Search

This paper provides analysis of experiments aimed at defining the capabilities of plasma opening switch (POS) for energy transfer to a load of inductance comparable with the inductance of the energy store vacuum section. The analysis is performed using the substantiated technique that allows quantitative estimation of the POS efficiency. Under the same conditions with a conduction current of ∼1 MA and POS voltage of ∼1 MV, the energy transferred to the load depends strongly on the transmission line design. When the electrode gap in the line is ∼1 cm, the energy delivered to the load is ∼40 kJ. Increasing the gap to ∼4-cm increases this energy to ∼100 kJ. [ABSTRACT FROM PUBLISHER]

Fe-based nanocrystalline (FE-N) cores are widely used in pulsed-power and power electronic systems. In this paper, FE-N cores with high and low residual flux were tested and compared under single impulses. The loss density and permeability of the two FE-N types are evaluated in the usable flux swing range of \(\sim 0.0\) –1.4 T, and a range of magnetization rates of \(\sim 1.0~\mu \) s–6.0 T/ \(\mu \) s. When the loss density and average relative permeability are evaluated for magnetization from initial point to positive saturation based on the initial magnetization curves, the FE-N with low residual flux has lower loss density and larger average relative permeability than the one with high residual flux under low magnetization rates. The loss density and average relative permeability of the two FE-N types are almost the same values under high magnetization rates. The application of the measured results in magnetic switch design and performance analysis is presented. The presented results of the two FE-N cores can be aided in the practical magnetic designs of magnetic switches, pulse transformers, and inductors, but not restricted to those. [ABSTRACT FROM PUBLISHER]

Since bipolar high-voltage pulses is more effective in the treatment of air purification, water treatment, and other applications than unipolar pulses, a newly developed bipolar high-voltage rectangular pulse adder is proposed with a new control strategy. The structure of the all solid state pulse adder based on the half-bridge structure has been improved by changing the driving signal of the MOSFETS in the main circuit to obtain high-voltage rectangular narrow pulses. Magnetic ring transformers with a common primary winding and rectifiers were employed to charge capacitors under a high frequency. Improved phase shift control strategy is proposed, which makes it possible to generate unipolar or bipolar pulses with or without chopping off over resistive and capacitive loads. The bias voltage in the pulse removed and the size of magnetic cores is reduced. A nine-stage laboratory prototype is assembled. Experimental results show that unipolar and bipolar rectangular pulses with an amplitude of 4 kV, frequency of 12 kHz, pulsewidth of 600 ns– $4~\mu \text{s}$ , and rise time of 80 ns are obtained over different loads. [ABSTRACT FROM AUTHOR]

A compact magnetic pulse compression (MPC) topology with only two magnetic cores and a continuous repetition rate of 20 kHz is presented. The demand for higher average output powers of pulsed power systems can be achieved by an increase of the pulse rate frequency (PRF). The PRF is often limited by the switching speed or recovery of the main switch and also the complex behavior of the magnetic materials. With the advent of insulated gate bipolar transistors and the nanocrystalline soft magnetic material, PRFs of tens of kilohertz are feasible if a suitable MPC topology is applied. The presented MPC is based on an existing topology that has been significantly improved to enable high-frequency pulse generation. A design method using 3-D magnetostatic and transient magnetic simulations is introduced to enable optimization of the magnetic switching components. A 20 kHz, 60 kV, and 52 ns full width at half maximum (FWHM) MPC generator is designed, built, and tested for a $100~\Omega $ load. Simulations suggest that a PRF up to 50 kHz is achievable, but continuous operation will likely be limited by thermal management. [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]

In this paper, a novel six-channels annular plasma-jet chamber is designed and embedded in the trigger electrode of the three-electrode gas switch to generate multichannel plasma jets without air flow, which is used to trigger the gas switch to form multichannel discharge. Results of this paper show that the plasma-jet triggering can be conductive to steady formation of multichannel discharge. [ABSTRACT FROM PUBLISHER]

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]

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]

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]

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 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]

A new design of powerful high-voltage high-current impulse source for nanosecond megavolt charging of short forming lines (SFLs) is proposed. The first stage of the device is based on inductive energy storage. It accumulates energy supplied by the current of magnetic flux compression generator (MCG), whereas the electro-explosive opening switch is used for the energy output into intermediate SFL. In the second stage, we use a Tesla transformer with oil insulation. The results of the earlier experimental study of submegavolt charging of intermediate forming line as well as the results of calculations of the two-stage facility given in this paper demonstrate the feasibility of the device based on MCGs for nanosecond charging of SFL up to about 3 MV. [ABSTRACT FROM PUBLISHER]

Vacuum surface flashover switch is a promising technique scheme of high repetitive frequency fast-closing switch applied to dielectric wall accelerator. In this paper, the switch is experimentally investigated, and a nanosecond pulse with 2.02-ns effective rise time is obtained. For a cylinder-fused quartz dielectric, the breakdown field of the switch is near 55 kV/cm, and the value for the frustoconical-shaped dielectric exceeds 120 kV/cm with a lifetime up to 69000 discharges. The repetitive frequency ability of the switch is better than 100 Hz, and the breakdown voltage increases slightly with higher frequency. [ABSTRACT FROM PUBLISHER]

In this paper, we investigated a water treatment method that sprays waste water droplets into a pulsed discharge space. To increase energy efficiency of this method, a pulsed power generator should output a pulsed power of a high peak and a short pulse width and be low circuit loss, high repetition rate, high power, and high stability. An inductive energy storage circuit using a semiconductor opening switch was studied to satisfy the above-mentioned requirement. Initially, effect of turn ratio of a pulse transformer (PT) in the circuit was investigated. Energy transfer efficiency and the pulsewidth of the output voltage increased with the PT turn ratio, resulting in an increase of the efficiency of the water treatment system. Then, the effect of the load impedance was investigated. The result showed that an optimum resistance to maximize the efficiency exists. From these results and a previous experimental report, we concluded that the optimization conditions are summarized below. The turn ratio and the inductance in the secondary circuit should be as high as possible under the condition, which does not output the very long pulse. The impedance of the discharge at an electrode for the water treatment should be a value that maximizes the energy transfer efficiency. Capacitance of capacitors in the circuit should be adjusted to obtain optimal peak voltage for the generation of active species. [ABSTRACT FROM PUBLISHER]

An X-band switched energy storage (SES) microwave pulse compression system is presented, and its theoretical analysis, numerical simulation, and experimental research are carried out. Detailed dimensions of the resonant cavity are theoretically calculated and numerically optimized by simulation. The operation mode of the resonant cavity is TE1,0,52 at the frequency of 9.3 GHz. The output power gain is theoretically calculated as 11.7. When the width of the rectangular coupling iris is 11 mm, the coupling coefficient is 1.05, which is beneficial for high energy storage efficiency. In the preliminary experiments, the output microwave with power of 350 kW and pulsewidth of 10 ns is produced by the SES pulse compression system under the input power of 54 kW, implying a pulse power gain of 6.5. [ABSTRACT FROM AUTHOR]

A low inductance three-electrode field-distortion gas switch (TFGS) used for linear transformer drivers (LTDs) is developed and tested. Based on the experimental platform, the short-circuit inductance of a brick which consists of two 100-nF capacitors connected electrically in series with the TFGS is measured to be less than 151 nH. By changing the electrode materials, the self-breakdown and triggering characteristics of the TFGSs and the pollution on insulators are compared, respectively. The results show that when the main electrodes are made of WNiFe and the trigger electrode is stainless steel, the TFGS shows relatively excellent performance. When the self-breakdown voltage is about ±90 kV, the standard deviation is less than 4 kV; for a charging voltage of ±80 kV and by operating at 60% working coefficient, the jitter of the TFGS is 1.6 ns while triggered by a −120-kV pulse, and there is no prefire and no-fire when the TFGS operates continuously over 1000 shots. [ABSTRACT FROM AUTHOR]

The characteristics of gas discharge are closely related to the features of high-voltage pulses, especially to the rising and falling time of pulse. A parameterized pulse control method based on improved Marx generator is proposed to obtain parameterized nanosecond high-voltage pulses to match different discharge circumstances. Different parameters of nanosecond pulses are realized in real time by parametrical modulating timing sequences of switches in an improved Marx generator. Experimental results indicate that the ability of generating pulses is with 0–20 kV amplitude, 0–1 ms width (flat top), 50–500 ns or faster rising/falling time, below 5% overshoot, and a maximum 5 kHz repetitive frequency at 20 kV on a matched 0–100 pF capacitance load. The shape of pulse waveform including triangular, rectangular, or the combination of the two kinds of pulse waveform can be achieved. The discharge characteristics in the dielectric barrier discharge device driven by the parameterized pulse, especially changing the rising time of pulse, are investigated. The uniform discharge is observed, and the discharge intensity is doubled while reducing the rising time of pulse from 500 to 50 ns, and the intensity of the N2 spectrum increased to 2.5 times. [ABSTRACT FROM AUTHOR]

An understanding of the electrostatic interaction between charged electrical conductors embedded in a grounded cylinder is quite useful in the design of compact pulse generators. We get the complete solution for capacitance between the two spheres and the capacitance between the sphere and the grounded cylinder in series form. The dependence of these capacitances on various geometrical parameters is very useful in the design phase of Marx generators where the stray capacitances play crucial roles. [ABSTRACT FROM AUTHOR]

The rapid-fire railgun (RAFIRA) is a railgun, which can be operated in multishot mode. However, so far, the number of shots in a multishot experiment was limited to two shots per experiment. That is why RAFIRA was adapted electrically and mechanically and multishot experiments with shots 2, 3, and 5 per experiment were performed. In these experiments, fire rates between 40 and 80 Hz and muzzle velocities up to 1700 m/s were achieved. [ABSTRACT FROM AUTHOR]

The gyrotron is a critical component of electron cyclotron resonance heating systems and is highly sensitive to the rising edge of the cathode’s high-voltage power supply (HVPS). HVPS is based on pulse-step modulation technology, which requires a rapidly rising edge and low-voltage overshoot. An equivalent mathematical model is thus established to analyze the transient characteristics of HVPS. An optimized control strategy is obtained from detailed theoretical calculations verified via simulations. A time interval of $1 ~\mu \text{s}$ is used to ensure that the voltage overshoot is controlled to within 1% over the rated output voltage range. Finally, the theoretical analysis is verified through experimental tests. [ABSTRACT FROM AUTHOR]

The investigation of a high output power, arc lamp exciplex ultraviolet (UV) source for pulsed power applications is presented. The arc lamp generates up to 550 W from XeF* exciplex radiation at 351 nm, totaling to nearly 0.15-mJ total radiated UV energy over the duration of the UV pulse. With an ellipsoidal reflector, the arc lamp produces 400 W/cm2 and up to 0.1 mJ of UV light onto a 1-cm2 area. A complete experimental investigation of the arc lamp for both XeCl* (308 nm) and XeF* (351 nm) exciplex sources operated under varying excitation and pressure conditions is reported. As an application, the arc lamp is successfully utilized as an illumination source for an intrinsically triggered, wide bandgap SiC photoconductive semiconductor switch (PCSS), where a PCSS ON-state resistance of $500~\Omega $ is achieved. [ABSTRACT FROM AUTHOR]

A technology scheme that replaces Marx generator with Tesla transformer was put forward to improve the reliability of the pulsed power system. In order to validate the technology scheme, a Tesla transformer was designed and tested. The excitation of the primary consists of two 4- $\mu \text{F}$ polypropylene film capacitors which are separated by a three-electrode field distortion gas switch. A deionized water dielectric pulse forming line (PFL), with 13-nF equivalent capacitance, acts as the secondary capacitor. The actual transformation ratio is 9.7 approximately, and the PFL voltage is as high as 1.2 MV when two capacitors are charged to ±62 kV by the bipolar high-voltage direct current. The prefire probability of switch is described by the Weibull distribution and the working ratio of the switch is elaborately chosen so as to balance the prefire probability and the trigger jitter. For ±62 kV charge voltage and 0.2-MPa pressured air dielectric, the prefire probability of switch is only $1 \times 10^{-7}$ and the jitter of that is 5 ns. When confidence is 0.90, the failure probability of pulsed power machine is $2.8 \times 10^{-4}$ according to the Binomial distribution correspondingly. [ABSTRACT FROM AUTHOR]

Experimental observation and numerical simulations of sub-nanosecond avalanche switching of Si and ZnSe bulk semiconductor structures initiated by high-voltage pulses with steep (dU / dt > 10 kV/ns) ramp are reported. The measured switching time is ~100ps. The switching is sustainable and repetitive and has negligible jitter. Comparison of the experimental and numerical results suggests that after switching, the whole volume of the structure is uniformly filled with nonequilibrium electron–hole plasma. [ABSTRACT FROM AUTHOR]

A pulsed-dc discharge method for plasma chemical vapor deposition (CVD) was developed using a constructed versatile pulsed-dc generator and a vacuum discharge chamber. Argon (Ar) gas discharge experiments were performed under a variety of discharge conditions, and plasma conditions were evaluated using optical emission spectroscopy. The developed system can perform glow discharge by employing nearly rectangular, unipolar, and high-voltage negative pulses with a wide variation of voltage amplitudes and a set discharge current, pulse repetition rate, and duty cycle. Plasma conditions could also be tuned by varying the pulse parameters. A preliminary test of the deposition of diamond-like carbon (DLC) films on silicon (Si) substrates and ultrathin pyrolytic carbon (PyC) films on nanothickness metal-catalyzed glass substrates was performed with acetylene (C2H2) by selecting some typical deposition conditions based on the gas discharge experiments. The deposited films were characterized via Raman spectroscopy. The characteristic properties of DLC and PyC films were achieved. The DLC films demonstrated conventional hard insulating properties while the ultrathin PyC films exhibited conductive and semitransparent properties. These results revealed that the developed pulsed-dc discharge system for plasma CVD is applicable for the synthesis of insulating hard as well as soft conducting carbon thin films. [ABSTRACT FROM AUTHOR]

The operation of transistorized Marx-bank circuits (MBCs) is analyzed, and physics-based modeling is used to understand the anomalous switching behavior of the first stage single trigger avalanche transistors of MBCs at high-current-injection conditions. The role of a voltage trigger pulse having variable rise time when applied to the base terminal is investigated to model the underlying physics of the anomalous switching behavior. Experimental observations related to ultrafast anomalous switching mechanisms of trigger transistor, i.e., either primary breakdown or current mode secondary breakdown, for faster and slower base drives are presented. This demonstrates the importance of the dynamic avalanche process and reverse saturation current on the switching mechanism under high-speed base-trigger ramps for different avalanche BJTs from various manufacturers and different lots. The agreement between 2-D TCAD device simulation results and the experimental observations shows the validity of the proposed theory when the base width and mobile carrier recombination rate are used as parameters in the device simulation setup. [ABSTRACT FROM AUTHOR]

The recent availability of fast high-power semiconductor switches makes the transformer coupled LC inversion generator (TCLCG) topology a very promising candidate for the realization of reliable, multi-kHz repetition rate pulse generators with an output voltage in the range of 200 kV and more. Usage of 1:1 transformers instead of closing switches in each generator stage reduces the total number of switches inside the TCLCG to only one, independent of the numbers of stages. Thus, problem of synchronization as in Marx-generators or classical LC inversion generators can be omitted. In principle, capacitors are initially charged to the charging voltage, whereas the odd-numbered of each stage are charged with the opposite polarity to the even-numbered capacitors. Fast voltage inversion of the even-numbered capacitors leads to efficient voltage multiplication provided the semiconductor switching module will be sufficiently fast to minimize switching losses. For initial investigations, a special asymmetrically compensated three-stage test TCLCG was designed and set up. Three high-voltage semiconductor switching modules were experimentally tested in detail; two 20-kV high-voltage switching modules consisting of a series arrangement of 15 Si-based insulated gate bipolar transistors or 15 SiC-based MOSFETs, with in each case 1700-V breakdown voltage, and a fast experimental 10-kV thyristor switching module with kilo ampere current carrying capability. The achievable output signal rise time and generator efficiency for different electrical loads (resistive, capacitive, or inductive) are discussed. [ABSTRACT FROM PUBLISHER]

Two solid-state bipolar Marx modulators are analyzed and compared regarding hold-off semiconductor voltages and open-fault tolerance capability. Normal and abnormal operating conditions are considered, such as switch synchronization mismatches, failures, and open faults. Ten-stage laboratory prototypes of two bipolar Marx modulators have been assembled using 1200-V insulated gate bipolar transistors and matching diodes, to operate at 500-V dc input voltage. Outputs are 4-kV bipolar pulses, 1% duty ratio, into resistive loads, and 1-kHz frequency. Lack of synchronization and open-fault tests confirm that only topologies with redundant switches can operate without semiconductors being subjected to double hold-off voltages while presenting current paths to clear faults. [ABSTRACT FROM PUBLISHER]

In this paper, dc arc characteristics in different high pressure gas atmospheres were studied, both in pure N2 and in mixed gases of 20%N2 and 80%H2 at 5 atm. The experiments were conducted in a demountable arc-quenching chamber with double contacts and a transparent glass shield in a 270 V dc circuit. With a high-speed camera, the arc motion is analyzed. The results indicate that H2 and N2 mixed gases have better performance for dc arc extinguishing. Images of pure N2 and 20%N2–80%H2 mixed gas dc arc appearances are presented. [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]

A 2.3-MV field-distortion oil switch was built and experimentally studied. Based on the JianGuang-I facility in China, an experimental stand was established for tests of the switch. Both static and dynamic performances of the switch were studied in detail. Experiment results show that the switch works well at approximately 2.3 MV with a 350-ns rise time. Field-distortion mechanisms worked well. In addition, the requirements of the trigger-voltage peak were not as rigorous as anticipated. With trigger voltages higher than 75 kV, the switch worked well with no problems. As the trigger voltage increased, the switch-breakdown delay and its jitters decreased rapidly. With a 250-kV trigger voltage, the breakdown delay of the switch was approximately 132 ns. Its jitter (the standard deviation) was as low as 4.4 ns. Finally, electrode erosions of the switch are also presented and analyzed. [ABSTRACT FROM AUTHOR]

For semiconductor-based pulsed power generators, short turn-ON and turn-OFF times of the employed switching elements are especially in hard switching condition of advantage. In order to enhance switching speeds for standard devices under hard switching conditions, we propose a capacitively coupled gate-boosting circuit with gate-drive voltages of up to 80 V. A low inductance test circuit has been set up to evaluate different switching elements under varying driving conditions. Beside single pulse operation, the setup allows for burst mode and continuous repetitive switching. The flexible design of the setup allows for testing metal–oxide–semiconductor field-effect transistors (MOSFETs) as well as insulated-gate bipolar transistors (IGBTs). Exemplary, we show results for a SiC MOSFET and a standard IGBT. By applying 80 V gate-drive voltage, the current rise rate of the SiC MOSFET could be increased by a factor of 3.5 up to 2.6 kA/ \mu \texts . For standard IGBT devices, we achieved an eightfold increase in current rise rate up to 4.2 kA/ \mu \texts . We verified a reproducible pulse shape for over \textrm 10^\textrm 8 pulses. In addition, the gate-drive circuit is able to drive the device in 3-MHz burst mode at 250 A peak collector current. [ABSTRACT FROM AUTHOR]

To carry out cell experiments for the pulsed magnetic field treatment of tumor cells, a high dB/dt pulsed magnetic field generator based on a printed circuit board (PCB) Archimedes spiral coil and a self-breakdown air switch is developed. The magnetic field and the induced electric field around the Archimedes spiral coil are calculated. Using COMSOL Multiphysics software, the magnetic field distribution characteristics of the coil are optimally designed. Then, the performance of the generator is measured. Ultimately, the PCB Archimedean spiral coil has seven turns, and it has a diameter of 21 mm. The coil can produce the following pulse magnetic field parameters in a cell culture liquid: an amplitude of 0.92 T, a rise time of 78 ns, a pulsewidth of 1.8 \mu \text{s} , a rate of magnetic field change that reaches 1.1\times 10^{7} T/s, a maximum-induced electric field of 55.9 kV/m, a degree of electric field uniformity of 84%, and a maximum-induced current density of 1.7 \times 10^4 A/ \textm^2 . The coil can be used to deliver pulsed magnetic field and induced electric field to biological objects. [ABSTRACT FROM AUTHOR]

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]

The observations of the evolution of dust clouds in afterglow plasmas at various neutral pressures are presented. Four cases were studied which showed a large variation in the cloud dynamics. In two cases, the clouds responded by rapidly shedding an outer layer of dust. In another case, the entire cloud exhibited a nearly uniform expansion—Coulomb explosion. In perhaps the most exotic case, the cloud splits into two clouds—Coulomb fission. The results for the case of the Coulomb expansion were compared with a theoretical model that included the effects of neutral drag. [ABSTRACT FROM PUBLISHER]

The importance of low-voltage devices to interrupt dc currents under load and fault conditions has been considerably growing recently. From experimental work, it is known that arcs in strong transverse magnetic fields are able to generate arc voltages high enough to interrupt such circuits. To study the mechanisms behind this process, 2-D simulations of the plasma fluid flow in arc chambers, coupled with current flow and magnetic field, were carried out with a Multiphysics FEM program. For arc chambers, where the arc is pressed against a wall, it could be shown that the power removal that determines directly the arc voltage per unit length occurs predominantly by convection in the $J\times B$ force field (electromagnetic pump). In this sense, hydrogen is much more effective than air. In a similar way, this mechanism can also explain the effect of strong magnetic blow fields in arcs with free environment. [ABSTRACT FROM PUBLISHER]

In recent years, all-solid-state high-voltage pulse generators have been widely used in irreversible electroporation for tumor ablation technology. However, high voltage may cause the breakdown of loads that leads to short circuits. The short circuit of loads will generate high short-circuit currents that will affect the performance of semiconductor switches. To improve the reliability and lifetime of solid-state pulse generators, a passive synchronous isolated gate drive circuit with short-circuit protection based on decreasing the gate–source voltage is proposed in this article. To verify the overcurrent protection during the breakdown of loads, a solid-state Marx generator prototype using the drive circuit was built and tests were carried out. The experimental results show that the 205-A short-circuit current was clamped with 90 A in less than 500 ns, while the transient voltage can be neglected. Besides, the response time, the maximum transient voltage, and the maximum current amplitude can all be adjusted. [ABSTRACT FROM AUTHOR]

Impulse bits produced by conical theta-pinch inductive pulsed plasma thrusters possessing cone angles of 20°, 38°, and 60°, were quantified for 500-J/pulse operation by direct measurement using a hanging pendulum thrust stand. All three cone angles were tested in single-pulse mode, with the 38° model producing the highest impulse bits at roughly 1-mN-s operating on both argon and xenon propellants. A capacitor charging system, assembled to support repetitively pulsed thruster operation, permitted testing of the 38° thruster at a repetition rate of 5 Hz at power levels of 0.9, 1.6, and 2.5 kW. For similar conditions, the average thrust measured during repetitive-pulse operation exceeded the value obtained when the single-pulse impulse bit is multiplied by the repetition rate, suggesting that a greater impulse bit per pulse was produced when operating in the repetitive-pulse mode. [ABSTRACT FROM PUBLISHER]

In the use of spark gaps as switching devices in pulsed power systems, spark resistance is a crucial factor influencing the voltage rise time and the efficiency of energy delivered to the load. However, current oscillations make it difficult to accurately measure the spark resistance. Therefore, we present a spectrographic method to measure the spark radius and the conductivity of spark channel according to its emission spectrums. A series of experiments has been carried out to investigate the time-dependent properties of spark resistance under oscillatory damped current pulses. The current and voltage waveforms have been recorded to calculate the energy deposited in the spark channel. Furthermore, the influences of gas pressure and gap length on spark resistance and the deposited energy have been discussed. The results indicate that lower resistance, and energy deposition is obtained with shorter gap lengths operating at higher pressures. [ABSTRACT FROM PUBLISHER]

The results of comparative studies of two compact generators of nanosecond high-voltage pulses are presented. Both generators include an opening switch in the form of a block of drift step-recovery diodes (DSRDs) and a closing switch in the form of a block of shock-ionized dynistors (SIDs). The generators are designed according to two different schemes, but they have similar parameters of the output pulses on a load of $50~\Omega $ : the amplitude of the output voltage is ~ 30 kV, its rise time is ~ 3 ns, and the output energy is ~ 0.4 J. It is shown that it is possible to increase the output voltage and output energy of the generators. [ABSTRACT FROM AUTHOR]

This paper demonstrates for the first time the use of microplasma to perform AND, OR, and XOR logic operations. The logic circuits are implemented similar to diode-resistor logic. Output voltages are in the range of \(5-40\) V and can be modified by varying the load resistor. The active area of the microplasma device is just \(50~\mu \) m \(\times 5~\mu \) m. The small interelectrode gap kept breakdown voltage to \(\sim 250\) V when operated in He gas at atmospheric pressure. The use of plasma as a source of free carriers is also demonstrated, with free carriers available up to 500- \(\mu \) m away from plasma. [ABSTRACT FROM PUBLISHER]

The development of pulsed power puts forward new requirements on volume and weight of generators. To develop a compact and lightweight high-voltage pulse generator, this work proposed a new modular pulse forming topology with high voltage gain and a reduced number of energy storage capacitors. The topology is realized by charging a set of capacitors cyclically step-by-step and discharging repetitively in series. A voltage gain of $2^{n-1}$ can be achieved with $2n\,+\,1$ all-solid-state switches, $n$ fast recovery diodes, and n capacitors. An experimental prototype built around five capacitors generates high-voltage pulses with adjustable voltage level, pulse frequency, and pulsewidth. Meanwhile, it is verified that the prototype has a certain capacity with a capacitive load. [ABSTRACT FROM AUTHOR]

A 4-MV self-triggered switch based on ultraviolet (UV) illumination technology is designed and tested under approximate 800-ns rise time pulse voltage. The switch is composed of five sections in series, and each section comprises an UV-illuminating gap (UV gap) and a main gap. The voltage charged on the UV gap is obtained by a resistance–capacitance coupling circuit, which enhances synchronization with the main gap voltage. The gap distance of the 4-MV switch is determined according to the performance of the same type of switch under a shorter pulse (about 300 ns), while the characteristics of the gap under 800-ns pulse voltage is still unclear. The experimental results show that low jitter breakdown of the switch can be realized effectively when two UV gaps are functioning. The breakdown jitter percentage achieves less than 1.55% within the range of 1.0–3.2 MV. When the working scope is narrowed down to 1.4–2.1 MV, the breakdown jitter is less than 1%. [ABSTRACT FROM AUTHOR]

Long pulse gas lasers utilizing double-discharge circuits are different from the single-short pulse gas lasers in that they do not require all of the desired energy to be deposited into the peaking capacitors prior to ignition of the main gap. Instead, the majority of the energy is held in another capacitor that is then discharged in the form of a longer duration discharge pulse output compared with that of single-short pulse lasers. Extended stability of the discharge is typically achieved by igniting the main gap discharge at higher ignition voltages. Several double-discharge circuit topologies exist in the literature. However, each topology has its own disadvantages primarily centered around the components needed and the resulting complexity. In this article we introduce the application of the new hybrid circuit pulsed power topology as a double-discharge circuit with high ignition voltages. The hybrid circuit pulsed power topology was originally published by the authors of this article in their previous publication titled “A New Hybrid Pulsed Power Circuit Topology for Gas Laser Applications.” The advantage of the hybrid circuit as a double-discharge circuit is that it does not require any special device [e.g., semiconductor opening switch (SOS) diode] and can use commonly available components. [ABSTRACT FROM AUTHOR]

Marx generators are widely used to produce transient high-voltage pulses. The evolution of semiconductor devices and power electronics concepts promotes the development of solid-state Marx generators (SSMGs) and enables them with flexible pulse modulation ability. First, this article sorts out the evolution of SSMGs topologies chronologically. We can see that how the energy efficiency of SSMGs is considerably improved by replacing resistors with diodes and switches and how square-wave pulses are generated by SSMGs based on half-bridge structures. Unipolar and bipolar pulses can be easily produced with different SSMGs. Second, we discuss the influence of rated voltage and rated power of present semiconductor switches on the performances of SSMGs since switches are the key components in pulse generators. To reduce the size and weight of SSMGs, metal–oxide–semiconductor field-effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs) with small packages are preferable. Third, synchronous isolated driving of switches as the crucial technique in SSMGs is introduced. Different methods of providing synchronous signals and isolated power to various stages in SSMGs are illustrated. Fourth, the performance including load capacity, droop compensation, waveform modulation, and self-triggering of SSMGs is discussed. In the end, the developing trend of SSMGs is given. [ABSTRACT FROM AUTHOR]

C5-fluoroketone (CF3C(O)CF(CF3)2, abbreviated C5-FK) and C4-fluoronitrile [(CF3)2CFCN, abbreviated C4-FN] mixed with background gases such as carbon dioxide, oxygen, or air are used as alternatives to SF6 as the insulating and switching medium in high voltage gas insulated switchgear (GIS) due to their good switching and dielectric insulation performance and comparably low global warming potential (GWP). Like SF6, C5-FK and C4-FN are chemically stable inside electrical equipment and non-flammable. Like most complex molecules, they decompose exothermically when exposed to sufficiently high temperatures and do not recombine after decomposing. In this work, we use a custom-built test device to experimentally investigate the conditions and gas compositions under which a decomposition reaction can proceed to completion in C5-FK- and C4-FN-based gas mixtures after being initiated by an electric arc. We also present the related theory. The results show that, for properly selected mixtures, even under extreme failure conditions—internal arc faults—complete decomposition of the C5-FK or C4-FN does not occur. [ABSTRACT FROM AUTHOR]

This article describes the performance of a multi-gap, multichannel (MGMC) spark gap switch, evaluated numerically and experimentally, to achieve multichanneling using a relatively low-magnitude trigger pulse. First, an electrostatic analysis of the switch geometry was carried out using COMSOL Multiphysics 5.5 to determine the electric field distribution during high-voltage hold-off before triggering and to determine the coupling parameters between trigger and other intermediate electrodes of the switch. Second, a circuit model was developed in PSpice Lite 16.6 for predicting the process of channel formation and its influence on adjacent channels. Based on the simulation results obtained, a six-gap, eight-channel, planar MGMC switch operating in air has been designed and developed. The developed switch was, then, incorporated into a compact experimental setup to experimentally evaluate various switch parameters such as inductance, switching delay, jitter, and closing time when triggered using a negative-polarity trigger pulse of magnitude −40 kV, generated using a compact, in-house developed trigger generator. In contrast to most of the reported MGMC switches that use complicated Marx-based generators to produce ≥120-kV trigger pulses for multichannel formation, the experimental results, thus obtained, report comparable switch performance using a low-magnitude (−40 kV) trigger pulse. In addition, framing and streak camera images taken during the current discharge indicate the presence of ~6 luminous channels. In addition, short-circuit experiments for estimating switch inductance by consecutively shorting one or more channels also indicate multichanneling in the switch using a low-magnitude trigger pulse. [ABSTRACT FROM AUTHOR]