Single-layer tubular resistor structure with fast response time coaxial tubular shunt

Abstract

A fast response time coaxial tube shunt with a single-layer tubular resistor structure is provided. A resistor tube is formed on the outer surface of an insulating tube. An insulating coating is provided on the outer surface of the resistor tube so that the outer conductive tube and the resistor tube can be designed to be as close as possible. When a large pulse current passes through, since the thickness of the resistor tube can be controlled to the μm level, the response time of the coaxial tube shunt can theoretically be in the ps level. At the same time, since the currents passing through the outer conductive tube and the resistor tube are equal in magnitude and opposite in direction, and the distance between the two is extremely close, the residual inductance of the coaxial tube shunt can be made extremely small, which greatly reduces the overshoot phenomenon of pulse current measurement and improves the accuracy of fast rise time pulse current measurement.

Description

Technical Field

[0001] The invention relates to a high-performance current sensor gap for pulse current measurement or verification, and in particular to a fast response time coaxial tube type shunt with a single-layer tubular resistor structure based on a jetting process. Background Art

[0002] Lightning discharge is a natural phenomenon that poses serious hazards to power transmission lines, buildings, communication base stations, etc. The lightning discharge process generally forms a pulse current of milliseconds and microseconds. With the research and increasingly widespread application of nuclear simulation technology, intense pulse laser, high-power microwave, electromagnetic emission simulation and high-temperature plasma technology, higher and higher requirements are placed on the measurement of nanosecond pulse large current.

[0003] In order to study the effects of lightning discharges and pulses and the corresponding protection effectiveness, simulated pulse current devices are widely used in laboratory research. Establishing the intrinsic correlation mechanism between pulse power supply and load through the electrical parameters of pulse current is the most conventional research method. Therefore, accurate measurement of pulse current is an important foundation and basis for all research.

[0004] Commonly used pulse current measurement sensors include electromagnetic induction Rogowski coils, magneto-optical induction current sensors and shunts, etc. The shunts are divided into folded shunts, two-wire winding shunts, coaxial tube shunts, disc shunts, etc. according to different structural forms. From the measurement principle of pulse current, the shunt is essentially a small resistor, which is directly electrically connected to the analog pulse current device. The measured pulse current parameters (including peak value, rise time, duration, etc.) are calculated through the relationship between the voltage at both ends and the shunt resistance; the electromagnetic induction Rogowski coil and magneto-optical induction current sensor are obtained through electromagnetic or magneto-optical induction and subsequent signal processing to obtain the electrical parameters of the measured pulse current. Therefore, shunts are usually used as standard current sensors to calibrate other types of current sensors, but the performance of shunts is affected by the manufacturing process of the shunts. The folded and two-wire winding shunts have large residual inductance, which makes the measured current have a large overshoot in the wavefront; the disc shunt uses the inner and outer edges as the input, output and measurement ends respectively. The pulse current can flow radially and evenly in the thin resistor disk and is less affected by stray inductance. However, when measuring large pulse currents, the temperature rise between the inner and outer edges is quite different. Due to the limitation of heat capacity, it is not suitable for measuring large-value pulse currents; in comparison, the coaxial tube shunt consists of two coaxial cylinders inside and outside. The measured pulse current can flow into the inner cylinder of the resistor and flow out of the shielded outer cylinder (or flow in the opposite direction). The magnetic field generated by the measured pulse current is almost limited between the inner and outer cylinders. There is no magnetic field inside the inner cylinder of the resistor, and the stray inductance can be made very small. Its upper frequency limit is limited by the skin effect. However, the geometric structure of the coaxial shunt is symmetrical, and the uneven current distribution caused by the skin effect can be calculated and compensated theoretically. Therefore, the coaxial tube type is a relatively ideal sensor and can be made into a high-performance standard current sensor.

[0005] With the development of nuclear simulation technology and pulse plasma technology, the demand for high-performance pulse shunts in the nanosecond or even picosecond range is increasing. In particular, for metering shunts, their response time must be much higher than that of the sensor being measured, at least 0.2 times the response time of the sensor being measured. That is to say, if the response time of the measured signal or the sensor being calibrated is 10ns, the response time of the sensor must be at least 2ns or shorter. At present, there is still a problem with coaxial tube shunts, especially coaxial tube pulse shunts with fast response time: (1) Due to the influence of the thickness of the metal alloy film of the resistor body, the response time of the pulse shunt is difficult to achieve 1ns; (2) Due to the limitation of the gap distance between the inner resistor body circular tube and the conductive outer tube of the shunt, the residual inductance of the coaxial tube shunt cannot be made too small, which causes the pulse current waveform measured by the pulse shunt to be distorted. Therefore, the performance indicators of pulse shunts need to be improved. Summary of the invention

[0006] The purpose of the present invention is to provide a fast response time coaxial tube shunt with a single-layer tubular resistor structure, which can have a fast response time and high measurement accuracy in nanosecond pulse large current measurement. The device can be used for measuring nanosecond pulse current signals, and can also be used as a standard pulse shunt for metrological verification to calibrate the bandwidth of other types of pulse current sensors.

[0007] To achieve the above object, the technical solution adopted by the present invention is: comprising an outer conductive round tube and an insulating round tube coaxially installed therein, wherein the outer wall of the insulating round tube is provided with a resistor body round tube with an insulating coating;

[0008] The upper and lower ends of the insulating circular tube are electrically connected to the upper and lower metal end caps respectively, the upper metal end cap is provided with an insulating circular ring connected to the upper end of the outer conductive circular tube, the center of the insulating circular ring is provided with a current injection electrode, and the lower end of the current injection electrode is connected to the upper metal end cap;

[0009] The lower metal end cap is connected to the lower end of the outer conductive round tube, a coaxial connector is arranged at the center of the lower metal end cap, and the core wire of the coaxial connector is connected to the current injection electrode through a wire;

[0010] The outer conductive round tube is also provided with a return end connected to the lower metal end cover.

[0011] The resistor body round tube is sprayed on the outer surface of the insulating round tube by using a spraying process.

[0012] The thickness of the resistor tube is 5 μm-200 μm.

[0013] The resistor body round tube is made of Kama alloy, Ni-Cr alloy or Constantan alloy.

[0014] The thickness of the insulating coating on the resistor tube is 20 μm-100 μm.

[0015] The gap between the inner wall of the outer conductive circular tube and the outer wall of the resistor circular tube is 200 μm-1 mm.

[0016] The insulating round tube is a ceramic round tube, and its two end faces are metallized, the thickness of the metallized layer is 20-100 μm, and the height of the metallized outer edge of the outer surface of both ends of the insulating round tube is 5-8 mm, and the thickness is 10-100 μm.

[0017] The upper metal end cover is a T-shaped structure. The outer diameter of the lower end of the upper metal end cover is the same as the inner diameter of the insulating round tube, and is embedded in the insulating round tube. The embedding depth is 5-10mm. The outer diameter of the upper end of the upper metal end cover is the same as the outer diameter of the insulating round tube.

[0018] The lower metal end cap is an inverted T-shaped structure, the upper end outer diameter is the same as the inner diameter of the insulating round tube, and is embedded in the insulating round tube with an embedding depth of 5-10mm, the lower end outer diameter is the same as the inner diameter of the outer conductive round tube, and is tightly connected to the outer conductive round tube through a threaded buckle.

[0019] The upper end of the outer conductive tube has a turned-out outer edge, the insulating ring is connected to the outer conductive tube via a threaded connection, and the return end of the current is arranged on the turned-out outer edge of the outer conductive tube.

[0020] The present invention forms a resistor body round tube on the outer surface of an insulating round tube, and an insulating coating is arranged on the outer surface of the resistor body round tube, so that the outer conductive round tube and the resistor body round tube can be designed to be as close as possible. When a large pulse current passes through, since the thickness of the resistor body round tube can be controlled to the order of μm, it is ensured that the response time of the coaxial tube type shunt can theoretically be in the order of ps; at the same time, since the currents passing through the outer conductive round tube and the resistor body round tube are equal in magnitude and opposite in direction, and the distance between the two is extremely close, the residual inductance of the coaxial tube type shunt can be made extremely small, which greatly reduces the overshoot phenomenon of pulse current measurement and improves the accuracy of fast rise time pulse current measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0022] In the figure, there are outer conductive tube 1, resistor tube 2, current injection electrode 3, voltage lead wire 4, voltage coaxial connector 5, upper metal end cap 6, lower metal end cap 7, insulating tube 8, insulating ring 9, nut 10, return end 11, nut 12. DETAILED DESCRIPTION

[0023] The structural principle and working principle of the present invention are further described in detail below with reference to the accompanying drawings.

[0024] See also Figure 1The present invention comprises an outer conductive tube 1, a resistor tube 2, a current injection electrode 3, a voltage lead wire 4, a voltage coaxial connector 5, an upper metal end cap 6, a lower metal end cap 7, and an insulating tube 8. The insulating tube 8 is coaxially installed in the outer conductor tube 1, and the resistor tube 2 is coaxially installed on the outer surface of the insulating tube 8. The resistor tube 2 is formed by spraying a metal alloy on the outer surface of the insulating tube 8 by a spraying mechanism. The thickness of the alloy metal layer of the resistor tube is controlled to be 5μm-200μm, and the metal alloy is kama alloy, nickel-chromium alloy or constantan alloy. The outer surface of the resistor tube 2 is sprayed with an insulating coating with a thickness of 20μm-100μm or a high-temperature insulating material with a thickness of 20μm-100μm. Since the outer surface of the resistor tube 2 is sprayed with an insulating coating, the gap between the inner wall of the outer conductive tube 1 and the outer wall of the resistor tube 2 can be designed to be as close as possible, and the gap is controlled to be 0.2-1mm.

[0025] The insulating tube 8 of the present invention is a ceramic tube, and its two end faces are metallized, and the thickness of the metallized film is 20-100 μm, and the outer edges of the outer surfaces of both ends of the insulating tube 8 are also metallized at a height of 5-8 mm, and the thickness of the metallized film is 10-100 μm, so that the sprayed metal layer of the sprayed resistor tube 2 has good electrical connection. The metallized end faces at both ends of the insulating tube 8 are tightly electrically connected to the upper metal end cap 6 and the lower metal end cap 7, respectively. The upper metal end cover 6 has a "T"-shaped structure. The lower end of the upper metal end cover 6 is embedded in the insulating circular tube 8 with an embedding depth of 5-10 mm. The diameter of the upper surface of the upper metal end cover 6 is consistent with the outer diameter of the insulating circular tube 8, and is tightly and reliably electrically connected to the metallized layer on the upper end surface of the insulating circular tube 8; the connection between the lower metal end cover 7 and the lower end surface of the insulating circular tube 8 is the same as the connection between the upper metal end cover 6 and the upper end surface of the insulating circular tube 8, and the lower metal end cover 7 is tightly connected to the lower end of the outer conductive circular tube 1 through a threaded connection. The lower metal end cover 7 can also be designed as an integrated whole with the outer conductive circular tube 1.

[0026] See also Figure 1The upper metal end cap 6 of the present invention has an insulating ring 9, and the outer conductive tube 1 has an outer edge that is turned out, and the width of the outer edge is 15-25mm and the thickness is 15-20mm. The insulating ring 9 is connected to the outer edge of the outer conductive tube 1 by a threaded connection. The current injection electrode 3 passes through the insulating ring 9 and is installed on the metal end cap 6 by a threaded connection and is fixed by a nut 10, which is used to be electrically connected to the pulse current circuit to be measured. The return end 11 of the current is set on the turned-out outer edge of the outer conductive tube and is electrically connected to the pulse current circuit through a nut 12. The current output by the pulse current generating device flows in from the current injection electrode 3, and a pulse current path is formed through the lower metal end cap 7-outer conductive tube 1-return end 11. Since the current in the resistor tube 2 is equal to the current in the outer conductive tube 1 in magnitude and opposite in direction, and the gap between the resistor tube 2 and the outer conductive tube 1 is extremely close, the coaxial tube shunt has an extremely low residual inductance, which greatly improves the waveform accuracy of the pulse current measurement.

[0027] See also Figure 1 The lower metal end cover 7 of the present invention has a circular hole for installing the voltage coaxial connector 5. The metal shell of the voltage coaxial connector 5 is tightly electrically connected to the lower metal end cover 7. The core wire of the voltage coaxial connector 5 is connected to the current injection electrode 3 through the voltage lead-out wire 4.

[0028] The significant features of the present invention that are different from the existing coaxial tube shunt are: first, a spraying process is used to spray or coat metal alloys and insulating materials on the outer surface of an insulating circular tube to form an alloy-insulating multilayer resistor circular tube. The thickness of the alloy layer can be controlled by the spraying process. When the thickness of the resistor circular tube is controlled to be several μm, the response time of the coaxial tube shunt can reach the order of 1ns, and steep pulse currents with a rise time of more than 10ns can be measured; second, high-temperature insulating material is sprayed on the outer surface of the alloy-insulating multilayer resistor circular tube, so that the gap distance between the resistor circular tube and the outer conductive circular tube can be controlled to be extremely close, so that the residual inductance of the coaxial tube shunt can be made extremely small, greatly reducing the overshoot phenomenon of pulse current measurement and improving the accuracy of fast rise time pulse current measurement.

Claims

1. A fast response time coaxial tube shunt with a single-layer tubular resistor structure, characterized in that: It comprises an outer conductive circular tube (1) and an insulating circular tube (8) coaxially installed therein, wherein the outer wall of the insulating circular tube (8) is provided with a resistor circular tube (2) with an insulating coating having a thickness of 5 μm to 200 μm, and the gap between the inner wall of the outer conductive circular tube (1) and the outer wall of the resistor circular tube (2) is 200 μm to 1 mm; The resistor body round tube (2) is sprayed onto the outer surface of the insulating round tube (8) by a spraying process; The resistor tube is made of Kama alloy, NiCr alloy or Constantan alloy; The thickness of the insulating coating on the resistor tube (2) is 20 μm-100 μm; The upper and lower ends of the insulating circular tube (8) are electrically connected to the upper and lower metal end caps (6, 7) respectively; the upper metal end cap (6) is provided with an insulating circular ring (9) connected to the upper end of the outer conductive circular tube (1); a current injection electrode (3) is installed at the center of the insulating circular ring (9); the lower end of the current injection electrode (3) is connected to the upper metal end cap (6); The lower metal end cover (7) is connected to the lower end of the outer conductive round tube (1), a coaxial connector (5) is arranged at the center of the lower metal end cover (7), and the core wire of the coaxial connector (5) is connected to the current injection electrode (3) through a wire (4); The outer conductive circular tube (1) is also provided with a return end (11) connected to the lower metal end cover (7).

2. The fast response time coaxial tube shunt of the single-layer tubular resistor structure according to claim 1, characterized in that: The insulating round tube (8) is a ceramic round tube, and its two end faces are metallized. The thickness of the metallized layer is 20-100 μm, and the height of the metallized outer edge of the outer surface of both ends of the insulating round tube is 5-8 mm and the thickness is 10-100 μm.

3. The fast response time coaxial tubular shunt of the single-layer tubular resistor structure according to claim 1, characterized in that: The upper metal end cover (6) is a T-shaped structure. The outer diameter of the lower end of the upper metal end cover (6) is the same as the inner diameter of the insulating round tube (8), and is embedded in the insulating round tube (8). The embedding depth is 5-10 mm. The outer diameter of the upper end of the upper metal end cover (6) is the same as the outer diameter of the insulating round tube (8).

4. The fast response time coaxial tube shunt of the single-layer tubular resistor structure according to claim 1, characterized in that: The lower metal end cover (7) is an inverted T-shaped structure, the outer diameter of the upper end is the same as the inner diameter of the insulating round tube (8), and is embedded in the insulating round tube (8) with an embedding depth of 5-10 mm, and the outer diameter of the lower end is the same as the inner diameter of the outer conductive round tube (1), and is tightly connected to the outer conductive round tube (1) through a thread.

5. The fast response time coaxial tube shunt of the single-layer tubular resistor structure according to claim 1, characterized in that: The upper end of the outer conductive tube (1) has a protruding outer edge, the insulating ring (9) is connected to the outer conductive tube (1) via a threaded connection, and the current return end (11) is arranged on the protruding outer edge of the outer conductive tube (1).

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