DC surge protector

Abstract

We provide a DC surge protection device with high lightning protection performance. [Solution] The DC surge protection device uses a wireless power supply coil to output DC that is electrically isolated from the DC input. The DC surge protection device includes a conversion circuit 12 that converts the DC power received by input terminals 11a and 11b into AC power, an input-side power supply coil 13 that receives the output of the conversion circuit 12, an output-side power supply coil 21 positioned opposite the input-side power supply coil 13, and a rectifier circuit 22 that converts the output of the output-side power supply coil 21 into DC power. The output of the rectifier circuit 22 is supplied to the protected equipment from output terminals 23a and 23b.

Description

Technical Field

[0001] The present invention relates to a technique for protecting equipment from lightning surges.

Background Art

[0002] Currently, as devices for protecting equipment from lightning surges, there are lightning-resistant transformers and SPDs (Surge Protective Devices). Lightning-resistant transformers are used for AC (alternating current) lightning protection and have a shielding function (30 kV) for surge intrusion routes due to high insulation performance and high surge attenuation performance (attenuating lightning surges to 1 / 100 to 1 / 10,000). Since lightning-resistant transformers have higher lightning protection performance than SPDs, lightning-resistant transformers are often used instead of SPDs in lightning protection measures for important equipment.

[0003] Also, for DC (direct current) lightning protection measures, SPDs are used for power supplies and control power supplies.

[0004] In Patent Document 1, a lightning protection device for direct current is disclosed. This direct current lightning protection device includes a conversion circuit that converts direct current power into alternating current power, a lightning-resistant transformer that receives the output of the conversion circuit on the primary side, and a rectification circuit connected to the secondary side of the lightning-resistant transformer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] If there were a device with the same high insulation performance and high surge attenuation performance as AC surge protectors for DC circuits, it would be possible to implement surge protection measures that are more effective than SPDs in DC circuits. However, surge protectors only exist for AC circuits, and no surge protectors exist for DC circuits. In addition, SPDs are used for power supply and control power supply surge protection for DC, but there are devices that cannot be protected by the surge voltage suppressed by SPDs.

[0007] One method of DC isolation is the use of isolated DC-DC converters. However, the isolation performance of DC-DC converters is, for example, around 1.5kV DC (for 1 minute) between input and output, and 5000V DC (for 1 minute) between output chassis, and they do not have high isolation performance against impulses such as lightning surges.

[0008] Furthermore, the DC lightning protection device described in Patent Document 1 had the problem that its efficiency was not necessarily sufficiently high.

[0009] The performance requirements for DC surge protection devices are as follows: • Outputs DC with high efficiency in response to DC input. • Very large surge attenuation • Very high impulse withstand voltage between input / output, input-to-ground, and output-to-ground. • Very high dielectric strength between input and output, and between input and ground, and between output and ground. • High voltage, large capacity In view of the above-mentioned problems, the present invention provides a DC surge protection device with high lightning protection performance. [Means for solving the problem]

[0010] One aspect of the present invention is a DC lightning protection device provided between a DC power supply and a protected device, comprising: positive and negative input terminals for receiving DC power from the DC power supply; a conversion circuit for converting the DC power received by the positive and negative input terminals into AC power; an input-side power supply coil for receiving the output of the conversion circuit; an output-side power supply coil arranged opposite to the input-side power supply coil; a rectifier circuit for converting the output of the output-side power supply coil into DC power; and positive and negative output terminals for supplying the output of the rectifier circuit to the protected device. Furthermore, a capacitance mechanism is provided for at least one of the positive and negative output terminals to form a ground capacitance that is larger than the capacitance between the input-side power supply coil and the output-side power supply coil.

[0011] According to this embodiment, the DC surge protection device can output electrically isolated DC from the DC input using a wireless power supply coil. Furthermore, by increasing the spatial distance between the input circuit and the output circuit, or by placing insulating material between them, the impulse withstand voltage and DC isolation withstand voltage between the input and output can be increased. Furthermore, the capacitance mechanism allows for the suppression of only high-frequency components such as surges through capacitance, thereby increasing surge attenuation. On the other hand, since the capacitance formed by this capacitance mechanism does not affect the output efficiency of the DC component, the DC lightning protection device can be made highly efficient. Therefore, a DC lightning protection device with high lightning protection performance can be realized.

[0012] Furthermore, in the DC surge protection device, the capacitance mechanism may include a first metal plate electrically connected to either the positive output terminal or the negative output terminal, and a second metal plate electrically insulated from the first metal plate and provided opposite to the first metal plate.

[0013] As a result, the capacitance mechanism can form capacitance using a first metal plate electrically connected to either the positive or negative output terminal, and a second metal plate that is electrically insulated from the first metal plate and positioned opposite it.

[0014] Furthermore, the capacitance mechanism may include a third metal plate electrically connected to the other of the positive output terminal and the negative output terminal, and a fourth metal plate electrically insulated from the third metal plate and provided opposite to the third metal plate.

[0015] As a result, the capacitance mechanism can form capacitance by a third metal plate electrically connected to the other of the positive output terminal and the negative output terminal, and a fourth metal plate electrically insulated from the third metal plate and provided opposite to the third metal plate.

[0016] Furthermore, the first metal plate and the third metal plate may be provided opposite to each other, the second metal plate may be provided on the opposite side of the third metal plate with respect to the first metal plate, and the fourth metal plate may be provided on the opposite side of the first metal plate with respect to the third metal plate.

[0017] As a result, since the first metal plate and the third metal plate are opposite to each other, it is possible to provide an effect of attenuating noise generated between the output lines by the capacitance formed by the first metal plate and the third metal plate.

[0018] Also, in the DC lightning arrester, the capacitance mechanism may include a first metal plate electrically connected to either the positive output terminal or the negative output terminal, and a metal housing electrically insulated from the first metal plate and provided so as to surround the first metal plate.

[0019] As a result, the capacitance mechanism can form capacitance by a first metal plate electrically connected to either the positive output terminal or the negative output terminal, and a metal housing electrically insulated from the first metal plate and provided so as to surround the first metal plate.

[0020] Also, in the DC lightning arrester, a lightning arrester may be provided in at least any one of between the positive input terminal and the negative input terminal, between the positive input terminal and the ground, and between the negative input terminal and the ground.

[0021] As a result, by suppressing surges from the input side, the surge attenuation amount can be increased.

Advantages of the Invention

[0022] According to the present invention, the following effects can be obtained. · For a DC input, it outputs DC with high efficiency, and can achieve a very large surge attenuation amount, a very high impulse withstand voltage (between input and output, between input and ground, between output and ground), and a very high insulation resistance (between input and output, between input and ground, between output and ground). · A lightning protection device for high-voltage and large-capacity DC can be realized. · For a DC circuit where lightning protection measures were difficult with conventional SPDs, stronger lightning protection measures become possible. · In the insulation measures for equipment using conventional lightning protection transformers, lightning protection by insulation is possible for DC circuits as well as for AC power supplies.

[0023] That is, according to the present invention, a lightning protection device for DC with high lightning protection performance can be realized.

Brief Description of the Drawings

[0024] [Figure 1] Configuration example of the lightning protection device for DC according to the embodiment [Figure 2] Figure for explaining the relationship between the surge voltage and the capacitance in the circuit of FIG. 1 <00−00107> [Figure 3] Configuration example of the capacitance mechanism in the lightning protection device for DC according to the embodiment [Figure 4] Configuration example of the capacitance mechanism in the lightning protection device for DC according to the embodiment [Figure 5] Configuration example of the capacitance mechanism in the lightning protection device for DC according to the embodiment [Figure 6] Another configuration example of the lightning protection device for DC according to the embodiment

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0026] (Embodiment) >Figure 1 shows an example of the circuit configuration of a DC surge protector according to this embodiment. As shown in Figure 1, the DC surge protector according to this embodiment is installed between a DC power supply and the equipment to be protected, i.e., the equipment to be protected from lightning surges. The DC surge protector according to this embodiment includes a positive input terminal 11a and a negative input terminal 11b that receive DC power from a DC power supply, and a positive output terminal 23a and a negative output terminal 23b that supply DC power to the equipment to be protected.

[0027] The DC surge protection device shown in Figure 1 includes a high-frequency conversion circuit 12 and an input-side power supply coil 13 that receives the output of the high-frequency conversion circuit 12 on the input side. On the output side, it includes an output-side power supply coil 21 and a rectifier circuit 22 that converts the output of the output-side power supply coil 21 into DC power. The input-side power supply coil 13 and the output-side power supply coil 21 are positioned opposite each other, making it possible to wirelessly transmit power from the input-side power supply coil 13 to the output-side power supply coil 21.

[0028] The high-frequency conversion circuit 12 is a circuit that converts the DC power received from the DC power supply at the positive and negative input terminals 11a and 11b into AC power. The high-frequency conversion circuit 12 may be configured, for example, to have a plurality of switching FETs (Field Effect Transistors) and a control circuit that controls the on / off operation of the switching FETs. The control circuit can adjust the output of the high-frequency conversion circuit 12 by changing the frequency and duty cycle of the PWM (Pulse Width Modulation) signal applied to the gates of the switching FETs.

[0029] The rectifier circuit 22 is a circuit that converts the AC power output from the output-side power supply coil 21 into DC power. The rectifier circuit 22 may be configured, for example, with a diode configured in a bridge configuration and a capacitor to reduce ripple. The output of the rectifier circuit 22 is supplied to the protected equipment via the positive and negative output terminals 23a and 23b.

[0030] In the DC surge protection device configured in Figure 1, wireless power supply coils 13 and 21 are used to output electrically isolated DC from the DC input. In this case, the impulse withstand voltage and DC isolation withstand voltage between the input and output can be increased by increasing the spatial distance between the input and output circuits, or by placing insulating material between the input and output circuits.

[0031] Furthermore, in the configuration shown in Figure 1, in order to further increase surge attenuation, capacitance mechanisms 3a and 3b are provided at the positive and negative output terminals 23a and 23b to form a sufficiently large capacitance to ground. By increasing the surge attenuation with these capacitance mechanisms 3a and 3b, the lightning protection performance of the DC lightning protection device can be further enhanced.

[0032] Referring to Figure 2, the relationship between surge voltage and capacitance will be explained. Let V1 be the surge voltage between the DC input and ground, and V2 be the surge voltage between the DC output and ground. Also, let C1 be the capacitance between the input side and ground, C2 be the capacitance between the output side and ground, and C12 be the capacitance between the input side power supply coil 13 and the output side power supply coil 21.

[0033] The relationship between surge voltage and capacitance is as follows:

[0034] V2 / V1=C12 / (C12+C2)…(Formula 1) At this time, C2≫C12…(Formula 2) If this relationship exists, the surge attenuation will be large.

[0035] In other words, it is preferable that the capacitance mechanisms 3a and 3b form a ground capacitance C2 that is sufficiently larger than the capacitance C12 between the input-side power supply coil 13 and the output-side power supply coil 21. For example, if C12 is around several tens of pF, then C2 should be around several tens of nF or more.

[0036] This configuration allows only high-frequency components such as surges to be suppressed via capacitance. On the other hand, DC components are output to the protected equipment. The capacitance formed by the capacitance mechanisms 3a and 3b does not affect the output efficiency of DC power (because the frequency of DC is 0 Hz), thus enabling a highly efficient DC lightning protection device.

[0037] Furthermore, the capacitance C1 on the input side relative to ground may be increased. However, the effect of this on surge attenuation will be limited.

[0038] Furthermore, a space may be provided or insulating material may be placed between the input / output power supply coils 13, 21 and the ground (earth). This makes it possible to increase the impulse withstand voltage and dielectric strength between the input and ground, and between the output and ground.

[0039] <Example of a capacity mechanism configuration> Figures 3 to 5 show specific configuration examples of the capacitance mechanisms 3a and 3b. However, the configuration of the capacitance mechanisms 3a and 3b is not limited to those shown.

[0040] In the configuration shown in Figure 3(a), a metal plate A 31 is electrically connected to the positive output terminal 23a, and a metal plate A 33 is electrically connected to the negative output terminal 23b. Opposite to metal plate A 31, a metal plate B 32 is provided, which is electrically insulated from metal plate A 31. Opposite to metal plate A 33, a metal plate B 34 is provided, which is electrically insulated from metal plate A 33. Metal plates B 32 and B 34 are grounded. Capacitance is formed by the opposing metal plates A and B. Each metal plate is made of, for example, copper. For example, metal plate A 31 corresponds to the first metal plate, metal plate B 32 corresponds to the second metal plate, metal plate A 33 corresponds to the third metal plate, and metal plate B 34 corresponds to the fourth metal plate.

[0041] To increase capacitance, it is preferable that metal plates A and B have large cross-sectional areas and be close together. It is also preferable to place a dielectric material with a high dielectric constant, such as phenolic resin, between metal plates A and B. It is preferable to ground metal plate B, but it is not required. Furthermore, the metal plates do not have to be in the shape of plates, but can be in the shape of sheets or wound wires, as long as they form capacitance. It is preferable to arrange opposing metal plates A and B in parallel, but they do not necessarily have to be parallel. In addition, although the planar shape of the metal plates is shown as a rectangle in the figure, the planar shape of the metal plates is not limited to this, and may be circular or polygonal, for example. These same considerations apply to subsequent configurations.

[0042] In the configuration shown in Figure 3(b), metal plates B 32a and B 32b, electrically insulated from metal plate A 31, are provided on both sides of metal plate A 31. Metal plates B 34a and B 34b, electrically insulated from metal plate A 33, are provided on both sides of metal plate A 33. Metal plates B 32a, B 32b, B 34a and B 34b are grounded. Capacitance is formed by the opposing metal plates A and B.

[0043] In the configuration shown in Figure 4(a), metal plate B 35 is provided opposite both metal plates A 31 and 33. In the configuration shown in Figure 4(b), metal plates B 35a and 35b are provided on both sides of metal plates A 31 and 33. Capacitance is formed by the opposing metal plates A and B.

[0044] In the configuration shown in Figure 5(a), a metal housing 41 is provided so as to surround the metal plates A 31 and 33. The metal housing 41 is provided in place of metal plate B in the configurations shown in Figures 3 and 4. Capacitance is formed by the metal plates A 31 and 33 and the metal housing 41.

[0045] The configuration in Figure 5(b) is similar to that in Figure 3(a). However, metal plate B 32 is provided on the opposite side of metal plate A 33, and metal plate B 34 is provided on the opposite side of metal plate A 31. That is, metal plates A 31 and A 33 face each other and form a capacitance C3. This configuration also has the effect of attenuating noise generated between DC output lines. In order to increase the capacitance C3, it is preferable that metal plates A 31 and A 33 have large cross-sectional areas and be close together. It is also preferable to place a dielectric material with a high dielectric constant, such as phenolic resin, between metal plates A 31 and A 33.

[0046] Furthermore, instead of a metal plate, windings or sheets may be used as the capacitance mechanism that forms capacitance on the output line side. Alternatively, capacitors may be provided. However, in this case, the capacitors will need to have high impulse withstand voltage and high insulation performance. Also, in the case of capacitors, there is a possibility of deterioration over time as the temperature rises. On the other hand, the configuration shown in Figures 3 to 5 can avoid this problem.

[0047] Furthermore, it is possible to increase the capacitance between the power supply coil and ground by placing a metal plate B on the power supply coil. However, since this is in the AC region (high frequency), the output efficiency may decrease due to the effect of the capacitance to ground. In particular, if a metal plate B is placed on the input-side power supply coil 13, or between the input-side power supply coil 13 and the output-side power supply coil 21, the output efficiency may decrease significantly.

[0048] As described above, the DC surge protection device according to this embodiment includes a conversion circuit 12 that converts the DC power received by input terminals 11a and 11b into AC power, an input-side power supply coil 13 that receives the output of the conversion circuit 12, an output-side power supply coil 21 arranged opposite the input-side power supply coil 13, and a rectifier circuit 22 that converts the output of the output-side power supply coil 21 into DC power. The output of the rectifier circuit 22 is supplied to the protected equipment from output terminals 23a and 23b. In other words, by using the wireless power supply coils 13 and 21, it is possible to output DC that is electrically isolated from the DC input. Furthermore, by increasing the spatial distance between the input-side circuit and the output-side circuit, or by placing insulating material between them, the impulse withstand voltage and DC isolation withstand voltage between the input and output can be increased.

[0049] In addition, the positive and negative output terminals 23a and 23b are provided with capacitance mechanisms 3a and 3b to form a ground capacitance that is larger than the capacitance between the input-side power supply coil 13 and the output-side power supply coil 21. These capacitance mechanisms 3a and 3b allow only high-frequency components such as surges to be suppressed via capacitance, thereby increasing surge attenuation. On the other hand, the capacitance formed by these capacitance mechanisms 3a and 3b does not affect the output efficiency of the DC component, thus enabling a highly efficient DC lightning protection device.

[0050] In the above explanation, the capacitance mechanisms 3a and 3b are provided on both the positive and negative output terminals 23a and 23b, but this is not the only option; the capacitance mechanism may be provided on only one of the positive or negative output terminals 23a and 23b. Furthermore, the capacitance mechanisms 3a and 3b may be provided separately on the outside of the device, provided they are on the DC output side.

[0051] Furthermore, in the configuration shown in Figure 1, it is also acceptable to omit the capacitive mechanisms 3a and 3b.

[0052] (Other configuration examples) Figure 6 shows another configuration example of a DC surge protection device according to the embodiment. In the configuration of Figure 6, in addition to the configuration of Figure 1, an SPD (Surge Protective Device) is further provided on the input side. Specifically, an SPD 51 is provided between the positive input terminal 11a and the negative input terminal 11b. In addition, an SPD 52 is provided between the positive input terminal 11a and ground, and an SPD 53 is provided between the negative input terminal 11b and ground. The SPD incorporates a nonlinear element such as a metal oxide varistor (MOV), and has the characteristic of having high resistance to normal power supply voltages, but instantaneously becoming low resistance to overvoltages such as lightning surges, and immediately returning to high resistance after processing the lightning surge. Other nonlinear elements include gas-filled discharge tubes (GDTs), avalanche breakdown diodes (ABDs), and surge protection thyristors (TSSs).

[0053] As shown in the configuration of Figure 6, by providing SPDs between input lines or between input lines and ground, surges from the input side can be suppressed, thereby increasing the surge attenuation of the DC surge protection device. In the configuration of Figure 6, SPDs are provided between the positive input terminal 11a and the negative input terminal 11b, between the positive input terminal 11a and ground, and between the negative input terminal 11b and ground, but the configuration is not limited to this, and it is also acceptable to provide SPDs in at least one of these locations.

[0054] Note that in the configuration shown in Figure 6, it is also acceptable to omit the capacitive mechanisms 3a and 3b.

[0055] Furthermore, a device to suppress electromagnetic induction, such as a ferrite core, may be inserted at one or more locations between the DC input and DC output sections. This will suppress harmonics. [Industrial applicability]

[0056] The present invention provides a DC surge protection device with high lightning protection performance, making it useful for protecting equipment operating on DC power from lightning surges. [Explanation of Symbols]

[0057] 3a,3b Capacity mechanism 11a Positive input terminal 11b Negative input terminal 12. High-frequency conversion circuit (conversion circuit) 13 Input-side power supply coil 21 Output side power supply coil 22 Rectifier circuit 23a Positive output terminal 23b Negative output terminal 31 Metal plate A (first metal plate) 32 Metal plate B (second metal plate) 33 Metal plate A (third metal plate) 34 Metal plate B (4th metal plate) 41 Metal casing 51, 52, 53 SPD

Claims

1. A DC surge protection device installed between a DC power supply and a protected device, Positive and negative input terminals that receive DC power from the DC power supply, A conversion circuit that converts the DC power received by the positive and negative input terminals into AC power, An input-side power supply coil that receives the output of the aforementioned conversion circuit, An output power supply coil is positioned opposite the input power supply coil, A rectifier circuit that converts the output of the output-side power supply coil into DC power, The rectifier circuit is provided with positive and negative output terminals for supplying the output to the protected device, A capacitance mechanism is provided for at least one of the positive and negative output terminals to form a ground capacitance that is larger than the capacitance between the input-side power supply coil and the output-side power supply coil. A DC lightning protection device characterized by the following features.

2. In the DC lightning protection device according to Claim 1, The aforementioned capacitance mechanism is A first metal plate is electrically connected to either the positive output terminal or the negative output terminal, The device comprises a second metal plate, which is electrically insulated from the first metal plate and is provided facing the first metal plate. A DC lightning protection device characterized by the following features.

3. In the DC lightning protection device according to Claim 2, The aforementioned capacitance mechanism is A third metal plate is electrically connected to the other of the positive output terminal and the negative output terminal, The present invention comprises a fourth metal plate, which is electrically insulated from the third metal plate and is provided facing the third metal plate. A DC lightning protection device characterized by the following features.

4. In the DC lightning protection device according to Claim 3, The first metal plate and the third metal plate are arranged facing each other, The second metal plate is provided on the side opposite to the third metal plate relative to the first metal plate, and the fourth metal plate is provided on the side opposite to the first metal plate relative to the third metal plate. A DC lightning protection device characterized by the following features.

5. In the DC lightning protection device according to Claim 1, The aforementioned capacitance mechanism is A first metal plate is electrically connected to either the positive output terminal or the negative output terminal, The device comprises a metal housing that is electrically insulated from the first metal plate and is provided so as to surround the first metal plate. A DC lightning protection device characterized by the following features.

6. In the DC lightning protection device according to claim 1, An SPD is provided between the positive input terminal and the negative input terminal, between the positive input terminal and ground, and between the negative input terminal and ground. A DC lightning protection device characterized by the following features.

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