Vacuum Switch Research Articles

Influences of Target Configurations on the Trigger Characteristics of Laser-Triggered Vacuum Switch

Working performances of laser-triggered vacuum switch (LTVS) mainly rely on the interactions of laser with target materials. Influences from target configuration, which is one of key factors in the interactions, are neglected so far. The trigger performances of LTVS with different target configurations are studied in this paper. Relevant influence factors about target configurations are discussed briefly based on theoretical analysis about the trigger process. The test prototype is established based on detachable vacuum chamber. The trigger characteristics of LTVS with different target structures, target depths, and laser focal positions are compared. The relationships between target configurations and trigger performances of LTVS are analyzed and discussed. The preferred targets in LTVS are suggested while considering its lifetime. The test results prove that the conical target shows the best trigger performances compared to other targets. Due to the enlarged laser irradiated area and shortened plasma moving distance, the delay time of LTVS reduces with the decrease in conical target angle and the increase in target depth, while the delay time is controlled within 32 ns. Benefited from laser reflection and plasma collision, the trigger performances of conical targets can be enhanced by focusing laser on the target side surface. In particular, the 90° conical target with 1.5 mm depth is suggested to be employed in LTVS products.

Research on Pancake-Coil Electromagnetic Launch Intercepting System

With pancake-coil electromagnetic launcher as a research object, the experimental platform of the pancake-coil electromagnetic launch intercepting system with 50-kV pulse capacitors as energy storage was built and tested for discharge to study the electromagnetic launch intercepting system. The oscillation problem of the current flowing through freewheeling loop was solved by connecting the reverse-cut diode stack in series with trigger vacuum switch (TVS). However, due to limiting power component, the experimental system can work normally at 9.4-kV capacitor voltage. A proportional 3-D model of the pancake-coil electromagnetic launcher and an external excitation circuit model were established based on the structural and circuit parameters of the experimental system to perform simulation. The accuracy of the simulation model was proved by comparing the simulated and measured currents obtained under same capacitor parameters. Based on the established finite element model, maximum launching capacity and energy efficiency of the experimental system platform were estimated through simulation, and the space–time distribution characteristics of the magnetic field were analyzed during the launching process. In addition, the electromagnetic-structure coupling simulation was carried out to study the deformation problems of components of launcher by sequential coupling. All the work done in this paper provides guidance for a detail research, and we want to try to improve our electromagnetic launch experimental system.

Analysis and design of a pulse‐closing vacuum switch for catenary fault detection

This study presents a novel pulse-closing vacuum switch (PCVS) that is used for catenary fault detection and location. First, as the application background of PCVS, the principle theory of the fault detection and locating system is briefly introduced. Then, the PCVS is analysed and designed based on the detailed analysis of its working process and principle. To validate the performance of the designed PCVS, the multi-physical domain co-simulation numerical model is implemented using the ANSYS Maxwell and ANSYS Simplorer. Finally, a PCVS prototype is developed with permanent magnet closing and repulsive force opening to verify the simulation results. The simulations and experiments both approve that the contact time between the moveable contact and static contact can be controlled to be <6 ms. This meets the pulse-closing technology requirement for the fault detection and locating system.

Vacuum Switch Contact Position Detection Based on Labview

Arc shape of vacuum switch is one of the main influencing factors of the breaking performance of vacuum switch. The contact opening distance directly affects the development of arc shape. How to accurately detect the real-time position of the contact and calculate the contact distance is of great significance. Therefore, based on Labview virtual instrument technology, a software and hardware system for real-time position detection of contacts for vacuum interrupter is designed. The system collects the arc image during the vacuum switch opening process by high-speed camera, and then uses the virtual instrument development platform Labview as the programming software to process the arc image and analyze the edge features. Finally, the edge information detected is used for fitting, to realize pinpoint of the moving and static contacts. The experimental results show that the detection system can accurately detect the real-time position of the contact. It has the characteristics of high detection efficiency, stable operation and easy operation. The detection results provide technical support for analyzing the vacuum switch arc shape.

No-Load Dielectric Recovery of the Ultra-Fast Vacuum Switch in Hybrid DC Circuit Breaker

The no-load curve of the dielectric recovery strength of the ultra-fast mechanical vacuum switch (MVS) changing with time is the theoretical foundation to optimize the turn-off strategy of the hybrid direct current circuit breaker with load commutation switch. To avoid the shortcomings of the classic synthetic circuit, a novel test circuit is proposed to measure the no-load dielectric recovery curve of the MVS in this paper. In the test circuit, a succession of pulse voltages is automatically applied on the MVS, and multiple breakdowns of the MVS occur in one test. Therefore, the dielectric strength of the MVS at multiple time points is obtained, and the envelope of the applied voltage on the MVS during one test can describe the dielectric recovery curve of the MVS; as a result, the test workload could be reduced dramatically and the measurement is more authentic. By changing test conditions, including the rate of rise of the test voltage and the operating speed of the MVS, no-load dielectric recovery characteristics are studied. The research has shown that the dielectric recovery speed of the MVS is irrelative with the rate of rise of the test voltage and it is directly proportional to the opening speed of the MVS.

Study on the trigger mechanism of a laser triggered vacuum switch

According to the preliminary study, the laser triggered vacuum switch (LTVS) might be an advanced high-voltage, high-intensity pulse switch. It will have the advantages of short trigger conduction time and good isolation from the main circuit. The study of the trigger mechanism of LTVS is not only conducive to both the optimization and the miniaturization, and also beneficial to promoting its practical process. In this paper, the LTVS which has a composite trigger electrode made of potassium chloride and titanium is studied. The material loss on the focal spot of the trigger before and after the triggering process is compared by X-ray spectroscopy. Based on the result, the composition of the plasma mass generated by LTVS is analyzed. The trigger mechanism of LTVS is proposed for laser ablation and vaporization according to the physical phenomenon and the analysis. The research about the trigger mechanism of the LTVS is of great guiding significance for its optimization and application.

Compact electromagnetic pulse forming system based on the trigger vacuum switch

Electromagnetic pulse forming (EMPF) is a type of electromagnetic manufacturing technology which produces a powerful Lorentz force to change the shape or form of a work piece. In this paper, a 6.75-kJ/15-kV compact EMPF system based on the RVU-43 trigger vacuum switch is designed, fabricated and tested. The RVU-43 has good performance in a high-voltage discharge process that can withstand 25 kV and conduct 400 kA. A trigger source for the RVU-43 based on a pulse transformer and a solid-state switch can generate a rectangular trigger pulse of an adjustable amplitude of 0–5 kV and a pulse width of 0–5 μs. A simulation model is built in PSPICE to analyze the parameters affecting the performance of the EMPF. The results show that the system inductance can affect the peak current and the rise time, while the system resistance can affect the peak current. Connecting the capacitors in parallel, reducing the discharge loop area and designing a single-turn forming coil with a 30-degree field shaper are used to reduce the influence of the system parameters. The results of experiments for changing the shape of an aluminum alloy tube suggest that the EMPF system can form and process the metal tube successfully.

Design, Construction, and Test of a Lightweight Thomson Coil Actuator for Medium-Voltage Vacuum Switch Operation

This paper details the design, construction, and test of a lightweight, low energy usage Thomson Coil actuator for the operation of a commercial medium-voltage vacuum switch. A novel latching design, directly linked to the actuator armature, helps to keep the actuator mass at minimum. Experimental results show that 125 J of electric energy is sufficient for operation of a commercial 27 kV vacuum interrupter in times suitable for medium-voltage dc protection applications. The use of high conductor density coils is shown to play a key role on the observed actuator performance. Finite element simulations are used to demonstrate that shorter operation times are feasible, without augmenting the consumed electrical energy, by further increasing coil conductor density.

Analysis of Dynamic Arc Parameters for Vacuum Circuit Breaker Under Short-Circuit Current Breaking

The vacuum circuit breaker (VCB) is an important vacuum switch widely used in generator protection systems and medium-voltage distribution power systems. For observing the vacuum arc behavior variation and analyzing the dielectric recovery characteristics and interrupting capability of VCBs, an experimental platform for a 40.5-kV/31.5-kA/2500-A VCB was established. Under the condition of typical short-circuit current breaking, the short-circuit current breaking test was carried out and the vacuum arc image was collected to obtain the curve of voltage versus current during the breaking process and the arc resistance distribution. By analyzing the variation trend of dynamic arc resistance, a physical and mathematical description of dynamic arc resistance was obtained by the curve fitting method. By comparing and analyzing the experimental data of arc resistance, it is shown that the physical and mathematical description can appropriately describe the spatiotemporal variation of arc resistance in the arcing interval.

Investigations on the safe stroke of mechanical HVDC vacuum circuit breaker

Here, a DC vacuum arc interruption test based on the hybrid high-speed actuator and the method of commutation is carried out in the synthetic loop system. The safe stroke is one of the basic breaking parameters. The minimum safe stroke directly determines the commutation time and breaking property of the mechanical DC vacuum circuit breaker. The main circuit breaker is a high-speed vacuum switch driven by electromagnetic repulsion actuator. In order to simplify its control system, the commutation switch also adopts high-speed vacuum switch. The main current source for verification test of this DC breaker system is provided by a LC oscillator circuit with lower frequency. Simulations with some experiments were completed on breaking process of this system by PSCAD. The breaking current is 4 kA by the DC breaker system proposed here, the opening speed is about 2.417 m/s in this experimental system; From the results, the simulation and experimental waveforms are compared and analysed, and some effects on safe stroke of the DC vacuum circuit breaker is studied. The shortest arcing time is about 0.89 ms and the minimum safe stroke is about 2.15 mm under the lower voltages.

Мікропроцесорний пристрій для діагностування електромагнітного привода вакуумного вимикача

The paper proposes a microprocessor device for diagnosing the electromagnetic drive of a vacuum switch. It is investigated that the reliable operation of the vacuum switch depends on the technical condition of the electromagnetic actuator. Microprocessor diagnostic devices allow controlling the quality of manufactured electromagnetic actuators at the stage of initial control of the manufacturer and in the process of their operation in production. On the basis of a mathematical model, which provides for the measurement of the "reference" curve of the magnetic characteristic after the new switch is put into operation or after its overhaul and comparison of this curve with the subsequent measured magnetic characteristics in the course of its further operation. During operation, the shape of the web-ampere characteristics of the windings of the electromagnetic drive of the vacuum switches changes. The control of deviation from the "reference" characteristic allows estimating the current state of the electromagnet and its degree of wear. The block diagram of the microprocessor device of the system of diagnostics of the electromagnetic drive of the vacuum switch is developed. The microprocessor device functions according to the developed mathematical model. The main components of the device are the AT32UC3L032 microcontroller, switching units, current sensors and voltages. The AT32UC3L032 microcontroller is the best option in terms of cost and specifications (low power consumption, high code density, and high performance). The algorithm of functioning of the diagnostic device and its hardware necessary for the construction of the diagnostic system has been developed. The operation of the device involves determining the technical condition of the drive, indicating the result of the diagnosis on the display device near the diagnostic device and transmitting through the interface of the converter the current status of the electromagnetic drive from the microcontroller to the computer operating personnel.

Развитие импульсного дугового разряда в вакуумном диоде с искровым поджигом

In a number of technology fields (devices for lighting fast processes with X
ray impulses, neutron logging equipment), the heavy current electronic devices of which must comply with certain key requirements such as lack of incandescent circuits, compact sizes, wide range of switched currents, and stability to external impacts, compact vacuum switches are used, which are sometimes called in the literature as vacuum diodes. The insulating vacuum gap in such devices is closed by injecting a plasma bunch into it. As is well known, the plasma propagation velocity under such conditions depends of the electric field direction in the switched gap. The simplest apparatus among electric discharge switching devices, which therefore can be made with the most compact sizes, is the one in which breakdown is initiated, followed by spark discharge over the dielectric surface, as a result of which plasma from the dielectric surface is injected into the vacuum gap. It is shown that conducting medium is generated in rarefied gas through photoionization, and the breakdown current over the dielectric surface is produced by the flow of electrons emitted from the cathode spot. The transition of discharge to the arc stage in the switched vacuum gap is preceded by escape of electrons from the plasma jet produced on the cathode, emission of ions, and ambipolar drift of plasma to the anode.

RETRACTED: Short-term dielectric recovery property of breaking for artificial zero current-limiting vacuum circuit breaker

In order to research influences of di/dt on breaking capacity of vacuum switch in the process of direct-current interruption at the time of clearance between open contacts, arc time, and current ze...

Study on Trigger Lifetime of Target Electrode on Laser-Triggered Vacuum Switch

The trigger lifetime of the target electrode has a great effect on the triggering characteristics of the laser-triggered vacuum switch. In this paper, the relevant experimental research shows that when the main voltage is 1 kV and the laser energy is 10 mJ, a irradiation point on the target electrode can work continuously 18 000 times. By comparing two laser energy of 10 and 3 mJ, it is found that the KCl/Ti loss ratio of the high-energy laser pulse is much larger than that of the lower energy laser pulse, which will worsen the conduction performance more rapidly, therefore, it is necessary to adjust the mixing ratio of KCl and Ti in accordance with the energy of the pulsed laser to increase the conduction reliability of the switch and the lifetime of the target electrode. In the pulsed-arc spectroscopy experiments, the laser pulse energy has little effect on the intensity of the arc spectrum, however, the intensity of the arc spectrum increases obviously with the increase of the main gap voltage of the switch and the enhancement effect of voltage on different linear lines is different, which means that the density and number of different plasmas are not increased uniformly.

Study of Laser-Triggered Vacuum Switch with a Six-gap Rod

In this paper, the triggered polar material structure of the Laser Triggered Vacuum Switch (LTVS) was redesigned and the shape of the main electrode was improved. At last, we know that when the gap length of the LTVS is 12mm and the withstand voltage is 30kV, the LTVS is successfully conducted with 5kV gap voltage and 10mJ laser whose wavelength is 1064nm. Meanwhile, jitter time of the switch is approximately 2ns and the conduction time is approximately 20ns. By comparing the gap voltage, capacitance value, laser power and laser wavelength, the implications of such improvements on the jitter time and conduction time of the switch are discussed.

Ablation characteristics of hybrid target materials for laser triggered vacuum switches

The key difference of laser triggered vacuum switch (LTVS) and electrical triggered vacuum switch (ETVS) is the different triggered way, because the initial plasmas were generated by laser irradiation target material of LTVS, which generates different impact on the triggered characteristics of LTVS with different target materials. There are three laser wavelength (1064nm, 532nm and 266nm) which are tested the triggered characteristics of target materials, with decreased conduction time delay under the condition of increasing laser energy.

The Effect of Laser Energy on the Initial Plasma Characteristics of Laser-Triggered Vacuum Switch

With the development of pulsed-power technology, more and more applications require high-voltage and heavy-current pulse switches. Laser-triggered vacuum switch combines laser technology, vacuum switch technology, and three-electrode trigger switch technology, and has the advantages of heavy current capability, good isolation from the main circuit, and short delay time. In this paper, the 1-D thermal conduction model was developed to analyze the influence of laser energy on the velocity of initial plasma. The relationship between the ablation area and the laser energy was derived. The theoretical analysis can be verified by the relationship between the trigger delay time and laser energy and the initial plasma microcurrent curve in the experiments.

Investigation of high-voltage pulse trigger generator based on photo-conductive semiconductor switch

The trigger to generate high-voltage pulse is one of the most important parts in a pulsed-power system, especially for the conduction characteristics of the main switch. However, traditional triggers usually have the drawbacks of large structure and worse long-term working stability, which goes against the demands of pulsed-power system miniaturization and stability. In the paper, a pulse trigger using photo-conductive semiconductor switch was developed, which is of small size, stable performance and steep leading edge of the output pulse rise. It is found that the output trigger pulse rise time is 14 ns, and the jitter of 20 shots is 330 ps. Applying the designed pulsed trigger in a field distortion switch and a triggered vacuum switch, experiments show that the switches could be triggered stably with reduced jitter.

Researches on Position Detection for Vacuum Switch Electrode

Form and transformation character of vacuum arc is important influencing factor on the vacuum switch performance, and the dynamic separations of electrode is the chief effecting factor on the transformation of vacuum arcs forms. Consequently, how to detect the position of electrode to calculate the separations in the arcs image is of great significance. However, gray level distribution of vacuum arcs image isn’t even, the gray level of burning arcs is high, but the gray level of electrode is low, meanwhile, the forms of vacuum arcs changes sharply, the problems above restrict electrode position detection precisely. In this paper, algorithm of detecting electrode position base on vacuum arcs image was proposed. The digital image processing technology was used in vacuum switch arcs image analysis, the upper edge and lower edge were detected respectively, then linear fitting was done using the result of edge detection, the fitting result was the position of electrode, thus, accurate position detection of electrode was realized. From the experimental results, we can see that: algorithm described in this paper detected upper and lower edge of arcs successfully and the position of electrode was obtained through calculation.

Research on the Prebreakdown Current of the Laser-Triggered Vacuum Switch

The prebreakdown current flowing in a laser-triggered vacuum switch (LTVS), investigated in this paper, is below the threshold voltage, where the switch becomes conducting. The laser irradiates in a short time the sintered KCl and Ti target of the vacuum switch and produces an initial plasma. The prebreakdown currents are measured in two different electrode geometries (planar and multirod) at both polarities and analyzed with respect to the ion and electron interactions with the electrodes. It is found that the peak value of the prebreakdown current increases with the applied voltage across the LTVS until 60 to 80 V, where it turns instantly into the conducting state. The multirod and planar LTVSs show different prebreakdown currents at different polarities, which is related to the condition of becoming conducting.