阅读说明：本技术 一种导体面电流密度分布的测量系统及测量方法 (System and method for measuring conductor plane current density distribution ) 是由 张正卿 吴钫 廖于翔 帅骁睿 张鹏程 吴浩伟 李锐 蔡凯 李鹏 汪文涛 蔡久青 于 2020-12-17 设计创作，主要内容包括：本发明提出一种导体面电流密度分布的测量系统包括测量探针、电流测量传感器、放大电路和数字信号处理模块；测量探针中探针基材是多层柔性电路板；磁通环线圈阵列是沿面电流密度分布方向布置的多组磁通环线圈；磁通环线圈与信号端子的正负连接线分别布置于基材相邻的两层,且正负连接线最近距离平行布置；电流测量传感器用于测量通流导体总电流幅值；放大电路与输出信号端子连接；数字信号处理模块结合测量探针与电流测量传感器测量结果,可以得到导体面电流密度时空分布。本发明所述的一种导体面电流密度测量方法,基于磁场测量反演,方法有效,外部电路简捷,数字信号处理流程高效,适应于导体交变和瞬态面电流密度时空分布的测量需求。(The invention provides a measuring system for conductor plane current density distribution, which comprises a measuring probe, a current measuring sensor, an amplifying circuit and a digital signal processing module, wherein the measuring probe is used for measuring the current density distribution of a conductor plane; the probe substrate in the measuring probe is a multilayer flexible circuit board; the magnetic flux loop coil array is a plurality of groups of magnetic flux loop coils arranged along the distribution direction of the surface current density; the positive and negative connecting wires of the magnetic flux loop coil and the signal terminal are respectively arranged on two adjacent layers of the base material, and the nearest distance between the positive and negative connecting wires is arranged in parallel; the current measuring sensor is used for measuring the total current amplitude of the through-current conductor; the amplifying circuit is connected with the output signal terminal; the digital signal processing module is combined with the measuring probe and the measuring result of the current measuring sensor, and the space-time distribution of the current density of the conductor surface can be obtained. The conductor surface current density measuring method is effective based on magnetic field measurement inversion, has simple and convenient external circuit and high-efficiency digital signal processing flow, and is suitable for measuring requirements of conductor alternation and transient surface current density space-time distribution.)

1. The measuring system for conductor plane current density distribution is characterized by comprising a measuring probe, a current measuring sensor, an amplifying circuit and a digital signal processing module;

the measuring probe comprises a probe substrate, a magnetic flux loop coil array and an output signal terminal;

the probe substrate is a multilayer flexible circuit board and covers the measured surface of the through-current conductor;

the magnetic flux loop coil array is arranged on the probe substrate and comprises a plurality of groups of magnetic flux loop coils arranged along the distribution direction of surface current density, and the normal line of each magnetic flux loop coil is vertical to the probe substrate;

the output signal terminal is arranged on the probe substrate, positive and negative connecting wires of the magnetic flux loop coil and the signal terminal are respectively arranged on two adjacent layers of the substrate, and the nearest distance between the positive and negative connecting wires is arranged in parallel;

the current measuring sensor is used for measuring the total current amplitude of the through-current conductor;

the amplifying circuit is connected with the output signal terminal and is used for amplifying the signal acquired by the measuring probe in proportion;

the digital signal processing module is used for acquiring signals output by the amplifying circuit and the current measuring sensor, and combining the measuring probe and the measuring result of the current measuring sensor, the space-time distribution of the conductor plane current density can be obtained.

2. The measurement system of claim 1, wherein the probe substrate is a flexible circuit board made of polyimide, capable of being attached to a conductor.

3. A measuring system according to claim 1, characterized in that the voltage signal induced by the flux ring coil in the changing magnetic field of the current conductor is representable as:

wherein, B_zMagnitude of magnetic induction u perpendicularly interlinked with said flux-ring coil_mThe voltage induced by the flux loop coil in a changing magnetic field is N, the total number of turns of the flux loop coil is N, the average surrounding area of each turn of the coil is S, and t is a time parameter.

4. A measuring system according to claim 3, characterized in that the voltage signal induced by the flux ring coil in the changing magnetic field of the current conductor is such thatThe method comprises the following steps:

wherein, J_xIs the conductor plane current density component, gamma is the material conductivity, and y is the plane current density distribution direction.

5. Measuring probe according to claim 4, characterized in that the current conductor is referenced y₀Current density distribution at the conductor opposing face y as a reference:

wherein, y_km-1≤y<y_km(ii) a i is the ith magnetic flux loop coil, and i is 1-20; k is the number of flux loop coils accessed in the measurement; gamma is the material conductivity; j is conductor area current density.

6. Measuring probe according to claim 5, characterized in that the amplitude E of the reference point electric field component of the through-current conductor_x0Comprises the following steps:

wherein, y₀For the y-direction starting reference point coordinate of the measured conductor, y_kFor the maximum reference point coordinate in the y direction of the conductor under test, E_x0For the electric field component E at the reference point_xThe amplitude of (c).

7. Measuring probe according to claim 5, characterized in that the areal current density distribution of the through-current conductor is:

J_x(y,t)＝J_x/y0(y,t)+E_x0×γ。

8. a measuring method for measuring conductor plane current density distribution by using the measuring probe and current measuring sensor according to any one of claims 1-7, comprising the following steps:

step 1: obtaining magnetic flux loop coil array measurement output voltage signal U_mi(t) and the current measuring sensor measures the current amplitude I_m(t)；

Step 2: outputting the measured output voltage signal U_mi(t) and the current amplitude I_m(t) inputting the data into a digital signal processing module for data processing to obtain the current density distribution of the conductor plane;

the method also comprises the following steps in the step 2:

calculated to reference point y₀Conductor-opposing-surface current density distribution as a reference:

wherein, y_k-1≤y<y_k(ii) a i is the ith magnetic flux loop coil, and i is 1-20; k is an amplification coefficient of the measurement amplification circuit, N is the total number of turns of the magnetic flux loop coil, S is the average surrounding area of each turn of the coil, t is a time parameter, gamma is the conductivity of the material, K is the number of the magnetic flux loop coils connected in the measurement, and J is the current density of a conductor surface;

calculating the amplitude E of the electric field component of the reference point_x0：

Wherein E is_x0For the electric field component E at the reference point_xThe amplitude of (d);

calculating the current density distribution of the conductor surface:

J_x(y,t)＝J_x/y0(y,t)+E_x0×γ。

9. the measurement method of claim 8, wherein the measurement probe flux ring coil array measurement output voltage signal is scaled by a measurement amplification circuit, and the output voltage signal is:

U_mi(t)＝K×u_mi(t)

wherein u is_mi(t) measuring voltage signals for the measuring probe flux ring coil array.

10. The method according to claim 8, wherein the digital signal processing module is configured to determine the reference point electric field component amplitude parameter E when the measurement probe is used alone_x0And setting zero.

Technical Field

The invention relates to the field of current density measurement, in particular to a system and a method for measuring conductor plane current density distribution.

Background

When alternating or transient current flows in the conductor, alternating or transient electromagnetic fields can be generated inside and outside the through-current conductor, induced current generated by the changed magnetic field in the conductor or an adjacent conductor can generate a superposition or offset effect on the basis of original current, a skin effect and a proximity effect are generated, and the current density is enabled to be unevenly distributed in the conductor.

The current skin effect and the proximity effect are widely existed in power supply bus bars and laminated bus bars, switch cabinet bus bars, transformers or inductance windings and various electromagnetic device conductive structures. In addition, the current density distribution in the conductor can be influenced by the edge effect and the fact that the conductor is in a complex external variable magnetic field, and the factors can generally reduce the effective sectional area of the conductor, so that the loss is increased, and the temperature rise is increased; the local electromagnetic field distribution and the radiation emission characteristics of the conductor are changed, so that the electromagnetic compatibility problem of equipment or devices is caused; at the same time, the electromagnetic force distribution on the conductor can be influenced, and the risks of vibration and structural safety are brought. Therefore, the measurement and analysis of the distribution characteristics of the high-frequency current density in the conductor are of great significance to the comprehensive optimization design of the thermal, structural and electromagnetic characteristics of the through-flow part of the relevant equipment and device, and an effective current density measurement method is needed to provide necessary experimental test means and verification method for the research of the current density distribution influence factors of the conductor.

In general, the size difference of the through-flow cross section of a conductor such as a bus bar in two dimensions of thickness and width is large, and the skin effect causes the current to be mainly distributed on the surface of the conductor, so that the alternating or transient current in the through-flow conductor of an electric or electromagnetic device generally has the surface current characteristic. The inversion by utilizing magnetic field measurement is one of effective methods for measuring the current density of a conductor surface, the method requires that the magnetic field measurement and the inversion mode are effective, the size of a magnetic field sensor is small, and the magnetic field sensor can be tightly attached to a measured conductor for measurement. At present, the method is not widely applied, a common magnetic field measurement sensor is large in size, not easy to install and arrange, and limited in measurement bandwidth, precision and resolution, and cannot meet the measurement requirement of conductor plane current density distribution.

Disclosure of Invention

The invention aims to provide a measuring system for conductor plane current density distribution aiming at the prior art, which is characterized by comprising a measuring probe, a current measuring sensor, an amplifying circuit and a digital signal processing module;

the measuring probe comprises a probe substrate, a magnetic flux loop coil array and an output signal terminal;

the probe substrate is a multilayer flexible circuit board and covers the measured surface of the through-current conductor;

the magnetic flux loop coil array is arranged on the probe substrate and comprises a plurality of groups of magnetic flux loop coils arranged along the distribution direction of surface current density, and the normal line of each magnetic flux loop coil is vertical to the probe substrate;

the output signal terminal is arranged on the probe substrate, positive and negative connecting wires of the magnetic flux loop coil and the signal terminal are respectively arranged on two adjacent layers of the substrate, and the nearest distance between the positive and negative connecting wires is arranged in parallel;

the current measuring sensor is used for measuring the total current amplitude of the through-current conductor;

the amplifying circuit is connected with the output signal terminal and is used for amplifying the signal acquired by the measuring probe in proportion;

the digital signal processing module is used for acquiring signals output by the amplifying circuit and the current measuring sensor, and combining the measuring probe and the measuring result of the current measuring sensor, the space-time distribution of the conductor plane current density can be obtained.

Furthermore, the probe substrate is a flexible circuit board made of polyimide, and a conductor can be attached to the flexible circuit board.

Further, the voltage signal induced by the flux ring coil in the changing magnetic field can be expressed as:

wherein, B_zMagnitude of magnetic induction u perpendicularly interlinked with said flux-ring coil_mThe voltage induced by the flux loop coil in a changing magnetic field is N, the total number of turns of the flux loop coil is N, the average surrounding area of each turn of the coil is S, and t is a time parameter.

Furthermore, the voltage signal induced by the magnetic flux loop coil in the changing magnetic field is satisfiedThe method comprises the following steps:

wherein, J_xIs the conductor plane current density component, gamma is the material conductivity, and y is the plane current density distribution direction.

Furthermore, the current conductor is referenced to a reference point y₀Current density distribution at the conductor opposing face y as a reference:

wherein, y_km-1≤y<y_km(ii) a i is the ith magnetic flux loop coil, and i is 1-20; k is the number of flux loop coils accessed in the measurement; gamma is the material conductivity; j is conductor area current density.

Furthermore, the amplitude E of the reference point electric field component of the current conductor_x0Comprises the following steps:

wherein, y₀For the y-direction starting reference point coordinate of the measured conductor, y_kFor the maximum reference point coordinate in the y direction of the conductor under test, E_x0For the electric field component E at the reference point_xThe amplitude of (c).

Furthermore, the areal current density distribution of the current conductor is:

J_x(y，t)＝J_x/y0(y，t)+E_x0×γ。

there is also provided a measuring method for measuring conductor plane current density distribution by the measuring system according to any one of claims 1 to 7, in which the measuring method is implemented by matching the measuring probe with a current measuring sensor, and the method comprises the following steps:

step 1: obtaining magnetic flux loop coil array measurement output voltage signal U_mi(t) and the current measuring sensor measures the current amplitude I_m(t)；

Step 2: outputting the measured output voltage signal U_mi(t) and the current amplitude I_m(t) inputting the data into a digital signal processing module for data processing to obtain the current density distribution of the conductor plane;

the method also comprises the following steps in the step 2:

calculated to reference point y₀Conductor-opposing-surface current density distribution as a reference:

wherein, y_k-1≤y<y_k(ii) a i is the ith magnetic flux loop coil, and i is 1-20; k is the amplification coefficient of the measurement amplification circuit, N is the total number of turns of the magnetic flux loop coil, and S is the average surrounding area of each turn of the coilT is a time parameter, gamma is the material conductivity, k is the number of flux loop coils accessed in the measurement, and J is the conductor plane current density;

calculating the amplitude E of the electric field component of the reference point_x0：

Wherein E is_x0For the electric field component E at the reference point_xThe amplitude of (d);

calculating the current density distribution of the conductor surface:

J_x(y,t)＝J_x/y0(y,t)+E_x0×γ。

furthermore, the output voltage signal measured by the measuring probe flux loop coil array is proportionally amplified by a measuring amplifying circuit, and the output voltage signal is as follows:

U_mi(t)＝K×u_mi(t)

wherein u is_mi(t) measuring voltage signals for the measuring probe flux ring coil array.

Furthermore, when the measuring probe is used alone, the amplitude parameter E of the electric field component of the reference point in the digital signal processing module_x0And setting zero.

The invention has the advantages that:

the conductor surface current density distribution measuring probe provided by the invention adopts a Flexible Printed Circuit (FPC) structure, is light in structure and low in cost, and is suitable for surface mounting of conductors to be measured in different shapes. Meanwhile, the coil circuit parameters are controllable, the stray parameters are small, the measurement frequency bandwidth is large, the number of layers, the size, the arrangement mode and the like of the coils of the magnetic flux loop coil array can be adaptively adjusted according to the measurement spatial resolution and the measurement precision requirements, and the specification of a serialized probe is formed.

The conductor surface current density measuring method is based on magnetic field measurement inversion, is effective, has simple and convenient external circuit and high-efficiency digital signal processing flow, and is suitable for measuring requirements of conductor alternation and transient surface current density space-time distribution.

Drawings

FIG. 1 is a schematic structural diagram of a system for measuring current density distribution of a conductor plane according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a measurement probe in a measurement system for conductor plane current density distribution according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a magnetic flux loop coil wiring in a system for measuring current density distribution of a conductor plane according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a digital signal processing flow in a system for measuring current density distribution of a conductor plane according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a typical conductor plane current density space-time distribution measurement result obtained by a conductor plane current density distribution measurement system according to an embodiment of the present invention;

fig. 6 is a schematic flow chart of a method for measuring current density distribution of a conductor plane according to an embodiment of the present invention.

Detailed Description

The technical solution of the present invention will be described in more detail with reference to the accompanying drawings, and the present invention includes, but is not limited to, the following embodiments.

As shown in fig. 1, the present invention provides a system for measuring current density distribution of a conductor plane, which includes a measuring probe, a current measuring sensor, an amplifying circuit and a digital signal processing module.

As shown in fig. 2-3, the measuring probe structure includes a probe substrate, a flux loop coil array, and an output signal terminal; the probe substrate is of a multilayer structure, covers the surface to be tested of the through-current conductor, adopts a Flexible Printed Circuit (FPC) structure, is made of polyimide, is light and thin, has good flexibility, can be perfectly attached to the conductor to be tested, and is convenient to mount and maintain; the magnetic flux loop coil array comprises a plurality of groups of magnetic flux loop coils which are uniformly arranged on the probe substrate along the surface current density distribution direction, and the normal line of each magnetic flux loop coil is vertical to the probe substrate; the output signal terminal sets up on the probe substrate, and each magnetic flux loop coil arranges respectively in the adjacent two-layer of substrate with the positive and negative connecting wire of output signal terminal, and nearest distance parallel arrangement to reduce probe stray parameter.

In this embodiment, the probe substrate is a complete four-layer FPC substrate with a thickness of less than 0.5mm, and N-20 sets of magnetic flux loop coils are arranged in the current density distribution direction (y direction) in total, and are numbered 1 to 20 in sequence, each set of magnetic flux loop coils is designed as a single-layer 6-turn coil, and four layers are connected in series, the total number of turns N is 24 turns, the average loop area S of each turn of coil is 0.05m x 0.005m, and the NS value of each set of magnetic flux loop coils is 6 × 10^-3m²。

It should be understood that the number of coils, the number of layers, the NS value, and the arrangement of the flux ring coil array can be adaptively designed and adjusted according to the surface size of the conductor to be measured, the frequency and the amplitude of the current density to be measured, and the requirements of the spatial resolution and the measurement precision of the measurement.

The current measuring sensor is used for measuring the total current amplitude of the through-flow conductor, and can adopt a Rogowski coil sensor which is arranged around the outer side of the conductor.

The amplifying circuit is connected with an output signal terminal of the measuring probe and is used for carrying out proportional amplification on the signals collected by the measuring probe.

The digital signal processing module is used for acquiring signals output by the amplifying circuit and the current measuring sensor and combining the measuring probe and the measuring result of the current measuring sensor to obtain the space-time distribution of the current density of the conductor surface.

As shown in fig. 4, 20 sets of flux-ring coils of the measuring probe are all switched in, and the voltage signal induced by the flux-ring coils in the changing magnetic field can be represented as follows:

wherein, B_zMagnitude of magnetic induction, u, being perpendicular interlinkage with flux-loop coil_mFor the voltage induced by the flux loop coil in a varying magnetic field, N is the total number of turns of the flux loop coilS is the average surrounding area of each turn of coil, and t is a time parameter.

According to the Faraday's law of electromagnetic induction, the rate of change of the electric field E and the magnetic flux density B induced on the surface of a conductor by an alternating or transient electromagnetic field is related as follows:

wherein E is an induced electric field.

And in the conductor material, the induced electric field and the current density amplitude satisfy the constitutive equation:

J＝Eγ (3)

wherein gamma is the material conductivity and J is the current density.

In the combination formula (2) and the formula (3), the obtained current density distribution in the conductor and the change rate of the magnetic induction strength satisfy the following relation:

in this embodiment, the tested conductor is a bus with a rectangular cross section, and the conductor current can be approximately regarded as a surface current (J)_z0), the current flowing direction is x-direction, the surface current density gradient direction is mainly y-direction, and the conditions are satisfiedCombining equations (1) and (4) together yields the following relationship:

the induced voltage signal is amplified in proportion by the amplifying circuit, and the output voltage signal is U_mi(t)＝K×u_mi(t), i is 1-20; wherein K is the amplification factor of the measurement amplification circuit.

The current measuring sensor measures the current amplitude value I_m(t)。

Digital signal processingThe module obtains an output voltage signal as U_mi(t) and a measured current amplitude of I_m(t) calculating to reference point y₀Current density distribution at the conductor opposing face y as a reference:

wherein, y_km-1≤y<y_km(ii) a i is the ith magnetic flux loop coil, and i is 1-20; k is the number of flux loop coils accessed in the measurement; gamma is the material conductivity; j is conductor area current density.

Calculating the amplitude E of the electric field component of the reference point_x0Comprises the following steps:

wherein, y₀For the y-direction starting reference point coordinate of the measured conductor, y_kFor the maximum reference point coordinate in the y direction of the conductor under test, E_x0For the electric field component E at the reference point_xThe amplitude of (c).

Calculating the current density distribution of the conductor surface:

J_x(y,t)＝J_x/y0(y,t)+E_x0×γ (8)

in another embodiment, the measuring probe in the measuring system can also be used independently, the digital signal processing module does not receive the output signal of the current sensor, and the reference point electric field component amplitude parameter E_x0Setting zero; digital signal processing module output with reference point y₀Reference conductor-opposed surface current densityThe space-time distribution of current density on the opposite surfaces of the conductor can be drawn, and the reference point y is used in the mode₀Relative surface current densityThe output is 0 and the current density output at position y is

As shown in FIG. 5, when the measuring probe is used with a current measuring sensor, the digital signal processing module outputs a conductor plane current density J_x(y, t), the space-time distribution of the conductor plane current density can be plotted. FIG. 5 illustrates a typical conductor plane current density spatiotemporal distribution measurement of a conductor flowing a transient current pulse in one embodiment. Wherein, the abscissa is a time axis t, and the ordinate is a space axis in the y direction of the conductor.

As shown in fig. 6, the present invention provides a method for measuring conductor surface current density distribution, which measures conductor surface current density through a measuring system, and comprises the following steps:

step 1: obtaining magnetic flux loop coil array measurement output voltage signal U_mi(t) and the current measuring sensor measures the current amplitude I_m(t)；

The measuring probe magnetic flux loop coil array measures the output voltage signal as U_mi(t) (i is 1-20), the signal is amplified in proportion by a measurement amplifying circuit, and the output voltage signal is U_mi(t)＝K×u_mi(t), wherein K is the amplification factor of the measurement amplification circuit. The current measuring sensor measures the current amplitude value I_m(t)。

Step 2: will output a voltage signal U_mi(t) and the current amplitude I_mAnd (t) inputting the data into a digital signal processing module for data processing to obtain the current density distribution of the conductor plane.

The specific method comprises the following steps:

calculated to reference point y₀Conductor-opposing-surface current density distribution as a reference:

wherein, y_k-1≤y<y_k(ii) a i is the ith flux ring coil, and i is 1-20.

Calculating the amplitude E of the electric field component of the reference point_x0：

Calculating the current density distribution of the conductor surface:

J_x(y,t)＝J_x/y0(y,t)+E_x0×γ (11)

when the measurement is carried out by the measuring probe in the measuring system, the digital signal processing module does not receive the output signal of the current sensor, and the reference point electric field component amplitude parameter E_x0Setting zero; digital signal processing module output with reference point y₀Reference conductor-opposed surface current densityThe space-time distribution of current density on the opposite surfaces of the conductor can be drawn, and the reference point y is used in the mode₀Relative surface current densityThe output is 0 and the current density output at position y is

In the prior art, the magnetic probes are mostly of single coil packaging structures, are not easy to attach to a measured conductor for installation, and need to use a large number of magnetic probes in the same arrangement form, so that the use cost is high; the measuring probe is an array structure based on the FPC substrate, and is easy to be adjusted adaptively according to a measured conductor, the thickness of the measuring probe for current density distribution in the invention is only 0.5mm, the weight is less than 50g, the spatial resolution is less than or equal to 5mm, the FPC manufacturing process is mature, and the cost is low; the overall cost of the measuring probe is only similar to that of a magnetic probe with a single packaging structure, and the cost is greatly saved.

The present invention is not limited to the above embodiments, and those skilled in the art can implement the present invention in other various embodiments according to the disclosure of the embodiments and the drawings, and therefore, all designs that can be easily changed or modified by using the design structure and thought of the present invention fall within the protection scope of the present invention.