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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. [ABSTRACT FROM AUTHOR]

The objective of this paper is to determine the influences of the transverse magnetic field (TMF) and the axial magnetic field (AMF) on prestrike inrush current arc behaviors in vacuum interrupters (VIs) during capacitive making processes. Two types of cup-type VI contacts were used: TMF contacts and AMF contacts. The contact diameter of the VIs was 48 mm. The insulating envelopes of the VIs were transparent, and there was no metal vapor shield inside the VIs, which were arranged for the observation of the prestrike arcs. The inrush current arc behaviors were recorded by a high-speed charge-coupled device video camera. The experimental results revealed that the VIs of cup-type AMF contact showed a higher dielectric strength than those of cup-type TMF contact during the making operations of inrush current. In addition, the arcs in VIs of cup-type TMF contact tended to be intense arcs that caused serious welding than those of VIs of cup-type AMF contact. Moreover, the cup-type AMF contact effectively reduced the prestrike arc erosion on the contact surfaces than those of TMF contact during the prestrike process of inrush current. [ABSTRACT FROM AUTHOR]

Power supplies have played crucial role to improve and extend plasma applications. Several dc, pulsed, and radio frequency (RF) stabilized power supplies have been developed over a wide range of frequencies and voltage waveforms. However, the influence of voltage waveform on the plasma densification, mainly due to the secondary electrons emission from the electrodes, has not been quite explored. This paper proposes an asymmetric pulsed bipolar power supply, adjustable in frequency, amplitude, pulsewidth, and number of pulses for generation of cold plasmas. Short period positive pulses, between longer negative pulses, increase greatly the secondary electron emission from the electrodes and, consequently, the plasma ionization rate. Short pulses (ns) are obtained by the phase shift between each carrier, and the high-intensity pulses are obtained by cascading the cell submodules in a half-bridge cascade topology, using a modular half-bridge converter configuration. The intensity of the positive and negative pulses can be varied independently. There is no unintended dc voltage level between the electrodes, which appear in RF plasmas. The plasma generated in this way is free of electric arc and can be kept stable within a broader range of operating parameters, mainly the voltage and the working gas pressure. [ABSTRACT FROM AUTHOR]

A magnetic pulse compressor (MPC) transfers energy via $C$ – $L$ – $C$ resonance. The pulse width of the MPC is determined by the saturation inductance of the magnetic switch (MS). When using the MS, the pulse width is limited due to the stray elements. To increase the pulse compression rate, the number of stray elements must be reduced. In this paper, we propose an optimum design for an MS having the lowest impedance of stray elements, along with its analysis and experimental verification. The proposed model is designed to have a reduced magnetic path length while retaining the same saturation inductances as that of a common MS; this is accomplished by using the relationship between the magnetic field path length and the number of inductor turns. The experimental results show that the proposed MS decreases the full width at half maximum by 18% and increases the rise rate by 69%. This result demonstrates that the proposed MS increases the pulse compression rate of the MPC by reducing impedance of stray elements in the system. [ABSTRACT FROM AUTHOR]

Coaxial magnetically insulated transmission line (MITL) was widely used in high-current pulsed power facilities. It is also an important option in future high-current accelerators based on the linear transformer driver (LTD) technology, in which the output line is usually coaxial to fit the component layout. In one of the schemes for high-current LTD accelerator, tens of coaxial MITLs are connected to conical disk lines in parallel. As a special structure, the coaxial–conical transition is a key component of the system. The feasibility of efficient current transmission under magnetic insulation condition is the precondition for building such a pulsed power facility. In this paper, we report the results of coaxial–conical MITL transition experiment which were conducted on the primary test stand (PTS). At the inner MITL of PTS, four coaxial MITLs were connected, gradually changed to mini-triplate and finally connected two conical MITLs. The total current at the entrance of coaxial lines (input) and at the conical MITL (output) were recorded. It showed that an output–to-input current efficiency of above 96% and of 87% across the transition was achieved with short load connection and open load connection, respectively. The 3-D transient electromagnetic simulation and 3-D particle-in-cell simulations were conducted to check the transmission efficiency, which confirmed very tiny loss when the load was short connected. [ABSTRACT FROM AUTHOR]

The quench protection switch (QPS) is an indispensable component ensuring the safety of the magnet coils of a superconducting Tokamak when a quench happens. In this paper, the second commutation process of a QPS based on artificial current zero is investigated. In this process, the current, which has already transferred from the bypass switch to the main circuit breaker, is forced to commutate from the vacuum circuit breaker (VCB) to the discharge resistor by the countercurrent. An LC oscillating circuit is applied to generate oscillating current to simulate the direct current near its peak which is about 20 kA. The countercurrent with frequencies of 500 and 1000 Hz is provided by a commutation branch. The equivalence of the experimental interrupting process compared with the practical situation is analyzed. Two kinds of vacuum interrupters of the VCB are used in experiments. One kind is equipped with contacts generating transverse magnetic field, and axial magnetic field contacts are used in another one. The experimental results indicate that the initial process of the vacuum arc before injecting the countercurrent has crucial impacts on the interruption performance. The countercurrent with the frequency of 500 Hz is easier to interrupt the current than the case of 1000 Hz. [ABSTRACT FROM AUTHOR]

In a magnetic pulse compressor (MPC), the saturation inductance of the magnetic switch (MS) determines the energy transfer time. Thus, in general, the number of windings on the MS is modulated to vary the saturation inductance. Changing the number of windings also changes the energy transfer time and the saturation time. In this paper, we propose and analyze an MS with multiwindings to modulate the pulse width without affecting the saturation time of the MS. The parallel structure of the multiwindings on the MS decreases the energy transfer time without affecting the saturation time. Through experiments, we show that the energy transfer time is decreased by 13% via a double winding MS. Therefore, an MS with multiwindings can be used to modulate the pulse width at the last stage of the MPC without affecting the saturation time of the MS. [ABSTRACT FROM AUTHOR]

Explosive current opening switches (EOSs) operate based on the principle of the conductors mechanical destruction of the inductive energy storage system by detonation products of the high explosive charge. The EOSs are used for current pulse sharpening of the magnetocumulative generators (MCG). These explosive single-acting devices constructively match each other; both operate in the physical limit and provide maximum specific characteristics. This paper describes several basic schemes of the EOS constructions that were experimentally checked in different laboratories of the world. The investigation results on the flat and cylindrical models and also full-scale experiments on the current pulses sharpening of the helical and disc MCG are presented. [ABSTRACT FROM AUTHOR]

The trigger voltage is usually high in traditional three-electrode gas switch, which makes the trigger system large and complex in large-scale pulsed power system such as linear transformer driver. In this paper, a three-electrode gas switch triggered by microhollow cathode (MHC) discharge is put forward, which can be operated stably under low trigger voltage. MHC discharge is a kind of microplasma with the characteristics of low trigger voltage (several thousand volts), high electron density, and high gas pressure discharge. In this switch, three MHC triggers sharing the same cathode are designed as the third electrode of the switch in the middle. Positive and negative high voltages are applied to two main electrodes, respectively. The breakdown characteristics of MHC discharge triggered by pulse voltage are first studied. The trigger voltage can be as low as 8 kV at 0.3 MPa in pure N2 with the discharge peak current up to 80 A. A circuit simulation model describing breakdown process of MHC is also built. Then two operating modes of the switch, three-electrode mode (T-mode) and two-electrode mode (D-mode), are analyzed. The stable operation with the charging voltage from ±35 to ±50 kV is realized under different working coefficients from 64% to 92% and different trigger voltages from 8 to 15 kV. The turn-on parameters including delay time, jitter, and turn-on time are studied that the delay time and jitter of D-mode are longer than that of T-mode under the same condition. At last, the improvement of MHC trigger for the stable operation of D-mode with shorter delay time is described. [ABSTRACT FROM PUBLISHER]

This paper describes a high-frequency pulsed-power generator for various industrial applications such as water treatment, food and medical apparatus for sterilization, or polluted gas treatment. The system is made of silicon-controlled rectifier as a main trigger switch, capacitors, two-stage magnetic pulse compression stages, and a linear transformer to generate a maximum of 120-kV, 5-kA pulse. The parameters obtained through the development are: output voltage: 120 kV (maximum), pulse repetition ration: 300 pulse per second, pulsewidth: 0.25~\mu \texts , and mean power: 30 kW. The designed pulsed-power generator is confirmed to be used effectively for many high-voltage pulsed-power applications related to environmental industry by simulation and experiments. [ABSTRACT FROM AUTHOR]

A novel circuit with the better performance for the inductive pulsed power supplies in the electromagnetic launch system is proposed in this paper, namely, the meat grinder with capacitive pulse forming unit (CPFU). Its working process is qualitatively analyzed stage by stage. Its practical feasibility is verified through a 7.5-kJ experiment. From the perspectives of circuit structure and working principle, this circuit can be regarded as the combination of a meat grinder and a CPFU. Compared with its preceding circuits, this circuit possesses following advantages: 1) the self-recovery of the capacitor precharged voltage can easily be achieved, which is conducive to continuous operations of the whole circuit and 2) the waveforms of the inductor currents contain no capacitive components, which can promote the energy storage density of the inductors. [ABSTRACT FROM PUBLISHER]

The opening switch is one of the critical technologies in the development of inductive pulsed-power supply. The power requirement is very high when the opening switch is desired to commutate a large current. This paper presents a zero-current opening circuit for inductive pulsed-power supply based on a high-temperature superconducting pulsed-power transformer. First, there are two types of current flowing through the opening switch, one comes from the secondary side of the pulse transformer, and the other one comes from superconducting energy storage inductance. The orientation of the two current is opposite. Then, when the current flowing through the opening switch closes to zero, the switch is opened and this restrains the over-voltage pulse of the opening switch. The simulation results indicate that this zero-current opening circuit is feasible and has potential applications for high-energy systems in the future electromagnetic launcher. [ABSTRACT FROM PUBLISHER]

High-voltage (HV) pulses are used in pulsed electric field (PEF) applications to provide an effective electroporation process, a process in which harmful microorganisms are disinfected when subjected to a PEF. Depending on the PEF application, different HV pulse specifications are required such as the pulse-waveform shape, the voltage magnitude, the pulse duration, and the pulse repetition rate. In this paper, a generic pulse-waveform generator (GPG) is proposed, and the GPG topology is based on half-bridge modular multilevel converter (HB-MMC) cells. The GPG topology is formed of four identical arms of series-connected HB-MMC cells forming an H-bridge. Unlike the conventional HB-MMC-based converters in HVdc transmission, the GPG load power flow is not continuous which leads to smaller size cell capacitors utilization; hence, smaller footprint of the GPG is achieved. The GPG topology flexibility allows the controller software to generate a basic multilevel waveform which can be manipulated to generate the commonly used PEF pulse waveforms. Therefore, the proposed topology offers modularity, redundancy, and scalability. The viability of the proposed GPG converter is validated by MATLAB/Simulink simulation and experimentation. [ABSTRACT FROM PUBLISHER]

In this paper, we present the first implementation of our 0–60-kV picosecond rise time 1–10-ns pulse generator. The pulse generator will be used in future work to generate a (sub-)nanosecond streamer plasma for air purification research. The first implementation of the pulse generator is a single-line pulse generator with an oil spark-gap, which generates 5 ns pulses with a 200 picosecond rise time and can operate at repetition rates of over 1 kHz into a 50 \Omega load. In this paper, we evaluate its performance and describe how we measure the very short pulses with an integrated and calibrated D-dot sensor. Furthermore, we present 3-D EM simulations of the 5 ns pulse generator and show that the simulations are in good agreement with the measurements. We previously described methods to flexibly vary the pulse duration of the pulse source by (artificially) changing the length of the pulse forming line (PFL). Here, we test these methods and find that changing the length of the outer conductor of the PFL and inserting magnetic material at the end of the PFL is a suitable method to change the pulse duration. Finally, we measure the breakdown voltages of the oil spark-gap and discover that higher pulse repetition rates are possible at higher oil pressures and smaller gap distances. [ABSTRACT FROM AUTHOR]

This paper describes the design, implementation, and comparison of high-voltage capacitor chargers for a solid-state pulsed power modulator (SSPPM). The three different converter topologies are a series resonant converter operating at a discontinuous conduction mode with switching frequency control (SRC_DCM_SFC), a series resonant converter operating at a continuous conduction mode with phase shifted pulse width modulation control (SRC_CCM_PSPWMC), and a series–parallel resonant converter operating at the CCM with SFC (SPRC_CCM_SFC). On the basis of these converter topologies, 10\-kW\rm{average} high-voltage capacitor chargers are designed for the three types of SSPPMs, which have the following maximum output specifications: 1) SRC_DCM_SFC: 60 kV, 300 A, 3 kpps, and 50 \mus; 2) SRC_CCM_PSPWMC: 10 kV, 50 A, 50 kpps, and 10 \mus; and 3) SPRC_CCM_SFC: 40 kV, 150 A, 7 kpps, and 10 \mus. Although the pulse output specifications are different, it is worth comparing the resonant inverter topologies and the control methods from the viewpoint of the losses, control characteristics, and merits and demerits of the high-voltage capacitor chargers. From the analysis and investigation of the three resonant inverters, the design procedure, including the determination of the resonant tank parameters, is provided, which considers the design of the high-voltage capacitor charger. PSPICE simulation is used to elucidate the effects of the resonant tank structure and its parameters, and the resonant current waveform and losses of the Insulated Gate Bipolar Transistor are compared. Finally, experiments for each charger are performed under various load conditions, and the comparison results of the three capacitor chargers, including the conduction and switching losses, control characteristics, and overall efficiency, are discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development and testing of a compact flat format multichannel electrically triggered rail spark gap. It is tested for multichannel discharge under atmosphere for high reliability. Multichannel discharge rail spark gaps can be developed using laser trigger or fast rising trigger voltage pulse (>5~kV/ns). The extra volume and weight added by laser or fast triggering circuits limit the use in pulse power applications. An electrically multitriggered low-inductance spark gap is developed. It is used as a multichannel low-inductance discharging element in a fast rising high-current generation system. The trigger of such rail gap is realized using the set of round copper pins similar to single trigger pin in a field distortion spark gap. In parenthesis, five different trigger pins are located in main trigger plate and these are isolated with high impedance. Therefore, five different trigger signals are generated with time difference of tens of nanoseconds. The major material erosion at five points of both stainless steel main electrodes confirms the multichanneling discharge. The main gap spacing in this switch is 4 mm and the trigger is located close to the ground electrode for reducing the delay time and jitter in delay time. This paper shows the trigger circuit design, main gap voltage, and trigger voltage effect on the closing of the spark gap and picture of electrodes after use. [ABSTRACT FROM AUTHOR]

A thermal model of a switched reluctance linear launcher is presented in this paper. The accuracy of the thermal model is verified by comparing experimental data with those results derived from finite-element method simulation. The temperature distribution of a switched reluctance linear launcher is derived based on the stator copper losses as the main heat power with measured stator winding current by the current sensor. The maximum temperature rise curves under different ambient temperature and different heat power of winding A are studied. The heat dissipation power of four air convection surfaces under different ambient temperature and the different heat power of winding A is also studied. Furthermore, this paper achieves optimization in thickness of the stator plate and in adding fins to the stator plate for heat dissipation with the present model. It is shown that the stator plate is the maximum heat dissipation power surface so that it can be adopted as the main heat dissipation channel and the effect of heat dissipation is obvious by adding fins to the stator plate. [ABSTRACT FROM PUBLISHER]

Normally, a three-electrode spark–gap switch is controlled by the application of an external trigger impulse. In this paper, a novel self-breakdown sharpening switch based on the three-electrode spark–gap switch is proposed. However, in this paper, the trigger electrode is connected to ground through a resistor, with the prespark between the trigger and the main electrodes providing the electrons and ions that initiate conduction of the main gap. A prototype sharpening switch with a breakdown voltage of 116.0 kV \pm 1.0 kV and a breakdown time of 3.396\ \mu\s\pm 0.036 \ \mu\s is described. When compared with a conventional two-electrode spark–gap sharpening switch, the novel sharpening switch has both a more stable breakdown voltage and lower jitter, and the dc breakdown and impulse breakdown characteristics of the two types of switches are presented and compared. When the impedance of the resistor connected to the trigger electrode is high, it is demonstrated that both the value of this resistor and also the type of load have little effect on the characteristics of the novel switch. However, the breakdown voltage of the novel sharpening switch was found to be sensitive to the rise time of the input pulse from the trigger generator. The prototype sharpening switch has a lifetime at least 20 000 shots and is now in use in a major pulsed power conditioning system. [ABSTRACT FROM PUBLISHER]

A 200 kJ pulsed power system (PPS) has been built up to drive pulsed plasma devices. This PPS consists of two 100 kJ capacitor bank modules, each comprising of five capacitors of each 178~\mu \textF , a discharge switch, and a pulse-shaping unit. When both the banks are charged simultaneously to −15 kV using full charging technique, it delivers a peak current 100 kA at the load (damping resistor and pulse-shaping inductor). Later on, a plasma system will be attached at the load which will also have an inductive and resistive effect. A fiber-optic triggering unit controls both the modules and there exists a flexibility of sometimes operating a single module only, besides there are provisions for further up gradation of the PPS to a targeted 600 kJ. Prior to this development, PSpice simulation was carried out to estimate the parameters of the circuit components to achieve the required wave pulse with precision. Using these parameters, a design of the PPS was made keeping into account about the critical issues involved and the ratings of the components, some of which were fabricated in house. This paper basically includes the criticality surrounding the operation of a high-energy long-pulse PPS under negative operating voltage. [ABSTRACT FROM AUTHOR]

The meat grinder is a basic circuit for inductive pulsed-power supply (IPPS). Based on meat grinder, the Institute of Advanced Technology proposed a circuit called the slow transfer of energy through capacitive hybrid (STRETCH) meat grinder, in which an Integrated Gate Commutated Thyristors (IGCT) is selected as the main switch. Tsinghua University proposed the STRETCH meat grinder with inverse current commutation with semiconductor devices (ICCOS) in which the main switch is replaced by a thyristor and the ICCOS subcircuit is introduced to turn off the main switch. To reduce the opening switch voltage and increase the current turning-off capacity for IPPS, this paper presents a novel circuit topology named the meat grinder with self-charged capacitor and thyristors (SECTs). The key idea of the SECT topology is to turn off the primary current by the energy transfer capacitor, which is precharged. The meat grinder with SECT has larger capacity than the STRETCH meat grinder because it replaces the IGCT with a thyristor and is simpler than the STRETCH meat grinder with ICCOS because it only needs one capacitor. The suggested circuit is more suitable for IPPS module with high energy density. Simulation and experiment have been carried out to validate the circuit. [ABSTRACT FROM PUBLISHER]

Magnetic pulse compression (MPC) system has been widely used over a few decades as a technique for producing short duration, high peak power pulses reliably. Novel MPC system which do not contain external demagnetization circuits, have broadened the appliance of MPC systems, in which circuit in each level of storage energy capacitors is composed of two capacitors in series, and the two-capacitance combination is connected to the output of previous stage, so that not only the pulse is compressed but also the voltage is doubled as well. In this paper, a 20-kHz high repetition-rate pulse generator with adjustable output amplitude based on Novel MPC system is presented. The pulse generator makes use of commercially available insulated gate bipolar transistor (IGBT), switching a capacitor bank into a ferrite transformer together with a voltage doubling circuit. The capacitor bank is charged to 530 V by a three-phase rectifier, also switched by a commercial diode. The amplitude of the output voltage of the pulse generator is controlled by the amplitude of the gate voltage of the IGBTs. Pulses with a width of 70 ns can be generated with repetition rates up to 20 kHz in burst. The amplitude can be controlled from 5 to 40 kV into a $500~\Omega $ resistive load. [ABSTRACT FROM AUTHOR]

This paper addresses inductive pulsed power generators and their major components. Different inductive storage designs, such as solenoids, toroids, and force-balanced coils, are briefly presented and their advantages and disadvantages are mentioned. Special emphasis is given to inductive circuit topologies, which have been investigated in railgun research, such as the XRAM, meat grinder, or pulse transformer topologies. One section deals with opening switches as they are indispensable for inductive storages and another one deals briefly with superconducting magnetic energy storage for pulsed power applications. Finally, the most relevant inductor systems, which have been realized with respect to railgun research, are summarized in Table I, together with their main characteristics. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) interference and its suppression are one of the major issues in most current systems design. The electric device such as railgun generates the EM fields that unintentionally propagate away from the structure. Railgun that have significant amounts of radiated emissions may interfere with the normal operation of other devices in close proximity. Also during the accelerating run of rail launchers, and particularly during the ignition of the armature, the radiated EM fields can compromise the life of electronic devices, can influence the signal to noise ratio, and can generate electrical shock hazard. The short duration pulse signal, such as current pulse of railgun, switching and arcing between components of railgun is typically rich in frequency spectral contents. It should be noted that the propulsive force of current pulse in each time push the armature in motion direction and change the propagation parameters of railgun as a time varying antenna and can affect on the radiation pattern in the various frequency ranges. Furthermore, in each component of current pulse, armature is in special position in direction of motion along the barrel and the impedance of railgun that power source see in front is different with previous stage and radiation pattern is different too. In this paper, the relationship between pulse form of input current and electric field around railgun are analyzed and simulated with finite-element method, then by attention of the armature position in each time it will be investigated the radiation pattern of railgun. [ABSTRACT FROM PUBLISHER]

With inherent strengths in energy density and power density, the inductive pulsed power supplies (IPPS) have become an attractive option for the power supplies in electromagnetic launch systems. The meat grinder circuits, including the slow transfer of energy through capacitive hybrid (STRETCH) meat grinder circuit, the STRETCH meat grinder with inverse current commutation with semiconductor devices circuit, and the meat grinder with self-charged capacitor and thyristors circuit, constitute one major branch among the IPPS circuits. This paper summarizes the fundamental research work and contributions of the meat grinder circuits from the perspectives of circuit improvements, performance analysis, inductor design, module collaboration, and efficiency promotion. The future directions of single IPPS module are higher energy level, larger energy density, and higher efficiency. [ABSTRACT FROM PUBLISHER]

This paper presents a novel technique for the voltage droop compensation of long pulses in solid-state bipolar high-voltage Marx generators. Considering the modularity of Marx generators the compensation consists in adding one extra stage to perform as a pulsewidth modulation circuit. This stage voltage is added to the output positive or negative pulses, and an output LfCf filter is included to smooth the voltage pulse waveform. A five-stage laboratory prototype of this circuit has been assembled using 1200-V Insulated Gate Bipolar Transistors and diodes with 1000-V dc input voltage. The circuit was operated at 50-Hz bipolar pulse rate, giving 4-kV bipolar pulses, into a resistive load, with 100- \mu \texts pulsewidth and 9.5-ms relaxation time. The circuit was able to compensate 10% of bipolar pulse voltage droop. [ABSTRACT FROM PUBLISHER]

DC power relay is a key electromechanical component widely used in electrical vehicles, photovoltaics, as well as more-electric aircrafts for energy managing, power conversion, and distribution. As the voltage and current increase due to relay switches, arc discharge becomes an unavoidable and significant issue during the operation of the dc high-power relay. Bridge-type contact and external permanent magnets are spontaneously employed in its arc chamber to accelerate the quenching of arc. In this paper, the complicated arc discharge plasma in a dc power relay has been investigated by using both experimental and numerical approaches. Initially, arc dwell and arc restriking characteristics during the arc motion phase are presented by analyzing the voltage and current waveforms and arc images acquired in carefully designed breaking experiments. The arc driven by a transverse magnetic field with a variety of flux densities and the influence of flux densities on arc voltage and dwell are preliminarily discussed based on the experimental results. Then, to reveal the arc physics and to determine the influence of transverse magnetic field on arc motion characteristics, a simplified model based on the magnetohydrodynamic (MHD) theory is built and three cases with different magnetic field are calculated. The simulated arc behaviors including distributions of the temperature and current density are presented. The mechanism underlying the influence of transverse magnetic field on the arc motion is analyzed according to arc root transfer and arc voltage variation. In addition, to understand the formation of the arc restriking, the critical breakdown electric-field strength inside the arc gap is also calculated based on streamer breakdown theory. The parameters in the space occupied by earlier arcs, as predicted by the MHD simulations, are used in the breakdown calculation. Results show that the critical breakdown voltage reduces remarkably along with growth of the operating voltage and breaking current, and the arc dwell time can be reduced by strengthening the external magnetic field within a reasonable extent. [ABSTRACT FROM PUBLISHER]

In this paper, a dual-electrode gas switch triggered by ejected plasma is proposed to ensure the switch to be triggered reliably under extremely low switching coefficient. The switch has the configuration of dual electrodes, in one of which a microincentive chamber is embedded to develop ejected plasma into the switch gap, leading to the breakdown of the switch. Both the features of ejected plasma and the triggering discharge characteristics of the switch are studied with different types of gas, gas pressures, voltage polarities, gap distances, triggering pulse energies, and so on. The results show that the switch can be triggered reliably in a much wide working voltage range, as the minimum switching coefficient is low to 9% with the delay time of about 10 \mu \texts . With the decrease of gas pressure and the increase of triggering pulse energy, the height of ejected plasma increases while the delay time of the switch reduces. The polarities of charging voltage and triggering voltage both have obvious influence on the delay time of the switch, and the effect of the former is greater. Under the same gas pressure and triggering pulse energy, the delay time in SF6 is much bigger than that in N2. [ABSTRACT FROM PUBLISHER]

In this paper, measurement results of the arc erosion limitation in low voltage (LV) switches are presented. The reduction of the arc erosion in the analyzed electromechanical switches was achieved through an application of the hybrid switching in the tested alternative current circuit during interruption of the inductive current. The presented method is based on a commutation of the current during its interruption into a semiconductor branch that is connected in parallel to the operated switch. Thus, this approach is able to limit the electric arc energy efficiently, and as a consequence the arc erosion of the electrical contacts is also significantly reduced. For this reason, the application of the hybrid switching has a positive influence on a lifespan and a reliability of the operated switch. In order to evaluate the influence of the hybrid switching application on an effectiveness of the limitation of the arc erosion in the analyzed LV switches, 50 000 current interruptions were conducted in the tested circuit by each of four analyzed switches. Researches were performed for two standalone switches during a standard current interruption, as well as, for two switches with applied the hybrid switching system. In order to compare the arc erosion of the contact surfaces in both considered cases, scanning electron microscope method coupled with energy dispersion spectroscopy was applied. Moreover, photos of the electric contact surfaces are presented. Additionally, frames registered by high-speed camera during current interruption are presented for both considered approaches. [ABSTRACT FROM PUBLISHER]

In the case of back-to-back capacitor banks switching, the inrush current arcs can locally melt the contact surfaces of vacuum interrupters (VIs) during the prestrike process. The contact materials significantly influence the behaviours of the inrush current prestrike arcs. The objective of this paper is to determine the influence of contact materials on prestrike arc behaviours of VIs during capacitive making processes. Six identical 12-kV VIs were used in the experiment after the proposed conditioning. The contact diameter of the VIs was 48 mm, and the insulating envelope was transparent. There were no metal vapour shields inside the VIs to enable the observation of the prestrike arcs. Two different contact materials (CuCr50/50 and CuW10/90) were used in the experiment. Test inrush currents were set to 5-, 10-, and 20-kA peak values, respectively. The inrush current arc features were recorded by a high-speed charge-coupled device video camera. It is discovered that the contact materials have a significant influence on the prestrike gaps. Moreover, the prestrike arcs in VIs with the CuW10/90 contact material tend to be more diffuse than those in VIs with the CuCr50/50 contact material. The results indicate the impact of different contact materials on the prestrike arc behaviours and reveal the contact erosion patterns for different materials. [ABSTRACT FROM PUBLISHER]

Pulsed-power generator based on linear transformer driver (LTD) technology has been used to demonstrate waveform control for pulsed atmospheric discharge. This kind of discharge load is known for its time-varying impedance where constant voltage usually does not result in constant current. In this paper, an LTD system has been combined with a field-programmable gate array in order to generate a flexible voltage waveform which, in turn, dictates the discharge current. The experimental results have proved that the current of a discharge load can be arbitrarily controlled, to a certain extent, by properly adjusting the applied voltage. This kind of current waveform control should have significant implications for various applications of discharge-generated plasmas. [ABSTRACT FROM PUBLISHER]

This paper discusses the modeling of a peaking switch to study the reduction in rise time for the subnanosecond duration pulses. The effect of the various shapes of input pulse, inductance, and interelectrode distance on the output voltage and wave shape is discussed in this paper. The modeling has been carried out using the electromagnetic and microwave modeling software of Computer Simulation Technology. [ABSTRACT FROM PUBLISHER]

This paper presents a power electronics converter to generate bipolar high-voltage pulses using low-voltage dc source. Converter is designed based on charging of different capacitors by a predetermined switching pattern and their discharging on the load for pulsed power applications. Low number of power electronics devices and bulky transformer elimination are main advantages of the proposed converter. According to new findings, bipolar high-voltage pulses may lead to higher efficiency in many applications, such as food sterilization industry. The proposed pulse generator generates bipolar controllable pulses with a modular circuit structure based on a capacitor-switched network. Experimental results are presented to verify the analysis. [ABSTRACT FROM AUTHOR]

In this paper, a novel method for high-repetition-rate high-power radio frequency (RF) pulse generation, which involves only passive solid-state devices and is capable of being used for generating high power microwaves using a low-to-high power converting scheme based on nonlinear self-compression is proposed. The method is also expected to be of low jitter. In the proposed circuit, two high voltage diodes with proper reverse recovery characteristics are used. The simulation results show that the proposed circuit generates RF pulses, with central frequencies up to gigahertz range. By applying a sub-kilowatt power supply, the maximum output power was well over 10 kW. This power can be increased up to megawatt order using power supplies of kilowatt range, as predicted by the theory. Simulations also indicated the possibility of 130-kHz pulse repetition rate as predicted by the theoretical analysis. The proposed method has been shown to work properly by an experimental setup. The setup showed the repetition rates up to 5000 pulses/s, which was capable of being increased to the simulation result using high quality circuit elements just as those used in the simulated circuit. We are currently carrying out a research to achieve the predicted upper limits of the power at gigahertz range RF generation and the results will be presented in their future reports. [ABSTRACT FROM AUTHOR]

Megavolt-class-triggered switches play a key role in large-induction voltage adder accelerators. This paper introduces a 2.8-MV, low-inductance, low-jitter, electrical-triggered, gas SF6 switch. The main section is a $V/n$ switch and the pretrigger section is a trigatron switch. Based on electric field simulation, experiment, and analysis, the structure and spacing of gaps, location of trigger disk, diaphragm, and switch inductance are all discussed. The primary test indicates that the switch can be operated in the range of 0.85–2.76 MV with the pressure of the SF6 changing from 0.1 to 0.9 MPa. The self-breakdown voltage is linearly related to the logarithm of the pressure, as the gap spacing and the voltage rise time are fixed. Three working modes were observed: self-breakdown, self-triggered, and ex-triggered. In the triggered modes, the switch jitter is <3 ns and the switch inductance is usually below 150 nH. [ABSTRACT FROM AUTHOR]

The parallel operation of array microhollow cathode (MHC) discharges is studied to generate high density of electrons owing to its multichannel MHC discharges. To ignite all the holes synchronously in one pulse, a pretrigger device is introduced, which is composed of three layers (two electrode layers and a dielectric layer). With the pretrigger process, some initial electrons can be injected into the holes, which makes array MHCs easier to ignite and improves the behavior of parallel operation. In this paper, the array MHC discharges with pretrigger in one pulse mode are presented and the influence on the parallel operation of the pretrigger process is studied. At last, the simulation result is given to have a better understanding of the pretrigger mechanism. [ABSTRACT FROM AUTHOR]

The series configuration of fast semiconductor switches seems to be the key component in the high-voltage and fast rising time pulse generation. In this approach, two important issues must be considered. The first is to provide a safe operating condition for the switches in transient intervals. The second is to design a gate drive system with the capability of driving a large number of discrete devices simultaneously. The aim of this paper is to obviate these two requirements. First, different factors affecting the unbalanced voltage sharing between the series switches are discussed. In this investigation, the switch-to-ground parasitic capacitance effect has been recognized as the major effect on the unbalanced voltage sharing in the transient interval. Two schemes for abating this effect are proposed. To solve the unbalanced voltage distribution, the structure with a snubber circuit in the clamp mode operation is suggested. This scheme can be used for any number of switches without destructively affecting their behavior. In addition, the output pulse with a fast rising time could be obtained by the proposed gate drive system. In order to evaluate the operation of the proposed structure, a stacked switch with the voltage capability of 36 kV is tested experimentally. The characteristics of the obtained pulse are the fast rising time (69.5 ns) with the dV/dt of 460 kv/ \mu \texts and the wide range of the pulsewidth adjusting to 0.5–15 \mu \texts . In addition, the voltage variance of the switches level in the series structure is about 10%. [ABSTRACT FROM AUTHOR]

This paper details the experimental evaluation and simulation of a 4-kV n-type gate turn-OFF thyristor (GTO) designed for pulsed power applications. The primary criteria of evaluation are rate of current rise ( dI/dt ), turn-ON delay time ( T_{D}) , and resistance of the device during turn-ON transients [ R_{\mathrm{\scriptscriptstyle ON}}(t)$ ]. The device under test (DuT) is an n-type asymmetric-blocking GTO manufactured by Silicon Power (Part No. 14N40A10) with a rated dc blocking voltage of 4 kV. A test circuit was specifically designed to minimize stray inductance in order to capitalize on the dI/dt$ capabilities of the DuT. Experimental data collected from resistance measurements are used to develop a single-switch approximate model for use in simulation. The results of dI/dt$ experiments provide a profile of DuT dI/dt$ operation beyond rated values; specifically dI/dt were readily achieved. The turn-ON delay time of the DuT is also characterized and determined to be $\sim 225$ ns on average. [ABSTRACT FROM AUTHOR]

A bipolar pulse has been proved to be more advanced in the treatment of tumor because of the elimination of muscle contractions and the effect for ablating nonuniform tissue. In this paper, a new type of modular bipolar pulsed-power generator based on Marx generator with double power charging is proposed. The concept of this generator is charging the two series of capacitors in parallel by two power sources, respectively, and then connecting the capacitors in series through solid-state switches with different control strategies. Utilizing a number of fast solid-state switches, the capacitors can be connected in series with different polarities, so that a positive or negative polarity pulse will be delivered to the load. The simulated models of this generator have been investigated in a PSPICE platform, and a laboratory prototype has been implemented in a laboratory. The simulation and test results verify the operation of the proposed topology in different switching modes. The development of this pulse generator can provide the hardware foundation for the research on biological effect without muscle contraction when the tumors are applied with bipolar pulse electric field. [ABSTRACT FROM AUTHOR]

The acceleration grid power supply (AGPS) is an important part of the neutral beam injector (NBI) system. With the increase in NBI power, the requirement for output voltage of the AGPS is becoming higher and higher, even reaching to 1000 kV. As the inverter-type high voltage power supply uses inverters located at the lower voltage side to regulate and cut off the output voltage, it is very suitable for high-voltage applications. The proposed scheme for the AGPS of the International Thermonuclear Experimental Reactor (ITER) NBI system comprises five stages, where each stage has an inverter-type power supply with an output voltage of 200 kV. This paper investigates the inverter-type power supply based on neutral point clamped three-phase three-level (TPTL) inverter and three-phase step-up transformer, which is equivalent to an insulated TPTL dc–dc converter connected with a dual dc link. In order to design a preferable controller for the inverter-type power supply, the topology and principles of the TPTL dc–dc converter with duty cycle modulation have been analyzed. It indicates that only when the converter operates at a large duty cycle, the output voltage ripple can be limited to ±5%. Hence, the small signal model of the converter at a duty cycle larger than 2/3 is established. Following the mathematical model, a single-loop PID controller has been designed and a 400 V/6 A prototype has been built. Simulation and experimental results verify the correctness of the theoretical analysis. The system achieves a lower output voltage ripple and fast dynamic response. [ABSTRACT FROM AUTHOR]

Nuclear fusion reactors, such as the tokamak in the International Thermonuclear Experimental Reactor (ITER) project, usually involve extremely sophisticated high-voltage power supply systems, which provide exciting research challenges. In the short term, the major challenges in power supplies of the ITER and other fusion reactors include the following: 1) fast current control of vertical stabilization (VS) coils and 2) dynamic compensation of reactive power and harmonics. In the long term, the power supply systems in fusion reactors provide opportunities for optimizations at both component and system levels. In this paper, modular multilevel converters (\M^2\LCs) are adopted to tackle the short-term challenges. Circuit structures, pulsewidth-modulation methods, and fault-tolerant operation strategies are presented. The configuration and control strategies of \M^2\LC in VS coils are fully studied and verified with real-time simulations. Compared with existing circuit solutions in fusion reactors, the \M^2\LC -based circuits will have better dynamic response, higher reliability, smaller footprint, and reduced weight. As an outlook to the long-term developments of the fusion power supplies, comprehensive real-time simulations are also discussed. Furthermore, as the future development direction of power electronic devices, the wide band gap devices are discussed at the end of this paper. [ABSTRACT FROM PUBLISHER]

This paper describes the studies performed to identify a suitable design solution for the power supply of the residual ion dump for neutral beam injectors (NBI) of International Thermonuclear Experimental Reactor (ITER). A novel approach has been proposed based on the series of two power supplies, one to produce the average output voltage and one devoted to the generation of the required ac component. The paper is focused in particular on the schematic circuit adopted to generate the alternating component that is meant to use floating capacitors to produce a trapezoidal voltage component superimposed to the dc one. [ABSTRACT FROM PUBLISHER]

An electromagnetic launcher (EML) or railgun is a complex dynamically coupled system, with interacting electric, magnetic, mechanical, and thermal subsystems. Part 1 of this paper formulated a bond graph model of an EML system, including power supply, dynamics of power cables, electric dynamics of armature and rails, magnetic containment of flux, electric contact resistance between sliding armature and rails, generation of forward longitudinal motion, transverse contact mechanics of armature sliding on rails, thermal analysis of armature heating, and model of armature melt wear and plasma erosion. Using state equations extracted from the Part 1 paper, numerical simulation results of the Institute of Advanced Technology's MCL EML are presented. Simulated are rail current, armature forward motions, armature–rail contact normal approach, armature and interface temperatures, and material loss. Results are compared to MCL shot 185. The results suggest interface temperatures of thousands of kelvins, which can exceed 15 000 K under certain conditions, and an armature–rail sliding contact separation due to accumulated melt erosion, consistent with transition. [ABSTRACT FROM AUTHOR]

For the generation of short high-power pulses in many applications, power modulators based on capacitor discharge are used, where the peak power is drawn from the input capacitor bank. In order to continuously recharge the energy buffer during operation at a lower average power, usually, power supplies connected to the mains are used. Due to the worldwide variation in mains voltages and the desired ability to adapt the capacitor voltage of the modulator, the power supply has to support a wide input and output voltage range, whereby the supply should draw a sinusoidal current from the mains due to EMI regulations. Additionally, depending on the modulator concept, a galvanic isolation also has to be provided. In order to achieve the mentioned specifications for the considered power supply, a combination of an ac–dc and a dc–dc converter is proposed, whereas the mains voltage is rectified by a three-phase buck–boost converter to 400 Vdc, and thereafter, an isolated dc–dc converter charges the input capacitor bank of the power modulator up to 3.5 kV. This paper focuses on the basic operation and the design of the 3.5-kV/11-kW isolated dc–dc converter, which includes transformer design, efficiency-volume optimization, and component selection. In this paper, compared with the well-known flyback converter, the proposed full-bridge-based topology results in a much higher efficiency and power density. [ABSTRACT FROM PUBLISHER]

To study the lighting shielding of ultrahigh voltage (UHV) transmission lines across mountains and the hillside effects on discharge process, experiments have been carried out with a reduced scale tower model. As the spatial electric field is changed by the slope, the space of shielding failure is enlarged. When the high-voltage electrode is 5 m to the transmission line, the vertical length of shielding failure is 8 m for the 30° slope, which is larger than 5.17 m for the flat ground. The maximum probabilities of striking the lines are 95% for the slope and 75% for the flat ground. When the vertical distance from the high-voltage electrode to the hillside is less than that to the transmission lines, the probabilities of discharge striking the flat ground are 85% for the 5-m gap and 94% for the slope for the same gap. When the vertical distance from the high-voltage electrode to the hillside is equal to that to the flat area, the hillside does not affect the average discharge voltage apparently but discharge time and discharge dispersity. The results of this paper are valuable for lighting protection of UHV transmission lines in mountainous areas. [ABSTRACT FROM PUBLISHER]

The superconducting inductive pulsed-power supply (SPPS) circuit consists of a high-temperature superconducting pulsed-power transformer (HTSPPT) and an auxiliary capacitor. The electrical losses and the power of the primary source can be cut down with the superconducting inductive energy storage. Although its energy density is slightly less than a purely superconducting inductive system, it can reduce the maximum voltage of the opening switch by the capacitor and achieve a high degree of current amplification factor. However, during the discharge process, the magnetic leakage flux energy stored in the primary of the HTSPPT requires the capacitor to have a certain capacity. The higher the ratio of the capacitive stored energy over the total inductive stored energy, the more the dominant position of inductive energy storage reduces. The current amplification factor ( \gamma ), the maximum voltage of the opening switch ( V_{S\max } ), and the ratio of capacitive stored energy ( \eta ) are the three main properties of the SPPS circuit, which depends on several intertwined critical parameters, such as the inductance ratio n = L2 /( L2+LL ) and the capacitance ( $C_{{\mathbf {1}}}$ ). This paper studies the influence of the critical parameters on the main circuit performance with a 1-kJ SPPS system. The detailed selection method of the critical parameters for the specific system is also discussed with a coupling coefficient of 0.95. Such a system is easy to be utilized for the basic experimental study of a small railgun. [ABSTRACT FROM PUBLISHER]

For a relativistic backward-wave oscillator (RBWO), various nonstationary phenomena, such as irregular transients, mode competition, self-modulation, and chaos, are typical. Phase locking by injection of the external signal helps to minimize transient times and to stabilize a single-frequency regime of operation. In this paper, phase locking of an RBWO with end reflections is considered. The results of time-domain numerical modeling are presented, which reveal an intricate pattern of the phase-locked operation. In particular, a possibility of rapid frequency switching by RF priming is demonstrated. [ABSTRACT FROM PUBLISHER]

This paper reports on the study of physical processes in a high-current vacuum arc shunted by semiconductor elements. The switching dynamics between a vacuum circuit breaker (VCB) and an assembly of several semiconductor elements connected in parallel to the VCB is investigated. The breaking capacity of a VCB-thyristor system is analyzed. It is found that at the instant of current switching, the arc can operate at a rather low voltage of 8–10 V. It is shown that there exists a certain limiting mode close to the conditions for current switching. In this mode, at least two cathode spots are observed. [ABSTRACT FROM PUBLISHER]

For electromagnetic emission applications that need a very high amplitude and an appropriate pulsewidth, a pulsed power supply based on multiple high-temperature superconducting pulsed power transformer (HTSPPT) modules is verified in this paper. First, the working processes of multiple HTSPPT modules are analyzed and two small experimental HTSPPTs are described in detail. Then, simulation is carried out to show the major pulse characteristics of two different discharge methods. To verify the feasibility of two discharge methods, high-current testing is carried out with the two HTSPPTs. The results show that a higher amplitude of current pulse can be achieved using synchronous parallel discharge and a larger pulsewidth of current pulse can be achieved using asynchronous parallel discharge. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate an influence of high-frequency high-voltage impulse conditioning on the back-to-back capacitor bank switching performance of vacuum interrupters (VIs). Nine identical 7.2-kV VIs were tested by 80 CO operations after the proposed conditioning. Test inrush currents were set to 0-, 2-, and 5-kA peak. The experimental results showed that this conditioning technology could make an impact on both prestrike and restrike characteristics of VIs. The complementary cumulative distribution function (CCDF) of the prestrike gap d\textrm {pre} followed complementary Weibull distribution. In contrast to VIs without conditioning, three typical prestrike gaps, i.e., CCDF 10% prestrike gap d\overline {10} , CCDF 50% prestrike gap d\overline {50} , and CCDF 90% prestrike gap d\overline {90}\vphantom {\sum RRR} , decreased by 39%, 19%, and 4% at most, respectively. Besides, the scattering of d\textrm {pre} decreased by 52% at most. Furthermore, the conditioning technology had an influence on the feature of restrike waveform through variation of field emission current. It could also reduce the restrike probability by 22.5% at most and made the entire restrikes occur between $0.5T$ and $5T$ during recovery voltage period ( $T=20$ ms). [ABSTRACT FROM AUTHOR]

The spark gap switch is the key element in any pulsed power system, which directly determines the pulse repetitive frequency of the system. The dielectric recovery data of the spark gap play a basic role, but they have not yet been adequately studied for repetitive pulse charge conditions. This paper describes some of the factors that affect the recovery of spark gap switch for pulse-charged operation. A two-pulse technique has been used, in which the first pulse is applied to the spark gap to overvolt the gap and initiate the breakdown and the second pulse is used to determine the recovery voltage of the gap. The effects of electrode size, pulse rise time, and conduction current on the spark gap recovery performance are presented. Experiments were performed by using a double-pulse generator capable of generating 40-kV pulses with a delay of 1 ms–1 s. Spark gap electrodes of 34-, 40-, and 68-mm diameters and a point type were used in the study. The effect of voltage rise rate was studied by changing the charging capacitor to 100, 500, and 1000 nF in the circuit. An intermediate plateau was observed in the spark gap recovery curves. In addition, an increase in the output impedance resulted in a decrease in the time taken for the recovery of the spark gap. Also, the switch recovery appears to be largely dependent on the electrode shape and size compared with the pulse rise time. [ABSTRACT FROM AUTHOR]