Composite passive magnetic shielding system suitable for low frequency magnetic field suppression

Abstract

The application relates to the technical field of electromagnetic shielding, and discloses a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression. The conductive layer can attenuate the medium-low-frequency alternating magnetic field, the magnetic field strength incident to the inner magnetic conductive layer is reduced, and the magnetic saturation of the magnetic conductive layer is avoided; the magnetic shunt of the direct-current or extremely-low-frequency magnetic field is shielded by the inner magnetic conductive layer, the magnetism is attenuated gradually, the full-frequency band coverage of the low-frequency magnetic field such as 0Hz-10kHz is realized, and therefore the better magnetic shielding effect is realized. The demagnetizing coil is wound on the magnetic conductive layer, the residual magnetism generated by the magnetization of the magnetic conductive layer by the external magnetic field is offset, the magnetic conductive layer is avoided from becoming the magnetic field pollution source in the shielding cabin, and the stability of the zero magnetic environment in the shielding cabin is ensured. The single multi-path synchronous power modulation system can synchronously complete the magnetic attenuation of the magnetic conductive layer of the full shielding cabin, the problems of uneven magnetic field offset and asynchronization caused by single independent control are avoided, and therefore the magnetic shielding performance of the shielding cabin is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding technology, and in particular to a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression. Background Technology

[0002] In fields highly sensitive to magnetic field environments, such as ultra-high sensitivity measurement of extremely weak magnetic fields, biomagnetic imaging, quantum sensing, and semiconductor processes, it is often necessary to establish a low magnetic environment with a background magnetic field below the nT level. Currently, common magnetic shielding technologies primarily utilize permalloy to construct magnetic shielding devices for high-performance shielding. However, permalloy itself is expensive, and using it as the main shielding layer results in a large amount of material usage, leading to high costs. Furthermore, its shielding effect in suppressing magnetic fields at low frequencies is poor, affecting the stability of the spatial magnetic field. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression, in order to solve the problems of high material cost and poor shielding effect in low-frequency magnetic field suppression when using permalloy as the main shielding layer, which affects the stability of the space magnetic field.

[0004] In a first aspect, the present invention provides a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression, comprising: The shielding chamber is a cuboid structure formed by several passive shielding layers. The passive shielding layer comprises at least one magnetically conductive layer and at least one electrically conductive layer, wherein the magnetically conductive layer and the electrically conductive layer are sequentially spliced ​​together to form the passive shielding layer. The demagnetizing system includes a demagnetizing coil and a single-unit multi-channel synchronous power modulation system. The demagnetizing coil is wound on the magnetic conductive layer, and the single-unit multi-channel synchronous power modulation system is electrically connected to the demagnetizing coil to synchronously reduce the magnetism of the magnetic conductive layer.

[0005] Beneficial effects: The conductive layer attenuates low-to-medium frequency alternating magnetic fields, reducing the magnetic field strength incident on the inner magnetically conductive layer and preventing magnetic saturation. The inner magnetically conductive layer shields the magnetic shunts of DC or extremely low-frequency magnetic fields, causing the magnetism to attenuate step by step, thus achieving full-band coverage of low-frequency magnetic fields such as 0Hz-10kHz, resulting in better magnetic shielding. The conductive layer shares the shielding burden in the low-to-medium frequency range, and the optimized interlayer layout between the magnetically conductive and conductive layers allows the magnetically conductive layer to operate in an unsaturated state, eliminating the need for large amounts of high-cost, high-permeability materials. This effectively reduces the amount of high-permeability materials used while ensuring full-band shielding performance from 0Hz to 10kHz.

[0006] Demagnetizing coils are wound around the magnetically conductive layer, and a reverse magnetic field is applied to the layer to counteract the residual magnetism generated by the magnetically conductive layer being magnetized by an external magnetic field. This prevents the layer from becoming a source of magnetic field pollution within the shielded chamber and ensures the stability of the "zero-magnetic" environment inside the chamber. A single multi-channel synchronous power modulation system can achieve synchronous control of multiple outputs, matching the corresponding drive current to the demagnetizing coils at different locations to generate corresponding reverse magnetic fields. This synchronously completes the magnetic reduction of the magnetically conductive layer in the fully shielded chamber, avoiding the problems of uneven magnetic field cancellation and asynchrony that occur with single-channel independent control, thereby effectively improving the magnetic shielding performance of the shielded chamber.

[0007] In one embodiment, the number of magnetically conductive layers is N, and the number of conductive layers is M, satisfying 1≤M≤N≤8.

[0008] In one embodiment, each of the magnetic conductive layers is formed by stacking several single plates and splicing them together in a staggered manner.

[0009] In one embodiment, the number of single plates in each layer of the magnetic conductive layer is n, satisfying 2≤n≤10; the thickness of the single plate is d, satisfying 0.025mm≤d≤2mm.

[0010] In one embodiment, each of the magnetically conductive layers is formed of at least one of a non-oriented silicon steel layer, an oriented silicon steel layer, a permalloy layer, and an amorphous nanocrystalline layer; The conductive layer includes any one of a copper layer, an aluminum layer, and an aluminum-based copper-clad layer.

[0011] In one embodiment, the thickness of the non-oriented silicon steel layer is 0.5mm-20mm; the thickness of the oriented silicon steel layer is 0.5mm-20mm; the thickness of the permalloy layer is 0.5mm-20mm; and the thickness of the amorphous nanocrystalline layer is 0.05mm-0.25mm.

[0012] In one embodiment, the thickness of the non-oriented silicon steel layer is such that the magnetic conductive layer is formed by a combination of a non-oriented silicon steel layer, an oriented silicon steel layer, a permalloy layer, and an amorphous nanocrystalline layer, wherein the spacing between the oriented silicon steel layer and the permalloy layer is 20mm-800mm, and the spacing between the amorphous nanocrystalline layer and the permalloy layer is 10mm-500mm.

[0013] In one embodiment, the length of the shielded chamber is L1, satisfying 1.5m≤L1≤8m, the width is W1, satisfying 1.5m≤W1≤8m, and the height is H1, satisfying 2m≤H1≤6m. The length of the shielded cabin is L2, which satisfies 1.55m≤L2≤9m; the width is W2, which satisfies 1.55m≤W2≤9m; and the height is H2, which satisfies 2.05m≤H2≤7m.

[0014] In one embodiment, the thickness of the conductive layer is 1mm-30mm.

[0015] In one embodiment, the demagnetizing coil is arranged along the edge of the shielding chamber within the shielding chamber; or The demagnetizing coils are arranged in a cross shape and evenly inside the shielding chamber. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the demagnetizing coil in a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the magnetic permeable layer in a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the internal residual magnetism and magnetic field variation curves of a composite passive magnetic shielding system according to an embodiment of the present invention.

[0018] Figure label: 10. Shielding chamber; 100. Passive shielding layer; 110. Magnetic conductive layer; 111. Non-oriented silicon steel layer; 120. Conductive layer; 112. Oriented silicon steel layer; 113. Permalloy layer; 114. Amorphous nanocrystalline layer; 200. Demagnetizing coil. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The following is combined with Figures 1 to 4 The following describes embodiments of the present invention.

[0022] According to embodiments of the present invention, such as Figure 1 and Figure 4 As shown, a composite passive magnetic shielding system suitable for low-frequency magnetic field suppression is provided, comprising: a shielding chamber 10, which is a cuboid structure formed by a plurality of passive shielding layers 100; the passive shielding layer 100 includes at least one magnetically conductive layer 110 and at least one conductive layer 120, which are sequentially spliced ​​together to form the passive shielding layer 100; and a demagnetizing system, comprising a demagnetizing coil 200 and a single multi-channel synchronous power modulation system, wherein the demagnetizing coil 200 is wound on the magnetically conductive layer 110, and the single multi-channel synchronous power modulation system is electrically connected to the demagnetizing coil 200 for synchronously reducing the magnetism of the magnetically conductive layer 110.

[0023] In this embodiment, the shielding chamber 10 has a rectangular parallelepiped structure, which is formed by a series of passive shielding layers 100. Each passive shielding layer 100 is formed by sequentially splicing at least one magnetically conductive layer 110 and at least one conductive layer 120. When both the magnetically conductive layer 110 and the conductive layer 120 are single layers, the magnetically conductive layer 110 is located on the inner side of the passive shielding layer 100, that is, on the side closer to the internal space of the shielding chamber 10; the conductive layer 120 is located on the outer side of the passive shielding layer 100, that is, on the side farther away from the internal space of the shielding chamber 10. When both the magnetically conductive layer 110 and the conductive layer 120 are multi-layered, the conductive layer 120 is sandwiched between two adjacent magnetically conductive layers 110.

[0024] The conductive layer 120 attenuates the low-to-medium frequency alternating magnetic field, reducing the magnetic field strength incident on the inner magnetically conductive layer 110 and preventing magnetic saturation of the magnetically conductive layer 110. The inner magnetically conductive layer 110 shields the magnetic shunt of DC or extremely low frequency magnetic fields, causing the magnetism to attenuate step by step, thereby achieving full-band coverage of low-frequency magnetic fields such as 0Hz-10kHz, thus achieving a better magnetic shielding effect. The conductive layer 120 shares the shielding burden in the low-to-medium frequency band. At the same time, through the optimized interlayer layout between the magnetically conductive layer 110 and the conductive layer 120, the magnetically conductive layer 110 operates in an unsaturated state, eliminating the need to stack a large amount of high-cost high-permeability materials, thus effectively reducing the amount of high-permeability materials used and ensuring full-band shielding performance from 0Hz to 10kHz.

[0025] The demagnetizing system includes a demagnetizing coil 200 and a single-unit multi-channel synchronous power modulation system. The demagnetizing coil 200 is wound on the magnetically conductive layer 110, applying a reverse magnetic field to the magnetically conductive layer 110 to cancel the residual magnetism generated by the magnetically conductive layer 110 being magnetized by an external magnetic field, thus preventing it from becoming a source of magnetic field pollution within the shielded chamber 10 and ensuring the stability of the "zero magnetic" environment within the shielded chamber 10. Here, a zero magnetic environment typically refers to a special environment close to zero magnetic field.

[0026] A single multi-channel synchronous power modulation system is electrically connected to multiple demagnetizing coils 200. The single multi-channel synchronous power modulation system may include a central control unit, multiple power drive channels, and a synchronization mechanism; each of the multiple power drive channels corresponds to a demagnetizing coil 200 on a magnetically conductive layer 110. Since the magnetic field distribution and magnetization state of the magnetically conductive layers 110 on each side of the cuboid shielding chamber 10 are different, the single multi-channel synchronous power modulation system can achieve synchronous control of multiple outputs, matching the corresponding drive current to the demagnetizing coils 200 at different positions, generating corresponding reverse magnetic fields, and synchronously completing the magnetic reduction of the magnetically conductive layers 110 of the fully shielded chamber 10. This avoids the problems of uneven magnetic field cancellation and asynchrony that occur with single-channel independent control, thereby effectively improving the magnetic shielding performance of the shielding chamber 10.

[0027] Testing revealed that the DC shielding performance of the composite passive magnetic shielding system provided by this invention is as follows: Figure 4 As shown, the residual magnetism inside the shielded chamber 10 is less than 50 nT, the residual magnetism in the shielded door area increases slightly, and the change in the magnetic field inside the door after repeated opening and closing is less than 5 nT.

[0028] In other possible implementations, the shielded chamber 10 has a logistics door and a pedestrian door, both of which are equipped with pneumatic locking devices and manual emergency opening devices.

[0029] In one embodiment, the number of magnetically conductive layers 110 is N, and the number of conductive layers 120 is M, satisfying 1≤M≤N≤8.

[0030] In this embodiment, the magnetically conductive layer 110 is a large layer whose size matches that of the conductive layer 120. The number of magnetically conductive layers 110 and the number of conductive layers 120 can be any value among 1, 2, 3, 4, 5, 6, 7, and 8 layers, respectively. Simultaneously, it is necessary to ensure that the number of conductive layers 120 does not exceed the number of magnetically conductive layers 110. If the number of magnetically conductive layers 110 and conductive layers 120 is too large, such as exceeding 8 layers, the material and manufacturing costs of the magnetically conductive layers 110 and conductive layers 120 will increase significantly, but the shielding performance of the shielding chamber 10 will not be significantly improved by stacking too many magnetically conductive layers 110. Moreover, an excessive number of magnetically conductive layers 110 and conductive layers 120 will correspondingly increase the wall thickness of the shielding chamber 10, thereby increasing the overall weight of the shielding chamber 10, making conventional buildings unable to support the weight of the shielding chamber 10, thus rendering the shielding chamber 10 unsuitable.

[0031] By incorporating the conductive layer 120, the conductive layer 120 preferentially attenuates common power frequency alternating magnetic fields, reducing the magnetic field strength incident on the magnetically conductive layer 110. This reduces the risk of magnetic saturation and remanent magnetization accumulation in the magnetically conductive layer 110, ensuring that the magnetically conductive layer 110 operates at its optimal permeability and alleviating the workload of the downstream synchronous demagnetization system. In low-frequency magnetic field suppression applications, the conductive layer 120 is ineffective against DC magnetic fields and has limited shielding effect against extremely low-frequency magnetic fields. Therefore, by incorporating the magnetically conductive layer 110 and ensuring that the number of magnetically conductive layers 110 is greater than or equal to the number of conductive layers 120, the magnetically conductive layer 110 can effectively eliminate the magnetism of DC or low-frequency magnetic fields, thereby ensuring the shielding effect of the shielding chamber 10.

[0032] In one embodiment, each magnetic conductive layer 110 is formed by stacking several single plates and splicing them together in a staggered manner.

[0033] In this embodiment, the material of the magnetic permeable layer 110 possesses both high magnetic permeability and high electrical conductivity. When an alternating magnetic field passes through it, eddy currents are induced within the material. These eddy currents generate a reverse magnetic field, which cancels out the magnetic flux within the highly permeable material, thereby weakening the magnetic shunt capability. By stacking multiple single-board units, the eddy currents can be confined to a very small loop within each single-board unit, thereby reducing the eddy current loop area and intensity, and suppressing eddy current losses.

[0034] Furthermore, if the seams of two adjacent single-layer boards are perfectly aligned, a magnetic leakage channel will be formed that runs through the entire magnetically conductive layer 110, allowing external magnetic fields to directly penetrate into the shielding chamber 10. By staggering the seams of several single-layer boards, the seam of one layer corresponds to the seamless surface of another layer, thus cutting off the continuous magnetic leakage channel. Even if a small amount of magnetic field lines leak out at the seam of one layer, they will be captured and diverted by the magnetically conductive single-layer board of the other layer, preventing them from penetrating further into the shielding chamber 10, effectively improving the shielding performance of the shielding chamber 10; at the same time, there is no need to compensate for the performance loss caused by magnetic leakage and eddy currents by stacking material thickness, further reducing the amount of high-cost, high-permeability materials used. The staggered seam width of each layer can be any value of 15mm, 20mm, 25mm, or 30mm, or a value between any two of these values.

[0035] In one embodiment, the number of single plates in each magnetic conductive layer 110 is n, satisfying 2≤n≤10; the thickness of the single plate is d, satisfying 0.025mm≤d≤2mm.

[0036] In this embodiment, the number n of the single plates in each magnetic conductive layer 110 can be any value from 2, 3, 4, 5, 6, 7, 8, 9, to 10. If there is only one single plate, the splicing seam extends into the interior of the shielding chamber 10, forming a direct leakage magnetic channel for the low-frequency magnetic field, thereby reducing the shielding performance of the shielding chamber 10. If the number of single plates is too large, such as more than 10, it will not actually improve the shielding performance of the magnetic conductive layer 110, and will also increase the overall thickness and weight of the magnetic conductive layer 110, thereby increasing the material cost of the magnetic conductive layer 110.

[0037] By rationally setting the number of individual boards, the overall thickness and weight of each large magnetic layer 110 can be effectively controlled while ensuring the shielding performance of the magnetic conductive layer 110, thereby reducing the material cost of the magnetic conductive layer 110. At the same time, multiple individual boards can be spliced ​​in a staggered manner to avoid forming magnetic leakage channels that penetrate into the interior of the shielding chamber 10, thus ensuring the shielding performance of the shielding chamber 10.

[0038] Furthermore, the thickness d of the single-layer plate can be any value or a value between any two of the following: 0.025mm, 0.05mm, 0.1mm, 0.3mm, 0.5mm, 0.7mm, 1mm, 1.2mm, 1.5mm, 1.7mm, and 2mm. If the thickness of the single-layer plate is too low, such as less than 0.025mm, it will increase the difficulty of the single-layer plate manufacturing process, making it prone to deformation, breakage, and uneven magnetic properties during production, thus reducing the yield of the single-layer plate. Moreover, the rigidity is poor, and it is easy to undergo tensile deformation during installation, thereby reducing the shielding ability of the single-layer plate. If the thickness of the single-layer plate is too high, such as greater than 2mm, it will be more difficult to bend, cut, or splice the single-layer plate. Cracking and breakage are likely to occur during bending, and the stress during installation and fastening will penetrate into the plate, causing irreversible deterioration of magnetic properties. At the same time, the magnetic domain structure of thick plates is uneven, the hysteresis loss is large, and the residual magnetism is more likely to accumulate, which will significantly increase the workload of the synchronous demagnetization system.

[0039] By appropriately setting the thickness of the single-board, the manufacturing process difficulty of the single-board is effectively reduced, and the yield rate of the single-board is effectively improved. This also reduces the risk of tensile deformation during single-board installation, ensuring the shielding capability of the single-board. Simultaneously, it reduces the risk of magnetic performance degradation of the single-board and avoids uneven magnetic domain structure and high hysteresis loss due to excessive single-board thickness. Furthermore, it reduces the accumulation of residual magnetism within the single-board, which is beneficial for improving the efficiency of the subsequent demagnetization system and ensuring the shielding performance within the shielding chamber 10.

[0040] In one embodiment, each magnetically conductive layer 110 is formed of at least one of a non-oriented silicon steel layer 111, an oriented silicon steel layer 112, a permalloy layer 113, and an amorphous nanocrystalline layer 114.

[0041] Specifically, non-oriented silicon steel has good initial magnetic permeability, low cost, extremely high saturation magnetic flux density, strong anti-magnetic saturation ability, good processing, bending and welding performance, extremely low mass production cost, and low remanence.

[0042] Oriented silicon steel has extremely high permeability in the rolling direction, and its cost is slightly higher than that of non-oriented silicon steel. However, its permeability along the rolling direction is far greater than that of non-oriented silicon steel. It also has lower low-frequency loss, strong anti-saturation ability, and good machinability.

[0043] Permalloy has extremely high initial permeability and extremely high cost. It has high permeability in weak magnetic environments, extremely strong shielding ability for very low frequency magnetic fields, and narrow hysteresis loop, making it suitable for nT-level zero magnetic environments.

[0044] Amorphous nanocrystals have high initial permeability, extremely low loss at the kHz level, and a cost between silicon steel and permalloy. They balance high permeability with moderate saturation flux density, and their loss in the low-to-mid frequency range of 1kHz-10kHz is much lower than that of silicon steel and permalloy. They also offer balanced performance across the entire frequency range.

[0045] In one possible implementation, the magnetic layer 110 is formed by combining a non-oriented silicon steel layer 111 and an oriented silicon steel layer 112.

[0046] Specifically, non-oriented silicon steel layer 111 and oriented silicon steel layer 112 are arranged alternately. Non-oriented silicon steel layer 111 provides omnidirectional basic protection and shields stray magnetic fields without a fixed direction. Oriented silicon steel layer 112 makes up for the insufficient shielding effectiveness of non-oriented silicon steel under strong directional magnetic fields. This can reduce the material cost of shielding chamber 10 while ensuring the shielding performance of shielding chamber 10.

[0047] In one possible implementation, the magnetically conductive layer 110 is formed by combining a non-oriented silicon steel layer 111 and a permalloy layer 113. Specifically, the non-oriented silicon steel layer 111 and the permalloy layer 113 are arranged alternately. The non-oriented silicon steel layer 111 first attenuates most of the external geomagnetic and power frequency strong magnetic fields, creating a stable weak magnetic working environment for the inner permalloy layer 113. Then, the permalloy layer 113 attenuates the remaining magnetic field to the nT level, compensating for the performance shortcomings of the non-oriented silicon steel layer 111 in extremely low-frequency weak magnetic scenarios and ensuring the shielding performance of the shielding chamber 10. Under the same shielding effectiveness, the material cost is reduced by more than half compared to using pure permalloy, and it can cover the entire frequency band from 0Hz to 10kHz. It has good processability, and the non-oriented silicon steel can also serve as the structural support for the passive shielding layer 100.

[0048] In one possible implementation, the magnetically conductive layer 110 is formed by combining a grain-oriented silicon steel layer 112 and a permalloy layer 113. Specifically, the grain-oriented silicon steel layer 112 and the permalloy layer 113 are arranged alternately. The grain-oriented silicon steel layer 112 first attenuates most of the strong power frequency magnetic field from strong power frequency interference in a fixed direction, creating a better weak magnetic environment for the inner permalloy layer 113. At the same time, the grain-oriented silicon steel layer 112 itself has lower power frequency loss, less heat generation, and stronger long-term magnetic stability. Then, the permalloy layer 113 compensates for the anisotropy of the grain-oriented silicon steel layer 112, providing all-directional blinding for stray magnetic fields in non-rolling directions, ultimately achieving a stable zero magnetic environment and ensuring the shielding performance of the shielding chamber 10 and the stability of the space magnetic field.

[0049] In one possible implementation, the magnetically conductive layer 110 is formed by combining a non-oriented silicon steel layer 111, an oriented silicon steel layer 112, and a permalloy layer 113. Specifically, the non-oriented silicon steel layer 111, the oriented silicon steel layer 112, and the permalloy layer 113 are arranged alternately. The non-oriented silicon steel layer 111 first attenuates most of the external geomagnetic and power frequency strong magnetic fields. Then, due to the insufficient shielding effectiveness of the non-oriented silicon steel layer 111 under strong directional magnetic fields, a more stable weak magnetic working environment is created for the inner permalloy layer 113. Finally, the permalloy layer 113 attenuates the remaining magnetic field to the nT level, achieving a zero magnetic environment inside the shielded chamber 10. This compensates for the performance shortcomings of the non-oriented silicon steel layer 111 and the oriented silicon steel layer 112 under extremely low frequency weak magnetic fields, ensuring the shielding performance of the shielded chamber 10 and the stability of the spatial magnetic field inside the shielded chamber 10.

[0050] In one possible implementation, the magnetically conductive layer 110 is formed by combining a non-oriented silicon steel layer 111, an oriented silicon steel layer 112, a permalloy layer 113, and an amorphous nanocrystalline layer 114. The spacing between the oriented silicon steel layer 112 and the permalloy layer 113 is 20 mm to 800 mm, and the spacing between the amorphous nanocrystalline layer 114 and the permalloy layer 113 is 10 mm to 500 mm.

[0051] Specifically, non-oriented silicon steel layer 111, oriented silicon steel layer 112, permalloy layer 113, and amorphous nanocrystalline layer 114 are arranged alternately. The non-oriented silicon steel layer 111 first attenuates most of the external geomagnetic and power frequency strong magnetic fields. Then, due to the insufficient shielding effectiveness of the non-oriented silicon steel layer 111 under strong directional magnetic fields, a more stable weak magnetic working environment is created for the inner permalloy layer 113. Then, the permalloy layer 113 attenuates the remaining magnetic field to the nT level, making up for the performance shortcomings of the non-oriented silicon steel layer 111 and oriented silicon steel layer 112 under extremely low frequency weak magnetic fields. Finally, the amorphous nanocrystalline layer 114 fills in the shielding blind zone in the mid-to-high frequency band, while further attenuating the remaining magnetic field, realizing a zero magnetic environment inside the shielding chamber 10, ensuring the shielding performance of the shielding chamber 10, and ensuring the stability of the spatial magnetic field inside the shielding chamber 10.

[0052] Furthermore, the spacing between the oriented silicon steel layer 112 and the permalloy layer 113 can be any value from 20mm, 50mm, 70mm, 100mm, 150mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, and 800mm, or a value between any two of these values. If the spacing between the oriented silicon steel layer 112 and the permalloy layer 113 is too small, such as less than 20mm, strong magnetic coupling will occur between them, causing the strong magnetic field of the outer layer to directly penetrate into the inner layer, effectively merging the two layers into a single thick plate, thereby reducing its shielding effectiveness. If the spacing between the oriented silicon steel layer 112 and the permalloy layer 113 is too large, such as greater than 800mm, it will increase the outer diameter of the shielding chamber 10, compressing the usable internal space, and will not effectively improve the shielding effectiveness. By appropriately setting the spacing between the oriented silicon steel layer 112 and the permalloy layer 113, magnetic coupling can be effectively avoided, ensuring that the outer oriented silicon steel layer 112 first attenuates most of the strong magnetic field, and the inner permalloy layer 113 then provides fine shielding against the weak magnetic field, achieving the design goal of gradient attenuation. At the same time, it avoids the overall size of the shielding chamber 10 from being too large, thereby increasing the usable space inside the shielding chamber 10.

[0053] Furthermore, the spacing between the amorphous nanocrystalline layer 114 and the permalloy layer 113 can be any value from 10mm, 20mm, 30mm, 40mm, 50mm, 70mm, 100mm, 200mm, 300mm, 400mm, and 500mm, or a value between any two of these values. If the spacing between the amorphous nanocrystalline layer 114 and the permalloy layer 113 is too small, such as less than 10mm, strong magnetic coupling may occur between them, and the eddy current fields may interfere with each other, causing the low-loss advantage of the amorphous nanocrystalline layer 114 at low and medium frequencies to be lost. If the spacing between the amorphous nanocrystalline layer 114 and the permalloy layer 113 is too large, such as greater than 500mm, it will also increase the outer diameter of the shielding chamber 10, without effectively improving the shielding effectiveness. By reasonably setting the spacing between the amorphous nanocrystalline layer 114 and the permalloy layer 113, the residual magnetic field can be attenuated to the nT level by the permalloy layer 113, and then the amorphous nanocrystalline layer 114 can fill the shielding blind zone in the mid-to-high frequency band, while further attenuating the residual magnetic field, thereby achieving a zero magnetic environment inside the shielding chamber 10, ensuring the shielding performance of the shielding chamber 10, and ensuring the stability of the spatial magnetic field inside the shielding chamber 10.

[0054] In one embodiment, the conductive layer 120 includes any one of a copper layer, an aluminum layer, and an aluminum-based copper-clad layer.

[0055] In this embodiment, the conductive layer 120 can be formed by pressing a single whole plate to form a closed structure, and in order to improve the conductivity at the pressing point of the conductive layer 120, the oxide layer on the surface of the conductive layer 120 can be removed.

[0056] The copper layer has the highest electrical conductivity, the best eddy current shielding performance, strong oxidation resistance, and stable long-term performance, making it suitable for applications requiring extreme shielding performance, strong alternating interference scenarios, and small-size precision shielding chambers.

[0057] The aluminum layer has moderate electrical conductivity, extremely low cost, low density, and significant lightweight advantages. Large-size plates are easy to process and transport, making it suitable for large-size shielded cabins, lightweight application scenarios, etc.

[0058] Aluminum-based copper-clad laminates are formed by coating copper onto a base layer of aluminum. The effective conductivity is close to that of pure copper, combining the high conductivity of copper with the lightweight and low-cost advantages of aluminum. Under the skin effect of an alternating magnetic field, eddy currents concentrate in the surface copper layer, resulting in shielding effectiveness close to that of pure copper. However, its weight and cost are relatively lower than pure copper, making it suitable for general-purpose applications that balance performance and cost, such as large-size lightweight shielding enclosures.

[0059] It is understandable that copper, aluminum, or aluminum-based copper clad layer can be used as the conductive layer 120 in different application scenarios. Users can set it according to their needs without specific restrictions.

[0060] In one embodiment, the thickness of the non-oriented silicon steel layer 111 is 0.5mm-20mm; the thickness of the oriented silicon steel layer 112 is 0.5mm-20mm; the thickness of the permalloy layer 113 is 0.5mm-20mm; and the thickness of the amorphous nanocrystalline layer 114 is 0.05mm-0.25mm.

[0061] In this embodiment, the thickness of the non-oriented silicon steel layer 111 can be any value or a value between any two of the following: 0.5mm, 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 7mm, 10mm, 12mm, 15mm, 17mm, and 20mm; the thickness of the oriented silicon steel layer 112 can be any value or a value between any two of the following: 0.5mm, 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 7mm, 10mm, 12mm, 15mm, 17mm, and 20mm.

[0062] If the thickness of the non-oriented silicon steel layer 111 and / or the oriented silicon steel layer 112 is too small, such as less than 0.5 mm, the effective magnetic cross-sectional area of ​​the non-oriented silicon steel layer 111 and / or the oriented silicon steel layer 112 will be insufficient, making them easily magnetized and saturated by a strong magnetic field. The permeability will drop instantly to near air, causing the magnetic shunt function to fail. If the thickness of the non-oriented silicon steel layer 111 and / or the oriented silicon steel layer 112 is too large, such as greater than 20 mm, it will not effectively improve the anti-saturation capability of the non-oriented silicon steel layer 111 and / or the oriented silicon steel layer 112. On the contrary, the excessive thickness will increase eddy current losses, thereby reducing the shielding effectiveness in the mid-low frequency band above 1 kHz, and increasing the material cost and weight of the magnetic layer 110. By reasonably setting the thickness of the non-oriented silicon steel layer 111 and / or the oriented silicon steel layer 112, it is ensured that they have sufficient magnetic cross-sectional area, reducing the risk of shielding failure of the non-oriented silicon steel layer 111 and / or the oriented silicon steel layer 112; it can also effectively reduce the material cost and weight of the magnetic layer 110.

[0063] Furthermore, the thickness of the permalloy layer 113 can be any value or a value between any two of the following: 0.5mm, 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 7mm, 10mm, 12mm, 15mm, 17mm, and 20mm. If the thickness of the permalloy layer 113 is too small, such as less than 0.5mm, its effective magnetic flux carrying capacity will be insufficient, leading to local saturation even in weak magnetic environments. Excessive magnetic reluctance will prevent the complete confinement of residual magnetic field lines, thus failing to achieve an nT-level zero magnetic environment. If the thickness of the permalloy layer 113 is too large, such as greater than 20mm, its material cost will increase significantly, while its shielding effectiveness will not be effectively improved. By reasonably setting the thickness of the permalloy layer 113, it can achieve sufficient magnetic flux carrying capacity, effectively confining residual magnetic field lines and thus achieving an nT-level zero magnetic environment. Simultaneously, it can effectively reduce the material cost and weight of the magnetically conductive layer 110.

[0064] Furthermore, the thickness of the amorphous nanocrystalline layer 114 can be any value or a value between any two of 0.05mm, 0.07mm, 0.1mm, 0.12mm, 0.15mm, 0.17mm, 0.2mm, 0.22mm, and 0.25mm. If the thickness of the amorphous nanocrystalline layer 114 is too small, such as less than 0.05mm, the amorphous nanocrystalline layer 114 is prone to breakage and wrinkling, and the effective magnetic cross-sectional area is insufficient to carry the magnetic flux, and the shielding effect in the mid-to-low frequency band cannot meet the usage requirements. If the thickness of the amorphous nanocrystalline layer 114 is too large, such as greater than 0.25mm, the internal material of the amorphous nanocrystalline layer 114 will be shielded by the skin effect and cannot participate in magnetic shielding. Instead, it will increase the eddy current loop, leading to a decrease in magnetic permeability. At the same time, an excessively thick amorphous nanocrystalline layer 114 is a redundant design, increasing unnecessary material costs. By reasonably setting the thickness of the amorphous nanocrystalline layer 114, it is ensured that it has sufficient magnetic cross-sectional area to meet the shielding performance requirements of the mid-to-low frequency band; at the same time, design redundancy of the amorphous nanocrystalline layer 114 is avoided, which helps to reduce its material cost.

[0065] In one embodiment, the length of the shielding chamber 10 is L1, satisfying 1.5m≤L1≤8m, the width is W1, satisfying 1.5m≤W1≤8m, and the height is H1, satisfying 2m≤H1≤6m; the length of the shielding chamber 10 is L2, satisfying 1.55m≤L2≤9m, the width is W2, satisfying 1.55m≤W2≤9m, and the height is H2, satisfying 2.05m≤H2≤7m.

[0066] In this embodiment, the X direction is the length direction of the shielding chamber 10, the Y direction is the width direction of the shielding chamber 10, and the Z direction is the height direction of the shielding chamber 10. The length L1 inside the shielded chamber 10 can be any value or a value between any two of the following: 1.5m, 1.7m, 2m, 2.5m, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m, 7.5m, and 8m. The width W1 inside the shielded chamber 10 can be any value or a value between any two of the following: 1.5m, 1.7m, 2m, 2.5m, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m, 7.5m, and 8m. The height H1 inside the shielded chamber 10 can be any value or a value between any two of the following: 2m, 2.5m, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m, and 6m.

[0067] If the internal dimensions of the shielding chamber 10 are too small, when the length, width, and height of the shielding chamber 10 approach the interlayer spacing of the passive shielding layer 100, the magnetic reluctance at the corners of the shielding chamber 10 will decrease relatively, and magnetic field lines will leak from the seams and corners of the passive shielding layer 100, resulting in a decline in the shielding performance of the shielding chamber 10. By ensuring that the internal length and width of the shielding chamber 10 are greater than or equal to 1.5m, the stable low-frequency shielding performance of the shielding chamber 10 is guaranteed; it also facilitates the accommodation of test equipment and maintains an effective safe distance between the test equipment and the inner wall of the shielding chamber 10. By ensuring that the internal height of the shielding chamber 10 is greater than or equal to 2m, operators can stand normally and operate the test equipment inside the shielding chamber 10, while also meeting the vertical installation requirements of vertical test equipment.

[0068] If the cavity size within the shielding chamber 10 is too large, the risk of structural deformation and stress accumulation in the large-size passive shielding layer 100 increases. High-permeability materials such as permalloy and amorphous nanocrystalline materials are highly sensitive to stress; even slight deformation can lead to a significant decrease in magnetic permeability, causing irreversible degradation of the shielding effectiveness of the magnetic permeable layer 110. By ensuring that the length and width of the shielding chamber 10 are less than or equal to 8m, and the height is less than 6m, the overall structural strength of the shielding chamber 10 is guaranteed, reducing the risk of structural deformation and stress accumulation in the passive shielding layer 100, thereby ensuring the shielding effectiveness of the magnetic permeable layer 110. Simultaneously, this allows the shielding chamber 10 to meet various application scenarios such as single-person medical testing and magnetobiology research.

[0069] Furthermore, the external length L2 of the shielding chamber 10 can be any value or a value between any two of the following: 1.55mm, 1.7m, 2m, 2.5m, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m, 7.5m, 8m, 8.5m, and 9m; the external width W2 of the shielding chamber 10 can be 1.55mm, 1.7m, 2m, 2.5m, 3m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m, 7.5m, 8m, 8.5m, and 9m. The height H2 outside the shielding chamber 10 can be any value or a value between any two of the following: 0.5m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m, 7.5m, 8m, 8.5m, 9m; 2.05mm, 2.2m, 2.5m, 3m, 3.5m, 4m, 4.5m, 5m, 5.5m, 6m, 6.5m, 7m.

[0070] By ensuring that the external length and width of the shielding chamber 10 are greater than or equal to 1.55m and the external height is greater than or equal to 2.05m, the internal space requirements of the shielding chamber 10 are met. Furthermore, the passive shielding layer 100 can be transported through conventional building doorways or elevators, and quickly and modularly installed in standard laboratory rooms without requiring structural modifications, making it suitable for miniaturized and low-cost applications. Alternatively, by ensuring that the external length and width of the shielding chamber 10 are less than or equal to 9m and the external height is less than or equal to 7m, the shielding performance of the shielding chamber 10 is maintained while maximizing its internal usable space, making it suitable for a wider range of applications.

[0071] In one embodiment, the thickness of the conductive layer 120 is 1 mm to 30 mm.

[0072] In this embodiment, the thickness of the conductive layer 120 can be any value or a value between any two of the following: 1mm, 2m, 3m, 5m, 7m, 10m, 12m, 15m, 17m, 20m, 22m, 25m, 27m, and 30m. If the thickness of the conductive layer 120 is too small, such as less than 1mm, the eddy current intensity at lower frequencies will be insufficient, leading to a decrease in shielding effectiveness and an inability to effectively attenuate common external power frequency interference, thus failing to protect the inner magnetic conductive layer 110. If the thickness of the conductive layer 120 is too large, such as greater than 30mm, the material exceeding the skin depth cannot effectively participate in eddy current shielding, constituting a redundant design, resulting in insufficient improvement in shielding effectiveness and increased material costs. By reasonably setting the thickness of the conductive layer 120, the conductive layer 120 generates effective eddy currents to counteract the power frequency magnetic field; at the same time, the material cost of the conductive layer 120 and the weight of the board are effectively reduced.

[0073] Furthermore, the passive shielding layer 100 has two conductive layers 120 and three magnetically conductive layers 110, with each conductive layer 120 sandwiched between two adjacent magnetically conductive layers 110. If there is only an air gap between two adjacent magnetically conductive layers 110, the leakage magnetic field and alternating magnetic field of the outer magnetically conductive layer 110 will directly couple to the inner magnetically conductive layer 110, leading to hysteresis loss and decreased permeability in the inner permalloy layer 113. Moreover, it causes residual magnetism to gradually accumulate, increasing the workload of the synchronous demagnetization system. By first using the outer conductive layer 120 to cancel out most of the alternating magnetic field leaking from the outer magnetically conductive layer 110, and then using the inner conductive layer 120 for secondary isolation, the magnetic coupling between the two magnetically conductive layers 110 is blocked, allowing the inner magnetically conductive layer 110 to operate in a stable weak magnetic and low alternating interference environment, while effectively reducing the control pressure of the demagnetization system. Furthermore, by matching the large skin depth requirement of the outer conductive layer 120 in the low-frequency band, sufficiently strong eddy currents are generated to cancel low-frequency interference; the inner conductive layer 120 matches the extremely small skin depth in the high-frequency band, avoiding eddy current loss of the thick plate at high frequencies, thus making the shielding efficiency higher. Through the cooperation of the two conductive layers 120 and the magnetic layer 110, the magnetic permeability of the magnetic layer 110 is prevented from decreasing rapidly in the mid-to-high frequency band due to eddy current loss. Combined with the DC or extremely low frequency shielding capability of the magnetic layer 110, full-band coverage without dead zones from 0Hz to 10kHz is achieved.

[0074] In one embodiment, the demagnetizing coil 200 is arranged along the edge of the shielding chamber 10 inside the shielding chamber 10; or the demagnetizing coil 200 is arranged evenly in a cross shape inside the shielding chamber 10.

[0075] In this embodiment, the shielding chamber 10 has a cuboid structure with 12 edges. The demagnetizing coil 200 is closely attached to the inner wall of the magnetic conductive layer 110 along the 12 edges, forming a closed rectangular demagnetizing coil 200 with three orthogonal axes (X, Y, and Z). The X-axis coil is arranged along the four edges along the length of the shielding chamber 10, corresponding to canceling the residual magnetism and magnetization intensity in the length direction; the Y-axis coil is arranged along the four edges along the width of the chamber, corresponding to canceling the residual magnetism and magnetization intensity in the width direction; and the Z-axis coil is arranged along the four edges along the height of the chamber, corresponding to canceling the residual magnetism and magnetization intensity in the height direction. The three axial coils are completely orthogonal and have no magnetic field coupling, allowing direct connection to a single multi-channel synchronous power modulation system to achieve independent synchronous control of the three channels. By arranging the demagnetizing coil 200 along the edges of the shielding chamber 10, the wiring of the demagnetizing coil 200 is neat and easy to fix; at the same time, the installation difficulty is low, the labor cost is low, and the later maintenance and repair are convenient.

[0076] In other possible implementations, the demagnetizing coils 200 are arranged in a cross-shaped, uniform manner within the shielded chamber 10. On the inner surface of the magnetically conductive layer 110 on the six sides of the shielded chamber 10, a planar coil array is laid out in a cross-shaped, uniformly distributed manner along the length and width of each side, forming a grid-like demagnetizing coil array 200 covering all highly magnetically conductive surfaces of the entire chamber. The coils on each shielded surface are arranged orthogonally within the surface, with no magnetic field coupling. Furthermore, depending on the size of the surface, the cross-shaped grid can be divided into multiple independent sub-coil loops, all of which are connected to a single multi-channel synchronous power modulation system to achieve independent synchronous control across the entire area. By arranging the demagnetizing coils 200 in a cross-shaped, uniform manner, the reverse magnetic field can uniformly cover every area of ​​the magnetically conductive layer 110, achieving precise residual magnetism cancellation even at edges and the center of large surfaces, thus solving the problem of uneven demagnetization in large-sized chambers. The grid-like sub-coils can be independently connected to a single multi-channel synchronous power modulation system. For areas of abnormal residual magnetism or uneven magnetization in the magnetic layer 110, the drive current can be adjusted individually to meet the dynamic demagnetization requirements in complex magnetic field environments. Moreover, the cross-shaped demagnetizing coils 200 can break the closed eddy current loops within the surface of the magnetic layer 110, reducing eddy current losses under alternating magnetic fields. This, combined with the thin single-board stacked design of the magnetic layer 110, further enhances the shielding effectiveness in the 0kHz-10kHz mid-low frequency range.

[0077] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0078] The specific embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A composite passive magnetic shielding system suitable for low-frequency magnetic field suppression, characterized in that, include: The shielding chamber (10) is a cuboid structure formed by several passive shielding layers (100); The passive shielding layer (100) includes at least one magnetically conductive layer (110) and at least one conductive layer (120), and the magnetically conductive layer (110) and the conductive layer (120) are sequentially spliced ​​to form the passive shielding layer (100). The demagnetizing system includes a demagnetizing coil (200) and a single multi-channel synchronous power modulation system. The demagnetizing coil (200) is wound on the magnetic conductive layer (110). The single multi-channel synchronous power modulation system is electrically connected to the demagnetizing coil (200) and is used to synchronously reduce the magnetism of the magnetic conductive layer (110).

2. The composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 1, characterized in that, The number of magnetic conductive layers (110) is N, and the number of conductive layers (120) is M, satisfying 1≤M≤N≤8.

3. A composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 1, characterized in that, Each of the magnetic conductive layers (110) is formed by stacking several single plates and splicing them together in a staggered manner.

4. A composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 3, characterized in that, The number of single plates in each magnetic conductive layer (110) is n, satisfying 2≤n≤10; the thickness of the single plate is d, satisfying 0.025mm≤d≤2mm.

5. A composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 1, characterized in that, Each of the magnetically conductive layers (110) is formed of at least one of a non-oriented silicon steel layer (111), an oriented silicon steel layer (112), a permalloy layer (113), and an amorphous nanocrystalline layer (114); The conductive layer (120) includes any one of a copper layer, an aluminum layer, and an aluminum-based copper clad layer.

6. A composite passive magnetic shielding system suitable for low-frequency magnetic field suppression according to claim 5, characterized in that, The thickness of the non-oriented silicon steel layer (111) is 0.5mm-20mm; the thickness of the oriented silicon steel layer (112) is 0.5mm-20mm; the thickness of the permalloy layer (113) is 0.5mm-20mm; and the thickness of the amorphous nanocrystalline layer (114) is 0.05mm-0.25mm.

7. A composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 5, characterized in that, The magnetic conductive layer (110) is formed by combining a non-oriented silicon steel layer (111), an oriented silicon steel layer (112), a permalloy layer (113), and an amorphous nanocrystalline layer (114). The spacing between the oriented silicon steel layer (112) and the permalloy layer (113) is 20mm-800mm, and the spacing between the amorphous nanocrystalline layer (114) and the permalloy layer (113) is 10mm-500mm.

8. A composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 1, characterized in that, The length of the shielding chamber (10) is L1, which satisfies 1.5m≤L1≤8m; the width is W1, which satisfies 1.5m≤W1≤8m; and the height is H1, which satisfies 2m≤H1≤6m. The length of the shielding chamber (10) is L2, which satisfies 1.55m≤L2≤9m, the width is W2, which satisfies 1.55m≤W2≤9m, and the height is H2, which satisfies 2.05m≤H2≤7m.

9. A composite passive magnetic shielding system suitable for low-frequency magnetic field suppression according to claim 1, characterized in that, The thickness of the conductive layer (120) ranges from 1 mm to 30 mm.

10. A composite passive magnetic shielding system for low-frequency magnetic field suppression according to claim 1, characterized in that, The demagnetizing coil (200) is arranged along the edge of the shielding chamber (10) inside the shielding chamber (10); or The demagnetizing coils (200) are arranged in a cross shape and evenly inside the shielding chamber (10).

Images