JP2008060495A - Reactor and noise filter using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactor by which the high damping characteristic can be acquired in the entire frequency band without requiring especial ingenuity for how to wind a coil, etc., and to provide a noise filter using it. <P>SOLUTION: In a figure, the cross section of a common mode reactor is shown. The common mode reactor comprises a core 1, a case 2 for core and a coil 3 wound around the core 1 with the case 2 for core between. As the case 2 for core, a material whose dielectric dissipation factor is ten times (0.003) or more of a conventional material whose dielectric dissipation factor is at most about 0.0003 is used. Thereby the impedance attenuation characteristic especially in a high frequency region is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reactor and a noise filter using the reactor.

In general, a reactor for a filter has an effect of attenuating high-frequency noise, and is mainly used by being connected to an electric or electronic circuit or its power source. Hereinafter, a common mode reactor as described in, for example, Patent Document 1 will be described as an example.
FIG. 3 shows a typical application example. As illustrated, when a common mode reactor is connected between the circuit 1 and the circuit 2, common mode high frequency noise between the circuits is attenuated. The attenuation characteristics depend on the impedance of the common mode reactor.

  The common mode reactor includes a magnetic core and a coil (winding) that winds the magnetic core, and the coil includes two phases or three phases. FIG. 4 shows an example of a common mode reactor having a two-phase coil. Further, a conductive wire with a film is usually used to insulate between the coils, and a magnetic core with a cover or a case is used to insulate between the coil and the magnetic core. An example having a coated wire and a magnetic core case is shown in FIG. 5A shows a reactor, and FIG. 5B shows a cross section of the coil.

  In order to remove more noise with the above-described common mode reactor, it is generally considered that the impedance of the common mode reactor is increased to some extent to improve the attenuation characteristics. Therefore, if the number of turns of the coil is increased in order to increase the impedance of the common mode reactor, the stray capacitance of the common mode reactor increases and the impedance in the high frequency region decreases. That is, although the attenuation characteristic of the noise filter with respect to the common mode noise is improved in the low frequency region, the high frequency region is deteriorated as shown in FIG.

JP 2001-112266 A

In such a case, if the attenuation characteristics of the noise filter are to be improved in the high frequency region, it is necessary to reduce the stray capacitance of the common mode reactor, reducing the number of turns of the coil, or a common winding with a special winding method. A mode reactor must be used.
However, when the number of turns of the coil is reduced, the impedance is lowered, and the attenuation characteristic in the low frequency region of the noise filter is lowered.

On the other hand, using a common mode reactor with a special winding method results in a decrease in productivity and a high cost. That is, the conventional noise filter has a problem that it is difficult to obtain high attenuation characteristics in a wide frequency band with respect to noise.
Accordingly, an object of the present invention is to provide a reactor capable of obtaining a high attenuation characteristic in the entire frequency band, and a noise filter using the same, regardless of how the coil is wound.

In order to solve such a problem, in a reactor including a magnetic core, a case for the magnetic core, and a coil that winds the magnetic core through the case for the magnetic core,
In the invention of claim 1, the case for the magnetic core is characterized by using a dielectric loss tangent of 0.003 or more,
In the invention of claim 2, the thickness of the case for the magnetic core is 2 mm or more,
The invention according to claim 3 is characterized in that the film thickness of the coil is 0.1 mm or more.

Similarly, in a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
In the invention of claim 4, the case for the magnetic core is characterized by using a dielectric loss tangent of 0.003 or more and a thickness of 2 mm or more,
The invention of claim 5 is characterized in that the magnetic core case has a dielectric loss tangent of 0.003 or more and a film thickness of the coil of 0.1 mm or more.
The invention according to claim 6 is characterized in that the magnetic core case has a thickness of 2 mm or more and a coating thickness of the coil of 0.1 mm or more.

In the invention of claim 7, in a reactor comprising a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core via the case for the magnetic core,
As the case for the magnetic core, a case where a dielectric loss tangent is 0.003 or more, a thickness is 2 mm or more, and a film thickness of the coil is 0.1 mm or more is used.
In invention of Claim 8, a noise filter can be comprised using any one of the said Claims 1-7.

  According to the present invention, a coil capable of obtaining a high attenuation characteristic in the entire frequency band by simply selecting a material characteristic and the like without requiring any special device for winding the coil, etc., and a noise using the coil A filter can be obtained.

FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining the effect of the present invention.
In general, the stray capacitance of the common mode reactor includes a stray capacitance (capacitance between coils) C1 generated between coils and a stray capacitance (magnetic case capacitance) C2 generated in a magnetic core case as shown in FIG.

  By the way, the dielectric loss of the material used for the magnetic core case and the conductive film is small or almost equal to 0 in the low frequency region, but becomes large in the high frequency region. The present invention pays attention to such properties and increases the dielectric loss of the stray capacitance as compared with the prior art, thereby increasing the impedance in the high frequency region and improving the noise attenuation characteristic in the high frequency region.

  Conventionally, polyethylene and polypropylene are usually used in the magnetic core case, and the dielectric loss tangent (tan δ) is at most about 0.0003. Therefore, in the present invention, a magnetic core case having a dielectric loss tangent of 0.003 or more is used. Thereby, the dielectric loss of the magnetic core case capacitance C2 shown in FIG. 1 increases. As the material, for example, an epoxy resin or vinyl can be used instead of the polyethylene or polypropylene, and a resin blended with rubber or the like can be used. The reason why the dielectric loss tangent is set to 0.003 or more is that it is considered that a dielectric loss tangent of about 10 times is necessary to increase the impedance significantly compared with the conventional one. Here, although a magnetic core case is assumed, any film may be used as long as it is disposed between the magnetic core and the coil and has a function equivalent to that of the magnetic core case. For example, a coating integrated with the magnetic core may be used.

  The thickness of the magnetic core case is generally about 1 mm. Therefore, in the present invention, the dielectric loss of the magnetic core case capacitor C2 shown in FIG. 1 is increased by using a magnetic core case that is thicker than a general magnetic core case, for example, 2 mm thick (magnetic core case capacitor C2 itself). Will decrease). The reason why the thickness is set to 2 mm or more is that it is considered that a dielectric loss tangent of about twice is necessary to increase the impedance significantly compared with the conventional one. Also in this case, instead of the magnetic core case, anything may be used as long as it is disposed between the magnetic core and the coil and has a function equivalent to that of the magnetic core case. For example, a film integrated with the magnetic core may be used. It is the same.

  Furthermore, the film thickness of the coated conductor widely used as a coil is at most about 0.02 mm when the conductor diameter is 0.1 mm, and at most about 07 mm when the conductor diameter is 3.2 mm. Therefore, in the present invention, a coil having a thicker film than a general coated wire, for example, 0.1 mm or more is used as the coil, thereby increasing the inter-coil capacity C1 shown in FIG. Will decrease). The reason why the thickness is set to 0.1 mm or more is that it is considered that a dielectric loss tangent of about 5 times is necessary to increase the impedance significantly compared with the conventional one.

By doing as described above, the frequency characteristic of the impedance of the common mode reactor becomes as shown in FIG. 2, and the characteristic is improved particularly in the high frequency region, as is apparent from comparison with FIG. 6 in the conventional case. I understand.
In addition, although the case of the common mode reactor was demonstrated above, it is applicable not only to this but a normal reactor. Ferrite is assumed as the magnetic core, but any magnetic material may be used. An enameled copper wire is assumed for the coil, but any wire with a coating may be used.
Furthermore, it goes without saying that the reactor as described above can be used as a common mode noise filter as described in FIG. 3 or a general noise filter.

Explanatory drawing explaining embodiment of this invention Characteristic diagram for explaining the effect of the present invention Illustration of application example of common mode reactor External view showing an example of a common mode reactor Sectional view showing an example of a common mode reactor Impedance characteristics for frequency of common mode reactor

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnetic core, 2 ... Magnetic core case, 3 ... Coil, C1 ... Coil capacity | capacitance, C2 ... Magnetic core case capacity | capacitance.

Claims (8)

In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a dielectric loss tangent of 0.003 or more is used as the magnetic core case. In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a thickness of the magnetic core case of 2 mm or more. In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a thickness of the coil of 0.1 mm or more. In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a dielectric loss tangent of 0.003 or more and a thickness of 2 mm or more is used as the magnetic core case. In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a dielectric loss tangent of 0.003 or more and a film thickness of the coil of 0.1 mm or more is used as the magnetic core case. In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a thickness of the magnetic core case of 2 mm or more and a film thickness of the coil of 0.1 mm or more is used. In a reactor including a magnetic core, a case for the magnetic core, and a coil for winding the magnetic core through the case for the magnetic core,
A reactor having a dielectric loss tangent of 0.003 or more, a thickness of 2 mm or more, and a coil film thickness of 0.1 mm or more is used as the magnetic core case.   The noise filter using the reactor as described in any one of Claims 1-7.

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