Device and method for calibrating megaampere-level fast-rise-time pulse large-current measuring probe

Abstract

The invention discloses a device and a method for calibrating a digital megaampere-level fast-leading-edge pulse large-current measuring probe, the device comprises a large-current pulse source, a coaxial calibration loop and a load structure, and a differential ring or Rogowski coil to be calibrated is mounted at the axis of the loop along with the load structure to form a current path with extremely low inductance; the calibration device generates high-amplitude (350-500kA) and fast-front-edge (about 100ns) current pulses, the current pulses are equally divided into a plurality of equal parts capable of being accurately measured through a coaxial cage-shaped structure formed by uniformly distributing dozens of short-circuit rods in the calibration loop in the circumferential direction, and reference Rogowski coils with known scale coefficients are sleeved on the dozens of short-circuit rods. The total current is calculated by the product of the number of the short-circuiting rods and the average value of the current measured on the dozens of short-circuiting rods, and current probe calibration is achieved. The calibration loop is low in inductance, and the calibration experiment probe is high in signal-to-noise ratio; the probe is arranged in a loop along with a load structure, the distribution of a magnetic field around the probe during calibration is similar to that when fast front edge pulse large current flows through several megaamperes to dozens of megaamperes, and the calibration result is traceable.

Description

Technical Field

[0001] This invention belongs to the field of high-power pulse measurement technology, specifically relating to a calibration device and method for a high-current measurement probe with fast leading-edge pulses ranging from several megaamperes to tens of megaamperes. Background Technology

[0002] The current amplitude in the load area of ​​fast-leading high-current pulse power devices reaches megaamperes to tens of megaamperes, with a leading edge of about tens to hundreds of nanoseconds. Probes with high-caliber differential loops or Rogowski coils are commonly used for measurement.

[0003] Existing technologies mainly use pulse current sources with an amplitude of about 10kA and a leading edge of about 100ns to calibrate multi-megaampere pulse current measurement probes. Sandia National Laboratories in the United States divided a 10kA pulse current with an amplitude of about 90ns into 48 channels and fed them uniformly into a radial transmission line to achieve differential loop calibration, and calculated the calibration coefficient based on the distance between the probe and the current axis. Wei Bing, Qing Yanling, Feng Shuping, et al. published a paper in the journal High Power Laser and Particle Beams (2015, 27(7)) entitled "Probe Design and Calibration for Measuring Multi-Megaampere Pulse Currents [J]". They developed a calibration device with the same load area size as the PTS device and including a column-hole bus structure. They also divided a 10kA pulse current with an amplitude of about 90ns into 48 channels and fed them uniformly into the device to achieve calibration. The output current leading edge of the above calibration device is similar to that of the experimental current, but the amplitude differs from the experimental current by 2-3 orders of magnitude. The low signal-to-noise ratio of the probe output reduces the accuracy of the calibration results and the reliability of the extrapolation of the scale coefficient, making it difficult to trace the calibration results. All of the above methods adopt offline calibration methods, but the probe scale coefficient is related to its location, making it difficult to guarantee the equivalence between the calibration device and the load structure. Summary of the Invention

[0004] The purpose of this invention is to address the technical challenges of existing calibration devices, such as low current amplitude (difference of 2-3 orders of magnitude from the experimental current), slow leading edge, and difficulty in tracing the source; low signal-to-noise ratio of the output of megaampere fast-pulse high-current measurement probes, susceptibility to interference, low accuracy of calibration results, and low reliability of scale coefficient extrapolation; and difficulty in ensuring the equivalence of the calibration device and the load structure during offline calibration. This invention proposes a calibration device and method for megaampere to tens of megaampere fast-leading-edge pulse high-current measurement probes. The calibration device feeds high-amplitude, fast-leading-edge current pulses into the load structure, achieving online calibration of the probe. The feed current is uniform, and the calibration results are traceable. The proposed calibration method is easy to implement and can improve the accuracy and reliability of megaampere fast-pulse high-current measurement probe calibration, possessing significant application value in fast-leading-edge high-current pulse power devices.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0006] A calibration device for a high-current measuring probe with a fast-rising-edge pulse at the megaampere level includes a high-current pulse source, a coaxial calibration circuit, and a load structure. The differential loop or Rogowski coil to be calibrated is first installed on the load structure, and then installed in the calibration circuit along with the load structure, forming a current path with extremely low inductance. The calibration device generates a high-amplitude (350kA-500kA) current pulse with a fast-rising-edge (tens of ns) pulse. This pulse is divided into several equal and accurately measurable portions by a cage-like structure formed by dozens of short-circuit rods evenly distributed circumferentially in the coaxial calibration circuit. A reference Rogowski coil is fitted on several short-circuit rods, and the calibration coefficient of the reference Rogowski coil is known. The total current is calculated by multiplying the number of short-circuit rods by the average current measured on the dozens of short-circuit rods, thus achieving current probe calibration. The low inductance of the coaxial calibration circuit can increase the amplitude of the feed current, thereby improving the signal-to-noise ratio of the calibration probe. The probe and the load structure are set together in the circuit, and the magnetic field distribution around the probe during calibration is similar to that when a high-current pulse with a fast-rising edge of several megaamperes to tens of megaamperes flows through it. This calibration method is equivalent to online calibration, and the calibration results are traceable.

[0007] When the single-stage linear transformer driver (LTD) module is used as a high-current pulse source, the calibration device structure mainly includes: LTD module, coaxial calibration circuit, and load structure. The current probe to be calibrated is installed on the load structure, the load structure is placed at the axis of the calibration circuit, and the gap distance is adjusted to make the inner and outer conductors of the load structure coaxial. The calibration circuit is installed on the secondary side of the LTD module to form a closed current path.

[0008] The coaxial calibration circuit structure mainly includes: a ground electrode, short-circuit rods, insulating rods, a reference Rogowski coil, insulating gaskets, a return electrode, a feed electrode, an extension flange, a sealing flange, a first cable adapter plate, a second cable adapter plate, an air pipe interface, and a sealing gasket ring. Dozens of short-circuit rods are installed on the ground electrode, forming a cage-like structure. The reference Rogowski coil is sleeved on the short-circuit rods and protected by insulating gaskets. The coil signal is led out to the outside of the cavity through the second cable adapter plate. The return electrode is connected to the short-circuit rods, and the feed electrode is supported by several insulating rods evenly distributed inside the short-circuit rods, forming a radial transmission line. The probe to be calibrated is installed along with the load structure at the axis of the coaxial calibration circuit. The above structure is installed on the secondary side of the LTD module, connecting the feed electrode and the high-voltage electrode of the LTD module. The ground electrode is connected to the ground electrode of the LTD module via the sealing gasket ring, forming a closed current path. The extension flange is connected to the feed electrode to ensure the internal space of the cavity formed by the coaxial calibration circuit and the LTD secondary; the sealing flange is used to achieve internal sealing of the cavity, and the signal of the probe to be calibrated is led out to the outside of the cavity through the first cable adapter plate; the gas pipe interface is used for vacuuming and injecting sulfur hexafluoride into the cavity.

[0009] A calibration method for a high-current measuring probe with a fast leading-edge pulse at the megaampere level, wherein the calibration device is fed with a current pulse, includes the following steps:

[0010] 1) After the calibration device is installed, confirm the airtightness of the cavity formed by the coaxial calibration circuit and the secondary winding of the LTD module, and that the signals from each probe and the reference Rogowski coil have been led out from the cavity;

[0011] 2) The air inside the cavity is removed by a vacuum pump, and sulfur hexafluoride is injected into the cavity to improve the insulation strength inside the cavity;

[0012] 3) Fill the gas switch in the LTD module with zero-level air to maintain insulation strength; use an external high-voltage DC power supply to charge the primary capacitor of the module until the set voltage is reached;

[0013] 4) Inject an electrical pulse or vent the switch to discharge, causing the trigger branch to discharge, thereby synchronously triggering all main branches in the module, generating a pulse current with an amplitude of several hundred kA and a leading edge of about 100 ns, which is then injected into the load structure through the coaxial calibration circuit.

[0014] 5) After completing one test, the external high-voltage DC power supply should be grounded;

[0015] 6) The waveforms of the current probe to be calibrated and the reference Rogowski coil are acquired by the data acquisition system, and the probe calibration coefficient is calculated;

[0016] 7) Repeat steps 2) to 6) to conduct multiple repeated experiments to reduce the uncertainty of the probe calibration coefficient.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] 1. The offline calibration method of the present invention increases the current amplitude from 10kA to several hundredkA, improves the signal-to-noise ratio of the probe in the calibration experiment, and enhances the accuracy of the calibration results and the reliability of the extrapolation of the scale coefficient.

[0019] 2. By using a coaxial cage structure, the large current of hundreds of kA fast pulses is divided into several equal and accurately measurable parts. The total current can be calculated, and the probe calibration results can be traced back to the reference Rogowski coil.

[0020] 3. During calibration, the magnetic field distribution around the probe is similar to that when a large current of several megaamperes to tens of megaamperes flows through it. The calibration method is equivalent to online calibration, and the obtained scale coefficients can be directly used for actual measurements without conversion.

[0021] 4. The probe is set in the loop along with the load structure, eliminating the error introduced by probe disassembly and assembly after offline calibration. Attached Figure Description

[0022] Figure 1This is a schematic diagram of the calibration device structure of an embodiment of the calibration device and method for a high-current measurement probe with a fast leading-edge pulse of several megaamperes according to the present invention;

[0023] Figure 2 This is a schematic diagram of the calibration circuit structure in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram comparing the output signal of the differential loop after being restored by the integrator with the total current signal in an embodiment of the present invention.

[0025] The annotations in the attached figures are explained as follows:

[0026] 1-LTD module, 2-calibration circuit, 3-load structure, 4-LTD module high voltage electrode, 5-LTD module ground electrode, 6-ground electrode, 7-short circuit rod, 8-insulating rod, 9-reference Rogowski coil, 10-insulating gasket, 11-return electrode, 12-feed electrode, 13-extension flange, 14-sealing flange, 15-first cable adapter plate, 16-second cable adapter plate, 17-air pipe interface, 18-sealing gasket ring. Detailed Implementation

[0027] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] like Figure 1As shown, this embodiment provides a calibration device and method for a high-current measurement probe with a fast leading-edge pulse of several megaamperes. It includes a high-current pulse source, a coaxial calibration circuit 2, and a load structure 3. The differential loop or Rogowski coil to be calibrated is first installed on the load structure 3, and then installed in the calibration circuit along with the load structure 3, forming a current path with extremely low inductance. The calibration device generates a high-amplitude (350kA - 500kA) current pulse with a fast leading edge (approximately 100ns). The coaxial calibration circuit 2 uses 24 short-circuit rods 7 evenly distributed circumferentially to form a cage-like structure. Two Pearson 4997 Rogowski coils are respectively set on two short-circuit rods 7 as reference Rogowski coils 9, ensuring that the current of the short-circuit rods 7 is within the measurable range. The scale factor of the reference Rogowski coil 9 is known. Twelve insulating rods 8 are evenly arranged inside the short-circuit rods 7 to support the feed electrode 12, with a distance of 1cm between it and the return electrode 11. The load structure 3 is located at the circuit axis, with four differential loops evenly arranged circumferentially. Before the calibration experiment, the air inside the calibration device chamber is evacuated using a vacuum pump, and sulfur hexafluoride at 0MPa - 0.1MPa (gauge pressure) is injected. The gas switch inside LTD module 1 is filled with zero-level air. The total current is calculated by multiplying the number of short-circuit rods 7 by the average current measured on dozens of short-circuit rods 7, thus achieving current probe calibration. The coaxial calibration circuit 2 has low inductance, which can increase the amplitude of the feed current, thereby improving the signal-to-noise ratio of the calibration probe. The probe is placed in the circuit along with the load structure 3, and the magnetic field distribution around the probe during calibration is similar to that when a large current of several megaamperes to tens of megaamperes flows through it. This calibration method is equivalent to online calibration, and the calibration results are traceable.

[0029] When the single-stage LTD module 1 is used as a high-current pulse source, the calibration device structure mainly includes: LTD module 1, coaxial calibration circuit 2, and load structure 3. The current probe to be calibrated is installed on the load structure 3. The load structure 3 is placed at the axis of the coaxial calibration circuit 2. The gap distance is adjusted to make the inner and outer conductors of the load structure 3 coaxial. The coaxial calibration circuit 2 is installed on the secondary of LTD module 1, thus forming a closed current path.

[0030] like Figure 2As shown, the calibration circuit structure mainly includes: ground electrode 6, short-circuit rod 7, insulating rod 8, reference Rogowski coil 9, insulating gasket 10, return electrode 11, feed electrode 12, extension flange 13, sealing flange 14, first cable adapter plate 15, second cable adapter plate 16, air pipe interface 17, and sealing gasket ring 18. Dozens of short-circuit rods 7 are installed on the ground electrode 6, forming a cage-like structure. The reference Rogowski coil 9 is sleeved on the short-circuit rod 7 and protected by the insulating gasket 10. The coil signal is led out to the outside of the cavity through the second cable adapter plate 16. The return electrode 11 is connected to the short-circuit rod 7, and the feed electrode 12 is supported by several insulating rods 8 evenly distributed inside the short-circuit rod 7, forming a radial transmission line. The probe to be calibrated is installed along the axis of the coaxial calibration circuit 2 with the load structure 3. This structure is then installed on the secondary side of the LTD module 1, connecting the feed electrode 12 and the high-voltage electrode 4 of the LTD module. The ground electrode 6 is connected to the ground electrode 5 of the LTD module via a sealing gasket 18, forming a closed current path: LTD module high-voltage electrode 4 - feed electrode 12 - load structure 3 - return electrode 11 - short-circuit rod 7 - ground electrode 6 - sealing gasket 18 - LTD module ground electrode 5. An extension flange 13 is connected to the feed electrode 12 to ensure the internal space of the cavity formed by the coaxial calibration circuit 2 and the secondary side of the LTD module 1. A sealing flange 14 is used to seal the inside of the cavity. The signal from the probe to be calibrated is led out to the outside of the cavity via the first cable adapter plate 15. An air pipe interface 17 is used for evacuating the cavity and injecting sulfur hexafluoride.

[0031] like Figure 3 As shown, in the calibration experiment, after LTD module 1 was charged to ±60kV, it was triggered to discharge. The two reference Rogowski coils 9 in the calibration device measured a current of 17kA, and the total current was calculated to be 408kA. The 10%-90% leading edge was 90ns.

[0032] A calibration method for a high-current measuring probe with a fast leading-edge pulse at the megaampere level, wherein the calibration device is fed with a current pulse, includes the following steps:

[0033] 1) After the calibration device is installed, confirm the airtightness of the cavity formed by the coaxial calibration circuit 2 and the secondary winding of the LTD module 1, and that the signals from each probe and the reference Rogowski coil 9 have been led out from the cavity;

[0034] 2) The air inside the cavity is removed by a vacuum pump, and sulfur hexafluoride is injected into the cavity to improve the insulation strength inside the cavity;

[0035] 3) Fill the gas switch in LTD module 1 with zero-level air to maintain insulation strength; use an external high-voltage DC power supply to charge the primary capacitor of the module until the set voltage is reached;

[0036] 4) Inject an electrical pulse or vent the switch to discharge, causing the trigger branch to discharge, thereby synchronously triggering all main branches in the module, generating a pulse current with an amplitude of several hundred kA and a leading edge of about 100 ns, which is then injected into the load structure 3 through the coaxial calibration circuit 2.

[0037] 5) After completing one test, the external high-voltage DC power supply should be grounded;

[0038] 6) The waveforms of the current probe to be calibrated and the reference Rogowski coil 9 are acquired by the data acquisition system, and the probe calibration coefficient is calculated;

[0039] 7) Repeat steps 2) to 6) to conduct multiple repeated experiments to reduce the uncertainty of the probe calibration coefficient.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A calibration device for a high-current measurement probe with a fast leading-edge pulse of several megaamperes, comprising a high-current pulse source, a coaxial calibration circuit, and a load structure, characterized in that: The differential loop or Rogowski coil to be calibrated is first installed on the load structure, and then installed in the calibration circuit along with the load structure, forming a current path with extremely low inductance. The calibration device generates a current pulse with an amplitude of 350kA-500kA and a leading edge of tens of ns. Through the cage structure in the coaxial calibration circuit, it is divided into several equal and accurately measured parts. A reference Rogowski coil is fitted on the short-circuit rod. The scale factor of the reference Rogowski coil is known. The total current amplitude is obtained by multiplying the number of short-circuit rods by the average current measured on the short-circuit rods, thus realizing the calibration of the current probe.

2. The calibration device for a megaampere-level fast-leading-edge pulse high-current measurement probe according to claim 1, characterized in that: The coaxial calibration circuit structure includes: a ground electrode, short-circuit rods, insulating rods, a reference Rogowski coil, insulating gaskets, a return electrode, a feed electrode, an extension flange, a sealing flange, a first cable adapter plate, a second cable adapter plate, an air pipe interface, and a sealing gasket ring. Dozens of short-circuit rods are installed on the ground electrode, forming a cage-like structure. The reference Rogowski coil is sleeved on the short-circuit rods, and an insulating gasket is used to protect the reference Rogowski coil. The coil signal is led out to the outside of the cavity through the second cable adapter plate. The return electrode is connected to the short-circuit rods, and the feed electrode is supported by several insulating rods evenly distributed inside the short-circuit rods, forming a radial transmission line. The probe to be calibrated and the load structure are installed at the axis of the coaxial calibration circuit, connecting the feed electrode and the high-voltage electrode of the LTD module. The ground electrode is connected to the ground electrode of the LTD module through the sealing gasket ring, forming a closed current path, namely: LTD module high-voltage electrode - feed electrode - load structure - return electrode - short-circuit rod - ground electrode - sealing gasket ring - The LTD module ground electrode; the extension flange connects to the feed electrode to ensure that the coaxial calibration circuit and the LTD secondary form the internal space of the cavity; the sealing flange achieves internal sealing of the cavity, and the signal of the probe to be calibrated is led out to the outside of the cavity through the first cable adapter plate; the endotracheal interface is used for vacuuming and injecting sulfur hexafluoride into the cavity.

3. A calibration device for a megaampere-level fast-leading-edge pulse high-current measuring probe according to claim 1 or 2, characterized in that: The coaxial calibration circuit uses multiple short-circuit rods evenly distributed around the circumference to form a cage-like structure. Reference Rogowski coils are set on the short-circuit rods to ensure that the short-circuit rod current is within the measurable range. The scale factor of the reference Rogowski coils is known. Multiple insulating rods are evenly arranged inside the short-circuit rods to support the feed electrode. The load structure is set at the circuit axis, and multiple differentiating rings are evenly arranged around the circumference. Before the calibration experiment, the air in the calibration device cavity is evacuated by a vacuum pump and sulfur hexafluoride is injected.

4. The calibration device for a high-current measurement probe with a fast leading-edge pulse at the megaampere level according to claim 1, characterized in that: The probe and load structure are set in the loop. During calibration, the magnetic field distribution around the probe is similar to that when a large current of several megaamperes to tens of megaamperes flows through a fast-leading pulse. The calibration method is equivalent to online calibration, and the obtained scale coefficients are directly used for actual measurements. The calibration results can be traced back to the reference Rogowski coil.

5. A calibration method for a megaampere-level fast-rising-edge pulse high-current measuring probe, based on the calibration device for a megaampere-level fast-rising-edge pulse high-current measuring probe as described in claims 1 to 4, characterized in that: The calibration device is fed a current pulse, including the following steps: Step 1: After the calibration device is installed, confirm the airtightness of the cavity formed by the coaxial calibration circuit and the secondary winding of the LTD module, and that the signals from each probe and the reference Rogowski coil have been led out from the cavity; Step 2: Remove the air from the cavity using a vacuum pump and inject sulfur hexafluoride into the cavity to improve the insulation strength of the cavity; Step 3: Fill the gas switch inside the LTD module with zero-level air to maintain insulation strength; use an external high-voltage DC power supply to charge the primary capacitor of the LTD module to reach the set voltage; Step 4: Inject an electrical pulse or vent the switch to discharge the trigger branch, thereby synchronously triggering all main branches in the LTD module to generate a pulse current with an amplitude of hundreds of kA and a leading edge of tens of ns, which is then injected into the load structure through the coaxial calibration circuit. Step 5: After completing one test, ground the external high-voltage DC power supply; Step 6: The data acquisition system acquires the waveforms of the current probe to be calibrated and the reference Rogowski coil, and calculates the probe calibration coefficient.

6. The calibration method for a high-current measurement probe with a fast leading-edge pulse at the megaampere level according to claim 5, characterized in that: It also includes step 7: Repeat steps 2 to 6 to conduct multiple repeated experiments to reduce the uncertainty of the probe calibration coefficient.

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