A small current transformer

Abstract

The utility model discloses a small current transformer, its technical scheme main points include the first core magnetic circuit and the second core magnetic circuit of mutual independence, the first core magnetic circuit includes the first part of encircling primary conductor and is provided with the second part of secondary winding, the second part forms a plurality of branch magnetic circuit, and each branch magnetic circuit constitutes closed magnetic circuit with the first part, a plurality of branch magnetic circuit total height in height direction is equal to the height of first part, the second core magnetic circuit has the open shape, and is coupled to the first core magnetic circuit through at least one air gap. The utility model discloses through the setting of branch magnetic circuit, can install a plurality of secondary windings, under the condition that the current transformer does not increase the size in thickness direction, significantly increases total turns, so that when the primary current is small, can export enough energy of driving subsequent circuit.

Description

Technical Field

[0001] This utility model relates to the field of current transformer technology, and more specifically to a small current transformer. Background Technology

[0002] Currently, in power distribution systems, circuit breakers have the functions of connecting, disconnecting, or carrying rated operating current, and can also protect against fault currents such as short-circuit current and overload current. When a short circuit occurs, the circuit breaker can automatically disconnect the circuit without an external power supply, thus achieving reliable protection. The disconnecting device in the circuit breaker is used to perform the disconnecting action, while the current transformer supplies power to the disconnecting device. The energy of the current transformer comes from the current flowing through the primary conductor of the circuit breaker (i.e., the primary current).

[0003] However, there are still some defects in the existing technologies. In order to meet the requirements of miniaturization, the magnetic circuit volume and the number of turns of the secondary winding of the existing small current transformers are limited, which makes the energy of the induced output too low when the primary current is small, making it difficult to drive the subsequent circuit; and when encountering a large current, it is very easy to overload and burn out due to its limited carrying capacity. Utility Model Content

[0004] In view of the shortcomings of the existing technology, the present invention provides a small current transformer.

[0005] To achieve the above objectives, the present invention provides the following technical solution: comprising a first core magnetic circuit and a second core magnetic circuit that are independent of each other. The first core magnetic circuit includes a first part surrounding a primary conductor and a second part having a secondary winding. The second part forms a plurality of branch magnetic circuits, each branch magnetic circuit forming a closed magnetic circuit with the first part. The total height of the plurality of branch magnetic circuits in the height direction is equal to the height of the first part. The second core magnetic circuit has an open shape and is coupled to the first core magnetic circuit through at least one air gap.

[0006] The present invention is further configured such that: the branch magnetic circuit includes a main magnetic circuit and at least one auxiliary magnetic circuit, each branch magnetic circuit is provided with a secondary winding, and the multiple secondary windings are staggered from each other in at least one of the length direction, height direction and thickness direction.

[0007] The present invention is further configured such that the auxiliary magnetic circuit is symmetrically distributed with the central symmetry plane of the main magnetic circuit as the symmetry plane.

[0008] The present invention is further configured such that the second iron core magnetic circuit and the first iron core magnetic circuit are arranged in the same plane.

[0009] The present invention is further configured such that the air gap is a fixed air gap of equal thickness and is filled with a solid non-ferromagnetic material.

[0010] The present invention is further configured such that: the second part of the first iron core magnetic circuit includes a linear iron core, and the cross-sectional area of ​​the linear iron core is smaller than the cross-sectional area of ​​the first part of the first iron core magnetic circuit.

[0011] In summary, this utility model has the following beneficial effects: 1. By setting up branch magnetic circuits, multiple secondary windings can be installed, significantly increasing the total number of turns without increasing the thickness of the transformer, so that when the primary current is small, it can output enough energy to drive the subsequent circuit.

[0012] 2. By setting up the second magnetic circuit and air gap, when the primary current is large, the magnetic flux shunting avoids the overheating of the iron core. At the same time, the iron core saturation effect suppresses the growth of the secondary output current, keeping it relatively stable and protecting the back-end electronic equipment. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this embodiment; Figure 2 This is a side sectional view of this embodiment; Figure 3 This is a cross-sectional view of the air gap location in this embodiment.

[0014] Reference numerals in the attached diagram: 1. First core magnetic circuit; 11. First part; 12. Second part; 121. Branch magnetic circuit; 1211. Main magnetic circuit; 1212. Auxiliary magnetic circuit; 122. Linear core; 2. Second core magnetic circuit; 21. Air gap; 3. Secondary winding; 4. Primary conductor. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings.

[0016] This embodiment discloses a small current transformer, such as Figures 1 to 3As shown, it includes a first core magnetic circuit 1 and a second core magnetic circuit 2 that are independent of each other. The first core magnetic circuit 1 includes a first part 11 surrounding the primary conductor 4 and a second part 12 provided with a secondary winding 3. The second part 12 forms a plurality of branch magnetic circuits 121. Each branch magnetic circuit 121 and the first part 11 form a closed magnetic circuit. By "splitting" the secondary winding 3 of the first core magnetic circuit 1 into a plurality of branch magnetic circuits 121, a plurality of secondary windings 3 are installed without increasing the overall magnetic circuit outline size. Each branch magnetic circuit 121 forms a complete magnetic ring with the common first part 11, ensuring that the magnetic flux generated by the primary conductor 4 is effectively coupled to each branch. The multi-branch magnetic circuit 121 allows for the installation of multiple secondary windings 3, significantly increasing the total number of coil turns, thereby outputting sufficient energy to drive subsequent circuits even with a small primary current. When the current transformer is in its normal operating position, its vertical dimension is defined as its height, while its dimension along the front-to-back direction is defined as its thickness. The total height of the multiple branch magnetic circuits 121 in the thickness direction is equal to the height of the first part 11, ensuring that the overall size of the current transformer meets the miniaturization requirements. The second iron core magnetic circuit 2 has an open shape and is coupled to the first iron core magnetic circuit 1 through at least one air gap 21. The first and second iron core magnetic circuits 2 are physically separate and not a single unit; they interact through magnetic coupling rather than electrical connection. This provides an independent path for flux shunting. The introduction of the second magnetic circuit and air gap 21 enables the secondary output current to be effectively suppressed and kept relatively stable when the primary current is large (such as overload or short-circuit current) through flux shunting and core saturation effect, thus protecting the back-end electronic equipment and avoiding core overheating.

[0017] Further improvements include a branch magnetic circuit 121 comprising a main magnetic circuit 1211 and at least one auxiliary magnetic circuit 1212. Each branch magnetic circuit 121 is equipped with one secondary winding 3, enabling the safe and reliable installation of multiple secondary windings 3 without increasing the overall volume. Furthermore, the multiple secondary windings 3 are staggered in at least one of the length, height, and thickness directions. This staggered arrangement in three-dimensional space avoids interference between the winding structures of the branch magnetic circuit 121, ensuring their physical coexistence within a limited space, effectively utilizing space, and optimizing internal space utilization.

[0018] Furthermore, the auxiliary magnetic circuits 1212 are symmetrically distributed with respect to the central symmetry plane of the main magnetic circuit 1211. This ensures that the path and magnetic reluctance characteristics are symmetrical when the magnetic flux flows from the first part 11 to each auxiliary magnetic circuit 1212, guaranteeing a relatively balanced magnetic flux distribution in each auxiliary magnetic circuit 1212. This results in consistent output characteristics and stable performance for each auxiliary winding. Simultaneously, the symmetrical structure helps to offset any additional leakage flux that may be caused by asymmetrical magnetic circuits, improving magnetic coupling efficiency.

[0019] Further improvements include arranging the second iron core magnetic circuit 2 and the first iron core magnetic circuit 1 in the same plane. The iron cores of the two magnetic circuits are assembled in the same plane. This ensures that the direction of magnetic flux does not change drastically when it crosses the air gap 21 from one magnetic circuit to another, making the flux transfer path more natural and reducing the total magnetic reluctance of the flux shunting path. Lower magnetic reluctance means that the second magnetic circuit has a stronger ability to shunt magnetic flux when needed, resulting in better voltage regulation.

[0020] Further improvements include a fixed air gap 21 of uniform thickness, ensuring consistent product performance. This air gap 21 is filled with a solid, non-ferromagnetic material, maintaining its thickness and preventing changes under vibration or thermal expansion and contraction. Furthermore, the filler material itself does not possess high magnetic permeability, thus not affecting the high magnetic reluctance characteristics of the air gap 21. Simultaneously, the filler material acts as a physical spacer, simplifying the assembly process and improving production efficiency and precision.

[0021] Further improvements include a second part 12 of the first core magnetic circuit 1 comprising a linear core 122, the cross-sectional area of ​​which is smaller than that of the first part 11 of the first core magnetic circuit 1. According to Ohm's law for magnetic circuits, with the same magnetic flux, the part with the smaller cross-sectional area has a higher magnetic flux density. When the primary current increases, the smaller cross-sectional area of ​​the linear core 122 will be the first to enter saturation. Once saturated, the permeability of this region decreases sharply, and the magnetic reluctance increases significantly, effectively suppressing further increases in the induced current in the secondary winding 3, allowing more magnetic flux to flow through the air gap 21 to the second magnetic circuit. Ultimately, the U-shaped part of the first core magnetic circuit 1 and the second magnetic circuit saturate together, achieving stable current limiting and voltage stabilization.

[0022] Working principle of this utility model When a small current flows through the primary conductor 4, the total magnetomotive force is small. All branches of the first iron core magnetic circuit 1 and the second iron core magnetic circuit 2 are far from saturated, and the magnetic reluctance is very low. Since the magnetic reluctance of the air gap 21 is much higher than that of the iron core, most of the magnetic flux is confined within the closed loop of the first iron core magnetic circuit 1. The magnetic flux starts from the first part 11 surrounding the conductor and passes through the two parallel branch magnetic circuits 121, the main magnetic circuit 1211 and the auxiliary magnetic circuit 1212. The secondary winding 3 on each branch cuts the magnetic flux and generates an induced current, so that the secondary windings 3 are connected in parallel or in series. The total output energy is much greater than the design current of a traditional single winding.

[0023] As the primary current increases, since the cross-sectional areas of the auxiliary magnetic circuit 1212 and the main magnetic circuit 1211 are smaller than the cross-sectional area of ​​the first part 11, the branch magnetic circuit 121 will enter magnetic saturation first. The winding output current will no longer increase proportionally with the primary current, but will tend to level off. The increasing magnetomotive force will overcome the high magnetic resistance of the air gap 21 and flow into the second iron core magnetic circuit 2 in large quantities, effectively diverting excess energy and preventing it from being concentrated in the first iron core, which would cause a severe temperature rise.

[0024] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the design concept of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A small current transformer, characterized in that: The system includes a first core magnetic circuit (1) and a second core magnetic circuit (2) that are independent of each other. The first core magnetic circuit (1) includes a first part (11) surrounding a primary conductor (4) and a second part (12) provided with a secondary winding (3). The second part (12) forms a plurality of branch magnetic circuits (121), each branch magnetic circuit (121) forming a closed magnetic circuit with the first part (11). The total height of the plurality of branch magnetic circuits (121) in the height direction is equal to the height of the first part (11). The second core magnetic circuit (2) has an open shape and is coupled to the first core magnetic circuit (1) through at least one air gap (21).

2. A small current transformer according to claim 1, characterized in that: The branch magnetic circuit (121) includes a main magnetic circuit (1211) and at least one auxiliary magnetic circuit (1212). Each branch magnetic circuit (121) is provided with a secondary winding (3), and the multiple secondary windings (3) are staggered from each other in at least one of the length direction, height direction and thickness direction.

3. A small current transformer according to claim 2, characterized in that: The auxiliary magnetic circuit (1212) is symmetrically distributed with the central symmetry plane of the main magnetic circuit (1211) as the symmetry plane.

4. A small current transformer according to claim 1, characterized in that: The second core magnetic circuit (2) is arranged in the same plane as the first core magnetic circuit (1).

5. A small current transformer according to claim 1, characterized in that: The air gap (21) is a fixed air gap (21) of equal thickness, and is filled with a solid non-ferromagnetic material.

6. A small current transformer according to claim 1, characterized in that: The second part (12) of the first core magnetic circuit (1) includes a linear core (122), the cross-sectional area of ​​which is smaller than that of the first part (11) of the first core magnetic circuit (1).

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