand insulator conductors with parallel ends; the conductors in the high DC loss region are undivided solid conductors, and their radial height is greater than the radial height of the single-strand sub-conductors after division in the high eddy current loss region and the medium eddy current loss region; at least a portion of the conductor surfaces in the high eddy current loss region and the medium eddy current loss region are provided with axially extending slots.

[0010] A design method for slotted flat wire windings based on layered suppression and hybrid cross-section includes the following steps: The radial distribution of the armature reaction magnetic field and the leakage magnetic field of the permanent magnet in the stator slot was quantitatively analyzed to obtain the radial and tangential magnetic flux density distributions of each conductor layer. Based on the magnetic field intensity distribution gradient, the stator slots are divided radially from the slot opening to the slot bottom into a high eddy current loss region, a medium eddy current loss region, and a high DC loss region. For conductors in the high eddy current loss region, radial segmentation, tangential segmentation, or a combination of both are used to divide them into multiple mutually insulated sub-conductors, with each sub-conductor connected in parallel at its ends; The conductor in the eddy current loss region is tangentially split into multiple mutually insulated sub-conductors, and each sub-conductor is connected in parallel at the ends; For conductors in the high DC loss region, a solid, undivided structure is adopted, and their radial height is increased; Based on the principle of global copper area balance, the radial height of the conductors in the high eddy current loss region and the medium eddy current loss region is adjusted so that the total copper area of ​​the sub-slot remains basically unchanged. Based on the magnetic field intensity gradient of each region, differentiated axial through slots are processed on the conductor surface in the high eddy current loss region and the medium eddy current loss region. The higher the magnetic field intensity, the more slots are opened and the greater the slot depth.

[0011] To implement precise loss suppression, a deep understanding of the distinct electromagnetic environments of conductors at different positions within the slot is essential. The basic principles and design concepts of this invention are described below using a conventional synchronous motor stator winding structure as an example. Figure 1 As shown, in the conventional synchronous motor stator winding structure, each layer of winding is named L1~L10 along the radial direction.

[0012] I. Distribution law of armature reaction under the action of magnetic field alone Neglecting the influence of permanent magnets, only the armature leakage magnetic field generated by the rated armature current is considered. Analysis shows that the magnitude of the leakage magnetic field within the slot is closely related to the conductor's position within the slot; the leakage magnetic field is larger at the slot opening and in the middle of the slot, and decreases towards the bottom of the slot. The radial magnetic flux density is calculated by taking the center points of each conductor layer (e.g., L1 to L10). B x With tangential magnetic flux B y Tangential magnetic flux density was found B y Dominant, radial magnetic flux density B x The magnetic flux density amplitude gradually decreases from L1 to L10, and the armature leakage magnetic field is close to zero at L9 and L10. Therefore, in the bottom region of the slot, eddy current losses are minimal, and DC losses dominate.

[0013] II. Distribution Pattern of Leakage Magnetic Field under the Sole Effect of Permanent Magnet Neglecting armature current and considering only the leakage magnetic field generated by the permanent magnet, analysis shows that the leakage magnetic field is larger at the slot opening and smaller in the middle and bottom of the slot. Inside the slot... B y Almost zero at L1 and L2 B x Larger, and from L3 to L10, B x and B y All are very small. This indicates that the leakage magnetic field of the permanent magnet is concentrated only in the L1 and L2 layers near the slot opening, and is mainly radial magnetic field.

[0014] III. Magnetic Field Distribution Law of Winding Structure Combining the effects of the two magnetic fields mentioned above, the stator slots can be divided radially into three regions with different loss characteristics: Region 1 (L1-L2, slot area): Simultaneously affected by the strong tangential magnetic field of armature reaction and the strong radial magnetic field of permanent magnet, the eddy current loss is extremely high, which is the high eddy current loss region.

[0015] Region 2 (L3-L8, middle of the slot): mainly affected by the tangential magnetic field of armature reaction, but the magnetic flux density amplitude gradually decreases from L3 to L8, and the eddy current loss is moderate, which is the medium eddy current loss region.

[0016] Region 3 (L9-L10, bottom of the tank): Both magnetic fields have decayed to near zero, eddy current losses are negligible, and losses are mainly DC losses, making it a high DC loss region.

[0017] Based on the above electromagnetic field analysis, the stator slots are divided into three characteristic regions along the radial direction (e.g., Figure 2 (as shown) 1) Region 1 (High eddy current loss region, slotted region, e.g., L1-L2 layers): Closest to the air gap and permanent magnet, it is subjected to strong coupling between the armature reaction magnetic field (strong tangential) and the permanent magnet leakage magnetic field (strong radial). The radial magnetic flux density component of this region... B x (Primarily generated by permanent magnets) and tangential magnetic flux density component B y The amplitudes of the eddy currents (primarily generated by the armature current) all reach their peak values, and the powerful alternating magnetic field induces huge eddy currents in the conductor. The eddy current losses can be qualitatively described by an extended form of the Sullivan formula: (1.1) in, a The radial height of the conductor. b The tangential width of the conductor. This is the resistivity of the conductor. Because... B x and B y The eddy current losses are all very large, resulting in extremely significant total eddy current losses in this region. Located deep within the motor, this area suffers from poor heat dissipation, and the enormous eddy current losses easily lead to localized overheating and the formation of hot spots, posing a major threat to motor reliability.

[0018] 2) Region Two (Middle Eddy Current Loss Region, Middle of the Slot, e.g., L3-L8 layers): As the magnet penetrates deeper into the slot, the radial magnetic field generated by the permanent magnet increases. B x The leakage magnetic field in this region decays rapidly and is mainly generated by the tangential magnetic field of the armature current. B y Dominantly, the magnetic flux density amplitude gradually decreases from L3 to L8. Eddy current losses in this region primarily originate from… B y Its loss formula can be simplified to: (1.2) Although the loss of a single conductor is lower than in region one, the total eddy current loss contribution cannot be ignored due to the large number of conductors in this region. Therefore, for...B y Targeted suppression is key to optimizing this region.

[0019] 3) Region Three (High DC Loss Region, bottom of the slot, e.g., L9-L10 layers): This region is far from the slot opening and air gap. Both the armature magnetic field and the permanent magnet magnetic field have attenuated to almost zero, and the magnetic flux density is low. B x and B y Both are close to zero, so eddy current losses are negligible. Almost all losses originate from the Joule heat generated by the current flowing through the DC resistance of the conductor, i.e., DC losses. (1.3) in, This is the effective value of the phase current. It is a DC resistance. The resistivity of the conductor material, For the conductor length, S This refers to the cross-sectional area of ​​the conductor. Under high torque conditions, DC losses in this region become the primary concern. Increasing the conductor's cross-sectional area... S This is the most direct way to reduce DC losses.

[0020] Based on the above precise physical field analysis, this invention establishes the theoretical basis of the "layered loss suppression method": adopting completely different and optimized conductor design strategies for different regions based on their loss mechanisms.

[0021] IV. Optimization Strategies of the Invention Based on the above-mentioned layered theory, this invention proposes a hybrid cross-section flat wire winding structure, which "customizes" the conductors in different regions of the slot.

[0022] Conductor optimization strategies for Region 1 (high eddy current loss region): radial segmentation, or tangential segmentation, or a combination of radial and tangential segmentation; Region 1 is simultaneously subjected to a tangential magnetic field B y With radial magnetic field B x The strong current carrying capacity is achieved by replacing the original single conductor with multiple insulated sub-conductors through radial splitting, tangential splitting, or a combination of radial and tangential splitting. All sub-conductors are connected in parallel at the ends to maintain the total current carrying capacity.

[0023] Among them, radial segmentation (suppressing tangential magnetic field) B y (induced eddies) Radial splitting (in the direction of downward cutting) divides the conductor tangentially (in the width direction) into multiple parallel insulator conductors, thereby reducing the tangential dimension of a single sub-conductor.b Due to the tangential magnetic field B y The resulting eddy current loss and b It is proportional to the cube of the equation, and the eddy current loss is significantly reduced after segmentation. The structure is as follows: Figure 3 As shown.

[0024] Among them, tangential segmentation (suppressing radial magnetic field) B x (induced eddies) Tangential splitting (in the downward cutting direction) divides the conductor radially (height direction) into multiple parallel insulator conductors, thereby reducing the radial dimension of a single sub-conductor. a Due to the radial magnetic field B x The resulting eddy current loss and a It is proportional to the cube of the equation, and the eddy current loss is significantly reduced after segmentation. The structure is as follows: Figure 4 As shown.

[0025] Optional material replacement: To further enhance the eddy current suppression effect in region one, the conductor material can be replaced from copper with a material with higher resistivity (such as aluminum, whose resistivity is approximately 1.6 times that of copper). According to the eddy current loss formula... Increasing resistivity can directly reduce eddy current losses; however, DC losses... Replacing the material with a high resistivity material will increase DC losses. Therefore, this material replacement solution is only suitable for ultra-high-speed operating conditions where eddy current losses are absolutely dominant and DC losses account for a very small proportion.

[0026] Optimization strategy for conductor in Region 2 (medium eddy current loss region): Tangential segmentation The eddy current source in region two has a tangential magnetic field. B x Dominant, radial magnetic field B y The attenuation has become negligible. To address this characteristic, the most cost-effective tangential segmentation strategy is adopted: tangential segmentation, which divides the conductor radially (in the height direction) into multiple parallel insulator conductors, thereby reducing the radial dimension of a single sub-conductor. a Based on eddy current loss and a The cube is proportional to the number of times the number is divided. B x The resulting eddy current losses are significantly suppressed. This scheme, while ensuring eddy current suppression, has low process complexity and manageable cost increases, making it the optimal choice for Region 2.

[0027] Optimization strategy for conductors in Region 3 (high DC loss region): Do not split, increase the cross-sectional area, and adjust the radial dimensions of each conductor in Regions 1 and 2 while satisfying the global copper area balance principle (or slot fill factor).

[0028] The conductor at the bottom of the tank is in an extremely weak magnetic field environment, so AC losses (eddy current losses) are negligible, and DC losses dominate. DC losses It is inversely proportional to the conductor's cross-sectional area, therefore increasing the cross-sectional area is the most direct way to reduce DC losses.

[0029] This invention employs a strategy of significantly increasing the radial height of the conductors in region three (L9, L10), assuming the original design height is... a The height after the increase is ,and .

[0030] However, simply increasing the cross-sectional area of ​​the bottom conductor will increase the slot fill factor, potentially exceeding the space limitations within the slot. Therefore, this invention proposes a global copper area balancing principle: to maintain a relatively constant total copper area (i.e., slot fill factor) within the entire slot, while increasing the cross-sectional area of ​​the conductor in region three, the cross-sectional areas of the conductors in regions one and two are correspondingly reduced. Let the total number of layers be... n The adjusted conductor heights for regions one and two are: conductor width b If it remains unchanged, the total copper area balance formula is: , Introducing an increase factor ( ),make Substituting into the above equation, we can solve for:

[0031] Optimal coefficient optimization: coefficient A larger value is not necessarily better. Increasing... While this reduces DC losses in region three, it also introduces two negative effects: first, the cross-sectional area of ​​the conductors in regions one and two decreases accordingly, leading to increased AC resistance and AC losses; second, the DC losses of the end windings also increase due to the thinner conductors. Therefore, there exists an optimal solution that minimizes the total loss (the sum of AC and DC losses). This invention uses finite element analysis to optimize under different operating conditions (especially peak torque conditions), ultimately determining the value that minimizes total losses. .

[0032] After completing the above-mentioned hybrid cross-section winding design based on partitioned management (partitioned management means: designing differentiated segmentation methods according to the radial magnetic field strength gradient in the stator slot; the conductor layer with weak magnetic field adopts a complete equal cross-section structure without segmentation to ensure the maximum conductive area and reduce DC resistance; the conductor layer with medium magnetic field strength is tangentially divided into two equal-sized sub-conductors; the conductor layer with the strongest magnetic field strength adopts a combined radial and tangential segmentation method to divide into four equal-sized sub-conductors to maximize the reduction of skin effect), this invention further introduces a local optimization measure—slotting on the conductor surface—to cope with the eddy current effect at extremely high frequencies.

[0033] The slotting design follows these rules: no slots are made in areas with low magnetic field strength (such as high DC areas); the number and depth of slots increase sequentially from farthest to nearth of the rotor (i.e., from the bottom of the slot to the top of the slot); within the same conductor layer, the slots are deeper in the middle and shallower on both sides; at the same time, one slot is made on each side of the tangential side of each conductor layer, and the slot depth decreases sequentially from high to low magnetic field strength.

[0034] The following is the basis for the number and depth of layers and slots: (1.6) The above is the skin depth. Calculation formula For conductor resistivity, For operating frequency, ρ is the permeability. When the equivalent thickness of the conductor... Greater than skin depth At that time, the current is concentrated on the surface, causing the AC windings to... Much greater than DC resistance The relationship between the two is shown in the following formula: (1.7) For rectangular conductors, The following empirical formula exists: (1.8) Layered grooving reduces the equivalent thickness of the conductor. This reduces Ultimately reduced The closer to the rotor, the higher the radial magnetic field strength. The smaller the value, the more radial slots the conductor has, and the radial magnetic field strength on both sides of the same layer of conductor is lower than the magnetic field strength in the central region. For large areas, shallow trenches are sufficient, while deeper trenches are needed in the central region to reduce the effective thickness; in to In some cases, the tangential magnetic field has a significant impact on AC losses. To address the AC losses caused by tangential leakage magnetic field, deeper tangential slots than radial slots are used. At the same time, considering the limited radial thickness of the flat wire winding, single slots are opened on both sides of the conductor, with the slots becoming deeper closer to the rotor side.

[0035] Grooving disrupts the continuous path of eddy currents by altering the shape and spacing of the conductor. The following equation shows the eddy current loss in the conductor. With vortex path area Proportional to the magnetic reluctance of the eddy current path Inversely proportional to the size of the conductor, the layered slotting of this invention divides the large conductor into smaller conductors, reducing the eddy current path area, increasing the eddy current path reluctance, and suppressing proximity effect losses. Furthermore, the central symmetry of the slotting ensures uniform current distribution, avoids eddy current concentration, and also results in uniform conductor stress distribution, ensuring the stability and reliability of the winding.

[0036] (1.9) To reduce the reduction in the cross-sectional area of ​​the copper wire caused by slotting and to lower the processing difficulty, based on the characteristics of AC loss distribution, this invention has a large number of slots in the region closest to the rotor, and the number of slots gradually decreases in the region radially away from the rotor.

[0037] Beneficial effects 1. The present invention, through a layered suppression through-slot structure, can effectively segment the large eddy current path caused by the skin effect and proximity effect, decompose it into multiple independent small eddy currents, thereby significantly weakening the eddy current intensity and reducing eddy current loss. 2. By combining the through-slot structure with the hybrid cross-section winding, this invention can reduce the effective conductor size to suppress the skin effect, while optimizing the magnetic field distribution in the slot, weakening the additional eddy current loss generated by the high-order harmonic magnetic field, and significantly reducing AC loss under high-frequency operating conditions while ensuring the slot fill factor, thus solving the problem of incomplete AC loss suppression in the prior art. 3. The present invention adopts a hybrid cross-section winding design of "overall-local synergy". By implementing differentiated segmentation and cross-sectional area optimization of conductors in different regions of the slot, the contradiction between high-frequency eddy current loss and high torque DC loss of flat wire winding in high-speed, high-power-density permanent magnet synchronous motor is resolved. 4. Based on the principle of global copper area balance, this invention increases the conductor cross-sectional area in the high DC loss region to reduce DC resistance, while correspondingly reducing the conductor cross-sectional area in the high eddy current loss region and the medium eddy current loss region. This solves the problem of difficulty in balancing slot fill factor and conductivity in the prior art, and achieves a balance between loss control and high torque output capability. 5. This invention constructs a comprehensive three-dimensional technical system of "zonal governance and multi-physics field optimization", which is not a single improvement measure. It can accurately suppress the magnetic field characteristics and loss mechanism of each region in the tank under different working conditions, and is suitable for complex operating scenarios such as high speed, high frequency and high voltage. 6. By designing a layered and differentiated groove depth and number, this invention enables regions with higher magnetic field strength to obtain stronger eddy current suppression capabilities. Compared with existing single improvement schemes, it improves the loss control effect and operational stability of flat wire windings in multiple scenarios, and enhances the adaptability and reliability of the technical solution. Attached Figure Description

[0038] Figure 1 Conventional synchronous motor stator winding structure; Figure 2 Schematic diagram of leakage magnetic field distribution and stratification within the tank; Figure 3 This is a schematic diagram of the radial segmentation of the conductor in this invention; Figure 4 This is a schematic diagram of the conductor tangential segmentation of the present invention; Figure 5 It is the original flat wire winding structure; Figure 6 This is a schematic diagram of the axial cross-section of a single-slot winding in an embodiment of the present invention. Detailed Implementation

[0039] To address the problems of incomplete AC loss suppression, the contradiction between slot fill factor and conductivity, and large additional losses in existing technologies, this embodiment provides a slotted flat wire winding based on layered suppression and a hybrid cross-section. The through-slots segment the eddy current path, dividing the large eddy current region that may be caused by the skin effect and proximity effect into multiple independent, smaller eddy currents. This also reduces the effective conductor size and suppresses the skin effect. The hybrid cross-section winding optimizes the magnetic field distribution, weakening the eddy current losses generated by higher harmonic magnetic fields. The synergistic effect of these two technologies allows for the control of the skin effect and eddy current losses while maintaining the slot fill factor, significantly reducing AC losses under high-frequency operating conditions.

[0040] The following uses a 6-layer flat wire winding as an example to illustrate the implementation of the present invention in detail. 1. Initial specifications of motor windings This example uses a 6-layer flat wire winding structure. The sub-slots are defined radially (depth direction) from the back (slot bottom) to the air gap side (slot opening), numbered sequentially from layer 1 (L1) to layer 6 (L6). The original design (traditional constant cross-section scheme) has the following single flat wire conductor dimensions: radial height a = 4.0 mm, tangential width b = 12.0 mm. Slot fill factor: ≥70%. Figure 5 As shown.

[0041] 2. Specific design parameters for improved winding structure The regions are divided into: Region 1 (High Eddy Current Loss Region): Layers L5 and L6. Closest to the air gap, it is most affected by high-frequency harmonic magnetic fields and permanent magnet leakage magnetic fields; Region 2 (Medium Eddy Current Loss Region): Layers L3 and L4. Located in the middle of the tank, it is mainly affected by the armature reaction magnetic field; Region 3 (High DC Loss Region): Layers L1 and L2. Located at the bottom of the tank, the magnetic field is weakest.

[0042] Partition optimization strategy: Region 1 (High Eddy Current Loss Region): The L5 layer adopts tangential segmentation (downward cutting direction) to divide the conductor into upper and lower parallel insulator conductors along the radial (height direction). The L6 layer adopts radial and tangential segmentation to replace the original single conductor with 4 mutually insulated sub-conductors. All sub-conductors are connected in parallel at the ends. Region 2 (Medium Eddy Current Loss Region): Layers L3 and L4 are tangentially divided, dividing the conductors radially (height direction) into upper and lower parallel insulator conductors; Region 3 (High DC Loss Region): Layers L1 and L2 are not segmented, but their cross-sectional area is increased. Furthermore, while satisfying the global copper area balance principle (or slot fill factor), the radial dimensions of each conductor in Regions 1 and 2 are adjusted, as follows: To reduce DC resistance, the radial height of the L1 and L2 conductor layers is increased. The amplification factor is determined. Therefore, the new heights of the L1 and L2 layer conductors are:

[0043] Width remains unchanged To keep the total copper area constant, according to the formula...

[0044] The adjusted heights of layers L3-L5 and L6 were calculated.

[0045] The new dimensions of the conductors in layers L3-L6 are: height ,width .

[0046] After regional segmentation and cross-sectional area adjustment, L1-L2 remain as a single solid flat wire of 5.0mm × 12.0mm; L3-L4 layers are radially divided into upper and lower insulator conductors, which remain as single solid flat wires. mm × 12.0 mm; the L5 layer is radially divided into upper and lower insulator conductors, maintaining a single solid flat wire. mm × 12.0 mm. The L6 layer conductor is divided into 4 insulator conductors equally along the tangential and radial directions. Dimensions of each sub-conductor: height ,width Of course, layers L5 and L6 can also be divided into four insulator conductors along the tangential and radial directions.

[0047] Conductor surface slotting design: All through slot widths are fixed. Layers L1 and L2: No slotting. Layer L3 has one axial through slot at the center of the radial sidewall of each sub-conductor near the rotor, with a slot depth of... (approximately the height of the sub-conductor) (28.6%). The L4 layer has two through-slots near the center on the radial sidewall of each sub-conductor, with a slot depth of... In layer L5, three through slots are formed near the center on the radial sidewall of each sub-conductor. The slots near the center (closest to the centerline of the slot) are deeper. (34% of the height); the grooves on both sides are shallower, with a depth of (20% of the height). Two slots are formed on the radial sidewalls of the four-strand conductor in section L6, with a slot depth of... , Simultaneously, tangential slotting is performed on all conductors. One through slot is created on each of the two tangential sidewalls of each sub-conductor, with a slot depth of... (Considering the significant contribution of the tangential magnetic field to losses in this region, the slot depth is slightly greater than that of the radial slots). The final winding structure is as follows: Figure 6 As shown.

[0048] The above is only used to explain the technical solution and is not intended to limit the present invention.

Claims

1. A slotted flat wire winding based on layered suppression and mixed cross-section, characterized in that, The system includes stator slots and multi-layer winding conductors disposed therein; the multi-layer winding conductors are sequentially divided into a high eddy current loss region, a medium eddy current loss region, and a high DC loss region along the radial direction of the slot from the slot opening to the slot bottom; the conductors located in the high eddy current loss region are divided radially, tangentially, or by a combination of both to form multi-strand insulator conductors with parallel ends; the conductors located in the medium eddy current loss region are divided tangentially to form multi-strand insulator conductors with parallel ends; the conductors located in the high DC loss region are undivided solid conductors, and their radial height is greater than the radial height of the single-strand sub-conductors after division in the high eddy current loss region and the medium eddy current loss region; at least a portion of the conductor surfaces in the high eddy current loss region and the medium eddy current loss region are provided with axially extending slots.

2. The slotted flat wire winding based on layered suppression and mixed cross-section according to claim 1, characterized in that, The high eddy current loss region, medium eddy current loss region, and high DC loss region are divided according to the distribution gradient of the radial magnetic field strength and tangential magnetic field strength formed by the combined action of the armature reaction magnetic field and the permanent magnet leakage magnetic field within the stator slot. Specifically, the high eddy current loss region is the slot opening area that is strongly affected by both the radial and tangential magnetic fields, the medium eddy current loss region is the middle slot area that is mainly affected by the tangential magnetic field, and the high DC loss region is the slot bottom area where both the radial and tangential magnetic fields are attenuated to almost zero.

3. The slotted flat wire winding based on layered suppression and mixed cross-section according to claim 1 or 2, characterized in that, The radial segmentation refers to dividing the conductor into multiple parallel insulator conductors along its tangential direction to reduce the tangential dimension of a single sub-conductor, thereby suppressing eddy current losses caused by the tangential magnetic field; the tangential segmentation refers to dividing the conductor into multiple parallel insulator conductors along its radial height direction to reduce the radial dimension of a single sub-conductor, thereby suppressing eddy current losses caused by the radial magnetic field.

4. The slotted flat wire winding based on layered suppression and mixed cross-section according to claim 1 or 2, characterized in that, The radial height of the conductor in the high DC loss region is increased, while the radial height of the conductor in the high eddy current loss region and the medium eddy current loss region is reduced accordingly, so that the total conductor cross-sectional area in the entire stator slot remains unchanged, satisfying the global copper area balance relationship.

5. The slotted flat wire winding based on layered suppression and mixed cross-section according to claim 4, characterized in that, The global copper area balance relationship satisfies the following formula: n a b = (nm) a e1 b + m a e2 b ,in, n The total number of conductor layers. m The number of conductor layers in the high DC loss region. a The radial height of the conductor in the original constant cross-section design. b The tangential width of the conductor. a e2 To increase the radial height of the conductor in the high DC loss region, a e1 The radial height of the single-strand conductor in the adjusted high eddy current loss region and medium eddy current loss region.

6. The slotted flat wire winding based on layered suppression and hybrid cross-section according to claim 1, characterized in that, The depth and number of grooves on the conductor surface are determined according to the magnetic field strength gradient of the region. The higher the magnetic field strength, the deeper the grooves and the more grooves there are.

7. The slotted flat wire winding based on layered suppression and mixed cross-section according to claim 6, characterized in that, On the radial sidewalls of the same conductor layer, the groove depth near the center line of the groove is greater than the groove depth near the sides of the groove wall.

8. The slotted flat wire winding based on layered suppression and mixed cross-section according to claim 1, characterized in that, The conductor material in the high eddy current loss region is replaced with a conductive material with a resistivity higher than that of copper.

9. A design method for slotted flat wire windings based on layered suppression and mixed cross-section, characterized in that, Includes the following steps: The radial distribution of the armature reaction magnetic field and the leakage magnetic field of the permanent magnet in the stator slot was quantitatively analyzed to obtain the radial and tangential magnetic flux density distributions of each conductor layer. Based on the magnetic field intensity distribution gradient, the stator slots are divided radially from the slot opening to the slot bottom into a high eddy current loss region, a medium eddy current loss region, and a high DC loss region. For conductors in the high eddy current loss region, radial segmentation, tangential segmentation, or a combination of both are used to divide them into multiple mutually insulated sub-conductors, with each sub-conductor connected in parallel at its ends; The conductor in the eddy current loss region is tangentially split into multiple mutually insulated sub-conductors, and each sub-conductor is connected in parallel at the ends; For conductors in the high DC loss region, a solid, undivided structure is adopted, and their radial height is increased; Based on the principle of global copper area balance, the radial height of the conductors in the high eddy current loss region and the medium eddy current loss region is adjusted so that the total copper area of ​​the sub-slot remains basically unchanged. Based on the magnetic field intensity gradient of each region, differentiated axial through slots are processed on the conductor surface in the high eddy current loss region and the medium eddy current loss region. The higher the magnetic field intensity, the more slots are opened and the greater the slot depth.

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