CN201465698U - A high-precision open-type Rogowski coil - Google Patents

Abstract

The utility model relates to the field of current sensors for high voltage and large current measurement, in particular to a printed circuit board Rogowski coil. The utility model discloses a high-precision open-type Rogowski coil, which comprises at least one layer of PCB boards, and each layer of PCB boards is composed of two oppositely arranged boards; a distance is provided between the two boards, and one end of the two boards is open. It is a normally open opening; the PCB board is provided with a coil, and the coil is composed of a wire engraved on the upper and lower sides of the PCB board and a wire post connected to the upper and lower wires; a signal output terminal is provided at the normally open opening; two The coils of the plates are connected in series by connecting wires. Compared with the traditional open-type Rogowski coil, the utility model has the characteristics of small size, light weight, easy installation and carrying. Moreover, the mutual interference is eliminated through measures such as uniform wiring and loop layout, and the accuracy can reach 0.05 level.

Description

A high-precision open-type Rogowski coil

technical field

The utility model relates to the field of current sensors for high voltage and large current measurement, in particular to a printed circuit board Rogowski coil.

Background technique

Traditional Rogowski coils for measuring current generally have two structures: open and closed. Open-type Rogowski coils are mostly used in occasions where conductor disassembly is inconvenient, such as live measurement of conductors. Its installation and maintenance are more convenient, but the accuracy of the open Rogowski coil is slightly lower, and due to mechanical structure and manufacturing reasons, the open Rogowski coil tends to decrease in accuracy with the increase of use time or times. At present, the open-type Rogowski coils used for live measurement are mostly rigid coils, which are made of air-core coils, and non-ferromagnetic materials are used to replace traditional iron cores. When used for measurement, an external shielding structure is added. The openings are connected by screws or other connectors.

Traditional Rogowski coils are often made by uniformly winding enameled wires on a ring-shaped frame. The frame is made of non-ferromagnetic materials such as plastic or ceramics. The relative magnetic permeability of the frame is the same as that in the air. A distinguishing feature of the core coil is that it differs from an AC current transformer with an iron core. The typical structure of the air-core coil is shown in Figure 6. The enameled wire windings on the air-core coil are evenly distributed, and the plane where each turn of the coil is located passes through the central axis of the coil; when used, the cylindrical primary conductor passes through the center of the air-core coil , their central axes coincide. In the design of the split Rogowski coil, for the consistency and accuracy of installation, the inner diameter of the split coil is selected to be the same as or close to the outer diameter of the primary conductor.

In Fig. 6, the Rogowski coil includes two skeletons 21 with opposite openings, the distance between the two skeletons 21 is an opening 24, the skeleton 21 is made of non-magnetic material, and the enameled wire 22 is evenly wound along the circumferential direction on the skeleton 21, The connecting wire 23 softly connects the enameled wires 22 respectively wound on the two skeletons 21 .

However, in order to ensure the accuracy of measurement, the open-type Rogowski coil is generally large in size and weighs about tens of kilograms, which makes it difficult to carry and install.

The measurement accuracy of the Rogowski coil depends on a stable mutual inductance constant M. In order to ensure the stability of the mutual inductance coefficient of the coil, the following principles must be followed in the design: 1. The coil density is constant; 2. The cross-sectional area of the skeleton is constant; 3. The coil cross-section is perpendicular to the center line.

In addition, considering the environment in which the air-core coil is used, the air-core coil is wound with a return winding, that is, at the outlet end of the coil, the return winding is carried out in the opposite direction of the winding direction. The winding of the loop makes the magnetic field perpendicular to the coil plane cancel on the coil winding and the induced potential on the loop, which can effectively resist the influence of external interference electromagnetic fields and effectively improve the anti-interference performance of the coil.

Utility model content

The purpose of the utility model is to provide a small and easy-to-carry open-type printed circuit board Rogowski coil, which can effectively improve the measurement accuracy.

The technical scheme of the utility model is:

A high-precision open-type Rogowski coil, which includes at least one layer of PCB boards, and each layer of PCB boards is composed of two oppositely arranged boards; a distance is provided between the two boards, and one end of the two boards is normally open; The PCB board is provided with a coil, and the coil is composed of a wire engraved on the bottom of the PCB board and a wire post connected to the upper and lower wires; a signal output terminal is provided at the normally open opening; the coils of the two boards are connected by wires connected in series.

It includes a pair of PCB boards stacked up and down. A pair of PCB boards includes two layers of PCB boards. There is an insulating pad between the PCB boards. The two layers of PCB boards are arranged in a mirror structure. The connecting wire is connected; the mirror image structure is that the upper surface of the upper PCB board is completely consistent with the lower surface of the lower PCB board, and the lower surface of the upper PCB board is completely consistent with the upper surface of the lower PCB board; the coils of two adjacent pairs of PCB boards are formed by The wires are connected in series.

It includes two or more pairs of PCB boards, each pair of PCB boards includes two layers of PCB boards, an insulating material is provided between two adjacent pairs of PCB boards, and the coils of two adjacent pairs of PCB boards are connected in series by wires.

The PCB board includes an intermediate epoxy layer, and conductor layers and insulating varnish layers are arranged symmetrically on both sides of the intermediate epoxy layer.

The board is arranged in a shielding box, and the shape of the shielding box is adapted to the board; one side of the shielding box is connected by a connecting mechanism.

The board is arranged in a shielding box, and the shape of the shielding box is adapted to the shape of the board; the shielding box is connected by a connecting mechanism.

The coil on the PCB is semi-circular.

The coil on the PCB board is semi-circular.

The coil on the PCB board is semi-circular.

The two layers of PCB boards are connected by screws.

The utility model comprises two semi-circular annular plates, a distance is set between the two semi-circular annular plates, one end opening of the two semi-circular annular plates is connected by a connecting mechanism, and the other end of the two semi-circular annular plates is a normally open opening; the semi-circular annular plates are A pair of semi-circular PCB boards, the PCB boards are provided with coils along the circumferential direction to form open-type PCB air-core coils, and the paired PCB boards are arranged in a mirror image structure; in addition, the utility model can also stack multiple pairs of PCB boards, each The PCB board includes two layers of PCB boards, and the coils on the PCB boards are connected in series through connecting wires between the boards; the utility model can also only have a pair of oppositely arranged PCB boards, and the coils of the two PCB boards are connected by flexible connecting wires. Compared with the traditional open-type Rogowski coil, the utility model has the characteristics of small size, light weight, easy installation and carrying. Moreover, the mutual interference can be eliminated through measures such as uniform wiring and loop arrangement, and the precision can reach 0.05 level. The high-precision, open-ended Rogowski coil based on PCB technology can be applied to live current measurement occasions, and its high-precision characteristics can make it meet the requirements of live comparison (calibration or verification) of current transformers; the open structure And it is easy to carry, which can reduce the difficulty of live operation for workers.

At the same time, in order to effectively eliminate the influence of the external interference magnetic field perpendicular to the coil plane, the planar air-core coil adopts the effective "loop" measure of mirror arrangement, which eliminates the potential influence of the external magnetic field to the greatest extent, which is better than the traditional approximation The offset method is more scientific and practical.

Description of drawings

Fig. 1 is the structural representation of the utility model embodiment one;

Figure 2 is a top view of a single PCB board;

Fig. 3 is the A-A sectional view of Fig. 2;

Fig. 4 is the B-B sectional view of Fig. 2;

Fig. 5 is a schematic diagram of expansion of the double-plate connection of the present invention;

Fig. 6 is a structural schematic diagram of an existing open-ended Rogowski coil;

Fig. 7 is the structural representation of embodiment two;

Fig. 8 is a C-C sectional view of Fig. 7 .

Detailed ways

Embodiment one

As shown in Figures 1 and 2, the utility model comprises an open-type aluminum shielding box 17 and two layers of PCB boards (printed circuit boards) 1, 13 up and down, stacked and placed. Each PCB board includes two semicircular annular plates 15, 16, and the semicircular annular plates 15, 16 are arranged oppositely. The shielding box 17 is divided into upper and lower parts, and the semicircular annular plates 15 and 16 are respectively located in the upper and lower parts of the shielding box 17, and the middle of the shielding box 17 is provided with a hole for a primary current-carrying conductor to pass through. The left opening (very open opening) of the shielding box 17 is provided with a connecting mechanism 18, which connects the upper and lower parts of the shielding box 17, and the upper and lower parts of the shielding box 17 can be rotated around the connecting mechanism 18 to open. The shielding box 17 is mainly used to shield external electromagnetic signals, prevent interference, and protect the inner semi-circular ring plates 15 and 16 at the same time. The connecting mechanism 18 is a rotating shaft, or other hinged devices. The opening 6 of the shielding box 17 is opened, and the primary current-carrying conductor passes through the shielding box 17. The connecting mechanism 18 can be quickly opened and closed, and the installation is accurate and firm. At the same time, in order to ensure the measurement accuracy and installation consistency of the present invention, the inner diameter r of the open-type aluminum shielding box 17 is the same as the outer diameter of the primary current-carrying conductor.

As shown in Figures 3 and 4, an insulating pad 9 (such as thin insulating paper or insulating plastic, etc.) is provided between the PCB boards 1 and 13, which can ensure that the conductors on the contact surfaces of the two boards are isolated from each other. A single PCB board consists of an insulating varnish layer 10 , a conductive layer 11 , an intermediate epoxy layer 12 , a conductive layer 11 , and an insulating varnish layer 10 from top to bottom. The upper and lower sides of the PCB board 1 are engraved with wires 2, and the wires 2 are evenly arranged on the board along the circumferential direction. Both ends of each wire 2 are provided with wire via holes 3, and the wire via holes 3 pass through the PCB board 1, and the wire posts 19 It is arranged in the wire via hole 3 and connects the upper and lower wires 2 to form a coil. The PCB board 13 located below also has the same structure.

As shown in Figure 5, the coil of each semicircular annular plate has a pair of output terminals U+ and U-, the U- of the semicircular annular plate 15 on the upper floor and the U+ of the semicircular annular plate 16 are connected by the connecting line 4, and the semicircular annular plate located on the lower floor The U+ of the annular plate 15 and the U- of the semi-circular annular plate 16 are connected by the connecting wire 4, and the U- of the semi-circular annular plate 16 on the upper floor and the U+ of the semi-circular annular plate 16 located on the lower floor are connected by the connecting line 8 between the plates, and are not connected by the connecting wire 4. The wires are connected and the remaining output terminals U+ and U- are respectively connected to the signal output lines 5 . It is equivalent to that the inter-board connecting wire 8 softly connects the coils respectively located on the PCB boards 1 and 13 .

The design of the open-type PCB air-core coil follows the design principle of the air-core coil, but due to the limited thickness of the substrate of the printed circuit board (common board thickness does not exceed 3mm), and as the thickness increases, the processing of the electrical connection via hole 3 between layers The difficulty will increase and lead to a decrease in its reliability. Therefore, PCB air-core coils are generally formed by connecting multiple PCB boards in series.

The processing of printed circuit boards is generally carried out by automatic control of machines for corrosion treatment and processing. The control precision of printed circuit board technology is high, which can effectively ensure the uniform and symmetrical distribution of multi-turn windings. Because the base material of the printed circuit board and the copper clad layer are closely combined and the temperature stability is excellent, even in the case of severe temperature changes, the shape of the coil and the distribution of the multi-turn coil are always consistent. Therefore, only after the coil design is completed, the PCB board diagram can be drawn by using the special software, and the flat coil can be automatically produced by the printed circuit board production system.

The paired PCB boards are arranged in a mirror image structure. As shown in FIG. A pair of outgoing terminals for connecting signal output lines are drawn out from the mirrored PCB board. The role of the mirror arrangement of the PCB board is similar to the function of the winding wire in the traditional coil, which can effectively resist the influence of external interference electromagnetic fields and effectively improve the anti-interference performance of the coil.

Correspondingly be provided with several (12 as shown in the figure) connection holes 14 on the circumference of PCB board 1,13, penetrate connection hole 14 with screw 7 and then connect and combine two PCB boards 1,13.

Manufacturing method is: as shown in Figure 2, select suitable diagonal on the annular coil, it is divided into two semi-annular plates 15,16. Use the connection wire 4 (soft twisted wire) to restore the electrical connection to the wire hole 3 on the side. The connection wire 4 is a soft connection wire; the opening 6 on the other side is reserved for easy installation on the primary current-carrying conductor. According to the output of the hollow coil The position of the end leads to the signal output line 5.

The principle of the utility model: In order to effectively eliminate the influence of the external interference magnetic field perpendicular to the coil plane, the flat-shaped air-core coil adopts the effective "loop" measure of mirror image arrangement, which can eliminate the potential influence of the external magnetic field to the greatest extent, compared with the traditional The approximate offset method is more scientific and practical.

The main key parameters of the air-core coil are: mutual inductance coefficient, self-inductance coefficient, internal resistance and inter-turn capacitance of the coil. In contrast, the self-inductance and mutual inductance of the air-core coil are more important in the design of the air-core coil. Since the structure of the planar air-core coil is basically the same as that of the traditional air-core coil, it can be calculated by referring to the analysis method of the traditional air-core coil.

Considering the needs of the actual application environment (carrying out live measurement without disconnecting the primary conductor), the PCB Rogowski coil chooses the clamp type (that is, "open type") structure, and the "open type" structure makes it possible to cut off the primary current-carrying wire The installation and disassembly of the current measuring device can be realized conveniently under the circumstances. The clamp-type air-core coil is composed of two semi-circular PCB boards. When in use, the semi-circular PCB boards are respectively fixed on the transformer shell. During the operation of the device, the two boards are closed to form a complete air-core coil. There is a small gap between them, which is called the opening distance. The opening distance of the clamp-type air-core coil can be regarded as the non-uniform winding of the coil, and the impact on its accuracy can be known through distribution calculations. The specific impact is shown in Table 1 below.

The experimental parameters are:

Coil size: inner opening diameter 76mm; outer maximum diameter: 190mm; coil inner diameter 104mm; coil outer diameter 174mm; single plate coil turns 200; double plate mirror connection. It is fixed outside a conductor with a diameter of 30mm for large current measurement, and the measurement current range is 300-900A.

Table 1 Error caused by coil opening (including eccentricity and adjacent phase interference)

From the above theoretical analysis and calculation of the clamp-type air-core coil, the following conclusions can be drawn:

1) The main factors that affect the measurement accuracy are: the change of the position of the primary wire, the interference of the adjacent phase current and the size of the air gap of the opening, among which the size of the air gap of the opening is the most influential.

2) For the clamp-type air-core coil under the technical conditions of this project, when the primary wire deviates from the center by ±2mm, the distance between the adjacent phase primary wires is 200mm, and the opening air gap is 0.05mm, the total error of the above-mentioned clamp-type air-core coil is: 0.0235 %; when the open air gap is 0.1mm, the total error of the above-mentioned clamp-type air-core coil is: 0.047%.

Therefore, through the fixing method of the mechanical device, the opening air gap is less than 0.1mm, and the total error of the clamp-type air-core coil can be controlled within the range of 0.03%-0.05%.

Embodiment two

The difference from Embodiment 1 is that, as shown in Figures 7 and 8, the semicircular annular plates 15 and 16 are only one layer of PCB board 1, and are no longer divided into two layers, and do not need to be connected by connecting wires 8 between boards, and the PCB board 1 Divided into two halves, respectively semi-circular annular plates 15, 16, U- of the semi-circular annular plate 15 and U+ of the semi-circular annular plate 16 are connected by connecting line 4, and the remaining U+ and U- are output ends, respectively connected to the signal output lines 5 connections.

Finally, it should be noted that the coil formed by the wire 2 on the PCB and the wire post 19 can also be in other shapes such as rectangle, ellipse, etc., and make corresponding changes according to the shape of the primary conductor to be measured. The shapes of the semi-circular plates 15 and 16 are not limited to semi-circular, and can be approximately replaced by other shapes as required. In addition, the PCB board can be two pairs or more than two pairs, each pair includes two layers of PCB boards arranged in a mirror structure, and the coils on the adjacent two pairs of PCB boards are connected in series with wires, and the remaining one U+ and a U- as the output terminal, insulating material is used between two adjacent pairs of PCB boards; the shape of the inner opening of the open aluminum shielding box 17 is adapted to that of the primary current-carrying conductor, such as when the primary current-carrying conductor is rectangular , the shape of the inner opening is correspondingly rectangular; such approximate changes all fall within the scope of protection of the present utility model.

Claims (9)

1. A high-precision open-type Rogowski coil is characterized in that: it includes at least one layer of PCB boards, and each layer of PCB boards is made up of two relatively arranged boards; spacing is provided between the two boards, and one end of the two boards The opening is a normally open opening; the PCB board is provided with a coil, and the coil is composed of a wire engraved on the upper and lower sides of the PCB board and a wire post connected to the upper and lower wires; a signal output terminal is provided at the normally open opening; The coils of the plates are connected in series by connecting wires. 2. The high-precision open-type Rogowski coil according to claim 1, characterized in that: it includes a pair of PCB boards stacked up and down, a pair of PCB boards includes two layers of PCB boards, and an insulating pad is provided between the PCB boards , the two-layer PCB boards are arranged in a mirror structure, and the coils on the PCB boards are connected by inter-board connecting wires; The surface is completely consistent with the upper surface of the lower PCB board; the coils of two adjacent pairs of PCB boards are connected in series by wires. 3. The high-precision open-type Rogowski coil according to claim 2, characterized in that: it includes two pairs or more than two pairs of PCB boards, each pair of PCB boards includes two layers of PCB boards, and between two adjacent pairs of PCB boards An insulating material is provided, and the coils of two adjacent pairs of PCB boards are connected in series by wires. 4. The high-precision open-type Rogowski coil according to any one of claims 1-3, wherein the PCB board includes an intermediate epoxy layer, and conductor layers and insulating layers are arranged symmetrically on both sides of the intermediate epoxy layer. paint layer. 5. The high-precision open-type Rogowski coil according to any one of claims 1-3, characterized in that: the plate is arranged in a shielding box, and the shielding box is adapted to the shape of the plate; one side of the shielding box is connected by a connecting mechanism . 6. The high-precision open-type Rogowski coil according to claim 4, characterized in that: the plate is arranged in a shielding box, and the shielding box is adapted to the shape of the plate; the shielding box is connected by a connecting mechanism. 7. The high-precision open-type Rogowski coil according to any one of claims 1-3, characterized in that: the coil on the PCB is in the shape of a semicircle. 8. The high-precision open-type Rogowski coil according to claim 4, characterized in that: the coil on the PCB board is semi-circular. 9. The high-precision open-type Rogowski coil according to claim 5, characterized in that: the coil on the PCB board is in the shape of a semicircle. 10. The high-precision open-type Rogowski coil according to claim 2 or 3, characterized in that: the two layers of PCB boards are connected by screws.

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