KR19990052218A - Guard device for shielding strong magnetic field - Google Patents

Abstract

The present invention relates to a device for shielding a strong magnetic field generated by the use of a large power, more specifically, by using a combination of a high permeability material and a material with high saturation magnetization to reduce the strong magnetic field to a weak magnetic field, and also to install on-site It can be easily dismantled and shields a wide range of areas to prevent malfunction of controllers such as PLCs, and to prevent problems caused by magnetization of the peripheral equipment such as handle rails or generation of organic currents, and to prevent workers from being exposed to magnetic fields. The present invention relates to a guard device for shielding strong magnetic fields.

According to an aspect of the present invention, there is provided an apparatus for shielding a strong magnetic field generated by using a large electric power, the apparatus comprising: a first panel of a material having a large saturation magnetization located at a magnetic field generating side; A second panel made of a material having a high permeability while maintaining a predetermined distance to the rear side of the panel; And a conductive plate serving as a frame for fixing these panels between the first and second panels, and dispersing a high current (inductive current) generated on the surface of the first panel side and serving as a ground to prevent generation of resistance heat. It provides a guard device for shielding the strong magnetic field comprising a.

According to the present invention, by effectively shielding the strong magnetic field, the strong magnetic field is reduced to the weak magnetic field, it is possible to shield a wide range of areas, and it is easy to install and dismantle on-site, thereby achieving convenience in use.

Description

Guard device for shielding strong magnetic field

The present invention relates to a device for shielding a strong magnetic field generated by the use of a large power, more specifically, by using a combination of a high permeability material and a material with high saturation magnetization to reduce the strong magnetic field to a weak magnetic field, and also to install on-site It can be easily dismantled and shields a wide range of areas to prevent malfunction of controllers such as PLCs, and to prevent problems caused by magnetization of the peripheral equipment such as handle rails or generation of organic currents, and to prevent workers from being exposed to magnetic fields. The present invention relates to a guard device for shielding strong magnetic fields.

In general, in smelting plants that use large power, such as steel mills and non-ferrous smelting plants, magnetic fields must be generated around power cables of power equipment such as arc furnaces and plasma torchs in proportion to the power used. do. The intensity of the magnetic field generated here is proportional to the input power, but especially in the power pattern of the large current (tens KA) / low voltage (hundreds V), a strong magnetic field of several hundred gauss generates adverse effects on the peripheral equipment. As a representative example, handrail facilities are usually installed in the vicinity of large power equipment in order to manage the fall prevention and access of workers. However, due to the generation of strong magnetic fields during operation, this equipment generates organic currents in excess of hundreds of A on the handrail, resulting in the risk of fire, electric shock and burns due to sparking and resistance heat (2-300 ℃). There is this. In addition, the sensors built into the temperature measuring device, which is an operation auxiliary facility, cause malfunctions due to the influence of strong magnetic fields and problems with the PLC controller, causing problems such as the suspension of the operator's body or magnetization of all the surrounding steel structures. In order to solve various problems, the need for a shielding guard device that effectively shields the strong magnetic field has emerged.

Recently, electromagnetic wave absorbers and magnetic shields have been manufactured and disseminated, but mostly for shielding weak magnetic fields and high frequency bands, shielding devices for shielding ultra-low frequency (50-60 Hz) strong magnetic fields have not been developed or commercialized. No shielding guard has been developed that can cover a wide range of meters.

Therefore, the present invention is to solve the conventional problems as described above, its purpose is to reduce the strong magnetic field to the weak magnetic field in order to effectively shield the strong magnetic field, and also easy to install and dismantle the field, The present invention provides a guard device for shielding a strong magnetic field to shield an area.

1 is a cross-sectional view showing the configuration of a strong magnetic field shielding guard device of the present invention;

Figures a), b) and c) of the present invention show a unit frame of the magnetic field shielding guard device of the present invention;

Figure 3 a) and, b) is a view showing a side view of the strong magnetic field shielding guard device of the present invention;

Figure 4 is a front view showing an embodiment of assembling the unit of the strong magnetic field shielding guard device of the present invention;

5 a) and b) are detailed views showing the configuration of connecting the unit of the shielding guard device of the present invention;

Figure 6 is a graph showing the performance of each installation distance of the strong magnetic field shielding guard device of the present invention;

Figure 7 is a graph showing the performance by thickness of the strong magnetic field shielding guard device of the present invention.

※ Explanation of symbols about main part of drawing ※

110 ..... First Panel 120 ..... Reflector

150 ..... Second Panel 153 ..... High Permeability Material

180 ..... conduction plate 200 ..... frame

210 ..... Hollow fiber angle bar 220 ..... Support

224 ..... Top plate

In order to achieve the above object, the present invention provides a device for shielding a strong magnetic field generated by the use of a large power, the first panel of a large saturation magnetization material located on the magnetic field generating side; A second panel made of a material having a high permeability while maintaining a predetermined distance to the rear side of the panel; And a conductive plate serving as a frame for fixing these panels between the first and second panels, and dispersing a high current (inductive current) generated on the surface of the first panel side and serving as a ground to prevent generation of resistance heat. By providing a guard device for shielding the strong magnetic field, characterized in that it comprises a.

Hereinafter, the present invention will be described in detail.

The present invention is a guard device capable of shielding an ultra-low frequency ferromagnetic field of 50-60 Hz corresponding to a low wave impedance near field in which a magnetic field predominates. Since the shielding in the form of a flat plate is the most ideal in the field situation such as a smelting plant, the shielding should be considered in consideration of the normalized wave impedance by the electric dipole and the magnetic dipole model.

The present invention provides a device 100 for shielding a strong magnetic field generated by using a large power, comprising a first panel 110 of a material having a high saturation magnetization located on the magnetic field generating side, to the rear side of the panel 110 The second panel 150 is formed of a material having a high permeability while maintaining a predetermined interval, and serves as a frame for fixing the panels between the first and second panels 110 and 150, and the first panel 110. The conductive plate 180 is provided with a high current (induction current) generated on the surface of the c) side and serves as a ground to prevent generation of resistance heat.

In general, the closer the shield is to a magnetic field source, the higher the impedance of the wave is and the lower the magnetic field is to the contrary (CN, pp.29). The impedance is almost matched, and the shielding effect due to reflection cannot be expected. Therefore, in order to increase the magnetic shielding effect in the proximity system, a method of increasing the loss due to absorption rather than the loss due to reflection is effective.

The shielding effect (SE) of the material is represented by the following Equation 1 as the sum of these terms taking into account the reflection loss (R), absorption loss (A), and multiple reflection loss (M) simultaneously. (友 野 理 平 et al. 電磁波シ-ル ド の 基礎, CMC, pp.210)

SE = R + A + M

Here, the reflection loss R reflects electromagnetic wave energy on the surface of the shielding material to attenuate the intrusion energy, and the absorption loss A means ohmic loss on a path propagating inside the shielding material. The multiple reflection loss (M) is a multiple reflection inside the shielding material. Since the absorption loss is usually 10 dB or more, only the reflection loss (R) and absorption loss (A) in the low impedance system can be considered. It can be represented by 2 and 3.

Where?,?, And t represent the conductivity, permeability, and thickness of the shield, respectively, and f represents the frequency (MH _Z ). As mentioned above, the absorption loss dominates the shielding efficiency in the magnetic shielding of the proximity system. Therefore, in order to increase the shielding effect, a method of increasing the absorption loss using a material having a large thickness t and σμ may be considered. Can be. In practice, however, as the thickness t increases, the absorption loss does not increase infinitely, and as the frequency f moves to the high frequency band, the absorption loss does not increase. Therefore, in order to devise a shielding guard suitable for the field situation, it is desirable to select a material having a larger sigma term as the thickness of the shielding body to be the thickness of the product currently on the market. Generally, it is basic to select a material with a high permeability to shield the magnetic field. However, if the magnetic field source is a strong magnetic field, the permeability decreases due to magnetic saturation and the shielding efficiency is greatly reduced. It is an object of the present invention to maximize shielding efficiency by using a material having a relatively small but large saturation magnetization and a material having a small saturation magnetization but a high permeability.

Therefore, in order to attenuate the strong magnetic field to the weak magnetic field, as shown in FIG. The so-called multiple shielding method using a large material is preferable.

In other words, the shielding guard device of the present invention will be described with reference to the drawings, the shielding guard device is a first panel bonded to the metal plate 120, which is a reflector on the back side of the high saturation material 112 to increase the loss due to the reflection effect on the primary side 110, a second panel 150 to which the high permeability material 153 and the metal plate 120 as a reflector are bonded to the secondary side, and a conductive plate 180 connecting the two panels. In addition, the conductive plate 160 has a structure in which a hollow space 180a is formed inside, as shown in FIGS. 1 and 2C.

The high saturation material 112 and the metal plate 120, and the high permeability material 153 and the metal body 120 and the conductive plate 180 are connected by spot welding or bolt fastening, respectively.

The primary first panel 110 weakens the strong magnetic field, and the secondary second panel 150 shields a magnetic field that is not sufficiently shielded at the primary side and leaks, and the conducting plate 180 is two panels 110 and 150. It serves to prevent the generation of resistance heat by distributing a high current (induction current) generated on the surface of the panel 110 on the primary side and a ground role to fix the structure.

The shielding guard device 100 of the present invention, as well as the shielding function, as well as the installation of the shielded guard device in the field is also an important factor, so the following is the shield guard device structure design and manufacturing method of the shielding guard device to realize the shielding concept It will be described in detail.

The shielding guard device 100 of the present invention, which is manufactured for the purpose of shielding a wide range of several tens of meters, cannot be manufactured integrally due to problems such as obstacles scattered in construction and on-site, so that the shielding guard device 100 is manufactured. The dividing is preferable in terms of construction efficiency, and is united as shown in FIG. Figure 2 shows the frame 200 for the unit (100a) of the shielding guard device 100, in order to reduce the weight of the structure frame 200 to fix the shield using a hollow fiber angle bar 210 as shown in FIG. To produce. In addition, the frame 200 may adjust the distance between the primary shield and the secondary shield by using a commercially available frame material, and double the frame 200 as shown in FIG. In consideration of this, as illustrated in FIG. 3, the conductive plate 180 is mechanically fastened as a bolt 211 to be integrated.

3 is a side view of the unit 100a of the shielding guard device incorporating the shielding concept of FIG. 1 into the frame 200 of FIG. 3 is provided with a support 220 for reinforcing the strength of the shielding guard device unit 100a and supporting the shielding guard device on the floor, and is provided with a lower guard fixture 222 for inserting the shielding guard device unit 100a. The lower guide fixture 222 is welded to the upper fixing plate 224 so that the shielding guard device is not overturned, so that the shield is firmly installed. In addition, in consideration of the case where the shielding guard device 100 is dismantled for maintenance purposes in the field, the upper fixing plate 224 of the shielding body uses the lower fixing plate 228 and the bolt 229 welded to the bottom 226. Make it easy to disassemble by mechanical fastening.

4 is a front view illustrating the assembly of the unit 100a of the shielding guard device 100. The method of connecting the unit (100a) of the chape guard device 100 of the present invention is an important factor influencing the performance of the shielding guard device 100 as shown in Figure 5 the shielding unit (100a) on the frame 200 of FIG. 5) When the extension flange 240 is formed on one side edge of the metal plate 120, 120 as shown in b) of FIG. 5 and the length thereof is longer than the frame length, the extension flange 240 of the one side unit 100a is formed. Adjacent units (100a) are inserted between them to fasten the overlapping plate with an unmarked screw. At this time, in consideration of the thickness of the plate, the extension plate 240 is expanded so that the shielding plate is not distorted during frame processing, and then the units 100a are coupled to each other, and the overlapped portions are fastened by the vertical reinforcement 242. The panel is screwed into a horizontal support 244 as shown in FIG. 4 to maintain strength.

On the other hand, when the shielding plate between the unit (100a) is not connected, the magnetic circuit is not formed, so the shielding effect is sharply lowered, paying particular attention to this advantage. When the area to be shielded is extensive, the shielding guard device unit 100a is repeatedly assembled by the above-described method. In addition, on-site maintenance is often performed so that the door 250 of FIG. 4 is installed at a necessary place in order for the worker to easily enter and exit. By reinforcing the support 220 to maintain the robustness. In addition, in order to maintain the overall balance of the shielding guard device 100, the support cover 255 is mounted on the top of the unit 100a, and connected to the vertical support 220 welded to the floor 226 to receive the force. do.

In addition, when the induced current generated in the shielding panel is not attenuated, heat of resistance is generated at the edges of the panel around the vertical support 220 of FIG. Since the reddish phenomenon occurs when the induced current reaches several hundred A, the connector 260, which is a conductive material having a diameter of 10 mm or more, is mounted on the support 220 to disperse the induced current causing resistance heat. By connecting the vertical support 220 and the unit (100a) is to be grounded through the conductive plate 180.

Hereinafter, the present invention will be described through examples.

Example 1

In order to optimize the installation position of the shielding guard device 100 and the thickness of the shielding guard device 100 of the present invention, there is a method of manufacturing and verifying the real thing, but in the case of a large shielding guard device in particular, to verify as a laboratory scale Since it is difficult and inefficient due to budget and time because it is necessary to derive the optimal plan through trial and error, it is effective to verify through so-called computer simulation using a model that describes the site where the shielding guard device 100 is to be installed in detail. to be.

Therefore, 40MVA (20KA, 200V) large power is used as an embodiment, and a site in which an actual arc furnace composed of a three-phase electrode, three-phase cable, three-phase electrode, and a mast body is installed. Was modeled. In addition, as a method for shielding the high magnetic field generated from the three-phase electrode, three-phase cable, mast (MAST) was evaluated by the computer simulation whether the shielding guard device of the present invention should be installed anyway. At this time, the height of the shielding guard device 100 is fixed to 3m, which is a sufficient height not affected by the magnetic field in consideration of the elongation of the worker when the worker resides on the floor where the shielding guard device is to be installed.

The actual calculations used physical data (permeability, electrical conductivity, thickness, etc.) for the actual material to be used to fabricate the chape guard device in Example 2, which will be described later, and the shielding material will be described later.

6 shows a change in shielding efficiency by distance between shielding guard devices in a magnetic field source. As shown in FIG. 6, it can be seen that the magnetic shielding efficiency of cables, masts, and electrodes around the 2.1m boundary is increased in all three places. In order to further improve shielding efficiency, the magnetic shielding efficiency is separated from the magnetic field source by more than 2.7m. It can be seen that the shield guard device 100 should be installed at a distance.

FIG. 7 shows the shielding efficiency of the shielding guard device 100 according to the thickness of the shielding guard device 100 fixed at 2.7 m. As the thickness of the shielding guard device 100 increases, the shielding efficiency is increased. Actually, when manufacturing and installing the shielding guard device, obstacles in construction, construction problems, problems of connecting the shielding guard device unit 100a, door installation, etc. As the shielding efficiency is lowered as a general precaution, the method to increase the shielding efficiency in calculation should be adopted.

As shown in FIG. 7, the shielding efficiency of 20-25 cm close to 100 dB may be evaluated as the optimal thickness of the shielding guard device in consideration of the stability of the shielding guard device 100 and the space of the site.

Example 2

In order to confirm the performance of the shielding guard device 100 of the present invention, the shielding guard device 100 having a thickness of about 20 cm and a height of 3 m according to the installation method of the shielding guard device 100 derived in Example 1 is 40MVA (20KA, 200V). A shielding guard device 100 having a total length of about 34m was installed around an actual arc furnace site using a large power of the. As described above, the installation position of the shielding guard device 100 is 2.7 m away from the center of the arc furnace. When 40 MVA is applied, the three-phase electrode is around 70 Gauss and the three-phase cable is about 470 Gauss. The MAST main body was found to generate a 150 Gauss strong magnetic field.

The material selection of the shielding guard device 100 was made of a commercially available material. That is, the primary side is a general rolled steel sheet as the high saturation material 112 as the electrical plate / reflector metal plate 120, and the secondary side is a high nickel permeability material 153 as the high nickel alloy steel sheet / reflector as the metal plate 120 as a general rolled steel plate The shielding guard device 100 was manufactured by using the thickness of the plate was set to 1mm each in order to reduce the weight on the processing and shielding guard device (100). In addition, although the reflector metal plate 120 is used as a general rolled steel sheet above, it is possible to use a copper plate (copper plate) in order to obtain a better effect than this, which is expensive to obtain a material of a large standard It is a difficult one, so we used a general rolled steel sheet, but this is the same for copper plates.

The frame 200 of the shielding guard device 100 has a tendency to be made of an aluminum hollow square bar, and the thickness is 3mm in consideration of strength. In addition, magnetic steel plates and high-nickel alloy steel sheets are attached to the frame 200 and subjected to proper heat treatment before screwing to express good magnetic properties. The surface of the shielding guard device 100 after construction is prevented from corrosion. An epoxy paint was applied.

After the shielding guard device 100 was constructed, the leakage magnetic field was measured by a model HI-3604 power survey meter manufactured by HOLADAY, and the measurement position was performed immediately after the shielding guard device 100 installed (about 2.7 m). The following table shows the results of comparing and analyzing the magnetic field strength before and after the installation of the shielding guard device 100 of the present invention.

Shielding efficiency of the shielding guard device 100 of the present invention. Measuring area Generated magnetic field strength (G) (before shielding) Leakage magnetic field strength (G) (after shielding) Shielding Efficiency (dB) 3-phase cable 370 4.5 38 Mast 150 2.1 37 3-phase electrode 70 1.8 32

As shown in the above table, the performance of the present invention chapegard device 100 can shield the strong magnetic field sufficiently, the shielding efficiency of all the locations in excess of 30dB was confirmed that the present invention exhibits an excellent shielding effect .

As described above, according to the present invention, by shielding the strong magnetic field with a weak magnetic field so as to effectively shield the strong magnetic field, it is possible to shield a wide range of areas, and also to facilitate the installation and disassembly of the field to achieve convenience in use. will be.

Claims (11)

An apparatus for shielding a strong magnetic field generated by the use of a large power, comprising: a first panel (110) of a high saturation magnetization material located on the magnetic field generating side; A second panel 150 made of a material having a high permeability while maintaining a predetermined distance to the rear side of the panel; And acting as a frame for fixing these panels between the first and second panels, dispersing high currents (induction currents) generated on the surface of the first panel 110 and serving as a ground to prevent the generation of resistance heat. Conductive plate 180; shielding device for a strong magnetic field comprising a. The method of claim 1, wherein the first panel 110 is bonded to the metal plate 120 of the reflector to increase the loss due to the reflection effect on the back of the high saturation material 112, the second panel 150 is The high magnetic permeability material 153 and the reflector metal plate 120 is bonded to the secondary side, the conductive plate 180 is a shield for the strong magnetic field, characterized in that to form a hollow space (180a) therein Guard device. 3. The first panel 110, the second panel 150, and the conductive plate 180 are formed of the highly saturated material 112, the metal plate 120, and the conductive plate from the ferromagnetic side to the weak magnetic side, respectively. (180), high magnetic permeability material (153) and the metal plate 120 in the order of the strong magnetic field shielding guard device, characterized in that arranged. 3. The method of claim 2, wherein the high saturation material 112 is an electrical steel sheet, the metal plate 120 is a general rolled steel or copper plate, and the high permeability material 153 is a high nickel alloy steel sheet for shielding the strong magnetic field Guard device. The method of claim 1, wherein the first panel 110, the second panel 150, and the conductive plate 180 form a unit 100a and are mounted to the frame 200, and the frame 200 is hollow. It consists of a square bar 210, the frame 200 is made of a double, strong magnetic field shielding guard device, characterized in that the coupling by coupling the conductive plate 180 as a bolt (211). The method according to claim 5, wherein when attaching the unit (100a) on the frame 200, an extension flange 240 is formed on one side edge of the metal plate (120) (120) to insert adjacent units (100a) therebetween. Strong magnetic field shielding guard device characterized in that the overlapping plate. The high saturation material 112 and the metal plate 120, and the high permeability material 153, the reflector 120 and the conductive plate 180 are each connected by spot welding. Guard device for shielding strong magnetic fields. According to claim 1, wherein the support (220) for supporting the floor while supporting the strength of the unit (100a) is provided, the lower guard fixture 222 for inserting the shield guard device unit (100a) is provided, The lower guide fixture 222 is welded to the upper fixing plate 224 so that the shielding guard device is not overturned, and the upper fixing plate 224 uses the lower fixing plate 228 and the bolt 229 welded to the bottom 226. Guard device for shielding strong magnetic fields, characterized in that the installation is firm. 9. The guard apparatus for shielding a strong magnetic field according to claim 8, further comprising a door (250) which is easily accessible by an operator for maintenance at the site. The method according to claim 8, wherein the connector 260, which is a conductive material, is mounted between the vertical support 220 and the unit 100a to induce an induced current around the vertical support 220 to the conduction plate 180 and through ground. Guard device for shielding strong magnetic field, characterized in that the dispersion. 6. The guard apparatus for shielding a strong magnetic field according to claim 5, wherein the frame (200) is made of aluminum hollow square bars to reduce weight.