Fast Response Time Coaxial Tube Shunt with Alloy-Insulator Multilayer Resistor Structure

Abstract

A fast-response-time coaxial tube shunt with an alloy-insulating multi-layer resistor structure. In the present invention, a multi-layer resistor circular tube formed by a metal alloy layer and an insulating layer is sprayed on the outer surface of an insulating circular tube. By spraying or coating a high-temperature insulating layer on the outer surface of the alloy-insulating multi-layer resistor circular tube, the outer conductive circular tube and the alloy-insulating multi-layer resistor circular tube can be designed to be as close as possible. When a pulsed large current passes through, since the thickness of each alloy layer of the resistor circular tube fabricated by the spraying process can be controlled to the μm order of magnitude, it is ensured that the response time of the coaxial tube shunt can be theoretically as fast as possible. At the same time, since the magnitudes of the currents passing through the outer conductive circular tube and the resistor circular tube are equal and the directions are opposite, and the distance between them is extremely close, the residual inductance of the coaxial tube shunt can be made extremely small, greatly reducing the overshoot phenomenon in pulsed current measurement and improving the accuracy of pulsed current measurement with a fast rise time.

Description

Technical Field

[0001] The present invention relates to a high-performance current sensor gap for pulsed current measurement or calibration, and particularly to a fast-response time coaxial tube shunt based on an alloy-insulating multi-layer resistor structure by a spraying process. Background Art

[0002] Lightning discharge is a natural phenomenon that causes serious harm to power transmission lines, buildings, communication base stations, etc. The lightning discharge process generally forms pulsed currents in the millisecond and microsecond ranges. With the research on nuclear simulation technology, high-power pulsed lasers, high-power microwaves, electromagnetic emission simulation, and high-temperature plasma technology and their increasingly wide application requirements, higher and higher requirements are also put forward for the measurement of nanosecond pulsed high currents.

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

[0004] Commonly used measurement sensors for pulsed current include Rogowski coils based on electromagnetic induction, current sensors based on magneto-optical induction, and shunts, etc. Shunts are further divided into folded shunts, double-wire wound shunts, coaxial tube shunts, disk shunts, etc. according to different structural forms. In terms of the measurement principle of pulsed current, a shunt is essentially a small resistor, directly electrically connected in an analog pulsed current device, and the measured pulsed current parameters (including peak value, rise time, duration, etc.) are calculated through the relationship between the voltage across its two ends and the shunt resistance value; while Rogowski coils based on electromagnetic induction and current sensors based on magneto-optical induction both obtain the electrical parameters of the measured pulsed current through electromagnetic or magneto-optical induction and subsequent signal processing. Therefore, shunts are usually used as standard current sensors to calibrate other types of current sensors. However, the performance of shunts is affected by the manufacturing process of shunts. For folded shunts and double-wire wound shunts, due to the large residual inductance, there is a large overshoot in the wavefront of the measured current; for disk shunts, the inner and outer edges are used as the input end, output end, and measurement end respectively, and the pulsed current can flow radially uniformly in the thin resistance disk, being less affected by stray inductance. However, when measuring large pulsed currents, the temperature rise difference between the inner and outer edges is relatively large, and due to the limitation of heat capacity, it is not suitable for measuring pulsed currents with large amplitudes; in contrast, a coaxial tube shunt consists of two coaxial cylinders inside and outside. The measured pulsed current can flow into the inner cylinder of the resistor body and out of the shielding outer cylinder (or vice versa). The magnetic field generated by the measured pulsed current is almost all restricted between the inner and outer cylinders, and there is no magnetic field inside the inner cylinder of the resistor body, and the stray inductance can be made very small. Its upper limit frequency is limited by the skin effect. However, the geometric structure of the coaxial tube shunt is symmetric, and the non-uniform current distribution caused by the skin effect can be calculated theoretically and compensated. Therefore, the coaxial tube shunt is an ideal sensor and can be made into a high-performance standard current sensor.

[0005] With the development of nuclear simulation technology and pulsed plasma technology, the demand for high-performance pulsed shunts in the nanosecond or even picosecond range is increasing. Especially for shunts used in metrology, their response time should be much higher than that of the measured sensor, at least 0.2 times the response time of the measured sensor. That is to say, if the response time of the measured signal or the calibrated sensor is 10 ns, then the response time of the sensor should be at least 2 ns or shorter. Currently, there is still a problem with coaxial tube shunts, especially coaxial tube pulsed shunts with fast response times: (1) Due to the influence of the thickness of the metal alloy thin film of the resistor body, it is difficult for the response time of the pulsed shunt to reach 1 ns; (2) Due to the limitation of the gap distance between the inner resistor body tube and the conductive outer tube of the shunt, the residual inductance of the coaxial tube shunt cannot be made too small, resulting in distortion of the pulsed current waveform measured by the pulsed shunt. Therefore, the performance indicators of pulsed shunts still need to be improved. Summary of the Invention

[0006] The object of the present invention is to provide a fast-response time coaxial tube shunt with an alloy-insulating multi-layer resistor structure that has a fast response time and high measurement accuracy in the measurement of nanosecond pulsed high currents. It can be used for the measurement of nanosecond pulsed current signals and can also be used as a standard pulsed shunt for metrological calibration to calibrate the bandwidth of other types of pulsed current sensors.

[0007] To achieve the above object, the technical solution adopted by the present invention is: it includes an outer conductive circular tube and an insulating circular tube coaxially installed inside it, and an alloy-insulating multi-layer resistor circular tube is provided on the outer wall of the insulating circular tube;

[0008] Upper and lower metal end caps are electrically connected to the upper and lower ends of the insulating circular tube respectively. An insulating ring connected to the upper end of the outer conductive circular tube is provided on the upper metal end cap, and a current injection electrode is installed at the center of the insulating ring, 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 circular tube, and a coaxial connector is provided 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] A return end connected to the lower metal end cap is also installed on the outer conductive circular tube.

[0011] The alloy-insulating multi-layer resistor circular tube is a composite layer of an alloy metal layer and an insulating layer formed by spraying a metal alloy evenly on the outer surface of the insulating circular tube by a spraying mechanism to form an alloy metal layer, and then coating an insulating layer on the outer surface of the alloy metal layer. The number of layers of the composite layer is 2 to 5 layers.

[0012] The thickness of the alloy metal layer of the alloy-insulating multi-layer resistor circular tube is 5 to 100 μm, and the thickness of the insulating layer is 10 to 100 μm.

[0013] The spraying of the resistor circular tube is Kanthal alloy, nickel-chromium alloy or constantan alloy.

[0014] The gap between the inner wall of the outer conductive circular tube and the outer wall of the alloy-insulating multi-layer resistor circular tube is 0.2 mm - 1 mm.

[0015] The insulating circular tube is a ceramic circular tube, and its two end faces are metallized. The thickness of the metallized layer is 20 - 100 μm, and the height of the outer edge metallization treatment on the outer surfaces of both ends of the insulating circular tube is 5 - 8 mm, and the thickness is 10 - 100 μm.

[0016] The upper metal end cap is of a T-shaped structure. The outer diameter of the lower end of the upper metal end cap is the same as the inner diameter of the insulating circular tube and is embedded in the insulating circular tube. The embedding depth is 5 - 10 mm. The outer diameter of the upper end of the upper metal end cap is the same as the outer diameter of the insulating circular tube.

[0017] The lower metal end cap is of an inverted T-shaped structure. The outer diameter of the upper end is the same as the inner diameter of the insulating circular tube and is embedded in the insulating circular tube. The embedding depth is 5 - 10 mm. The outer diameter of the lower end is the same as the inner diameter of the outer conductive circular tube and is tightly connected to the outer conductive circular tube by a screw thread.

[0018] The upper end of the outer conductive circular tube has a turned-out outer edge. The insulating circular ring is connected to the outer conductive circular tube by a screw thread. The current return end is arranged on the turned-out outer edge of the outer conductive circular tube.

[0019] In the present invention, on the outer surface of the insulating circular tube, a metal alloy is sprayed and an insulating material is coated by a spraying process to form a multi-layer resistor body circular tube, and its thickness can be controlled by the spraying process. By spraying or coating a high-temperature insulating layer on the outer surface of the alloy-insulating multi-layer resistor body circular tube, therefore, the distance between the outer conductive circular tube and the alloy-insulating multi-layer resistor body circular tube can be designed to be as close as possible. When a pulsed high current passes through, since the thickness of each alloy layer of the resistor body circular tube made by the spraying process can be controlled to the μm level, it is ensured that the response time of the coaxial tube type shunt can be obtained as fast as possible in theory; at the same time, since the magnitudes of the currents passing through the outer conductive circular tube and the resistor body circular tube are equal and the directions are opposite, and the distance between the two is extremely close, the residual inductance of the coaxial tube type shunt can be made extremely small, greatly reducing the overshoot phenomenon of the pulsed current and improving the accuracy of measuring the fast pulsed current with a short rise time. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0021] Figure 2 is a schematic structural diagram of the alloy-insulating material two-layer resistor body of this Embodiment 1; Detailed Embodiment

[0022] The structural principle and working principle of the present invention will be further described in detail below with reference to the drawings.

[0023] See Figure 1, the present invention includes an outer conductive circular tube 1, an alloy-insulating multi-layer resistor circular 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 circular tube 8. The insulating circular tube 8 is coaxially installed inside the outer conductor tube 1, and the alloy-insulating multi-layer resistor circular tube 2 is coaxially installed on the outer surface of the insulating circular tube 8. The alloy-insulating multi-layer resistor circular tube 2 is formed by a multi-layer resistor structure formed by alloy spraying and insulating material coating on the outer surface of an insulating circular tube 8 with a diameter of Φ50-200mm and a length of 100-500mm. The thickness of the alloy metal layer 2-1 of the alloy-insulating multi-layer resistor circular tube 2 is 5μm-100μm, and an insulating coating with a thickness of 10-100μm or a high-temperature insulating material with a thickness of 10-100μm is sprayed on the outer surface of the alloy metal layer 2-1. Since an insulating coating is sprayed on the outer surface of the alloy-insulating multi-layer resistor circular tube 2, the gap distance between the outer conductive circular tube 1 and the alloy-insulating multi-layer resistor circular tube 2 is as close as possible, and the gap between the inner wall of the outer conductive circular tube 1 and the outer wall of the alloy-insulating multi-layer resistor circular tube 2 is 0.2-1mm.

[0024] See Figure 1 , the insulating circular tube 8 of the present invention is a ceramic circular tube, and its two end faces are metallized. The thickness of the metallized film is 20-100μm, and the outer edges of the outer surfaces of both ends of the insulating circular tube 8 are metallized with a thickness of 5-8mm and a metallization thickness of 10-100μm to facilitate good electrical connection with the sprayed metal layer of the alloy-insulating multi-layer resistor circular tube 2. The metallized end faces at both ends of the insulating circular 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 cap 6 has a "T" shape. The lower end of the upper metal end cap 6 is embedded in the insulating circular tube 8 with an embedding depth of 5-10mm. The diameter of the upper surface of the upper metal end cap 6 is the same as the outer diameter of the insulating circular tube 8 and is tightly and reliably electrically connected to the metallized layer on the upper end face of the insulating circular tube 8; the connection between the lower metal end cap 7 and the lower end face of the insulating circular tube 8 is the same as the connection between the upper metal end cap 6 and the upper end face of the insulating circular tube 8, and the lower metal end cap 7 is tightly connected to the lower end of the outer conductive circular tube 1 by a screw thread. The lower metal end cap 7 can also be a metal circular tube integrated with the outer conductive circular tube 1.

[0025] See Figure 1, an insulating ring 9 is provided on the upper metal end cap 6, and the outer diameter of the insulating ring 9 is the same as the inner diameter of the outer conductive circular tube 1; the outer conductive circular tube 1 has a turned-out outer edge, and the width of the outer edge is 15 - 25 mm and the thickness is 15 - 20 mm. The insulating ring 9 is threadedly connected to the outer edge of the outer conductive circular tube 1. The current injection electrode 3 passes through the insulating ring 9 and is installed on the metal end cap 6 by threading and fixed by a nut 10 for electrical connection with the measured pulsed current circuit. The current return end 11 is provided on the turned-out outer edge of the outer conductive circular tube and is electrically connected to the pulsed current circuit through a nut 12. The current output by the pulsed current generating device flows into through the current injection electrode 3, and a pulsed current path is formed through the lower metal end cap 7 - the outer conductive tube 1 - the return end 11. Since the current in the resistance body circular tube 2 is equal in magnitude and opposite in direction to the current in the outer conductive tube 1, and the gap distance between the resistance body circular tube 2 and the outer conductive tube 1 is extremely close, the coaxial tube type current shunt has extremely low residual inductance, greatly improving the waveform accuracy of pulsed current measurement.

[0026] See Figure 1 , the lower metal end cap 7 has a round hole for installing the voltage coaxial connector 5. The metal shell of the voltage coaxial connector 5 is closely electrically connected to the lower metal end cap 7, and the core wire of the voltage coaxial connector 5 is connected to the current injection electrode 3 through a voltage lead wire 4.

[0027] See Figure 2 , the alloy-insulating multi-layer resistance body circular tube 2 is composed of a spraying mechanism spraying metal alloy uniformly on the outer surface of the insulating circular tube 8 to form an alloy metal layer 2-1, and coating an insulating layer 2-2 on the outer surface of the alloy metal layer 2-1 to form a composite layer of the alloy metal layer and the insulating layer. The number of alloy-insulating alternating composite layers can range from 2 layers to 5 layers, and the number of composite layers adopted in the present invention is 2 layers.

[0028] The alloy metal is Kanthal alloy, nickel-chromium alloy or constantan alloy, etc., and the insulating material can be epoxy resin, etc.

[0029] The remarkable features of the present invention different from the existing coaxial tube type current shunts are: one is that the spraying process is adopted to spray metal alloy on the outer surface of the insulating circular tube to form a resistance body circular tube, and its thickness can be controlled by the spraying process. When the thickness of the alloy-insulating resistance body circular tube is controlled at several μm, the response time of the coaxial tube type current shunt can reach the ns level, and steep pulsed current with a rise time above 10 ns can be measured; the other is that a high-temperature insulating material is sprayed on the outer surface of the alloy-insulating multi-layer resistance body circular tube, so that the gap distance between the alloy-insulating multi-layer resistance body circular tube and the outer conductive circular tube can be controlled to be extremely close, making the residual inductance of the coaxial tube type current shunt extremely small, greatly reducing the overshoot phenomenon in pulsed current measurement and improving the accuracy of fast rise time pulsed current measurement.

Claims

1. A fast-response-time coaxial tube shunt with an alloy-insulating multi-layer resistor structure, characterized in that, it includes an outer conductive circular tube (1) and an insulating circular tube (8) coaxially installed therein, and an alloy-insulating multi-layer resistor circular tube (2) is provided on the outer wall of the insulating circular tube (8); The alloy-insulating multi-layer resistor circular tube (2) is a composite layer of an alloy metal layer and an insulating layer formed by spraying a metal alloy uniformly on the outer surface of the insulating circular tube (8) by a spraying mechanism to form an alloy metal layer (2-1), and coating an insulating layer (2-2) on the outer surface of the alloy metal layer (2-1), and the number of layers of the composite layer is 2 to 5 layers; Upper and lower metal end caps (6, 7) are electrically connected to the upper and lower ends of the insulating circular tube (8) respectively. An insulating ring (9) connected to the upper end of the outer conductive circular tube (1) is provided on the upper metal end cap (5), and a current injection electrode (3) is installed at the center of the insulating ring (9), and the lower end of the current injection electrode (3) is connected to the upper metal end cap (5); The lower metal end cap (7) is connected to the lower end of the outer conductive circular tube (1), and a coaxial connector (5) is provided at the center of the lower metal end cap (7), and the core wire of the coaxial connector (5) is connected to the current injection electrode (3) through a wire (4); A return end (11) connected to the lower metal end cap (7) is also installed on the outer conductive circular tube (1).

2. The fast-response-time coaxial tube shunt with an alloy-insulating multi-layer resistor structure according to claim 1, characterized in that: The thickness of the alloy metal layer of the alloy-insulating multi-layer resistor circular tube (2) is 5 to 100 μm, and the thickness of the insulating layer is 10 to 100 μm.

3. The fast-response-time coaxial tube shunt with an alloy-insulating multi-layer resistor structure according to claim 2, characterized in that: The spraying of the resistor circular tube is Kanthal alloy, nickel-chromium alloy or constantan alloy.

4. The fast-response-time coaxial tube shunt with an alloy-insulating multi-layer resistor structure according to claim 1, characterized in that: The gap between the inner wall of the outer conductive circular tube (1) and the outer wall of the alloy-insulating multi-layer resistor circular tube (2) is 0.2 mm - 1 mm.

5. The fast-response-time coaxial tube shunt with an alloy-insulating multi-layer resistor structure according to claim 1, characterized in that: The insulating circular tube (8) is a ceramic circular tube, and its two end faces are metallized. The thickness of the metallized layer is 20 - 100 μm, and the height of the outer edge metallization treatment on the outer surfaces of both ends of the insulating circular tube is 5 - 8 mm, and the thickness is 10 - 100 μm.

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

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

8. The fast-response time coaxial tube shunt with an alloy-insulating multi-layer resistor structure according to claim 1, It is characterized in that: The upper end of the outer conductive circular tube (1) has a turned-out outer edge. The insulating circular ring (9) is connected to the outer conductive circular tube (1) by a screw thread. The current return end (11) is arranged on the turned-out outer edge of the outer conductive circular tube (1).

Images