CURRENT TRANSFORMER

Abstract

A current transformer includes a closed magnetic circuit and a secondary winding. A first part of the closed magnetic circuit completely surrounds a primary conductor, and a second part of the closed magnetic circuit forms the secondary winding. The second part of the closed magnetic circuit serves as a magnetic core of the secondary winding. The closed magnetic circuit forms a plurality of branch magnetic circuits at the second part, and a secondary winding is formed on each branch magnetic circuit. Each branch magnetic circuit serves as a magnetic core of a corresponding secondary winding. Each secondary winding is staggered with each other in at least one of the length, the height and the thickness.

Claims

1. A current transformer comprising: a closed magnetic circuit, a first part of the closed magnetic circuit completely surrounding a primary conductor; a second part of the closed magnetic circuit forming a secondary winding, the second part of the closed magnetic circuit serving as a magnetic core of the secondary winding; wherein, the closed magnetic circuit forms a plurality of branch magnetic circuits at the second part, and a secondary winding is formed on each branch magnetic circuit, each branch magnetic circuit serves as a magnetic core of a corresponding secondary winding, each secondary winding is staggered with each other in at least one of the length, the height and the thickness.

2. The current transformer according to claim 1, wherein the branch magnetic circuits formed by the second part of the closed magnetic circuit are mutually staggered in the length and the height, each branch magnetic circuit forms a closed magnetic circuit with the first part, wherein one branch magnetic circuit and the first part forms a closed primary magnetic circuit, and the rest branch magnetic circuits and the first part form closed auxiliary magnetic circuits.

3. The current transformer according to claim 2, wherein a total height of each branch magnetic circuit of the second part of the closed magnetic circuit in the height is equal to a height of the first part of the closed magnetic circuit.

4. The current transformer according to claim 2, wherein each secondary winding comprises: an insulation framework, the insulation framework being hollow to form a cavity, one branch magnetic circuit passing through the cavity to form a magnetic core of the secondary winding; a wire wound on the insulating framework, the wire being wrapped by an insulating layer, a wire of each secondary winding leading out two leads extending outside of the insulating layer; sheet-shaped structures being formed on both ends of the insulating framework, and the sheet-shaped structure isolating the magnetic circuit and the wire.

5. The current transformer according to claim 4, wherein the insulating frameworks of the secondary windings have different lengths, the sheet-shaped structures at the two ends of each insulation framework are mutually staggered in thickness.

6. The current transformer according to claim 5, wherein the closed magnetic circuit is formed with soft magnetic metal sheets, a first part of the closed magnetic circuit is arc-shaped and surrounds a circular primary conductor; or a first part of the closed magnetic circuit is square and surrounds a square-shaped primary conductor.

7. The current transformer according to claim 4, wherein the plurality of secondary windings are connected in series by respective leads.

8. The current transformer according to claim 4, wherein the plurality of secondary windings are connected in parallel by respective leads.

9. The current transformer according to claim 4, wherein the plurality of secondary windings have different sizes and different numbers of turns.

10. The current transformer according to claim 4, wherein the plurality of secondary windings have a same size and a same number of turns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other features, natures, and advantages of the invention will be apparent by the following description of the embodiments incorporating the drawings, wherein,

[0026] FIG. 1 illustrates a structural diagram of a current transformer according to prior art.

[0027] FIG. 2 illustrates a structural diagram of a secondary winding of a current transformer.

[0028] FIG. 3 illustrates a structural diagram of a current transformer according to an embodiment of the present invention.

[0029] FIG. 4 illustrates a structural diagram of a current transformer and a transformer housing according to an embodiment of the present invention.

[0030] FIG. 5 illustrates a structural diagram of a current transformer according to another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0031] The energy outputted by a current transformer is dependent on the number of turns of a coil included in the current transformer and the diameter of the coil. Under a same primary current, the more the number of turns of the coil is, and the larger the diameter of the coil is, the larger the energy outputted by the current transformer is. A typical method for increasing the number of turns and the diameter of the coil is enlarging a volume of the secondary winding. If a size of an insulation framework of the secondary winding is enlarged, more turns of wires can be wound on the insulation framework, which may increase the number of turns of the coil and the diameter of the coil. However, when the size of the insulation framework increases, an overall volume of the current transformer will increase and a volume of a circuit breaker increases accordingly.

[0032] Continue with FIG. 1, three directions are defined in FIG. 1 and represented by X, Y and Z respectively. The X, Y and Z directions are perpendicular to each other. The X direction indicates a thickness direction, the Y direction indicates a length direction, and the Z direction indicates a height direction. The size of the current transformer is mainly dependent on a size of the primary conductor and a length of the insulating framework in the X direction, mainly dependent on a length of the closed magnetic circuit on the Y direction and mainly dependent on a height of the closed magnetic circuit and a size of the sheet-shaped structure at both ends of the insulated framework on the Z direction. Therefore, if it is desirable to increase the number of turns and the diameter of the coil, the length of the insulating framework needs to be increased, and the insulating framework is made to have a larger diameter. The increase of the diameter of the insulating framework also increases the diameter of the sheet-shaped structure. Thus, the size of the current transformer in both the X direction and the Z direction increases. The increase in size of the current transformer does not meet the development trend of a modern circuit breaker. Modem circuit breakers are required to be miniaturized so that the design scheme with increased volume cannot be accepted.

[0033] Increase of the number of turns of the coil can also be realized by increasing the number of secondary windings. The purpose of increasing the number of turns of the coil can be achieved by arranging a plurality of secondary windings. When the number of turns of the coil is increased, it is not necessary to further considering the change of the diameter of the coil. Increase of the number of turns of the coil can obviously improve the output energy of the current transformer under a same primary current. As shown in FIG. 1, in an existing current transformer, there is a space 106 between the primary conductor 107 and the secondary winding 113, the space 106 is not utilized and is idle.

[0034] The present invention uses the space 106 described above to arrange a plurality of secondary windings. The closed magnetic circuit is made of stacked or wound soft magnetic metal sheets, and the soft magnetic metal sheets can be flexibly split or bent according to actual requirements. Such modifications are all within an original external contour space of the current transformer. All modifications utilize internal idle spaces and do not change a size of the current transformer.

[0035] FIG. 3 illustrates a structural diagram of a current transformer according to an embodiment of the present invention. As shown in FIG. 3, the current transformer comprises a closed magnetic circuit 301 and a plurality of secondary windings 303.

[0036] A first part of the closed magnetic circuit 301 completely surrounds a primary conductor 308. The first part is the upper part shown in FIG. 3. A second part of the closed magnetic circuit 301 forms a secondary winding. The second part of the closed magnetic circuit serves as a magnetic core of the secondary winding. The second part is the lower part shown in FIG. 3.

[0037] The closed magnetic circuit 301 forms a plurality of branch magnetic circuits 304, 305 at the second part. One secondary winding 303 is formed on each branch magnetic circuit. Each branch magnetic circuit serves as a magnetic core of a corresponding secondary winding. Each secondary winding 303 is staggered with each other in at least one of the length, the height and the thickness.

[0038] Each branch magnetic circuit is formed by splitting of laminated or wound soft magnetic metal sheets. Generally, the respective branch magnetic circuits are bent at different positions in Y direction, so that the branch magnetic circuits are staggered in Y direction (i.e., the length direction). Meanwhile, the respective branch magnetic circuits are formed by different layers of soft magnetic metal sheets and they are naturally staggered in Z direction (i.e., the height direction). Because the branch magnetic circuits are formed by splitting of laminated or wound soft magnetic metal sheets, a total height of each branch magnetic circuit in the height direction is equal to a height of the first part of the closed magnetic circuit.

[0039] Each secondary winding 303 has a structure similar to that shown in FIG. 2, comprising: an insulation framework 204, a wire 205, an insulating layer 201, leads 206 and sheet-shaped structures 202. The insulation framework 204 is hollow to form a cavity 203. One branch magnetic circuit passes through the cavity 203 to form a magnetic core of the secondary winding. The wire 205 winds on the insulating framework 204, the wire 205 is wrapped by the insulating layer 201. The wire 205 of each secondary winding leads out two leads 206 extending outside of the insulating layer. The leads 206 are denoted as leads 307 in FIG. 3. The sheet-shaped structures 202 are formed on both ends of the insulating framework 204, and the sheet-shaped structure 202 isolates the magnetic circuit and the wire.

[0040] In each secondary winding 303, the most outwardly protruding portion of an outer contour is the sheet-shaped structure 202. In order to avoid mutual interference between the secondary windings 303, it is also necessary to consider the position between the sheet-shaped structures 202. In some embodiments, by arranging the respective branch magnetic circuits in a staggered manner in Y direction and Z direction, the sheet-shaped structures 202 at both ends of the insulating framework 204 of respective secondary windings 303 do not interfere with each other. In other embodiments, if a size of the sheet-shaped structure 202 is large, only a staggered arrangement of the respective branch magnetic circuits in Y direction and Z direction is not sufficient to separate the sheet-shaped structures 202 of respective secondary windings 303 from each other. At this time, a further adjustment may be achieved in X direction (the thickness direction). For example, the insulating framework 204 of respective secondary windings may have different lengths. Thus, the sheet-shaped structures 202 at both ends of respective insulating frameworks are further staggered in the thickness direction and will not interfere with each other.

[0041] The plurality of secondary windings in the current transformer of the present invention are staggered in at least on direction of length, height and thickness (the X direction, Y direction or Z direction), so that the plurality of secondary windings can be placed in the current transformer without influence each other. Here, a staggered manner of respective secondary windings in at least one direction of lengths, height or thickness (the X direction, Y direction or Z direction) includes staggering in on direction, staggering in two directions or staggering in all three directions.

[0042] Continue with FIG. 3, each of the plurality of branch magnetic circuits 304, 305 formed by the second part of the closed magnetic circuit 301 forms a closed magnetic circuit with the first part. One branch magnetic circuit and the first part forms a closed primary magnetic circuit, and the rest branch magnetic circuits and the first part form closed auxiliary magnetic circuits. According to the embodiment shown in FIG. 3, the branch magnetic circuit 305 is the primary magnetic circuit and the branch magnetic circuit 304 is the auxiliary magnetic circuit. Generally, the primary magnetic circuit 305 has more soft magnetic metal sheets that the auxiliary magnetic circuit 304, thus the primary magnetic circuit 305 looks thicker than the auxiliary magnetic circuit 304. The positions of the primary magnetic circuit and the auxiliary magnetic circuit are not limited. The primary magnetic circuit may be arranged on the outer side (away from the primary conductor), and the auxiliary magnetic circuit may be arranged on the inner side (between the primary conductor and the primary magnetic circuit). Or the primary magnetic circuit may be arranged on the inner side and between the primary conductor and the auxiliary magnetic circuit. Or a part of the auxiliary magnetic circuit may be arranged on the inner side of the primary magnetic circuit and the other part of the auxiliary magnetic circuit may be arranged on the outer side of the primary magnetic circuit.

[0043] According to the embodiment shown in FIG. 3, the stacked or wound soft magnetic metal sheets are connected together by a riveting element 302. The riveting element 302 may be provided in the first part of the closed magnetic circuit so as to fix all of the soft magnetic metal sheets. Or the riveting element 302 may provided in the second part of the closed magnetic circuit so as to fix the soft magnetic metal sheets in a particular branch magnetic circuit.

[0044] Each secondary winding 303 has a respective lead 307, and each secondary winding 303 leads out two leads 307. The respective secondary windings 303 in the current transformer may be connected in parallel, or be connected in series. The parallel or series connection of the secondary windings is achieved through respective leads. Finally, two leads are led out from the current transformer to serve as the leads of the current transformer.

[0045] The respective secondary windings 303 may have different sizes and different numbers of turns. For example, the respective secondary windings may have different diameters and lengths according to actual space of placement. Different diameters and lengths result differences in size and number of turns. Or, if the space of placement is sufficient, the respective secondary windings may have a same size and a same number of turns.

[0046] FIG. 4 illustrates a structural diagram of a current transformer and a transformer housing according to an embodiment of the present invention. The current transformer is placed in a housing 401. According to the present invention, the additional secondary windings in the current transformer utilize idle spaces within the current transformer, thus a size of the outer contour of the current transformer does not increase, the volume does not change as well. Therefore, it is not necessary to change the size of the housing 401.

[0047] According to the embodiment shown in FIG. 3, the first part of the closed magnetic circuit 301 is arc-shaped and surrounds a circular primary conductor 308.

[0048] FIG. 5 illustrates a structural diagram of a current transformer according to another embodiment of the present invention. Compared with the embodiment shown in FIG. 3, the embodiment shown in FIG. 5 differs in that the first part of the closed magnetic circuit 501 is square and surrounds a square-shaped primary conductor 508. Other structures of this embodiment are similar to that of the embodiment shown in FIG. 3.

[0049] The current transformer of the present invention fully utilizes the idle space therein. A plurality of secondary windings are arranged in a spatial interleaving manner and a plurality of secondary windings are arranged in a spatial interleaving manner, the plurality of secondary windings significantly increase a total energy outputted by the circuit transformer. Larger output energy is obtained under a same volume, and a performance of the circuit breaker under a small current condition can be improved.

[0050] The above embodiments are provided to those skilled in the art to realize or use the invention, under the condition that various modifications or changes being made by those skilled in the art without departing the spirit and principle of the invention, the above embodiments may be modified and changed variously, therefore the protection scope of the invention is not limited by the above embodiments, rather, it should conform to the maximum scope of the innovative features mentioned in the Claims.