Search

Railguns are current-driven guns that allow reaching large muzzle velocities and energies. In the military context, the long-range artillery scenario makes use of these two capabilities to enable the launch of hypervelocity projectiles to target distances above 100 km. As of today, the most advanced railgun project is conducted by the Office of Naval Research, Arlington, VA, USA, and features railguns with a muzzle energy of 32 MJ. Such large artillery railgun systems with efficiencies above 30% are fed by a pulsed power system with a nominal energy content of about 100 MJ. In contrast to this, experiments with French-German Research Institute’s (ISL) most powerful railgun, PEGASUS, have reached muzzle energies of 2 MJ, only. The nearer future ISL has to answer two questions: 1) is the railgun technology adequate for a long-range artillery scenario? 2) can the railgun launch a hypervelocity projectile which is being developed by other groups in ISL? To do so and to support the development of the hypervelocity projectile, a larger railgun installation with a significant increase of the energy and free flight capability is required. In this paper, three different railgun systems were investigated using an electric circuit simulation code. The systems are referred to by the energy being stored in the capacitors as 25, 50, and 100 MJ. The aim of this paper is to investigate what masses can be accelerated to the relevant velocity range for the long-range artillery scenario by these different primary energies. The results of this paper can be used to aid the decision about the required size, with respect to the military scenario, of a potential future railgun system. [ABSTRACT FROM AUTHOR]

Prestrike phenomenon in circuit breakers (CBs) can cause electromagnetic transients in power systems. Therefore, the investigation of this phenomenon has considerable importance. The scope of this paper is to investigate the effects and importance of arcing contact shape on the prestrike in SF6 gas CBs. In order to simulate the prestrike with high accuracy, a multi-physics model is developed precisely. In this model, equations of motion of the SF6 gas, the electric charge conservation equation, turbulent equations, heat transfer equation in fluids, and the governing equations of an electric circuit in which the CB works are considered simultaneously. The numerical study is performed on a 72.5-kV single pressure puffer type SF6 CB. Three different types of arcing contacts are investigated in this paper. Numerical results show that the arcing contact shapes have an important effect on the prestrike in gas type CBs. [ABSTRACT FROM AUTHOR]

In recent years, all solid-state Marx generators have been found more and more extensive applications in industrial, environmental, and biological fields. All solid-state Marx generators have many requirements for their drive circuits, such as good synchrony for driving signals at different stages, fine isolation between control signals and the main circuits, adjustable pulsewidths and frequencies, and good driving abilities. This paper proposes a high-performance drive circuit for a 24-stage Marx generator based on IGBTs. A half-bridge circuit using IR2110 outputs a high-current turning-on drive signal (positive) and a turning-off drive signal (negative) with adjustable dead time. The control drivers are input to the common primary side of 24 nanocrystalline magnetic transformers, which isolate the control circuit and the main circuit. Through gate circuits at the second sides of the magnetic cores, the turning-on drive signal charges 24 gate–emitter capacitors to required voltages and consequently all IGBTs move into on state until the turning-off signal arrives. Similarly, the negative turning-off drive signal charges all gate–emitter capacitors to a negative voltage which ensures all IGBTs stay in the off state. Therefore, the pulsewidth is determined by the phase difference between the turning-on and turning-off drive signals. Equipped with this drive circuit, the 24-stage Marx generator is able to produce stable high voltage pulse with a peak value of −9.6 kV, PRF $0.05\sim 5$ kHz, and different pulsewidths. In this paper, the design details and experimental confirmation of the proposed drive circuit are illustrated. [ABSTRACT FROM AUTHOR]

In this paper, we designed an active coupling trigger circuit and an active surge protection gap (ASPG). The surge protection level of the passive SPG is improved, and the operating time of the passive SPG is shortened. The equivalent circuits for the coupling trigger circuit were developed. Then, we analyzed the component transient voltage of the active coupling trigger circuit with the combination wave injected. We obtained the numerical relationship between the coupling trigger current and the current flowing through the ASPG. In addition, the timing relationship between the component voltage and the current was acquired. To verify the analysis results, we established the combination wave generator and conducted an experiment. In the experiment, we observed that the trigger circuit operating time and the ASPG impulse breakdown voltage changed with the capacitor charging voltage of the combination wave generator. Furthermore, we discovered the change laws. The results also show that the operating time and impulse breakdown voltage of the ASPG are both smaller than the passive SPG. These results provide an important theoretical and experimental basis for the further study and structural optimization of the ASPG. [ABSTRACT FROM AUTHOR]

Large railguns require powerful power supply units. At the French-German Research Institute of Saint-Louis (ISL), most experimental railguns are driven by power supply units based on capacitors. Recent investigations at ISL explore the possibility to use coil-based systems to increase the energy density and reduce the footprint of the power supply. In this paper, an electrical circuit simulation is used to investigate the difference for railgun operation in between a capacitor and a coil-based power supply with respect to the current amplitude behavior, projectile velocity, and launch efficiency. For this, a scenario of a 25-MJ muzzle energy railgun is simulated with two different power supply options; one is based on capacitors, and the other is on coils. The circuit resistance determines a large part of the losses of the system and therefore defines the efficiency of the launch and the size of the power supply. Therefore, a range of different resistances were simulated as well. The interpretation of the results of the performed simulations leads to the conclusion that the capacitor-based system “naturally” produces a favorable current pulse trace with respect to launching a mechanical delicate payload. Further simulations show that the disadvantage of the inductor-based supply can be mitigated by increasing the power supply unit subdivision into smaller units. [ABSTRACT FROM AUTHOR]

For massive conductors with the characteristic sizes exceeding the penetration depth of variable or pulse magnetic field, it is possible to define the skin parameter, which affects transients in electrical circuits with massive conductors and does not depend on time and frequency. This paper describes the peculiarities of transients in circuits with massive conductors, defines and justifies the skin parameter, presents the methods of its calculation and measurement, as well as the results of calculation of transients in electrical circuits with massive conductors. [ABSTRACT FROM AUTHOR]

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]

Isolated phase bus (IPB) is generally used in power plants to connect the generator to the main transformers due to its shielding ability. And this paper presents the electromagnetic shielding effectiveness analysis of the IPB applied in International Thermonuclear Experimental Reactor poloidal field converters. The circulating currents induced in the enclosures and the magnetic field around the IPB are analyzed and studied. An equivalent electrical circuit is built to analyze the circulating current with a nonsinusoidal input by solving the corresponding numerical differential equations. And an experimental test is also performed on a full scale prototype to verify the model and results of the analysis. In addition, magnetic field distribution around the IPB is analyzed based on the Fourier decomposition and finite-element method. The analysis result indicates that the IPB is of good electromagnetic shielding ability. And the method of the analysis presented in this paper is proved to have great value in the analysis and design of IPB used in converter systems. [ABSTRACT FROM PUBLISHER]

Slow transfer of energy through capacitive hybrid (STRETCH) meat grinder circuit, which was proposed by the Institute for Advanced Technology, added a capacitor into the traditional meat grinder circuit. Even though its energy density is slightly less than the corresponding pure inductance system, it can reduce the voltage across the opening switch and maintain the high multiplication factor of the opening current. The performance of the STRETCH meat grinder circuit depends on multiple parameters. The inductance ratio ( n=L1 / L2) and the capacitance (C) are the two vital factors, which have a crucial influence on the system performance, such as the voltage over the opening switch ( V_{\rm Sopm}) , the current multiplication factor ( m$ ), and the ratio of the maximum capacitive energy over the total inductive energy ( $\eta )$ . Thorough studies have been carried out in this paper on the relationship between the above two factors and the three performance criteria. This paper also discusses and analyzes the chosen of the key parameters ( $n$ and $C$ ) for a single-stage STRETCH meat grinder with 2-mH total inductance, which is made up of two serial coils with 0.95 coupling factor. The opening current of the main switch is 1 kA, which constitutes a 1-kJ inductive pulsed-power supply. It fully takes the advantage of the STRETCH meat grinder topology, intensifies the study of the inductive pulsed-power supply with higher energies, and is easy to be utilized for practical application. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of a 40-kV, 20-kJ/s high-voltage capacitor charger based on a series/parallel resonant converter. The inclusion of the parallel resonant capacitor component in this circuit results in the production of a trapezoidal resonant current, which reduces conduction loss. This capacitor is practically realized as a part of the balancing network of the high-voltage rectifiers in the secondary side of the circuit. Particular attention in this paper is paid to the high-voltage transformer, which must be carefully designed to provide the required functionality without negative impact on the resonant circuit. A PSpice simulation has been used to prove that the proposed control method for the circuit is valid. This is supported with the experimental results, which verify that the operation of the circuit is as expected and that the converter is able to meet all the design criteria with an efficiency of up to 96%. [ABSTRACT FROM PUBLISHER]

The virtual cathode oscillator (vircator), which is one of the microwave sources, has been widely studied for about 40 years, since it has advantages, such as its simple structure and high-power radiation. To implement the behavior of the vircator, a simulation model of the axial vircator using circuit elements is studied in this paper. There are two steps in simulation of this paper: 1) obtaining the optimized case in the fixed input power that has a maximum efficiency and 2) at the case, conducting the circuit modeling. Passive elements and switches are used to model the power losses, emission threshold, etc. This circuit analysis is simulated by the Electro Magnetic Transient Program. Through the simulation model of the axial vircator using circuit elements, the high-power electromagnetic system can be handled as an integrated system, which contains a prime power part, a pulsed power part, a microwave source part, etc. This means that the circuit analysis can be carried out from the prime power to the vircator. [ABSTRACT FROM PUBLISHER]

In this paper, a compact circuit topology is presented for pulsed power generation with a semiconductor opening switch (SOS). Such circuits require the generation of a fast forward current through the diode, followed by a reverse current that activates the recovery process. In general, magnetic switches are used to switch the diode current from forward to reverse. Therefore, adjustment of the output voltage of an SOS pulser is difficult. This paper introduces a circuit that allows an adjustable output voltage of the pulser. A solution is realized with a premagnetizing circuit on the primary winding of a pulse transformer (PT), so that a third winding is not needed. The primary capacitor voltage can now be varied while maintaining proper saturation of the PT. [ABSTRACT FROM PUBLISHER]

This paper puts forward a novel high-voltage pulse generator, which can output a near square waveform across the load. The generator is composed of a conventional Marx generator, an $LC$ filter and a metal–oxide varistor (MOV) in parallel with the load. The Marx generator and the filter form a two-section type-A Guillemin pulse forming network (PFN). The PFN outputs a near square waveform and the MOV further stabilizes the voltage because of the MOV’s nonlinear resistivity. Circuit simulation verifies the working principle. Design parameters for the conventional PFN are derived. Considering the stray inductance of the filter, a more realistic PFN circuit is proposed and its parameters are derived. Preliminary experiments are conducted and verify the concept. Typical output waveforms have 20–30-ns rise time, 1000–1100-ns pulsewidth, and ~7-kV peak voltage. The pulse generator based on this concept is suitable to be used as a compact, long-pulse high power microwave modulator as it has a simple design, a well-defined flat top and it can output near constant voltage even if the load’s impedance varies. [ABSTRACT FROM AUTHOR]

This paper presents a new method to calculate stray capacitance of coil turns of magneto flux cumulative generator. The proposed method depends on the coil geometrical properties. The presented analysis in this paper is based on the calculation of capacitance between two adjacent turns and capacitance between the coil turns and the central cylindrical liner of the generator for a single-layer coil with N series turns having an integrated round cross section. Moreover, the effects of the insulating coating of winding, winding pitch, distance of coil turns to the central cylindrical liner on the stray capacitance, and the sensitivity analysis of effective parameters in the creation of stray capacitance between coil turns and also between coil turns and the central cylindrical liner are considered in this paper. Simulation results show that the proposed method is very useful for the designing geometrical structure of the magneto cumulative generator coil. [ABSTRACT FROM AUTHOR]

The objective of this paper is to determine arcing contact gap of a 126-kV horseshoe-type bipolar axial magnetic field vacuum interrupter. Drawn arc experiments were carried out in a demountable vacuum. Experimental current ranged from 12- to 40-kA rms. Based on the vacuum arc behavior, minimum arcing contact gap $D_{1}$ and maximum arcing contact gap $D_{2}$ were defined. When average opening speed within 20 mm ($v_{1}$) was 1.9, 2.3, and 2.6 m/s, $D_{1}$ was determined as 15.3, 16.8, and 14.3 mm, respectively. In addition, $D_{1}$ reflected a peak effect with $v_{1}$. When average opening speed within 40 mm ($v_{2}$) was 2.6, 2.7, and 2.8 m/s, $D_{2}$ was determined as 38.5, 36.7, and 36.1 mm, respectively. Uncontrollable arc mode appeared when current was higher than 32 kA with arc duration of 9 ms. The critical contact gap to avoid uncontrollable arc mode decreased as a liner function of arc current. Based on the experimental results, quantitative design method of three-interval opening velocity for the 126-kV horseshoe-type vacuum circuit breaker was proposed. For short-circuit current interruption test duty T100s, lower limit value of $v_{1}$ and upper limit value of $v_{2}$ were determined as 2.5 and 2.9 m/s with a prospective minimum arcing time of 7 ms. [ABSTRACT FROM AUTHOR]

This paper presents the design and construction of a sample of Marx pulsed generator based on boost converter (BC) pulse-forming networks (BCPFNs). BCPFN is used instead of the conventional Marx floors for constructing this pulsed generator. BCPFN is carried out by connecting inductors and capacitors in series and parallel modes, respectively, by using solid-state switches, and during this procedure the pulsed generator converts to BC temporarily and increases the voltage of capacitors uniformly to a considerable value. This technique causes an increase in the discharging voltage level to the load that is many times more than its dc voltage source by charging the capacitors to a greater level. In order to take advantage of the benefits of Marx generator and PFN, this paper suggests a new circuit with the minimum number of switches. It means, to compose BCPFN and Marx, we have tried to design the circuit with fewer switches and instead of it we have achieved our desired performance with changing the operating mode in the states of BC, PFN, BCPFN, and BCPFN Marx. The results are simulated with MATLAB software. At the end, the experimental results of the construction of the above-mentioned system at low-power levels are presented, and the topology’s accuracy is proved by comparing them to the results of simulation. [ABSTRACT FROM AUTHOR]

The Marx circuit structure based on fast high-power semiconductor devices is the classical way of generating picosecond pulses. However, most reported studies suggest that as the number of stages in the Marx circuit increases, the output pulse amplitude tends to saturate. This has of late made high-voltage picosecond-pulse generation a challenge. In this paper, as the number of stages increases, the internal resistance of the avalanche transistor tends to decrease with increasing current flowing through the avalanche transistor. A step-by-step wiring and debugging of the avalanche transistor-based Marx circuit demonstrates this experimentally. That is, for a certain range in the number of stages, saturation of the output pulse amplitude for the Marx circuit of avalanche transistors is not apparent. Introducing a parallel structure for the transistors not only increases the current level of the entire circuit but also further reduces the equivalent resistance of the avalanche transistors, thereby improving the output efficiency. Drawing on microstrip transmission theory, and combining the Marx circuit and avalanche transistor parallel structure, component parameters and circuit topology of the picosecond-pulse generator were redesigned, and a 30-level Marx circuit with a parallel structure of two avalanche transistors was developed. The picosecond-pulse generator outputs a pulse with adjustable voltage amplitude of 0.9–3.1 kV, a 350-ps full-width at half-maximum, a 150-ps rise time, and an adjustable high-stability repetition rate of up to 10 kHz. The number of pulses is precisely controlled. The generator is an all-solid-state compact device with high frequency suitable for research needs. [ABSTRACT FROM AUTHOR]

Optimal design and selection of arm inductances have been as a challenging subject in the field of modular multilevel converter (MMC). The average steady-state model is generally used as the analytical circuit model that neglects the switching frequency and harmonic values. Also, most of the researchers neglect the saturation effect of inductor core to simplify the analytical model. Contrary to the transformers, choosing the maximum flux density of inductance core is a sensitive issue, in order to design and minimize the inductors. Increasing the flux density reduces the inductor size, but getting close to the saturation region might alter the performance of the converter. This paper presents a systematic optimization approach to minimize high-power MMCs with saturable arm inductance considering technical, thermal, and manufacturing constraints. An accurate steady-state analytical model of MMC converter has been proposed and verified. A combination of converter circuit model and inductance electromagnetic model is employed to find the optimal arm inductances and capacitor values. The effect of nonideal inductance core on converter outputs has been investigated. A dimensioning model of inductor consisting of electromagnetic and thermal models is presented. To compute the optimal inductor size, a novel hybrid optimization loop is proposed including the analytical model of the converter and the inductor in which circuit, electromagnetic, and thermal properties are taken into consideration. In order to increase the accuracy of the dimensioning model, an internal verification loop is employed to verify and correct the analytical model using finite-element analysis. The proposed optimization loop aims to find the minimum inductor size considering technical and manufacturing constraints. Finally, the converter mass sensitivity of MMC converter versus some important constraints, such as temperature rise and capacitor ripple, has been investigated. [ABSTRACT FROM AUTHOR]

This paper describes the design and implementation of novel trigger circuit (23 kV, $1.7~\mu \text{s}$ , and 0.66 J/pulse) for xenon flash lamp driver. The design is based on a modified flyback circuit in the discontinuous conduction mode to take advantage of both generating the high voltage from the resonance with output capacitor and connecting the series with main pulse circuit using the flyback transformer which can carry the full current of several kiloampere at high-voltage side. This design eliminates the requirement for additional high-voltage protection devices in a xenon flash lamp driver. In addition, the unique high-voltage flyback transformer is designed with high turn ratio and low leakage inductance. The detailed design procedure for the resonant circuit at the output side of the flyback circuit with the permissible range of the parasitic component of the transformer is described on the basis of simplified analysis of resonant circuit. To verify the proposed design, computer simulation based on PSpice software and experiments for the proposed triggering circuit with a main pulse circuit was performed. For the experiment, the trigger circuit is developed with the specification of maximum 23-kV, 0.66-J/pulse output and tested with a xenon flash lamp (Heraeus P4101) driver consisting of a 1.5-kV, 36-kJ/s main pulse circuit and a 2.5-kW (500 V, 5 A) simmer circuit. The experiment is performed in both triggering without the simmer mode and combining the simmer mode. From the simulation and experimental results, it is verified that the triggering circuit can be used effectively, as it exhibits reliable ignition. [ABSTRACT FROM AUTHOR]

Experiments on high-current arcs carried out in an ultrahigh vacuum chamber are presented in this paper. For contact separation the lower electrode is moved by a mechanical-pneumatic device simulating the conditions of a vacuum circuit breaker. The arc behavior of the Cu–Cr test electrodes after the electrode separation without application of external magnetic field is observed by a high-speed video camera. Besides the usual electrical measurements, the emission in the gap along the electrode axis is investigated by spatially resolved optical emission spectroscopy. Differences are found in the intensity distribution of atomic and ionic lines along the gap. [ABSTRACT FROM PUBLISHER]

We have developed a circuit particle-in-cell (PIC) coupled model for simulating a pulsed power system, based on a circuit algorithm of a pulsed power supply and a PIC simulation for a magnetically insulated transmission line (MITL) system. The coupled algorithm comprises an external circuit algorithm based on BERTHA and a coupled algorithm for the PIC and circuit interface based on the Mur absorbing boundary condition. In this paper, a simple coaxial MITL with a single linear transformer driver (LTD) was simulated to validate the coupled model compared with PSPICE and BERTHA simulations. The numerical results show that the circuit–PIC coupled model achieved almost the same outputs on the load. The coupled model was then applied to an MITL system driven by ten LTD cavities. The simulation results and experimental results were in agreement, which confirms that the circuit–PIC coupled model could provide a reference for the structural design of experimental apparatuses. [ABSTRACT FROM PUBLISHER]

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]

In this paper, the numerical analysis on an air-core pulsed alternator is presented. Since compulsators are characterized by very fast electromechanical transients, their accurate analysis requires strong coupling between the equations governing the electrical and the mechanical behaviors. The device is investigated by using a dedicated numerical code capable to take into account eddy currents, compensating windings, as well as the excitation/control circuits. Furthermore, the code is capable of modeling centrifugal forces and vibrations acting on the shaft due to electric and mechanical unbalances or to misalignments of the shaft from its centered position. This makes the code a very powerful tool during the design phase. Examples of application of the code to machines with nonuniform compensating shield and with shorted compensating windings are shown. [ABSTRACT FROM PUBLISHER]

The major strengths of inductors in energy density and power density make an inductive pulsed power supply (IPPS) a promising option for pulsed power supplies in an electromagnetic launch system. Among the circuits for an IPPS, the capacitor-aided meat grinder circuits constitute an important branch. An analytical method for the working processes of these circuits is proposed in this paper. The core of this method is the decoupling of a high-order circuit into the superposition of a resistor–inductor first-order equivalent subcircuit and a resistor–inductor–capacitor second-order equivalent subcircuit. The validity and accuracy of this method have been verified through comparison with a numerical simulation. The results show that this method possesses both satisfactory accuracy and excellent computational speed. With the same circuit parameters and time step, the time cost of this method is three orders of magnitudes lower than the time cost of a numerical simulation. Moreover, this method contributes to more intuitive understanding and more essential insight into the working principles of the capacitor-aided meat grinder circuits. [ABSTRACT FROM PUBLISHER]

Active electromagnetic armor is a new kind of concept armor that integrates active defense and electromagnetic launch technology. During launching, the spatial movement of the intercepting projectile determines the intercepting probability for attacking the coming targets. For two perpendicular pancake coils, the intercepting projectile can be launched in different directions by changing the trigger times controlled by two switches. In this paper, a field-circuit coupled model of a two coil launcher is built first. When two coils are discharged simultaneously, the intercepting projectile is directed at the angular bisector of two coils. The eddy current in the intercepting projectile is mainly distributed near the coils, and the current density decreases dramatically along the normal direction of the surface. For different trigger times, the intercepting projectile moves in both types: linear and rotation. The moving characteristic on the intercepting projectile is analyzed. If the electromagnetic force is not exerted on the mass center along the movement of the intercepting projectile, the spatial movement may be changed. Based on the simulation results, a steerable launcher has been built. Three typical experimental results for the simultaneous discharge launching are shown under the same condition. The spatial movements for steerable launching at the simultaneous time and delay time of 1 ms are measured by the high speed camera. Compared with the experimental results, the simulation results are validated. It provides the reference for launching the projectile to intercept the coming targets. [ABSTRACT FROM PUBLISHER]

The RF front-end is a very vulnerable part of the coupling paths that are induced by a high power electromagnetic (HPEM) pulse. Existing studies found through experiment or simulation that low-noise amplifiers (LNAs) often break down or are damaged, which causes the malfunction of the RF front-end. To protect the RF front-end, the damage process of LNAs based on theory is required in detail. This paper summarizes the damage process, and a new library is developed describing the damage phenomenon of LNAs by using user-defined elements. The model can be combined with other circuit models, and can also offer variation of the internal parameters of LNAs by HPEM pulse. Existing physical protection methods have high costs and complexity, and it is difficult to provide perfect protection. Thus, the proposed model can contribute to protection studies utilizing a circuit model. [ABSTRACT FROM AUTHOR]

Because of lack of current zero, dc arc is hard to be extinguished, which has become the main reason causing faults in dc system. To find an effective method to detect dc arc faults is of great significance. In this paper, a method for detecting dc arc fault based on electromagnetic radiation signal is presented. A dc arc generating device is designed to simulate dc arc faults caused by loose connection in dc systems. A fourth-order Hilbert curve fractal antenna is adopted to detect the electromagnetic radiation signals of dc arc. The amplitude and spectrums of electromagnetic radiation signals measured under different circuit currents are analyzed. A photovoltaic (PV) system is constructed and the dc arc generated in that system is measured. The test results show that, under the present experimental condition, the electromagnetic radiation pulses have an obvious characteristic frequency, which are in a range of 39–41 MHz. The characteristic frequency of electromagnetic radiation of dc arc generated in PV system is around 39 MHz. Moreover, the characteristic frequency of dc arc is compared with that of switch operation. The dc arc has higher characteristic frequency and longer interval of each electromagnetic radiation pulse than those of the switch operation. The results indicate that the characteristic frequency of electromagnetic radiation signals can be used as the detection parameter of dc arc. [ABSTRACT FROM PUBLISHER]

This paper proposes an efficient modeling and an identification method for dielectric barrier discharge (DBD) systems, based on input–output (current–voltage) experimental measurements. The DBD is modeled using an equivalent electric circuit associated with a differential equation that describes the dynamics of its conductance. This equation assumes a homogeneous behavior of the gas. This paper introduces a series of polynomial terms of the current of the gas into the conductance equation. These terms, after identification, are a very useful tool to analyze the physical mechanisms that take place in the gas. The identification process also returns the numerical values of other DBD parameters, such as associated capacitances and the breakdown voltage. In addition, an asymmetric model for the gas, which considers the direction of the current, is proposed to consider the possible geometrical dissimilarity between the two electrodes of the DBD setup. Experimental measurements taken on two different DBD applications are used for validating the proposed approach. [ABSTRACT FROM PUBLISHER]

The impedance of an electrical coil wound over a flu- orescent tube is found experimentally both when the tube is ener- gized and de-energized. This paper reports results showing a sig- nificant change in the resonance characteristics of the coil due to the influence of the plasma core. The effects are described with the help of an equivalent circuit consisting of an inductance with a se- ries resistance and a parallel capacitance. This paper demonstrates that by energizing the core, the series resistance and shunt capac- itance in the equivalent circuit increase significantly. The experi- ment is performed both for alternating current and direct current excitations. From the observed results, fractional changes in the resonant characteristics are found and explained using a perturba- tional viewpoint. This enables us to indirectly estimate the plasma density profile and model the beam loading effects in high-energy radio frequency sources. The equivalent circuit model presented here can be employed to explain the macroscopic effect of low-tern- perature plasma on circuit elements Within close proximity. [ABSTRACT FROM AUTHOR]

Low-temperature plasma treatment is a promising technology for particulate matter (PM). In this paper, the arrayed dielectric barrier discharge (DBD) plasma reactor for PM2.5 removal is investigated at atmospheric pressure. In order to reveal the interaction between experimental findings and simulation results, the equivalent electrical circuit is used. The electrical model is implemented on the PSIM software. To calculate the capacitance of the arrayed DBD reactor, the capacitor expressions are developed. Considering the experimental elements, such as plasma-generated configuration and the power source, a topological equivalent circuit is given. Finally, the simulation results are compared with the experimental ones, and they agree well. In addition, the designed DBD reactor was used to investigate PM2.5 removal. PM2.5 removal after 4 min of plasma treatment found to be about 53.8%. [ABSTRACT FROM PUBLISHER]

Active attitude control systems require a non-negligible amount of space to be mounted on board satellites. For the nanosatellite case, it becomes even more difficult to accommodate an active attitude control system due to size and mass constraints, and choices of active attitude control system are therefore limited. In this paper, small size and lightweight are realized by direct drive and passive ignition of a thruster. The direct drive is a power supply system without a booster circuit. The passive ignition system is an ignition system using microdischarge generated by interaction with a plasma environment and the propellant surface. Availability of these two systems was verified. As a result, when the thruster was placed into a high-density plasma environment ( 10^12~\textm^-3) , it was confirmed that the direct drive and passive ignition can operate normally. Moreover, expected performance of this vacuum arc thruster was measured. The results show that the impulse bit was of micronewtons order, and the ion velocity was measured to be approximately 12 km/s. Moreover, it was found that the impulse bit changes with the applied voltage and the capacitance value of the discharge circuit. [ABSTRACT FROM PUBLISHER]

Many approaches exist for energy storage and delivery to the load, including high-power relativistic applications. One of the best solutions for the driver of high-power relativistic applications is the Marx generator. This paper describes the design, fabrication, and experimental validation of a Marx generator consisting of capacitors, spark-gap switches, and resistors. It is designed as an eight-stage Marx circuit to reach an output voltage level as low as −500 kV, and it is directly connected to the Blumlein pulse-forming line (PFL) to achieve more than 100 ns of the full-width at half-maximum. Experiments are performed with a solution load in a manner similar to having a coaxial structure in a high vacuum with a pressure of below 0.5\, \times \, 10^-5 torr, to prevent breakdown and measure the amplitude of the negative high-voltage pulse waveform. The solution load is designed to capture the short-pulse output of the PFL with a rise time of less than 25 ns and a voltage level of approximately −500 kV. The experimental results show that the output pulse can be used as a source to generate an intense relativistic electron beam at the gun for high-power relativistic applications. [ABSTRACT FROM PUBLISHER]

Based on the 1-D elastic–plastic reactive hydrodynamic code Simplified Stretch Sin, a magnetohydrodynamic (MHD) version SSS/MHD has been developed. The new code is of multifield coupling, making use of the Resistance-Inductance-Capacitance circuit equations related to loading currents and others. To calculate MHD and circuit variables consistently and simultaneously, on the basis of Faraday’s law, the relations between loading currents and magnetic flux in configuration cavities, variation in total magnetic flux and back electromotive force, and an iteration procedure are employed. The sample configurations in magnetically driven isentropic compression experiments (ICEs) here consist of parallel slabs and cavities, in which the step targets are a pair of slabs symmetrical to loading electrodes and of the same sample material but different in thickness. Self-consistent MHD and circuit calculations for ICE step targets of aluminum, tantalum, and plastic binder explosive is reported in this paper. The results agree with the measured ones well, including loading current profiles and velocity histories on samples’ free surface or optics window interface. Since the input data for this code are geometric sizes, material parameters, and original circuit parameters only, its results are independent of measured or empirical data, and could be helpful in design and prediction of ICE or other experiments. [ABSTRACT FROM PUBLISHER]

This paper describes the design and implementation of a three-phase resonant converter with low ripple and high control accuracy. Based on a three-phase LCC-type resonant converter—which has advantages of low ripple, high-efficiency, and high-power density compared with a single-phase converter—a high-voltage power supply with low ripple (<0.1%) was designed. In addition to the general merits of an LCC-type resonant converter operating at continuous conduction mode—including soft switching, low conduction loss, and current source characteristics—the proposed scheme uses only one phase under a light-load condition by having different leg designs of the gate drive circuit and snubber parameters. This allows the design to overcome the operational constraints of the general LCC-type resonant converter. The distinctive design of the three-phase converter structure provides high efficiency and low ripple not only during rated operation, but also under light-load conditions. In order to analyze the high performance of the proposed scheme from no load to rated load, a PSPICE simulation was carried out. Comparison results with a conventional LCC-type resonant converter based on a single-phase structure are analyzed from the viewpoints of output ripple, losses, and operable load range. Using the proposed converter, a 20-kV, 20-kW high-voltage dc power supply design and implementation was presented with a superior gate drive circuit. Finally, the superiority of the proposed converter was verified through a simulation and experimental results. It was experimentally confirmed that the developed power supply achieves high performance in terms of efficiency (98%), operable load range (0.5–20 kV), and low ripple (0.05%), with a high power density. [ABSTRACT FROM PUBLISHER]

A number of high-power applications require a transportable high-energy, high-current GW generator to drive a pulsed power system at the output. A first prototype, based on exploding wire technology and using an H-bridge circuit configuration, was developed at Loughborough University a few years ago and has been previously reported. The present stage of the work has necessitated the development of a more powerful and energetic source, and this is now based on inductive storage technology. A 400 kJ capacitor bank is connected by a high-Coulomb explosively driven closing switch with an air-cored 0.6 MV transformer, an exploding wire array, and a high-power diode based on a polarity-dependent spark-gap completing the arrangement. The GW generator, including the command and control module, is accommodated in two ISO containers. The various components of the generator are described in this paper, together with results obtained from full-scale tests. [ABSTRACT FROM PUBLISHER]

The primary test stand (PTS) is a high-current accelerator for Z-pinch experiment at China Academy of Engineering Physics. In this paper, a circuit model for its magnetically insulated transmission lines (MITLs) have been developed, in which all the PTSs transmission line (TL) sections from water TLs, to vacuum insulator stack, to both outer and inner MITLs, and eventually to a wire array load, have been treated as a total of 273 TL elements with different transit time and impedance, among which are comprised of 195 MITL elements. With the aid of the model, the performance of all these sections have been predicted and discussed, including conducting current, interface voltage, loss current, flow impedance, and grounded resistor of each MITL element, as well as the dynamic characteristics of the wire array load. The reliability and accuracy for all these predicted results will await the examination of future experiments. [ABSTRACT FROM PUBLISHER]

This paper discusses diffusion of a pulsed magnetic field into a resistive element fabricated from a low-carbon steel. The developed numerical model shows that the process of the magnetic field diffusion into the steel at the leading edge of the pulse can be conventionally described by three stages: initial stage extending up to saturation of the steel surface layers, stage of saturation when the discharge current diffuses into the bulk of the steel, and stage of conduction when the discharge current is distributed practically uniformly in the steel. Approximate analytical relations describing the voltage drop across the resistive element are derived for each of the three stages. These relations are used for estimation of the effect of the ferromagnetic properties of the steel on transients in electrical circuits with the resistive element. Experiments prove the validity of the obtained analytical results. [ABSTRACT FROM PUBLISHER]

This paper presents a homogeneous study of xenon dielectric barrier discharge (DBD). The model, including plasma chemistry, electrical circuit, and Boltzmann equation modules, investigates the electrical and physical characteristics of high-pressure DBDs. The model is applied in the case of a sinusoidal voltage at period frequency of 50 kHz and gas pressure of 400 torr. First, we have analyzed the temporal evolutions of the plasma voltage, the current density and the species concentrations. Then, the physical model validity is checked by comparing the model results with a theoretical work. The effect of the kinetic scheme on the electrical parameters, the species concentration, and the total lamp efficiency are also investigated and discussed. [ABSTRACT FROM AUTHOR]

Current transformers (CTs) (ACCT/DCCT) are used as noninterceptive means of beam current measurement in the IFMIF/EVEDA accelerator. However, current measurement using CTs for long pulses with 100 ms or longer such problems as droops are apparent. This is due to the fact that this measurement is based on the current induction through transformers and is considered inevitable. We propose a method for retrieving the beam currents from the ACCT output waveforms using an experimentally obtained transfer function. This method has several advantages. The transfer function is easy to obtain from simple experiments with a function generator and an oscilloscope other than the ACCT and an amplifier, and the effects of stray capacitance, inductance, and magnetic materials nearby are inherently included in the transfer function. Square waveforms with different pulselengths are used to numerically obtain the forward and backward transfer functions, and this method for current waveform retrieval was validated. It was confirmed in experiments that square waveforms with lengths from 100 ms to 1.3 s could be retrieved without droops from the ACCT output. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate how strong an axial magnetic field (AMF) is needed in test duty T100a for a 126-kV single-break vacuum circuit breaker (VCB) when interrupting a rated short circuit current of 40-kA rms in light of arcing contact gap, arc duration and phase shift effect. The AMF is generated by a pair of 2/3 coil-type AMF contacts. First, the accuracy of a 3-D finite element simulation of AMF is validated by an AMF measurement at a contact gap 30 mm and the error is <10\%. After that test duty T100a of the 126-kV single-break VCB are carried out 18 times with arc duration from 3.3 to 19 ms at 40-kA rms. With a given opening displacement curve, the contact gap as arc extinguishes within a range from 12 to 50 mm corresponding to the arc duration from 3.3 to 19 ms. Then the AMF distribution of the 126-kV single-break VCB at each contact gap at which arc extinguished is simulated to analyze the current interrupting results. The results show that there are successful interruptions at the short-circuit current 40-kA rms in test duties T100a, with the shortest arcing contact gap window from 18 to 23 mm and the longest arcing contact gap of 44 mm. The shortest arcing contact gap window corresponds to the maximum AMF at the intermediate plane of the contact gap per kilo-ampere of the breaking peak current from 9.3 to 8.5 mT/kA. In addition, the longest arcing contact gap corresponds to the value of 6.1 mT/kA. The phase shift time at the center of intermediate plane of the contact gap ranged from 1.36 to 0.75 ms corresponding to an increase of arcing contact gap from 12 to 50 mm in the tests. [ABSTRACT FROM AUTHOR]

The stored-to-kinetic energy conversion efficiency of railgun system is investigated by simulation and experiment methods. There are many factors, which might affect the conversion efficiency of the railgun system. These factors include the parameter values of pulsed power supply (PPS), the velocity of armature, the inductance gradient of rail, and so on. To analyze the stored-to-kinetic energy conversion efficiency, a novel electric circuit simulation model for the railgun system is built. The simulation results show that the less resistance, the more inductance of PPS, the more inductance gradient of launcher, and the higher muzzle velocity of armature can improve the energy conversion efficiency of the railgun system. Some experimental results with the 6-MJ railgun system at Beijing Institute of Special Electromechanical Technology are also presented in this paper, which can illustrate the correctness of the analysis and the simulation results. [ABSTRACT FROM PUBLISHER]

The supercapacitor, because of its advantages of high specific power, quick charging or discharging with high current rates, and long cycle life, is an interesting choice for energy storage for applications where high power is needed for only a few seconds, such as pulse-power supply systems. Based on the use of supercapacitors all around the world, more and more attention is focused on the effects of temperature on their performance metrics such as capacitance, internal resistance, and efficiency. To predict the terminal voltage of supercapacitors at different temperatures, a three-branch RC equivalent circuit model is improved in this paper, and it can predict the terminal voltage up to 5 to 10 min after completion of charging or discharging. Initially, a typical three-branch RC equivalent circuit model without temperature parameter is used to simulate the pulse charging and discharging behavior of a specific commercial supercapacitor. Next, with the pulse charging and discharging experiment results under -40^\circC, -20^\circC, 0^\circC, and 20^\circC, all parameters in the circuit model are reset to a function of temperature, and the temperature dependence of parameters is discussed in detail and determined numerically. Finally, for the purpose of validating the correctness and the accuracy of the improved model, compared study of simulation results and experiment curves is done. Comparison results show that the fitting accuracy of the improved equivalent circuit model is satisfied in pulse charging and discharging at different temperature. [ABSTRACT FROM PUBLISHER]

In this paper, the circuit model capable of dealing with magnetizing characteristics of the magnetic cores and switch prefire is established for linear transformer driver (LTD) cavities in PSPICE. Through simulation, the effects of switch prefire on other components in LTD and its output current pulse have been analyzed associated with the variation of energy loss in magnetic cores. Simulation results indicate that a switch prefire in one cavity would produce oscillations added to the charge voltage of the other switches in this cavity and cavities adjacent immediately. The magnitudes of such oscillations have an intimate relation with the magnetic core loss equivalent resistance. The loss equivalent resistances in the range from 4 to 6 \Omega have produced moderate voltage oscillations. Experiments on the 300-kA LTD cavity developed by the Northwest Institute of Nuclear Technology proved that such oscillations added to the charge voltage of other switches are likely to increase the breakdown probability of them. [ABSTRACT FROM PUBLISHER]

Helical launchers have become attractive because of their high inductance gradient that allows obtaining a large thrust force for a given feeding current. Furthermore, helical launchers are characterized by a large maximum theoretical efficiency also in constant current mode. The possible presence of destructive arcs and the dissipation of the commutation energy in the brush material are serious problems that affect these launchers. A numerical model based on an equivalent circuit approach is adopted in this paper to investigate the overall performance of the helical launchers and to examine brush commutation. [ABSTRACT FROM PUBLISHER]

The performance of a single inductive coil driver with six different turns of drive coils is analyzed and emulated with the emulation program in this paper. Under the condition that the integral projectile mass is 1.125 kg and the armature length is 300.0 mm, the maximum velocities of the projectile are 130.1, 134.1, and 132.8 m/s when the drive coil axial lengths are 50.0, 100.0, and 150.0 mm, respectively, and the drive coil radial thickness is 20.0 mm. By changing the drive coil radial thickness to 30.0 mm, the maximum velocities of the projectile are 112.5, 110.2, and 116.3 m/s when the drive coil axial lengths are 50.0, 100.0, and 150.0 mm, respectively. The result shows that only when the structural parameters of the drive coil and the armature are matched suitably that the maximum velocity of the projectile can be reached. This conclusion provides a reference for the engineering practice of the inductive coil driver. [ABSTRACT FROM AUTHOR]

To analyze the stored-to-kinetic energy conversion efficiency, a transient electric-circuit model for a railgun system is built using the electrical circuit analysis software SIMPLORER in this paper, and the electric parameters of the model are defined with measurement values of the actual system. Many results of simulations and experiments are also presented, and the results show that the equivalent series resistance of the coaxial cables and the rail resistance are major factors on the energy conversion efficiency. In the end, some methods are proposed to improve energy conversion efficiency of the pulsed-power supply system. [ABSTRACT FROM AUTHOR]

This paper investigates the underlying influence of permanent magnet (PM) magnetization length on the performance of a tubular transverse flux PM linear machine working as the propeller of an electromagnetic launcher, including its main flux linkage, cogging force, and thrust force. The theoretical analysis is brought forward and verified with 3-D numerical computations. It is shown that the cogging force increases with the increase of the PM magnetization length, whereas the main flux linkage and thrust force do not follow this rule, which is quite different from that in conventional PM machines. [ABSTRACT FROM AUTHOR]

Very high frequency (VHF) capacitively coupled plasma (CCP) sources offer several benefits, including low plasma potential, high electron density, and controllable dissociation. However, standing electromagnetic waves can make the spatial structure of VHF plasmas a sensitive function of operating conditions and reactor geometry. This paper discusses how the profile of VHF CCPs can be controlled using an external circuit that modifies the electrical boundary conditions. A 2-D plasma model with external circuit has been used for this study, where networks of passive circuit elements can be connected to different electrodes in the reactor. Plasma simulations have been performed for several combinations of capacitors and inductors. It is found that the external circuit can be used to change the radio-frequency current return path, thereby modifying the plasma profile. In general, the plasma is pulled toward the electrode with an inductive impedance and pushed away from the electrode with a capacitive impedance. These changes in plasma profile are related to the relative voltage and their phase on different electrodes. [ABSTRACT FROM PUBLISHER]

In an effort to achieve higher power RF source performance, designers are utilizing distributed beam devices, such as sheet beams and multiple beams. A limitation is the amount of current that can be emitted by the cathode while still achieving long cathode lifetimes. The desire is to develop distributed beam devices that utilize fundamental mode cavities in the RF circuit. For multiple-beam devices, where the individual beams propagate at the same radius as the cathode, a limitation is reached, where the size of the cathode becomes limited by the space available. A solution is to place the cathodes at a larger radius and compress the beams toward the radius required for fundamental mode cavities. This paper describes the design of a multiple-beam gun where the ensemble of beams is compressed toward the device axis while still achieving parallel propagation through the RF circuit. [ABSTRACT FROM AUTHOR]

In power modulators for pulses in the microsecond range, transformers are often used for generating high output voltages. With standard topologies, the transformer is usually only excited in a unipolar direction, i.e., the flux density B swings between zero and a value close to the saturation flux density. By applying a reset circuit, the flux density B in the transformer is set to a value close to the negative saturation flux density before the pulse, so that the flux density could swing between the negative and positive saturation values during the pulse. This allows one to halve the core area and reduce the core volume/weight as well as the losses. In this paper, the operating modes of three different reset circuit topologies (the standard and a new advanced passive as well as an active one) and the corresponding waveforms are explained. Furthermore, the three topologies are compared with respect to the losses/complexity based on a design for a solid-state modulator with 20-MW output power and 200-ky output voltage. [ABSTRACT FROM AUTHOR]