RU2079915C1 - Method of manufacture of magnetic cores - Google Patents

Abstract

FIELD: electrical engineering, manufacture of transformer magnetic systems; in high-frequency transformers with magnetic cores of amorphous magnetically soft and microcrystalline alloys characterized by low hysteresis and eddy-current losses. SUBSTANCE: the method consists in winding of magnetic core from band, annealing, coating with synthetic resin, hardening, cutting, and mechanical lapping of magnetic core end faces in a mandrel. Annealing is carried out in conditions providing for the initial stage of embrittlement of magnetic core material for time period τ_ann.≥ τ_emb. at temperature T_ann.< T_cr., where: τ_ann. 0 annealing time, s; τ_emb.-time of embrittlement of magnetic core material, s; T_ann. - annealing temperature, C; T_cr. - crystallization temperature of magnetic core material, C. EFFECT: enhanced quality of magnetic cores by increasing the level of their electromagnetic characteristics.

Description

 The invention relates to the field of electrical engineering, namely to the manufacture of magnetic systems of transformers, and can be used in high-frequency (f≅100 kHz) transformers when replaced by amorphous soft magnetic and microcrystalline alloys / AMMS /, characterized by low hysteresis and eddy currents, crystalline Permalloid class alloys, electrical steel, ferrites.

 At present, the technology for manufacturing toroidal magnetic cores from AMMS has been developed, and the available developments for twisted split / providing the necessary parameters of electromagnetic devices at high current multiples and technological advantages during assembly / [1, 2] do not allow achieving the expected effect mainly due to incomplete operational technological chain.

A known method of manufacturing a magnetic circuit, including winding from an amorphous alloy ribbon on a rectangular mandrel of an magnetic circuit, annealing, coating with a synthetic resin, curing the latter, pouring in the form of low-melting metal, cutting into two halves, heating to remove metal, avoids deformation of delamination of the material of the magnetic circuit. However, the complexity of adhering to and monitoring the total heat treatment mode (during annealing, metal casting, subsequent heating) does not allow approaching the required level of electromagnetic characteristics, and the lack of grinding of the ends makes it difficult to achieve sufficiently high characteristics, in particular magnetic permeability μ _n .

 The closest to the claimed technical essence and the achieved result is the known method [3] according to which the magnetic core is wound mainly from an amorphous soft magnetic alloy, annealed, applied synthetic resin, cured, cut the magnetic core and polished the ends of its parts. This method, as well as the method [2] does not provide the required level of electromagnetic characteristics of the magnetic circuit also due to the difficulty of observing the control of heat treatment modes.

 The aim of the present invention is to increase the level of electromagnetic characteristics of split magnetic cores, mainly from amorphous soft magnetic alloys, that is, to improve the quality of magnetic cores.

To achieve this goal in the known method, including winding the alloy ribbon, annealing, coating with synthetic resin, curing, cutting and mechanical grinding of the ends in the clamping equipment according to this invention, annealing is carried out in the mode of providing the initial stage of embrittlement of the magnetic core material during the annealing time τ _{annealing .} ≥ τ _ocr. at T _ann. <T _cr .

The required values of the surface cleanliness of the ends and the thickness of the gap are achieved by the operation of mechanical grinding of the ends. Given the high hardness of AMMS before annealing, for high-speed cutting and grinding without heating the material / leading to crystallization and a sharp deterioration in electromagnetic characteristics /, annealing is necessary before carrying out these operations before the initial embrittlement stage. In the case of τ _ot. <τ _guard the sections of the magnetic circuit are heated above the crystallization temperature T _cr. . It should be noted that heating to temperatures close to the crystallization temperature T _cr. , at the same time leads to strong embrittlement of the material, which, in turn, does not allow, due to partial destruction, to approach the required surface quality of the ends.

 Embrittlement, as well as the level of electromagnetic characteristics, is determined by the passage of structural relaxation, which is an activation process. The embrittlement time at the selected annealing temperature can be determined using the effective activation energy of the corresponding structural relaxation process from the peak by DSC differential scanning calorimetry [4, 6] / low-temperature part of the relaxation spectrum /.

For alloy: 7421
τ _ocher. = 2.35 • 10 ^-12 • exp (174000 / PT) (SI)
For alloy 9KSR [6]
τ _ocher. = 2.3 • 10 ^-12 exp (170000 / PT)
P gas constant.

Crystallization temperature T _cr. for each alloy is indicated in the AMMS catalog [5]
For alloy 7421 T _cr. 510 ± 10 ^o C
for alloy 9KSR T _cr. 550 ± 10 ^o C
Thus, the invention is as follows. Sufficiently high values of a number of electromagnetic characteristics of composite (U-shaped) magnetic cores, in particular the initial magnetic permeability M _n , are determined by the surface quality of the ends and the size of the gap.

The joint use of the annealing modes of the magnetic cores to the initial stage of embrittlement provides a cutting operation without heating above the crystallization temperature T _cr. . The grinding operation of the ends of the magnetic circuit ensures the quality of the surface of the ends and the size of the gap, which provides increased values of the initial magnetic permeability μ _n .

Cutting without annealing or during annealing above crystallization temperature N _cr. leads to increased values of specific losses P _beats. , and without grinding the ends lower values of the initial magnetic permeability μ _n .

 The proposed method was carried out as follows.

 Example 1

A ribbon core of 8 mm wide with an active cross-section area S _A ≃ 0.1 cm ² with a one-sided silicate coating is wound from a 7421 alloy tape with a thickness of 25 μm on a rectangular mandrel.

Heat treatment in clamping equipment was carried out according to the cyclogram [6]
heating to 400 ^o C at a speed of 15 deg / min,
cooling to 200 ^o C at a speed of 20 deg / min,
further cooling at a speed of 5 deg / min.

 After heat treatment, a synthetic resin / ED-5 / was applied, and after the exposure necessary for curing, mechanical cutting into U-shaped parts on a cutting machine with abrasive disks was carried out, followed by mechanical grinding of the ends.

For a frequency f 10 kHz, the values of induction B _m 0.113 T were determined for a field strength H _m 117 A / m, magnetic permeability μ = 768, coercive force H _e 21.6 A / m, specific losses (P _beats ) / at B _m 9.6 W / kg, the coefficient of squareness of the hysteresis loop K _p 0,181.

Compound tests / of two U-shaped / magnetic circuits were carried out using the IPM-1 device / frequency 25, 50 kHz / with the determination of the level of specific losses and parameters of the static hysteresis loop
(P _beats ) 0.2 / 25 54 W / kg; B _m1 0.66 T; H _m1 560 A / m
(P _beats ) 0.1 / 50 36 W / kg; B _m2 1.18 T; H _m2 1650 A / m
Example 2

A ribbon core 10 mm wide with an active section area S _A S 0.38 cm ² with a one-sided coating of magnesium oxide was wound from a 9KSR alloy tape with a thickness of 25 μm on a rectangular mandrel.

Heat treatment in clamping equipment was carried out according to the sequence diagram: heating to 410 ^o C at a speed above 15 deg / min, cooling at a speed above 20 deg / min, to 200 ^o C, then above 5 deg / min. After heat treatment, cold-cured synthetic resin was applied, and after daily exposure, mechanical cutting with an abrasive disk into U-shaped parts was carried out, followed by grinding of the ends.

The tests of the composite core were also carried out at IMP-1/25 kHz / with determination of the level of specific losses / P _beats. / and parameters of the static hysteresis loop induction B _w and field strength H _w .

(P _beats ) _{0.2 / 25} 90 W / kg; B _m1 0.28 T; H _m1 110 A / m
(P _beats ) _{0.5 / 25} 380 W / kg; B _m2 1.1 T; H _m2 1100 A / m
In examples 1, 2 it is shown that the level of specific losses / P _beats. / at higher frequencies of the obtained composite magnetic circuits, it is close to that expected for toroidal samples without a cut, and in Example 2, the magnetic permeability μ _n / at 10 kHz /> 700 satisfies the requirements for the magnetic cores of transformers for diagnostic equipment.

The given examples confirm the receipt on the composite magnetic circuits of the level of characteristics (μ _n and P _beats ) necessary for small-sized transformers of power sources.

Thus, the effect achieved by the proposed method is to improve the surface quality of the ends of the magnetic circuit with a minimum / adjustable / thickness of the gap and, accordingly, increased values of electromagnetic characteristics, in particular μ _n / example 2 / and P _beats. , while the known methods do not take into account the degree of embrittlement of the material during heat treatment, as a result of which the required level of electromagnetic devices for diagnosing and tracking damage to insulation coatings and cable networks is not achieved, the initial magnetic permeability μ _n ≥ 700 was obtained.

Claims (1)

A method of manufacturing magnetic cores mainly from amorphous soft magnetic alloys, including the operations of winding, annealing, applying synthetic resin, curing, cutting and grinding the ends of the parts of the magnetic circuit, characterized in that the annealing is carried out in the mode of providing the initial stage of embrittlement of the material of the magnetic circuit for a time τ _anh ≥ τ _{ocher .} at a temperature T _{of T w} <T _cr where τ _ann - - annealing time, s; τ _ocher - the time of embrittlement of the material of the magnetic circuit, s; T _{o t w} annealing temperature, ^o C; T _{to p} - the crystallization temperature of the material of the magnetic circuit, ^o C.