Miniature mutual inductor with electromagnetic interference resistance

Abstract

The utility model provides a kind of miniature mutual inductor of anti-electromagnetic interference, including anti-magnetic shell, the positioning column of the anti-magnetic shell inside integral setting is described, the mutual inductor coil is positioned by the positioning column inside the anti-magnetic shell, the pin of the mutual inductor coil is described and is worn outside in the pin mouth of the anti-magnetic shell, the sealing body is poured in the anti-magnetic shell inside, the sealing cover inside surface of the anti-magnetic shell opening position is provided with the occlusal projection, the anti-magnetic shell and sealing cover are provided with corresponding detection port;The utility model constitutes complete shielding cabin with anti-magnetic shell, sealing cover and coating, blocks electromagnetic interference;Internal positioning column accurately limits mutual inductor coil, guarantees parameter consistency and reliability;Sealing cover occlusal projection and sealing body interlock, enhance bonding strength, guarantee shielding effect and service life.

Description

Technical Field

[0001] This utility model belongs to the field of miniature current transformer technology, and in particular relates to a miniature current transformer that is resistant to electromagnetic interference. Background Technology

[0002] As power electronics technology develops towards higher frequencies, higher densities, and greater integration, the electromagnetic environment in circuit systems is becoming increasingly complex, posing a severe challenge to the accuracy and reliability of current and voltage sampling devices. Miniature current transformers, as key signal sensing elements, are widely used in new energy vehicles, smart grids, industrial frequency conversion, and aerospace fields.

[0003] In existing technologies, to achieve miniaturization and insulation protection, epoxy resin and other materials are often used to integrally encapsulate the current transformer coil. However, this conventional encapsulation method has significant shortcomings: First, ordinary plastic or resin shells do not have electromagnetic shielding capabilities, making the internal current transformer coil highly susceptible to interference from complex external electromagnetic environments, leading to signal distortion and decreased measurement accuracy. Second, during the casting process, the coil is prone to displacement due to fluid pressure, making it difficult to ensure its centered position within the shell. This not only affects the symmetry of the magnetic circuit and causes inconsistent electrical parameters but may also lead to safety hazards due to uneven local insulation thickness. Furthermore, if the seal between the shell and the cover is not tight or the connection is unreliable, electromagnetic leakage gaps can easily form, affecting the product's mechanical strength and environmental adaptability.

[0004] Therefore, it is essential to invent a miniature current transformer that is resistant to electromagnetic interference. Utility Model Content

[0005] To address the aforementioned technical problems, this utility model provides a miniature current transformer resistant to electromagnetic interference, comprising an antimagnetic housing, a positioning post, a current inductor coil, pins, pin openings, a sealing body, a sealing cover, an engagement protrusion, and a detection port. The positioning post is integrally disposed inside the antimagnetic housing, and the current inductor coil is limited by the positioning post inside the antimagnetic housing. The pins of the current inductor coil protrude through the pin openings of the antimagnetic housing. The sealing body is cast inside the antimagnetic housing, and the engagement protrusion is provided on the inner surface of the sealing cover at the opening of the antimagnetic housing. The antimagnetic housing and the sealing cover are provided with corresponding detection ports.

[0006] Preferably, the protrusion height of the positioning post can limit the mutual inductance coil to a central position inside the antimagnetic shell, and a plurality of positioning posts are arranged in a circular array.

[0007] Preferably, the excess space inside the antimagnetic shell is filled by the cast sealing body, which encloses the mutual inductance coil located in the center.

[0008] Preferably, one side opening of the antimagnetic shell is closed by the sealing cap, and the interlocking protrusions arranged in a circular array on the inner surface of the sealing cap interlock with the sealing body filled inside the antimagnetic shell.

[0009] Preferably, both the antimagnetic shell and the sealing cover are made of electromagnetic interference-resistant materials, and both are coated with an electromagnetic interference-resistant coating. Together, the antimagnetic shell and the sealing cover constitute the shell structure of the miniature transformer.

[0010] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes an antimagnetic shell and sealing cover made of anti-electromagnetic interference material, along with an anti-electromagnetic interference coating on their surface, to form a continuous and complete electromagnetic shielding chamber. This structure effectively blocks external high-frequency electromagnetic waves and low-frequency magnetic field interference, providing a "clean" working environment for the internal mutual inductance coils, fundamentally ensuring the purity and accuracy of signal acquisition.

[0011] This invention innovatively incorporates a circular array of positioning posts integrated within the antimagnetic housing. This design allows for precise positioning during casting, ensuring the mutual inductance coil remains at the geometric center within the housing. This not only guarantees the symmetry of the magnetic circuit, resulting in high consistency of electrical parameters (such as turns ratio and phase) in mass production, but also ensures a uniform thickness of the insulation layer around the coil, improving the product's insulation withstand voltage rating and long-term reliability.

[0012] The interlocking protrusions on the inner side of the sealing cap of this utility model interlock with the cured sealing body to form a strong mechanical interlocking structure. This design greatly enhances the bonding strength between the outer shell and the sealing cap, effectively preventing the cap from loosening or detaching due to vibration, impact, or thermal cycling, ensuring the integrity of the shielding effect and the product's service life under harsh working conditions. Attached Figure Description

[0013] Figure 1 This is an exploded structural diagram of the present invention.

[0014] Figure 2 This is a schematic diagram of the overall structure of this utility model.

[0015] Figure 3 This is a schematic diagram of the internal structure of the antimagnetic shell of this utility model.

[0016] In the picture: 1. Antimagnetic housing; 2. Positioning post; 3. Mutual inductance coil; 4. Pin; 5. Pin port; 6. Sealing body; 7. Sealing cover; 8. Engaging protrusion; 9. Detection port. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 should fall within the protection scope of the present invention.

[0018] In the description of the embodiments, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of the utility model, it should be noted that unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in the present utility model based on the specific circumstances.

[0019] As attached Figure 1 To be continued Figure 3 As shown: This utility model provides a miniature current transformer for electromagnetic interference suppression, comprising an antimagnetic housing 1, a positioning post 2, a current inductor coil 3, pins 4, pin openings 5, a sealing body 6, a sealing cover 7, an engagement protrusion 8, and a detection port 9. The positioning post 2 is integrally disposed inside the antimagnetic housing 1. The current inductor coil 3 is limited by the positioning post 2 inside the antimagnetic housing 1. The pins 4 of the current inductor coil 3 protrude outside through the pin openings 5 ​​of the antimagnetic housing 1. The sealing body 6 is cast inside the antimagnetic housing 1. The engagement protrusion 8 is provided on the inner surface of the sealing cover 7 at the opening position of the antimagnetic housing 1. The antimagnetic housing 1 and the sealing cover 7 are provided with corresponding detection ports 9.

[0020] Furthermore, the positioning post (2) and the antimagnetic shell (1) are manufactured using an integrated injection molding process. The positioning post (2) is made of insulating engineering plastic with low dielectric constant and low eddy current loss, such as PEEK or ceramic-filled epoxy resin. The number of positioning posts 2 is preferably 3-4, which are evenly arranged in a circular array on the inner bottom surface of the antimagnetic shell 1. The center of the array coincides with the geometric center of the antimagnetic shell 1 to ensure the uniformity of the limiting of the mutual inductance coil 3. The protrusion height H of the positioning post 2 is designed to be 1 / 2 to 2 / 3 of the height of the mutual inductance coil 3 (for example, when the height of the mutual inductance coil 3 is 8mm, H is 5mm). Its top end face is in contact with the outer wall of the mutual inductance coil 3, and the contact surface is polished. The mutual inductance coil 3 is stably restricted to the central position inside the antimagnetic shell 1 through a three-point (or four-point) support structure. That is, the axis of the mutual inductance coil 3 coincides with the axis of the antimagnetic shell 1, and the distance error between the outer wall of the coil and the inner wall of the antimagnetic shell 1 is controlled within ±0.1mm, which effectively avoids the problem of uneven distribution of parasitic capacitance caused by coil offset.

[0021] Furthermore, apart from the space occupied by the positioning post 2 and the mutual inductance coil 3, the remaining space inside the antimagnetic shell 1 is filled with the sealing body 6 using a vacuum pressure casting process. The sealing body 6 is made of modified epoxy resin material with a dielectric strength ≥30kV / mm and a volume resistivity ≥10¹. 4 Ω·cm, possessing both high insulation and mechanical strength. During the casting process, the antimagnetic outer shell 1 is first placed in a vacuum chamber for degassing for 30 minutes. Then, pressure injection is used to completely saturate the winding gap of the mutual inductance coil 3 and the fitting gap between the positioning post 2 and the coil, ultimately forming an integral structure without air bubbles or voids. After curing, the sealing body 6 completely encloses the mutual inductance coil 3 in the central position. Its outer surface is tightly fitted to the inner wall of the antimagnetic outer shell 1, forming a mechanical lock with the positioning post 2. This not only blocks the coupling path of external electromagnetic signals through the air gap but also further ensures that the central position of the mutual inductance coil 3 does not shift through physical fixation.

[0022] Furthermore, the opening on one side of the antimagnetic shell 1 adopts a stepped structure design, with a 1mm wide sealing groove at the edge of the opening. The edge of the sealing cover 7 has corresponding raised sealing ribs, achieving initial sealing with the antimagnetic shell 1 through a transition fit (fitting gap 0.02-0.05mm). The interlocking protrusions 8 on the inner surface of the sealing cover 7 are arranged in a circular array, their number matching that of the positioning posts 2, and the center of the array coincides with the geometric center of the sealing cover 7, ensuring positional correspondence with the positioning posts 2. The interlocking protrusions 8 adopt a conical structure, made of the same material as the sealing cover 7 (anti-electromagnetic interference composite board). Before the sealing body 6 is fully cured, the sealing cover 7 is fastened, allowing the interlocking protrusions 8 to embed inside the sealing body 6. After the sealing body 6 is fully cured, the protrusions and the sealing body 6 form a mechanical interlocking structure with a pull-out force ≥50N, effectively preventing the sealing cover 7 from loosening. This structure eliminates the gaps of traditional snap-fit ​​connections and enhances the integrity of the sealing cover 7 and the antimagnetic shell 1 through interlocking, preventing electromagnetic signals from intruding from the joints.

[0023] Furthermore, both the antimagnetic outer shell 1 and the sealing cover 7 adopt a composite structure of "outer layer high conductivity material + inner layer high magnetic permeability material": the outer layer is an oxygen-free copper alloy (conductivity ≥98% IACS) used to shield external electric fields; the inner layer is permalloy (Ni80Fe20, initial permeability ≥80000) used to attenuate low-frequency magnetic fields. The two are bonded together using a diffusion welding process, with a conductivity ≥10 at the joint. 6 S / m, ensuring the continuity of the shielding. A uniform anti-electromagnetic interference coating is applied to both the outer and inner surfaces of the antimagnetic outer shell 1 and the sealing cover 7. The coating uses a nickel-phosphorus alloy chemical plating, which further enhances the reflection and absorption capabilities of high-frequency electromagnetic radiation. When the sealing cover 7 is fastened to the antimagnetic outer shell 1, the composite structure of the two, together with the coating, forms a complete closed shielding body with a shielding effectiveness of 10kHz. Z -1GH Z It reaches 60-80dB within the frequency band, achieving all-round shielding against electric fields, magnetic fields and electromagnetic radiation.

[0024] The working principle is as follows: First, when there is external electric field, magnetic field or electromagnetic radiation interference, the closed shielding body composed of the antimagnetic shell 1 and the sealing cover 7 plays its role: the oxygen-free copper alloy on the outer layer of the antimagnetic shell 1 and the sealing cover 7 can reflect and conduct the external electric field, preventing the electric field from entering the interior through spatial coupling; the permalloy on the inner layer guides the external low-frequency magnetic field to propagate along its own path through its high magnetic permeability, reducing the intensity of the magnetic field entering the interior through the shielding body; the nickel-phosphorus alloy coating on the surface of both further absorbs and attenuates high-frequency electromagnetic radiation, so that most of the interference is weakened before reaching the internal mutual inductance coil 3.

[0025] Secondly, the positioning post 2 uses a three-point (or four-point) support structure to stably restrict the mutual inductance coil 3 to the central position of the antimagnetic shell 1, ensuring that the distance between the mutual inductance coil 3 and the inner wall of the antimagnetic shell 1 is uniform, avoiding strong capacitive coupling caused by the coil offset and the local area being too close to the shell, thereby reducing the interference signal of the external electric field coupled to the mutual inductance coil 3 through parasitic capacitance.

[0026] Furthermore, the sealing body 6 inside the antimagnetic shell 1 completely encloses the mutual inductance coil 3 and fits tightly with the positioning post 2 and the inner wall of the antimagnetic shell 1, eliminating the internal air gap—which could become a channel for electromagnetic signal coupling. The high insulation properties of the sealing body 6 can block the path of interference signal coupling through the medium, while the physical fixation further maintains the centered position of the mutual inductance coil 3, ensuring the stability of the anti-interference state.

[0027] Then, the interlocking protrusion 8 on the inner side of the sealing cover 7 is embedded into the sealing body 6 and forms a mechanical interlock, so that the sealing cover 7 and the antimagnetic shell 1 are tightly combined, eliminating the gap at the connection between the two and preventing external interference signals from seeping in from the joint; at the same time, the sealing ribs on the edge of the sealing cover 7 cooperate with the sealing groove of the antimagnetic shell 1, further enhancing the sealing performance of the shield and ensuring that the shielding continuity of the entire shell structure is not affected by the connection.

[0028] Finally, under the protection of the above-mentioned multiple anti-interference structures, the mutual inductance coil 3 can stably sense the measured electrical signal. When its pin 4 passes through the pin port 5, the isolation effect of the antimagnetic shell 1 and the sealing body 6 reduces the influence of external interference on the signal transmitted by the pin 4. When the detection port 9 needs to be tested, it is within the shielding range of the antimagnetic shell 1 and the sealing cover 7, so performance testing can be carried out without destroying the overall shielding effectiveness, ensuring the accuracy of the output signal of the mutual inductance coil 3.

[0029] Any technical solution that achieves the above-mentioned technical effects by utilizing the technical solution described in this utility model, or by designing a similar technical solution inspired by the technical solution described in this utility model, falls within the protection scope of this utility model.

Claims

1. A miniature current transformer resistant to electromagnetic interference, characterized in that, The device includes an antimagnetic shell (1), a positioning post (2), a mutual inductance coil (3), a pin (4), a pin opening (5), a sealing body (6), a sealing cover (7), an engagement protrusion (8), and a detection port (9). The positioning post (2) is integrally disposed inside the antimagnetic shell (1). The mutual inductance coil (3) is limited by the positioning post (2) inside the antimagnetic shell (1). The pin (4) of the mutual inductance coil (3) protrudes out through the pin opening (5) of the antimagnetic shell (1). The sealing body (6) is cast inside the antimagnetic shell (1). The engagement protrusion (8) is disposed on the inner surface of the sealing cover (7) at the opening of the antimagnetic shell (1). The antimagnetic shell (1) and the sealing cover (7) are provided with corresponding detection ports (9).

2. The miniature current transformer with electromagnetic interference suppression as described in claim 1, characterized in that: The protrusion height of the positioning post (2) can limit the mutual inductance coil (3) to the central position inside the antimagnetic shell (1), and several positioning posts (2) are arranged in a circular array.

3. The miniature current transformer with electromagnetic interference suppression as described in claim 2, characterized in that: The excess space inside the antimagnetic shell (1) is filled by the cast sealing body (6), which encloses the mutual inductance coil (3) in the central position.

4. The miniature current transformer for electromagnetic interference suppression as described in claim 3, characterized in that: The opening on one side of the antimagnetic shell (1) is closed by the sealing cover (7), and the interlocking protrusions (8) arranged in a circular array on the inner surface of the sealing cover (7) interlock with the sealing body (6) filled inside the antimagnetic shell (1).

5. A miniature current transformer for electromagnetic interference suppression as described in claim 4, characterized in that: The antimagnetic shell (1) and the sealing cover (7) are both made of anti-electromagnetic interference material. Both of them are coated with an anti-electromagnetic interference coating. The antimagnetic shell (1) and the sealing cover (7) together constitute the shell structure of the miniature transformer.

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