A method for manufacturing a differential current detector

Abstract

The present invention relates to a method for manufacturing a differential current detector, which is applied to the design of pulse current detectors with leading-edge times in the order of nanoseconds to hundreds of nanoseconds and amplitudes in the order of hundreds of kA. This method solves the technical problem that the existing development of differential current detectors (B-dots) fails to consider the influence of structural errors, resulting in poor B-dot consistency. The method for manufacturing the differential current detector includes the following steps: 1) setting a circuit model of the B-dot; the circuit model of the B-dot includes a B-dot inductor L, a signal cable impedance Z connected to the B-dot inductor L, and a current to be measured I o Mutual inductance M between B-dot and B-dot; 2) According to the B-dot output signal amplitude u w , constraining the size of the B-dot ring; 3) determining the size of the B-dot along the axis of the shielding hole, the position of the B-dot ring, and the angle of the B-dot ring surface based on the distribution of the magnetic field B inside the shielding hole; 4) fabricating a differential current detector based on the size of the B-dot ring, the size of the B-dot along the axis of the shielding hole, the position of the B-dot ring, and the angle of the B-dot ring surface.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a differential current detector, which is applied to the design of a pulse current detector with a leading edge time in the order of ns to hundreds of ns and an amplitude in the order of hundreds of kA. Background Art

[0002] In pulsed power devices, electromagnetic induction coil detectors are commonly used to measure pulsed currents in the hundreds of kA range. When the detector circuit parameters are properly set, and its output signal is a differential waveform of the current pulse to be measured, it is called a differential current detector (also known as a B-dot). The differential signal obtained by a differential current detector can be restored through numerical integration or an RC integration circuit. If numerical integration is used, the measurement system hardware is very simple, consisting solely of the B-dot itself and the measurement cable; the response characteristics of the measurement system are largely determined by the B-dot's geometric structure.

[0003] B-dots are currently widely used in pulsed power devices. The PBFA-Z (ParticleBeam Fusion Accelerator) at Sandia Laboratories uses this B-dot to measure currents in magnetically insulated transmission lines. Wei Bing and others at the China Academy of Engineering Physics also used B-dots to measure currents in vacuum magnetically insulated transmission lines at the Yang accelerator and the Julong-1 accelerator. These studies focused on electrical parameters such as B-dot inductance and load impedance, as well as performance parameters such as leading-edge response and frequency response. Structural parameters were only briefly discussed, generally including only the annular area. The impact of structural errors on B-dot performance was not analyzed, and structural errors were not properly constrained in the design. Even B-dots with identical structures can have amplitude scale differences exceeding 30%. The response characteristics of B-dots often rely on calibration experiments.

[0004] Large pulse power devices have complex structures and variable current paths, often equipped with dozens or even hundreds of B-dot probes. This places high demands on B-dot consistency. This requires rationally constraining error parameters based on the impact of structural errors on B-dot performance, in order to obtain B-dot probes with high consistency. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the influence of structural errors is not considered in the development of existing differential current detectors (B-dots), resulting in poor B-dot consistency, and to provide a method for manufacturing a differential current detector to improve the B-dot manufacturing method.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for manufacturing a differential current detector is characterized in that it includes the following steps:

[0008] 1) Set the circuit model of B-dot;

[0009] The circuit model of the B-dot includes the B-dot inductor L, the signal cable impedance Z connected to the B-dot inductor L, and the current to be measured I o Mutual inductance M between B-dot;

[0010] 2) According to the B-dot output signal amplitude u w , constraining the B-dot ring size; the B-dot ring size is the equivalent ring surface area nS:

[0011] 2.1) Estimate the B-dot output signal amplitude u w for:

[0012] u w =MI o / t r

[0013] Where, t r The current to be measured I o cutting edge;

[0014] 2.2) Through step 2.1) w =MI o / t r , determine the B-dot ring size nS:

[0015] nS=MI o / B i

[0016] Where B i is the magnetic field at B-dot, and the measured current I o Proportional; n is the number of turns of the B-dot ring, S is the area of the B-dot ring;

[0017] 3) Based on the distribution of the magnetic field B inside the shielding hole, determine the size of the B-dot along the axis of the shielding hole, the position of the B-dot ring body, and the B-dot ring surface angle;

[0018] The specific method for determining the size of the B-dot along the axis of the shielding hole is:

[0019] A1) Simulate the magnetic field inside the shielding hole B

[0020] Define the magnetic field B inside the shielding hole along the x-axis, the axis of the shielding hole along the y-axis, the coordinate origin o is located at the center of the outer edge of the shielding hole, and the -y direction represents the depth inside the shielding hole;

[0021] Calculate the magnetic flux dΦ in the area element in the y-axis direction y

[0022]

[0023] Where: a is the starting point of the area element in the y-axis direction, l y is the total length of the area element along the y-axis, d z is the width of the area element in the y-axis direction, B0 is the magnetic field on the surface of the shielding hole, and k is a constant;

[0024] A2) According to the magnetic flux dΦ in the area element in the y-axis direction y , determine the total length l of the area element of B-dot along the y-axis y , obtain the dimension along the axis of the shielding hole;

[0025] The specific determination of the B-dot ring position range is:

[0026] B1) When z = 0, based on the distribution of the magnetic field B inside the shielding hole, under conditions of constant depth, the deviation of the magnetic field at different positions along the x-axis relative to the magnetic field along the shielding hole axis is compared. When the magnetic field variation is less than 5%, it can be obtained that the position variation of the B-dot ring along the x-axis does not exceed ±0.1d, where d is the aperture of the shielding hole;

[0027] B2) When x = 0, based on the magnetic field B distribution inside the shielding hole, under conditions of constant depth, the deviation of the magnetic field at different positions along the z-axis relative to the magnetic field along the shielding hole axis is compared. When the magnetic field variation is less than 5%, it can be found that the position variation of the B-dot ring along the z-axis does not exceed ±0.17d;

[0028] B3) When the magnetic flux dΦ in the area element in the y-axis direction y Less than 8.4%, it can be obtained that the position change of the B-dot ring in the y-axis direction does not exceed ±0.088d / k;

[0029] 4) A differential current detector is manufactured based on the B-dot ring size, the B-dot size along the shield hole axis, the B-dot ring position, and the B-dot ring surface angle.

[0030] Furthermore, in step 3), the B-dot annular angle is determined as follows:

[0031] When the B-dot torus is defined as perpendicular to the magnetic field at its location, the location of the B-dot torus is referred to as the reference plane, and the angle between the B-dot torus and the reference plane is referred to as the B-dot torus angle θ.

[0032] Furthermore, step A2) is specifically as follows:

[0033] The size of the B-dot along the shielding hole axis is less than or equal to 3d / k.

[0034] Furthermore, in step 2.1), the B-dot output signal amplitude u w The value range is u w ∈(100,1000).

[0035] Furthermore, in step 3, the B-dot annular surface angle θ is ≤ 18°.

[0036] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0037] The manufacturing method of the differential current detector of the present invention analyzes the magnetic field distribution inside the introduced shielding hole, constrains the size of the B-dot ring body, and puts forward requirements for the size of the B-dot along the axis of the shielding hole, the position of the B-dot ring body, and the angle of the B-dot ring surface. This solves the technical problem of poor B-dot consistency caused by failure to consider the influence of structural errors in the development of existing differential current detectors, and improves the performance consistency requirements of B-dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the working principle diagram of the existing B-dot. o is the current to be measured, B is the current to be measured I o The magnetic field, I1 is the current generated in the B-dot ring, i.e. the loop current, Z is the signal cable impedance, u w is the load voltage, i.e. the B-dot output signal amplitude.

[0039] Figure 2 This is the simplified circuit model of B-dot in the present invention. In the figure, L is the B-dot inductance, Z is the signal cable impedance, and I o is the current to be measured (i.e. the pulse current on the high voltage electrode), M is the current to be measured I o The mutual inductance between the B-dot and the B-dot, I1 is the loop current generated in the B-dot ring, u w B-dot output signal amplitude.

[0040] Figure 3 Schematic diagram of B-dot installation in an embodiment of the present invention. The dotted line in the figure is the boundary line between the shielding hole and the ground electrode inside the device, which is called the shielding hole outer edge line.

[0041] Figure 4 Schematic diagram of the shielding hole and magnetic field model direction setting in an embodiment of the present invention, wherein the magnetic field B inside the shielding hole is along the x-axis direction, and the axis of the shielding hole is along the y-axis direction.

[0042] Figure 5 Schematic diagram of magnetic field distribution in the shielding hole when x=0 in an embodiment of the present invention.

[0043] Figure 6 Schematic diagram of magnetic field distribution in the shielding hole when z=0 in an embodiment of the present invention.

[0044] Figure 7 Schematic diagram of the area element of B-dot along the y-axis in an embodiment of the present invention, where a represents the starting position of the area element in the y-axis direction, b represents the end position of the area element in the y-axis direction, and l y It represents the total length of the area element in the y-axis direction, and dz represents the width of the area element in the y-axis direction.

[0045] Figure 8 Schematic diagram of the area element of B-dot along the z-axis in the embodiment of the present invention. z is the length of the area element in the z-axis direction, dy is the width of the area element in the z-axis direction, and m is the distance between the center of the area element in the z-axis direction and the y-axis.

[0046] Figure 9 for Figure 8 Schematic diagram of the relationship between the flux deviation and the center position of the area element of different lengths of the B-dot along the z-axis at y = -0.1d, where d is the aperture of the shielding hole.

[0047] Figure 10 for Figure 8 Schematic diagram of the relationship between the magnetic flux deviation of area elements of different lengths and the center position of the area element at y = -0.3d along the z-axis of the B-dot.

[0048] Figure 11 for Figure 8 Schematic diagram of the relationship between the flux deviation of area elements of different lengths and the center position of the area element at y=-0.5d along the z-axis.

[0049] Figure 12 for Figure 8 Schematic diagram of the relationship between the magnetic flux deviation of area elements of different lengths and the center position of the area element at y = -0.7d along the z-axis in the B-dot.

[0050] Figure 13 Schematic diagram of the angle between the toroidal surface of the B-dot ring and the direction of the magnetic field in an embodiment of the present invention.

[0051] Figure 14 This is a schematic diagram of a multi-turn B-dot ring body in an embodiment of the present invention. The B-dot ring body in the figure is a multi-turn coil made of metal wire. The shape of the coil is not fixed and can be circular or rectangular. The figure shows a schematic diagram of a circular multi-turn B-dot ring body.

[0052] Figure 15This is a schematic diagram of a single-turn B-dot ring body in an embodiment of the present invention. The B-dot ring body in the figure is a single-turn coil made of metal wire. The shape of the coil is not fixed and can be circular or rectangular. The figure shows a schematic diagram of a circular single-turn B-dot ring body.

[0053] The accompanying drawings are:

[0054] 1-B-dot ring body, 2-shielding hole, 3-signal cable, 4-ground electrode, 5-high voltage electrode. DETAILED DESCRIPTION

[0055] To facilitate understanding of the relevant content of the present invention, the working principle of B-dot is introduced as follows:

[0056] like Figure 1 As shown, B-dot is essentially a single-turn or multi-turn coil. o When the magnetic field B changes with time, the magnetic flux inside the B-dot ring changes, inducing a current I1 on the B-dot ring body. I1 flows through the load Z (usually the signal cable impedance), generating a voltage u on Z. w ,u w This is the output signal of B-dot.

[0057] Usually the B-dot ring is small in size and the magnetic field at its location is approximately uniform, so the magnetic flux Φ in the B-dot ring surface is B =B ⊥ A, where B ⊥ is the component of the magnetic field at B-dot perpendicular to the torus, A is the equivalent torus area, Where n is the number of turns of the B-dot ring, S i is the area of the i-th toroidal surface. Generally, if the areas of all toroids are equal, then A = nS, where S is the area of a single toroidal turn. From the flux calculation formula, we know that the effective portion of magnetic field B is the component perpendicular to the B-dot toroidal surface. To maximize magnetic flux, the B-dot toroidal surface is often perpendicular to the magnetic field being measured. The following analyses, except for the fourth angle analysis, are performed under the assumption that the toroidal surface is perpendicular to the magnetic field.

[0058] Since the current to be measured I o The magnetic field will be shielded by the ground electrode 4, so that the B-dot can contact the current to be measured I o The magnetic field B inside the shielding hole is generated. There is a hole in the ground electrode 4. The B-dot passes through the hole and contacts the current to be measured I oMagnetic field B. In order to avoid serious electric field distortion near the B-dot, and thus insulation problems (such as flashover discharge on the B-dot surface, or discharge between the B-dot and the high-voltage electrode 5, or discharge between the B-dot and the ground electrode, etc.), the B-dot ring body 1 is usually not higher than the hole, but is completely inside the hole. Since the hole will have a certain shielding effect on the magnetic field B, the hole is called a shielding hole. In short, the function of the shielding hole is to enable the B-dot to contact the current to be measured I o The first is to prevent the magnetic field B from occurring near the B-dot, and the second is to prevent serious electric field distortion from occurring near the B-dot, which in turn may cause insulation problems.

[0059] The manufacturing method of the differential current detector of the present invention controls the range of B-dot structural error based on the B-dot performance consistency requirements. It mainly includes the following steps:

[0060] 1. According to the B-dot output signal amplitude u w , constrain the size of B-dot ring 1

[0061] like Figure 2 As shown, based on the simplified B-dot circuit model, the amplitude u of the B-dot output (differential) signal is estimated. w for:

[0062]

[0063] Among them, t r The current to be measured I o Front edge, M is the current between B-dot and the measured current I o The mutual induction between.

[0064] In engineering, based on signal-to-noise ratio and insulation considerations, the B-dot output signal amplitude u is required to be w Should be between 100 and 1000 V. According to M = nSB i / I o ,have

[0065]

[0066] Where B i is the magnetic field at B-dot, and the measured current I o proportional to;

[0067] The equivalent annular area nS is defined as the annular size, and formula (2) gives the design range of the annular size.

[0068] For coaxial transmission lines, the above formula can be transformed into

[0069]

[0070] b is the inner surface radius of the outer cylinder of the transmission line, and μ is the magnetic permeability of the transmission line.

[0071] 2. According to the magnetic field distribution inside shielding hole 2, determine the size limit of B-dot along the axis of shielding hole 2

[0072] like Figure 3 As shown, Figure 3 The dashed line marks the boundary between the shielding hole and the ground electrode 4 within the device, referred to as the shielding hole outer edge. Typically, the B-dot ring 1 is located within the shielding hole 2. Typically, the shielding hole 2 is on the order of centimeters, corresponding to a cutoff frequency of several GHz. However, the pulsed current from the high-voltage electrode 5 discussed in this invention has a frequency below tens of MHz. Therefore, the electromagnetic wave of the pulsed current is cut off by the shielding hole 2, and the magnetic field B inside the shielding hole 2 decays exponentially within the shielding hole 2:

[0073] B=B0e -k*h / d (4)

[0074] Where B0 is the surface magnetic field of the shielding hole, h is the depth of shielding hole 2, d is the diameter of shielding hole 2, k is a constant, and B0 is the magnetic field at the outer edge of shielding hole 2.

[0075] like Figure 4 As shown, the magnetic field B inside the shielding hole 2 is simulated. The direction of the magnetic field B inside the shielding hole 2 is set, where the magnetic field B inside the shielding hole 2 is along the x-axis direction and the axis of the shielding hole 2 is along the y-axis direction. The coordinate origin o is located at the center of the outer edge of the shielding hole 2, and the -y direction indicates that it is deep inside the shielding hole 2. Figure 5 As shown, it is the simulation result of the magnetic field B inside the shielding hole 2.

[0076] exist Figure 4 In the coordinate system shown, according to formula (4), the attenuation of the magnetic field B inside the shielding hole 2 along the y direction is

[0077] B=B0e -k*y (5)

[0078] like Figure 7 As shown, take the area element in the y-axis direction, the starting point of the area element in the y-axis direction is at a, the end point is at b, and the total length is l y = ba, width is dz (the units of the above lengths are all the diameter d of the shield hole 2). Calculate the magnetic flux dΦ in the area element in the y-axis direction y =dz∫Bdy.

[0079] Substitute equation (5) into dΦ y =dz∫Bdy, we have

[0080]

[0081] In order to study the area element length l y Magnetic flux dΦy The influence of , the starting point a of the area element in the y-axis direction is fixed (i.e. a remains unchanged), then dzB0e in formula (6) -ak / k is a constant, the length of the area element is l y pass Term for magnetic flux dΦ y Have an impact. With l y Increase, dΦ y Gradually approaches the constant dzB0e -ak / k. When (i.e. l y >3d / k), dΦ y With dzB0e -ak / k is less than 5%, at this time the magnetic flux dΦ y Almost no y changes with the change of y The part greater than 3d / k has a negative effect on the magnetic flux dΦ y The contribution of the B-dot ring 1 in the y-axis direction is less than 5%. Therefore, the size of the B-dot ring 1 in the y-axis direction should be controlled within the range of 3d / k. The constant k can be calculated from the magnetic field simulation data at the axis of the shielding hole 2.

[0082] 3. Determine the position limit of B-dot ring 1 based on the magnetic field distribution inside shielding hole 2

[0083] 1) Determine the x-direction position limit based on the magnetic field distribution on the z=0 plane

[0084] like Figure 6 As shown, according to the magnetic field distribution data of the z=0 plane, under the condition of equal depth (equal y), with the magnetic field of the axis of the shielding hole 2 (i.e. x=0) as the benchmark, the deviation of the magnetic field at different x positions relative to the magnetic field of the axis of the shielding hole 2 is compared. When the magnetic field change does not exceed 5%, the position change in the x-axis direction does not exceed ±0.1d.

[0085] 2) Determine the z-axis position limit based on the magnetic field distribution on the x=0 plane

[0086] like Figure 8 As shown, the schematic diagram of the magnetic flux of B-dot in the z-axis direction is shown. Figure 8 Middle z is the length of the area element in the z-axis direction, dy is the width of the area element in the z-axis direction, m is the distance between the center of the area element in the z-axis direction and the y-axis, and the magnetic field is along the x-axis direction. The magnetic flux in the area element in the z-axis direction is dΦ z =dy∫Bdz, the magnetic flux is proportional to the length l of the magnetic field along the area element z Integral of direction.

[0087] like Figures 9 to 12 As shown in the figure, the deviation of the area element flux under different lengths and different center positions from the area element flux under the condition of m=0 is shown in the figure. Figures 9 to 12 As can be seen from the figure, the magnetic flux deviation is basically consistent with the deviation of the magnetic field at the center point of the area element in the z-axis direction. Therefore, the magnetic field deviation at the center point of the area element in the z-axis direction can be directly used for analysis.

[0088] like Figure 5 As shown, the magnetic field distribution data of the x=0 plane. Under the condition of equal depth (equal y), the axis (z=0) magnetic field is used as the reference to compare the deviation of the magnetic field at different z positions relative to the axis magnetic field. When the magnetic field changes by no more than 5%, the position change in the z-axis direction does not exceed ±0.17d.

[0089] 3) Determine the Y-axis position limit (i.e., position range) based on the magnetic field distribution on the axis of shield hole 2

[0090] According to formula (4), when the B-dot size is determined, the magnetic flux is only related to e -ak related.

[0091] If the deviation caused by position is required to be no more than 10% (including the deviation caused by position changes in the x-axis, y-axis, and z-axis directions), then the magnetic flux deviation caused by the y-axis position shall not exceed 8.4%, thus obtaining that the y-axis position change is within the range of ±0.088d / k.

[0092] 4. Determine the B-dot torus angle limit

[0093] For B-dot, when working, the B-dot ring surface is required to be perpendicular to the magnetic field B (the position of the ring surface at this time is defined as the working reference plane). At this time, the B-dot measurement circuit output voltage u w Maximum. Figure 13 As shown in the figure, in actual operation, due to installation reasons, the B-dot annulus often has a certain angle θ with the working reference plane (θ = 0° on the reference plane), resulting in a discrepancy between the actual B-dot output and the theoretical output. Angle θ is defined as the B-dot annulus angle.

[0094] Under uniform magnetic field conditions, the B-dot output amplitude is proportional to the projected area of the B-dot ring surface on the reference plane. According to the geometric relationship, the B-dot output amplitude is proportional to cosθ.

[0095] In this embodiment, the angle θ corresponding to a 5% deviation in the projected area is 18°, so during the manufacturing process, it should be ensured that the deviation between the B-dot annular surface angle and the reference surface is no greater than 18°.

[0096] Finally, a differential current detector is manufactured according to the B-dot ring size, the B-dot size along the axis of the shielding hole 2, the position of the B-dot ring 1 and the B-dot ring surface angle.

[0097] like Figure 14 、 Figure 15 As shown, a B-dot ring body is a multi-turn coil wound with metal wire. The coil shape is variable and can be circular or rectangular. Schematic diagrams of multi-turn and single-turn B-dot ring bodies are provided. The cross-section parallel to the xy plane and located at the middle of the B-dot ring body's length along the z-axis is defined as the B-dot ring surface, and the area of the B-dot ring surface enclosed by the ring body is defined as the ring surface area. For a specific application, the design range of the ring body dimensions is first estimated according to step 1. Then, in step 2, based on the magnetic field distribution within the shielding hole 2, the dimensional constraints of the B-dot along the axis of the shielding hole 2 are determined. The y-axis dimensions of the B-dot ring body 1 are controlled to determine the structural dimensions of the B-dot ring body 1. Once the structural dimensions of the B-dot ring body 1 are determined, the position of the B-dot ring body 1 and the angle of the B-dot ring surface are constrained according to steps 3 and 4 to ensure good consistency among the multiple B-dots designed using this method.

Claims

1. A method for manufacturing a differential current detector, characterized in that: The following steps are involved: 1) Set the circuit model of B-dot; The circuit model of the B-dot includes a B-dot inductor L, an impedance Z of a signal cable (3) connected to the B-dot inductor L, and a current to be measured I o Mutual inductance M between B-dot; 2) According to the B-dot output signal amplitude u w , constraining the B-dot ring size; the B-dot ring size is the equivalent ring surface area nS: 2.1) Estimate the B-dot output signal amplitude u w for: u w =MI o / t r Where, t r is the current to be measured I o cutting edge; 2.2) Through step 2.1) w =MI o / t r , determine the B-dot ring size nS: nS=MI o / B i Where B i is the magnetic field at B-dot, and the measured current I o is proportional to; n is the number of turns of the B-dot ring (1), S is the area of the B-dot ring; 3) determining the size of the B-dot along the axis of the shielding hole (2), the position of the B-dot ring (1), and the B-dot ring angle according to the distribution of the magnetic field B inside the shielding hole (2); The size of the B-dot along the axis of the shielding hole (2) is specifically determined as follows: A1) Simulate the internal magnetic field of the shielding hole (2) B It is defined that the magnetic field B inside the shielding hole (2) is along the x-axis direction, the axis of the shielding hole (2) is along the y-axis direction, the coordinate origin o is located at the center of the outer edge of the shielding hole (2), and the -y direction represents the internal depth of the shielding hole (2); Calculate the magnetic flux dΦ in the area element in the y-axis direction y Where: a is the starting point of the area element in the y-axis direction, l y is the total length of the area element along the y-axis, d z is the width of the area element in the y-axis direction, B0 is the surface magnetic field of the shielding hole (2), and k is a constant; A2) According to the magnetic flux dΦ in the area element in the y-axis direction y Determine the total length l of the area element of B-dot along the y-axis y , obtaining the dimension along the axial direction of the shielding hole (2); The specific method for determining the position range of the B-dot ring body (1) is as follows: B1) When z=0, according to the distribution of the magnetic field B inside the shielding hole (2), under the condition of equal depth, the deviation of the magnetic field at different positions in the x-axis direction relative to the magnetic field of the shielding hole (2) axis is compared. When the magnetic field change is less than 5%, it can be obtained that the position change of the B-dot ring (1) in the x-axis direction does not exceed ±0.1d, where d is the aperture of the shielding hole; B2) When x=0, based on the distribution of the magnetic field B inside the shielding hole (2), under the condition of equal depth, the deviation of the magnetic field at different positions in the z-axis direction relative to the magnetic field of the shielding hole (2) axis is compared. When the magnetic field change is less than 5%, it can be obtained that the position change of the B-dot ring (1) in the z-axis direction does not exceed ±0.17d; B3) When the magnetic flux dΦ in the area element in the y-axis direction y is less than 8.4%, and the position change of the B-dot ring (1) in the y-axis direction does not exceed ±0.088d / k; 4) A differential current detector is manufactured according to the B-dot ring size, the B-dot size along the shield hole (2) axis, the B-dot ring (1) position and the B-dot ring surface angle.

2. The method for manufacturing a differential current detector according to claim 1, characterized in that: In step 3), the B-dot annular angle is determined as follows: When the B-dot torus is defined as perpendicular to the magnetic field at its location, the location of the B-dot torus is referred to as the reference plane, and the angle between the B-dot torus and the reference plane is referred to as the B-dot torus angle θ.

3. The method for manufacturing a differential current detector according to claim 2, characterized in that: Step A2) is specifically as follows: The size of the B-dot along the axial direction of the shielding hole (2) is less than or equal to 3d / k.

4. The method for manufacturing a differential current detector according to claim 3, characterized in that: In step 2.1), the B-dot output signal amplitude u w The value range is u w ∈(100,1000).

5. The method for manufacturing a differential current detector according to claim 4, characterized in that: In step 3, the B-dot annular surface angle θ is ≤ 18°.

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