Method and system for manufacturing high-frequency ac loss reduction insulation winding based on a litz wire

Abstract

The application discloses a high-frequency AC loss reduction insulation winding manufacturing method and system based on a Litz wire, relates to the winding manufacturing technical field of a high-frequency electromagnetic element, and comprises the following steps: determining the diameter of a single wire, the total number of strands and a multi-stage reverse twisting scheme according to a target working frequency and a rated current, and manufacturing a single wire with a self-adhesive insulation layer; performing hierarchical twisting, and untwisting in the opposite direction after each hierarchical twisting; filling the Litz wire core with inter-strand heat-conducting insulation glue and wrapping the Litz wire core with an external insulation tape; winding and forming in a heated state; finally, detecting the high-frequency loss of the coil, and adjusting process parameters such as the twisting pitch according to the detection result; and the system comprises a Litz wire preparation unit, an insulation processing unit, a winding forming unit, a detection feedback unit and a central control system; the application realizes the systematic integration of parameter design, insulation processing and winding forming, and effectively reduces the high-frequency AC loss through closed-loop feedback optimization.

Description

Technical Field

[0001] This invention belongs to the field of high-frequency electromagnetic component winding manufacturing technology, and specifically discloses a method and system for manufacturing high-frequency AC loss-reducing insulating windings based on Litz wire. Background Technology

[0002] High-frequency electromagnetic components are core components of power electronic systems. With the application of wide-bandgap semiconductor devices, the operating frequency has increased from the kilohertz level to hundreds of kilohertz, and the power density has increased significantly, but the high-frequency losses of the windings have also increased dramatically.

[0003] Under high-frequency AC conditions, the skin effect and proximity effect distort the current distribution, resulting in AC resistance that is much greater than DC resistance. Studies have shown that the AC / DC resistance ratio of a solid conductor can reach over 5 at 500kHz. To suppress these losses, Litz wire (composed of multiple strands of insulated fine wire twisted in a regular pattern) is widely used. By controlling the diameter of each strand within the skin depth and achieving inter-strand transposition through multi-stage twisting, Litz wire can effectively balance the current distribution and reduce high-frequency losses.

[0004] However, existing Leeds wire and its winding technology still have the following shortcomings:

[0005] From the selection of single strand diameter, total number of strands, number of strands and pitch at each stage, there is a lack of a complete parameter chain design method based on a unified physical model. It is difficult to achieve optimal matching of parameters at each stage, resulting in unstable loss reduction effect.

[0006] During the winding process, Litz wire is subjected to compression, bending, and tension fluctuations, which can easily damage the insulating varnish film between strands, leading to short circuits and wire failure. Existing solutions mostly complete the insulation coating during the manufacturing stage, lacking targeted insulation reinforcement treatment after winding; the adhesive application and winding parameters also lack linkage optimization with the structural parameters of Litz wire.

[0007] Winding losses are usually tested after the finished product is completed. It is impossible to monitor and adjust process parameters in real time during the winding process, making it difficult to guarantee product consistency and yield.

[0008] After multi-stage twisting, the interstrand bonding force of Litz wire is limited, and it is easy to loosen and misalign when the winding is bent, which affects the transposition effect and filling coefficient. The existing untwisting treatment lacks a matching design with the twisting parameters, and the untwisting effect is difficult to quantify and control.

[0009] Therefore, it is necessary to invent a method and system for manufacturing high-frequency AC loss-reducing insulated windings based on Litz wire to solve the above problems. Summary of the Invention

[0010] To overcome the aforementioned deficiencies in the prior art, this invention provides a method and system for manufacturing high-frequency AC loss-reducing insulated windings based on Litz wire. The method involves determining the diameter of a single-strand conductor, the total number of strands, and a multi-stage reverse stranding scheme according to the target operating frequency and rated current; manufacturing a single-strand conductor with a self-adhesive insulation layer; performing staged stranding and untwisting in the opposite direction after each stage; filling the Litz wire core with thermally conductive insulating adhesive between strands and wrapping it with external insulating tape; winding the wire under heating; and finally, performing high-frequency loss detection on the coil and adjusting process parameters such as stranding pitch based on the detection results. This effectively solves the problems mentioned in the background art.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a method for manufacturing high-frequency AC loss-reducing insulating windings based on Leeds wire, specifically including the following steps:

[0012] Obtain the operating frequency and rated current of the target high-frequency electromagnetic component;

[0013] The diameter of a single-strand insulated wire is determined based on the skin depth at the operating frequency, wherein the diameter is less than or equal to the critical diameter corresponding to the skin depth.

[0014] The total number of strands of the Litz wire is determined based on the rated current and the current-carrying capacity of the single-strand insulated conductor.

[0015] The graded stranding scheme is determined based on the total number of strands, and the graded stranding scheme includes the number of stranding levels and the number of strands in each stranding level;

[0016] According to the graded stranding scheme, multi-strand single-strand insulated wires are stranded step by step. The stranding direction of each stage is opposite to that of the previous stage. Each stage of stranding has a stranding pitch determined according to the outer diameter of the current stage wire and the number of strands. After each stage of stranding, the wires are untwisted in the opposite direction and shaped to form the Litz wire core.

[0017] The Litz wire core is subjected to insulation reinforcement treatment, which includes inter-strand insulation filling and external insulation covering;

[0018] The Litz wire, after insulation enhancement treatment, is wound into a coil.

[0019] The high-frequency loss of the wound coil is tested, and the process conditions of the step-by-step stranding and / or the winding process conditions are adjusted according to the test results.

[0020] A high-frequency AC loss-reducing insulation winding fabrication system based on Leeds wire includes:

[0021] The Litz wire preparation unit includes a pay-off frame, a multi-stage stranding machine, a de-twisting device, and an online outer diameter monitor. The pay-off frame is used to hold multiple rolls of single-strand insulated wire and provide independent tension control. The multi-stage stranding machine is used to strand multiple single-strand insulated wires in stages. The de-twisting device is set between every two stages of the stranding machine to perform reverse rotation de-twisting and hot air shaping on the stranded bundles. The online outer diameter monitor is used to monitor the outer diameter of the Litz wire core in real time.

[0022] An insulation treatment unit, located downstream of the Litz wire preparation unit, includes an impregnation tank, an extrusion device, a curing channel, a wrapping machine, and a coating and curing device arranged sequentially. The impregnation tank is used to hold thermally conductive insulating adhesive and impregnate the Litz wire core. The extrusion device is used to control the amount of thermally conductive insulating adhesive applied. The curing channel is used to heat and cure the impregnated Litz wire core. The wrapping machine is used to wrap insulating tape around the surface of the cured Litz wire core. The coating and curing device is used to coat the surface of the wrapping layer with thermosetting insulating varnish and cure it.

[0023] A winding forming unit, located downstream of the insulation treatment unit, includes a winding machine, a heating device, and an insulation protection device. The winding machine is used to wind the Litz wire after insulation enhancement treatment into shape. The heating device is used to heat and activate the self-adhesive hot-melt insulation layer on the surface of the Litz wire during the winding process. The insulation protection device includes a guide wheel with a surface coated with polytetrafluoroethylene or a ceramic coating and a tension buffer mechanism.

[0024] The detection and feedback control unit includes a high-frequency impedance analyzer, a data acquisition and processing module, and a feedback control module. The high-frequency impedance analyzer is used to measure the AC resistance and DC resistance of the coil after winding. The data acquisition and processing module is used to collect sensor data from each process stage. The feedback control module is used to adjust the process parameters of the multi-stage stranding machine and / or the winding machine according to the deviation between the detection results and the design target value.

[0025] The central control system is communicatively connected to the Litz wire preparation unit, the insulation treatment unit, the winding forming unit, and the detection and feedback control unit, respectively. It is used to receive design input parameters and perform parameter design calculations, send control commands to each execution unit, receive detection data for quality judgment and process parameter optimization and adjustment, and store process parameters and detection data.

[0026] The technical effects and advantages of this invention are as follows:

[0027] 1. Starting from high-frequency operating conditions, this invention determines the single-strand wire diameter based on the skin depth model, and calculates the total number of strands and the graded stranding scheme according to the rated current system, so that the parameters of each link are uniformly matched. Multi-stage reverse stranding combined with step-by-step untwisting treatment makes each strand of conductor evenly distributed in the cross section, effectively suppressing the inter-strand circulating current loss.

[0028] 2. In this invention, the inter-strand insulation filling and external insulation covering are performed sequentially before winding. The thermally conductive insulating adhesive not only enhances insulation but also improves heat dissipation. The external insulation layer provides mechanical protection during the winding process to prevent short circuits between strands from causing Litz wire failure. The inter-turn bonding of the self-adhesive layer simplifies the process and improves efficiency.

[0029] 3. This invention eliminates the internal stress of stranding by quantitatively controlling the untwisting angle and hot air shaping, making the Litz wire less prone to loosening and misalignment during subsequent winding bending, thus ensuring the long-term effectiveness of the transposition effect. Attached Figure Description

[0030] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0031] Figure 1 This is a flowchart of the method of the present invention.

[0032] Figure 2 This is the logic diagram for high-frequency loss detection and feedback control of the present invention.

[0033] Figure 3 This is a system architecture diagram of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention provides, for example Figure 1 The method for fabricating high-frequency AC loss-reducing insulating windings based on Litz wire, as shown, specifically includes the following steps:

[0036] Obtain the operating frequency and rated current of the target high-frequency electromagnetic component;

[0037] The diameter of a single-strand insulated wire is determined based on the skin depth at the operating frequency, wherein the diameter is less than or equal to the critical diameter corresponding to the skin depth.

[0038] It should be further noted that, in a preferred embodiment of the present invention, the skin depth δ is determined according to the formula... Calculate, where ω is the angular frequency, ω = 2πf, μ is the permeability of the conductor material, and σ is the electrical conductivity of the conductor material. The diameter d of the single-strand insulated conductor is chosen to be less than or equal to... The value of d ensures that the ratio of AC resistance to DC resistance of a single-strand wire at the operating frequency is ≤1.05, thus suppressing skin effect losses within an acceptable range. Preferably, when the operating frequency f is in the range of 10kHz to 100kHz, the diameter d of the single-strand wire is selected from 0.10mm to 0.30mm; when the operating frequency f is in the range of 100kHz to 500kHz, the diameter d of the single-strand wire is selected from 0.05mm to 0.10mm; and when the operating frequency f is above 500kHz, the diameter d of the single-strand wire is selected from 0.03mm to 0.05mm.

[0039] The total number of strands of the Litz wire is determined based on the rated current and the current-carrying capacity of the single-strand insulated conductor.

[0040] It should be further noted that, in the preferred embodiment of this invention, the total number of Leeds lines N = (I·K) / (J·A) s ), where J is the economic current density of a single-strand conductor, A s I is the cross-sectional area of ​​a single conductor, I is the rated current, and K is the safety margin factor, with a value ranging from 1.1 to 1.5.

[0041] The current-carrying capacity of the single-strand insulated conductor is determined based on the conductor material and insulation heat resistance class. For polyimide-insulated (Class H, heat resistant to 180℃) copper conductors, the economic current density J ranges from 3 to 6 A / mm²; for copper-clad aluminum composite conductors, the economic current density J ranges from 2 to 4 A / mm². The lower limit is used when the rated current is high to ensure controllable temperature rise, while the upper limit is used when the rated current is low to optimize material utilization.

[0042] The graded stranding scheme is determined based on the total number of strands, and the graded stranding scheme includes the number of stranding levels and the number of strands in each stranding level;

[0043] It should be further noted that, in the preferred embodiment of the present invention, the number of stranding stages is set to m, and the number of strands in each stranding stage is n1, n2, ..., n. m The total number of shares is N, satisfying: N = n1 × n2 × ... × n m .

[0044] The number of stranding levels is matched according to the total number of shares: 2-level stranding is used when the total number of shares N≤50, 3-level stranding is used when 50<N≤300, and 4-level stranding is used when N>300.

[0045] When the number of twisting stages m≥2, the number of strands n in the i-th stage (i≥2) twisting is... i The value range is [2, 5].

[0046] According to the graded stranding scheme, multi-strand single-strand insulated wires are stranded step by step. The stranding direction of each stage is opposite to that of the previous stage. Each stage of stranding has a stranding pitch determined according to the outer diameter of the current stage wire and the number of strands. After each stage of stranding, the wires are untwisted in the opposite direction and shaped to form the Litz wire core.

[0047] Furthermore, in the above technical solution, the stranding pitch of each stage in the graded stranding scheme is determined as follows:

[0048] The first-stage stranding pitch L1 = (8~15) × d, which means that the first-stage stranding pitch is 8~15 times the outer diameter d of a single-strand insulated wire;

[0049] i-th level twist pitch L i =(1.2~1.5)×L i-1 , indicating that the pitch of the i-th level twist is 1.2 to 1.5 times that of the pitch of the (i-1)-th level twist, where i ∈ [2, m].

[0050] Furthermore, in the above technical solution, during the step-by-step stranding process, the outer diameter of the Litz wire core is monitored in real time after each stranding stage, and the outer diameter deviation is controlled within a preset allowable deviation range; during each stranding stage, each single insulated conductor is independently controlled with constant tension, and the tension deviation between each conductor is controlled within a preset tension consistency range.

[0051] It should be further noted that, in the preferred embodiment of this invention, the outer diameter monitoring employs a laser diameter gauge, with at least three measuring points evenly arranged circumferentially along the direction of travel of the Litz wire core. The average value of the measurements is taken as the actual outer diameter value. The outer diameter deviation is controlled within ±3%. When the measured outer diameter exceeds the preset allowable deviation range of the target outer diameter, the system automatically alarms and adjusts the traction speed of the stranding machine or the compression ratio of the stranding die to bring the outer diameter back within the allowable range.

[0052] The process of staged twisting is as follows:

[0053] First-stage stranding: n1 single-strand insulated wires are stranded together at a pitch L1 to form the first-stage strand bundle. Constant tension control is used during the stranding process, with the tension of each single wire controlled between 0.5 and 2.0 N, and the tension deviation of each strand not exceeding ±5%.

[0054] Untwisting process: After each stage of twisting is completed, an untwisting operation is performed. After untwisting, the strand bundle is shaped.

[0055] Repeat the above process to complete the stranding from level 2 to level m, finally forming the Leeds wire core.

[0056] Furthermore, in the above technical solution, the specific operation of the untwisting and shaping process is as follows: rotating by a preset angle in the opposite direction of the stranding direction to eliminate the back-twisting stress generated by this stage of stranding; after untwisting, heating is used to make the insulation layer between each strand of wire in the strand bundle slightly adhered to maintain the stability of the strand bundle structure.

[0057] It should be further noted that, in the preferred embodiment of this invention, the un-twisting direction is opposite to the twisting direction, and the preset angle for the un-twisting operation is determined based on the twisting angle of that stage of twisting. The twisting angle θ is calculated according to the formula θ = 360° × (L p / L t ) calculate, where L p L is the length of the twisted section. t The twisting pitch is set to 80% to 95% of the twist angle. The residual twist angle after twisting is controlled within 5% to 20% of the twist angle to maintain appropriate cohesion and prevent the strands from loosening, while eliminating excessive back-twist stress.

[0058] The shaping process uses hot air heating. For self-adhesive hot-melt insulation layers, the hot air temperature is preferably 100~130℃. The hot air shaping time is determined based on the Litz wire travel speed and the length of the heating channel, ensuring that the strands remain in the heating zone for no less than 1 second to fully soften the insulation layer and achieve slight adhesion between the strands.

[0059] Furthermore, in the above technical solution, the single-strand insulated wire includes a conductor and an insulating layer covering the outside of the conductor. The insulating layer is a double-layer composite structure, consisting of an inner polyimide insulating varnish layer and an outer self-adhesive hot-melt insulating layer. The material of the self-adhesive hot-melt insulating layer is thermoplastic polyester or polyamide.

[0060] It should be further explained that the material of the conductor is selectively determined according to the operating frequency: when the operating frequency f ≤ 100kHz, high conductivity oxygen-free copper (conductivity ≥ 100% IACS) is selected as the conductor; when the operating frequency f > 100kHz, copper-clad aluminum composite conductor is selected as the conductor, with the copper layer thickness being 2%~5% of the conductor diameter and the aluminum core diameter being 90%~96% of the conductor diameter. The lower conductivity of the aluminum core is used to reduce proximity effect losses, while the copper layer is used to ensure good solderability and conductivity.

[0061] The inner polyimide insulating varnish layer is applied using a mold coating method, completed through 3-6 coating-curing cycles. After each coating, it is cured in an oven at 300-450℃, with the final insulating varnish layer thickness controlled at 5-15μm. The outer self-adhesive hot-melt insulating layer is made of thermoplastic polyester or polyamide material, and is applied to the outside of the polyimide insulating varnish layer by extrusion coating, with a thickness controlled at 3-8μm. The activation temperature of the self-adhesive hot-melt insulating layer is lower than the heat resistance temperature of the polyimide insulating varnish layer, ensuring that the inner insulation is not damaged during winding heating activation.

[0062] Preferably, after each stage of stranding is completed, before entering the next stage of stranding, the core of the Litz wire is cleaned by means of compressed air blowing or brush cleaning to remove impurities such as copper powder and insulation debris generated during stranding, so as to avoid impurities entering the subsequent insulation treatment stage and affecting the insulation quality.

[0063] The Litz wire core is subjected to insulation reinforcement treatment, which includes inter-strand insulation filling and external insulation covering;

[0064] Furthermore, in the above technical solution, the inter-strand insulation filling includes:

[0065] The Litz wire core is passed through an impregnation tank containing thermally conductive insulating adhesive at a preset travel speed, and the impregnation temperature is the process applicable temperature of the thermally conductive insulating adhesive.

[0066] After impregnation, the Litz wire core is passed through an extrusion device to remove excess thermally conductive insulating adhesive from the surface under a preset extrusion pressure, and to promote the filling of the gaps between the strands with thermally conductive insulating adhesive.

[0067] The Litz wire core is fed into the curing channel and cured at the curing temperature of the thermally conductive insulating adhesive for a preset time.

[0068] It should be further noted that, in a preferred embodiment of the present invention, the wire core passes through the impregnation tank at a speed of 0.5~5 m / min. The impregnation tank contains a thermally conductive insulating adhesive, preferably an epoxy resin-based thermally conductive insulating adhesive, with a thermal conductivity ≥1.0 W / (m·K) and a volume resistivity ≥10. 14 Ω·cm, with the impregnation temperature controlled at 40~60℃ to ensure that the thermally conductive insulating adhesive fully penetrates into the gaps between the strands of the conductor.

[0069] The impregnation tank is equipped with guide rollers and impregnation pressure rollers. Under the action of the impregnation pressure rollers, the Litz wire core is completely immersed below the surface of the thermally conductive insulating adhesive. The impregnation pressure rollers apply an auxiliary pressure of 0.1~0.3 MPa to the wire core to promote the deep penetration of the thermally conductive insulating adhesive into the interstrand gaps.

[0070] The extrusion device includes upper and lower extrusion rollers, the surface of which is covered with a polyurethane or silicone rubber elastic layer. The roller spacing is precisely adjusted by a servo motor, with an adjustment range of 85% to 95% of the Litz wire core diameter. A residual adhesive recovery tank is provided at the outlet of the extrusion device, and the collected thermally conductive insulating adhesive is filtered and returned to the impregnation tank for recycling.

[0071] The curing channel is a segmented temperature-controlled tunnel oven, divided sequentially into a heating zone, a constant temperature zone, and a cooling zone along the Leeds line. In the heating zone, the temperature linearly rises from room temperature to the curing temperature; in the constant temperature zone, the curing temperature is maintained; and in the cooling zone, the core temperature is reduced to below 60°C through natural cooling or forced air cooling. An inert gas protection device is installed within the curing channel to prevent oxidation of the thermally conductive insulating adhesive during the high-temperature curing process.

[0072] Furthermore, in the above technical solution, the external insulation covering in the insulation enhancement treatment specifically involves: using insulating tape as the wrapping material, spirally wrapping it around the surface of the Litz wire core after the inter-strand insulation is filled by overlapping and pressing the edges of adjacent tapes together, with the wrapping tension being a preset tension value; after wrapping, applying thermosetting insulating varnish to the surface of the external insulation layer, and curing it at a preset temperature.

[0073] It should be further noted that the width of the insulating tape is determined based on the outer diameter of the Litz wire core, and the ratio of the tape width W to the outer diameter D of the core ranges from [3, 8]. In the method of overlapping and crimping adjacent tape edges, the ratio of the overlap width of two adjacent tapes to the tape width ranges from 50% to 65%. The angle between the tape length direction and the core axis direction ranges from 15° to 30°.

[0074] After wrapping, a thermosetting insulating varnish, either polyesterimide or polyamideimide, is applied to the surface of the outer insulation layer, with a coating thickness of 10~20μm. The high-temperature curing treatment is carried out at 150~180℃ for 20~40 minutes to allow the thermosetting insulating varnish to fully cross-link and cure, forming an integrated insulating protective layer with the outer insulation tape.

[0075] The Litz wire, after insulation enhancement treatment, is wound into a coil.

[0076] Furthermore, in the above technical solution, during the process of winding the Litz wire after insulation enhancement treatment, a preset winding tension and winding speed are used for winding; during the winding process, the Litz wire is heated to a temperature above the activation temperature of the self-adhesive hot-melt insulation layer; after the winding is completed, an overall heat treatment is performed to fully solidify the self-adhesive layer between each turn.

[0077] The high-frequency loss of the wound coil is tested, and the process conditions of the step-by-step stranding and / or the winding process conditions are adjusted according to the test results.

[0078] It should be further noted that before winding, the winding process parameters are set according to the previously determined operating frequency and the structural parameters of the litz wire:

[0079] Winding tension: determined according to the wire diameter and the number of strands of the litz wire. For a litz wire with a total number of strands N≤100 and an outer diameter ≤2mm, the winding tension is preferably 0.5~2N; for a litz wire with a total number of strands 100<N≤500 and an outer diameter of 2~5mm, the winding tension is preferably 2~4N; for a litz wire with a total number of strands N>500 and an outer diameter >5mm, the winding tension is preferably 4~8N.

[0080] Winding speed: determined comprehensively according to the number of strands of the litz wire and the winding tension. The larger the total number of strands and the higher the tension, the correspondingly lower the winding speed. Preferably, the winding speed ranges from 0.3 to 3 m / s. The following relationship is satisfied between the winding speed and the winding tension: v×T≤K v , where v is the winding speed (m / s), T is the winding tension (N), K v is the speed-tension product constant, with a value range of 1.5~6 N·m / s.

[0081] Winding temperature: for a litz wire containing a self-adhesive insulating layer, the litz wire is heated to the activation temperature of the self-adhesive layer by a heating device during the winding process, so that adjacent turns are bonded during winding;

[0082] Winding pitch: determined according to the outer diameter of the litz wire and the coil design requirements, to ensure a uniform gap between turns.

[0083] During the winding process, an insulation protection device is provided between the guiding mechanism of the winding machine and the winding mold, which includes: (1) the surface of the guide wheel is coated with a polytetrafluoroethylene or ceramic coating to reduce frictional damage to the insulating layer of the litz wire; (2) a tension buffer mechanism, which uses a spring damping system to absorb instantaneous tension fluctuations during the winding process, so as to prevent the insulating layer from cracking due to sudden force.

[0084] After the winding is completed, the coil is subjected to integral heat treatment at a temperature of 150~180°C for a holding time of 30~60 minutes, so that the self-adhesive layer between each turn is fully cured, and the inter-strand insulating glue is completely cured at the same time. The heating rate is controlled at 2~5°C / min, and the cooling rate is controlled at 3~8°C / min, so as to avoid coil deformation or insulating layer cracking caused by thermal stress.

[0085] Further, in the above technical solution, as Figure 2 shown, the performing high-frequency loss detection on the wound and formed coil is specifically: measuring the AC resistance R of the coil ac and the DC resistance R dc , calculating the AC / DC resistance ratio R ac / R dc ; taking Rac / R dc Compare with the design expected value:

[0086] If R ac / R dc ≤ the first preset threshold, the coil is determined to be qualified;

[0087] If the first preset threshold < R ac / R dc ≤ the second preset threshold, it is determined that process adjustment is required to reduce the stranding pitch and / or increase the winding tension;

[0088] If R ac / R dc > the second preset threshold, it is determined to be unqualified;

[0089] The first preset threshold and the second preset threshold are calculated through the design expected value.

[0090] It should be further noted that, in the preferred technical solution of the present invention, the AC resistance R ac is measured using a high-frequency impedance analyzer, the measurement frequency covers the range of 0.5 to 2 times the target operating frequency f, and the AC resistance value is read at the target operating frequency f. Before measurement, the high-frequency impedance analyzer needs to be calibrated for open circuit, short circuit and standard load, with no less than 10 calibration frequency points to ensure measurement accuracy.

[0091] The DC resistance R dc is measured by the four-terminal method (Kelvin method), and the measurement current shall not exceed 10% of the rated current-carrying capacity of a single conductor, so as to avoid the self-heating effect from affecting the measurement accuracy. The ambient measurement temperature is controlled at 20±2℃. If the measurement cannot be performed at the standard ambient temperature, the measured value shall be corrected to the standard value at 20℃ according to the resistance temperature coefficient of copper conductor (0.00393 / ℃).

[0092] The first preset threshold is preferably set to 1.0 to 1.1 times the design expected value, and the second preset threshold is preferably 1.3 to 1.5 times the design expected value. The design expected value is determined according to the statistical average value of qualified samples in the same batch.

[0093] As Figure 3 shown, the high-frequency AC loss-reducing insulated winding manufacturing system based on litz wire includes:

[0094] A litz wire preparation unit, including a pay-off stand, a multi-stage stranding machine, a untwisting device and an online outer diameter monitor, where the pay-off stand is used to place multiple rolls of single-strand insulated wires and provide independent tension control, the multi-stage stranding machine is used for grading and stranding multiple single-strand insulated wires, the untwisting device is arranged between every two stages of stranding machines for performing reverse rotation untwisting and hot air setting on the stranded strands, and the online outer diameter monitor is used for real-time monitoring of the outer diameter of the litz wire core;

[0095] An insulation treatment unit, located downstream of the Litz wire preparation unit, includes an impregnation tank, an extrusion device, a curing channel, a wrapping machine, and a coating and curing device arranged sequentially. The impregnation tank is used to hold thermally conductive insulating adhesive and impregnate the Litz wire core. The extrusion device is used to control the amount of thermally conductive insulating adhesive applied. The curing channel is used to heat and cure the impregnated Litz wire core. The wrapping machine is used to wrap insulating tape around the surface of the cured Litz wire core. The coating and curing device is used to coat the surface of the wrapping layer with thermosetting insulating varnish and cure it.

[0096] A winding forming unit, located downstream of the insulation treatment unit, includes a winding machine, a heating device, and an insulation protection device. The winding machine is used to wind the Litz wire after insulation enhancement treatment into shape. The heating device is used to heat and activate the self-adhesive hot-melt insulation layer on the surface of the Litz wire during the winding process. The insulation protection device includes a guide wheel with a surface coated with polytetrafluoroethylene or a ceramic coating and a tension buffer mechanism.

[0097] The detection and feedback control unit includes a high-frequency impedance analyzer, a data acquisition and processing module, and a feedback control module. The high-frequency impedance analyzer is used to measure the AC resistance and DC resistance of the coil after winding. The data acquisition and processing module is used to collect sensor data from each process stage. The feedback control module is used to adjust the process parameters of the multi-stage stranding machine and / or the winding machine according to the deviation between the detection results and the design target value.

[0098] The central control system is communicatively connected to the Litz wire preparation unit, the insulation treatment unit, the winding forming unit, and the detection and feedback control unit, respectively. It is used to receive design input parameters and perform parameter design calculations, send control commands to each execution unit, receive detection data for quality judgment and process parameter optimization and adjustment, and store process parameters and detection data.

[0099] It should be further noted that in the Litz wire preparation unit, the independent tension controller of the pay-off frame adopts a magnetic powder brake or servo motor drive, with a tension control accuracy of ±0.1N. The stranding die of the multi-stage stranding machine is made of polytetrafluoroethylene or ceramic material, and a lubrication device is provided at the die inlet, using graphite or molybdenum disulfide dry lubricant to reduce frictional damage between the wire and the die during stranding.

[0100] In the insulation treatment unit, the impregnation tank, extrusion device, and curing channel are connected by a sealed connection to form a closed insulation treatment path, preventing the volatiles of the thermally conductive insulating adhesive from diffusing into the workshop environment. The exhaust port of the curing channel is connected to a tail gas treatment device, which treats the organic waste gas using activated carbon adsorption or catalytic combustion.

[0101] In the winding forming unit, the tension buffer mechanism of the insulation protection device adopts a spring damping system or a pneumatic damping system, which can absorb instantaneous tension fluctuations caused by acceleration changes during the winding process. The PTFE or ceramic coating covering the surface of the guide wheel has a coefficient of friction ≤0.15 and a hardness ≥HRC 55, in order to minimize frictional wear on the outer insulation layer of the Litz wire.

[0102] In the detection and feedback control unit, the data acquisition and processing module has a sampling frequency of ≥1kHz. The acquired sensor data includes, but is not limited to: stranding tension at each stage, stranding speed, stranding pitch, core outer diameter, impregnation temperature, extrusion pressure, curing temperature, winding tension, winding speed, and heating temperature. All acquired data is timestamped and stored in the database of the central control system, forming a traceable production process record.

[0103] The central control system communicates with each execution unit via industrial Ethernet or fieldbus to ensure real-time control command issuance and sensor data feedback. The central control system has a built-in process parameter optimization algorithm that automatically calculates the adjustment direction and amount of process parameters based on loss detection results uploaded by the detection and feedback control unit. After confirmation by the operator, the algorithm is sent to each execution unit for execution.

[0104] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating high-frequency AC loss-reducing insulated windings based on Leeds wire, characterized in that, Includes the following steps: Obtain the operating frequency and rated current of the target high-frequency electromagnetic component; The diameter of a single-strand insulated wire is determined based on the skin depth at the operating frequency, wherein the diameter is less than or equal to the critical diameter corresponding to the skin depth. The total number of strands of the Litz wire is determined based on the rated current and the current-carrying capacity of the single-strand insulated conductor. The graded stranding scheme is determined based on the total number of strands, and the graded stranding scheme includes the number of stranding levels and the number of strands in each stranding level; According to the described graded stranding scheme, multiple single-strand insulated wires are stranded step by step to form Litz wire cores. The Litz wire is wound into shape to form a coil; Each level of twisting is opposite to the previous level of twisting, and each level of twisting has a twisting pitch determined according to the outer diameter and number of strands of the current level. After each level of twisting, the strands are untwisted in the opposite direction of twisting and then shaped. The Litz wire core is subjected to insulation reinforcement treatment, which includes filling the inter-strand thermally conductive insulating adhesive and covering it with external insulating tape. Litz wire, after insulation enhancement treatment, is wound into shape under a heated and activated state; The high-frequency loss of the wound coil is tested, and the process conditions of the step-by-step stranding and / or the winding process conditions are adjusted according to the test results.

2. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: In the graded stranding scheme, the stranding pitch of each stage is determined as follows: The first-stage stranding pitch L1 = (8~15) × d, where d is the outer diameter of a single-strand insulated wire; i-th level twist pitch L i =(1.2~1.5)×L i-1 , where i = 2, 3, ..., m.

3. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: The specific operation of the untwisting and shaping process is as follows: rotate by a preset angle in the opposite direction of the stranding direction to eliminate the back-twisting stress generated by this stage of stranding; after untwisting, heat is used to make the insulation layer between each strand of the strand slightly adhered to maintain the stability of the strand structure.

4. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: The single-strand insulated wire includes a conductor and an insulating layer covering the outside of the conductor. The insulating layer is a double-layer composite structure, consisting of an inner polyimide insulating varnish layer and an outer self-adhesive hot-melt insulating layer. The material of the self-adhesive hot-melt insulating layer is thermoplastic polyester or polyamide.

5. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: The interstrand insulation filler includes: The Litz wire core is passed through an impregnation tank containing thermally conductive insulating adhesive at a preset travel speed, and the impregnation temperature is the process applicable temperature of the thermally conductive insulating adhesive. After impregnation, the Litz wire core is passed through an extrusion device to remove excess thermally conductive insulating adhesive from the surface under a preset extrusion pressure, and to promote the filling of the gaps between the strands with thermally conductive insulating adhesive. The Litz wire core is fed into the curing channel and cured at the curing temperature of the thermally conductive insulating adhesive for a preset time.

6. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: The external insulation wrapping in the insulation enhancement process specifically involves: using insulating tape as the wrapping material, spirally wrapping it around the surface of the Litz wire core after the inter-strand insulation is filled in a way that the edges of adjacent tapes overlap and press together, with the wrapping tension being a preset tension value. After the wrapping is completed, a thermosetting insulating varnish is applied to the surface of the outer insulation layer and cured at a preset temperature.

7. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: During the process of winding the Litz wire after insulation enhancement treatment, a preset winding tension and winding speed are used for winding; the Litz wire is heated during the winding process, and the heating temperature reaches above the activation temperature of the self-adhesive hot melt insulation layer; after the winding is completed, an overall heat treatment is performed to fully cure the self-adhesive layer between each turn.

8. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: The high-frequency loss detection of the wound coil specifically involves measuring the AC resistance R of the coil. ac and DC resistance R dc Calculate the AC / DC resistance ratio R ac / R dc ; R ac / R dc Compare with the expected design value: If R ac / R dc is less than or equal to a first preset threshold, the coil is determined to be qualified; If the first preset threshold <R ac / R dc If the value is less than or equal to the second preset threshold, it is determined that process adjustments are needed, such as reducing the stranding pitch and / or increasing the winding tension. If R ac / R dc The second preset threshold is used to determine if the test is unqualified. The first preset threshold and the second preset threshold are calculated based on the expected design values.

9. The method for manufacturing high-frequency AC loss-reducing insulating winding based on Litz wire according to claim 1, characterized in that: During the step-by-step stranding process, the outer diameter of the Litz wire core is monitored in real time after each stranding stage, and the outer diameter deviation is controlled within a preset allowable deviation range. During each stranding stage, each single insulated conductor is independently controlled with constant tension, and the tension deviation between each conductor is controlled within a preset tension consistency range.

10. A high-frequency AC loss-reducing insulation winding fabrication system based on Leeds wire, applied to the high-frequency AC loss-reducing insulation winding fabrication method based on Leeds wire as described in any one of claims 1-9, characterized in that: include: The Litz wire preparation unit includes a pay-off frame, a multi-stage stranding machine, a de-twisting device, and an online outer diameter monitor. The pay-off frame is used to hold multiple rolls of single-strand insulated wire and provide independent tension control. The multi-stage stranding machine is used to strand multiple single-strand insulated wires in stages. The de-twisting device is set between every two stages of the stranding machine to perform reverse rotation de-twisting and hot air shaping on the stranded bundles. The online outer diameter monitor is used to monitor the outer diameter of the Litz wire core in real time. An insulation treatment unit, located downstream of the Litz wire preparation unit, includes an impregnation tank, an extrusion device, a curing channel, a wrapping machine, and a coating and curing device arranged sequentially. The impregnation tank is used to hold thermally conductive insulating adhesive and impregnate the Litz wire core. The extrusion device is used to control the amount of thermally conductive insulating adhesive applied. The curing channel is used to heat and cure the impregnated Litz wire core. The wrapping machine is used to wrap insulating tape around the surface of the cured Litz wire core. The coating and curing device is used to coat the surface of the wrapping layer with thermosetting insulating varnish and cure it. A winding forming unit, located downstream of the insulation treatment unit, includes a winding machine, a heating device, and an insulation protection device. The winding machine is used to wind the Litz wire after insulation enhancement treatment into shape. The heating device is used to heat and activate the self-adhesive hot-melt insulation layer on the surface of the Litz wire during the winding process. The insulation protection device includes a guide wheel with a surface coated with polytetrafluoroethylene or a ceramic coating and a tension buffer mechanism. The detection and feedback control unit includes a high-frequency impedance analyzer, a data acquisition and processing module, and a feedback control module. The high-frequency impedance analyzer is used to measure the AC resistance and DC resistance of the coil after winding. The data acquisition and processing module is used to collect sensor data from each process stage. The feedback control module is used to adjust the process parameters of the multi-stage stranding machine and / or the winding machine according to the deviation between the detection results and the design target value. The central control system is communicatively connected to the Litz wire preparation unit, the insulation treatment unit, the winding forming unit, and the detection and feedback control unit, respectively. It is used to receive design input parameters and perform parameter design calculations, send control commands to each execution unit, receive detection data for quality judgment and process parameter optimization and adjustment, and store process parameters and detection data.

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