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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]

ASELSAN Inc. has been conducting experimental research on electromagnetic launch technologies since 2014. The first prototype, EMFY-1, has 25 $\text {mm} \times 25$ mm square bore and 3-m-length rails. In addition, two capacitor-based pulsed-power supplies (PPSs) with 1- and 4-MJ stored energy are built to supply launcher. During the design process of EMFY-1, a 3-D finite element (FE) model has been developed to simulate the electromagnetic and mechanical aspects of the railgun. This paper presents the simulation and experimental results of EMFY-1 with C-type aluminum armature. FE model, developed using COMSOL Multiphysics, includes both launcher and the PPS system. In addition to the velocity and position of the armature with respect to time, it is possible to observe the magnetic field, current density distributions and breech voltage using the FE model. In the experiments, pulse currents of the PPS modules, breech, and muzzle voltages are measured. The velocity of the projectile is measured using the B-dot probes. In this paper, two experiments of EMFY-1 will be presented. In the first experiment, the launch package with 42-g total mass is accelerated to 2778 m/s, and in the second experiment, the launch package with 130-g total mass is accelerated to 1560 m/s. The simulation results of the proposed FE model are compared with the experiments. It is observed that there is a good agreement between experimental and simulation results. [ABSTRACT FROM AUTHOR]

Compulsators are popular choices for various high-power electromagnetic launch applications, especially for the electromagnetic railgun. A two-axis-compensated compulsator with lower internal impedance and higher power density was proposed in the authors’ previous paper. The field windings and compensating windings are allocated electrical orthogonally, providing the opportunity to design the direct-axis and quadrature-axis compensations independently. Due to the excitation function of the field windings, as well as field windings and compensating windings at the same rotor periphery, the ratio between $d$ -axis and $q$ -axis compensation is determined not only by the waveform of the air-gap flux density but also by the occupied space of windings, electromagnetic force during discharge and temperature rise and cooling condition. All these aspects mentioned above were analyzed in this paper. Furthermore, the output performance for single pulse discharge of a 2-m railgun with 100-g armature and multiple pulses discharge of a 5-m railgun with 300-g armature was simulated and compared. The results indicated that the two-axis compensation could obtain benefits by introducing more sinusoidal discharge currents for single pulse mission comparing to traditional compensation structure, whereas no obvious advantages for a flat-topped current waveform for multiple pulses mission. [ABSTRACT FROM AUTHOR]

A new modular pulsed-power source with fast rise time and step-wise arbitrary output waveform generation is currently under development to drive the Gepulste Elektronenstrahlanlage device investigated at the Institute for Pulsed Power and Microwave Technology (IHM). Acknowledging the complex design procedures necessary to set up a modular pulsed-power source for voltages of up to 120 kV, this paper focuses on the circuit design for a single stage and its validation prior to the generator assembly. Using a semiconductor-based Marx generator topology, the stages are designed to have an output voltage of 1 kV with a pulse current of up to 600 A. When connected to an ohmic load, the measured current rise times are in the order of 46 ns resulting in the current rise rates of up to 10 kA/ $\mu \text{s}$ using the commercial devices. The step-wise arbitrary output waveform is created by generating the switching commands on the stage using a microprocessor and a fast optical synchronization unit. Effective stage shielding is verified by operating the stage in a 100-kV, 2.5-kA electromagnetic interference test bed. This paper presents the design considerations and the corresponding measurements. [ABSTRACT FROM AUTHOR]

Isentropic compression experiments (ICEs) are an important method to study the dynamic characteristics of materials at pressures, temperatures, and stress or strain rate not attainable in conventional shock experiments. Yet it makes high demands toward the precise current pulse tailoring capability of the source. The China Academy of Engineering Physics is now developing a 20-brick parallel discharge driver and a 256-brick parallel discharge driver (CQ-7) to improve the performance and flexibility of compact magnetic compression devices. The load current of ICEs is tailored by optimizing the switch trigger sequence and the brick charging voltage. This paper establishes the equivalent circuit model of the 20-brick parallel discharge driver, taking the distributed inductance, resistance, and capacitance of transmission plates into account based on the partial-element equivalent circuit method. Besides, the equivalent circuit model of discharge brick based on the switch arc resistance model is also established to study the influence of key structural parameters on the output current. Furthermore, by comparing the simulation and experimental results of simultaneous discharge of 20-brick driver, the accuracy of simulation model is confirmed. This paper is of great significance to the design and optimization of multibrick parallel discharge drivers. [ABSTRACT FROM AUTHOR]

The linear induction launcher consists of two parts: the barrel section and the projectile section. The barrel contains of a long coaxial sectionalized group of coils that are energized by a capacitor bank or generator sets. This paper deals with the design, implementation, and experimental test of a coreless axial-flux permanent magnet (AFPM) pulsed alternator with a flywheel system as an energy source for linear induction coil launchers. The proposed coreless AFPM generator has a low internal inductance and resistance of stator windings without compensation windings when compared with the conventional iron core machines. This paper describes the coreless AFPM generator configuration and shows the simulation findings. [ABSTRACT FROM AUTHOR]

Reluctance coilgun (RCG) is a special coilgun which uses solid ferromagnetic material instead of induction coil as projectile. RCG has shown great advantages and potential in the application of antiterrorism weaponry due to its simplicity, reliability, and excellent controllability. As a compact lightweight pulsed-power supply (PPS), the compensated pulsed alternator (Compulsator) will play a key role in promoting this kind of electromagnetic weapon into practical applications. Focused on a specific RCG which has conductive rails and brushes, this paper deduced the electromagnetic force analytical formula by using the virtual displacement principle and researched the feasibility of the electromagnetic launch design scheme which uses compulsator as the PPS of the RCG system by co-simulation method. Finally, this paper finished tests of the system by taking advantages of a small demonstrative RCG and a scale-model prototype of the compulsator. The results indicate that the design scheme is completely feasible. [ABSTRACT FROM PUBLISHER]

Because it possesses higher current turn-off capability, the inverse current commutation with semiconductor devices (ICCOS) is a better option for the opening switch of an inductive pulsed power supply than the integrated gate commutated thyristor. This paper investigates the counter-current capacitor, which is the key component that determines the turn-off result and the volume of the counter-current branch. The major contributions of this paper include the following: 1) deriving an analytical expression for the minimum precharged capacitor voltage that can reliably turn off the main switch; 2) verifying this expression through a series of experiments within a current range of 0 to 4000 A and an energy range of 0 to 50 kJ; 3) giving an approximate expression for the optimal capacitance that minimizes the precharged energy; and 4) investigating the variation trends of the optimal capacitance and the corresponding optimal precharged energy with varying inductor current. [ABSTRACT FROM PUBLISHER]

The pulsed high-power supplies in this paper employs a homopolar inductor alternator (HIA) as the motor/generator integrated energy storage pulsed alternator. Lumped parameter design equations are developed, which is used to establish the mathematical model of the HIA, and the analytic calculation method of inductance matrix is derived. Prototype flywheel energy storage was built, and the basic structure of HIA is analyzed by using finite-element method (FEM). This paper proposes a simplified equivalent 2-D salient-pole synchronous generator model to simplify the 3-D FEM of HIA and investigates the motor control method of HIA based on the simplified 2-D equivalent model. The experiments were conducted for speed up to 8000 rpm and the six-step inverter drive strategy presented in this paper achieves the motor/generator integrated control on inductor energy storage pulsed alternator (IESPA). Most experimental results were in line with designed value. [ABSTRACT FROM PUBLISHER]

Based on the urgent needs for modularization and miniaturization of the inductive pulsed power supply system, this paper proposes the conceptual design and comparison of 100-kJ inductive storage power modules including four circuit topologies, three of which are proposed in our previous researches. The four circuit topologies are the STRETCH meat grinder, the XRAM with STRETCH meat grinder unit, the XRAM with strongly coupled inductors, and the XRAM with magnetic flux compression effect. The maximum load current of each constructed module is set to be 50 kA and its pulsewidth is at least 5 ms, which are the same as the main electrical properties of an existing 100-kJ capacitive module. A comparative study on energy density among the constructed inductive modules and the existing capacitive module is carried out in depth. Results show that the inductive modules, considering the volume of semiconductor switches and their control circuits, have higher energy density than that of the capacitive module. Among four constructed inductive modules, the XRAM with strongly coupled inductors module has the highest inductive energy density, and the XRAM with magnetic flux compression effect module has relatively better comprehensive performance. This paper offers the theoretical analysis foundation for investigating the inductive pulse power supply with higher energy. [ABSTRACT FROM PUBLISHER]

Superconducting pulsed-power supply (SPPS) provides an efficient method for both high-density inductive energy storage and high current pulse generation. An SPPS consisting of eight high-temperature superconducting pulsed-power transformer (HTSPPT) modules with XRAM methodology was designed and simulated in preliminary studies. It recycled the leakage flux energy and reduced the voltage across the opening switch with a capacitor in primary. However, the SPPS with XRAM methodology has two problems. The first one is that it can provide high pulse amplitude, but cannot provide enough width. The other one is that the ratio of the maximum capacitive energy over the total inductive energy is relatively large, which cuts down the overall system energy density. This paper proposes a modified topology of SPPS with capacitor reuse methodology. Multiple HTSPPT modules are divided into several groups. Each group shares the same capacitor. The procedure of the modified SPPS is presented in detail. A 270-kJ SPPS with capacitor reuse methodology is designed and simulated to illustrate the modified topology. With the load parameters of a small railgun, the peak value of the load current is 207.15 kA and the pulse half-height width is 5.56 ms, the ratio of the maximum capacitive energy over the total inductive energy is 11%. The characteristics of the modified topology are also described in detail in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents a novel brushless doubly-fed pulsed alternator (BDPA) in the direct-drive power supply system for high-energy pulsed lasers. There are two sets of stator winding which are embedded in the stator slots of BDPA. One is called power winding and another is called control winding. The rotor winding is short circuit. Because there is no brush, compared with the compensated pulsed alternator, BDPA has higher reliability and can run at higher speeds to get higher energy-storing density. Besides, when the system works on the state of continuous multiple pulses, with a decrease of speed, the BDPA can maintain the frequency and voltage of the power winding constant basically. In this paper, the design procedure of BDPA is proposed according to the requirement of the high-energy pulsed lasers. Utilizing the finite-element model of the alternator, we can analyze the electromagnetic properties and calculate inductance parameters of the BDPA to verify the design scheme. Meanwhile, the simulation model of the direct-drive power supply system is established in MATLAB/Simulink to analyze the output performance of the flashlamp load. The simulation results confirmed the feasibility of design scheme of BDPA for the system. [ABSTRACT FROM PUBLISHER]

Marx generator using all-solid-state devices has been studied for many years. Higher parameters are always the demand for new applications. Traditional all-solid-state Marx generator can output high voltage due to its series topology, but the current is always limited by the switch. In this paper, a stage-stage paralleled topology of Marx generator for high current has been proposed. Topology structure and driving mode comparison for current balance have been analyzed. The paralleled driving mode for the current balance and the shaping waveform has been proposed. For experiment, a four-stage-four-paralleled Marx generator with metal–oxide–semiconductor field-effect transistors (MOSFETs) has been constructed with output pulses 2.2 kV, 730 A (depending on the load), rise time of 31 ns, fall time of 56 ns, and adjustable pulsewidth from 400 to 800 ns. [ABSTRACT FROM AUTHOR]

In order to analyze the performance of a fast linear transformer driver (FLTD) in different states, we develop a circuit model of nonlinear magnetic core. The circuit model contains controllable initial magnetic flux density and time-dependent loss resistance of the magnetic core. Afterward, the core model is added to the integral circuit to simulate the performance of the single stage FLTD; both the simulation and experimental results are given in this paper and the simulation results fit the experimental results very well under different situations. Moreover, this circuit model can be used to analyze the conditions when some faults occurred in the magnetic core. [ABSTRACT FROM AUTHOR]

The air-core pulsed alternator has the integrated advantages of high energy density and high power density. It has important applications in new concept kinetic energy weapons such as electromagnetic launching and has become the research focus of many countries at present. However, the air-core machine with a current up to mega-ampere level still lacks testing, it is impractical and unscientific for the machine to drive the railgun directly without any experimental basis, and its huge risk and cost for testing must be taken into consideration. This paper presents an equivalent load instead of the electromagnetic railgun, which is used to accomplish the relevant testing research and theoretical verification. In this text, the design scheme for the equivalent load is proposed according to performance requirements, and it is composed of an inner cylinder and an outer cylinder with a coaxial configuration. Then, the design is carried out by taking parameters of resistance, inductance, maximum temperature rising, stress, and length into consideration. Finally, it is necessary to develop simulations to verify electrical and mechanical performances of the load. The results provide a technical guidance and support for the actual railgun testing. It is helpful to promote the development of the air-core pulsed alternator, directly driving the electromagnetic railgun. [ABSTRACT FROM AUTHOR]

Synchronous induction coilgun (SICG) has attracted more and more attention due to its advantages of simple manufacturing and no physical contact between armature and barrel. The armature, as an important component of SICG, will directly affect the launch speed and energy conversion efficiency. According to the distribution characteristics of eddy current and electromagnetic force, a new structural armature is proposed in this paper. The proposed inner conical armature is characterized by the maximum thickness at the tail end and the minimum thickness at the front end, with a gradual decrease in the thickness along the axial direction. The simulation results reveal that the proposed armature not only increases the mutual inductance between the armature and the drive coil but also enhances the electromagnetic force and weakens the armature capture effect. The experimental results verify that, compared with a traditional armature weighing 56.5 g, the new structure armature weighing 58.0 g enables higher muzzle velocities using the same set of pulsed power supply and drive coil, providing higher efficiency. [ABSTRACT FROM AUTHOR]

The driving coil, as a key element of synchronous induction coilgun, endures not only the radial expansionary force because of the magnetic flux compression but also the axial force due to the compressive force and counterforce of the armature. Dielectric breakdown and mechanical structure damage occurs frequently. Meanwhile, the driving coil should have high energy conversion efficiency as a pusher to accelerate the armature. Therefore, it is important to choose the appropriate structure and parameters in order to achieve a high launching performance. In this paper, the factors that influence the system efficiency are analyzed first. Different structure designs of the driving coil with the same inductance are evaluated. The effect of different calibers on the system efficiency is analyzed. The simulation result shows that the structure of the driving coil should be chosen according to the practical launching requirement while the magnetic coupling should be increased. Second, the electromagnetic force applied on the coil is calculated and the stress is analyzed. The thickness and displacement of the containment are calculated on the condition of unyielding. In order to validate the accuracy of the theoretical analysis, an electromagnetic-mechanical coupling finite element model is built. Comparing two calculation results, the error is small. Therefore, the method can be used to guide the design of the driving coil. Finally, a driving coil is fabricated according to the calculation results and experimented through static and dynamic tests. The experimental results show that the driving coil performs well and have high conversion efficiency. It provides a theoretical and experimental basis for the future design of multistage induction coilgun. [ABSTRACT FROM AUTHOR]

To deal with the uneven force on the inner and outer layers of the series coils as well as a large force on and temperature rise in its single layer under the influence of high pulse current during the electromagnetic launch (EML), this paper proposes a method of winding the wires of different diameters and turns by layers to make the multilayer coil parallel and the force on its layer uniform. But the prerequisite for the method is to ensure that the total current in the series coil and new-type coils keeps basically unchanged. The idea of designing the uniform distribution of coil current will provide a new approach to designing coils in the future. [ABSTRACT FROM AUTHOR]

In 2016, Hanwha Defense Systems Corporation commenced an electromagnetic launcher program to develop the next-generation “cold-launching” missile launcher system. This system is based on multistage induction coilguns with advantages such as controllability of energy transfer, reusability, and noncontact between the armature and the stators. The system requirement is to launch missiles to a height of 20 m with weight ranging from hundreds of kilograms to several tons. This paper presents the design, fabrication, and experiment results of a laboratory-scale electromagnetic launcher to demonstrate the feasibility of an electromagnetic launcher for heavy missiles. The effectiveness and performance of an electromagnetic launcher developed to launch heavy missiles have been demonstrated by accelerating a 21.68-kg projectile to 20 m/s. [ABSTRACT FROM AUTHOR]

In switching power supplies, the transformer leakage inductance (TLI) is of considerable practical significance. Ordered winding is the certain assumption in previously reported works for the calculation of the TLI value. However, disordered windings are usually unavoidable in practice and their effect on the value of the TLI is considerable. The problem becomes more complex when the number of winding turns increases. In this paper, the effect of winding disorder on the TLI value is investigated. In disordered wrapping, the winding turns arrangement (WTA) of each produced transformer is different from the others. Thus, each produced transformer has an exclusive TLI value in a disordered wrapping. Moreover, the number of possible WTAs is high, especially in transformers with a large number of winding turns. The proposed method utilizes an analytical tool for estimating the distribution of the TLI values for all of the possible WTAs. This estimation is carried out based on the limited number of the WTAs. The required number of WTAs is calculated and the validity of the proposed method is checked with Kolmogorov–Smirnov theorem. The TLI value is calculated by means of the stored magnetic energy in different parts of the transformer using the magnetomotive force variation method. Finite element simulation and experimental results are presented to show the effects of disorder on the TLI value and the validity of the proposed analytical method. [ABSTRACT FROM AUTHOR]

Induction synchrotron (IS) has become the focus of improving the intensity of high energy ion beams in recent years. But because of the pulse voltage of the induction accelerating cell cannot adjust quickly, causing the mismatch of the magnetic deflection field and accelerate electric field, there is a serious beam loss problem in IS. The simulation of beams longitude dynamics proves that increasing the number of accelerating cells can effectively reduce the loss. In this paper, a novel compact induction accelerator module is introduced. Compared with the existing induction accelerator module of KEK, the new design can increase the number of accelerating cells to more than five times in the same installation space and improves the voltage top drop of the acceleration pulse significantly. [ABSTRACT FROM AUTHOR]

The superconducting inductive pulsed-power supply (IPPS) is considered to have broad application prospects in the field of electromagnetic launch because of its low electrical loss. In order to obtain a higher efficiency in continuous electromagnetic launch, a repetitive IPPS circuit topology based on a high-temperature superconducting pulse power transformer (HTSPPT) has been proposed in our previous studies. It can recover most of the remaining energy for generating continuous current pulses by using a bridge-type capacitive switching circuit. As a follow-up work, this paper presents a multimodule repetitive superconducting IPPS model for a railgun system. This multimodule model consists of 24 HTSPPT modules connected to an XRAM-like circuit topology. In order to verify the feasibility of the repetitive superconducting IPPS and study its driving characteristics, the dynamic launching process of a simple 4-m-long railgun system was simulated. The influence of the capacitance in the bridge-type capacitive switching circuit on the main performance of the system, such as the maximum output current, the maximum primary voltage, the launch efficiency, the maximum capacitive energy ratio, and the remaining energy recovery ratio, was analyzed. The simulation results show that the repetitive superconducting IPPS is suitable for driving the simple railgun. In addition, it also concluded that the system performances conflict with each other and the optimal capacitance value for each HTSPPT module should be determined by the tradeoff of system performances. [ABSTRACT FROM AUTHOR]

This paper is aimed at finding the effect of varying inductive energy storage systems’ (IESSs) inductance on resistance of an electrically exploded conductor-based opening switch and profile of current transferred into load, which has not yet been fully understood. Based on experimental results obtained, it is observed that when the inductance of IESS is varied, the magnitude of load current changes so as to conform to the magnetic flux conservation law but its rise time remains unchanged. Resistance of the opening switch and energy deposited in it has been estimated using recorded voltage and current waveforms. It has been found that with increasing inductance of IESS, the resistance of switch increases, whereas energy deposited in it decreases. Using these estimated values of energy, a possible explanation of observed behavior in resistance is presented. Effect of a mismatch between the inductance of IESS and load is seen to only affect the energy transfer efficiency or magnitude of load current but not its rise time emphasizing the novel finding that for a given load, the rise time of load current is independent of the inductance of IESS. [ABSTRACT FROM AUTHOR]

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]

High-stability flat-top pulsed magnetic field, which combines the advantages of pulsed high magnetic field and steady high magnetic field, is widely used in in the fields of physics, biology, and chemistry. The pulsed alternator-rectifier power supply, with controllable output voltage, is suitable to discharge a multicoil magnet to generate a synthetic flat-top magnetic field with high parameters. However, the coupling characteristics of coil current and the time-varying nonlinear characteristics of magnetic field system bring challenges to generate a high-stability flat-top pulsed magnetic field. This paper first adds a decoupling transformer in discharge circuit of the 50-T flat-top pulsed magnetic field system existed at the Wuhan Nation High Magnetic Field Center, Wuhan, China, and hence, the coupling effect of 50-T dual-coil magnet can be eliminated. Then, a control method of high-stability flat-top pulsed magnetic field based on the model predictive control is proposed. A prediction model of rectifier trigger angle is obtained by establishing the mathematical model of the system. A simulation model is built by MATLAB/Simulink to simulate the discharge process, and a 50-T/120-ms flat-top pulsed magnetic field with an accuracy of 400 ppm is generated. [ABSTRACT FROM AUTHOR]

This paper presents a novel three-coil reconnection electromagnetic launcher (TCREL). Analytical calculations and simulation results indicated that not only does this model possess a higher structural strength, but also the launching efficiency is improved effectively compared with that of the traditional reconnection electromagnetic launcher (REL). In addition, take the TCREL model as an independent module; a toroidal REL (TREL) model can be obtained after several modules are uniformly placed and fixed around the circumference. The TREL model can reduce the magnetic flux leakage among driving coils, and further improves the launching efficiency. To verify the conceptual feasibility, two-stage TCREL and REL models were built and tested. The experiments demonstrate that the TCREL model possesses better launching performance than does the REL model; the former can obtain the desired launching efficiency of 15.818% but the latter only 8.248% in the contrast experiment. The experimental results are also in accordance with the simulation results. [ABSTRACT FROM AUTHOR]

The challenging demands of pulsed electron beam devices (such as the GESA device) with respect to their pulsed power supply have led to the development of a new semiconductor-based Marx generator. At a maximum output voltage of 120 kV and 600-A pulse current for a duration of up to 100 $\mu \text{S}$ , stepwise arbitrary output waveforms are desired. A fast rise time of the generator is achieved by using fast switching circuitry, low inductance capacitors, and a low inductance stage arrangement. For low jitter triggering of all stages and efficient signal transmission, the generator uses an optical bus system for communication. Due to the inherent dynamic load characteristics of the GESA device, the generator features a fast overcurrent protection scheme. This paper presents selected design aspects of the generator and their validation in a small-scale assembly able of delivering up to 8 kV at 600-A load current. [ABSTRACT FROM AUTHOR]

This paper presents the results of predictive calculations of the parameters of pulses of soft X-ray radiation (SXR) on a four-module electrophysical facility GAMMA-4 (the current pulse amplitude is ~3 MA with rise time of ~60 ns) that has been constructed in Russia. Scaling numerical simulation of implosion of a cylindrical single and nested multiwire array in 0-D, 2-D, and 3-D radiation magnetohydrodynamic– approximations is performed, taking into account, the updated double-loop equivalent electrical circuit of the GAMMA-4. The main purpose of the conducted studies was the numerical optimization of the multiwire array parameters to obtain the best characteristics of the SXR pulse generated as a result of Z-pinch implosion on the axis of the system. [ABSTRACT FROM AUTHOR]

An air-core strip-type high-voltage pulse transformer (HVPT) features a relatively simple structure in terms of design and fabrication. However, this HVPT requires considerable attention to prevent dielectric breakdown between the conductor windings. Because each spiral winding must be very thin, the field enhancement at the edges of the windings is very high. Therefore, it is important to develop proper methods to reduce the field enhancement factor and to prevent the dielectric breakdown at the winding edges. In this paper, in order to minimize the field enhancement, the proposed HVPT winding edges were folded, and each winding width was designed to decrease gradually to form a reverse trapezoid. These windings were insulated by multilayer insulators arranged in a specific manner. The requirement specifications are a maximum input voltage of 50 kV and an output voltage of 400 kV. This paper describes a design process and an electric field analysis to reduce the field enhancement. The simulation and experimental results confirmed the validity of the fabricated HVPT. The dielectric breakdown strength was tested up to 467 kV. [ABSTRACT FROM PUBLISHER]

Self-integrating Rogowski coil has been widely used for measurements of pulsed currents from nanosecond timescale to microsecond timescale in pulsed power systems. Appropriate designs of coil’s structure are vital to high-frequency response. This paper proposed a new structure of Rogowski coil so as to provide a better response to fast pulsed current. Four Rogowski coils with different structures were tested in three different platforms. Experimental results showed that the hybrid Printed Circuit Board Rogowski coil had the best performance in this paper, which could respond to square waves with fronts of $\sim 2$ ns and had a sensitivity of 0.585 V/kA. The designed maximal peak current was 100 kA. [ABSTRACT FROM PUBLISHER]

Electromagnetic launchers (EMLs) including railguns, helical guns, and coilguns have been proposed for numerous applications. However, the scaling characteristics of EMLs are unknown. This paper examines the nonlinear operating characteristics of EMLs and derives the operating voltage and current scaling relationships as determined by the mass and velocity of the projectile and the length of the launcher. The scaling relationship is derived using the kinetic power relationship common to all types of EMLs. The scaling relationship is expressed as a simple function of the projectile velocity, projectile mass, and launcher length. This paper also defines the impedance of an EML. The accuracy of the scaling relationship and the EML impedance are verified in a comparison with the experimental results of practical EMLs. The effects of resistive losses and inductive energy storage on the scaling relationship are included in the analysis. [ABSTRACT FROM PUBLISHER]

Paralleled pulse-forming units (PFUs) with different triggering delays might be a paramagnetic way for generating flat-topped current wave for electromagnetic launch. Many researchers have reported that multiple capacitive storage PFUs were implemented such current waves in laboratories. However, due to its low energy density, the applications of the capacitive pulsed-power supplies are limited. Since the inductor has advantages in energy density, the inductor pulsed-power supply becomes one of the hottest topics recently. The slow transfer of energy through capacitive hybrid meat grinder with inverse current commutation with semiconductor devices proposed by Tsinghua University has demonstrated its advantage and applicability recently. Using this kind of topology, this paper proposes the design of an inductive storage PFU with a stored energy of 100-kJ. The maximum load current reaches to 50 kA and its pulsewidth is at least 5 ms. The optimized inductive storage PFU shows superiority in contrast to the capacitive storage PFU with the same energy. This paper offers the theoretical analysis and the testing foundation for investigating the inductor pulsed-power supply with higher energy. [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 a novel brushless doubly fed alternator (BDFA) based on the differential mode and conducts research on its applications in a pulse capacitor charge power supply (CCPS). Since there are no brushes, the brushless doubly-fed alternator is expected to have high reliability and long service life. The excitation winding of the BDFA that is placed in the stator slots can be supplied with either dc or ac. In previous studies, regardless of the rotor configuration, the natural speed of BDFA is 60f/(p1+ p2) , i.e., based on the additive mode. To increase the alternator’s natural speed, expand the alternator’s operation as well as control range and to promote the alternator’s power density, this paper presents the differential mode, i.e., natural speed is equal to 60f/\vert p1-p2\vert . The author will introduce the detailed design method of the BDFA based on the differential mode. Utilizing the finite-element model of the alternator, we will analyze the magnetic field distribution and calculate inductance parameters of the BDFA. Subsequently, the inductance mathematic model of the BDFA will be established. We also establish the simulation model of the pulse CCPS. Finally, we will verify the feasibility of the design scheme for the BDFA through the simulation results in a pulse CCPS system. [ABSTRACT FROM PUBLISHER]

As power supplies, compulsators are popular choices for electromagnetic railguns. In this paper, a two-phase two-axis-compensated compulsator (2P2AC compulsator) with lower internal inductance and higher power density was designed and analyzed. Two-phase armature windings are allocated on the stator, and discharge pulse currents to the load via a rectifier. This arrangement decouples the machine speed from the pulsewidth, thus enables a higher tip speed. Two sets of windings with electrical orthogonal displacement are allocated on the rotor. The bigger one is the field winding that freewheels via a diode and provides the direct-axis compensation during the discharge process, while the smaller one is the short-circuit compensating winding providing the quadrature-axis compensation. The effect of the composition of the $d$ - and $q$ -axis compensation is equivalent to a passive compensation using a continuous conductive shield, which compresses the flux for all rotor positions. Compared with the passive compensation, this arrangement has no conductive path to couple with the field winding due to the orthogonal displacement, thus speeding up the charging process. This paper presents the design methodology of the 2P2AC compulsator, along with its system performance of driving railgun load. [ABSTRACT FROM PUBLISHER]

Matching devices in the form of electro-exploded current opening switches (EEOSs) or explosive current opening switches (EOSs) are used for transforming current pulses of magnetocumulative generators (MCGs) into voltage pulses of hundreds of kilovolts at high-impedance loads. Current pulse sharpening is accompanied by significant losses of the stored energy. Using EOSs are more preferable to EEOSs from the point of view of the energy losses since it does not lead to efficiency decrease in the MCG operation. This paper considers magnetocumulative multimodule systems consisting of several synchronously operating and serially connected small helical MCGs. Each generator is equipped with an explosive current opening switch. The voltages generated at each opening switch are summarized into the load. Fast operation of MCGs allows using very thin foils in the opening switches and obtaining the short voltage pulse front. Results of the works on creating high-voltage devices based on helical MCGs of a 60-mm diameter and disk EOSs of a 200-mm diameter are presented in this paper. In the experiment, the device consisting of two modules provides a voltage pulse of 370 kV with a rise time of $\sim 170$ ns into a load of 29 $\Omega $ and an inductance of 0.5 $\mu $ H. Maximum power in the load is $\sim 4.3$ GW, and the emitted energy is $\sim 1.1$ kJ. The four-module device forms the pulse with the characteristic current rise time of $\sim 100$ ns in the similar load at twice smaller current. [ABSTRACT FROM PUBLISHER]

Nowadays, disk magnetocumulative generators (DMCGs) are the most powerful and power-consuming magneto-cumulative generators (MCGs). The problem of necessary initial energy supply to the generator circuit is very urgent at creating high-performance disk generators. Preliminary energy amplification in experiments with DMCG is provided with helical MCGs. Along with preset energy supply, the preamplifier should have small characteristic current rise time. It is necessary for decreasing thermal and mechanical supply current effect on elements of the disk generator. This means increasing the output power of the preamplifier and associated with obtaining maximum possible initial energy in the DMCG. Initial inductance and resistance of the DMCG circuit became higher with an increase of the DMCG sizes and the number of its elements. This required increasing the power of earlier used preamplifiers. This paper presents experimental results of the MCG-240 characteristics improvement at the expense of turns distribution change and application of more powerful explosive. Other possibilities of the preamplifier power increase are considered in this paper. [ABSTRACT FROM PUBLISHER]

Electromagnetic induction coilgun systems have been receiving great attention, recently, due to the advantage of noncontact between the stator and armature coils. Several studies present the simulation and analysis of the coilgun system by using the finite-element method. However, there are still deficiencies in current modeling studies of the coilgun system. This paper presents a design of a multistage pulsed power induction coilgun system using the Taguchi method to maximize its efficiency and reduce the time and cost of the design process. A coilgun system is analyzed and designed using a state-space equation system. The Taguchi method is applied in order to evaluate and determine the geometric variables, the layer, turn layer numbers for both the stator and armature coils, and the trigger positions of each stage. Then, a 2-D finite-element model of the coilgun system using the MagNet program was developed to compare the design and analysis results. The energy efficiency of the three-stage coilgun system is 31.3%, and this is expected to increase with the increase in the number of stages. [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]

This paper puts forward a repetitive high-voltage pulse modulator, consisting of a step-up pulse transformer to decrease the number of needed semiconductor switches, and a bipolar Marx generator to reduce the turns ratio of PT, leakage inductance, and distributed capacitance, and also to improve the pulse shape. An equivalent circuit of the proposed modulator considering parasitic elements is established. Based on the equivalent circuit, circuit operation is analyzed in detail. In order to verify the theory analysis and circuit operation, simulations are conducted. In addition, a laboratory prototype is implemented. The simulations and experimental results of resistive load and dielectric-barrier discharges load turn out matched quite well with the theory analysis, demonstrating that the prototype can operate with a voltage amplitude in the range of 0–25 kV, a repetition rate of 0.1–5-kHz stably. [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]

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]

Repetitive high-voltage square pulses are of great importance for producing long-pulse electron beams and high-power microwaves. One of possible technologies for the generation of such pulses is a Marx generator using pulse forming network (PFN) stages, often combined with a pulse sharpening technique to reduce the rise time to a few nanoseconds (peaking stage). This paper presents an innovative design, named the “zigzag design,” for the optimization of the compactness and of the rise time of 400-kV–85-ns PFN-Marx. Thanks to this design, the 16 stages of this generator, which delivers an open circuit output voltage of 720 kV, fit in a 650-mm length. For a slightly overmatched load ($Z_{\mathrm {load}} = 100 ~\Omega$), the output voltage reaches 400 kV with a rise time as less as 5 ns. The inductance reduction associated with the innovative zigzag design, which allows this sharp rise time with no need for a peaking stage, is described. The 85-ns plateau duration of the pulse is given by the PFN construction of each stage, which is based on six ceramic capacitors (2.1 nF–45 kV) connected within a strip line. The 16 PFN stages are housed in a 360-mm diameter gas pressurized vessel. Burst mode operation for a duration of 10 s at a pulse repetition frequency of 100 Hz is reported, for a resistive load and for the electron beam diode of a X-band relativistic backward-wave oscillator (BWO). To reach further compactness, the BWO system is integrated on side of the generator vessel and a U-shaped gas pressurized line connects both systems through a compact conical vacuum insulator. [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]

This paper presents a new capacitor bank topology for a pulsed power system to improve the efficiency of multistage synchronous induction coilgun. In the proposed method, a switch, such a gate turn-off thyristor, is inserted in parallel to a crowbar diode and load to generate an attractive force between the next stator and the armature. A mathematical model was developed, and finite-element method simulations were conducted to verify the proposed topology. The results show that the proposed method improves the energy efficiency and launch velocity. The improvement in energy efficiency is confirmed from the simulation results of a three-stage synchronous induction coilgun. [ABSTRACT FROM AUTHOR]

In this paper, the results of a 2.88-MW solid-state long-pulse modulator, which has been designed for the new linear collider at the european spallation source in Lund, are summarized. The presented modulator generates an output voltage pulse of 115 kV with a pulselength of 3.5 ms. The main components of the modular system, which include a series–parallel resonance converter, a high-voltage high-frequency transformer, and an output rectifier, are discussed. The modulator design is verified by measurements performed with a full-scale prototype, which is operated under nominal load conditions. A detailed output voltage ripple evaluation is given, and in addition, the system design has been proven by a 7- and 2/3-h heat run test. All specifications are well within the given limits, and the maximum occurring temperatures in the transformer stay below 110 °C even under worst case assumptions. The system achieves a pulse efficiency (determined by the pulse shape) of 96.78%, an overall electrical system efficiency of 91.9%, and a combined pulse system efficiency of 89%. [ABSTRACT FROM AUTHOR]

This paper suggests a design of pulsewidth modulation series-resonant converter (PWM SRC) for magnetron power supplies. The goal of this design is to make the PWM SRC have a wide output voltage maintaining mode 3 operation that shows good switching characteristics. To keep the mode 3 operation, a systematic design is required because the design is related to various parameters, such as resonant tank, transformer turns-ratio, magnetizing inductance, and duty-ratio. To establish the design procedure, converter analysis is performed related to the steady-state operation, input–output relationship, and critical design conditions, and several design equations are derived based on the analysis. Based on the design procedure, a PWM SRC with parallel-input-series-output-connected transformer has been designed for magnetron power supplies and verified. [ABSTRACT FROM AUTHOR]

Inductive pulsed power supply (IPPS), especially superconducting pulsed power supply (PS), has been the focus of research in recent years due to its high energy density and low power requirement for the input PS. Quite a lot of fantastic work regarding two or multiple IPPS modules has been presented. But they disregard the mutual inductance between modules. This paper establishes a double-module IPPS based on two high-temperature superconducting pulsed power transformers and takes the mutual inductance between modules into consideration. The influence of the mutual inductance between two modules on three discharge modes of the system is researched. Simulations and experiments on synchronous discharge, time-delay discharge, and asynchronous discharge are carried out, respectively. The results demonstrate that taking the mutual inductance into consideration, the amplitude and the pulsewidth of the output currents are both improved a lot, especially the obtainable energy of load is improved by nearly half. For time-delay discharge, the mutual inductance makes the delay time slightly increase. However, for asynchronous discharge, the mutual inductance increases the positive maximum value of the primary current of the second module. It may exceed the critical current and lead to quench. Consequently, the mutual inductance between modules has positive impacts on synchronous discharge and time-delay discharge of the IPPS system while it brings both advantages and disadvantages to asynchronous discharge. [ABSTRACT FROM AUTHOR]

Based on high pulsed-power technology, electrical explosion is increasingly utilized to generate shock waves (SWs) with high pressure and short duration. To further magnify the SWs, we have proposed a novel technique by using energetic material (EM) loads. In this paper, we investigated the SW characteristics of ammonium nitrate (AN) powders ignited by the plasma of different kinds of refractory wire explosion. Evident results suggested that compared with $\Phi ~0.5$ -mm wires, $\Phi ~0.2$ -mm molybdenum and tantalum wires were able to finish vaporization, undergo the breakdown and eventually produce stronger SWs. After introducing the AN powders, the peak pressure of SW was scarcely enhanced, while the duration was significantly increased. Moreover, it was implied that various factors would affect the SW characteristics, including the EM charge density, the diameter, and material of metal wire. Finally, a simple plasma ignition mechanism based on multifactors was proposed. [ABSTRACT FROM AUTHOR]

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