Design method of single-phase winding composite iron core

Abstract

The invention relates to a design method of a single-phase winding composite iron core, which comprises the following steps of: winding an iron-cobalt soft magnetic alloy belt and an ultra-thin oriented silicon steel belt to form an inner side iron core, winding the ultra-thin silicon steel belt on the outer side to form a core design of a composite structure, and matching with a specific annealing and insulating treatment process. The prepared composite iron core is excellent in comprehensive performance, wherein the saturation flux density can reach 21000 Gs at most and is improved by about 30% compared with a traditional silicon steel iron core; in a typical working interval, the iron core loss can be reduced by 10-30% compared with that of a single ferrocobalt alloy; meanwhile, the consumption of expensive cobalt elements is effectively reduced, the cost is remarkably reduced, the overall mechanical strength of the iron core and the reliability of resisting environmental stress impact are enhanced through the composite structure, and the method is particularly suitable for the fields such as aviation transformers with strict requirements for the size, the weight, the performance 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 single-phase winding composite core. BACKGROUND

[0002] In the field of aviation, aerospace and special power supply, intermediate frequency (such as 400Hz) power transformer is often used. Since it cannot directly use the power frequency power grid for power supply, it needs to rely on independent generator set, so it puts forward extremely strict requirements on the volume, weight and efficiency of the transformer. One of the key ways to realize the miniaturization and light weight of the transformer is to use core material with high saturation magnetic induction strength (Bs) to reduce the cross-sectional area of the core and reduce the amount of copper used in the winding.

[0003] At present, the core of the 400Hz transformer mainly uses high magnetic induction oriented silicon steel (such as SJ 1761 recommended), and its typical saturation magnetic induction strength is about 1.5T (15000Gs). Although such material has mature technology and relatively controllable cost, its magnetic performance has reached the theoretical limit of traditional silicon steel, and it is difficult to meet the higher requirements of power density in application scenarios.

[0004] Ferrocobalt soft magnetic alloy (such as 1J22) is the soft magnetic material with the highest saturation magnetic induction strength (Bs can reach more than 2.4T) known at present. Using this material can significantly reduce the volume and weight of the core, and it is an ideal choice to realize the extreme miniaturization of the transformer. However, this material has three outstanding shortcomings: first, as a strategic rare metal, cobalt is scarce, expensive and unstable in supply, resulting in high cost of core manufacturing; second, the material itself has significant brittleness, and is easy to produce microcracks or breakage due to stress impact during winding processing and subsequent use, with poor structural reliability; third, under high frequency working conditions, its core loss (iron loss) is relatively high, which restricts its application in high efficiency systems.

[0005] Therefore, there is an urgent need in the art for a new core design and manufacturing method that can effectively overcome the defects of high cost, high brittleness and high frequency loss of single ferrocobalt soft magnetic alloy while maintaining high saturation magnetic induction strength. SUMMARY

[0006] To solve the above technical problems, the present application provides a design method of single-phase winding composite core, comprising the following steps:

[0007] Winding forming: winding the ferrocobalt soft magnetic alloy strip to form an inner core blank, and then winding the extremely thin oriented silicon steel strip outside the inner core blank to form an outer core blank, thereby forming a composite core structure; and

[0008] Annealing treatment: annealing the composite core structure to eliminate internal stress and optimize magnetic properties.

[0009] In one embodiment of the present application, the thickness of the extremely thin oriented silicon steel strip is 0.1 mm, and the thickness of the iron-cobalt soft magnetic alloy strip is 0.2 mm.

[0010] In one embodiment of the present application, when the extremely thin oriented silicon steel strip is wound, the winding tension is controlled to be 30-50 N, the winding speed is 10-15 m / min, the interlayer gap is ≤0.5 μm, and the lamination coefficient is greater than 0.88.

[0011] In one embodiment of the present application, the annealing process adopts a unified annealing process: heating at a rate of 50-100 ℃ / h to 800-850 ℃, holding for 3-6 hours under nitrogen protection, then cooling at a rate of 50-100 ℃ / h to 750 ℃, and finally cooling at a rate of 180-240 ℃ / h to 300 ℃ before discharging.

[0012] In one embodiment of the present application, the annealing process adopts a split annealing process, i.e. any one of the processes is selected according to different considerations of product performance and production cost to achieve the purpose of the application. Specifically, it includes:

[0013] The inner side core blank of the iron-cobalt soft magnetic alloy strip wound and formed is annealed: heating at a rate of 50-100 ℃ / h to 850-900 ℃, holding for 4 hours under nitrogen protection, then cooling at a rate of 50 ℃ / h to 750 ℃ and holding for 3 hours, applying a direct current magnetic field of 1200-1600 A / m at this stage, and finally cooling at a rate of 200 ℃ / h to 300 ℃ before discharging;

[0014] The outer side core blank of the extremely thin oriented silicon steel strip wound and formed is annealed: heating at a rate of 50-100 ℃ / h to 800-850 ℃, holding for 3-6 hours under nitrogen protection, then cooling at a rate of 50-100 ℃ / h to 750 ℃, and finally cooling at a rate of 180-240 ℃ / h to 300 ℃ before discharging.

[0015] In one embodiment of the present application, after the winding and forming and before the annealing process, it further includes fixing and shaping: the wound and formed core blank is fixed by winding with insulating tape, and the size accuracy is corrected by using a shaping die.

[0016] In one embodiment of the present application, after the annealing process step, it further includes:

[0017] Insulation treatment: coating epoxy resin insulating paint on the surface of the core and curing at 120 ℃ for 2 hours, so that the radial compressive strength of the final composite core is ≥5 MPa;

[0018] Detection and finishing: the core is detected in size and magnetic performance, and the core is cut into two halves according to the assembly requirement, and the cutting end face is protected by film.

[0019] The above technical scheme of the present application has the following advantages compared with the prior art: the design method of the present application, by placing the iron-cobalt soft magnetic alloy on the inner side and the extremely thin oriented silicon steel on the outer side of the unique composite structure, and cooperating with the optimized annealing process, realizes the synergistic improvement of multiple technical advantages: while maintaining high saturation magnetic induction (Bs up to 21000Gs), the middle section iron loss is effectively reduced by 10-30%; the use of expensive strategic metal cobalt is significantly reduced, and the manufacturing cost is significantly reduced; and the mechanical strength and impact resistance of the core as a whole are enhanced through structural composite, overcoming the inherent brittleness of single iron-cobalt material, and being particularly suitable for aerospace and other fields with extremely high requirements for volume, weight and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings.

[0021] Figure 1 is a schematic view of the cut structure of the single-phase wound composite core in the present application;

[0022] Figure 2 is a 400Hz core loss comparison chart in the present application. DETAILED DESCRIPTION

[0023] The present embodiment provides a design method of a single-phase wound composite core, which is described in detail as follows. 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:

[0024] 1. Strip pretreatment

[0025] Select an extremely thin oriented silicon steel strip (GT-100) with a thickness of 0.1mm and an iron-cobalt soft magnetic alloy strip (1J22) with a thickness of 0.2mm as raw materials. First, according to the size requirements of the target core, the two kinds of strips are cut into specific width coils, and pretreatment work such as removing dirt and cleaning impurities is carried out.

[0026] 2. Winding forming

[0027] Winding forming is one of the core steps of the present application, and the specific operation is as follows:

[0028] First, the pretreated iron-cobalt 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 around the center axis to form a rectangular inner core blank.

[0029] Next, a pre-treated ultra-thin oriented silicon steel strip is wound around the outer side of the already formed inner iron-cobalt alloy blank to form an outer core blank, thus constituting a complete composite core structure. During the winding of the silicon steel strip, the winding tension is stably controlled between 30N and 50N, and the winding speed is controlled between 10 and 15 m / min to ensure that the interlayer gap of the strip is ≤0.5μm and the lamination factor is controlled to be greater than 0.88.

[0030] 3. Fixation and Shaping

[0031] After winding, insulating tape is used to wrap and fix the composite iron core blank to prevent it from loosening. Subsequently, the dimensional accuracy (such as roundness and flatness) of the iron core is corrected by forming molds or pressure equipment to ensure that it meets the final design standards.

[0032] 4. Annealing treatment

[0033] This embodiment provides two optional annealing schemes, both of which can effectively eliminate internal stress and optimize magnetic properties:

[0034] Option 1: Standardize the annealing process

[0035] The shaped composite iron core is placed in an annealing furnace for uniform annealing. The specific process involves heating the core at a rate of 50-100℃ / h to 800-850℃, holding it at this temperature for 3-6 hours under nitrogen protection; then cooling it to 750℃ at a rate of 50-100℃ / h, and finally cooling it to 300℃ at a rate of 180-240℃ / h before removing it from the furnace. This method is simple and highly efficient.

[0036] Option 2: Separate annealing process (to obtain optimal magnetic properties)

[0037] This method requires annealing the inner blank of the iron-cobalt alloy and the outer blank of the silicon steel separately.

[0038] Annealing of the inner blank of iron-cobalt soft magnetic alloy (1J22): Heat to 850-900℃ at a rate of 50-100℃ / h, under nitrogen protection, and hold for 4 hours; then cool to 750℃ at a rate of 50℃ / h and hold at this temperature for 3 hours, starting from the 750℃ holding stage, apply a DC magnetic field of 1200-1600A / m; finally, cool to 300℃ at a rate of 200℃ / h and remove from the furnace.

[0039] Annealing of the outer blank of ultra-thin oriented silicon steel (GT-100): proceed according to the curve of scheme one, that is, heat to 800-850℃ at 50-100℃ / h, hold for 3-6 hours, and then cool to 300℃ at the corresponding cooling rate before taking it out of the furnace.

[0040] After both are annealed, they are reassembled, fixed, and shaped.

[0041] 5. Insulation treatment

[0042] After annealing and cooling, the iron core requires insulation treatment. Epoxy resin insulating varnish is applied to its surface and interlayer, followed by drying and curing at 120℃ for 2 hours. This process not only prevents excessive eddy current losses during use but also strengthens the core, ultimately achieving a radial compressive strength ≥5MPa.

[0043] 6. Inspection and finishing

[0044] Finally, the insulated iron core undergoes rigorous dimensional measurements and magnetic performance tests (such as iron loss and permeability). After selecting qualified products, if necessary, some iron cores may be cut into upper and lower halves to facilitate coil assembly according to assembly requirements. Figure 1 Each piece of material should be individually and clearly marked. After cutting, the cut surfaces must be immediately protected with a protective film to prevent oxidation and rust.

[0045] The design method and performance effects described in this embodiment are as follows: Figure 2 And as shown in the table below:

[0046]

[0047] The single-phase wound composite iron core prepared by the method in this embodiment has achieved the expected performance after testing.

[0048] The saturation magnetic induction intensity (Bs) can reach up to 21,000 Gs, which is significantly higher than that of traditional silicon steel cores.

[0049] Within the operating range where the magnetic flux density (B value) is less than 15000 Gs, the core loss is reduced by 10-30% compared to a single iron-cobalt alloy core.

[0050] While ensuring high performance, the amount of expensive cobalt used was reduced, thus lowering costs.

[0051] The composite structure effectively improves the brittleness of the single iron-cobalt alloy and enhances the structural reliability of the iron core under environmental stresses such as vibration and impact.

[0052] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A design method for a single-phase wound composite iron core, characterized in that, Includes the following steps: Winding: An iron-cobalt soft magnetic alloy strip is wound to form an inner core blank, and then an extremely thin grained silicon steel strip is directly wound around the outside of the inner core blank to form an outer core blank, thus forming a composite core structure; and Annealing treatment: The composite iron core structure is annealed to eliminate internal stress and optimize magnetic properties.

2. The design method according to claim 1, characterized in that: The thickness of the ultra-thin oriented silicon steel strip is 0.1 mm, and the thickness of the iron-cobalt soft magnetic alloy strip is 0.2 mm.

3. The design method according to claim 1, characterized in that: When winding the ultra-thin oriented silicon steel strip, the winding tension is controlled at 30N-50N, the winding speed is 10-15m / min, the interlayer gap is ≤0.5μm, and the stacking factor is greater than 0.

88.

4. The design method according to claim 1, characterized in that: The annealing process adopts a unified annealing process: the temperature is raised to 800-850℃ at a rate of 50-100℃ / h, held at this temperature for 3-6 hours under nitrogen protection, then cooled to 750℃ at a rate of 50-100℃ / h, and then cooled to 300℃ at a rate of 180-240℃ / h before being removed from the furnace.

5. The design method according to claim 1, characterized in that: Annealing treatment or separate annealing process, specifically including: The inner core blank formed by winding the iron-cobalt soft magnetic alloy strip is annealed: the temperature is raised to 850-900℃ at a rate of 50-100℃ / h, held at that temperature for 4 hours under nitrogen protection, then cooled to 750℃ at a rate of 50℃ / h and held at that temperature for 3 hours. During this stage, a DC magnetic field of 1200-1600A / m is applied, and finally cooled to 300℃ at a rate of 200℃ / h before being taken out of the furnace. The outer core blank formed by winding the ultra-thin oriented silicon steel strip is annealed: the temperature is raised to 800-850℃ at a rate of 50-100℃ / h, held at that temperature for 3-6 hours under nitrogen protection, then cooled to 750℃ at a rate of 50-100℃ / h, and then cooled to 300℃ at a rate of 180-240℃ / h before being removed from the furnace.

6. The design method according to claim 1, characterized in that: After the winding and before the annealing process, the process also includes fixing and shaping: the wound iron core blank is wrapped and fixed with insulating tape, and its dimensional accuracy is corrected using a shaping mold.

7. The design method according to claim 1, characterized in that: Following the annealing step, the process further includes: Insulation treatment: Epoxy resin insulating varnish is coated on the surface of the iron core and cured at 120℃ for 2 hours to make the radial compressive strength of the final composite iron core ≥5MPa; Inspection and finishing: The core is inspected for size and magnetic properties, and then cut into two halves according to assembly requirements. The cut ends are then protected with a protective film.

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