JPH0562444B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a magnetic core used in a transformer, a chiyoke coil, etc.

[Background technology]

Generally, in a laminated magnetic core made of soft magnetic metal with high magnetic permeability, the core loss during AC excitation, so-called iron loss, is divided into hysteresis loss Wh, general eddy current loss We, and abnormal eddy current loss Wa. The frequency characteristics are as shown in Figure 1, and the hysteresis loss W/h per cycle does not change even if the frequency fou changes, and both eddy current losses We and Wa increase as the frequency f increases. increase Note that the composition ratio of each loss Wh, We, and Wa varies greatly depending on the shape of the magnetic core material, such as the thickness, and the heat treatment conditions. By the way, the above general eddy current loss We is calculated by the following formula (1), where t is the thickness of the magnetic plate forming the laminated magnetic core, ρ is the electrical resistance, and Bm is the operating magnetic flux density. It is also called classical eddy current loss.

We=(πtfBm) ² /6ρW/cc...(1) On the other hand, the abnormal eddy current loss Wa is the eddy current loss that actually occurs and the general eddy current loss mentioned above.
This is the difference between We and this abnormal eddy current loss Wa
is strongly related to the magnetic domain structure and the number of domain walls,
If the plate thickness is t and the domain wall spacing is d, it is calculated by the following equation (2).

Wa/We=1.63d/t...(2) (Based on Pry and Bean's formula) Taking the above into consideration, conventional techniques have been to create scratches on the surface of silicon steel sheets and to create fine particles inside amorphous magnetic materials. The abnormal eddy current loss Wa was reduced by increasing the number of domain walls by increasing the number of domain walls by precipitating a crystalline material. When a so-called cut core is formed by cutting a section to provide an open magnetic path surface, the abnormal eddy current loss Wa, which is thought to be due to disturbance of magnetic flux in the open magnetic path surface formed by the cut surface orthogonal to the lamination direction, increases, and this iron loss increases. There was a problem in that the higher the frequency f, the higher the rate. for example,
Recently developed amorphous magnetic materials have lower iron loss than ferrite up to the high frequency range of several 100KHz, so
Application to a gapped laminated magnetic core that combines two cut cores has been considered, but although the core loss in a closed magnetic circuit core without a gap is small, as shown in Figure 2a, the When the laminated magnetic core A, which is formed by winding and laminating strip-shaped thin films, is cut as shown in FIG. 5B to form a gap G as shown in FIG. In other words, in a closed magnetic circuit core that is not cut, when the operating magnetic flux density Bm is 3KG and the frequency f is 20KHz, Mn
- Core loss of magnetic core A using Zn ferrite is 200m
W/cc, whereas the iron loss of laminated magnetic core A using cobalt-based amorphous magnetic material with zero magnetostriction is 50mW/cc.
cc, and the iron loss is a fraction of that. However, in a gapped laminated magnetic core A' in which an air gap G with a ratio of about 0.005 to the magnetic path length is provided,
The iron loss of the case using an amorphous magnetic material was more than twice that of the case using ferrite. It is generally accepted that, under conditions where the operating magnetic flux density Bm and frequency are constant, providing a gap increases the excitation current and increases copper loss, but does not increase iron loss. However, the reason why such an increase in iron loss actually occurs is thought to be as follows. In other words, a magnetic flux component perpendicular to the plate surface is generated in the open magnetic path plane, which is the cut surface.
On the other hand, the magnetic domain structure changes due to the generation of spike domains and reflux domains near the open magnetic path plane, which affects the domain wall movement mode and the number of domain walls during the magnetization process, and is thought to increase the abnormal eddy current loss Wa.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to reduce abnormal eddy current loss and iron loss when an open magnetic path surface consisting of a cut surface is provided.

[Disclosure of the invention]

(Structure) FIG. 3 shows the structure of the present invention, in which 1 is a laminated magnetic core body formed of a magnetic thin plate with high magnetic permeability and having an open magnetic path surface 1a partially formed of a cut surface;
The laminated magnetic core body 1 is made of at least one of an amorphous magnetic material, permalloy, silicon steel plate, electromagnetic soft iron, and sendust. Reference numeral 2 denotes a piece of magnetic material having high electrical resistance and magnetic permeability, and is disposed in contact with the open magnetic path surface 1a of the laminated magnetic core body 1 so as to cover the cut surface. One surface X of this magnetic material piece 1 is brought into close contact with the open magnetic path surface 1a, and the other surface Y serves as a gap forming surface. The magnetic material piece 2 is formed of a composite resin magnetic material in which ferrite or powdered magnetic material is dispersed in a synthetic resin.

Now, the magnetic material piece 2 with high electrical resistance and low eddy current loss is placed on the open magnetic path surface 1 of the laminated magnetic core body 1.
a, that is, the opposite end faces of the gapped laminated magnetic core A'' are brought into close contact with each other, and a gap G is formed between the magnetic pieces 2. Therefore, the cut surface of the open magnetic path surface 1a of the laminated magnetic core body 1 is magnetic. Since a gap G is formed on the other surface Y of the magnetic body piece 2, bending of the magnetic flux and disturbance of the magnetic domain structure around the gap part of the laminated magnetic core A'' will occur inside the magnetic body piece 2. The general eddy current loss
We and abnormal eddy current loss Wa are now reduced. Examples will be specifically described below.

Example 1 Figure 4 shows an example of the present invention, in which a thin ribbon of Co-based amorphous magnetic material (Co-Si-B-based alloy) with a ribbon width of 10 mm and a thickness of 25 μ and zero magnetostriction is made into a rectangular shape. Two wound magnetic cores A ₁ and A ₂ with a laminated thickness of approximately 8 mm are formed by winding into a shape, and both wound magnetic cores A ₁ and A ₂ are annealed to remove strain and then water cooled, which is a heat treatment to reduce so-called high-frequency iron loss. After fixing, insulating adhesive resin is impregnated between the layers of the wound magnetic cores A ₁ and A ₂ and between both wound magnetic cores A ₁ and A ₂ , and the central part is cut as shown in Fig. 4a. type magnetic core
Forms Aa and Ab. Here, the effective magnetic path length is 76 mm,
The effective magnetic path cross-sectional area was 64 mm ² , the magnetic core volume was 4.9 cc, and the iron loss was 30 mW/cc under operating conditions of an operating magnetic flux density of 1 KG and a frequency of 50 KHz without forming a gap with the cut surfaces in close contact. This E type magnetic core Aa,
When we measured the iron loss when expanding the unsaturated region of the B-H loop by setting an air gap G of about 0.5 mm between the cut surfaces of Ab, we found that the iron loss was 75 mW/cc.
This is twice as much as when there is no air gap G. Therefore, as shown in Figure 4b, a thin plate (1.5 mm thick) of magnetic material piece 2 made of soft ferrite and having the same area as the cross-sectional area of the magnetic path is placed in close contact with the open magnetic path surface formed by the cut surface. By doing so, the gap G
The increase in iron loss due to the provision of this was reduced. In other words, the iron loss when using Mn-Zn ferrite (effective magnetic permeability μe - 2000 at 1 KG, 50 KHz) as the magnetic piece 2 is 42 mW/cc compared to the iron loss when using Ni-Zn ferrite (μe = 350 at 1 KG, 50 KHz). The loss is
50mW/cc, and it can be seen that the one with high magnetic permeability is more effective in reducing the increase in iron loss due to gap G. Furthermore, Fig. 5 shows an experimental method for confirming the change in the effect of reducing the increase in iron loss depending on the placement position of the magnetic material piece 2. In Fig. 5 c, no reducing effect is obtained, and in Fig. Some effects can be obtained, and the greatest effect can be obtained in case a of the same figure.

Example 2 In the same configuration as in Example 1, a Co-based amorphous magnetic material (Co-Si-B-based alloy) with zero magnetostriction composition was used.
is mechanically pulverized to form a magnetic powder, and this magnetic powder is dispersed in a synthetic resin to form a composite magnetic material with high electrical resistance.The composite magnetic material is used to form a magnetic material piece 2. was formed. Here, the synthetic resin is a phenolic resin, the volume ratio of the phenolic resin is 50%, and the effective magnetic permeability μe of the composite magnetic material thus obtained is 45.

Now, as a result of measuring the iron loss in Example 2 under the same conditions as in the previous example, the iron loss was 65 mW/cc.
The effect of reducing the increase in iron loss was recognized.

FIG. 6 is a diagram qualitatively showing the effect of reducing the gap G and iron loss with respect to the material of the magnetic piece 2 of Examples 1 and 2, and as is clear from the figure, the magnetic permeability of the magnetic piece 2 is It can be seen that the higher the gap G, the greater the effect of reducing iron loss, and the longer the gap G, the greater the effect. In fact, it has been confirmed that a large iron loss reduction effect can be obtained even when a magnetic piece 2 is provided on the end face of an I-type laminated magnetic core A _I that has a completely open magnetic path as shown in Figure 7. Also, the 8th
As shown in the figure, it was confirmed that a large iron loss reduction effect could be obtained even in the case of a C-type laminated magnetic core Ac in which a gap G exists in the coil CO, and magnetic flux leakage at the gap part is small.

〔Effect of the invention〕

As described above, the present invention is made of a magnetic thin plate with high magnetic permeability, which has an open magnetic path surface partially consisting of a cut surface, and is made of at least one of amorphous magnetic material, permalloy, silicon steel plate, electromagnetic soft iron, and sendust. It consists of a laminated magnetic core body to be formed, and a magnetic piece made of ferrite having high electric resistance and magnetic permeability, which is placed in contact with each open magnetic path surface to cover the cut surface. Since a magnetic gap is formed between the other surfaces of the magnetic material pieces, the magnetic material pieces disposed in contact with the open magnetic path surface of the laminated magnetic core body prevent bending of magnetic flux and magnetic domains in the open magnetic path surface portion. This has the effect of reducing abnormal eddy current loss due to structural disturbance, and providing a magnetic core with little increase in iron loss even when a magnetic gap is formed.

[Brief explanation of the drawing]

Figure 1 shows the frequency characteristics of iron loss, Figure 2a
~c are perspective views showing the manufacturing process of the conventional example, Figures 3a and b are perspective views showing the configuration of the present invention, and Figures 4a,
b is a diagram showing the manufacturing process of one embodiment of the present invention, FIGS. 5 and 6 are explanatory diagrams of the same operation, and FIGS. 7 and 8 are diagrams showing other embodiments, respectively. 1 is a magnetic core body, and 2 is a magnetic piece.

Claims (1)

[Claims] 1. A laminated magnetic core body that has an open magnetic path plane partially consisting of a cut surface and is formed of a thin magnetic material plate with high magnetic permeability made of at least one of amorphous magnetic material, permalloy, silicon steel plate, electromagnetic soft iron, and sendust. , a magnetic material piece made of ferrite having high electric resistance and magnetic permeability, which is disposed in contact with each open magnetic path surface to cover the cut surface, and one surface of which is in contact with the open magnetic path surface and the other surface of the two magnetic material pieces is arranged to cover the cut surface. A magnetic core characterized in that a magnetic gap is formed in the core.