JPH1174129A - Low-loss composite magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and weight of a low-loss composite magnetic core which is used at a high frequency by arranging a permanent magnet on the surface of a coil, using an Mn-Zn ferrite with the S-pole of the magnet at one end of the surface of the magnet perpendicular to the magnetic path of the ferrite and the N-pole at the other end of the surface. SOLUTION: After 53.0 mol.% Fe2 O3 , 38.0 mol.% Mn3 O4 , and 19.0 mol.% ZnO are mixed together and kneaded wet for 20 minutes, the mixture is dried, granulated, and calcined at 800 deg.C. Then, after adding 0.04 wt.% SiO2 , 0.04 wt.% CaO, and 0.10 wt.% ZrO2 to the calcined product, the product is pulverized wet for 120 minutes and the powder is dried, granulated, and pressed. A permanent magnet 1 having a different surface magnetic flux in the direction of magnetization is arranged on one surface of a coil 5, which is formed by winding an exciting winding 4 around a ferrite core 2 composed of the sintered body obtained in this way, and the magnet 1 is fixed with a resin 3. Therefore, the loss of the magnet 1 other than the hysteresis loss is reduced, when the surface magnetic flux of the magnet 1 falls within a range of 100 to 1,000 G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-loss composite core made of ferrite for a transformer used at a high frequency.

[0002]

2. Description of the Related Art As a power transformer material, an Mn-Zn ferrite core having a relatively high saturation magnetic flux density and a small power loss is used. For example, ring core, EE
There are a core, an EI core, and the like, and their sizes also vary.

[0003] If the power loss of the transformer material is large, heat generation may cause a failure or malfunction.

[0004] Generally, in Mn-Zn ferrite, the loss is reduced by examining the main component composition, additives, powder characteristics, and firing conditions. However, in recent years, miniaturization and weight reduction of electric products have been attempted. Accordingly, the frequency of power transformers has been increasing, and accordingly, further reduction in loss of ferrite cores has been required.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-loss composite core made of ferrite for a transformer used at a high frequency with low loss and reduced in size and weight.

[0006]

According to the present invention, a permanent magnet is arranged on the surface of a Mn-Zn ferrite core, and the Mn-Z ferrite core is provided with a permanent magnet.
This is a low-loss composite core in which one end of a surface perpendicular to the magnetic path of the n-ferrite core has an S pole and its counter electrode has an N pole.

[0007] The present invention also relates to a Mn-Zn ferrite core in which a permanent magnet is disposed on the surface of a coil using the Mn-Zn ferrite core.
One end of the surface perpendicular to the magnetic path of the Zn ferrite core is the S pole,
This is a low-loss composite magnetic core whose counter electrode has an N pole.

Further, the present invention is a low-loss composite core having a surface magnetic flux of 100 to 1000 G in the magnetizing direction of the permanent magnet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A low loss composite magnetic core according to the present invention will be described.

According to the present invention, a permanent magnet having a surface magnetic flux of 100 to 1000 G in a magnetizing direction is arranged on the surface of a Mn-Zn ferrite core or the surface of a coil using the Mn-Zn ferrite core. The above problem is solved by using a low-loss composite magnetic core having one end of a surface perpendicular to the magnetic path as the S pole and the other pole as the N pole.

In the low-loss composite core of the present invention, the power loss of the ferrite is composed of hysteresis loss, eddy current loss, and residual loss. A permanent magnet applies a magnetic field in a direction perpendicular to the magnetic path of the ferrite core. It is considered that the domain wall disappears and the hysteresis loss caused by the irreversible movement of the domain wall and the eddy current loss locally generated in the crystal grain due to the domain wall movement are both reduced.

The surface of Mn--Zn ferrite core or M
The surface magnetic flux in the magnetization direction of the permanent magnet arranged on the surface of the coil using the n-Zn ferrite core is 100 to 1000.
The reason for G is that if it is smaller than 100 G, the domain wall in the ferrite core remains and the loss does not decrease.
On the other hand, if it is larger than 1000 G, the spin orientation in the excitation direction is not easy, and the loss is deteriorated.

[0013]

Embodiments of the present invention will be described below.

[0014] Fe ₂ O ₃ , Mn ₃ O ₄ and ZnO
3.0Fe ₂ O ₃ -38.0MnO-balance ZnO (mol
%), Mixed in a wet manner for 20 minutes, dried and granulated, and calcined in the air at 800 ° C., and 0.04 wt% of SiO ₂ was added to the obtained powder as a sub-component. After adding CaO of 0.04% by weight and ZrO ₂ of 0.10% by weight, each was pulverized in a wet system for 120 minutes, dried, granulated, and pressed.

[0015] Then, in an atmosphere in which the oxygen partial pressure is controlled, 1
It baked at 150 degreeC for 120 minutes.

As shown in FIG. 1 (a), on one side of a coil 5 obtained by applying a winding 4 for excitation to a ferrite core 2 of a sintered body having a size of 25 mmφ-15 mmφ-5 mm obtained as described above. The size of the surface magnetic flux in the magnetization direction is 25mmφ-
A permanent magnet 1 having a diameter of 15 mm and a diameter of 5 mm was disposed, and the loss of a structure (structure) fixed with the resin 3 was measured.

Further, as shown in FIG. 1 (b), one side of a ferrite core 2 of a sintered body having a size of 25 mmφ−15 mmφ−5 mm obtained in the same manner has a different surface magnetic flux in the magnetization direction. Was arranged with a permanent magnet 1 having a diameter of 25 mm to 15 mm and a diameter of 5 mm.

FIG. 1 is a schematic view of the structure and the structure of FIGS. 1A and 1B.

Table 1 shows the measurement results of the loss at 1 MHz-500 G and 80 ° C.

[0020] Excitation condition: 1MHz-500G, measurement temperature: 80 ° C

As a comparative material, the measurement results when no permanent magnet is arranged are also shown. The value obtained by multiplying the DC excitation loss by the AC excitation frequency was used as the hysteresis loss.

As a result, the following points became clear. That is, in both the structures, the surface magnetic flux of the permanent magnet is 100 to 1
Loss other than hysteresis loss in the range of 000G (Pcv
−Ph) are both reduced.

At the surface magnetic flux of 50 G, the structure, the loss, and the loss are the same as those of the comparative material. Also, with a surface magnetic flux of 1200G,
Both structure and loss are deteriorating. This is because the loss other than the hysteresis loss, that is, the eddy current loss or the residual loss, is degraded although the hysteresis loss is reduced.

As an example, the surface magnetic flux of the permanent magnet is 500 G
FIG. 2 shows the temperature change of the loss in the case (1). The structure is indicated by a curve, the structure is indicated by a curve b, and the case without a permanent magnet is indicated by a curve c. In both cases, the loss is reduced in the temperature range from normal temperature to 120 ° C.

The result as shown in Table 1 is that Mn-Z
When the surface magnetic flux in the magnetization direction of the permanent magnet disposed on the surface of the n-ferrite core or the coil using the Mn-Zn ferrite core is in the range of 100 to 1000 G, the permanent magnet is perpendicular to the magnetic path of the Mn-Zn ferrite core. Magnetic field is applied in a certain direction, the domain wall disappears, and hysteresis loss and domain wall movement caused by irreversible movement of the domain wall cause
It is considered that the loss due to the eddy current locally occurring in the crystal grain is reduced together.

When the surface magnetic flux is smaller than 100 G,
The domain wall in the ferrite core remains and the loss does not decrease,
On the other hand, if it is larger than 1000 G, it is considered that spin orientation in the excitation direction is not easy, and losses other than the hysteresis loss are deteriorated.

[0027]

As described above, according to the present invention,
It is possible to provide a low-loss composite core used at a high frequency, which is reduced in size, weight, and cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing the structure and structure of a low-loss composite magnetic core of the present invention. FIG. 1A is an explanatory view showing a structure of a low-loss composite magnetic core of the present invention. FIG. 1B is an explanatory view showing the structure of the low-loss composite magnetic core of the present invention.

FIG. 2 is a graph showing a comparison between the temperature change of the total loss (Pcv) at 1 MHz to 500 G when the surface magnetic flux of the permanent magnet of the structure (see curve a) and the structure (see curve b) of the low-loss composite core of the present invention is 500 G Explanatory drawing which shows the temperature change of the total loss (Pcv) of the material (refer to curve c) under the same conditions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Permanent magnet 2 Ferrite core 3 Resin 4 Winding 5 Coil

Claims (3)

[Claims] 1. A permanent magnet is arranged on a surface of a Mn-Zn ferrite core, and one end of a surface perpendicular to a magnetic path of the Mn-Zn ferrite core has an S pole and a counter electrode has an N pole. A low-loss composite magnetic core characterized by: 2. A permanent magnet is disposed on the surface of a coil using a Mn-Zn ferrite core, and one end of a surface perpendicular to the magnetic path of the Mn-Zn ferrite core is an S pole and its counter electrode is an N pole.
A low-loss composite core characterized by having poles. 3. The low-loss composite magnetic core according to claim 1, wherein the surface magnetic flux of the permanent magnet in the magnetizing direction is 100.
A low-loss composite magnetic core characterized by being up to 1000 G.