DC heavy-current normal mode inductor and noise filter

Abstract

To realize a noise filter by a magnetic core without causing a magnetic saturation in a circuit in which a heavy-current is flown.SOLUTION: A heavy-current is divided into a plurality of conductors, and a noise filter by a magnetic core is provided to each of the plurality of conductors. The magnetic core is constructed so that one conductor passes into the plurality of different magnetic cores, and a frequency band can be expanded by making a characteristic of a plurality of cores to be different. In addition of a cutoff of a normal mode noise, a core type noise filter that can be corresponded to a common mode noise can be provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a large current normal mode inductor and a noise filter that can effectively block noise in a circuit through which a large current flows. More specifically, the present invention relates to a noise filter inductor device and a noise filtering method that realizes an effective noise filtering effect by avoiding the effects of magnetic saturation of normal mode inductors as a noise filter in a switching circuit through which a large current flows. [Background technology]

[0002] Inverters and high-voltage DC / DC converters for power motors in electric vehicles, hybrid vehicles, electric aircraft, etc. often perform switching at 10 kHz to 200 kHz, but these harmonics can sometimes cause noise interference problems. For example, harmonic noise caused by switching is radiated from the harness between the inverter and battery of an electric vehicle, affecting AM radio, wireless communication, and in-car communications. Additionally, harmonics of switching noise leak from DC / DC converters used in electric vehicle development test benches and solar power generation systems, causing EMC problems. Generally, normal mode noise and common mode noise are mixed in power electrical circuits, but in high current circuits, noise filters using inductors with ring cores to filter out normal mode noise have not been realized due to the occurrence of magnetic saturation caused by large currents. For this reason, in conventional technology, inductors using normal mode cores to block noise could not be used in circuits through which large currents flow, and filters that use cores have generally been for common mode use, having a common mode core. Generally, most noise countermeasures have been developed at the level of handling voltage and current in the so-called low-current field, but noise countermeasures in circuits where extremely large currents flow, which is the field of the present invention, have been lacking. That is, in electric vehicles and hybrid vehicles where large currents flow, the method of containing noise radiation by using shielded wires has been the norm. However, since wire harnesses using shielded wires have a complex structure and are expensive, there has been a demand for a noise reduction method for large currents that reduces the noise itself.

[0003] Note that magnetic saturation here refers to the phenomenon in which, even in the case of a material with high magnetic permeability, when a very large magnetic field is applied, the permeability decreases and eventually approaches the relative permeability of 1, in other words, the permeability of a vacuum, μ₀. Therefore, when using a ferrite core, for example, as a noise killer, if a ferrite core is used as a noise killer for an electric wire through which a strong magnetic field, i.e., a large current, flows, the inductance is reduced by the action of the strong magnetic field caused by the large current, making it impossible to use as a noise killer. Even in the case of a ferromagnetic material, which is a magnetic material with an extremely high magnetic permeability, the magnetic permeability, i.e., the hysteresis curve in the BH curve, will experience magnetic saturation, where the slope at the upper and lower sides becomes zero, i.e., the relative permeability becomes 1. When a magnetic field H is applied to a magnetic material, the spins become aligned, but once all the spins can no longer be aligned, the increase in magnetic flux density due to spin alignment reaches a plateau, no matter how much the magnetic field is increased.

[0004] As a result, magnetic saturation occurs, where the magnetic flux density does not increase even if the magnetic field is further increased. When magnetic saturation occurs, the noise blocking effect due to the energy consumption caused by the reversal of the magnetic moment of the magnetic core, which will be described later, disappears, the relative permeability becomes 1, and the noise current blocking effect due to inductance is also reduced. For this reason, in the prior art, magnetic cores have not been used as a means for suppressing normal mode noise that propagates through electric wires carrying large currents.

[0005] Patent Document 1 discloses that "There is known a noise filter that has a divided magnetic core that surrounds the periphery of a bus bar to attenuate noise propagating through the bus bar (see Patent Document 1, for example). In the case of wiring through which a large current flows, such as a bus bar, it is important to suppress magnetic saturation of the magnetic core, particularly in a differential mode noise filter. In the case of the noise filter described in Patent Document 1 below, a gap spacer portion is provided that is sandwiched between one core member and the other core member, thereby forming a gap between the one core member and the other core member and suppressing magnetic saturation" (paragraph 0002), and introduces Japanese Patent Application Laid-Open No. 2005-93536 as Patent Document 1. However, simply providing a gap is insufficient to effectively block normal mode noise in a circuit through which a large current flows, such as that in an electric vehicle.

[0006] Patent Document 2 discloses that "The ferrite core of the filter unit described above to be mounted in an inverter device as an EMC filter must be selected so that its impedance characteristics and high-frequency characteristics are appropriate for the magnitude and frequency of the noise current, and the carrier frequency of the inverter. In practice, an EMC filter selected for each type of inverter device with different ratings is implemented and verified, and the noise reduction effect is evaluated and confirmed before making a decision. For example, when the amount of noise current generated is large, in order to avoid magnetic saturation of the ferrite core, it is necessary to change the selection, such as increasing the number of ring-core ferrite cores 1 shown in Figure 8 and arranging multiple cores on the same axis, and winding cable 2 collectively around these ferrite cores to form filter unit 3" (paragraph 0007). However, even if multiple ferrite cores are arranged on the same axis, they cannot be used in a circuit through which a current flows that would magnetically saturate the multiple cores.

[0007] In Patent Document 3, it is stated that "When the inductor is inserted into a signal line, particularly a power line, the problem is that the magnetic saturation of the core material limits the effective current value" (paragraph 0039). "Therefore, in the line noise attenuator according to the embodiment of the present invention, the number of windings in one core material is limited to the limit number of turns at which magnetic saturation occurs at the desired signal current value, and an element in which this inductor 1 is combined in parallel with resistor 2 is used as a unit element, thereby realizing the practical application of a noise attenuator that can withstand the desired current of a power line, etc. In addition, the disclosure states that "the limit number of turns at which magnetic saturation occurs is determined by the value of the current flowing through the conductor line, and is not uniquely determined, but is adjusted according to the current value" (paragraph 0040). In other words, this invention keeps the number of turns of the conductor wire wound around the filter core at a level that does not cause magnetic saturation, but this conventional technology is only suitable for currents on the order of those found in the power lines of communications equipment, and cannot be used as a noise filter in circuits through which much larger currents flow. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-125426 A [Patent Document 2] JP 2011-192825 A [Patent Document 3] JP 2010-130368 A Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, an object of the present invention is to provide an inductor that uses a magnetic core and is easy to handle, that does not become magnetically saturated even when used as a noise countermeasure in a circuit through which an extremely large current not previously observed, that is, a current of several hundred amperes to more than one thousand amperes, flows, and that can effectively filter normal mode noise, and a noise filter using the same. [Means for solving the problem]

[0010] The present invention includes the following aspects. [1] A noise filter inductor having one input terminal and one output terminal, in which a conductor is split into multiple conductors between the two terminals, and each of the multiple conductors passes through a magnetic core. [2] An inductor as described in [1], in which the conducting wire passing through the magnetic core is wound around the core one or more times. [3] An inductor as described in [1], wherein the sum of the currents flowing through the multiple conductors between the input terminal and the output terminal causes magnetic saturation when they pass through one core, but the core and the multiple conductors are configured so that magnetic saturation does not occur even when each of the divided currents of the multiple conductors passes through its respective core. [4] An inductor as described in [1], in which the conductor wound around a single core is further divided into multiple conductors. [5] A noise filter that removes normal mode and / or common mode noise by connecting line-to-line and line-to-ground capacitors to a plurality of inductors according to [1] to [4]. [6] A noise filter according to [5], comprising an even number of inductors and further comprising a common mode winding core through which a set of the multiple conductors with opposite current directions passes, thereby forming a core for common mode noise.

[0011] The inventors of the present application recognized that in order to effectively block normal mode noise, it is necessary to maintain the necessary inductance without causing magnetic saturation, and arrived at the following configuration.

[0012] Large current normal mode inductors prevent saturation by dividing the current into gapped cores in parallel, but connecting the cores in parallel or inserting a gap reduces the inductance. However, winding wire around the core makes it possible to increase the inductance value by the square of the number of turns, making it possible to maintain the required inductance in normal mode even with large currents. In other words, even if the sum of the currents flowing through the inductor of the present invention is large enough to magnetically saturate a single core, if this current is divided into multiple conductors and an inductor annular core is provided for each conductor, the current passing through the holes in each annular core can be kept to a level that does not reach magnetic saturation of each annular core, and by winding the conductor multiple times around the annular core to compensate for the reduced composite inductance, magnetic saturation is not caused and the noise filtering effect of the core is not hindered. Furthermore, since the sum of the currents flowing through the multiple conductors is the desired large current, the annular core's noise blocking effect effectively acts as a noise filter, even in a conductor through which a large current flows.

[0013] Furthermore, the characteristics of the core as a noise filter vary depending on its material, shape, dimensions, whether or not a gap is provided in the core, the total magnetic reluctance of the core when a gap is provided, and the overall magnetic permeability of the core. Therefore, by using the most suitable core in accordance with the overall performance requirements that the inductor of the present invention is to exhibit, a noise filter inductor having the desired characteristics can be constructed.

[0014] The noise blocking effect on the conductor passing through the hole in the annular core is that the core and conductor form an inductor, and the noise current is limited by the reactance of high-frequency noise due to the reactance and resistance components of the inductor's impedance, and by the energy consumption effect caused by the reversal of the magnetic moment of the magnetic material that makes up the core, and each has different frequency characteristics.

[0015] Furthermore, by providing a gap in the core, the magnetic flux density generated in response to the magnetomotive force generated by the current flowing through the conductor passing through the hole in the core is reduced by increasing the magnetic resistance of the magnetic circuit, so the saturation current value at which magnetic saturation occurs can be increased. However, this reduces the magnetic loss by the same amount, so the noise current limiting effect due to the energy consumption effect is reduced.

[0016] Also, if magnetic saturation is prevented by putting a gap in the core, the wire or busbar used for large currents requires a large cross-sectional area, but it is not easy to wind it around the core. Therefore, the required cross-sectional area can be obtained by dividing the wire or busbar into smaller cross-sectional areas.

[0017] In addition, in the structure in which the conductor is wound around the core, in addition to the conductor passing through the core without any windings, it is also possible for the conductor to be wound around the core once, twice, three times, etc., and then connected to both terminals of the inductor. By winding in this manner, the range of adjustment of the inductance value is wider, making it easier to manufacture one with the desired characteristics.

[0018] It is also possible to create a circuit that adds capacitors and common mode cores in addition to normal mode cores to create a filter that can handle noise conditions. These addition methods can change the characteristics of the noise filter. For example, capacitors can be placed between the lines and between the ground, or between the cores, allowing for a wide variety of configurations. Effect of the Invention

[0019] According to the present invention, it is possible to provide a noise filter with a novel configuration which makes it possible to use a noise filter using a normal mode core even in circuits through which large DC currents flow, such as those found in electric vehicles and large-current power supplies, i.e., in circuits through which large currents that could not be used in noise filters using conventional cores due to magnetic saturation. The noise filter inductor of the present invention has two connection terminals, and when a large current flows between these terminals, the inductor of the present invention operates as a noise filter that performs the desired noise blocking operation, thereby effectively blocking electromagnetic radiation caused by noise from the circuit beyond the noise-blocking point, making it possible to avoid the use of conventional complex and heavy shielded cables, shielded connectors, shielded lithium-ion batteries, etc. Furthermore, in the inductor of the present invention, it is possible to adjust the filter characteristics as desired by optimizing the core and the overall structure of the inductor, such as the noise-blocking core structure, material, wire arrangement, and the presence or absence and number of windings.

[0020] Although the term "inductor" is used in this invention, this does not mean that the inductance component of impedance is used only, but rather that the term is used because the inductor acts as a low-pass filter that blocks high frequencies such as noise. It goes without saying that the emphasis is on the resistance component of impedance because of the focus on magnetic saturation, and when used in an actual circuit, the elements of resistance, induction, and capacitance are all taken into consideration. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram for explaining that 1-A is a conventional configuration that causes magnetic saturation, and 1-B is a configuration of the present invention that does not cause magnetic saturation. [Diagram 2] FIG. 2 is a schematic diagram of an inductor according to one embodiment of the present invention, in which a conductor is wound multiple times around a core. [Diagram 3] FIG. 3 is a schematic diagram of an inductor for normal mode noise according to one embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a normal mode noise filter according to one embodiment of the present invention. [Diagram 5]FIG. 5 is a schematic diagram of a noise filter according to an embodiment of the present invention, which has a common mode core.

[0022] The basic principle of the present invention is shown in Fig. 1. In the conventional configuration shown in Fig. 1-A, a conductor 1 through which a large current flows passes from an input electrode 3 to an output electrode 4 and passes through a hole in a core 2. In the present invention shown in FIG. 1-B, this conductor is divided into multiple conductors, and in the example shown, it is divided into three conductors 1a, 1b, and 1c, each of which passes through holes in cores 2a, 2b, and 2c. The three conductors are configured so that approximately equal currents flow, and in order to increase the noise blocking effect, it is important to keep the state of the multiple conductors as uniform as possible in order to improve the characteristics of the noise filter.

[0023] In the case of Fig. 1-A, the material of this core is such that when 30A passes through the hole of the core, the current causes magnetic saturation, and in the present invention of 1-B, three conductors, namely 1a, b, and 1c, through which 10A flows, are passed through the holes of three cores, namely 2a, 2b, and 2c, made of the same material. As in 1-A, which has only one conductor, one input / output electrode 3 and one output electrode 4 are provided in 1-B as well. In the present invention, if the three cores 2a, 2b, and 2c in 1-B have the same dimensions as the core 2 in 1-A, which is saturated at 30A, they will of course not saturate at 10A, but since the current is reduced to 10A even if the dimensions are smaller, it is sufficient to have dimensions that do not saturate even at 10A.

[0024] It goes without saying that the inductor of the present invention may be used in combination with a capacitor as a noise filter to enhance the noise blocking effect by providing necessary shielding and grounding. As shown in Fig. 2, the conductors 16a, 16b, 16c passing through the cores may be wound around the cores 2a1, 2b1, 2c1 multiple times, although Fig. 2 shows an example in which the conductors are wound only once. As the number of turns increases, the inductance increases, but magnetic saturation also becomes more likely to occur. Therefore, by selecting an appropriate number of turns, it becomes easier and more diverse to obtain the desired characteristics of the inductor as a whole.

[0025] As shown in Figure 3, by designing the normal mode core so that multiple conductors each have multiple windings penetrating it, the inductor of the present invention makes it possible to both adjust the inductance by the number of windings as described above and avoid saturation by dividing it into multiple conductors, and by using multiple cores, the freedom of overall shape is also increased. For example, a large current Ia flowing from a power supply to a motor, which is a drive current for the motor, flows from input electrode 3a to output electrode 4a, and a return current Ib from the motor flows from input electrode 3b to output electrode 4b. The normal mode noise current is a normal mode noise current, and is therefore a high frequency current that alternates between flowing from 3a to 4a and from 3b to 4b, or in the opposite direction.

[0026] As shown in FIG. 4, by providing capacitors Cab, Cag, and Cbg between the lines of the inductor and the ground, the inductor can be used as a noise filter.

[0027] As shown in FIG. 5, by providing a common mode core 7 in addition to the normal mode core in FIG. 4, it is also possible to use it as a filter that reduces both common mode and normal mode noise. [Explanation of symbols]

[0028] 1: Conductor 1a, 1b, 1c: multiple conductors 2: Normal mode core 2a2, 2b2, 2c2: Cores without conductor windings 2a1, 2b1, 2c1: Cores wound with conductor 3, 3a, 3b: Input electrode 4, 4a, 4b: Output electrodes 7: Common mode core Cab, Cag, Cbg: Capacitor

Claims

1. A noise filter inductor having one input terminal and one output terminal, wherein a conductor is split into multiple conductors between the two terminals, and each of the multiple conductors passes through a magnetic core.

2. 2. The inductor according to claim 1, wherein the conductive wire passing through the magnetic core is wound around the core one or more times.

3. 2. The inductor according to claim 1, wherein the core and the multiple conductors are configured such that a sum of currents flowing through the multiple conductors between the input terminal and the output terminal causes magnetic saturation when passing through one core, but magnetic saturation does not occur even when each of the divided currents of the multiple conductors passes through its respective core.

4. The inductor according to claim 1 , wherein the conductor wound around one core is further divided into a plurality of conductors.

5. A noise filter for removing normal mode and / or common mode noise by connecting a plurality of inductors according to any one of claims 1 to 4 with line-to-line and line-to-ground capacitors.

6. 6. The noise filter according to claim 5, further comprising an even number of inductors, and further comprising a common mode winding core through which the pair of conductors with opposite current directions passes, thereby forming a common mode noise core.

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