Design method of three-phase winding composite iron core

Abstract

The invention relates to a three-phase winding composite iron core design method. According to the method, an iron-cobalt soft magnetic alloy strip and an ultra-thin oriented silicon steel strip are adopted as composite raw materials, the iron-cobalt soft magnetic alloy strip is wound to form an inner side blank of each column of the three-phase iron core, then the silicon steel strip wraps the inner side blank in a surrounding mode to form an outer side blank, and the total thickness of the inner side blank and the total thickness of the outer side blank are consistent. The preparation process comprises the steps of strip pretreatment, winding forming, fixed shaping, annealing treatment, insulation dipping and detection finish machining. According to the structure, the advantage of high saturation flux density (Bs can reach 21000 Gs) of the iron-cobalt alloy is maintained, meanwhile, iron loss under medium and low magnetic flux is effectively reduced, iron core brittleness is improved, mechanical strength and environmental reliability are improved, the consumption of cobalt materials is remarkably reduced, cost is reduced, and the structure is particularly suitable for the field of aviation medium-frequency transformers with strict requirements for the size, the weight and the reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer core, in particular to a design method of three-phase winding composite core. BACKGROUND

[0002] In the field of aviation, aerospace and other special applications, due to the inability to directly use the ground power grid, it is necessary to rely on independent generator sets to provide 400Hz medium frequency power supply. This puts forward extremely strict requirements for the lightweight and miniaturization of the power transformer used.

[0003] To achieve this goal, the industry generally uses core materials with high saturation magnetic induction (Bs). Increasing the Bs value means that the cross-sectional area of the core can be smaller under the same magnetic flux, thereby directly reducing the volume and weight of the core and correspondingly reducing the amount of wire used, ultimately achieving compact design of the transformer as a whole.

[0004] Currently, 400Hz three-phase winding cores mainly use the following two types of materials, but both have obvious limitations:

[0005] Traditional oriented silicon steel: The ordinary electrical steel core manufactured according to the current national standard (such as GB / T4596) has a saturation magnetic induction of about 15000Gs, which has become a technical bottleneck restricting the further reduction of transformer volume. Although very thin oriented silicon steel (such as 0.1mm specification) can improve high-frequency loss, its saturation magnetic induction (about 18000Gs) is limited and cannot meet the demand for higher power density.

[0006] Ferrocobalt soft magnetic alloy (such as 1J22): This material has extremely high saturation magnetic induction (up to more than 24000Gs), and has irreplaceable advantages in achieving ultra-miniaturization and lightweight of transformers. However, its application faces two major obstacles:

[0007] High material cost and supply risk: Cobalt is a strategic rare metal with concentrated global supply and high and volatile prices, resulting in extremely high manufacturing cost of ferrocobalt alloy core.

[0008] Poor mechanical processing performance: The ferrocobalt alloy material is brittle and prone to stress cracks during winding, shearing and other processing, resulting in low mechanical strength of the finished core and poor reliability in resisting environmental stress impact (such as vibration and impact), which restricts its widespread application in the aviation field with extremely high reliability requirements.

[0009] Therefore, there is an urgent need in the art for an innovative core design and manufacturing method that can effectively overcome the defects of high cost, brittleness and insufficient reliability of single ferrocobalt soft magnetic alloy core while retaining the advantage of high saturation magnetic induction. SUMMARY

[0010] To solve the above technical problems, the design method of the three-phase winding composite core of the present application aims to build a composite structure with three core columns, including the following steps:

[0011] Step S1: strip pretreatment; provide two kinds of strips as raw materials, i.e. extremely thin oriented silicon steel strip and iron-cobalt soft magnetic alloy strip; and pretreat the two kinds of strips, i.e. cut according to the core size and remove surface dirt and impurities;

[0012] Step S2: winding forming; wind to form three core columns of the three-phase core respectively; for each core column, first wind the pretreated iron-cobalt soft magnetic alloy strip to form a rectangular inner blank of the core column; then, wind the pretreated extremely thin oriented silicon steel strip around the outside of the inner blank to form an outer blank of the core column, and keep the total thickness of the inner and outer blanks consistent after forming;

[0013] Step S3: fixing and shaping; fix and shape the three core columns after winding forming to assemble into a complete three-phase core and ensure that the size accuracy meets the design requirements;

[0014] Step S4: annealing treatment; anneal the three-phase composite core after shaping to eliminate processing stress and optimize its magnetic properties;

[0015] Step S5: insulation treatment; insulate the three-phase composite core after annealing to enhance interlayer insulation and improve mechanical strength;

[0016] Step S6: detection and finishing; finally, detect and finish the three-phase composite core after insulation treatment to obtain qualified products.

[0017] In an embodiment of the present application, the extremely thin oriented silicon steel strip is GT-100 with a thickness of 0.1 mm; and the iron-cobalt soft magnetic alloy strip is 1J22 with a thickness of 0.2 mm.

[0018] In an embodiment of the present application, in the winding forming step, the winding tension of the extremely thin oriented silicon steel strip is controlled at 30-50 N, the winding speed is controlled at 10-15 m / min, the interlayer gap is ≤0.5 μm, and the lamination coefficient is greater than 0.88.

[0019] In an embodiment of the present application, the annealing treatment adopts any of the following methods:

[0020] Method one: heat to 800-850℃ at a speed of 50-100℃ / h under nitrogen protection, keep warm for 3-6 hours, then cool to 750℃ at a speed of 50-100℃ / h, and then cool to 300℃ at a speed of 180-240℃ / h and discharge;

[0021] Method two: heating to 850-900℃ at a rate of 50-100℃ / h under nitrogen protection, keeping for 4 hours, then cooling to 750℃ at a rate of 50℃ / h and keeping for 3 hours, and then cooling to 300℃ at a rate of 200℃ / h to discharge, and applying a direct current magnetic field of 1200-1600A / m at the beginning of keeping at 750℃.

[0022] In an embodiment of the present application, the insulation treatment adopts epoxy resin paint coating and curing at 120℃ for 2 hours, so that the radial compressive strength of the iron core is ≥5MPa.

[0023] In an embodiment of the present application, in the three-phase winding composite iron core, the magnetic properties of the left and right phases refer to the composite iron core data, and the magnetic properties of the middle phase refer to the iron-cobalt soft magnetic alloy iron core data.

[0024] The above technical scheme of the present application has the following advantages compared with the prior art: the three-phase winding composite iron core design method of the present application effectively reduces the iron loss under medium and low magnetic flux while maintaining the advantage of high saturation magnetic induction intensity (Bs up to 21000Gs) of iron-cobalt alloy, improves the brittleness of the iron core, improves the mechanical strength and environmental reliability, significantly reduces the amount of cobalt material, and reduces the cost, and is particularly suitable for the field of aviation medium-frequency transformers which have strict requirements on volume, weight and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the content of the present application easier to be clearly understood, the present application will be further described in detail below according to specific embodiments of the present application and in combination with the accompanying drawings.

[0026] Figure 1 is a schematic view of the structure of the three-phase winding composite iron core of the present application after cutting;

[0027] Figure 2 is a comparison chart of 400Hz iron core loss in the present application. DETAILED DESCRIPTION

[0028] The present embodiment provides a design method of a three-phase winding composite iron core, which is described in detail, and aims to prepare a three-phase winding composite iron core for a 400Hz aviation transformer. The present embodiment is only used to explain the present application and does not constitute a limitation on the protection scope of the present application; including:

[0029] 1. Strip pretreatment; select an extremely thin oriented silicon steel strip (model GT-100) with a thickness of 0.1mm and an iron-cobalt soft magnetic alloy strip (model 1J22) with a thickness of 0.2mm as raw materials. First, according to the size requirements of the target iron core, the two kinds of strips are cut into coiled materials with a specific width. Then, the strips are cleaned to remove the oil stains and impurities on the surface, preparing for winding forming.

[0030] 2. Winding forming; this step is the core of forming three-phase composite structure.

[0031] Firstly, the pretreated 1J22 Fe-Co soft magnetic alloy strip is fed into the winding machine, and through precise tension control and mold positioning, the strip is continuously and tightly wound to form the rectangular inner blank of three core columns.

[0032] Then, the pretreated GT-100 ultra-thin oriented silicon steel strip is continuously wound around the outer side of the 1J22 inner blank of each core column formed above, thereby forming the outer blank of three core columns. Ensure that the total thickness of the inner and outer blanks of each core column is consistent after forming.

[0033] During the winding of the silicon steel strip, the winding tension is stably controlled between 30N-50N, and the winding speed is controlled at 10-15m / min, to ensure that the interlayer gap of the strip is not greater than 0.5μm, and the lamination coefficient is controlled to be greater than 0.88.

[0034] 3. Fixing and shaping; after winding, the three independent core column blanks are wrapped and fixed using insulating tape to prevent them from loosening. Subsequently, through a shaping mold or pressure equipment, the overall dimensional accuracy of the core (such as the parallelism of each core column and the symmetry of the window) is corrected to ensure compliance with the design drawing standards.

[0035] 4. Annealing treatment; the three-phase composite core after shaping is placed in an annealing furnace for annealing treatment to eliminate internal stress and optimize magnetic properties. One of the two annealing schemes is adopted in this embodiment:

[0036] Scheme A (mixed annealing): heated to 800-850℃ at a heating rate of 50-100℃ / hour under nitrogen protection, and kept for 3-6 hours; then cooled to 750℃ at a rate of 50-100℃ / hour; finally, cooled to 300℃ at a rate of 180-240℃ / hour and discharged.

[0037] Scheme B (to obtain optimal magnetic properties): the silicon steel part and the Fe-Co alloy part are annealed separately. The GT-100 silicon steel blank is annealed according to scheme A; the 1J22 Fe-Co alloy blank is annealed according to the following process: heated to 850-900℃ at a rate of 50-100℃ / hour under nitrogen protection, and kept for 4 hours; then cooled to 750℃ at a rate of 50℃ / hour and kept for 3 hours, and a direct current magnetic field of 1200-1600A / m is applied during this 750℃ keeping stage; finally, cooled to 300℃ at a rate of 200℃ / hour and discharged. After annealing, the two parts are reassembled and fixed.

[0038] 5. Insulation treatment; after annealing and cooling, the surface and interlayer of the core are coated with insulation. The embodiment uses epoxy paint for dipping treatment and is baked and cured at 120°C for 2 hours. This treatment not only provides the necessary interlayer insulation to prevent eddy current loss, but also makes the final core radial compressive strength not less than 5MPa.

[0039] 6. Detection and finishing; finally, the three-phase composite core after insulation treatment is subjected to final size measurement and magnetic property test (such as iron loss, permeability), and the qualified products are screened out. According to the assembly needs, the core can be cut into two halves to facilitate the assembly of the coil, and the cutting end face is protected by film to prevent rusting.

[0040] The design method described in this embodiment has the following performance effects, such as Figure 2 and shown in the following table:

[0041]

[0042] And the three-phase wound composite core prepared by the method of this embodiment has the following properties:

[0043] The saturation magnetic induction (Bs) can reach up to 21000Gs, which is significantly improved compared with the traditional silicon steel core (about 15000Gs).

[0044] In the working range of magnetic induction (B value) less than 15000Gs, the core loss is reduced by 10-30% compared with single 1J22 iron-cobalt alloy core.

[0045] Due to the reduction of the amount of expensive 1J22 material, the manufacturing cost is effectively controlled.

[0046] The tough silicon steel layer on the outside improves the overall mechanical properties of the core and enhances the reliability of resisting environmental stress impact.

[0047] Obviously, the above embodiments are only examples for the sake of clarity, and are not limited to the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A design method of a three-phase wound composite core, the design method aiming to construct a composite structure having three core legs, characterized in that, It comprises the following steps: Step S1: strip pretreatment; providing two kinds of strips as raw materials, i.e. an extremely thin oriented silicon steel strip and a cobalt-iron soft magnetic alloy strip; and pretreating the two kinds of strips, i.e. cutting according to the size of the core and removing surface dirt and impurities; Step S2: winding forming; winding to form three core columns of the three-phase core respectively; for each core column, first winding the pretreated cobalt-iron soft magnetic alloy strip to form a rectangular inner blank of the core column; Subsequently, winding the pretreated extremely thin oriented silicon steel strip around the outside of the inner blank to form an outer blank of the core column, and keeping the total thickness of the inner and outer blanks consistent after forming; Step S3: fixing and shaping; fixing and shaping the three winding-formed core columns to assemble into a complete three-phase core and ensure that the size accuracy meets the design requirements; Step S4: annealing treatment; annealing the shaped three-phase composite core to eliminate processing stress and optimize its magnetic properties; Step S5: insulation treatment; insulating the annealed three-phase composite core to enhance interlayer insulation and improve mechanical strength; Step S6: detection and finishing; finally, detecting and finishing the insulating three-phase composite core to obtain qualified products.

2. The design method of a three-phase wound composite core according to claim 1, characterized by: The extremely thin oriented silicon steel strip is GT-100 with a thickness of 0.1 mm; and the cobalt-iron soft magnetic alloy strip is 1J22 with a thickness of 0.2 mm.

3. The design method of a three-phase wound composite core according to claim 1, characterized by: In the winding forming step, the winding tension of the extremely thin oriented silicon steel strip is controlled at 30-50 N, the winding speed is controlled at 10-15 m / min, the interlayer gap is ≤0.5 μm, and the lamination coefficient is greater than 0.

88.

4. The design method of a three-phase wound composite core according to claim 1, characterized by: The annealing treatment adopts any one of the following methods: Method one: heating to 800-850 ℃ at a speed of 50-100 ℃ / h under nitrogen protection, keeping for 3-6 hours, then cooling to 750 ℃ at a speed of 50-100 ℃ / h, and then cooling to 300 ℃ at a speed of 180-240 ℃ / h to discharge; Method two: heating to 850-900 ℃ at a speed of 50-100 ℃ / h under nitrogen protection, keeping for 4 hours, then cooling to 750 ℃ at a speed of 50 ℃ / h and keeping for 3 hours, and then cooling to 300 ℃ at a speed of 200 ℃ / h to discharge, and applying a direct-current magnetic field of 1200-1600 A / m at the beginning of keeping at 750 ℃.

5. The design method of a three-phase wound composite core according to claim 1, characterized by: The insulation treatment adopts epoxy resin paint coating and curing at 120 ℃ for 2 hours, so that the radial compressive strength of the core is ≥5 MPa.

6. The design method of a three-phase wound composite core according to claim 1, characterized by: In the three-phase winding composite core, the magnetic properties of the left and right phases refer to the composite core data, and the magnetic properties of the middle phase refer to the cobalt-iron soft magnetic alloy core data.

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