JP2009164326A - Magnetic core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic core that is effectively cooled to thereby suppress the rising of temperature, and also improves the efficiency of a power converting apparatus using the magnetic core. <P>SOLUTION: The magnetic core is produced by mixing metal, such as copper and aluminum, with a magnetic material such as ferrite, as a high-heat conductive material having higher heat conduction characteristics than the magnetic member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic core, and more particularly to a magnetic core used for a transformer or a reactor in a power converter and a magnetic core suitable for suppressing a temperature rise of a winding wound around the magnetic core.

Conventionally, in a power conversion device such as a transformer that uses electromagnetic induction, the location of the transformer core (magnetic core) around which the winding is wound is caused by the heat generated by the iron loss of the magnetic core, In addition to the concentration of heat generated by copper loss, the cooling air to the magnetic core is hindered by the winding itself or the insulation sheet or bobbin that constitutes the transformer, so the temperature rise inside the magnetic core is most significant. Are known.
When the temperature rise inside the magnetic core becomes excessive, the insulating material near the magnetic core and windings may melt and break down. Further, when the temperature of the magnetic core rises, the saturation magnetic flux density in the magnetic core decreases, so that an excessive current flows through the winding due to magnetic saturation, and other components may be damaged. For this reason, when designing a magnetic component such as a magnetic core, it is necessary to pay attention to the maximum temperature reached by the magnetic component.
Therefore, this type of power conversion device suppresses the temperature rise as described above, forcibly air-cooling with a large fan, increasing the surface area of the magnetic component using a large magnetic core, increasing the heat dissipation area, A loss is reduced by using a member having a large wire diameter for the winding.
Or, as an alternative method, a ferrite core consisting of multiple compositions with different temperature dependence of magnetic properties such as magnetic core loss can be selected by selecting the optimal ferrite core composition corresponding to the temperature distribution, and the magnetic parts can be effectively used. Attempts have been made to cool composite ferrite cores (see, for example, Patent Document 1).

Alternatively, a heat release device is also proposed in which a heat sink is thermally coupled to a magnetic core (iron core) used in a device using electromagnetic induction to dissipate heat (see, for example, Patent Document 2).
JP 2003-163110 A JP-A-10-106847

However, the above-described heat release device disclosed in Patent Document 2 is merely provided with a high thermal conductivity material layer on the surface of the magnetic core, and although the heat dissipation on the surface is improved, the temperature at the center of the magnetic core is improved. Has a problem that it is higher than the surface and outer periphery of the magnetic core. In particular, the magnetic core may be damaged due to dielectric breakdown or magnetic saturation when such a locally high temperature portion exists.
Incidentally, as shown in the graph of FIG. 6, the magnetic core generally tends to increase iron loss and copper loss when the temperature rises. For this reason, the loss in the vicinity of the central portion of the magnetic core that becomes high temperature further increases, and there is a problem that the amount of heat generated by the magnetic core further increases.
Moreover, as shown in the graph of FIG. 6, the loss generated in the magnetic core varies depending on the temperature. For this reason, the magnetic core is desirably used at a temperature at which the loss is minimized (for example, temperature T1 in FIG. 6). However, if the temperature gradient inside the magnetic core is large, the temperature (eg, temperature T2 in FIG. 6) deviates from the temperature at which the loss generated inside the magnetic core is minimized on the magnetic core surface and outer periphery. When the temperature at the center rises (for example, temperature T3 in FIG. 6), there is a concern that the loss of the magnetic core increases, the amount of heat generation increases, and the temperature of the magnetic core rises.

In order to prevent such a temperature rise, the temperature gradient at the central portion of the magnetic core and other portions may be suppressed. For this reason, generally, a large-sized forced air cooling fan is used to enhance cooling, or the magnetic core (magnetic component) is enlarged to increase the surface area and enhance the cooling effect. However, these methods have a new problem that the size of the apparatus is increased and the cost is increased.
The present invention has been made in order to solve such a problem. The object of the present invention is to effectively cool the magnetic core to suppress the temperature rise, and the power conversion device using the magnetic core. An object of the present invention is to provide a magnetic core capable of improving efficiency.

In order to achieve the above-described object, the magnetic core according to the present invention is characterized by being produced by mixing a predetermined magnetic material such as ferrite with a high thermal conductive material having higher thermal conductivity than the magnetic material.
In this magnetic core, a material having high heat conduction characteristics is added to the material of the magnetic core and dispersed in the core, thereby improving the heat conduction characteristics.
Alternatively, the magnetic core according to the present invention is characterized in that the content of the high heat conductive material in the vicinity of the winding wound around the magnetic core is higher than that of the other magnetic core.
Preferably, the high thermal conductive material includes at least one of copper and aluminum.
The above-described magnetic core can efficiently dissipate heat from the central portion to the outer peripheral portion by including, for example, copper or aluminum as a material having a high thermal conductivity in the high temperature portion.
Alternatively, the magnetic core of the present invention includes a cavity portion that communicates with a magnetic path that circulates in the magnetic core, and a fluid that is enclosed in the cavity portion and receives heat generated in the magnetic core. It is characterized by having.

The magnetic core described above provides a cavity in the magnetic core and encloses a fluid such as water whose density changes with temperature in the cavity, and causes the fluid to convect by a temperature gradient between the center and the outer periphery of the magnetic core. Heat transfer between the magnetic core center and the outer periphery is improved. And the temperature difference of a magnetic core center part and an outer peripheral part is suppressed.
Preferably, the hollow portion is provided with a plurality of cavities in which a cross-sectional area in the vicinity of a winding wound around and attached to the magnetic core is narrower than other portions.
The above-mentioned magnetic core has a smaller cavity diameter at a portion that becomes a high temperature portion than the other portion (magnetic core outer peripheral portion) such as the vicinity of the winding wound around the magnetic core (magnetic core central portion). In addition, by increasing the number of cavities, efficient heat transfer can be performed between the magnetic core central portion and the outer peripheral portion, and therefore the temperature difference between the magnetic core central portion and the outer peripheral portion is suppressed. It is done.
Or the magnetic core of this invention can improve the heat transfer between a core center part and an outer peripheral part by combining the method mentioned above suitably.

As described above, since the magnetic core of the present invention has improved heat conduction characteristics, it is possible to effectively cool a local high temperature portion generated in the central portion of the magnetic core. Therefore, the power conversion device using the magnetic core according to the present invention can be operated safely by reducing iron loss and copper loss with high efficiency and suppressing deterioration of the insulator.
The magnetic core of the present invention can reduce the temperature gradient in the magnetic core and make the temperature distribution uniform. As a result, the power conversion device using the magnetic core according to the present invention can reduce the size and weight of the magnetic component and the cooling component, thereby reducing the cost and loss of the device. There is a great practical effect.

Hereinafter, a magnetic core according to an embodiment of the present invention will be described with reference to the drawings. 1-5 is a figure for demonstrating the magnetic core which concerns on one Embodiment of this invention, Comprising: These figures do not limit this invention.
<Example 1>
FIG. 1 is a perspective view showing the structure of a transformer to which the magnetic core of the present invention is applied, and FIG. 2 is a sectional view thereof. In these drawings, reference numeral 10 denotes, for example, two well-known EE type magnetic cores, and reference numeral 2 denotes a winding wound around the magnetic cores.
In general, the magnetic core of the present invention configured as described above is characterized in that a magnetic material such as ferrite has higher heat conduction characteristics than this magnetic material, such as copper and aluminum. It is in the point which mixed the high heat conductive material which has and produced | generated the magnetic core (high heat conductive material containing) 10.
More specifically, magnetic material such as ferrite, which is the main constituent material of the magnetic core, is mixed with copper, aluminum, or other powders of materials having high thermal conductivity characteristics, and is molded and sintered. Then, for example, a magnetic core (containing a high thermal conductivity material) 10 suitable for power conversion equipment such as a transformer is created.

The magnetic core of the present invention configured in this way is mixed with a different kind of material having a higher thermal conductivity than the main constituent material of the magnetic core (for example, a magnetic material such as ferrite) to contain the magnetic core (containing a high thermal conductivity material). Therefore, the heat conduction characteristics can be improved as compared with the conventional magnetic core. Therefore, the magnetic core of the present invention can efficiently dissipate the heat in the vicinity of the center of the magnetic core (containing the high thermal conductivity material) 10 where the temperature rises most, and further, the heat in the outer peripheral portion of the magnetic core The temperature rise can be effectively suppressed in combination with the cooling by the diffusion.
<Example 2>
Next, a magnetic core according to a second embodiment of the present invention will be described with reference to a cross-sectional view of the transformer shown in FIG.
The difference between the second embodiment and the first embodiment described above is that the vicinity of the winding 2 being wound around the magnetic core (containing the high thermal conductivity material) 10 produced by mixing the high thermal conductivity material, that is, the temperature of the magnetic core. In order to improve the heat conduction characteristics in the middle foot portion 10a where the temperature rises the most, the magnetic core is generated by adding more high heat conductive material to the middle foot portion 10a.
The magnetic core according to the second embodiment of the present invention configured as described above can more effectively disperse the heat in the vicinity of the central portion of the magnetic core (containing a high thermal conductive material) 10 throughout the magnetic core. Furthermore, the magnetic core according to the second embodiment of the present invention can effectively suppress the temperature rise in combination with the cooling due to heat dissipation at the outer peripheral portion of the magnetic core (containing a high thermal conductivity material) 10.
<Example 3>
Next, a magnetic core according to Embodiment 3 of the present invention will be described with reference to the cross-sectional view of the transformer shown in FIG. The magnetic core in the third embodiment may be produced by mixing a high thermal conductive material as shown in the first and second embodiments, or may be produced by using the same material as the conventional magnetic core. Absent. Here, the magnetic core 1 made of the same magnetic material as the conventional magnetic core (for example, ferrite) will be described for convenience.

This embodiment differs from the first and second embodiments described above in that a hollow portion 20 is provided inside the magnetic core 1 so as to circulate around the magnetic core 1 and is enclosed in the hollow portion. The fluid 21 absorbs heat generated in the magnetic core 1 by induction.
The fluid 21 is preferably a fluid that causes convection due to a density difference caused by a temperature difference, such as water.
Now, in the cross-sectional view of the transformer shown in FIG. 4, the central portion in the cross-sectional direction of the middle leg 1 a of the magnetic core 1 around which the winding 2 is wound is the place where the temperature rise is most remarkable. On the other hand, cooling occurs effectively in the outer peripheral portion 1b of the magnetic core 1. For this reason, a temperature gradient is generated between the center portion of the middle leg portion 1a of the magnetic core 1 and the outer peripheral portion 1b, and the fluid 21 convects as shown by a path indicated by an arrow.
Thus, the magnetic core according to the third embodiment of the present invention can dissipate the heat of the central portion of the magnetic core 1 throughout the magnetic core 1 and increase the temperature of the magnetic core 1 by cooling due to heat dissipation in the outer peripheral portion 1b. It can be effectively suppressed.
<Example 4>
Next, a magnetic core according to Embodiment 4 of the present invention will be described with reference to a cross-sectional view of the transformer shown in FIG. This embodiment differs from the third embodiment described above in that the diameter of the cavity 20 is small and the cavity is close to the center of the magnetic core 1 where the temperature rises most like the middle leg 1a of the magnetic core 1. The number of 20 is provided.

The magnetic core according to the fourth embodiment of the present invention configured as described above can more efficiently disperse the heat generated in the middle leg portion 1a of the magnetic core 1 to the entire magnetic core 1, and at the outer peripheral portion 1b. The temperature rise can be effectively suppressed in combination with cooling by heat dissipation.
In the first to fourth embodiments described above, if the magnetic core 1 is set to operate while maintaining the temperature at which the iron loss is minimized by cooling the magnetic core 1 (for example, the temperature T1 shown in FIG. 6), the magnetic core 1 Loss can be further reduced, and furthermore, the temperature in the vicinity of the middle leg portion 1a where the temperature of the magnetic core 1 becomes highest can be lowered, and the copper loss of the winding 2 can be reduced.
Alternatively, the magnetic core 1 of the present invention may of course be implemented by appropriately combining the above-described Examples 1 to 4.
As described above, the magnetic core of the present invention is a magnetic component applied to power conversion devices such as transformers, reactors, and rotating devices used in power conversion devices such as power factor correction circuits, DC-DC converters, UPSs, and inverters. By using it, there is a practically great effect that the efficiency of the power conversion device can be improved while effectively suppressing the temperature rise.
The magnetic core of the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the present invention.

The perspective view which shows the structure of the transformer using the magnetic core which concerns on Example 1 of this invention. Sectional drawing of the transformer shown in FIG. Sectional drawing which shows the structure of the transformer using the magnetic core which concerns on Example 2 of this invention. Sectional drawing which shows the structure of the transformer using the magnetic core which concerns on Example 3 of this invention. Sectional drawing which shows the structure of the transformer using the magnetic core which concerns on Example 4 of this invention. The graph which showed the temperature dependence of the iron loss and copper loss of a transformer.

Explanation of symbols

2 Winding 10 Magnetic core (Contains high thermal conductivity material)
20 Cavity 21 Fluid

Claims (5)

  A magnetic core produced by mixing a predetermined magnetic material with a high thermal conductivity material having higher thermal conductivity than the magnetic material.   2. The magnetism according to claim 1, wherein the magnetic core has a higher content of the high heat conductive material in the vicinity of a winding wound around the magnetic core than that of the other magnetic core. core.   The magnetic core according to claim 1, wherein the high thermal conductive material includes at least one of copper and aluminum. A magnetic core applied to a power conversion device that converts power by electromagnetic induction,
The magnetic core includes a hollow portion provided in communication along a magnetic path that circulates in the magnetic core; and
A magnetic core comprising: a fluid that is sealed in the hollow portion and receives heat generated in the magnetic core.   5. The magnetic core according to claim 4, wherein the hollow portion has a plurality of cavities with a cross-sectional area in the vicinity of a winding wound around and attached to the magnetic core narrower than other portions.

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