Split Rogowski coil and current transformer

Abstract

The present invention provides an open-and-closed Rogowski coil and a current transformer, wherein the open-and-closed Rogowski coil comprises a coil frame, which is annular and comprises at least one air gap opening, and a coil, which is a spirally wound coil arranged around the coil frame, wherein the density of the coil adjacent to the air gap opening is greater than the density of the coil away from the air gap opening, and the number of turns is adjusted according to the structure of the open-and-closed Rogowski coil, and the coil adjacent to the air gap opening is increased in turns, so that the density of the coil adjacent to the air gap is greater than the density of the coil away from the air gap, thereby compensating for the lost magnetic flux, thereby improving the accuracy of the open-and-closed Rogowski coil in measuring current.

Description

Technical Field

[0001] The invention belongs to the technical field of current transformers, and in particular relates to a split-type Rogowski coil and a current transformer. Background Art

[0002] At present, there are two main ways to measure the current on the industrial frequency circuit: CT and Rogowski coil. Among them, CT coils often use silicon steel as the magnetic conductive material. CT using silicon steel materials often has the problems of complicated structure, heavy weight, low self-resonance frequency, and easy saturation under large current. Rogowski coils have the advantages of simple structure, light weight, and not easy to saturate under large current. To facilitate the installation of equipment, the Rogowski coils of some equipment use an open-and-closed structure, which can be more conveniently installed in different application scenarios. However, the Rogowski coils using an open-and-closed structure will inevitably have gaps after installation. The introduction of gaps will affect the accuracy of the Rogowski coil in measuring current. Summary of the invention

[0003] In view of this, an embodiment of the present invention provides a split-type Rogowski coil, aiming to improve the accuracy of current measurement by the split-type Rogowski coil.

[0004] A first aspect of an embodiment of the present invention provides a split-type Rogowski coil, the split-type Rogowski coil comprising:

[0005] A coil frame, the coil frame is annular and includes at least one air gap opening;

[0006] The coil is a spirally wound coil arranged around the coil frame, and the coil density near the air gap opening is greater than the coil density far from the air gap opening.

[0007] In one embodiment, the coil is wound in a stacked manner near the air gap opening and is wound in a single turn away from the air gap opening.

[0008] In one embodiment, the coil skeleton includes an air gap opening, and the coil includes a first sub-coil, a second sub-coil, and a third sub-coil connected in series in sequence, the first sub-coil and the third sub-coil are adjacent to the air gap opening, and the second sub-coil is far away from the air gap opening, and the coil density of the first sub-coil and the coil density of the third sub-coil are both greater than the coil density of the second sub-coil.

[0009] In one embodiment, with any boundary position of the air gap opening as the 0° position, the winding angle of the stacked winding ranges from -40° to 0° and from 0° to +40°.

[0010] In one embodiment, the coil skeleton includes a first PCB substrate and a second PCB substrate, wherein the first PCB substrate and the second PCB substrate are both semi-annular and symmetrically arranged to form a first air gap opening and a second air gap opening, a total of two air gap openings;

[0011] The coil comprises a first sub-coil, a second sub-coil and a third sub-coil connected in series in sequence, and a fourth sub-coil, a fifth sub-coil and a sixth sub-coil connected in series in sequence;

[0012] The first sub-coil is arranged around the first PCB substrate and is adjacent to the first air gap opening, the third sub-coil is arranged around the first PCB substrate and is adjacent to the second air gap opening, the second sub-coil is arranged around the first PCB substrate and is away from the first air gap opening and the second air gap opening, and the coil density of the first sub-coil and the coil density of the third sub-coil are both greater than the coil density of the second sub-coil;

[0013] The fourth sub-coil is arranged around the second PCB substrate and is adjacent to the second air gap opening, the sixth sub-coil is arranged around the second PCB substrate and is adjacent to the first air gap opening, the fifth sub-coil is arranged around the second PCB substrate and is away from the first air gap opening and the second air gap opening, and the coil density of the fourth sub-coil and the coil density of the sixth sub-coil are both greater than the coil density of the fifth sub-coil.

[0014] In one embodiment, taking any boundary position of the first air gap opening as the 0° position, the winding angles of the stacked winding range from -15° to 0°, 0° to 15°, 165° to 180° and 180° to 195° respectively.

[0015] A second aspect of an embodiment of the present invention provides a split-type Rogowski coil, the split-type Rogowski coil comprising:

[0016] A coil frame, wherein the coil frame is annular and includes m air gap openings;

[0017] The coil is a spiral coil uniformly wound around the coil frame, the density of the coil at n positions of the coil frame is 0, forming corresponding n air gaps; wherein m+n is a multiple of 4, and the m air gap openings and the n air gaps are uniformly distributed on the circumference of the coil frame.

[0018] In one embodiment, the coil frame includes an air gap opening, the density of the coil at three positions of the coil frame is 0, forming three corresponding air gaps, and the one air gap opening and the three air gaps are evenly distributed on the circumference of the coil frame.

[0019] In one embodiment, the coil skeleton of the open-close Rogowski coil includes a first PCB substrate and a second PCB substrate, wherein the first PCB substrate and the second PCB substrate are both semi-annular and symmetrically arranged to form a first air gap opening and a second air gap opening, a total of two air gap openings;

[0020] The density of the coil at a position of the first PCB substrate is 0, and the density of the coil at a position of the second PCB substrate is 0, forming two corresponding air gaps, and the two air gap openings and the two air gaps are evenly distributed on the circumference of the coil skeleton.

[0021] A third aspect of the embodiments of the present invention provides a current transformer, which includes a lead-out terminal and the split-type Rogowski coil as described above, wherein the lead-out terminal is electrically connected to the coil.

[0022] The present invention adjusts the number of turns or the air gap according to the structure of the open-and-closed Rogowski coil. When the original structure of the coil frame has an air gap opening due to installation, the coil adjacent to the air gap opening is added with turns to make the density of the coil adjacent to the air gap greater than the density of the coil away from the air gap, thereby compensating for the lost magnetic flux, thereby improving the accuracy of the open-and-closed Rogowski coil in measuring current. Alternatively, multiple air gaps are added by another winding method, so that the multiple air gaps are evenly distributed in the annular frame. The added air gap can correct the problem of discontinuous change of the magnetic flux inside the Rogowski coil due to the air gap installed in the Rogowski coil, thereby also achieving the purpose of improving the accuracy of the open-and-closed Rogowski coil in measuring current. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 A schematic diagram of a first structure of an open-close Rogowski coil provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a second structure of an open-close Rogowski coil provided in an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a third structure of an open-close Rogowski coil provided in an embodiment of the present invention;

[0027] Figure 4 A fourth structural schematic diagram of an open-close Rogowski coil provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are embodiments of a part of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0029] The term "comprising" and any variations thereof in the specification and claims of the present invention and the above drawings are intended to cover non-exclusive inclusions. For example, a process, method or system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products or devices.

[0030] A first aspect of an embodiment of the present invention provides a split-type Rogowski coil.

[0031] like Figure 1 and Figure 2 As shown, the split Rogowski coil comprises:

[0032] A coil frame (not shown), the coil frame is annular and includes at least one air gap opening;

[0033] The coil is a spirally wound coil arranged around a coil frame, and the density of the coil near the air gap opening is greater than the density of the coil far from the air gap opening.

[0034] In this embodiment, the coil skeleton is a non-ferromagnetic material with the characteristics of light weight and strong anti-interference ability. The working principle of the Rogowski coil is that the coil skeleton surrounds the conductor to be measured, and the magnetic field around the conductor will change with the change of the current in the conductor, and the coil on the skeleton will induce an electromotive force. According to mathematical derivation, the electromotive force is proportional to the derivative of the current in the conductor, and the proportionality coefficient is related to the number of coil turns, the skeleton cross-section, the magnetic permeability, etc. In order to facilitate installation, the Rogowski coil is usually provided with an air gap opening for easy installation. The opening does not surround the coil, thereby forming an air gap, such as Figure 1 As shown, the coil frame is provided with an air gap 11, and the coils are wound around the coil frame in sequence, or as shown in FIG. Figure 2As shown, the coil skeleton is configured to be a first PCB substrate and a second PCB substrate that are symmetrically arranged, and two air gap openings 11 and 12 are formed between the two substrates. The increase in the air gap opening leads to magnetic flux loss and uneven current in the measurement process, resulting in a decrease in current detection accuracy. Therefore, in this embodiment, the number of coil turns is changed according to the structure of the coil skeleton to achieve the purpose of improving current detection accuracy.

[0035] like Figure 1 and Figure 2 As shown, the coil frame is provided with an air gap opening due to different installation methods. At this time, the number of coil turns is increased on the coil frame near the air gap opening, thereby increasing the coil density. The increased number of turns, the winding method and the winding arc length are set accordingly according to the measurement accuracy requirements. After the coil density is increased, the magnetic flux at the air gap increases, thereby compensating for the magnetic flux lost by the original air gap, thereby improving the accuracy of the open and close Rogowski coil in measuring current.

[0036] The present invention adjusts the number of turns or the air gap according to the structure of the open-and-closed Rogowski coil. When the air gap is opened due to installation of the original structure of the coil frame, the coil near the air gap opening is added with turns to make the density of the coil near the air gap greater than the density of the coil far from the air gap, thereby compensating for the lost magnetic flux, thereby improving the accuracy of the open-and-closed Rogowski coil in measuring current.

[0037] like Figure 1 and Figure 2 As shown, in one embodiment, the coil is stacked and wound near the air gap opening, and is wound in a single turn away from the air gap opening, so that the coil density near the air gap is greater than the coil density away from the air gap. For example, the two ends of the air gap are wound in a stacked manner to make up for the coils, with 4 turns on each side and 8 turns in total. After increasing the coil density, the magnetic flux at the air gap increases, thereby compensating for the magnetic flux lost by the original air gap, thereby improving the accuracy of the open and close Rogowski coil in measuring current.

[0038] like Figure 1As shown, in one embodiment, the coil skeleton includes an air gap opening 11, and the coil includes a first sub-coil 21, a second sub-coil 22 and a third sub-coil 23 connected in series in sequence. The third sub-coil 23 is close to the air gap opening 11, and the second sub-coil 22 is far away from the air gap opening 11. The coil density of the first sub-coil 21 and the coil density of the third sub-coil 23 are both greater than the coil density of the second sub-coil 21. In this embodiment, the coil skeleton is in a non-closed state due to the existence of the air gap opening, and the coil is correspondingly wound on the coil skeleton. The magnetic flux at the air gap opening 11 is reduced, and the first sub-coil 21, the second sub-coil 22 and the third sub-coil 23 are connected in series. At this time, the first sub-coil 21 and the second sub-coil 22 are set to add turns, and the first sub-coil 21 and the third sub-coil 23 are supplemented by lamination. The number of supplemented turns is not limited and is set according to the measurement accuracy requirements and the volume of the open and close Rogowski coil. For example, each coil is supplemented with 4 turns, and the total number of supplemented turns is 8 turns. After the coil density is increased, the magnetic flux at the air gap opening 11 increases, thereby compensating for the magnetic flux lost by the original air gap, thereby improving the accuracy of the open and close Rogowski coil in measuring current.

[0039] At the same time, the arc length range of the added circle can be set according to the needs, and the length of the arc can be set according to the formula:

[0040]

[0041] Determine, wherein θ is the winding angle formed by the geometric center of the coil skeleton as the center, the air gap position and the critical position of the coil wound in layers adjacent to the air gap, and R is the radius of the open and closed Rogowski coil. The winding angle can be selected accordingly through the mapping relationship between the measurement accuracy designed in the early stage and the winding angle, and then the arc length of the winding is determined. In one embodiment, any boundary position of the air gap opening 11 is taken as the 0° position, and the winding angle of the layered winding ranges from -40° to 0° and 0° to +40°.

[0042] like Figure 2 As shown, in one embodiment, the coil skeleton includes a first PCB substrate (not shown) and a second PCB substrate (not shown), the first PCB substrate and the second PCB substrate are both semi-annular and symmetrically arranged to form a first air gap opening 11 and a second air gap opening 12, a total of two air gap openings;

[0043] The coil includes a first sub-coil 21, a second sub-coil 22 and a third sub-coil 23 connected in series in sequence, and a fourth sub-coil 24, a fifth sub-coil 25 and a sixth sub-coil 26 connected in series in sequence;

[0044] The first sub-coil 21 is disposed around the first PCB substrate and is adjacent to the first air gap opening 11, the third sub-coil 23 is disposed around the first PCB substrate and is adjacent to the second air gap opening 12, the second sub-coil 23 is disposed around the first PCB substrate and is away from the first air gap opening 11 and the second air gap opening 12, and the coil density of the first sub-coil 21 and the coil density of the third sub-coil 23 are both greater than the coil density of the second sub-coil 22;

[0045] The fourth sub-coil is arranged around the second PCB substrate and is adjacent to the second air gap opening 12, the sixth sub-coil 26 is arranged around the second PCB substrate and is adjacent to the first air gap opening 11, the fifth sub-coil 25 is arranged around the second PCB substrate and is away from the first air gap opening 11 and the second air gap opening 12, and the coil density of the fourth sub-coil 24 and the coil density of the sixth sub-coil 26 are both greater than the coil density of the fifth sub-coil 25.

[0046] In this embodiment, by symmetrically arranging the two PCB substrates, when installing the open and close Rogowski coil, it is only necessary to dock and fix the two PCB substrates, and they can be directly sleeved on the installed wires without reinstalling the wires. The coils can be arranged before or after installation, and the number of turns of the first sub-coil 21, the third sub-coil 23, the fourth sub-coil 24 and the sixth sub-coil 26 are adjusted accordingly according to the size of the air gap opening generated when the two PCB substrates are installed, wherein the first sub-coil 21, the third sub-coil 23, the fourth sub-coil 24 and the sixth sub-coil 26 are stacked and wound, and the number of turns is equal, and the winding angles of each coil are respectively -15° to 0°, 0° to 15°, 165° to 180° and 180° to 195°.

[0047] A second aspect of the embodiments of the present invention provides an open-close Rogowski coil.

[0048] like Figure 3 and Figure 4 As shown, in this embodiment, the magnetic flux is adjusted by adding a symmetrical air gap to ensure that the magnetic flux and the sampling current change evenly, wherein the open-close Rogowski coil includes:

[0049] A coil frame (not shown), the coil frame is annular and includes m air gap openings;

[0050] The coil is a spiral coil uniformly wound around the coil frame, and the density of the coil at n positions of the coil frame is 0, forming corresponding n air gaps; wherein m+n is a multiple of 4, and the m air gap openings and the n air gaps are uniformly distributed on the circumference of the coil frame.

[0051] In this embodiment, different coil winding methods are selected according to the structure of the coil skeleton to increase the air gap, so that the increased air gap and the coil skeleton are evenly distributed on the circumference of the coil skeleton, thereby ensuring that the magnetic flux and the induced current of the open and close Rogowski coil change evenly, thereby improving the detection accuracy. For example, when the coil skeleton is provided with an air gap opening 11, the coil forms a plurality of air gaps on the coil skeleton by means of jumper connection, and the coil is directly connected to the unwound coil at the air gap, so that 3, 7, 11, 15 and other air gaps can be added, ensuring that the sum of the increased air gap and the air gap opening of the coil skeleton is a multiple of 4, thereby forming a plurality of air gaps that are evenly and symmetrically distributed, and the formed air gap is equal to the air gap opening size of the coil skeleton, and the more air gaps are added, the more accurate the measurement accuracy is.

[0052] The present invention adjusts the air gap according to the structure of the open-and-closed Rogowski coil, wherein, when the air gap of the original structure of the coil skeleton is opened due to installation, multiple air gaps are additionally added by winding, so that the multiple air gaps are evenly distributed in the annular skeleton. The added air gap can correct the problem of discontinuous change of the internal magnetic flux of the Rogowski coil due to the air gap of the Rogowski coil installation, and also achieve the purpose of improving the accuracy of current measurement of the open-and-closed Rogowski coil.

[0053] like Figure 1 As shown, in one embodiment, the coil frame includes an air gap opening 11, and the density of the coil at three positions of the coil frame is 0, forming corresponding three air gaps 31, 32 and 33, and one air gap opening 11 and three air gaps 31, 32 and 33 are evenly distributed on the circumference of the coil frame.

[0054] In this embodiment, the original structure of the coil skeleton is an air gap opening 11. In order to reduce the complexity of wiring and winding costs, three air gaps 31, 32 and 33 are formed on the coil skeleton by jumper wires. Adjacent coils are directly connected by wires 41, 42 and 43, and the formed air gaps 31, 32 and 33 are equal in size to the air gap opening 11 of the coil skeleton. The three air gaps 31, 32 and 33 are respectively angularly different from the air gap opening 11 of the coil skeleton by 90°, 180° and 270°, and the coil density between each air gap and the air gap opening 11 is equal.

[0055] like Figure 2 As shown, in one embodiment, the coil skeleton includes a first PCB substrate and a second PCB substrate, the first PCB substrate and the second PCB substrate are both semi-annular and symmetrically arranged to form a first air gap opening 11 and a second air gap opening 12, a total of two air gap openings;

[0056] The density of the coil at one position of the first PCB substrate is 0, and the density of the coil at one position of the second PCB substrate is 0, forming two corresponding air gaps 31 and 32. The two air gap openings 11 and 12 and the two air gaps 31, 32 and 33 are evenly distributed on the circumference of the coil skeleton.

[0057] In this embodiment, two PCB substrates are symmetrically installed to form two air gap openings 11 and 12. In order to reduce the complexity of wiring and the cost of winding, two air gaps 31 and 32 are formed on the coil skeleton by means of jumpers, that is, one air gap 31 is formed on the first PCB substrate, and another air gap 32 is formed on the second PCB substrate. Adjacent coils on the first PCB substrate are directly connected by a wire 41, and adjacent coils on the second PCB substrate are directly connected by a wire 42. The formed air gaps 31 and 32 are equal in size to the air gap openings 11 and 12 of the coil skeleton. The two air gaps 31 and 32 correspond to the two air gap openings 11 and 12 of the coil skeleton respectively at an angle difference of 90°, and the coil density between each air gap and the air gap openings is equal.

[0058] The embodiment of the present invention also provides a current transformer, which includes a lead-out terminal (not shown) and an open-and-closed Rogowski coil. The specific structure of the open-and-closed Rogowski coil refers to the above embodiment. Since the current transformer adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here. Among them, the lead-out terminal is electrically connected to the coil, and the lead terminal feeds back the current induced by the open-and-closed Rogowski coil to the control system, so that the current value of the conductor to be detected can be obtained.

[0059] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. An open and closed Rogowski coil, It is characterized in that include: A coil frame, wherein the coil frame is annular and includes m air gap openings; A coil, wherein the coil is a spiral coil uniformly wound around the coil frame, the density of the coil at n positions of the coil frame is 0, and corresponding n air gaps are formed; wherein m+n is a multiple of 4, and the m air gap openings and the n air gaps are uniformly distributed on the circumference of the coil frame; The coil frame includes an air gap opening, the density of the coil at three positions of the coil frame is 0, forming three corresponding air gaps, and the one air gap opening and the three air gaps are evenly distributed on the circumference of the coil frame; Alternatively, the coil skeleton comprises a first PCB substrate and a second PCB substrate, wherein the first PCB substrate and the second PCB substrate are both semi-annular and symmetrically arranged to form a first air gap opening and a second air gap opening, a total of two air gap openings; The density of the coil at one position of the first PCB substrate is 0, and the density of the coil at one position of the second PCB substrate is 0, forming two corresponding air gaps, and the two air gap openings and the two air gaps are evenly distributed on the circumference of the coil skeleton; Wherein, the coil forms the air gap on the coil frame by means of jumper wires.

2. A current transformer, It is characterized in that It comprises a lead-out terminal and the split-type Rogowski coil as claimed in claim 1, wherein the lead-out terminal is electrically connected to the coil.

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