Wire structure based on filler and multiple twisted litz wire and preparation method thereof

Abstract

The application provides a wire structure based on a filler and a multiple-twisted Litz wire and a preparation method, and belongs to the technical field of megahertz power electronics. The preparation method of the wire structure based on the filler and the multiple-twisted Litz wire comprises the following steps: S1, determining an optimal arrangement mode in wire multiple-twisting; S2, twisting fine copper wires and coating a filler to obtain a primary structure wire; and S3, according to the optimal arrangement mode in wire multiple-twisting determined in step S1, repeating multiple-level twisting on the structure wire of the previous step and adding the filler until the optimal arrangement mode in wire multiple-twisting determined in step S1 is met; the repeated multiple-level twisting at least comprises secondary twisting on the primary structure wire. The application increases the spacing between the fine copper wires in the wire through the filler, reduces the megahertz frequency band alternating current loss of the obtained Litz wire, and suppresses the proximity effect and skin effect of the high frequency in the wire through the internal structure arrangement optimization of the wire, thereby reducing the loss of the obtained Litz wire.

Description

Technical Field

[0001] This invention belongs to the field of megahertz power electronics technology, specifically, it relates to a wire structure and preparation method based on filler and multiple stranded Litz wire, and in particular, a novel high-frequency megahertz wire structure and preparation method based on filler and multiple stranded Litz wire. Background Technology

[0002] Megahertz (MHz) power electronics technology has received widespread attention and achieved significant development in recent years. The main research areas in megahertz power electronics technology include the research and design of megahertz fundamental devices and materials, the research and design of megahertz high-efficiency inverters (power amplifiers), the research and design of megahertz high-efficiency rectifiers and synchronous rectification control algorithms, and the research and design of megahertz high-efficiency transformers. Among these, the research and design of megahertz fundamental devices and materials is of paramount importance, serving as the foundation for other research areas in megahertz power electronics technology.

[0003] Wire is the most fundamental material in the field of power electronics, used to connect circuits or to further manufacture inductors, coils, and other equipment. Traditionally, wires used in the megahertz frequency band are made of ordinary Litz wire, ordinary copper foil, or ordinary solid copper wire. Due to the proximity and skin effect at high frequencies, these traditional wires often have high internal resistance and high losses in the megahertz frequency band. Inductors and coils made from these wires have high internal resistance and low quality factor at high megahertz frequencies, resulting in a decrease in overall system efficiency. Therefore, researching, designing, and developing a new type of wire structure suitable for megahertz power electronics is of great significance.

[0004] Currently, the relevant existing technologies include: (1) High-frequency electrical concentric twisted Litz wire (patent document CN203165496U) This patent document discloses a high-frequency electrical concentric twisted Litz wire, including a rectangular outer insulation layer, wherein the outer insulation layer is provided with a concentric rectangular twisted Litz wire formed by concentric transposition and twisting of multiple Litz wire strands to form two or more even-numbered rows of multiple columns; the technical solution uses concentric twisting, which is insufficient in terms of high-frequency loss suppression capability.

[0005] (2) A Litz wire for medium- and high-frequency transformers (Patent document CN206179579U) This patent document discloses a Litz wire for medium- and high-frequency transformers, comprising: an outer insulating layer, a shielding layer, a braided layer, a No. 1 filler, a No. 2 filler, and multiple enameled wires; the multiple enameled wires are divided into at least two parallel groups; the adjacent enameled wires are tangent to each other, and a No. 1 filler and a No. 2 filler are provided between the adjacent enameled wires; the multiple enameled wires are covered by a braided layer, the outer surface of the braided layer is covered by a shielding layer, and the outer surface of the shielding layer is covered by an outer insulating layer; the enameled wires are composed of multiple strands of single wire and insulating varnish; compared with the concentric structure, it has a stronger ability to suppress high-frequency losses, but this patent does not consider internal losses.

[0006] (3) A stranded Litz wire, reactor and manufacturing apparatus for medium and high frequency electrical applications (Patent document CN209343798U) This patent document discloses a stranded Litz wire, reactor and manufacturing apparatus for medium and high frequency electrical applications, which relates to the field of cable equipment technology. It includes a bundle-shaped protective layer and a wire core. The bundle-shaped protective layer is arranged around the surface outside the wire core. The wire core includes multiple strands of spirally twisted Litz wire. Each Litz wire includes multiple insulated and spirally twisted conductors. The cross-section of the bundle-shaped protective layer and the wire core is approximately rectangular. The scope of application of this technical solution is relatively limited. The description of the application frequency is limited to medium and high frequency. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a wire structure and preparation method based on filler and multiple stranded Litz wire.

[0008] The method for preparing a wire structure based on filler and multiple stranded Litz wire according to the present invention includes: Step S1: Determine the total number of fine copper wires in the wire structure, the total number and diameter of each stranded wire, and the total filler amount of the wire structure; Step S2: Based on the total number of fine copper wires in the primary structure wire determined in step S1 and the diameter of the primary structure wire, twist the fine copper wires together and cover them with filler for the first time to obtain the primary structure wire. Step S3: Based on the total number of fine copper wires in the stranded structure wire, the total number and diameter of each level of stranded structure wire, and the total filler amount of the wire structure confirmed in Step S1, repeat the multi-level stranding and filler addition for the previous level structure wire until the total number and diameter of each level of stranded structure wire and the total filler amount of the wire structure are satisfied as determined in Step S1. The repeated multi-stage twisting includes at least a second-stage twisting of the primary structure line.

[0009] Preferably, the filler coating method is to increase the paint thickness or to incorporate non-conductive material, and the filler filling amount is expressed as the non-copper wire area ratio.

[0010] Preferably, step S1 includes: Step S1.1: Obtain the eddy current loss of a single thin copper wire; Step S1.2: Combining the eddy current loss of the single thin copper wire in step S1.1, obtain the AC internal resistance of the wire. The mathematical relationship between the amount of filling material and the amount of filling material; Step S1.3: Combine with the AC internal resistance of the wire in step S1.2 Obtain the overall internal resistance R of the wire; Step S1.4: Combining the overall wire resistance R from step S1.3 and the wire AC resistance from step S1.2. The mathematical relationship between the amount of fine copper wire and the amount of filler is used to determine the number of fine copper wires N and the non-copper wire area ratio δ. Step S1.5: Combine the results from steps S1.1 to S1.4 to obtain the fine copper wire arrangement and stranding method, including: the number of fine copper wires, the total number of wires in each stranding structure, the initial phase and diameter.

[0011] Preferably, in step S1.1, for a single fine copper wire, the eddy current loss of the wire conductor is proportional to the fourth power of the diameter, the square of the operating frequency, the reciprocal of the resistivity, and the square of the magnetic field strength. The time-averaged eddy current loss is derived using formula (1):

[0012] Where l is the length of a single thin copper wire, d is the diameter of a single thin copper wire, and ω is the angular frequency of the operating frequency. ρ is the peak amplitude of the sinusoidal magnetic field at the location of a single thin copper wire, and ρ is the resistivity of the single thin copper wire. In step S1.2, the non-copper wire area ratio δ is defined as the ratio of the total area of ​​non-copper wires in the cross-section of the wire to the cross-sectional area of ​​the wire, which is used to represent the amount of filler. The formula for calculating δ is as follows:

[0013] Where S is the total cross-sectional area of ​​the wire, N is the total number of fine copper wires, and d is the diameter of each fine copper wire. When S is fixed, N causes a change in δ, which in turn causes a change in loss: When S is fixed and the wire structure is fixed, a change in N will not cause a change in current distribution or magnetic flux density. The spatial distribution remains unchanged; the total wire loss increases linearly with the number of copper wires; combining formula (1), the total AC internal resistance of the wire is:

[0014] Where P is the eddy current loss of a single thin copper wire in formula (1), k is the internal resistance-single wire loss proportional coefficient, and I is the total current flowing through the wire. When N is fixed, S causes a change in δ, which in turn causes a change in loss: Changes in the cross-sectional area S of the wire will affect the average distance between fine copper wires. The change; due to the square relationship between distance and area, The relationship between S and S is also quadratic:

[0015] Where α is the coefficient of proportionality between average distance and number of roots; According to Biosavart's law, the magnetic induction intensity in formula (1) It is proportional to the total current intensity I passing through the wire and the average distance between the copper wires. The inverse relationship is as follows:

[0016] Where β is the proportionality coefficient between the magnetic induction intensity and the average distance of the current; Combining and simplifying formulas (1), (4), and (5), the AC internal resistance of a single copper wire is obtained. The relationship between the wire cross-section S and the wire cross-section is shown in formula (6):

[0017] Combining formula (6) and formulas (1) to (3), we can obtain The relationship between δ and its value is:

[0018] Wherein, ε is the proportionality coefficient between AC loss and copper wire density; In step S1.3, the total internal resistance R of the wire is determined by the DC internal resistance. With communication resistance The total DC internal resistance of the wire is determined jointly. The calculation is as follows:

[0019] Where N is the number of fine copper wires, l is the length of each fine copper wire, s is the cross-sectional area of ​​each fine copper wire, and ρ is the resistivity of the copper wire. Combining formulas (7) and (8), the overall internal resistance R of the wire is obtained as follows:

[0020] In step S1.4, in formula (9), since all parameters except N are fixed values, the total internal resistance of the wire is considered as a function of the number of fine copper wires N; when N takes a specific optimal value (denoted as n), the total internal resistance R of the wire can take the minimum value, thereby minimizing the total loss of the wire; the value of n satisfies the following formula (10):

[0021] Combining formulas (9) and (10), the specific value of the optimal value of N, n, is calculated using formula (11):

[0022] At this point, with the cross-sectional area of ​​the copper wire and the cross-sectional area of ​​the wire fixed, the optimal total resistance of the wire is obtained by adding filler. Combining formulas (2) and (11), the corresponding non-copper wire area ratio δ is calculated as follows:

[0023] Step S1.5: Obtaining the fine copper wire arrangement and twisting method; including: Each copper wire in the stranded wire structure is represented by the parametric equation shown in the following formula (13):

[0024] Where j represents the number of the fine copper wire, and h represents the parameter variable in the parametric equation. This represents the x-coordinate of the line in a Cartesian coordinate system. This represents the y-coordinate of the line in a Cartesian coordinate system. This represents the z-coordinate of the line in a Cartesian coordinate system, and t represents the total number of twists. This represents the intercept of the i-th twist. This represents the twist radius of the j-th copper wire in the i-th twist. This indicates the initial (phase) position of the j-th copper wire during the i-th twist; In each stranding process of the wire structure, the number of wires involved in the stranding is less than or equal to six, and the stranding radius of the wires is the same in each stranding process. The wire structure and its corresponding mathematical expression are obtained as shown in formulas (14) and (15):

[0025] Where N represents the total number of copper wires, and q represents the total number of twisting operations. This represents the twist radius of the i-th twist. This represents the number of strands in the i-th twist. This represents the initial reference phase in the i-th twist.

[0026] Preferably, in step S2: every several fine copper wires are first stranded; after stranding, a filler is wrapped around the surface of the stranded structure to form a primary structural wire; Step S3 includes: Step S3.1: Based on the total number and diameter of the primary structural lines in the secondary structural lines determined in step S1, twist multiple primary structural lines together and then cover them with filler material for the second time to obtain the secondary structural lines; Step S3.2: Based on the total number and diameter of the secondary structural lines in the tertiary structural line determined in step S1, twist multiple secondary structural lines together and cover them with filler for the third time to obtain the tertiary structural line; After three layers of filling material application in steps S2, S3.1, and S3.2, the total filling material amount meets the total filling material amount of the wire structure determined in step S1.

[0027] Preferably, in step S3.1: the primary structural wire obtained in step S2 is twisted together to obtain a secondary structural wire, and filler is added. If the filler in step S2 already meets the total filler amount of the wire structure in step S1, then no more filler is added. In step S3.2: the secondary structure wires obtained in step S3.1 are twisted together to obtain tertiary structure wires, and filler is added. If the filler in step S3.1 already meets the total filler amount of the wire structure in step S1, no more filler is added.

[0028] The present invention provides a megahertz wire structure based on filler and multiple stranded Litz wire, which is obtained by the novel high-frequency megahertz wire structure preparation method based on filler and multiple stranded Litz wire provided by the present invention. It has the performance of suppressing the proximity effect and skin effect of current at high frequencies and reducing loss and internal resistance in the megahertz frequency band.

[0029] Preferably, the wire structure is formed by multiple fine copper wires twisted together in multiple stages, the fine copper wires are evenly and symmetrically arranged in space, and there is a non-conductive filler between each fine copper wire.

[0030] Preferably, the fine copper wire is pre-coated with filler by increasing the enamel thickness or coating with a non-conductive material.

[0031] Preferably, the wire structure is used to wind a megahertz coil.

[0032] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention reasonably increases the distance between different fine copper wires in the Litz wire structure by adding filler according to the arrangement optimization during the multi-stage winding process, thereby reducing the eddy current loss and AC internal resistance of each copper wire. In particular, it reduces the high-frequency (megahertz band) AC loss of the wire compared with the traditional concentric twisted structure. 2. This invention improves, optimizes, and averages the current distribution in different fine copper wires by repeatedly twisting multiple copper wires in the Litz wire, making each fine copper wire as symmetrical as possible in spatial position; it suppresses the proximity effect and skin effect of current at high frequencies, thereby reducing the loss and internal resistance of the wire in the megahertz frequency band, and further improving the quality factor and other performance of inductors and coils made of this wire in the megahertz frequency band. 3. This invention, through the design of the number and arrangement of fine copper wires, takes into account the influence of AC internal resistance and DC internal resistance, and can achieve excellent control effect on DC and AC losses under different numbers of fine copper wires. 4. The macroscopic structure of the wire obtained by this invention is similar to that of traditional wire, which makes it easy to produce the new type of wire proposed in this solution by simply modifying existing production equipment, thereby reducing production costs. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the copper wire arrangement structure of the present invention.

[0034] Figure 2 This is a schematic diagram of the current distribution across the cross-section of the optimized structural wire in this invention.

[0035] Figure 3 This is a schematic diagram of the winding process according to an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of an inductor and coil prepared according to an embodiment of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0038] like Figures 1 to 3 As shown, this embodiment of the invention provides a method for preparing a wire structure based on filler and multiple stranded Litz wire, comprising: Step S1: Determine the total number of fine copper wires in the wire structure, the total number and diameter of each stranded wire, and the total filler amount of the wire structure; Step S2: Based on the total number of fine copper wires in the primary structure wire determined in step S1 and the diameter of the primary structure wire, the fine copper wires are twisted together and the filler is wrapped for the first time to obtain the primary structure wire. Step S3: Based on the total number of fine copper wires in the stranded structure wire, the total number and diameter of each level of stranded structure wire, and the total filler amount of the wire structure confirmed in Step S1, repeat the multi-level stranding and filler addition for the previous level structure wire until the total number and diameter of each level of stranded structure wire and the total filler amount of the wire structure are satisfied as determined in Step S1. Repeated multi-stage twisting includes at least a second stage of twisting the primary structure wire.

[0039] Furthermore, the filler is filled by increasing the paint thickness or by incorporating non-conductive materials, and the filler amount is expressed as the non-copper wire area ratio.

[0040] Further, step S1 includes: Step S1.1: Obtain the eddy current loss of a single thin copper wire; specifically, for a single thin copper wire, the eddy current loss of the wire conductor is proportional to the fourth power of the diameter, the square of the operating frequency, the reciprocal of the resistivity, and the square of the magnetic field strength. The time-averaged eddy current loss is derived from formula (1):

[0041] Where l is the length of a single thin copper wire, d is the diameter of a single thin copper wire, and ω is the angular frequency of the operating frequency. ρ is the peak amplitude of the sinusoidal magnetic field at the location of a single thin copper wire, and ρ is the resistivity of the single thin copper wire. Step S1.2: Obtain the AC internal resistance of the wire The mathematical relationship between the amount of filler and the non-copper wire area ratio δ is defined as the ratio of the total area of ​​non-copper wires in the cross-section of the wire to the cross-sectional area of ​​the wire. It is used to characterize the amount of filler. The more filler, the larger the value of δ. Specifically, the formula for calculating δ is as follows:

[0042] Where S is the total cross-sectional area of ​​the wire, N is the total number of fine copper wires, and d is the diameter of each fine copper wire. When S is fixed, N causes a change in δ, which in turn causes a change in loss: When S is fixed and the wire structure is fixed, a change in N will not cause a change in current distribution or magnetic flux density. The spatial distribution therefore remains unchanged; the AC loss of the wire increases linearly with the number of copper wires; at this time, using formula (1), the total AC internal resistance of the wire is:

[0043] Where P is the eddy current loss of a single thin copper wire in formula (1), k is the AC internal resistance - single wire loss proportional coefficient, and I is the total current flowing through the wire. When N is fixed, S causes a change in δ, which in turn causes a change in loss: Changes in the cross-sectional area S of the wire will affect the average distance between fine copper wires. The change; due to the square relationship between distance and area, The relationship between S and S is also quadratic, specifically:

[0044] Where α is the coefficient of proportionality between average distance and number of roots; According to Biosavart's law, the magnetic induction intensity in formula (1) is... It is proportional to the total current intensity I passing through the wire and the average distance between the copper wires. It is inversely proportional, as specifically given by formula (5):

[0045] Where β is the proportionality coefficient between the magnetic induction intensity and the average distance of the current; Combining and simplifying formulas (1), (4), and (5), the relationship between the AC internal resistance of a single copper wire and S is shown in the following formula (6):

[0046] Formula (3) shows that the total AC internal resistance of the wire It is directly proportional to the total number of copper wires N; Formula (6) shows that the total AC internal resistance of the wire is inversely proportional to the cross-sectional area S of the wire; Combining with Formula (2), we can give The relationship between the δ value and the δ value is given by formula (7):

[0047] Where ε is the AC loss-copper wire density proportional coefficient, formula (7) shows that by adding filler to increase the non-copper wire area ratio δ of the wire, the AC internal resistance of the wire can be effectively suppressed. ; Step S1.3: Obtain the overall internal resistance R of the wire; the total internal resistance R of the wire is determined by the DC internal resistance. With communication resistance Together, we decided that the following sections would discuss how to minimize the total internal resistance of the wire by adding filler. Total DC internal resistance of the wire The calculation is as follows:

[0048] Where N is the number of fine copper wires, l is the length of each fine copper wire, s is the cross-sectional area of ​​each fine copper wire, and ρ is the resistivity of the copper wire. Combining formulas (7) and (8), the overall internal resistance R of the wire is obtained as follows:

[0049] Step S1.4: Determine the number of fine copper wires N; specifically: in formula (9), since all parameters except N are fixed values, the total internal resistance of the wire can be regarded as a function of the number of fine copper wires N; when N takes a specific optimal value (denoted as n), the total internal resistance R of the wire can take the minimum value, thereby minimizing the total loss of the wire; the value of n satisfies the following formula (10):

[0050] Combining formulas (9) and (10), the specific value of the optimal value of N, n, is calculated using formula (11):

[0051] At this point, with the cross-sectional area of ​​the copper wire and the cross-sectional area of ​​the wire fixed, the optimal total resistance of the wire can be obtained by adding filler. Combining formulas (2) and (11), the corresponding non-copper wire area ratio δ can be calculated as follows:

[0052] Step S1.5: Obtain the arrangement and twisting method of the fine copper wires; including: Each copper wire in the stranded wire structure is represented by the parametric equation shown in the following formula (13):

[0053] Where j represents the number of the fine copper wire, and h represents the parameter variable in the parametric equation. This represents the x-coordinate of the line in a Cartesian coordinate system. This represents the y-coordinate of the line in a Cartesian coordinate system. This represents the z-coordinate of the line in a Cartesian coordinate system, and t represents the total number of twists. This represents the intercept of the i-th twist. This represents the twist radius of the j-th copper wire in the i-th twist. This indicates the initial (phase) position of the j-th copper wire during the i-th twist; Furthermore, to achieve a more precise and superior control effect, in a more preferred embodiment, the present invention provides a wire structure and its corresponding mathematical expression; the structure has the following main features: in each stranding process, the number of wires involved in stranding is less than or equal to six, and the stranding radius of the wires is the same each time; its mathematical expression is based on formula (13), with relevant features supplemented by formulas (14) and (15):

[0054] In the formula, N represents the total number of copper wires, and q represents the total number of twisting operations. This represents the twist radius of the i-th twist. This represents the number of strands in the i-th twist. This represents the initial reference phase in the i-th twist; meanwhile, the wire example model constructed by formulas (13), (14), and (15) is as follows: Figure 1 As shown; Furthermore, Figure 2 The optimized structure of this wire, as shown by formulas (13), (14), and (15), demonstrates the suppression effect of proximity effect and skin effect at high frequencies (taking 6.78MHz as an example). Specifically, the current in different fine copper wires is relatively consistent (e.g., ...). Figure 2 The leftmost sub-figure shows the distribution of current in a common copper wire arrangement with the same number of copper wires and the same cross-sectional area. The middle and right sub-figures represent the distribution of current in a common copper wire arrangement with the same number of copper wires and the same cross-sectional area.

[0055] Furthermore, in step S2 above: every few fine copper wires are first stranded; after stranding, a filler is wrapped around the surface of the stranded structure to form a primary structural wire; Step S3 above includes: Step S3.1: Based on the total number and diameter of the primary structural lines in the secondary structural lines determined in step S1, twist multiple primary structural lines together and then cover them with filler material for the second time to obtain the secondary structural lines; Step S3.2: Based on the total number and diameter of the secondary structural lines in the tertiary structural line determined in step S1, twist multiple secondary structural lines together and cover them with filler for the third time to obtain the tertiary structural line; After three layers of filling material application in steps S2, S3.1, and S3.2, the total filling material amount meets the total filling material amount of the wire structure determined in step S1.

[0056] Further, in step S3.1 above: the primary structural wire obtained in step S2 is twisted to obtain the secondary structural wire, and filler is added. If the filler in step S2 already meets the overall filler amount of the wire structure in step S1, then no more filler is added; specifically: since the filler in the primary structural wire may have a certain volume, elasticity and toughness, it plays the role of filler in the secondary structural wire and increases the distance between the thin copper wires; therefore, it can be omitted for cost considerations. In step S3.2 above: the secondary structure wires obtained in step S3.1 are twisted together to obtain tertiary structure wires, and filler is added. If the filler in step S3.1 already meets the total filler amount of the wire structure in step S1, no more filler is added.

[0057] The Litz wire with a multi-twisted structure and filler, manufactured according to the proposed scheme, exhibits a significant performance improvement in the megahertz frequency band compared to traditional Litz wire.

[0058] More specifically, this invention also provides a megahertz wire structure based on filler and multiple stranded Litz wire. This structure is obtained through the novel high-frequency megahertz wire fabrication method provided in this invention, which suppresses the proximity effect and skin effect of current at high frequencies, and reduces losses and internal resistance in the megahertz band. The wire structure is formed by multiple fine copper wires stranded in multiple stages, with the fine copper wires arranged uniformly and symmetrically in space. Each fine copper wire is separated by a non-conductive filler such as insulating varnish or nylon wire.

[0059] The following is a more specific embodiment to further illustrate the point: Example 1 In a more specific embodiment, the filler and the formation of the multiple-stranded structure are achieved by repeatedly twisting the wrapped Litz wire, such as... Figure 3 As shown, the wire has 6 6 30 The wire has a 0.03mm diameter; it can be used as a general wire, or to make inductors and coils, such as... Figure 4 As shown, the upper left is the wire, the lower left is the wire used to wind the inductor, and the right is the wire used to wind the coil. In this embodiment: In step S2, several fine copper wires with a diameter of 0.03 mm are prepared, and 30 fine copper wires are twisted together for the first time. After twisting, a layer of nylon filament is wrapped around the surface of the twisted structure as a filler to form 30 strands. The primary structure line is 0.03.

[0060] In step S3.1, the six primary structural wires are twisted together to form six 30 0.03 Secondary structure line; At this time, the nylon filaments on the surface of the primary structure line, due to their own certain volume, elasticity and toughness, meet the filler area requirements when determining the arrangement method, and play the role of filler in the secondary structure line and increase the distance between the fine copper wires.

[0061] In step S3.2, the six secondary structure wires are twisted together to form six 6 30 The tertiary structure line is 0.03; at this time, the nylon filaments on the surface of the primary structure line continue to act as filler and increase the distance between the fine copper wires.

[0062] In a more preferred embodiment, the fine copper wire is pre-coated with filler by increasing the enamel thickness or coating with a non-conductive material, and the amount of filler in the fine copper wire coating affects the value of δ.

[0063] The coils wound using the novel high-frequency megahertz wire structure based on filler and multiple stranded Litz wire obtained through the above steps were analyzed using a network analyzer, and the results are shown in the table below:

[0064] Compared to existing ordinary Litz wire products, which have an inductance of 4.15uH, an internal resistance of 0.46Ω, and a quality factor of 387 at 6.78MHz with the same number of turns, the Litz wire with filler in this application has an inductance of 3.38uH, an internal resistance of 0.15Ω, and a quality factor of 973 at 6.78MHz. Compared to traditional wire (ordinary Litz wire products), this application shows a significant performance improvement in the megahertz frequency band.

[0065] More specifically, the implementation principle of this invention is as follows: for a given system and copper wire, the wire length, wire diameter, operating frequency, and resistivity of the material are all fixed values. Therefore, the loss P can be reduced by decreasing the magnetic induction intensity of the magnetic field at the location of the wire. According to the principle of linear superposition of magnetic fields, the magnetic induction intensity at the location of each thin wire is equal to the superposition of the magnetic fields generated by all other thin wires at that point. According to the Biot-Savart principle, under the condition that the current distribution remains basically unchanged, the farther each thin wire is from other thin copper wires, the lower the magnetic induction intensity value at its location. Correspondingly, as can be seen from formula (1), the lower the magnetic induction intensity, the smaller the loss. Therefore, in terms of filler, by using different means, while ensuring that the structure remains approximately unchanged, increasing the filler can significantly increase the spacing between different thin wires in the Litz wire, thereby significantly reducing the AC internal resistance of the Litz wire in the megahertz frequency band. In terms of arrangement, ordinary Litz wires are usually composed of many fine copper wires randomly. The arrangement of the fine copper wires in this invention is specially designed to meet the requirements of repeated stranding. The core purpose of this repeated stranding is to make each fine copper wire as symmetrical and uniform as possible in spatial position, so as to avoid the phenomenon of current being too concentrated on certain wires, reduce the skin effect and proximity effect of current distribution in the megahertz frequency band, make the current distribution between different fine wires as even as possible, and thus reduce AC loss and AC internal resistance.

[0066] In summary, this invention provides a wire structure and preparation method based on filler and multiple stranded Litz wire. The preparation method of the wire structure based on filler and multiple stranded Litz wire includes: Step S1: Determining the optimal arrangement in the wire stranding; Step S2: Stranding fine copper wires and covering them with filler to obtain a primary structure wire; Step S3: According to the optimal arrangement in the wire stranding confirmed in Step S1, repeating multiple stranding and adding filler to the previous stage structure wire until the optimal arrangement in the wire stranding determined in Step S1 is satisfied; the repeated multiple stranding includes at least a secondary stranding of the primary structure wire. The filler is added by increasing the enamel thickness or by stranding in non-conductive materials; the filler increases the spacing between the fine copper wires in the wire, reducing the AC loss in the megahertz band of the obtained Litz wire; the optimized internal structure arrangement of the wire suppresses the proximity effect and skin effect at high frequencies in the wire, reducing the high-frequency AC internal resistance and AC loss of the obtained Litz wire.

[0067] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0068] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for preparing a wire structure based on filler and multiple stranded Litz wire, characterized in that, include: Step S1: Determine the total number of fine copper wires in the wire structure, the total number and diameter of each stranded wire, and the total filler amount of the wire structure; Step S2: Based on the total number of fine copper wires in the primary structure wire determined in step S1 and the diameter of the primary structure wire, the fine copper wires are twisted together and the filler is wrapped for the first time to obtain the primary structure wire. Step S3: Based on the total number of fine copper wires in the stranded structure wire, the total number and diameter of each level of stranded structure wire, and the total filler amount of the wire structure confirmed in Step S1, repeat the multi-level stranding and filler addition for the previous level structure wire until the total number and diameter of each level of stranded structure wire and the total filler amount of the wire structure are satisfied as determined in Step S1. The repeated multi-stage twisting includes at least a second-stage twisting of the primary structure wire; The filling material is coated by increasing the paint thickness or by incorporating non-conductive materials. The filling material amount is expressed as the non-copper wire area ratio. Step S1 includes: Step S1.1: Obtain the eddy current loss of a single thin copper wire; Step S1.2: Combining the eddy current loss of the single thin copper wire in step S1.1, obtain the AC internal resistance of the wire. The mathematical relationship between the amount of filling material and the amount of filling material; Step S1.3: Combine with the AC internal resistance of the wire in step S1.2 Obtain the internal resistance R of the entire wire; Step S1.4: Combining the overall wire resistance R from step S1.3 and the wire AC resistance from step S1.

2. The mathematical relationship between the amount of fine copper wire and the amount of filler is used to determine the number of fine copper wires N and the non-copper wire area ratio δ. Step S1.5: Combine the results from steps S1.1 to S1.4 to obtain the fine copper wire arrangement and stranding method, including: the number of fine copper wires, the total number of wires in each stranding structure, the initial phase and diameter; In step S1.1, the eddy current loss of a single thin copper wire conductor is proportional to the fourth power of the diameter, the square of the operating frequency, the reciprocal of the resistivity, and the square of the magnetic field strength. The time-averaged eddy current loss is derived from formula (1): Where l is the length of a single thin copper wire, d is the diameter of a single thin copper wire, and ω is the angular frequency of the operating frequency. ρ is the peak amplitude of the sinusoidal magnetic field at the location of a single thin copper wire, and ρ is the resistivity of the single thin copper wire. In step S1.2, the non-copper wire area ratio δ is defined as the ratio of the total area of ​​non-copper wires in the cross-section of the wire to the cross-sectional area of ​​the wire, which is used to represent the amount of filler. The formula for calculating δ is as follows: Where S is the total cross-sectional area of ​​the wire, N is the total number of fine copper wires, and d is the diameter of each fine copper wire. When S is fixed, N causes a change in δ, which in turn causes a change in loss: When S is fixed and the wire structure is fixed, a change in N will not cause a change in current distribution or magnetic flux density. The spatial distribution remains unchanged; the total wire loss increases linearly with the number of copper wires; combining formula (1), the total AC internal resistance of the wire is: Where P is the eddy current loss of a single thin copper wire in formula (1), k is the internal resistance-single wire loss proportional coefficient, and I is the total current flowing through the wire. When N is fixed, S causes a change in δ, which in turn causes a change in loss: Changes in the cross-sectional area S of the wire will affect the average distance between fine copper wires. The change; due to the square relationship between distance and area, The relationship between S and S is also quadratic: Where α is the coefficient of proportionality between average distance and number of roots; According to Biosavart's law, the magnetic induction intensity in formula (1) It is proportional to the total current intensity I passing through the wire and the average distance between the copper wires. The inverse relationship is as follows: Where β is the proportionality coefficient between the magnetic induction intensity and the average distance of the current; Combining formulas (1), (4), and (5) and simplifying them, the relationship between the AC internal resistance of a single copper wire and S is shown in formula (6): Combining formula (6) and formulas (1) to (3), we can obtain The relationship between δ and its value is: Wherein, ε is the proportionality coefficient between AC loss and copper wire density; In step S1.3, the total internal resistance R of the wire is determined by the DC internal resistance. With communication resistance The total DC internal resistance of the wire is determined jointly. The calculation is as follows: Where N is the number of fine copper wires, l is the length of each fine copper wire, s is the cross-sectional area of ​​each fine copper wire, and ρ is the resistivity of the copper wire. Combining formulas (7) and (8), the overall internal resistance R of the wire is obtained as follows: In step S1.4, in formula (9), since all parameters except N are fixed values, the total internal resistance of the wire is considered as a function of the number of fine copper wires N; when N takes a specific optimal value (denoted as n), the total internal resistance R of the wire can take the minimum value, thereby minimizing the total loss of the wire; the value of n satisfies the following formula (10): Combining formulas (9) and (10), the specific value of the optimal value of N, n, is calculated using formula (11): At this point, with the cross-sectional area of ​​the copper wire and the cross-sectional area of ​​the wire fixed, the optimal total resistance of the wire is obtained by adding filler. Combining formulas (2) and (11), the corresponding non-copper wire area ratio δ is calculated as follows: Step S1.5: Obtaining the fine copper wire arrangement and twisting method; including: Each copper wire in the stranded wire structure is represented by the parametric equation shown in the following formula (13): Where j represents the number of the fine copper wire, and h represents the parameter variable in the parametric equation. This represents the x-coordinate of the line in a Cartesian coordinate system. This represents the y-coordinate of the line in a Cartesian coordinate system. This represents the z-coordinate of the line in a Cartesian coordinate system, and t represents the total number of twists. This represents the intercept of the i-th twist. This represents the twist radius of the j-th copper wire in the i-th twist. This indicates the initial phase position of the j-th copper wire during the i-th twisting; In each stranding process of the wire structure, the stranding radius of the wire is the same each time. The wire structure and its corresponding mathematical expression are obtained as shown in formulas (14) and (15): Where N represents the total number of copper wires, and q represents the total number of twisting operations. This represents the twist radius of the i-th twist. This represents the number of strands in the i-th twist. This represents the initial reference phase in the i-th twist; In step S2: every few fine copper wires are first stranded; after stranding, a filler is wrapped around the surface of the stranded structure to form a primary structural wire. Step S3 includes: Step S3.1: Based on the total number and diameter of the primary structural lines in the secondary structural lines determined in step S1, twist multiple primary structural lines together and then cover them with filler material for the second time to obtain the secondary structural lines; Step S3.2: Based on the total number and diameter of the secondary structural lines in the tertiary structural line determined in step S1, twist multiple secondary structural lines together and cover them with filler for the third time to obtain the tertiary structural line; After three layers of filling material application in steps S2, S3.1, and S3.2, the total filling material amount meets the total filling material amount of the wire structure determined in step S1.

2. The method for preparing a wire structure based on filler and multiple stranded Litz wire according to claim 1, characterized in that, In step S3.1: the primary structure wire obtained in step S2 is twisted together to obtain the secondary structure wire, and filler is added. If the filler in step S2 already meets the total filler amount of the wire structure in step S1, no more filler is added. In step S3.2: the secondary structure wires obtained in step S3.1 are twisted together to obtain tertiary structure wires, and filler is added. If the filler in step S3.1 already meets the total filler amount of the wire structure in step S1, no more filler is added.

3. A megahertz wire structure based on filler and multiple stranded Litz wire, characterized in that, The novel high-frequency megahertz wire structure, obtained by the method of fabrication based on filler and multiple stranded Litz wire according to claim 1 or 2, has the performance of suppressing the proximity effect and skin effect of current at high frequencies and reducing loss and internal resistance in the megahertz band.

4. The megahertz wire structure based on filler and multiple stranded Litz wire according to claim 3, characterized in that, The wire structure is formed by multiple fine copper wires twisted together in multiple stages. The fine copper wires are evenly and symmetrically arranged in space, and there is a non-conductive filler between each fine copper wire.

5. The megahertz wire structure based on filler and multiple stranded Litz wire according to claim 3, characterized in that, The fine copper wire is pre-coated with filler by increasing the enamel thickness or coating it with a non-conductive material.

6. The megahertz wire structure based on filler and multiple stranded Litz wire according to claim 3, characterized in that, The wire structure is used to wind a megahertz coil.

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