JP2014138016A - Noise absorption device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a noise current without increasing a size of a magnetic body even when a large current is applied.SOLUTION: In a noise absorption device 10 provided to a main circuit W, the main circuit W is divided into a high-impedance circuit 20 and a low-impedance circuit 30 so as to have the same current amount in a low-frequency region and to have a biased current amount in a high-frequency region. The high-impedance circuit and the low-impedance circuit are arranged so as to be opposed to each other in an annular magnetic body.

Description

  The present invention relates to a noise absorber.

  Conventionally, when a high-frequency noise current is superimposed on a low-frequency current in a low-frequency range, noise can be generated by inserting an electric wire through a cylindrical or annular magnetic body such as a ferrite core or winding the electric wire. The current is reduced. As such a technique, the one described in Patent Document 1 is known.

JP 2006-1000046 A

  By the way, when a large current flows through the electric wire, the magnetic material causes magnetic saturation, the performance as an inductor is lowered, the impedance is lowered, and the noise current cannot be sufficiently reduced. For this reason, when flowing a large current through the electric wire, it is necessary to increase the size of the ferrite core, and a countermeasure for this is eagerly desired.

  The present invention has been completed based on the above-described circumstances, and an object of the present invention is to reduce noise current without enlarging a magnetic material even when a large current is passed.

  As a means for achieving the above object, the present invention is a noise absorber provided in a main circuit, wherein the main circuit has the same amount of current in a low frequency region and a biased amount of current in a high frequency region. Thus, the high impedance circuit and the low impedance circuit are divided, and the high impedance circuit and the low impedance circuit are characterized in that they are arranged to face each other in an annular magnetic body.

  According to the noise absorbing device having such a configuration, the signal currents in the low frequency range in the magnetic body, the magnetic fluxes generated by the respective signal currents cancel each other and flow through each circuit without receiving resistance. However, in the case of a high-frequency noise current, the high-impedance circuit works as a resistor, so the noise current is biased toward the low-impedance circuit. A magnetic flux is generated in the magnetic body by a low impedance circuit, and the magnetic flux is converted into heat as a magnetic loss in the magnetic body, so that a noise current is reduced. That is, the low frequency current in the low frequency region passes through the magnetic body without receiving resistance, and only the noise current is reduced by the magnetic body. Thereby, a noise current can be reduced without increasing the size of the magnetic material.

The following configuration is preferable as an embodiment of the present invention.
The low-impedance circuit is made of a low-impedance conductor, and the high-impedance circuit is made of a high-impedance conductor that has the same cross-sectional area as the low-impedance conductor and has a smaller surface area than the low-impedance conductor. It is good.

  According to such a configuration, since the cross-sectional areas of the conductors in both circuits are the same, the low frequency current amounts in both circuits can be made the same. By the way, a so-called skin effect occurs in which a noise current having a high frequency is concentrated on the surface. Therefore, by reducing the surface area of the conductor, a high impedance circuit can be formed and the flow of noise current can be biased toward the low impedance circuit. Thereby, noise current can be reduced in the magnetic body.

The high impedance conductor may have a circular cross section, and the low impedance conductor may have a square shape with a flat cross section.
According to such a configuration, the surface area of the high impedance conductor can be made smaller than the surface area of the low impedance conductor.

The high impedance conductor may have a circular cross section, and the low impedance conductor may include a plurality of small diameter conductors each covered with an insulating coating.
According to such a configuration, the surface area of the high impedance conductor can be made smaller than the surface area of the low impedance conductor.

The high impedance circuit and the low impedance circuit may be made of a conductor having the same cross-sectional area, and the high impedance circuit may be provided with an inductor.
According to such a configuration, since the cross-sectional areas of the conductors in both circuits are the same, the low frequency current amounts in both circuits can be made the same. Further, by providing an inductor such as a coil, the inductance of the high impedance circuit can be increased, and the current can be made difficult to flow as the frequency increases. Thereby, noise current can be reduced in the magnetic body.

  According to the present invention, it is possible to reduce the noise current without enlarging the magnetic material even when a large current is passed.

1 is a perspective view of a noise absorber according to Embodiment 1. FIG. Cross section of noise absorber Cross section of conductor in high impedance circuit Cross section of conductor in low impedance circuit Sectional drawing of the conductor of the low impedance circuit concerning Embodiment 2 Sectional drawing of the noise absorber concerning Embodiment 3.

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to FIGS.
The present embodiment illustrates a noise absorbing device 10 provided in a main circuit W that connects an inverter (not shown) and a motor (not shown).
The main circuit W is configured by covering an outer periphery of a conductive conductor with an insulating coating.

  As shown in FIGS. 1 and 2, the noise absorbing device 10 includes a high impedance circuit 20 and a low impedance circuit 30 formed by dividing the main circuit W into two parts, and a short circuit through which these circuits 20 and 30 are inserted. And a cylindrical ferrite core (an example of a “magnetic body”) 40.

  As shown in FIG. 3, the high impedance circuit 20 has a form in which a circular conductor (an example of a “high impedance conductor”) 21 having a circular cross section is covered with an insulating coating 22, and has almost the same cut-off throughout the entire length. It is an area.

  As shown in FIG. 4, the low impedance circuit 30 has a shape in which a rectangular conductor 31 (an example of “low impedance conductor”) 31 having a flat cross section is covered with an insulating coating 32 around the entire circumference. The area is almost the same over the entire area. The rectangular conductor 31 has a cross-sectional area that is substantially the same as that of the circular conductor 21 and has a larger surface area than the circular conductor 21. In addition, in order to make a main part intelligible, about 1 and FIG. 2, the insulation coating of the high impedance circuit 20 and the low impedance circuit 30 is abbreviate | omitting illustration.

  The ferrite core 40 is a ceramic magnetic body mainly composed of iron oxide or the like, and reduces the noise current by inserting a conductor through which the noise current flows into the ferrite core 40. Specifically, when a noise current is passed through the ferrite core 40, a magnetic field generated from the noise current is collected in the core by a force that collects the magnetic flux of the ferrite core 40. The magnetic energy collected in the ferrite core is converted into heat by the magnetic loss of the ferrite and consumed, so that the noise current is reduced.

  As shown in FIGS. 1 and 2, the high impedance circuit 20 is inserted into the ferrite core 40 from one opening 41 (the upper opening in the drawing in FIG. 2) and the other opening 42 (the lower drawing in FIG. 2). The low impedance circuit 30 is inserted from the other opening 42 (lower opening in the drawing in FIG. 2) and led out from one opening 41 (upper opening in the drawing in FIG. 2). Two high-impedance circuits 20 and two low-impedance circuits 30 are arranged side by side so as to face each other in the ferrite core 40.

The noise absorbing device 10 of the present embodiment is configured as described above, and the operation and effect thereof will be described.
The inverter converts alternating current into direct current, and controls the motor at a variable speed by switching transistors. However, since a high-frequency noise current is generated by high-speed on / off control of the transistor, the noise current is superimposed on the low-frequency low-frequency current. For this reason, generally, a noise current is reduced by inserting an electric wire into a cylindrical or annular ferrite core or winding the electric wire. However, when a large current flows through the electric wire, the ferrite core causes magnetic saturation, and the performance as an inductor is lowered, so that the impedance is lowered and the noise current cannot be sufficiently reduced.

  However, according to the present embodiment, the cross-sectional area of the circular conductor 21 in the high-impedance circuit 20 and the cross-sectional area of the rectangular conductor 31 in the low-impedance circuit 30 are formed substantially the same. Both conductors 21 and 31 flow uniformly in a well-balanced manner, and the amount of current is the same. Then, the magnetic fluxes of the low frequency currents generated in the ferrite core 40 cancel each other, and the low frequency currents flow in the ferrite core 40 without receiving resistance.

  On the other hand, high-frequency noise currents flow on the surfaces of the respective conductors 21 and 31 due to the so-called skin effect concentrated on the surface of the conductor. For this reason, the circular conductor 21 of the high impedance circuit 20 has a higher current density on the surface of the circular conductor 21 than the rectangular conductor 31 of the low impedance circuit 30. And the resistance with respect to the noise current in the surface of the circular conductor 21 becomes high, and the noise current flows biased to the low impedance circuit 30. That is, an unbalanced state in which the amount of current in the high frequency region is biased toward the low impedance circuit 30 is obtained. Then, the magnetic flux of the noise current flowing through the low impedance circuit 30 in the ferrite core 40 is converted into heat as magnetic loss in the ferrite core 40 without being canceled.

  That is, the low frequency current in the low frequency region passes through the ferrite core 40 without receiving resistance, and only the noise current is reduced by receiving the resistance of the ferrite core 40. Thereby, even when flowing a large current, the noise current can be reduced without increasing the size of the ferrite core 40.

As described above, according to the present embodiment, the main circuit W is divided into the high impedance circuit 20 and the low impedance circuit 30, and both the circuits 20 and 30 are arranged to face each other in the ferrite core, whereby the noise current is obtained. Only the resistance of the ferrite core 40 can be reduced. That is, since the size of the ferrite core 40 can be set for the purpose of reducing only the noise current, the noise current can be reduced without enlarging the ferrite core 40 even when a large current is passed. .
Further, the cross-sectional area of the circular conductor 21 of the high impedance circuit 20 and the rectangular conductor 31 of the low impedance circuit 30 are made the same, and the surface area of the rectangular conductor 31 is simply increased compared to the surface area of the circular conductor 21. Since only the noise current in the high frequency region can be biased toward the low impedance circuit 30, it is effective in reducing the size of the noise absorbing device 10.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described with reference to FIG.
In the second embodiment, the shapes of the rectangular conductor 31 and the insulating coating 32 in the low-impedance circuit 30 in the first embodiment are changed, and the configuration, operation, and effects common to the first embodiment are duplicated. The description is omitted. The same reference numerals are used for the same configurations as those in the first embodiment.

  The low impedance circuit 130 of the second embodiment is a bundled electric wire 135 in which a plurality of small-diameter electric wires 133 are bundled. The small-diameter electric wire 133 has a form in which a small-diameter conductor (an example of a “low impedance conductor”) 131 having a circular cross section is covered with an insulating coating 132, and all the cross-sectional areas of the small-diameter electric conductor 133 in the small-diameter conductor 131 are combined. Is set to be substantially the same as the cross-sectional area of the circular conductor 21 in the high impedance circuit 20.

  That is, according to the present embodiment, the total cross-sectional area of the circular conductor 21 in the high-impedance circuit 20 and the small-diameter conductor 131 in the bundled electric wire 135 of the low-impedance circuit 130 is the same, and the bundle is larger than the surface area of the circular conductor 21. The total surface area of the small-diameter conductor 131 in the electric wire 135 can be significantly increased. As a result, only the noise current in the high frequency region can be largely biased toward the low impedance circuit 130, which is very effective in reducing the size of the noise absorbing device 10.

<Embodiment 3>
Next, Embodiment 3 of the present invention will be described with reference to FIG.
The noise absorbing device 210 according to the third embodiment is a modification of the high impedance circuit 20 according to the first embodiment, and the configuration, operation, and effect common to those in the first embodiment are duplicated, and thus the description thereof is omitted. The same reference numerals are used for the same configurations as those in the first embodiment.

The high impedance circuit 220 according to the third embodiment is configured to include a coil (an example of an “inductor”) 223 in the middle of the high impedance circuit 220.
The coil 223 has a winding structure in which a conductor is wound, and an inductance increases in proportion to the square of the number of turns, so that a current in a high frequency region is less likely to flow. That is, the flow of noise current in the high impedance circuit 220 can be reduced.
Thereby, the flow of noise current in the high frequency range can be biased toward the low impedance circuit 30, and only the noise current can be reduced by the ferrite core 40.
<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

(1) In the said embodiment, although it was set as the structure which applied the cyclic | annular ferrite core 40, this invention is not limited to such an aspect, For example, a cylindrical ferrite core or a pair of halves A cylindrical ferrite core may be applied, and a sheet-like magnetic body may be formed in a cylindrical shape.
(2) In the second embodiment, the bundled electric wire 135 in which the small-diameter electric wires 133 are bundled is used. However, the present invention is not limited to such an embodiment. For example, a plurality of conductors are insulated. A flat bundled electric wire (flat cable) covered in a lump may be used.
(3) In the third embodiment, the coil 223 around which the conductor is wound is provided as the inductor in the high impedance circuit 220. However, the present invention is not limited to such a mode. Alternatively, a multilayer inductor or a film-shaped chip inductor in which a conductive material and a conductive material are laminated may be provided in a high impedance circuit.

10, 210: Noise absorbers 20, 220: High impedance circuit 21: Circular conductor (high impedance conductor)
30, 130: Low impedance circuit 31: Rectangular conductor (low impedance conductor)
40: Ferrite core (magnetic material)
131: Small-diameter conductor of bundled wire (low impedance conductor)
223: Coil (inductor)
W: Main circuit

Claims (5)

A noise absorber provided in the main circuit,
The main circuit is divided into a high impedance circuit and a low impedance circuit so that the current amount in the low frequency region is the same and the current amount in the high frequency region is biased,
The high-impedance circuit and the low-impedance circuit are noise absorbers arranged to face each other in an annular magnetic body. The low impedance circuit is made of a low impedance conductor,
2. The noise absorbing device according to claim 1, wherein the high impedance circuit comprises a high impedance conductor having the same cross-sectional area as the low impedance conductor and a smaller surface area than the low impedance conductor. The high impedance conductor has a circular cross section,
The noise absorbing device according to claim 2, wherein the low impedance conductor is formed in a square shape with a flat cross section. The high impedance conductor has a circular cross section,
The noise absorbing device according to claim 2, wherein the low impedance conductor includes a plurality of small diameter conductors each covered with an insulating coating. The high impedance circuit and the low impedance circuit are made of a conductor having the same cross-sectional area,
The noise absorber according to claim 1, wherein the high impedance circuit is provided with an inductor.

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