Magnetic balance current transformer

Abstract

The utility model relates to the technical field of mutual inductors, in particular to a magnetic balance current transformer which comprises a mutual inductor body, and the mutual inductor body comprises a magnetic core, a primary winding, a secondary winding and an epoxy resin layer wrapping the mutual inductor body. The outer side of the epoxy resin layer is encapsulated with a metal shell; the metal shell is made of an aluminum alloy material, and the lining is provided with a soft magnetic adhesive tape layer; a shielding layer formed by attaching a semi-conductive adhesive tape is arranged on a lining of the soft magnetic adhesive tape layer; the two ends of a wire of the primary winding penetrate through the epoxy resin layer and the metal shell and extend out of the metal shell, and the two ends of the wire of the primary winding are sleeved with insulating sleeves. The two ends of a wire of the secondary winding penetrate through the epoxy resin layer and the metal shell and extend out of the metal shell, and the two ends of the wire of the secondary winding are also sleeved with insulating sleeves. The insulating sleeve is arranged between the wire and the metal shell; an external magnetic field is shielded through the metal shell, and the measurement precision of the current transformer is improved.

Description

Technical Field

[0001] The present application relates to the technical field of transformers, and in particular to a current transformer. Background Art

[0002] The magnetic balance current transformer is a sensor used to measure current. Its principle is to introduce an additional magnetic field into the current path to achieve magnetic balance by making the magnetic field inside the sensor and the magnetic field of the current being measured cancel each other out. In this way, by measuring the additional current used to cancel the magnetic field, the value of the measured current can be indirectly obtained, which cancels the core loss and improves the measurement accuracy of the current transformer.

[0003] However, in some multi-line locations, interference from external magnetic fields may affect the measurement accuracy of magnetically balanced current transformers, resulting in errors. Utility Model Content

[0004] The purpose of this section is to summarize some aspects of the embodiments of the utility model and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract of the specification and the name of the utility model of this application to avoid blurring the purpose of this section, the abstract of the specification and the name of the utility model, and such simplifications or omissions cannot be used to limit the scope of the utility model.

[0005] In view of the above problems and / or the problems existing in the prior art, the present utility model is proposed.

[0006] In order to solve the above technical problems, the utility model provides the following technical solutions:

[0007] A magnetically balanced current transformer comprises a transformer, wherein the transformer comprises a magnetic core, a primary winding and a secondary winding, wherein the secondary winding is connected to a magnetically balanced transformer:

[0008] Also includes an epoxy resin layer wrapping the mutual inductor;

[0009] The epoxy resin layer is encapsulated with a metal shell outside;

[0010] The metal shell is made of aluminum alloy, and the inner lining is provided with a soft magnetic tape layer;

[0011] The inner lining of the soft magnetic tape layer is provided with a shielding layer formed by bonding a semi-conductive tape;

[0012] Both ends of the wire of the primary winding pass through the epoxy resin layer and the metal shell and extend out of the metal shell, and both ends of the wire of the primary winding are covered with insulating sleeves;

[0013] Both ends of the wire of the secondary winding pass through the epoxy resin layer and the metal shell and extend out of the metal shell. Both ends of the wire of the secondary winding are also covered with insulating sleeves.

[0014] The insulating sleeve is arranged between the wire and the metal shell.

[0015] The above design firstly wraps the mutual inductor in epoxy resin by setting an epoxy resin layer, and encapsulates a metal shell on the outside of the metal shell to improve the stability of the mutual inductor. The metal shell can shield the external magnetic field and current, reduce the external magnetic field interference, and improve the measurement accuracy of the current transformer; the metal shell is also provided with a shielding layer formed by winding a semi-conductive tape and a soft magnetic tape layer, so as to further improve the electromagnetic shielding ability of the metal shell and further improve the measurement accuracy of the current transformer; finally, insulating sleeves are set at both ends of the wires of the primary winding and the secondary winding to prevent the wires of the primary winding and the secondary winding from short-circuiting, thereby improving the stability of the magnetically balanced current transformer; the magnetic balancing transformer of the magnetically balanced current transformer is connected to the wire of the secondary winding, and an additional magnetic field is introduced into the measured current path through the magnetic balancing transformer to balance the magnetic field of the primary winding, so that the magnetic field inside the sensor and the magnetic field of the measured current cancel each other, thereby achieving magnetic balance, and then testing the current that generates the offset magnetic field to measure the current of the measured circuit, thereby offsetting the core loss and shielding the influence of the external magnetic field, and improving the measurement accuracy.

[0016] Preferably, a support base is connected to the lower side of the metal shell, and the support base is provided with a grounding terminal connected to the aluminum alloy layer; a grounding terminal is provided on the metal shell, and the grounding terminal is connected to the aluminum alloy layer, so that the metal shell can be grounded to ensure safety and reduce electromagnetic interference.

[0017] Preferably, the outer layer of the epoxy resin layer adopts a material layer of epoxy resin mixed with soft magnetic powder, which is called a soft magnetic epoxy resin mixed layer, and the soft magnetic epoxy resin mixed layer is compounded on the outside of the epoxy resin layer; by optimizing the structure of the epoxy resin layer, after optimization, the soft magnetic epoxy resin mixed layer is used to reduce the influence of the external magnetic field on the mutual inductor.

[0018] Preferably, the shielding layer is made of a copper foil material layer coated with a polyimide film and a carbon black polymer; the structure of the shielding layer is optimized to a combination material of a polyimide film, a carbon black polymer and a copper foil, thereby improving the electromagnetic shielding capability of the shielding layer and thus improving the measurement accuracy of the current transformer.

[0019] Preferably, the metal shell is also wrapped with a layer of mesh woven from nylon fibers containing stainless steel wires, called a shielding mesh; by providing the shielding mesh, the shielding layer can effectively shield the interference of the external electromagnetic field on the current transformer, further optimizing the measurement accuracy of the current transformer.

[0020] Preferably, the metal shell is provided with a threaded hole connected to the support seat, the threaded hole is configured as a blind hole that does not pass through the metal shell, at least two threaded holes are arranged, and at least one threaded hole is provided on the front and rear surfaces of the metal shell.

[0021] The support seat is provided with through holes, the number of the through holes is consistent with the threaded holes and the positions correspond one to one, the threaded holes are provided with screws in cooperation with the threads, and the screws pass through the through holes and cooperate with the threaded holes to fix the support seat and the metal shell; by providing a support seat threadedly connected to the metal shell, the replacement of the support seat is convenient, thereby facilitating the maintenance of the current transformer.

[0022] Preferably, the support seat is made of phenolic resin material. By providing the support seat made of phenolic resin material, the support seat is insulated, so that external leakage will be isolated by the insulating seat, thereby improving the stability of the current transformer.

[0023] Preferably, both ends of the wires of the primary winding and the secondary winding are connected with wiring terminals, and the wiring terminals are made of polyimide material; by arranging wiring terminals at both ends of the wires, it is convenient to connect the mutual inductor to the circuit, and to use the mutual inductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0025] Figure 1 A schematic diagram of the overall structure of a magnetically balanced current transformer according to an embodiment of the present utility model;

[0026] Figure 2 A schematic diagram of a cross-sectional structure of a magnetically balanced current transformer according to an embodiment of the present utility model;

[0027] Figure 3 A schematic diagram of the explosion structure of a current transformer and a metal casing in a magnetically balanced current transformer according to an embodiment of the utility model. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purposes, features and advantages of the present invention more understandable, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general proportion, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0031] Secondly, the "one embodiment" or "embodiment" referred to herein refers to a specific feature, structure or characteristic that can be included in at least one implementation of the utility model. The "in one embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0032] Example 1

[0033] Reference Figure 1 to Figure 3 This embodiment provides a magnetic balance current transformer including a transformer, the transformer includes a magnetic core 4, a primary winding 41 and a secondary winding 42, and the secondary winding 42 is connected to a magnetic balance transformer.

[0034] The invention also includes an epoxy resin layer 3 wrapping the mutual inductor; a metal shell 1 is provided on the outer side of the epoxy resin layer 3; the metal shell 1 is made of aluminum alloy, and is lined with a soft magnetic tape layer; the soft magnetic tape layer is lined with a shielding layer 2 formed by bonding a semi-conductive tape; both ends of the wire of the primary winding 41 pass through the epoxy resin layer 3 and the metal shell 1, and extend from the metal shell 1, and both ends of the wire of the primary winding 41 are covered with insulating sleeves; both ends of the wire of the secondary winding 42 pass through the epoxy resin layer 3 and the metal shell 1, and extend from the metal shell 1, and both ends of the wire of the secondary winding 42 are also covered with insulating sleeves; the insulating sleeve is arranged between the wire and the metal shell 1; by arranging the epoxy resin layer 3, the mutual inductor is wrapped in the epoxy resin layer 3. In the embodiment, the metal shell 1 is encapsulated on the outside of the metal shell 1 to improve the stability of the current transformer. The metal shell 1 can shield the external magnetic field and current, reduce the external magnetic field interference, and improve the measurement accuracy of the current transformer. The metal shell 1 is also provided with a shielding layer 2 wound with a semi-conductive tape and a soft magnetic tape layer to further improve the electromagnetic shielding ability of the metal shell 1 and further improve the measurement accuracy of the current transformer. Finally, insulating sleeves are provided at both ends of the wires of the primary winding 41 and the secondary winding 42 to prevent the wires of the primary winding 41 and the secondary winding 42 from being short-circuited, thereby improving the stability of the magnetically balanced current transformer. The magnetic core 4 is a magnetic core 4 of an annular iron-based nanocrystalline material, and the primary winding 41 and the secondary winding 42 are both wound on the magnetic core 4.

[0035] The magnetic balancing transformer (dynamic compensation circuit) of the magnetic balancing current transformer is connected to the wire of the secondary winding 42. An additional magnetic field is introduced into the measured current path through an external power supply and the magnetic balancing transformer to balance the magnetic field of the primary winding 41, so that the magnetic field inside the sensor and the magnetic field of the measured current cancel each other out, thereby achieving magnetic balance. The current that generates the offset magnetic field is then tested to measure the current of the measured circuit, thereby offsetting the loss of the magnetic core 4, shielding the influence of the external magnetic field, and improving the measurement accuracy.

[0036] A support base 5 is connected to the lower side of the metal shell 1, and the support base 5 is provided with a grounding column 6 which is conductive with the aluminum alloy layer; the grounding column 6 is provided on the metal shell 1, and the grounding column 6 is conductive with the aluminum alloy layer, so that the metal shell 1 can be grounded to ensure safety and reduce electromagnetic interference.

[0037] The outer layer of the epoxy resin layer 3 is a material layer of epoxy resin mixed with soft magnetic powder, called a soft magnetic epoxy resin mixed layer, which is compounded on the outside of the epoxy resin layer 3; by optimizing the structure of the epoxy resin layer 3, after optimization, the soft magnetic epoxy resin mixed layer is used to reduce the influence of the external magnetic field on the mutual inductor.

[0038] The shielding layer 2 is made of a copper foil material layer coated with a polyimide film and a carbon black polymer; the structure of the shielding layer 2 is optimized to be a composite material of a polyimide film, a carbon black polymer and a copper foil, thereby improving the electromagnetic shielding capability of the shielding layer 2 and thus improving the measurement accuracy of the current transformer.

[0039] The metal shell 1 is also wrapped with a layer of mesh woven from nylon fibers containing stainless steel wires, called a shielding mesh 7. By providing the shielding mesh 7, the shielding layer 2 can effectively shield the interference of the external electromagnetic field on the current transformer, further optimizing the measurement accuracy of the current transformer.

[0040] When in use, first put the mutual inductor into the mold for pouring the epoxy resin layer 3, pour the hot-melt epoxy resin on the mutual inductor, and fill the middle through hole of the magnetic ring. After the epoxy resin solidifies, pour the hot-melt epoxy resin mixed with soft magnetic powder on the surface of the magnetic ring with solidified epoxy resin to form a soft magnetic epoxy resin mixed layer. The epoxy resin layer 3 is completely solidified, and the metal shell 1 has an openable cover and a hole for the wire to pass through. The soft magnetic tape layer is also lined on the inner surface of the metal shell 1, and then the copper foil shielding layer 2 coated with polyimide film and carbon black polymer is lined on the inner surface of the soft magnetic tape layer. The cover of the metal shell 1 is also lined with the soft magnetic tape layer and the shielding layer 2. Wrap the ring The magnetic core 4 of the epoxy resin layer 3 is installed in the metal shell 1 and sealed with the cover of the metal shell 1, only the wires at both ends of the primary winding 41 and the secondary winding 42 are leaked, and then the metal shell 1 is wrapped with a shielding net 7, and the support base 5 is installed. The current transformer is installed, and then the primary winding 41 is connected to the circuit to be tested, and the secondary winding 42 is connected to the magnetic balance transformer. The magnetic balance current transformer works. When the secondary winding 42 offsets the magnetic field, the shielding net 7, the metal shell 1, the soft magnetic tape layer and the shielding layer 2 are used to shield the external magnetic field, so as to improve the measurement accuracy of the magnetic balance current transformer, and the additional current used to offset the magnetic field is measured to obtain the value of the measured current.

[0041] Example 2

[0042] Reference Figure 1 and Figure 3 , which is the second embodiment of the utility model, and this embodiment is based on the previous embodiment.

[0043] The metal shell 1 is provided with a threaded hole connected to the support seat 5 . The threaded hole is provided as a blind hole that does not pass through the metal shell 1 . There are at least two threaded holes arranged in an array. At least one threaded hole is provided on the front and rear surfaces of the metal shell 1 .

[0044] The support seat 5 is provided with through holes, the number of the through holes is consistent with the threaded holes and the positions correspond one to one, the threaded holes are provided with screws in cooperation with the threads, the screws pass through the through holes and cooperate with the threaded holes to fix the support seat 5 and the metal shell 1; the support seat 5 is threadedly connected to the metal shell 1; the replacement of the support seat 5 is convenient, thereby facilitating the maintenance of the current transformer.

[0045] The support base 5 is made of phenolic resin material. By providing the support base 5 made of phenolic resin material, the support base 5 is insulated, so that external leakage will be isolated by the insulating base, thereby improving the stability of the current transformer.

[0046] Both ends of the wires of the primary winding 41 and the secondary winding 42 are connected with wiring terminals 8, and the wiring terminals 8 are made of polyimide material. By arranging the wiring terminals 8 at both ends of the wires, it is convenient to connect the mutual inductor to the circuit and to use the mutual inductor.

[0047] When in use, the metal shell 1 is connected to the support base 5 by screws, and the support base 5 is fixed with bolts. After the connection is completed, the primary winding 41 terminal 8 is connected to the circuit, and the primary winding 41 is connected in series to the line. At least one primary winding 41 terminal 8 is connected to the controlled end of the air switch. The air switch adopts an electrically triggered type. The terminal 8 of the secondary winding 42 is connected to the magnetic balancing current. The terminal 8 of the secondary winding 42 is also connected to the trigger signal input end of the air switch. When the circuit is overloaded or short-circuited, the magnetic balancing current transformer actively triggers the air switch to disconnect the circuit to prevent damage to various components of the magnetic balancing current transformer.

[0048] Importantly, it should be noted that the construction and arrangement of the present application shown in a number of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible, for example, the size, scale, structure, shape and proportion of various elements, and parameter values ​​such as temperature, pressure, etc., mounting arrangements, use of materials, color, directional changes, etc., without substantially departing from the novel angles and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present utility model. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of the execution function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present utility model, other substitutions, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0049] Additionally, in order to provide a concise description of the exemplary embodiments, all features of the actual embodiments may not be described, ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those features that are not relevant to implementing the invention.

[0050] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, the development effort will be a routine task of design, fabrication, and production without undue experimentation.

[0051] It should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A magnetically balanced current transformer, comprising a transformer, wherein the transformer comprises a magnetic core, a primary winding and a secondary winding, characterized in that: Also includes an epoxy resin layer wrapping the mutual inductor; The epoxy resin layer is encapsulated with a metal shell outside; The metal shell is made of aluminum alloy, and the inner lining is provided with a soft magnetic tape layer; The inner lining of the soft magnetic tape layer is provided with a shielding layer formed by bonding a semi-conductive tape; Both ends of the wire of the primary winding pass through the epoxy resin layer and the metal shell and extend out of the metal shell, and both ends of the wire of the primary winding are covered with insulating sleeves; Both ends of the wire of the secondary winding pass through the epoxy resin layer and the metal shell and extend out of the metal shell. Both ends of the wire of the secondary winding are also covered with insulating sleeves. The insulating sleeve is arranged between the wire and the metal shell.

2. The magnetically balanced current transformer according to claim 1, characterized in that: A support base is connected to the lower side of the metal shell, and the support base is provided with a grounding terminal which is conductive with the aluminum alloy layer.

3. The magnetically balanced current transformer according to claim 2, characterized in that: The outer layer of the epoxy resin layer is a material layer of epoxy resin mixed with soft magnetic powder, which is called a soft magnetic epoxy resin mixed layer. The soft magnetic epoxy resin mixed layer is compounded on the outer side of the epoxy resin layer.

4. The magnetically balanced current transformer according to claim 3, characterized in that: The shielding layer is a copper foil material layer coated with a polyimide film and a carbon black polymer.

5. The magnetically balanced current transformer according to claim 4, characterized in that: The metal shell is also wrapped with a layer of mesh woven from nylon fibers containing stainless steel wires, which is called a shielding mesh.

6. The magnetically balanced current transformer according to claim 5, characterized in that: The metal shell is provided with a threaded hole connected to the support seat, the threaded hole is set as a blind hole that does not pass through the metal shell, at least two threaded holes are arranged, and at least one threaded hole is set on the front and rear surfaces of the metal shell.

7. The magnetically balanced current transformer according to claim 6, characterized in that: The support seat is provided with through holes, the number of the through holes is consistent with the threaded holes and the positions are one-to-one corresponding, the threaded holes are provided with screws in threaded cooperation, and the screws pass through the through holes and cooperate with the threaded holes to fix the support seat and the metal shell.

8. The magnetically balanced current transformer according to claim 7, characterized in that: The support seat is made of phenolic resin material.

9. The magnetically balanced current transformer according to claim 1, characterized in that: Both ends of the wires of the primary winding and the secondary winding are connected with wiring terminals, and the wiring terminals are made of polyimide material.

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