JP6825369B2 - Resonant current limiting circuit - Google Patents

Description

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

On the other hand, it is desirable that the current limiting device has as small an impedance as possible during normal operation. However, with the current limiting device alone, it may be difficult to sufficiently reduce the impedance during normal operation.

Therefore, an object of the present invention is to provide a highly reliable current limiting circuit having a simple device configuration and having reduced impedance during normal operation.

The current limiting circuit according to the present invention is a current limiting circuit that limits the current supplied from an AC power supply, and is connected to a current limiting device including a magnetic core and a coil wound around the magnetic core in series with the current limiting device. It has a connected capacitor. The magnetic characteristics of the magnetic core are such that in the first quadrant of the graph in which the first axis is the magnetic field and the second axis is the magnetic field density or magnetization, in the first magnetic field region equal to or lower than the first magnetic field strength, the magnetic field density or magnetization with respect to the magnetic field In the second magnetic field region where the differential value of is the first value and is stronger than the first magnetic field strength, the differential value of the magnetic field density or magnetism with respect to the magnetic field is a second value larger than the first value. is there. The coil and the capacitor form an LC resonance circuit that resonates in the frequency band of the AC power supply when the magnetic field applied to the magnetic core is in the first magnetic field region.

According to the present invention, when the current flowing through the coil is equal to or less than a predetermined value, the reactance is small because it operates in the first magnetic field region, while when the current flowing through the coil exceeds a predetermined value, it operates in the second magnetic field region. The reactance increases because it operates. 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, when the magnetic field applied to the magnetic 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 can be significantly reduced. In order to obtain such magnetic properties, a metamagnetic material, a permember characteristic material or a synthetic antiferromagnetic material may be used as the material constituting the magnetic core.

In the present invention, the resonance frequency of the LC resonance circuit when the magnetic field applied to the magnetic core is in the second magnetic field region is preferably 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 more effective current limiting operation.

As described above, according to the present invention, it is possible to provide a highly reliable current limiting circuit having a simple device configuration and having reduced impedance during normal operation.

FIG. 1 is a circuit diagram of an electric circuit using the current limiting circuit 100 according to the embodiment of the present invention. FIG. 2 is another circuit diagram of an electric circuit using the current limiting circuit 100. FIG. 3 is a diagram showing an example of a specific configuration of the current limiting device 10. FIG. 4 is a graph showing the magnetic properties of the magnetic material used for the magnetic core 11. FIG. 5 is a graph showing the magnetic properties of the magnetic material used for the magnetic core 11, 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 10 and the inductance L. FIG. 7 is a graph showing the relationship between the voltage V applied to the coil 12 and the current I flowing through the coil 12. FIG. 8 is another graph showing the magnetic properties of the magnetic material used for the magnetic core 11. FIG. 9 is a graph showing the differential values of the characteristics shown in FIG. FIG. 10 is a graph showing the double derivative values of the characteristics shown in FIG. FIG. 11 is a graph showing the relationship between the current I flowing through the coil 12 and the B / H value. FIG. 12 is a simulation result showing a voltage waveform applied to the load 30. FIG. 13 is a simulation result showing the current waveform flowing through the current limiter 10. FIG. 14 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.

FIG. 1 is a circuit diagram of an electric circuit using the current limiting circuit 100 according to the embodiment of the present invention.

The electric circuit shown in FIG. 1 includes a current limiting circuit 100 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 limiting circuit 100 according to the present embodiment 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. 2, 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 in a state where the large current is suppressed by the current limiting circuit 100.

As shown in FIGS. 1 and 2, the current limiting circuit 100 according to the present embodiment constitutes an LC resonance circuit in which a reactor type current limiting device 10 and a capacitor 50 are connected in series. The resonance frequency of the LC resonance circuit during normal operation is set in the frequency band of the AC power supply 20, and therefore, the impedance of the current limiting circuit 100 during normal operation is very small. The resonance frequency of the LC resonant circuit does not have to be exactly the same as the frequency of the AC power supply 20, but it is set near the frequency of the AC power supply 20 so that the impedance of the current limiting circuit 100 during normal operation is sufficiently small. There is a need. On the other hand, it is preferable that the resonance frequency of the LC resonance circuit at the time of an abnormality in which a short circuit accident occurs is different from the frequency band of the AC power supply 20.

The current limiter 10 is a simple reactor. Although the details will be described later, 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. Moreover, as described above, since the LC resonance circuit resonates during normal operation, 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 occurs spontaneously in response to a change in the current I. Therefore, an element for detecting the current value. Etc. are unnecessary.

FIG. 3 is a diagram showing an example of a specific configuration of the current limiting device 10 used in the present embodiment.

The current limiting device 10 shown in FIG. 3 is composed of a toroidal type magnetic core 11 and a coil 12 wound around the magnetic core 11. As the coil 12, it is preferable to use a coated conductive wire or the like using copper (Cu) having a low resistance value as a core material. The toroidal type magnetic core 11 constitutes a closed magnetic path, and when a current I flows through a coil 12 wound around the magnetic core 11, a magnetic flux orbiting the toroidal type magnetic core 11 is generated. However, in normal operation when the current I is equal to or less than a predetermined value, the magnetic permeability of the magnetic core 11 is sufficiently low, and therefore the reactance generated is also small. Then, when the current I exceeds a predetermined value at an abnormal time, the magnetic permeability of the magnetic core 11 sharply increases, and the reactance also sharply increases.

In order to exhibit such a phenomenon, in this embodiment, the magnetic material described in detail below is used as the material of the magnetic core 11.

FIG. 4 is a graph showing the magnetic properties of the magnetic material used for the magnetic core 11. 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, is magnetized. Shows M. In FIG. 4, reference numeral A indicates the magnetic characteristics of the magnetic core 11, 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 reference numeral 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 general ferromagnetic materials, the magnetic material used for the magnetic core 11 in this embodiment is in the low magnetic field region, as indicated by reference numeral A in the first quadrant (I) and the third quadrant (III) of the graph. Is hardly magnetized due to its low magnetic permeability, and is easily magnetized due to its high magnetic permeability in the medium magnetic field region, and magnetic saturation occurs in the strong magnetic field region, and is hardly magnetized beyond that. 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 10 using the magnetic material can be used repeatedly, and is automatically restored after the current limiting operation is completed.

FIG. 5 is a graph showing the magnetic properties of the magnetic material used for the magnetic core 11, and shows only the first quadrant (I).

To explain the magnetic characteristics of the magnetic core 11 more specifically with reference to FIG. 5, when the magnetic field is increased from the state where there is no magnetic field H, in the region up to the first magnetic field strength H1 (first magnetic field region MF1), The magnetic permeability is low, so the increase in magnetization M is small. The slope of the graph, that is, the differential value of the magnetization M with respect to the magnetic field H, is linked to 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 magnetization M 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 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.

On the contrary, when the magnetic field is weakened from the third magnetic field region MF3 and falls below the third magnetic field strength H3, the magnetic permeability increases again in the region up to the fourth magnetic field strength H4. Then, when it falls below the fourth magnetic field strength H4, the magnetic permeability decreases, and the material behaves again as a non-magnetic material. As described above, although there is hysteresis in the first quadrant (I), there is almost no residual magnetization. Therefore, 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 magnetic core 11 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 magnetic core 11 may be a simple substance of a metamagnetic material, a permember characteristic material or a synthetic antiferromagnetic material, or may be a combination thereof, and a part of the magnetic core 11 is composed of a ferromagnetic material. It doesn't matter if it is done.

If the magnetic core 11 is 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 10. Here, the magnetic field H applied to the magnetic core 11 is determined by the structure of the coil 12 and the current I flowing through the coil 12, and when the magnetic path length is ML and the number of turns of the coil 12 is N,
H = N × I / ML
Defined in.

FIG. 6 is a graph showing the relationship between the current I flowing through the coil 12 of the current limiting device 10 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 magnetic core 11 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 magnetic core 11 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 10 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 magnetic core 11 is in the first magnetic field region MF1 and the magnetic permeability is sufficiently low. As a result, the current limiter 10 has almost no load on the electric circuit. Here, when the magnetic permeability of the magnetic core 11 in the first magnetic field region MF1 is μ1 and the cross-sectional area of the magnetic core 11 is S, the inductance L1 in the first magnetic field region MF1 is
L1 = μ1 × N ² × S / ML
Defined in.

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 10 rapidly increases to L2 (> L1). This is because when the current I flowing through the coil 12 exceeds the first current value I1, the magnetic core 11 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 10, and when the current I flowing through the coil 12 exceeds the first current value I1, the inductance of the current limiter 10 sharply increases. As a result, when a current exceeding the first current value I1 flows through the electric circuit, the current limiting device 10 spontaneously starts the current limiting operation. Here, when the magnetic permeability of the magnetic core 11 in the second magnetic field region MF2 is μ2, the inductance L2 in the second magnetic field region MF2 is
L2 = μ2 × N ² × S / ML
Defined in.

Then, when the current I flowing through the coil 12 exceeds the second current value I2, the inductance value of the current limiting device 10 sharply decreases to L3 (<L2). This is because when the current I flowing through the coil 12 exceeds the second current value I2, the magnetic core 11 becomes the third magnetic field region MF3.

FIG. 7 is a graph showing the relationship between the voltage V applied to the coil 12 and the current I flowing through the coil 12. In the graph shown in FIG. 7, when the current I flowing through the coil 12 is equal to or less than the first current value I1, the impedance Z1 indicated by the inclination of the graph is low, and the current I flowing through the coil 12 has the first current value I1. When it exceeds, the impedance Z2 is shown to increase.

As described above, in the current limiting device 10 used in the present embodiment, since the magnetic core 11 has the magnetic characteristics shown in FIGS. 4 and 5, the current I flowing through the coil 12 is equal to or less than the first current value I1. In some cases, the load is hardly applied, but when the current I flowing through the coil 12 exceeds the first current value I1, the current limiting operation can be performed by a rapid increase in the inductance. In the graphs shown in FIGS. 4 and 5, the vertical axis is the magnetization M, but the same relationship holds even if the vertical axis is replaced with the magnetic flux density B.

FIG. 8 is another graph showing the magnetic characteristics of the magnetic material used for the magnetic core 11. The horizontal axis, which is the first axis, shows the magnetic field H, and the vertical axis, which is the second axis, shows the magnetic flux density B. ..

As shown in FIG. 8, even when the vertical axis is replaced with the magnetic flux density B, the magnetic characteristics of the magnetic core 11 draw a similar characteristic curve in the first quadrant (I) of the graph. That is, the inclination is small in the first magnetic field region MF1 which is a low magnetic field, the inclination becomes sharply large in the second magnetic field region MF2 which is a medium magnetic field, and the inclination is large in the third magnetic field region MF3 which is a strong magnetic field. Becomes smaller again. Further, also in the graph shown in FIG. 8, the characteristic curve showing the magnetic characteristics of the magnetic core 11 substantially passes through the origin, and even if it does not pass exactly through the origin of the graph, the vicinity of the origin on the horizontal axis or the vertical axis Pass.

FIG. 9 is a graph showing the differential value of the characteristic shown in FIG. 8, and FIG. 10 is a graph showing the double differential value of the characteristic shown in FIG. The characteristics shown in FIG. 9 correspond to the differential magnetic permeability of the magnetic material constituting the magnetic core 11.

As shown in FIG. 9, when the characteristic shown in FIG. 8 is differentiated once, the differential value becomes maximum in the second magnetic field region MF2. In the first magnetic field region MF1 and the third magnetic field region MF3, the differential value remains small. Then, as shown in FIG. 10, when the characteristic shown in FIG. 8 is differentiated twice, the twice differential value is inverted from a positive value to a negative value in the second magnetic field region MF2. In the first magnetic field region MF1 and the third magnetic field region MF3, the second derivative value is almost zero. As described above, the magnetic material used for the magnetic core 11 has a feature that when the magnetic flux density B is differentiated twice with respect to the magnetic field H, the twice differential value is inverted from a positive value to a negative value.

FIG. 11 is a graph showing the relationship between the current I flowing through the coil 12 and the B / H value. The B / H value corresponds to the average magnetic permeability.

As shown in FIG. 11, when the current I flowing through the coil 12 is equal to or less than the first current value I1, the B / H value (average magnetic permeability) is low and there is almost no change in the electric circuit. The effect on is small. On the other hand, when the current I flowing through the coil 12 exceeds the first current value I1, the B / H value (average magnetic permeability) sharply increases. After that, when the current I flowing through the coil 12 exceeds the second current value I2, the B / H value (average magnetic permeability) gradually decreases. This is because the magnetic core 11 is magnetically saturated in the third magnetic field region MF3.

As described above, examples of the magnetic material constituting the magnetic core 11 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 limiting device 10.

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 10 T, the current limiter 10 using this as the material of the magnetic core 11 includes a power system, a large-capacity capacitor circuit, and a power source. Applications for large currents such as transformer circuits 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 10. Therefore, even if an antiferromagnetic material is used as the material of the magnetic core 11, it is practically difficult to make it function as a current limiter.

The metamagnetic materials are paramagnetic ferromagnetic transition type (PM-FM transition type) that transitions from paramagnetism to ferromagnetism by a magnetic field, and 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 10 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 10 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-based 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 bar, Mo permin bar, super permin bar, isopalm, and senpalm. 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 a permember characteristic material is used, the first magnetic field strength H1 is 1/100 to 1/1000 of that of the metamagnetic material. Therefore, if this is used as the material of the magnetic core 11, a current limiter for low power can be constructed. It becomes possible to do.

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 it is used as the magnetic core 11. 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 of the permember characteristic material during normal operation (that is, the first magnetic field region MF1) has a magnetic permeability of 10 to 100 times or more that of the metamagnetic material, the permeability characteristic material is used as the material of the magnetic core 11. The current limiter 10 using the 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 magnetic core 11, a current limiter for medium power is used. Can be configured.

As described above, the current limiting device 10 used in the present embodiment has a coil 12 wound around a magnetic core 11 made of 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 LC resonance circuit is formed by connecting the current limiter 10 and the capacitor 50 in series, it is possible to make the impedance during normal operation extremely small. Become.

12 and 13 are operation waveform diagrams of the current limiting circuit 100 according to the present embodiment, FIG. 12 shows a voltage waveform applied to the load 30, and FIG. 13 shows a current waveform flowing through the current limiting device 10. There is. Both FIGS. 12 and 13 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. 12, 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. 14 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. 14, 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, if the current limiting circuit 100 according to the present embodiment is used, the reactance of the current limiting device 10 rises instantaneously when a short circuit accident occurs, so that the increase in current is suppressed. Moreover, if the resonance frequency when the magnetic field applied to the magnetic core 11 is in the second magnetic field region MF2 is different from the frequency band of the AC power supply 20, the resonance operation stops at the same time as the short circuit accident occurs, so that the impedance Can be further enhanced. As a result, by using the current limiting circuit 100 according to the present embodiment, it is possible to prevent damage to system equipment and circuit elements even when a short circuit accident occurs.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. It goes without saying that it is included in the range.

For example, the current limiting device 10 used in the above embodiment has a configuration in which the coil 12 is wound around a toroidal type magnetic core 11, but the current limiting device according to the present invention is not limited thereto. Therefore, the shape of the magnetic core may be an E-type, a U-type, or an I-type other than the toroidal type. Further, the magnetic core 11 may be provided with a magnetic gap. The coil 12 is not limited to the coated lead wire using copper (Cu) as the core material, and a superconductor may be used.

10 Current limiter 11 Magnetic core 12 Coil 20 AC power supply 30 Load 40 Circuit breaker 50 Capacitor 100 Current limit circuit

Claims (3)

A current limiting circuit that limits the current supplied from an AC power supply.
A current limiter containing a magnetic core and a coil wound around the magnetic core,
With a capacitor connected in series with the current limiter,
The magnetic characteristics of the magnetic core are such that in the first quadrant of the graph in which the first axis is the magnetic field and the second axis is the magnetic field density or magnetization, in the first magnetic field region equal to or lower than the first magnetic field strength, the magnetic field density or magnetization with respect to the magnetic field In the second magnetic field region where the differential value of is the first value and is stronger than the first magnetic field strength, the differential value of the magnetic field density or magnetism with respect to the magnetic field is a second value larger than the first value. Yes,
The coil and the capacitor form a resonance type current limiting circuit that resonates in the frequency band of the AC power supply when the magnetic field applied to the magnetic core is in the first magnetic field region. circuit. The resonance type limiting current according to claim 1, wherein the resonance frequency of the LC resonance circuit when the magnetic field applied to the magnetic core is in the second magnetic field region is different from the frequency band of the AC power supply. circuit. The resonance type current limiting circuit according to claim 1 or 2, wherein the magnetic core includes a metamagnetic material, a permember characteristic material, or a synthetic antiferromagnetic material.

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