Magnetic core, solid state transformer and method for manufacturing a magnetic core

Abstract

The application relates to the technical field of nanocrystalline magnetic cores, in particular to a magnetic core, a solid-state transformer and a preparation method of the magnetic core. The magnetic core comprises two cut magnetic cores, the cut magnetic core comprises at least two magnetic pieces, the at least two magnetic pieces are sequentially stacked from inside to outside along the thickness direction of the magnetic pieces, the adjacent two magnetic pieces are bonded to each other, and the end of the cut magnetic core has a cut surface. The number of first slits on the cut surface is less than or equal to 10, and the roughness of the cut surface is less than or equal to 0.02 mm. Therefore, the low loss and high lamination coefficient of the magnetic core are realized, and the high performance requirement of the solid-state transformer can be met.

Description

Technical Field

[0001] This application relates to the field of nanocrystalline magnetic core technology, and in particular to a magnetic core, a solid-state transformer, and a method for preparing the magnetic core. Background Technology

[0002] Solid-state transformers (SSTs), also known as power electronic transformers, are static electrical devices that integrate power electronic conversion technology and high-frequency power conversion technology. They are widely used in scenarios with high power density and high efficiency requirements, such as AI data center power supply, new energy grid connection, and smart distribution networks.

[0003] The high-frequency transformers inside solid-state transformers use magnetic cores including ferrite cores and nanocrystalline alloy cores. Because the saturation magnetic induction intensity of ferrite cores is low, the core volume is large, and its permeability and temperature stability are insufficient, making it difficult to meet the requirements of high power density and low temperature rise of SST under high-frequency operating conditions. Therefore, nanocrystalline alloy cores are used in related technologies.

[0004] However, during the preparation of nanocrystalline alloy cores, processes such as cutting, winding, and heat treatment can easily lead to increased eddy current losses and decreased lamination factor, making them unsuitable for the high-performance requirements of solid-state transformers. Summary of the Invention

[0005] This application provides a magnetic core, a solid-state transformer, and a method for fabricating the magnetic core, achieving low loss and high lamination factor in the magnetic core, which can be applied to the high-performance requirements of solid-state transformers.

[0006] In the first aspect, the magnetic core provided in this application includes two cut magnetic cores, each cut magnetic core including at least two magnetic elements, the at least two magnetic elements being stacked sequentially from the inside to the outside along the thickness direction of the magnetic elements, two adjacent magnetic elements being bonded to each other, and the ends of the cut magnetic core having cut surfaces.

[0007] The number of first slits on the cut surface is less than or equal to 10, and the roughness of the cut surface is less than or equal to 0.02 mm.

[0008] In one possible implementation, the magnetic core provided in this application has a first gap whose depth direction is consistent with the length direction of the magnetic element, and the depth of the first gap is less than or equal to 5% of the length of the magnetic element.

[0009] In one possible implementation, the magnetic core provided in this application has sidewalls cut along the width direction of the magnetic element, with a second gap on the sidewalls and a first distance between the cut surface and the sidewalls.

[0010] In one possible implementation, the magnetic core provided in this application has a first pitch greater than or equal to 5 millimeters.

[0011] And / or, the width of the second gap is less than or equal to 1 mm.

[0012] And / or, the second gap on one side of the wall has a second distance from the other side of the wall.

[0013] In one possible implementation, the magnetic core provided in this application has less than or equal to 5 adhesive protrusions per 1 cm² area on the cut surface.

[0014] In one possible implementation, the magnetic core provided in this application includes a first magnetic part and two second magnetic parts, the two second magnetic parts being disposed on the same side of the first magnetic part, and the opposite ends of the first magnetic part being connected to the two second magnetic parts respectively; the cutting surface is located at the end of the second magnetic part away from the first magnetic part.

[0015] In one possible implementation, the magnetic core provided in this application has a cut surface perpendicular to the length direction of the second magnetic part.

[0016] In one possible implementation, the magnetic core provided in this application has a rectangular cut surface.

[0017] In one possible implementation, the magnetic core provided in this application has a first magnetic part that transitions to two second magnetic parts via an arc.

[0018] In one possible implementation, the magnetic core provided in this application has an arc radius greater than or equal to 10 mm and less than or equal to 20 mm.

[0019] In one possible implementation, the magnetic core provided in this application has a first magnetic portion and a second magnetic portion that are perpendicular to each other.

[0020] In one possible implementation, the magnetic core provided in this application is made of an iron-based nanocrystalline alloy.

[0021] In one possible implementation, the magnetic core provided in this application, when cut, further includes an adhesive layer, which is used to bond two adjacent magnetic components.

[0022] In one possible implementation, the magnetic core provided in this application has a resin layer as the adhesive layer.

[0023] Secondly, this application also provides a solid-state transformer, including any of the magnetic cores provided in the first aspect above.

[0024] Thirdly, this application also provides a method for preparing a magnetic core, used to prepare any of the magnetic cores provided in the first aspect above, the method for preparing the magnetic core includes:

[0025] The magnetic strip is wound from the inside out, and adjacent layers of the wound magnetic strip are bonded together to form a magnet.

[0026] The magnet is cut to form a cut magnetic core. The cut magnetic strip forms at least two magnetic elements stacked sequentially from the inside to the outside along the thickness direction. The two adjacent magnetic elements are bonded to each other. The cutting position of the cut magnetic core forms a cut surface. The number of first gaps on the cut surface is less than or equal to 10, and the roughness of the cut surface is less than or equal to 0.02 mm.

[0027] In one possible implementation, the method for preparing the magnetic core provided in this application, after winding the magnetic strip from the inside out, further includes:

[0028] The wound magnetic strip is subjected to crystallization annealing.

[0029] In one possible implementation, the method for preparing the magnetic core provided in this application involves bonding two adjacent layers of a wound magnetic strip together to form a magnet, comprising:

[0030] The wound magnetic strip is impregnated with resin so that the resin penetrates into the gaps between the two adjacent layers of the magnetic strip.

[0031] The resin is cured so that the cured resin bonds adjacent layers of the magnetic strip together to form a magnet.

[0032] In one possible implementation, the method for preparing the magnetic core provided in this application, after cutting the magnet to form a cut magnetic core, further includes:

[0033] The cut magnetic core is acid-washed.

[0034] The cut surfaces of the acid-washed magnetic cores are polished to ensure that the number of first slits on the cut surfaces is less than or equal to 10 and the surface roughness is less than or equal to 0.02 mm.

[0035] This application provides a magnetic core, a solid-state transformer, and a method for manufacturing the magnetic core. The magnetic core includes two cut magnetic cores. The cut magnetic core is provided with at least two magnetic elements, which are stacked sequentially from the inside to the outside along the thickness direction of the magnetic elements. Adjacent magnetic elements are bonded to each other. The ends of the cut magnetic cores have cut surfaces.

[0036] A surface roughness of less than or equal to 0.02 mm reduces eddy current loss sources; a first slit on the surface of less than or equal to 10 increases the lamination factor and magnetic circuit utilization. This achieves low core loss and a high lamination factor, making it suitable for the high-performance requirements of solid-state transformers. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the magnetic core structure provided in an embodiment of this application;

[0039] Figure 2 for Figure 1 Schematic diagram of the structure of the cut magnetic core;

[0040] Figure 3 for Figure 2 Top view;

[0041] Figure 4 for Figure 2 Side view;

[0042] Figure 5 for Figure 2 A schematic diagram of the structure of the magnetic component.

[0043] Explanation of reference numerals in the attached figures:

[0044] 100-cut magnetic core;

[0045] 101-First magnetic part; 102-Second magnetic part; 103-Cut surface; 1031-First gap; 1032-Adhesive protrusion; 104-Side wall surface; 1041-Second gap;

[0046] 110 - Magnetic component; 111 - First magnetic segment; 112 - Second magnetic segment;

[0047] 120 - Adhesive layer.

[0048] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0049] First, those skilled in the art should understand that these embodiments are merely for explaining the technical principles of this application and are not intended to limit the scope of protection of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0050] Secondly, it should be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0051] Furthermore, it should be noted that in the description of this application, the terms "upper," "lower," "front," "back," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0053] As illustrated in the background section, in related technologies, the high-frequency transformer inside a solid-state transformer uses a nanocrystalline alloy core. However, during the fabrication of the nanocrystalline alloy core, the cutting process easily generates burrs, microcracks, and deformation on the cut surface, leading to localized short circuits and increased eddy current losses in the nanocrystalline alloy core. The nanocrystalline core is composed of multiple layers of strip wound together. After heat treatment, the inconsistent lengths of the inner and outer layers cause uneven shrinkage of the strips due to thermal expansion and contraction, resulting in gaps between the layers. These gaps reduce the effective magnetic conductive area and decrease the lamination factor. Therefore, it is difficult to meet the high-performance requirements of solid-state transformers.

[0054] Based on this, the magnetic core, solid-state transformer and the method for preparing the magnetic core provided in this application include two cut magnetic cores. The cut magnetic cores are provided with at least two magnetic elements, which are stacked sequentially from the inside to the outside along the thickness direction of the magnetic elements. Adjacent magnetic elements are bonded to each other, and the ends of the cut magnetic cores have cut surfaces.

[0055] A surface roughness of less than or equal to 0.02 mm reduces eddy current loss sources; a first slit on the surface of less than or equal to 10 increases the lamination factor and magnetic circuit utilization. This achieves low core loss and a high lamination factor, making it suitable for the high-performance requirements of solid-state transformers.

[0056] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0057] Reference Figures 1 to 5 As shown, the magnetic core provided in this application includes two cut magnetic cores 100. Each cut magnetic core 100 includes at least two magnetic elements 110. The at least two magnetic elements 110 are stacked sequentially from the inside to the outside along the thickness direction of the magnetic elements 110. Adjacent magnetic elements 110 are bonded to each other. The end of the cut magnetic core 100 has a cut surface 103.

[0058] The number of first slits 1031 on the cutting surface 103 is less than or equal to 10, and the roughness of the cutting surface 103 is less than or equal to 0.02 mm.

[0059] It should be noted that the thickness direction of the magnetic component 110, i.e. Figure 2 The X direction is indicated by the middle arrow.

[0060] Understandably, at least two magnetic elements 110 are stacked to form a magnetic circuit and carry magnetic flux transmission under high-frequency operating conditions. In one possible embodiment, the magnetic element 110 may be a soft magnetic alloy sheet, a surface-treated magnetic element material, or other magnetic element material suitable for forming a magnetic circuit; in another possible embodiment, the magnetic element 110 may be a rectangular sheet, an annular sheet, or an irregularly shaped sheet suitable for an open magnetic core structure; the number of magnetic elements 110 may be two, three, or more than three, and the embodiments of this application do not impose excessive limitations on this.

[0061] It should be noted that, referring to Figure 3 As shown, the first gap 1031 on the cut surface 103 refers to the visible gap (the width of the first gap 1031 is greater than or equal to 0.03 mm) located in the end face region formed by cutting the end of the magnetic core 100, caused by cutting damage, interlayer deviation, or bonding discontinuity. It is used to characterize the continuity of the cut surface 103 and the integrity of the end magnetic circuit. The first gap 1031 is distributed on the cut surface 103. By limiting the first gap 1031, the location of magnetic circuit interruption on the cut surface 103 can be reduced, the probability of interlayer magnetic flux crossing the gap can be reduced, and thus the local additional loss at the end can be reduced.

[0062] In one possible embodiment, the first gap 1031 may be an interlayer opening, a small notch, or an end discontinuity gap; in another possible embodiment, it may be a narrow groove caused by a cutting mark; and in yet another possible embodiment, it may be an end face gap formed by the shrinkage of the adhesive material.

[0063] The roughness of the cutting surface 103 refers to the average degree of surface undulation after the cutting surface 103 is processed. It is used to characterize the flatness of the cutting surface 103 and the cutting edge forming quality. The roughness of the cutting surface 103 is less than or equal to 0.02 mm, which can reduce the disturbance of local peaks to the magnetic field distribution.

[0064] The roughness of the cut surface 103 is affected by the sharpness of the cutting tool, the feed rate, the slitting pressure, and subsequent finishing processes. In one possible embodiment, a lower roughness cut surface 103 can be formed by precision slitting, grinding, or polishing. In another possible embodiment, the cut surface 103 can be a basically flat mechanically cut surface, a slightly textured finished surface, or a composite plane after pressing. In yet another possible embodiment, the width of the cut surface 103 is coordinated with the thickness of the magnetic component 110 layer to ensure consistent contact between the ends of each piece on the cut surface 103. By limiting the roughness of the cut surface 103, the equivalent effect of local air gaps at the ends can be reduced, and the additional losses when high-frequency magnetic flux passes through the cut surface 103 can be decreased.

[0065] Based on the above analysis, it can be seen that the magnetic core provided in this application maintains a stacked fit of at least two magnetic components 110 under the constraint of mutual adhesion. Magnetic flux is established along the interior of each magnetic component 110 and completes magnetic circuit closure at the cut surface 103. Since the roughness of the cut surface 103 is less than or equal to 0.02 mm, eddy current loss sources can be reduced; the number of first gaps 1031 on the cut surface 103 is less than or equal to 10, which can improve the lamination factor and magnetic circuit utilization. Thus, the magnetic core achieves low loss, high permeability, and high lamination factor under high-frequency operating conditions, suitable for the high-performance requirements of solid-state transformers.

[0066] In some embodiments, refer to Figure 2 and Figure 3 As shown, the depth direction of the first gap 1031 is consistent with the length direction of the magnetic component 110, and the depth of the first gap 1031 is less than or equal to 5% of the length of the magnetic component 110.

[0067] This configuration allows the damage layer and crack propagation range at the end of the cut surface 103 to be controlled at a shallow level, reducing the disruption of the continuity of the main magnetic circuit by the first gap 1031 and avoiding excessive local magnetic reluctance abrupt changes.

[0068] Furthermore, limiting the depth of the first gap 1031 can reduce stress concentration and burrs on the cut surface 103, shorten the interlayer additional eddy current path, reduce heat accumulation and magnetic field distortion in the edge region, further improve the stacking utilization rate and reduce high-frequency loss.

[0069] For example, the depth of the first slit 1031 may be 5%, 4%, 3%, 2%, 1%, etc., of the length of the magnetic element 110.

[0070] In some embodiments, refer to Figure 2 , Figure 3 and Figure 4 As shown, along the width direction of the magnetic component 110, the cutting magnetic core 100 has sidewalls 104 on opposite sides, and there is a first gap between the second slit 1041 on the sidewalls 104 and the cutting surface 103.

[0071] It should be noted that the width direction of the magnetic component 110, i.e. Figure 4 The middle arrow indicates the Y direction.

[0072] Reference Figure 2 As shown, the second gap 1041 on the sidewall 104 refers to the gap formed on the two opposite sidewalls 104 of the magnetic core. The second gap 1041 has a first distance between it and the cut surface 103. Figure 2 As indicated by the middle arrow S1), the first spacing is used to define the positional relationship of the second slit 1041 on the sidewall surface 104 relative to the cut surface 103, so that the sidewall defect does not extend directly to the end magnetic circuit sensitive area.

[0073] Thus, the second gap 1041 maintains a first distance from the cutting surface 103, preventing local openings on the side wall 104 from forming a continuous weakening channel on the cutting surface 103, preventing defects on the side wall 104 from intruding into the sensitive magnetic area of ​​the cutting surface 103, and ensuring a stable distribution of magnetic flux in the area between the cutting surface 103 and the side wall 104.

[0074] In some embodiments, refer to Figure 2 As shown, the first spacing is greater than or equal to 5 millimeters.

[0075] It should be noted that the first distance between the second gap 1041 on the side wall 104 and the cut surface 103 ( Figure 2 The middle arrow indicates that S1) is greater than or equal to 5 mm, so that the second gap 1041 on the sidewall 104 maintains sufficient spatial separation from the local defect area on the cut surface 103, avoiding the formation of strong magnetic flux concentration by the magnetic field of the cut surface 103 crossing at least two defect areas in a very short distance, thereby helping to maintain the continuity of the magnetic circuit.

[0076] For example, the first distance between the second slit 1041 on the sidewall 104 and the cut surface 103 can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc.

[0077] In some embodiments, the width of the second gap 1041 is less than or equal to 1 mm.

[0078] It should be noted that the width of the second gap 1041 on the sidewall 104 is less than or equal to 1 mm, which can prevent a sharp increase in local magnetic reluctance, thus reducing the additional losses and temperature rise fluctuations caused by edge effects under high-frequency operating conditions. For example, the width of the second gap 1041 can be 1 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, 0.1 mm, etc.

[0079] In some embodiments, refer to Figure 4 As shown, there is a second gap 1041 on one side wall 104 and a second distance between the other side wall 104.

[0080] It should be noted that the second spacing ( Figure 4 The arrow S2 indicates the distance between the second gap 1041 set on one side wall 104 and the other side wall 104, which is used to characterize the spatial separation degree of the defect distribution on the two side walls 104 of the magnetic core.

[0081] This reduces the possibility of local defects on the sidewall 104 propagating or coupling to the opposite side, and avoids the magnetic flux distribution on both sides from overlapping due to local cracking, interlayer misalignment, or uneven bonding.

[0082] In some embodiments, refer to Figure 3 As shown, the number of adhesive protrusions 1032 per 1 cm² area of ​​the cut surface 103 is less than or equal to 5.

[0083] It should be noted that the adhesive protrusions 1032 on the cut surface 103 refer to the local protrusions formed by multiple magnetic components 110 at the cut surface 103 due to overflow of adhesive material, misalignment during pressing, or accumulation of residual material after cutting. The adhesive protrusions 1032 may be located at the edge of the cut surface 103, at the junction of layers, or at the location where adhesive material overflows. In one possible embodiment, its shape may be a small bulge formed by material covering, a step-like protrusion caused by misalignment of the ends of layers, or a burr-like residue formed by insufficient cutting trimming. In another possible embodiment, the adhesive protrusions 1032 may be removed by secondary trimming, scraping, or hot pressing. In yet another possible embodiment, the spatial distribution of the adhesive protrusions 1032 may be concentrated at the local edge or discretely distributed at multiple locations on the cut surface 103.

[0084] By limiting the number of adhesive protrusions 1032 per 1 cm² of the cut surface 103 to less than or equal to 5, the bonding state of the cut surface 103 can be kept relatively uniform, reducing local eddy current concentration.

[0085] In some embodiments, refer to Figure 2 and Figure 5 As shown, the cutting magnetic core 100 includes a first magnetic part 101 and two second magnetic parts 102. The two second magnetic parts 102 are disposed on the same side of the first magnetic part 101, and the two opposite ends of the first magnetic part 101 are respectively connected to the two second magnetic parts 102. The cutting surface 103 is located at the end of the second magnetic part 102 that is away from the first magnetic part 101.

[0086] In a specific implementation, the magnetic component 110 may include a first magnetic segment 111 and two second magnetic segments 112. The two second magnetic segments 112 are disposed on the same side of the first magnetic segment 111, and the two opposite ends of the first magnetic segment 111 are respectively connected to the two second magnetic segments 112. The first magnetic segments 111 of at least two magnetic components 110 together form a first magnetic part 101, and the second magnetic segments 112 of at least two magnetic components 110 together form a second magnetic part 102. The cutting surface 103 is located at the end of the second magnetic part 102 that is away from the first magnetic part 101.

[0087] The first magnetic segment 111 forms the main magnetic flux carrying area in the magnetic core, and the two second magnetic segments 112 form a branched extension structure on one side of the first magnetic segment 111, so that the single magnetic element 110 presents a three-segment shape with an open outline on the plane. After stacking, this structure allows the first magnetic segments 111 of multiple magnetic elements 110 to overlap at corresponding positions to form the first magnetic part 101, and the second magnetic segments 112 of multiple magnetic elements 110 to overlap on the other side to form the second magnetic part 102, thereby creating a clear partition between the main magnetic flux area and the branch magnetic flux area in the magnetic circuit. A cutting surface 103 is provided at one end of the second magnetic part 102 away from the first magnetic part 101, so that the cutting process can be uniformly performed at this end and the state of the cutting surface 103 can be controlled.

[0088] In one possible embodiment, the first magnetic segment 111 may be a straight strip, suitable as the main load-bearing segment of the magnetic core; in another possible embodiment, the first magnetic segment 111 may be an elongated structure with rounded corners to reduce stress concentration during stacking assembly. In one possible embodiment, the two second magnetic segments 112 may be parallel to each other.

[0089] For example, the magnetic component 110 may be an iron-based nanocrystalline alloy sheet, a soft magnetic ferrite sheet, or other high-permeability soft magnetic alloy strip, or a composite magnetic strip with a surface insulating coating as required by the working conditions.

[0090] In some embodiments, refer to Figure 2 As shown, the cut surface 103 is perpendicular to the length direction of the second magnetic part 102.

[0091] It should be noted that the length direction of the second magnetic part 102 is... Figure 2 The middle arrow indicates the Z direction.

[0092] This reduces the effective cross-sectional area loss caused by oblique cutting, and lowers the additional losses and temperature fluctuations caused by local magnetic field distortion, enabling the magnetic core to maintain more stable magnetic properties and higher stacking utilization under high-frequency operating conditions.

[0093] In some embodiments, refer to Figure 3 As shown, the cut surface 103 is rectangular.

[0094] Understandably, the rectangular outline allows the edges of each magnetic component 110 to be aligned along a uniform reference, thereby making the shape of the cut magnetic core 100 end regular and easy to match with the external magnetic circuit structure and assembly structure. Furthermore, the rectangular cut surface 103 can provide relatively uniform boundary conditions for magnetic flux to enter and leave the cut magnetic core 100, so that the magnetic flux can be continuously transmitted in the cut magnetic core 100.

[0095] In some embodiments, refer to Figure 2 and Figure 5 As shown, the first magnetic part 101 is connected to the two second magnetic parts 102 by a circular arc.

[0096] Specifically, the connection area between the first magnetic part 101 and the two second magnetic parts 102 disposed on the same side thereon adopts an arc-shaped transition structure, so that the connection is formed by a continuous curve rather than by a sharp corner or abrupt boundary.

[0097] In one possible embodiment, the arc transition can be an arc segment with a single radius. In another possible embodiment, it can be a composite arc transition segment formed by continuously splicing together at least two arcs with different radii. Specifically, it can be formed by die-cutting, laser cutting, precision stamping, or subsequent trimming. This application does not impose too many restrictions on this aspect.

[0098] In one possible embodiment, the cut magnetic core 100 is formed by stacking at least two magnetic elements 110 along the thickness direction of the magnetic elements 110. After cutting and shaping, the first magnetic segment 111 and the two second magnetic segments 112 of the magnetic elements 110 form an arc transition, so that each layer of magnetic elements 110 has a continuous curved connection interface in the corner area. In this way, after stacking and bonding, the magnetic circuit can smoothly turn when passing through the arc area, avoiding local magnetic flux congestion caused by sudden changes in magnetic resistance at sharp corners, and also reducing the impact of residual stress formed at the cutting edge in this part on the magnetic properties of the material.

[0099] In this way, the first magnetic part 101 is connected to the two second magnetic parts 102 by a circular arc, which can release the residual stress generated during the magnetic core manufacturing process, avoid the deterioration of magnetic properties caused by stress concentration, and ensure the high permeability of the magnetic core.

[0100] In some embodiments, refer to Figure 2 As shown, the radius of the arc is greater than or equal to 10 mm and less than or equal to 20 mm.

[0101] It should be noted that the radius of the arc is... Figure 2 The length of R is indicated by the middle arrow.

[0102] Experiments have verified that the volumetric loss Pcv exhibits a U-shaped trend, first decreasing and then increasing, with the change in arc radius. Specifically, the average volumetric loss Pcv is lowest at an arc radius of 15 mm (29.3 mW / cm³). At arc radii of 5 mm and 25 mm, the volumetric loss Pcv is 44.8 mW / cm³ and 42.7 mW / cm³, respectively, which are approximately 53% and 46% higher than the volumetric loss Pcv at an arc radius of 15 mm. At arc radii of 10 mm and 20 mm, the volumetric loss Pcv is 35.2 mW / cm³ and 34.7 mW / cm³, respectively, falling within the inflection point region. While the performance is acceptable, it is significantly inferior to that at an arc radius of 15 mm. At an arc radius of 15 mm, the residual stress generated by cutting and winding concentrates in the sharp corner region and cannot be effectively released. This stress concentration hinders the movement of magnetic domain walls in this region, resulting in a permeability of only 10²¹⁷. While a radius of 25mm effectively releases stress, it also reduces the effective magnetic circuit cross-sectional area, resulting in a lower lamination factor and a permeability of only 10033. Furthermore, an excessively large radius increases the longitudinal volume of the core, impacting assembly space. A radius of 15mm effectively releases residual stress while maximizing the preservation of the effective magnetic circuit cross-sectional area, achieving a permeability of 12350.

[0103] Understandably, the radius of the arc is between 10mm and 20mm, so that the arc can provide sufficient transition length to release stress, while avoiding the reduction of the effective cross-sectional area of ​​the magnetic circuit or the excessive size of the magnetic core due to an excessively large radius.

[0104] In this way, the transition region can be avoided from being too sharp and weakening the structural reliability, and the curvature can be avoided from being too gentle and occupying too much effective magnetic circuit space, so that the magnetic core can maintain structural compactness and assembly adaptability while maintaining high permeability and low loss.

[0105] For example, the radius of the arc can be 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, etc.

[0106] In some embodiments, refer to Figure 2 As shown, the first magnetic part 101 and the second magnetic part 102 are perpendicular to each other.

[0107] This configuration allows for a clear magnetic circuit direction, a more regular winding arrangement, and helps reduce local magnetic flux congestion and assembly interference, thereby improving the compatibility of the magnetic core with the external structure and its operational stability.

[0108] In some embodiments, refer to Figure 2 and Figure 5 As shown, the magnetic component 110 is made of an iron-based nanocrystalline alloy.

[0109] It should be noted that iron-based nanocrystalline alloys have good mechanical flexibility and high material utilization. The magnetic component 110 is made of iron-based nanocrystalline alloy, which can be more easily bonded and shaped during the stacking process. It can form a stable geometric relationship on the cut surface 103, side wall surface 104 and bonding interface, thereby reducing edge defects caused by material brittleness or processing deformation.

[0110] In some embodiments, refer to Figure 2 and Figure 3 As shown, the magnetic core provided in this application, the cut magnetic core 100 also includes an adhesive layer 120, which is used to bond two adjacent magnetic components 110.

[0111] In this way, two adjacent magnetic components 110 are bonded together by the adhesive layer 120. The adhesive layer 120 constrains the magnetic components 110, preventing them from separating, misaligning or warping at the ends, thereby improving the consistency of the finished magnetic core and its long-term operational stability.

[0112] In some embodiments, refer to Figure 2 and Figure 3 As shown, the adhesive layer 120 is a resin layer.

[0113] In practice, resin material can be pre-coated between two adjacent magnetic components 110, or the magnetic components 110 can be impregnated with resin material and then cured under pressure and temperature. The cured resin forms an adhesive layer 120 to reliably bond each layer of magnetic components 110 together.

[0114] Because the resin layer also has electrical insulation properties, the interlayer current is difficult to form a continuous closed loop, thereby suppressing the interlayer eddy current loss under high-frequency operating conditions. At the same time, after the resin layer is cured, it can limit the small displacement between the magnetic components 110, reduce the risk of interlayer loosening caused by vibration, thermal expansion and contraction or mechanical impact, and enable the magnetic core to maintain a relatively stable structural integrity under high-frequency switching conditions.

[0115] This application also provides a solid-state transformer, including a magnetic core.

[0116] Since this solid-state transformer uses the magnetic core described in the above embodiment, it also possesses the advantages and benefits associated with the magnetic core. Specifically, the roughness of the cut surface 103 of the cut magnetic core 100 is less than or equal to 0.02 mm, which reduces eddy current loss sources; the number of first slits 1031 on the cut surface 103 is less than or equal to 10, which improves the lamination factor and magnetic circuit utilization. Thus, low loss and high lamination factor of the magnetic core under high-frequency operating conditions are achieved, making it suitable for the high-performance requirements of solid-state transformers.

[0117] The specific structure and working method of the magnetic core have been described in detail in the above embodiments, and will not be repeated here.

[0118] This application also provides a method for preparing a magnetic core, the method comprising:

[0119] S101. The magnetic strip is wound from the inside out, and the adjacent layers of the wound magnetic strip are bonded together to form a magnet.

[0120] In practical implementation, the magnetic strip can be made of nanocrystalline alloy strip, iron-based amorphous alloy strip, or other soft magnetic material suitable for high-frequency transformers. The thickness, width, and length of the strip can be matched according to the magnetic circuit size of the target magnetic core to ensure that a continuous and stable magnetic flux path can be formed.

[0121] In this way, the magnetic strip is wound from the inside out, and the adjacent layers of the wound magnetic strip are bonded together. This integrates the magnetic strip wound from the inside out into a whole, which facilitates subsequent cutting and processing, and allows the magnet to maintain good structural stability during processing and use.

[0122] In some embodiments, refer to Figure 1 As shown, the magnet is ring-shaped, and the outer length of the magnet (i.e., Figure 1 The length of L1 (indicated by the middle arrow) can be 355mm, and the outer width of the magnet (i.e., Figure 1 The length of L2 (indicated by the middle arrow) can be 184 mm, and the inner length of the magnet (i.e. Figure 1 The length of L3 (as indicated by the middle arrow) can be 275 mm, and the inner width of the magnet (i.e. Figure 1 The length of L4 (as indicated by the middle arrow) can be 104 mm.

[0123] S102. The magnet is cut to form a cut magnetic core 100. The cut magnetic strip forms at least two magnetic elements 110 stacked sequentially from the inside to the outside along the thickness direction. The two adjacent magnetic elements 110 are bonded to each other. The cutting position of the cut magnetic core 100 forms a cutting surface 103. The number of first gaps 1031 on the cutting surface 103 is less than or equal to 10, and the roughness of the cutting surface 103 is less than or equal to 0.02 mm.

[0124] For example, the cutting method can be grinding, wire cutting, laser cutting, or other cutting methods suitable for processing soft magnetic materials. During cutting, the cutting path, cutting depth, and cutting speed are controlled so that the magnet is divided into cut magnetic cores 100 that meet the installation requirements, while forming a clear cutting surface 103 at the cutting position.

[0125] In this way, by cutting the magnet to form a cut magnetic core 100, the roughness of the cut surface 103 of the cut magnetic core 100 is less than or equal to 0.02 mm, which can reduce eddy current loss sources; the number of first gaps 1031 on the cut surface 103 is less than or equal to 10, which can improve the lamination factor and magnetic circuit utilization. Thus, low loss, high permeability and high lamination factor of the magnetic core under high frequency operating conditions are achieved, which is suitable for the high performance requirements of solid-state transformers.

[0126] In some embodiments, after winding the magnetic strip from the inside out, the method further includes:

[0127] The wound magnetic strip is subjected to crystallization annealing.

[0128] Specifically, the wound magnetic strip can be placed in an annealing apparatus for crystallization annealing. The annealing temperature and holding time can be set according to the material composition and thickness of the magnetic strip, so that the magnetic strip can complete the crystallization structure adjustment while maintaining the integrity of the sheet shape. After this treatment, the structural state of the surface and edges of the magnetic strip is more suitable for resin wetting and penetration, which can reduce local accumulation or void residue caused by uneven structure during subsequent impregnation.

[0129] In some embodiments, bonding adjacent layers of a wound magnetic strip together to form a magnet includes:

[0130] The wound magnetic strip is impregnated with resin so that the resin penetrates into the gaps between the two adjacent layers of the magnetic strip.

[0131] The resin is cured so that the cured resin bonds adjacent layers of the magnetic strip together to form a magnet.

[0132] Specifically, the wound magnetic strip is fed into the impregnation process, where liquid resin is used to ensure full contact with the surface of the magnetic strip. Under the action of capillary action and gravity, the resin penetrates into the gaps between the two adjacent layers of the magnetic strip and extends along the fine gaps to the area to be bonded, thereby forming a continuous resin distribution between the sheets.

[0133] During the curing process, the resin undergoes cross-linking and curing under set temperature or time conditions. The cured resin firmly connects two adjacent layers of the magnetic strip together, ultimately resulting in a magnet.

[0134] In this way, through resin impregnation and curing, the gaps between two adjacent layers of the magnetic strip can be uniformly filled by the resin, and the cured resin and the magnetic component 110 can form a stable bonding interface, thereby reducing local loose adhesion and void residue, and improving the overall bonding strength and structural consistency of the magnet.

[0135] In some embodiments, after cutting the magnet to form the cut magnetic core 100, the method further includes:

[0136] The cut magnetic core 100 is acid-washed.

[0137] The cut surface 103 of the acid-washed cut magnetic core 100 is polished so that the number of first gaps 1031 on the cut surface 103 is less than or equal to 10, the roughness of the cut surface 103 is less than or equal to 0.02mm, and the number of adhesive protrusions 1032 per 1cm² of the cut surface 103 is less than or equal to 5.

[0138] In practice, the cut magnetic core 100 can be placed in an acid pickling tank using a dilute acid pickling solution. The concentration, temperature, and soaking time of the solution are controlled to ensure that the pickling solution removes only the adhering impurities on the surface of the cut surface 103 without corroding the cut magnetic core 100. After pickling, the cut magnetic core 100 can be rinsed and dried to prevent residual acid from continuing to act on the cut surface 103 and to prevent corrosion products from re-adhering.

[0139] It should be noted that acid pickling of the cut magnetic core 100 can eliminate the oxide layer and surface contamination formed in the heat-affected zone of the cut, making the cut surface 103 more uniform and providing a stable foundation for subsequent grinding.

[0140] The cut surface 103 of the acid-washed cut magnetic core 100 is then polished. Polishing can be done using a grinding wheel, abrasive belt, or grinding disc, directionally trimming along the cut surface 103. By controlling the polishing pressure, feed rate, and removal amount, micro-protrusions, local chipping, and residual micro-unevennesses on the cut surface 103 are further removed, resulting in lower roughness and higher flatness for the cut surface 103. Because acid washing removes adhering impurities beforehand, it is less likely to press contaminants into the surface layer during polishing, thus making the trimming process more uniform and stable and reducing the risk of secondary damage.

[0141] In some embodiments, winding the magnetic strip from the inside out includes:

[0142] The thickness of the magnetic strip is greater than or equal to 10 μm and less than or equal to 22 μm.

[0143] It should also be noted that a magnetic strip thickness greater than or equal to 10 μm ensures the mechanical strength of the magnetic strip and guarantees the integrity of the magnetic core structure. Furthermore, since eddy current losses are proportional to the square of the magnetic strip thickness, a magnetic strip thickness less than or equal to 22 μm reduces eddy current losses.

[0144] For example, the thickness of the magnetic strip can be 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, etc.

[0145] Experiments have verified that the existing ferrite core has a volumetric loss Pcv of 120 mW / cm³ and a permeability of 2500. The existing nanocrystalline core has a cutting damage layer, resulting in high eddy current losses. Specifically, the roughness Ra of the cutting surface 103 of the existing nanocrystalline core is 0.05 mm, and there are 12 adhesion protrusions 1032 per 1 cm² of the cutting surface 103, resulting in a volumetric loss Pcv of 130 mW / cm³ and a stacking factor of 80%.

[0146] In some embodiments, iron-based nanocrystalline ribbon is used, and the process involves winding, crystallization annealing, vacuum impregnation curing, wire cutting (positioning accuracy ±0.02mm), pickling, and precision grinding of the end face (roughness Ra≤0.02mm). Six magnetic core samples of the same size were continuously prepared, and the test results are shown in the table below:

[0147]

[0148] Experimental results show that the roughness Ra of the cut surface 103 of the six magnetic core samples is 0.015~0.019mm, the number of adhesive protrusions 1032 per 1cm² of the cut surface 103 is 0~3, the volumetric loss Pcv is 22~35mW / cm³, the number of first gaps 1031 (width ≥0.03mm) of the cut surface 103 is 0~4, and the stacking factor is 87.5%~88.5%.

[0149] Thus, in response to the problems of high loss, low stacking factor, and poor quality of the cut surface 103 in existing nanocrystalline alloy magnetic cores, the magnetic core provided in this application achieves low loss, high permeability, and high stacking factor by optimizing the morphological characteristics.

[0150] In other embodiments, only the cutting method is changed to abrasive wheel cutting, while the rest of the process remains unchanged. Experimental verification shows that the roughness Ra of the cutting surface 103 obtained by abrasive wheel cutting is 0.020~0.024mm, the number of adhesion protrusions 1032 per 1cm² area of ​​the cutting surface 103 is 4~5, and the volumetric loss Pcv is 38~45mW / cm³ (average approximately 41.3mW / cm³), which is higher than that of wire cutting. The number of first slits 1031 (width ≥0.03mm) on the cutting surface 103 is 2~7, indicating that wire cutting is the preferred solution, but the performance of abrasive wheel cutting is also improved compared to existing nanocrystalline magnetic cores.

[0151] Those skilled in the art will understand that the magnetic core, solid-state transformer, and method for preparing the magnetic core provided in this application include two cut magnetic cores 100. The cut magnetic core 100 is provided with at least two magnetic elements 110. The at least two magnetic elements 110 are stacked sequentially from the inside to the outside along the thickness direction of the magnetic elements 110. Adjacent magnetic elements 110 are bonded to each other. The end of the cut magnetic core 100 has a cut surface 103.

[0152] The roughness of the cut surface 103 is less than or equal to 0.02 mm, which can reduce eddy current loss sources; the number of first slits 1031 on the cut surface 103 is less than or equal to 10, which can improve the lamination factor and magnetic circuit utilization. Thus, low loss and high lamination factor of the magnetic core are achieved, which can be used to meet the high performance requirements of solid-state transformers.

[0153] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0154] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application.

[0155] The technical solutions of this application have been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A magnetic core, characterized in that, include: Two cut magnetic cores (100) are provided, each comprising at least two magnetic elements (110). The at least two magnetic elements (110) are stacked sequentially from the inside to the outside along the thickness direction of the magnetic elements (110). Two adjacent magnetic elements (110) are bonded to each other. The ends of the cut magnetic cores (100) have cut surfaces (103). The number of first slits (1031) on the cut surface (103) is less than or equal to 10, and the roughness of the cut surface (103) is less than or equal to 0.02 mm.

2. The magnetic core according to claim 1, characterized in that, The depth direction of the first gap (1031) is consistent with the length direction of the magnetic element (110), and the depth of the first gap (1031) is less than or equal to 5% of the length of the magnetic element (110).

3. The magnetic core according to claim 1, characterized in that, Along the width direction of the magnetic element (110), the cutting magnetic core (100) has sidewalls (104) on opposite sides, and there is a first gap between the second gap (1041) on the sidewall (104) and the cutting surface (103).

4. The magnetic core according to claim 3, characterized in that, The first spacing is greater than or equal to 5 millimeters; And / or, the width of the second gap (1041) is less than or equal to 1 mm; And / or, the second gap (1041) on one of the sidewall surfaces (104) has a second spacing with the other sidewall surface (104).

5. The magnetic core according to claim 1, characterized in that, The number of adhesive protrusions (1032) per 1 cm² area of ​​the cut surface (103) is less than or equal to 5.

6. The magnetic core according to any one of claims 1 to 5, characterized in that, The cutting magnetic core (100) includes a first magnetic part (101) and two second magnetic parts (102). The two second magnetic parts (102) are disposed on the same side of the first magnetic part (101), and the opposite ends of the first magnetic part (101) are respectively connected to the two second magnetic parts (102). The cut surface (103) is located at the end of the second magnetic part (102) away from the first magnetic part (101).

7. The magnetic core according to claim 6, characterized in that, The cut surface (103) is perpendicular to the length direction of the second magnetic part (102).

8. The magnetic core according to claim 7, characterized in that, The cut surface (103) is rectangular.

9. The magnetic core according to claim 6, characterized in that, The first magnetic part (101) is connected to the two second magnetic parts (102) by a circular arc.

10. The magnetic core according to claim 9, characterized in that, The radius of the arc is greater than or equal to 10 mm and less than or equal to 20 mm.

11. The magnetic core according to claim 6, characterized in that, The first magnetic part (101) and the second magnetic part (102) are perpendicular to each other.

12. The magnetic core according to any one of claims 1 to 5, characterized in that, The magnetic component (110) is made of an iron-based nanocrystalline alloy.

13. The magnetic core according to any one of claims 1 to 5, characterized in that, The cut magnetic core (100) also includes an adhesive layer (120), which is used to bond two adjacent magnetic components (110).

14. The magnetic core according to claim 13, characterized in that, The adhesive layer (120) is a resin layer.

15. A solid-state transformer, characterized in that, Includes the magnetic core as described in any one of claims 1 to 14.

16. A method for preparing a magnetic core, characterized in that, The method for preparing the magnetic core according to any one of claims 1 to 14 comprises: The magnetic strip is wound from the inside out, and adjacent layers of the wound magnetic strip are bonded together to form a magnet. The magnet is cut to form a cut magnetic core (100). The cut magnetic strip forms at least two magnetic elements (110) stacked sequentially from the inside to the outside along the thickness direction. The two adjacent magnetic elements (110) are bonded to each other. The cut position of the cut magnetic core (100) forms a cut surface (103). The number of first gaps (1031) on the cut surface (103) is less than or equal to 10, and the roughness of the cut surface (103) is less than or equal to 0.02 mm.

17. The method for preparing a magnetic core according to claim 16, characterized in that, After winding the magnetic strip from the inside out, the process further includes: The wound magnetic strip is then subjected to crystallization annealing.

18. The method for preparing a magnetic core according to claim 16, characterized in that, The process of bonding adjacent layers of the wound magnetic strip together to form the magnet includes: The wound magnetic strip is impregnated with resin so that the resin penetrates into the gaps between two adjacent layers of the magnetic strip; The resin is cured so that the cured resin bonds adjacent layers of the magnetic strip together to form the magnet.

19. The method for preparing a magnetic core according to claim 16, characterized in that, After cutting the magnet to form a cut magnetic core (100), the process further includes: The cut magnetic core (100) is pickled; The cut surface (103) of the acid-washed cut magnetic core (100) is polished so that the number of first gaps (1031) on the cut surface (103) is less than or equal to 10, and the roughness of the cut surface (103) is less than or equal to 0.02 mm.

20. The method for preparing a magnetic core according to claim 16, characterized in that, The winding of the magnetic strip from the inside out includes: The thickness of the magnetic strip is greater than or equal to 10 μm and less than or equal to 22 μm.

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