JP6760085B2 - Current limiter and resonance type current limit circuit equipped with it - Google Patents

Description

The present invention relates to a current limiting device and a resonance type current limiting circuit including the same, and more particularly to a reactance type current limiting device and a resonance type current limiting circuit including the reactance type current limiting device.

When a short-circuit accident occurs in an electric power system or an electric circuit, a large current flows instantly at the short-circuited part, and this current may damage the system equipment or circuit elements, or even cause a fire. A current limiter has been conventionally known as a device for suppressing such a large current when a short circuit accident occurs. Demand for current limiters is expected to increase in the future as the power capacity increases and distributed power sources become more widespread in recent years.

Specific configurations of the current limiting device are described in, for example, Patent Documents 1 to 4. The current limiters described in Patent Documents 1 and 2 have a configuration in which a reactor is connected to a bridge circuit including a thyristor and a diode. Further, the current limiter described in Patent Document 3 has a configuration in which a series resonance circuit and a parallel resonance circuit are combined. Further, the current limiter described in Patent Document 4 has a configuration in which a saturable DC reactor is magnetically biased by using a DC power supply.

Japanese Unexamined Patent Publication No. 49-50448 Japanese Unexamined Patent Publication No. 9-285012 Japanese Unexamined Patent Publication No. 2010-17016 JP-A-2002-291150

However, the current limiters described in Patent Documents 1 to 4 have a large number of elements, and the device configuration is complicated. In particular, the current limiter described in Patent Document 3 requires a separate filter circuit for suppressing noise, which further complicates the circuit configuration. Further, the current limiter described in Patent Document 4 always requires a DC power supply for applying a magnetic bias, and has a problem that it does not function as a current limiter when the DC power supply is lost.

As described above, since the conventional current limiter has a complicated device configuration, there is a problem that it is difficult to secure reliability and a heavy maintenance burden. Moreover, it is difficult to obtain a sufficient response speed due to the complexity of the device configuration.

Therefore, an object of the present invention is to provide a highly reliable reactance type current limiting device having a simple device configuration and a resonance type current limiting circuit including the reactance type current limiting device.

The current limiting device according to the present invention includes a magnetic core and a coil wound around the magnetic core, and the magnetic core is different from the first core containing the first magnetic material and the first magnetic material. The first magnetic material includes a second core containing two magnetic materials, the first magnetic material is a ferromagnetic material, and the magnetic properties of the second magnetic material are such that the first axis is a magnetic field and the second axis is a magnetic flux density. Alternatively, in the first quadrant of the graph as magnetism, in the first magnetic field region equal to or lower than the first magnetic field strength, the magnetic flux density or the differential value of magnetism with respect to the magnetic field is the first value, which is higher than the first magnetic field strength. The strong second magnetic field region is characterized in that the differential value of the magnetic flux density or magnetism with respect to the magnetic field is a second value larger than the first value.

According to the present invention, the reactance is small because the second core operates in the first magnetic field region when the current flowing through the coil is equal to or less than a predetermined value, while the reactance is small when the current flowing through the coil exceeds a predetermined value. The reactance is increased because the core of 2 operates in the second magnetic field region. As a result, when the current is equal to or less than the predetermined value, the current limiting operation can be performed when the current exceeds the predetermined value without substantially causing a load on the power system or the electric circuit. Moreover, since it has a simple device configuration in which a coil is wound around a magnetic core, it is possible to provide a low-cost and highly reliable current limiter. Further, since the first core is made of a ferromagnetic material, the magnetic flux can be concentrated on the second core. As the second magnetic material, a metamagnetic material, a permember characteristic material or a synthetic antiferromagnetic material may be used.

In the present invention, it is preferable that the first core has a gap that divides the magnetic path, and the second core is inserted into the gap. According to this, since most of the magnetic flux orbiting the magnetic core passes through the second core, the amount of change in inductance is sufficient depending on whether the current flowing through the coil is below the predetermined value or exceeds the predetermined value. It becomes possible to secure it.

In this case, it is preferable that the first core has a shape in which the cross section increases as the distance from the surface in contact with the second core increases. According to this, it is possible to concentrate a uniform magnetic flux on the second core while preventing magnetic saturation of the first core. Further, in this case, it is also preferable that the connection portion of the first core in contact with the second core is made of another ferromagnetic material having a saturation magnetic flux density higher than that of the ferromagnetic material. According to this, it becomes possible to prevent the magnetic saturation of the first core more effectively.

In the present invention, the first core is composed of a combination of two E-type cores having one middle leg and two side legs, and the gap is a portion where the middle legs of the two E-type cores face each other. It is preferably formed in. According to this, the magnetic flux can be more effectively concentrated on the second core.

Further, the resonance type current limiting circuit according to the present invention is a current limiting circuit that limits the current supplied from the AC power supply, and the above-mentioned current limiting device and a capacitor connected in series with the current limiting device are connected. The coil and the capacitor are characterized in that they form an LC resonance circuit that resonates in the frequency band of the AC power supply when the magnetic field applied to the second core is in the first magnetic field region. To do.

According to the present invention, when the magnetic field applied to the second core is in the first magnetic field region, the LC resonance circuit resonates in the frequency band of the AC power supply, so that the impedance during normal operation is significantly reduced. It can be (ideally zero).

In the present invention, it is preferable that the resonance frequency of the LC resonance circuit when the magnetic field applied to the second core is in the second magnetic field region is different from the frequency band of the AC power supply. According to this, since the impedance at the time of abnormality becomes larger, it becomes possible to perform a more effective current limiting operation.

As described above, according to the present invention, it is possible to provide a highly reliable reactance type current limiting device having a simple device configuration and a resonance type current limiting circuit including the reactance type current limiting device.

FIG. 1 is a perspective view showing the configuration of the current limiting device 10A according to the first embodiment of the present invention. FIG. 2 is a perspective view for explaining the structure of the magnetic core 11A. FIG. 3 is a cross-sectional view for explaining the structure of the magnetic core 11A. FIG. 4 is a graph showing the magnetic properties of the magnetic material used for the second core 22. FIG. 5 is a graph showing the magnetic properties of the magnetic materials used for the first and second cores 21 and 22, and shows only the first quadrant (I). FIG. 6 is a graph showing the relationship between the current I flowing through the coil 12 of the current limiting device 10A and the inductance L. FIG. 7 is a simulation result showing the magnetic flux density distribution of the magnetic core 11A when a current is passed through the coil 12. FIG. 8 is a cross-sectional view showing the structure of the current limiting device 10X according to a comparative example. FIG. 9 is a perspective view showing the configuration of the magnetic core 11B used in the second embodiment of the present invention. FIG. 10 is a cross-sectional view showing the configuration of the current limiting device 10C according to the third embodiment of the present invention. FIG. 11 is a circuit diagram of an electric circuit using the current limiter 10. FIG. 12 is another circuit diagram of an electric circuit using the current limiter 10. FIG. 13 is still another circuit diagram of an electric circuit using the current limiter 10. FIG. 14 is a simulation result showing a voltage waveform applied to the load 30. FIG. 15 is a simulation result showing the current waveform flowing through the current limiter 10. FIG. 16 is a simulation result showing a current waveform flowing through the linear reactor when a normal linear reactor is used instead of the current limiting device 10.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a perspective view showing the configuration of the current limiting device 10A according to the first embodiment of the present invention.

As shown in FIG. 1, the current limiting device 10A according to the present embodiment is composed of a magnetic core 11A and a coil 12 wound around the magnetic core 11A. The magnetic core 11A is provided with two through holes, and the coil 12 is arranged in the through holes. As the coil 12, it is preferable to use a coated lead wire or the like using copper (Cu) having a low resistance value as a core material.

2 and 3 are views for explaining the structure of the magnetic core 11A, FIG. 2 is a perspective view, and FIG. 3 is a cross-sectional view.

As shown in FIGS. 2 and 3, the magnetic core 11A is composed of a first core 21 and a second core 22. The first core 21 has a structure in which two E-type cores 21a and 21b are combined, and the second core 22 is placed in a gap formed in a portion where the middle legs of the E-type cores 21a and 21b face each other. It has been inserted. The two side legs provided on the E-type core 21a and the two side legs provided on the E-type core 21b are connected to each other without a gap. As a result, the magnetic core 11A forms a closed magnetic path, and the magnetic flux orbiting the closed magnetic path always passes through the second core 22. The cross-sectional area of the first core 21 (area in the direction perpendicular to the magnetic flux) is substantially equal to the cross-sectional area of the second core 22 at the connection surface with the second core 22, but in other regions, the first core 21 has a cross section. It is larger than the cross section of the core 22 of 2, which prevents the magnetic saturation of the first core 21. The middle legs of the E-shaped cores 21a and 21b have a shape in which the cross-sectional area increases as the distance from the surface in contact with the second core 22 increases, thereby preventing magnetic saturation of the first core 21 while preventing magnetic saturation. The magnetic flux density given to the second core 22 is increased.

The first magnetic material constituting the first core 21 is made of a ferromagnetic material. The type of the ferromagnetic material is not particularly limited, but it is preferable to use a soft magnetic material having a high magnetic permeability such as permalloy or an electromagnetic steel plate. On the other hand, the second magnetic material constituting the second core 22 has a low magnetic permeability when the magnetic field strength is equal to or less than a predetermined value, and exceeds the predetermined magnetic field strength, contrary to the soft magnetic material. It has the property that the magnetic permeability increases sharply. As a result, when the current flowing through the coil 12 is equal to or less than a predetermined value, the second core 22 acts as a magnetic gap of the magnetic core 11A, so that the magnetic permeability of the entire magnetic core 11A is relatively low and the reactance generated is also generated. small. When the current flowing through the coil 12 exceeds a predetermined value, the magnetic permeability of the second core 22 rapidly increases, so that the magnetic gap disappears. As a result, the magnetic permeability of the entire magnetic core 11A sharply increases, and the reactance also sharply increases. That is, the current limiting device 10A according to the present embodiment spontaneously starts the current limiting operation when the current flowing through the coil 12 exceeds a predetermined value.

In order to exhibit such a phenomenon, in the present embodiment, a magnetic material described in detail below is used as the material of the second core 22.

FIG. 4 is a graph showing the magnetic characteristics of the magnetic material used for the second core 22, the horizontal axis (X axis) which is the first axis shows the magnetic field H, and the vertical axis (Y axis) which is the second axis. ) Indicates the magnetization M. In FIG. 4, reference numeral A indicates the magnetic characteristics of the second core 22, reference numeral SM indicates the magnetic characteristics of a general soft magnetic material, and reference numeral HM indicates the magnetic characteristics of a general hard magnetic material.

As shown by reference numeral SM in FIG. 4, a general soft magnetic material has high magnetic permeability in a low magnetic field region and is easily magnetized, while magnetic saturation occurs when the magnetic field strength exceeds a predetermined value, and more than that. It exhibits the property of being hardly magnetized. In other words, in the magnetic field region where the magnetism is not saturated, the differential value of the magnetization M with respect to the magnetic field H is large, and in the magnetic field region where the magnetism is saturated, the differential value of the magnetization M with respect to the magnetic field H is small. Further, since a general soft magnetic material has no hysteresis or has a very small hysteresis, the characteristic curve indicated by the symbol SM passes through the origin of the graph or its vicinity. Therefore, the characteristic curve represented by the reference numeral SM appears in the first quadrant (I) and the third quadrant (III) of the graph, and does not substantially appear in the second quadrant (II) and the fourth quadrant (IV).

As shown by the reference numeral HM in FIG. 4, a general hard magnetic material has a large hysteresis, and the magnetized state is maintained even when the magnetic field is zero. Therefore, the characteristic curve represented by the symbol HM appears in all of the first quadrant (I) to the fourth quadrant (IV) of the graph.

In contrast to these common ferromagnetic materials, the magnetic material used for the second core 22 in this embodiment is low, as indicated by reference numeral A in the first quadrant (I) and third quadrant (III) of the graph. In the magnetic field region, the magnetic permeability is low, so it is hardly magnetized. In the medium magnetic field region, the magnetic permeability is high and it is easily magnetized. Furthermore, in the strong magnetic field region, magnetic saturation occurs, and it is hardly magnetized beyond that. Is shown. Depending on the material selected, there is a slight hysteresis in the first quadrant (I) and the third quadrant (III), but the residual magnetization is zero or very small, so the characteristic curve indicated by reference numeral A is substantially a graph. Pass through the origin of. Even if the characteristic curve indicated by reference numeral A does not pass exactly through the origin of the graph, it passes near the origin on the horizontal axis or the vertical axis. This means that the same magnetic properties can be obtained regardless of whether the magnetic material is in the initial state or in the state after repeatedly applying a magnetic field. Therefore, the current limiting device 10A using the magnetic material can be used repeatedly, and automatically recovers after the current limiting operation is completed.

FIG. 5 is a graph showing the magnetic properties of the magnetic materials used for the first and second cores 21 and 22, and shows only the first quadrant (I). The horizontal axis (X-axis), which is the first axis, indicates the magnetic field H, and the vertical axis (Y-axis), which is the second axis, indicates the magnetic flux density B. In FIG. 5, reference numeral A indicates the magnetic characteristics of the second core 22, and reference numeral B indicates the magnetic characteristics of the first core 21. In each case, for convenience, it represents a state without hysteresis.

To explain the magnetic characteristics of the second core 22 more specifically with reference to FIG. 5, when the magnetic field is increased from the state where there is no magnetic field H, the region up to the first magnetic field strength H1 (first magnetic field region MF1). ), The magnetic permeability is low, and therefore the increase in the magnetic flux density B is slight. The value of the magnetic flux density B at the first magnetic field strength H1 is B1. The slope of the graph, that is, the differential value of the magnetic flux density B with respect to the magnetic field H, indicates the magnetic permeability. The magnetic permeability in the first magnetic field region MF1 is about the same as the magnetic permeability of the non-magnetic material, and therefore behaves substantially as a non-magnetic material in the first magnetic field region MF1.

On the other hand, in the region from the first magnetic field strength H1 to the second magnetic field strength H2 (second magnetic field region MF2), the magnetic permeability increases sharply, and the value of the magnetic flux density B increases significantly. That is, as the magnetic field is increased, the magnetic permeability sharply increases with the first magnetic field strength H1 as a boundary. The value of the magnetic flux density B at the second magnetic field strength H2 is B2. The magnetic permeability in the second magnetic field region MF2 is close to the magnetic permeability of the soft magnetic material, and therefore behaves softly magnetically in the second magnetic field region MF2.

When the second magnetic field strength H2 is exceeded by further increasing the magnetic field (third magnetic field region MF3), magnetic saturation occurs, and the slope of the graph, that is, the magnetic permeability decreases again.

Further, since the magnetic material constituting the second core 22 has almost no residual magnetization, once the magnetic field H is returned to near zero, the same characteristics as those described above can be obtained again.

The magnetic material constituting the second core 22 is not particularly limited as long as it is a magnetic material having the above-mentioned magnetic properties, and examples thereof include a metamagnetic material, a permember characteristic material, and a synthetic antiferromagnetic material. .. The magnetic material constituting the second core 22 may be a simple substance of a metamagnetic material, a permember characteristic material, or a synthetic antiferromagnetic material, or may be a combination thereof.

On the other hand, the magnetic material (ferromagnetic material) constituting the first core 21 has extremely steep magnetic characteristics as shown by reference numeral B in FIG. 5, and is saturated before reaching the first magnetic field strength H1. .. The value of the magnetic flux density B when the first core 21 is magnetically saturated is B3. The value of B3 is not particularly limited as long as it is larger than B1. Although not particularly limited, in the present embodiment, the value of B3 is slightly smaller than the value of B2.

If the first and second cores 21 and 22 are made of such a magnetic material, the inductance can be greatly changed depending on the magnitude of the current I flowing through the coil 12 of the current limiting device 10A. Here, the magnetic field H applied to the second core 22 is determined by the structure of the coil 12 and the current I flowing through the coil 12, and the magnetic path length of the second core 22 is ML and the number of turns of the coil 12 is N. ,
H = N × I / ML
Defined in. This is because the magnetic flux density of the first core 21 at the first magnetic field strength H1 of the second core 22 is as low as a fraction of the magnetic flux density B1 of the second core 22, so that it is magnetically saturated. Therefore, the magnetic field strength of the first core 21 is close to zero, and it can be considered that the upper surface and the lower surface of the second core 22 are magnetically ideally short-circuited by the first core 21. Is.

FIG. 6 is a graph showing the relationship between the current I flowing through the coil 12 of the current limiting device 10A and the inductance L. Here, the current value I1 shown in FIG. 6 is a current value at which the magnetic field H applied to the second core 22 becomes the first magnetic field strength H1. Further, the current value I2 shown in FIG. 6 is a current value at which the magnetic field H applied to the second core 22 becomes the second magnetic field strength H2.

As shown in FIG. 6, when the current I flowing through the coil 12 is equal to or less than the first current value I1, the inductance value of the current limiting device 10A is L1, which is sufficiently low. This is because when the current I flowing through the coil 12 is equal to or less than the first current value I1, the second core 22 is in the first magnetic field region MF1 and the magnetic permeability is sufficiently low. As a result, the current limiter 10A has almost no load on the electric circuit.

On the other hand, when the current I flowing through the coil 12 exceeds the first current value I1, the inductance value of the current limiting device 10A sharply increases to L2 (> L1). This is because when the current I flowing through the coil 12 exceeds the first current value I1, the second core 22 becomes the second magnetic field region MF2, so that the magnetic permeability increases sharply. The first current value I1 is the operation start point of the current limiter 10A, and when the current I flowing through the coil 12 exceeds the first current value I1, the inductance of the current limiter 10A sharply increases. As a result, when a current exceeding the first current value I1 flows through the electric circuit, the current limiting device 10A spontaneously starts the current limiting operation.

Then, when the current I flowing through the coil 12 exceeds the second current value I2, the inductance value of the current limiting device 10A sharply decreases to L3 (<L2). This is because when the current I flowing through the coil 12 exceeds the second current value I2, the second core 22 becomes the third magnetic field region MF3.

FIG. 7 is a simulation result showing the magnetic flux density distribution of the magnetic core 11A when a current is passed through the coil 12. In FIG. 7, a region having a high magnetic flux density is displayed in white, and a region having a low magnetic flux density is displayed in black.

As shown in FIG. 7, when a current is passed through the coil 12, the magnetic flux density becomes higher in the portion closer to the through hole into which the coil 12 is inserted, and the magnetic flux density is highest in the portion where the second core 22 is provided. You can see that it is. Moreover, the magnetic field applied to the second core 22 is substantially uniform. Therefore, when the current flowing through the coil 12 increases, the magnetic field applied to the second core 22 increases while maintaining a uniform state. When the current flowing through the coil 12 exceeds a predetermined value, the magnetic permeability of the second magnetic material constituting the second core 22 increases at a time, and the inductance rapidly increases.

FIG. 8 is a cross-sectional view showing the structure of the current limiting device 10X according to a comparative example.

The current limiting device 10X shown in FIG. 8 has a magnetic core 11X of a toroidal type, and the entire magnetic core 11X is composed of a second magnetic material (metamagnetic material, permember characteristic material or synthetic antiferromagnetic material). When the magnetic core 11X has such a structure, when a current is passed through the coil 12X, a magnetic flux orbiting the toroidal type magnetic core 11X is generated, but the magnetic path length thereof differs depending on the radial position. That is, the magnetic path length ML1 of the magnetic flux that orbits the vicinity of the outer circumference of the magnetic core 11X is longer than the magnetic path length ML2 of the magnetic flux that orbits the vicinity of the inner circumference of the magnetic core 11X. Therefore, the magnetic field generated in the magnetic core 11X is weaker toward the outer circumference and stronger toward the inner circumference.

As a result, when the current flowing through the coil 12X increases, the magnetic field applied to the magnetic core 11X increases while maintaining the magnetic field gradient. Therefore, the magnetic permeability of the magnetic core 11X does not increase all at once, and the magnetic permeability increases. The area gradually expands from the inner peripheral side to the outer peripheral side. That is, when the magnetic core 11X shown in FIG. 8 is used, even if the current flowing through the coil 12 is increased, a portion having a high magnetic permeability and a portion having a low magnetic permeability are mixed, so that the inductance can be rapidly increased at a certain current value. Can not.

On the other hand, in the current limiting device 10A according to the present embodiment, the magnetic core 11A is composed of a combination of the first core 21 and the second core 22, and the magnetic path length of the second core 22 is uniform. As a result, a uniform magnetic flux is concentrated on the second core 22, so that the inductance can be rapidly increased when the current flowing through the coil 12 exceeds a predetermined value.

Moreover, in the magnetic core 11X shown in FIG. 8, since the magnetic path length of the second magnetic material is long, the current value required to reach the first magnetic field strength H1 is very large. In order to reduce the current value required to reach the first magnetic field strength H1, it is necessary to increase the number of turns of the coil 12X. However, when the number of turns of the coil 12X is increased, as shown in FIG. 8, the toroidal The coil 12X located at the inner diameter is wound in multiple layers, and most of the magnetic flux generated from the coil 12X wound in the upper layer (that is, the part closer to the center) passes through the space without passing through the magnetic core 11X. Resulting in. Such magnetic flux does not contribute to the increase in the magnetic field strength of the magnetic core 11X.

On the other hand, in the current limiting device 10A according to the present embodiment, since the magnetic path length of the second core 22 is short, it is possible to rapidly increase the inductance with a smaller current value while suppressing the number of turns of the coil 12. .. This means that the copper loss caused by the coil 12 is minimized.

As described above, in the current limiting device 10A according to the present embodiment, the first core 21 is composed of a combination of two E-type cores 21a and 21b, and the second core is formed in the gap provided between the middle legs. Since the 22 has an inserted structure, the current value required for the second core 22 to reach the first magnetic field strength H1 can be reduced, and the overall transparency of the second core 22 can be reduced. It is possible to increase the magnetic coefficient at once. As a result, it is possible to sufficiently secure the ratio (L2 / L1) of the inductance during normal operation and the inductance during abnormal operation.

As described above, examples of the magnetic material constituting the second core 22 include a metamagnetic material, a permember characteristic material, and a synthetic antiferromagnetic material. Which magnetic material to use may be appropriately selected according to various characteristics (mainly the value of the first magnetic field strength H1) required for the current limiter 10A.

The metamagnetic material refers to a material that undergoes a primary phase transition from paramagnetism (PM: Paramagnetic) or antiferromagnetism (AFM: Anti-Ferromagnetic) to ferromagnetism (FM: Ferromagnetic) due to a magnetic field. The first-order phase transition due to a magnetic field means that the change in magnetization with respect to the magnetic field has a discontinuous point. Since the magnetic field at which the first-order phase transition occurs in the metamagnetic material is usually a relatively large magnetic field of 1 to 10T, the current limiting device 10A using this as the material of the second core 22 includes a power system and a large-capacity capacitor circuit. , Applications for large currents such as transformer circuits for electric power are suitable. In addition, some anti-ferrometric materials also have a characteristic that the magnetic flux density B sharply increases if the magnetic field H is remarkably increased, but the magnetic field strength that causes such a change (that is, the first magnetic field strength H1) is It is extremely strong at 10 to 100 T, and it is practically impossible to create such a magnetic field by the coil 12 of the current limiting device 10A. Therefore, even if an antiferromagnetic material is used as the material of the second core 22, it is practically difficult to make it function as a current limiter.

The metamagnetic materials are the paramagnetic ferromagnetic transition type (PM-FM transition type) that transitions from normal magnetism to ferromagnetism by a magnetic field and the antiferromagnetic ferromagnetic transition type (AFM-FM) that transitions from antiferromagnetism to ferromagnetism. It is classified as a metastatic type). In the PM-FM transition type, since the primary phase transition occurs only in the vicinity of the Curie temperature, the operating temperature of the current limiter 10A is also limited to the vicinity of the Curie temperature. On the other hand, in the AFM-FM transition type, the first-order phase transition occurs when the temperature is below the Neel temperature at which the antiferromagnetic state disappears, so that the current limiter 10A can be operated at a wider temperature range.

Meta Specific examples of magnetic materials, La _{(FeSi) 13} system, La _{(FeSi) 13} H system, MnAs system, Mn (AsSb) system, MnAl system, FeRh system, NiMnIn _system, Mn 3 _GAC-based, Mn 3 SnC Examples include Mn ₃ SnB materials. In particular, La _{(FeSi) 13} H system first order phase transition occurs in the vicinity of room temperature, MnAs system, Mn (AsSb) system, preferably MnAl based material, most preferably, MnAl system is AFM-FM transition type meth magnetic material It is a material. When a material that does not cause a primary phase transition near room temperature is used, it may be maintained in a temperature range where a primary phase transition occurs by using a heater or a cooling device.

Next, the permember characteristic material is a material called permin bar that exhibits special BH characteristics confirmed with a Ni 45 wt% Co 25 wt% Fe residue. Specific examples thereof include permin bars, Mo permin bars, super permin bars, isopalms, and sempalms. Further, NiZn ferrite and CoB-based amorphous materials are also mentioned as palmin bar characteristic materials.

The permember characteristic material has no hysteresis in a relatively low magnetic field and exhibits a linear BH characteristic with a small slope, and exhibits a BH characteristic with a large slope when a certain magnetic field (first magnetic field strength H1) is exceeded. When the permin bar characteristic material is used, the first magnetic field strength H1 is 1/100 to 1/1000 of the metamagnetic material. Therefore, if this is used as the material of the second core 22, the current limit for low power consumption is used. It becomes possible to construct a vessel.

Further, if the permember characteristic material is below the Curie temperature at which ferromagnetism is maintained, the magnetic permeability changes according to the magnetic field strength, so that the material can operate in a wide range of temperatures including room temperature. Further, since the magnetostrictive material has a small magnetostriction due to the application of a magnetic field, it is possible to obtain high durability when used as the second core 22. Moreover, since most of the compositions constituting the permember characteristic material are transition metals, there is an advantage that the material cost is lower than that of the metamagnetic material containing platinum group elements and rare earth elements.

Since the permeability characteristic material has a magnetic permeability of 10 to 100 times or more that of the metamagnetic material during normal operation (that is, the first magnetic field region MF1), the material of the second core 22 is used. The current limiting device 10A using the permeable characteristic material can also be used as a reactor during normal operation.

Next, the synthetic antiferromagnetic material refers to a material that exhibits antiferromagnetic properties by antiferromagnetically coupling the ferromagnetic phase and the ferromagnetic phase. Unlike antiferromagnetic materials, synthetic antiferromagnetic materials have a small antiferromagnetic coupling strength, and therefore, when a certain magnetic field (first magnetic field strength H1) is exceeded, a ferromagnetic magnetization arrangement is formed. Specific examples of the material include FeCo / Ru / FeCo thin films. When a synthetic antiferromagnetic material is used, the first magnetic field strength H1 is 1/10 to 1/100 of that of the metamagnetic material. Therefore, if this is used as the material of the second core 22, it is used for medium power. It is possible to configure a current limiter.

As described above, the current limiting device 10A according to the present embodiment has a coil 12 wound around a magnetic core 11A containing a magnetic material having the above-mentioned characteristics, and has a very simple configuration. As a result, it is possible to spontaneously and at high speed limit current operation without using active elements such as diodes and thyristors, DC power supplies, etc., which makes it possible to realize cost reduction and improvement of reliability. Become. Further, in the present embodiment, since the magnetic core 11A is composed of the combination of the first core 21 and the second core 22, it is necessary for the second core 22 to reach the first magnetic field strength H1. The current value can be lowered, and the overall magnetic permeability of the second core 22 can be increased at once.

<Second embodiment>
FIG. 9 is a perspective view showing the configuration of the magnetic core 11B used in the second embodiment of the present invention.

As shown in FIG. 9, the magnetic core 11B used in the present embodiment is the first in that the connecting portion 23 in contact with the second core 22 of the first core 21 is made of another ferromagnetic material. It is different from the magnetic core 11A used in the embodiment. Since the other configurations are the same as those of the magnetic core 11A, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

The connecting portion 23 of the first core 21 is made of a ferromagnetic material having a higher saturation magnetic flux density than the other portions. The ferromagnetic material constituting the connecting portion 23 has the magnetic characteristics indicated by reference numeral C in FIG. That is, it has extremely steep magnetic characteristics, and the value of the magnetic flux density B when magnetically saturated is B4, which is higher than the magnetic flux density B2 when the second core 22 is magnetically saturated. As a result, while the second core 22 is in the second magnetic field region MF2, that is, while the current limiting operation is being performed, the connection portion 23 is not magnetically saturated, so that a high impedance can be secured. ..

As shown in FIG. 9, since the middle leg of the first core 21 has a tapered shape in which the cross-sectional area decreases as it approaches the second core 22, the magnetic flux density is highest in this portion. However, in the magnetic core 11B used in the present embodiment, since the connection portion 23 with the second core 22 is made of a highly magnetically saturated material, the first core 21 during the current limiting operation is performed. It is possible to prevent magnetic saturation of. Moreover, since the highly magnetically saturated material is used only for a part of the first core 21, it is possible to minimize the increase in material cost.

<Third embodiment>
FIG. 10 is a cross-sectional view showing the configuration of the current limiting device 10C according to the third embodiment of the present invention.

As shown in FIG. 10, in the current limiting device 10C according to the present embodiment, the first core 21 has a toroidal structure in which two U-shaped cores 21c and 21d are combined, and between the U-shaped cores 21c and 21d. The second cores 22a and 22b are inserted into the two gaps provided, respectively. Since the other configurations are the same as those of the current limiter 10A according to the first embodiment, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

The cross-sectional area of the U-shaped cores 21c and 21d is not constant in the circumferential direction, and has a tapered shape in which the cross-sectional area is reduced at the end portion, that is, the portion in contact with the second core 22. As a result, the density of the magnetic flux orbiting the magnetic core 11C is increased in this portion, so that a uniform and high magnetic flux can be applied to the second cores 22a and 22b.

As illustrated by the present embodiment, the shape and structure of the magnetic core used in the present invention are not particularly limited, and any shape and structure can be adopted.

<Fourth Embodiment>
FIG. 11 is a circuit diagram of an electric circuit using the current limiter 10. The current limiting device 10 is the current limiting device described in each of the above-described embodiments, or a current limiting device having a modified structure thereof.

The electric circuit shown in FIG. 11 includes a current limiter 10 and a load 30 connected in series with the AC power supply 20. The AC power source 20 is, for example, a commercial power source, and the load 30 is various electric devices operated by the electric power supplied from the AC power source 20. The current limiter 10 is connected in series between the AC power supply 20 and the load 30, and plays a role of suppressing a large current flowing when the load 30 causes a short-circuit accident. As shown in FIG. 12, the circuit breaker 40 may be connected in series with the load 30. If the circuit breaker 40 is used, when the load 30 causes a short-circuit accident, the circuit breaker 40 can perform the circuit breaker operation while the large current is suppressed by the current limiting device 10.

As shown in FIGS. 11 and 12, the current limiting device 10 is a simple reactor. As described above, the reactance of the current limiter 10 is sufficiently small during normal operation when the current I is equal to or less than a predetermined value, and thus the impedance given to the electric circuit is very small. On the other hand, when the current I exceeds a predetermined value, the reactance of the current limiter 10 increases significantly. As a result, since it acts as a large impedance with respect to the AC power supply 20, an increase in the current I is suppressed. Such a change in reactance is due to a change in the magnetic field applied to the magnetic core of the reactor (principle of electromagnetic induction), and it occurs spontaneously in response to a change in the current I. Therefore, an element for detecting the current value. Etc. are unnecessary.

In order to further reduce the voltage drop caused by the reactance component during normal operation, as shown in FIG. 13, a capacitor 50 that resonates with the current limiting device 10 may be connected in series. Then, if the resonance frequency of the resonance circuit including the current limiter 10 and the capacitor 50 is matched with the frequency of the AC power supply 20, the impedance of the current limiter 10 in normal operation can be significantly reduced.

Since the current limiting device 10 according to the present embodiment is a reactor type, it is suitable for application to an AC circuit. However, since reactance has the effect of delaying the increase in current, assuming that the circuit breaker 40 that cuts off a large current is used, the current limiting device 10 according to the present embodiment is used in the DC circuit. However, it is possible to reduce the risk of exceeding the breaking capacity (maximum power value that can be broken) of the circuit breaker 40. Therefore, the current limiter 10 according to the present embodiment can also be used in a DC circuit.

14 and 15 are operation waveform diagrams of the current limiting circuit (when the circuit breaker 40 is omitted) shown in FIG. 13, FIG. 14 shows a voltage waveform applied to the load 30, and FIG. 15 is a current limiting circuit. The current waveform flowing through the vessel 10 is shown. 14 and 15 are simulation results when the AC power supply 20 is a commercial power supply (50 Hz or 60 Hz, effective voltage 100 V, maximum voltage 141 V) and a short circuit accident occurs at time t1.

As shown in FIG. 14, in the period before time t1, the maximum value of the voltage applied to the load 30 is about 141V, and the AC voltage supplied from the AC power supply 20 hardly drops to the load 30. It is applied. This is because the resonance frequency of the LC resonance circuit including the current limiter 10 and the capacitor 50 is set in the frequency band of the AC power supply 20, and the impedance at that frequency is very low. Then, when a short-circuit accident occurs at time t1, the voltage applied to the load 30 becomes almost zero, as shown in FIG. However, when a short-circuit accident occurs, the reactance of the current limiter 10 rises instantaneously, so that the increase in current is suppressed as shown in FIG.

FIG. 16 is a simulation result showing a current waveform flowing through the linear reactor when a normal linear reactor is used instead of the current limiting device 10. As shown in FIG. 16, when a normal linear reactor is used instead of the current limiting device 10, it can be seen that the current value rapidly increases when a short-circuit accident occurs at time t1.

On the other hand, in the present embodiment, when a short-circuit accident occurs, the reactance of the current limiting device 10 rises instantaneously, so that the increase in current is suppressed. Moreover, if the resonance frequency when the magnetic field applied to the second core 22 is in the second magnetic field region MF2 is different from the frequency band of the AC power supply 20, the resonance operation is stopped at the same time as the short circuit accident occurs. Therefore, the impedance can be further increased. As a result, by using the current limiter 10 according to the present embodiment, it is possible to prevent damage to the system equipment and circuit elements even when a short-circuit accident occurs.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. Needless to say, it is included in the range.

10, 10A, 10C, 10X Current limiter 11A to 11C, 11X Magnetic core 12, 12X Coil 20 AC power supply 21 First core 21a, 21b E type core 21c, 21d U type core 22 Second core 23 Connection part 30 Load 40 circuit breaker 50 capacitor

Claims (8)

A magnetic core and a coil wound around the magnetic core are provided.
The magnetic core includes a first core containing a first magnetic material and a second core containing a second magnetic material different from the first magnetic material.
The first magnetic material is a ferromagnetic material and
The magnetic properties of the second magnetic material are based on the magnetic field in the first magnetic field region of the first magnetic field strength or less in the first quadrant of the graph in which the first axis is the magnetic field and the second axis is the magnetic flux density or magnetization. In the second magnetic field region where the differential value of the magnetic flux density or the magnetization is the first value and is stronger than the first magnetic field strength, the differential value of the magnetic flux density or the magnetization with respect to the magnetic field is larger than the first value. A current limiting device characterized by having a value of 2. The current limiting device according to claim 1, wherein the first core has a gap that divides the magnetic path, and the second core is inserted into the gap. The current limiting device according to claim 2, wherein the first core has a shape in which the cross section increases as the distance from the surface in contact with the second core increases. The current limiting device according to claim 3, wherein the connection portion of the first core in contact with the second core is made of another ferromagnetic material having a saturation magnetic flux density higher than that of the ferromagnetic material. .. The first core consists of a combination of two E-shaped cores with one middle leg and two side legs.
The current limiting device according to any one of claims 2 to 4, wherein the gap is formed in a portion where the middle legs of the two E-shaped cores face each other. The current limiting device according to any one of claims 1 to 5, wherein the second magnetic material is made of a metamagnetic material, a permember characteristic material, or a synthetic antiferromagnetic material. A current limiting circuit that limits the current supplied from an AC power supply.
The current limiter according to any one of claims 1 to 6 and
With a capacitor connected in series with the current limiter,
The coil and the capacitor form a resonance circuit that resonates in the frequency band of the AC power supply when the magnetic field applied to the second core is in the first magnetic field region. Type limiting circuit. The resonance according to claim 7, wherein the resonance frequency of the LC resonance circuit when the magnetic field applied to the second core is in the second magnetic field region is different from the frequency band of the AC power supply. Type limiting circuit.