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This paper is focused on using plasma as element of a frequency selective surface (FSS). FSSs have been used for filtering electromagnetic waves for many years. Conventional FSSs use metal patch pattern as periodic element. This paper takes the plasma tube as a substitution for metal patch. The 3-D finite-difference time-domain method with periodic boundary condition is utilized to simulate the interaction of incident wave and plasma FSS. Numerical calculation results in that electron number density of plasma can dominate the resonance frequency obviously. The resonance frequency increases as the increasing of electron number density of plasma to the limit of that of perfectly electric conductor. Thus, the FSS can be designed to be tunable by changing the ionized electron number density. Both of the noncollision and collisional plasma model are introduced to study the FSS characteristics. The numerical calculation results show that the collision frequency only influences the reflectivity while has no effect on the resonant frequency. The resonant frequency and transmitted power ratio can be tuned by assigning the plasma’s electron number density and collision frequency. Thus, plasma elements offer the possibility of improved shielding effect along with reconfigurability. Plasma FSS can also be made transparent by tuning the plasma off which makes the use of FSS more versatile. [ABSTRACT FROM AUTHOR]

Bar-plate configuration has a vital function in the intensive study of corona discharge mechanism. To study the discharge characteristics of the steady current stage in this configuration, this paper proposes a hybrid numerical algorithm composed by the finite-element method and the finite-volume method. The former solves Poisson’s equation and calculates the value of onset field intensity. The latter solves the current continuity equation, in which a time-varying charge item is added. This charge item can increase the stability of the hybrid algorithm. This paper also proposes a new selection strategy for the initial charge and inception voltage on the bar electrode surface. Based on this algorithm, corona current under different electrode radii, gap distances, and applied voltages was calculated. In this way, the distribution characteristics of an electric field intensity and space charge density along the whole gap in the model can be obtained through the experiment. To verify the validity of the algorithm, the related experiment is carried out in the laboratory. The simulation results have a good consistency with the experimental results, verifying the validity of the algorithm proposed in this paper. [ABSTRACT FROM AUTHOR]

Modeling of the structural behavior of the housing of an electromagnetic railgun is usually carried out without considering the electromagnetic origin of the forces; the magnetic pressure acting on the rails is assumed to act at the rail surfaces only. This approximation proves to be a great challenge, as moving pressure profiles at speeds of a railgun projectile are very rare in purely mechanical investigations. In the past, we have published several papers on the structural mechanics of railgun housings characterized by discrete supports. We could show that the displacement of rail surfaces at the position of the armature can reach amplitudes that are not negligible. In fact, in the case of metal brush armatures, the increase in distance between the rail surfaces of only tenths of a millimeter can make the difference between the solid contact and arcing to increase. We also matched our findings to experimental data that were, however, so far only gained in static tests. In this paper, we analyze the foundations of our mechanical modeling using electromagnetic calculations. We calculate a 3-D distribution of the $J \times B$ volume force density in the rails and use them as input for our structural mechanics model. A second point to be addressed concerns the parts made from conducting materials, such as our discrete supports made from steel bolts, which are situated in rapidly changing magnetic fields during the experiments. Again, the influence on our structural mechanics modeling is discussed. [ABSTRACT FROM AUTHOR]

Electromagnetic pulse forming (EMPF) is an attractive manufacturing method using pulse power techniques. Temperature rise of the work piece is usually neglected in previous studies because the forming process is regarded as a cold process. Nevertheless, the temperature rise (if not high) also has influence on the forming process. It is important to study the temperature rise for exploring the related law in the process of EMPF. In this paper, the thermal effect in the process of EMPF, caused by the joule heating generated by the high current and the plastic work produced by the plastic deformation of the work piece in the forming process, is discussed though simulations and experiments. A finite-element simulation coupled with the electromagnetic field, plastic mechanics, deformed geometry, heat transfer, and thermal expansion based on COMSOL multiphysics is established to show the detailed thermal effect in this process. The relationship between parameters of work piece and the thermal effect has been analyzed by comparing different materials and thicknesses of work pieces. The simulation results show that the temperature of work piece has changed because of the thermal effect. A high-current pulse generator has been developed for the experiment of EMPF to verify the results of simulations. This paper describes the forming experiments of different materials and thicknesses. And the experimental results verify that the materials and thickness of work piece affect thermal effect during the process of EMPF. Compared with the Joule heating, the plastic work is the main cause of the thermal effect. Moreover, the thermal expansion caused by temperature rise could affect the forming results and material property. [ABSTRACT FROM AUTHOR]

The intelligent estimation method (IEM) is based on approximations which can be described by the configuration and behavioral characteristic of the problem. This paper used the IEM in time domain (IEM-TD) which can be utilized to predict the current distribution and maximum current density. A detailed IEM technique to compute the current distribution over the surface of a rail, current profile around the rail, and maximum current density ( J\max) formula will be presented in this paper. The current distribution is computed for rectangular and circular rails that are shown in color figures. Finally, this paper considers the effect of the rail dimensions and material on these parameters that are shown in several figures. The results of this paper are compared to other published studies and FEM simulation. [ABSTRACT FROM AUTHOR]

The current density and electromagnetic force distribution of the armature directly affect the performance of electromagnetic railgun. In this paper, the electromagnetic thrust, electromagnetic pressure, and current density of the C-shaped armature and H-shaped armature are calculated, respectively, by the finite-element method under different Armature–rail contact modes (different contact areas and positions), and the calculation results under different contact modes are compared. The calculation results show that the maximum current density of the armature head is independent of the contact mode, and the position of the maximum current density of the armature tail moves with the advance of the contact position. The separation of the rear part of the armature tail and rail will result in a sharp decrease in electromagnetic pressure, so the armature tail and rail need to maintain contact to ensure a stable current transfer. At the same time, only the head and the rear part of the armature tail are in contact with the rail, the electrical performance of the armature in complete contact with the rail can be achieved. Therefore, the armature adopts the structural design scheme of interference at both ends, which is more conducive to electromagnetic emission and greatly reduces the difficulty of the armature structural design. [ABSTRACT FROM AUTHOR]

This paper discusses the design, fabrication, and analysis of a coil assembly for a multistage induction-type coilgun system with the pulsed power module. The voltage, current, force, velocity, acceleration, and efficiency of the coilgun system were analyzed using the finite-element method. Based on the results of the electromagnetic analysis, the geometry of the coil assembly part for coilgun system was defined. The designed coilgun system has been found to exhibit high energy efficiency and safety against the force and temperature of the coil assembly. The designed coil assembly part was fabricated and analyzed. The design specifications and analysis results concerning the coilgun can, hence, be effectively utilized to develop a large-scale multistage induction-type coilgun system. [ABSTRACT FROM AUTHOR]

Paschen’s law gives the inception voltage for an electrical discharge as a function of the product of gas pressure and the gap distance between the two infinite planar electrodes. It is known that the deviations from Paschen’s law occur when the temperature is increased. Historically, two theoretical corrections, the Peek and Dumbar corrections, are proposed to predict the deviation from Paschen’s law by increasing the temperature. To carry out an experimental investigation on the deviation from Paschen’s law by increasing the temperature, a customized system was designed, which can operate at temperatures up to 400 °C and at pressure up to 1 MPa, calculated at room temperature, with an interelectrode distance between $100~\mu \text{m}$ and 6.6 mm and an error on the interelectrode distance measurement of $20~\mu \text{m}$. In this paper, first, the results from the experimental investigation on the deviation from Paschen’s law at temperature up to 400 °C are presented. The results are then compared with theoretical corrections, and finally, a theory to explain the results is proposed and discussed. [ABSTRACT FROM AUTHOR]

Virtual engineering is being widely adopted in diverse technical fields and has the potential to accelerate the realization of tokamak fusion energy. In this paper, we demonstrate, for the first time, the use of virtual engineering techniques to enhance the development cycle of a water-cooled divertor plasma facing component. The divertor concept under development is the thermal break, which aims to increase heat flux limits and DEMO-relevance by alleviating the high thermal mismatch stress between a tungsten monoblock and a copper alloy cooling pipe. Response surface-based design search and optimization is used to explore the potential of the concept and to inform the design of a high-heat-flux (HHF) mock-up. In developing a brazing manufacturing procedure, computed tomography scanning and subsequent image-based finite-element modeling revealed a defective joining process which would result in unacceptable divertor performance. The same techniques were used to develop an improved brazing procedure that was used to manufacture the mock-ups. A production defect was discovered by ultrasonic qualification testing, but a “virtual twin” model confirmed the acceptable performance of the mock-up under HHF. Indeed, all mock-ups were then subjected to at least 100 cycles of 20 MW/ $\text{m}^{2}$ HHF testing, with no signs of damage. The development of these virtual engineering and modeling techniques will facilitate criteria for design and component rejection, and in future enable predictive maintenance of components in service. Practical trials and experiments will remain essential to complement and validate simulations. [ABSTRACT FROM AUTHOR]

Barrel and pulsed power supply modules are two crucial parts of an electromagnetic launcher (EML), in terms of overall efficiency. One of the most important features of the barrel side is the armature geometry. In this paper, the shape of the armature of an EML with 10-MJ current pulse generator, 1000-kA peak current, and 4.5-ms excitation time is optimized by using independent variables to define the exact geometry of the armature. The main goal is to maximize the muzzle kinetic energy of the projectile with 300-g mass including pressure and contact current constraints. Finite-element method (FEM) is used to calculate the muzzle kinetic energy of the EML for different armature geometries. Genetic algorithm is used as the optimization method. Since the contact resistance between the armature and the rail affects the distribution of contact current density, contact resistance is also modeled in FEM. It is observed that armature shape optimization study increases the muzzle kinetic energy to 596 kJ and the muzzle velocity to 1993 m/s. [ABSTRACT FROM AUTHOR]

As an attractive power supply for high energy level pulsed power applications, such as long range electromagnetic railgun, electromagnetic aircraft launch system, and high-energy laser, multiple pulsed alternators can not only meet the high energy level requirement of the load, but also lower the requirements of the power electronics in the system. Utilizing multiple pulsed alternators work together also makes the control strategy of the system more flexible. In order to improve the efficiency of the whole system, a novel control strategy of an air-core pulsed alternator pair is proposed in this paper. Like a single pulsed alternator, the whole work process of the pulsed alternator pair can also be divided into three subprocesses: the self-excitation process, the discharge process, and the energy reclamation process. In the self-excitation and energy reclamation processes, the armature windings of the pulsed alternator pair are connected in series, and the filed windings are connected in parallel. In order to illustrate the advantages of this control strategy, a comprehensive discussion of different connection topologies of the alternator pair has been made in this paper. A mathematical model based on the equivalent circuit of the air-core pulsed alternator considering the harmonic components was also established in this paper, which could help calculating the system efficiency more accurately. The results and conclusions of the analyses and simulations can offer guidance for the air-core pulsed alternator pair system design and optimization. [ABSTRACT FROM AUTHOR]

This paper deals with shielding resonator structures for possible application in electromagnetic rail launchers. The main aspects of the resonant shield are revisited via the spatial averaging concept of macroscopic quantities and of the effective magnetic behavior. In particular, it is recalled how for a resonator structure it is possible to get negative values of the effective permeability and it is shown how this can be exploited for shielding applications. Simulation results are obtained via a commercial finite-element code through a 3-D frequency analysis. The shielding effectiveness is estimated at different operating conditions by varying the resonance frequencies of the shield, while maintaining the constant field operating frequency. Possible advantages and critical aspects of such an approach are discussed throughout this paper, and an estimation of the thrust force acting on the projectile is also provided. [ABSTRACT FROM PUBLISHER]

The pulse transformer is used in many applications to provide high-voltage pulses. In order to obtain high and narrow output pulses, it is necessary to reduce the leakage inductance of the pulse transformer. The circuit of a high-voltage power supply is analyzed and simulated to study the effect of the leakage inductance on the pulse waveform. Afterwards, the winding structure is analyzed. Three transformer models were built based on the asymmetric parallel winding, the traditional parallel winding, and the taper winding. Their leakage inductances and parasitic capacitances are calculated and compared. The 3-D finite element simulation is adopted to compute the leakage inductance precisely. The simulation results demonstrate that the asymmetric parallel winding in this paper reduces the leakage inductance effectively with small parasitic capacitances. In addition, using the asymmetric parallel winding, a pulse transformer prototype is manufactured and tested. The experimental results verify the accuracy of the simulation method and the feasibility of the asymmetric parallel winding. [ABSTRACT FROM PUBLISHER]

Since a tactical electromagnetic railgun system is required to fire several times a minute, the thermal load on the rails leads to a higher temperature, which will even result in launch failures and reduce the life span of the launcher. In this paper, the rail temperature was measured during the launch experiment. Furthermore, based on a 3-D transient model with moving armature, mechanically, thermally coupled electromagnetic field analysis using finite-element method is presented. The Joule heating is one of the main heat sources in the rails. Contact resistance and friction force that cause heat between the armature and the rail are also included in the model. The simulation results show that the peak temperature in the rail occurs at the inner surface. Overall, along the direction of armature motion, the temperature of the rail near the breech end is higher than at the muzzle end, and the maximum temperature on the rail appears near the initial position of the armature. The contact resistance contributes much more than friction to the temperature rise in rails. [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]

Electrical machines with transverse-flux (TF) paths have flexible structures, which may help to improve the performance of machines. Comparing to the flat-type structure in linear machines, the tubular-type structure is good for improving the electromagnetic thrust density. In this paper, a novel single-phase tubular-type switched reluctance linear launcher with TF path is proposed. Its stator is composed of several U-shaped modules, and windings are coiling on the yokes of these modules of the stator. This structure differs from the traditional tubular linear machine, and it avoids two windings squeezing in one stator slot so that the winding assembling process is easy. Gear-shaped poles on mover form more effective magnetic circuits than conventional machines. In the design process, the sensitivity analyses on five important parameters are conducted with the finite-element method (FEM) to achieve better performance on thrust density. The prototype has been manufactured and tested. The static and dynamic performances measured through experiments coincide well with the simulation results. These prove the correctness of the calculated FEM results and the well-manufactured machine, and its superiority in thrust density is verified. [ABSTRACT FROM AUTHOR]

In previous studies, the field winding of the brushless pulsed alternator (BPA) is embedded in the stator slots, which is supplied by dc power or variable frequency power. The advantage is that the field current can be independently adjusted. It means that the BPA system needs a standalone excitation system, which will increase the volume and cost of the system. If we substitute electric excitation for permanent magnet excitation, not only the volume and cost of the BPA system can be decreased but the efficiency and flexibility can be enhanced. In this paper, the design schemes for electric excitation and permanent magnet excitation BPA are presented. For comparison, the stator and rotor dimensions of the two kinds of BPA are both the same. The characteristics of electric excitation and permanent magnet excitation BPA are analyzed by the finite-element method and field-circuit coupling method. Finally, the BPA systems with a resistive load are established, the performances of both the two excitation modes are compared. According to the simulation results, we conclude their advantages and disadvantages. [ABSTRACT FROM AUTHOR]

Sliding electrical contact between rail and armature in rail launchers is characterized by high speed and large current. Melt erosion is caused by the current concentration on the contact surface of armature. This current melt erosion (CME) has been experimentally studied in the current range of 10–20 kA/mm with a 20-mm caliber lab-scale rail launcher, and payload separated method was used to keep the recovered armatures intact. Thus, the onset behavior and erosion patterns of CME can be successfully observed in such relatively low current densities. In this paper, we will further our study to analyze the patterns of CME with the increasing current densities under the effect of different initial mechanical contact force. Results show that CME all start at the side edge, and then spreading longitudinally and transversely with the increase of current. It is found that the starting position of CME appears near the trailing edge at small mechanical contact force and moves to the leading edge with larger mechanical contact force. At the same current magnitude, erosion amounts are much more under small mechanical contact force. Stationary mechanical contact pressures and current distribution of armature surface are simulated to investigate the effect of initial mechanical contact force on starting position of CME. Current distributes at the edges of actual contact zone and the maximum of current density appears at the side edges of armature. As the initial mechanical contact force increases, actual contact zone and current density move toward to the leading edge from trailing edge. It can be confirmed that the erosion starting position is at the side edge along actual contact zone and will move toward to the leading edge from trailing edge with the increase of initial mechanical contact force. Smaller initial mechanical contact force will cause more erosion at the same current magnitude because of larger current density. Furthermore, an average friction coefficient calculation method is proposed to evaluate the melt lubrication effect of CME. The result shows that the lubrication effect becomes better with larger current densities. [ABSTRACT FROM AUTHOR]

This paper presents a novel finite-element modeling of interelectrode plasma dispersion process inside a vacuum interrupter (VI) prototype. A new set of coupled equations considered for the plasma simulation process consisting of the Stefan–Maxwell diffusion equations, collision and interaction between particles considerations, and Coulomb integral for conductivity calculation of plasma are utilized to give a better understanding from complicated vacuum plasma dispersion process inside a VI. Using SolidWorks software, an exact 3-D schematic of the prototype is drawn and imported to the proper finite-element method software. Considering suitable boundary conditions and proposed plasma equations set, including 10 kV/ $\mu \text{s}$. The ramp function as a transient recovery voltage inserted to the contacts, the model is dynamically simulated, and the derived results have been discussed in detail. In continue, postarc current waveform is derived using the Maxwell equations. This result is compared to a practical-based common model which is named the Andrews–Varey transition model. The derived postarc waveforms are compared in a table. The similarities of results, for example, postarc time (difference between two models is less than 8%) or maximum value of postarc current (difference <7.5%), ensure the accuracy of the new proposed plasma modeling strategy. [ABSTRACT FROM AUTHOR]

We numerically model the ablation process of a 25- $\mu \text{m}$ -thick aluminum foil driven by a pulsed-power machine that provides a 1-MA peak current in a 100-ns zero-to-peak rise time. The extended magnetohydrodynamics simulation is a discontinuous Galerkin code with Cartesian coordinates in 3-D and with 25- $\mu \text{m}$ spatial resolution. We investigate the influence of an external magnetic field normal to the foil surface, $B_{z}$. During the foil ablation, $B_{z}=1$ T causes more nonuniform distributions of density and current compared to $B_{z}=0$ T. $B_{z}=4$ T delays the generation of surface plasma relative to the 0- and 1-T cases. The understanding of a material’s ablation as it undergoes transition from the solid to plasma phases requires detailed knowledge of a material’s equation of state and conductivity. This paper of warm dense matter and how instabilities propagate from a solid material to plasma motivates improvements to both numerical simulations and experimental diagnostics. [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]

This paper presents the calculation results of the initial axial magnetic field compression by the cylindrical multiwire array, powered by the pulsed power electrophysical facility Gamma. (The current pulse amplitude with 16 modules is ~11 MA, and rise time is ~60 ns.) The facility is being constructed in RFNC-VNIIEF and presently has four operating modules. [ABSTRACT FROM AUTHOR]

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]

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]

Thermal energy in railgun is unwanted and generated by ohmic losses that are dependent to the current implied, rail dimensions, electrical conductivity (\sigma), and specific heat (CP). \sigma and CP are functions of temperature. Using achievement L^\prime formula by intelligent estimation method, the current density and ohmic losses on the cross section of the rail are computed. Ohmic losses are the source heat and utilized heat equation that are used to compute thermal distribution and temperature that are compared with other results in some papers. This paper chose h = 30\ \mm, w = 10\ \mm, and copper for the rail material and a method to compute the thermal distribution on the surface of the rail and side rail edges. Effects of rail dimensions on the temperature in time domain are calculated and shown in the figures. Rail materials are investigated with copper and aluminum in which the average temperature of both materials on the rail surface is calculated and compared. [ABSTRACT FROM AUTHOR]

Multipole field reconnection electromagnetic launchers are highly efficient electromagnetic transmitters, which can solve the inherent flaws in conventional electromagnetic launchers such as the small axial thrust and the sliding contact. In addition, there are many tunable parameters for this launch mode. In order to improve the acceleration performance, the axial acceleration force, the efficiency of the system and influence of capacitor parameters on the emission performance is focused in this paper. Some theories about this launch mode is introduced. A finite-element model of the system was constructed and the commercial finite-element software Ansys Maxwell was applied. The simulation results indicate that increasing the voltage and capacitance of the capacitor can improve the axial acceleration force of the projectile, but the efficiency of the system may not be enhanced. We proposed that it should be appropriate to reduce the capacitance, while increasing the charging voltage value at high-speed launch. [ABSTRACT FROM AUTHOR]

Electromagnetic force on rails of railgun is the effective factor which impacts on input current pulse, rails and armature geometry, dimensions, and materials. This paper investigates how the stimulated current form affects the electromagnetic force on rails. A transient analysis with a finite-element method is discussed to simulate a 3-D railgun in this paper. In the first section, we consider the effect of flat-top length of stimulated current pulse on electromagnetic force distribution on rail and armature velocities. In the second section, we consider the effect of stimulated currents that have the same areas but have various amplitudes and flat-top lengths and at the last section, the flat-top length and amplitude of current are exactly the same, but the flat-top part replaces during time. Consequences are shown in several figures. [ABSTRACT FROM AUTHOR]

Induction coil launcher (ICL) is an electromagnetic accelerator that uses Lorentz force to accelerate a projectile with a conducting armature. In this paper, the effects of the height and starting position of the armature on the performance of the ICL were analyzed. Launching experiments were conducted to verify the analysis results. The speed of the projectile converged to a saturated value as the armature height increased. We found that there exists an optimal starting position of the armature for the highest speed. The concept of inductance gradient was adopted to explain the analysis results. It was possible to predict the acceleration characteristics and to estimate the optimal starting position using this concept. Results show that the armature height should be longer than the drive coil height ( \textH\mathrm {coil}) , and the bottom of the armature should be positioned between (1/4)H\mathrm {coil} and (1/2)H\mathrm {coil} at the start to obtain the highest speed. The experimental results showed good agreement with the simulation analysis results. [ABSTRACT FROM AUTHOR]

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]

The static and dynamic voltage distribution characteristics and voltage sharing design of a 126-kV modular triple-break vacuum circuit breaker (VCB) was discussed in this paper. The finite-element method and power frequency tests were used to calculate and verify the static voltage distribution ratios and distributed capacitance parameters of multi-break VCBs, respectively. A model combining the post arc current model and equivalent capacitance model was proposed for simulations of dynamic transient recovery voltage (TRV) distribution characteristics of the triple-break VCB. The simulation results indicated that besides the stray capacitances, the TRV sharing design should take the influence of residual charge (RC) into account, and the influence of RC on the TRV distribution is relevant to the differences of RC parameters among the series interrupters. Therefore, the appropriate value of grading capacitors should meet the requirement of the worst case. Based on the investigation of this paper, a 126 kV U-shaped triple-break VCB prototype with 1000 pF grading capacitors has been produced, and the successful large current breaking tests indicate the good breaking capacity and suitable voltage sharing design of the triple-break VCB. [ABSTRACT FROM PUBLISHER]

This paper proposed a railgun with sector of circular rails. The center of the sector of circular rails is located at the outside of the railgun bore. The distance between the sectors of two circles is s , opening angle facing outward \theta , the inner and outer radius are also assumed to be Ri and Ro , respectively. The influence of internal curvature of the rails, the rail thickness and the distance between rails on the current density, magnetic flux density, and inductance gradient ( L' ) have been studied and analyzed using finite-element method. First of all, the different values of \theta , s , , and R_{o} are calculated for various values of the area of the railgun bore ( S_{C}) and cross section of the rails ( SR) . The current density, magnetic flux density, and L' have been calculated for different values. The area of the railgun bore is assumed to be 9 and 10 cm ^2 and the area of rails are assumed to be 9, 6, 3, and 1 cm ^2 . In next section, L' is found as a function of s , Ri , and Ro for \theta =90 ^\circ , 120°, 150°, and 180°. Finally, $L'$ is compute for rail thickness equals to one-tenth of bore size and $\theta $ on the interval [180°, 360°]. According to the achieved results it can be observed the behavior of $L'$ in terms of railgun dimensions changes and it is compared with other geometries. [ABSTRACT FROM PUBLISHER]

This paper deals with the 3-D finite element method (FEM) analysis of a novel magnetic levitation (maglev) train driven by an air-cored tubular linear induction motor. This new maglev system originates from electromagnetic launcher (EML) technology, especially linear induction launcher (LIL) type. Some 2-D magnetic analyses based on current sheet model or transmission line approach for the LIL type launchers are available in the literature, but this paper provides an alternative way to analyze LIL type of EMLs using 3-D FEM. The analysis examines the variation of propulsion, levitation, and guidance forces induced in the moving part. It is expected that the possible results of this magnetic analysis will lead to some new and important design considerations for the novel maglev system. [ABSTRACT FROM PUBLISHER]

Pulsed power systems often use a pulse transformer to generate high voltage pulses in some application such as radar systems, linear accelerators, and klystron modulators. Parasitic parameters include leakage inductance and capacitances are crucial for output waveform of pulse transformers. To ensure a rectangular pulse shape with a fast rise time, a required small overshoot and an acceptable voltage droop, theoretical calculation based on MATLAB is studied to optimize the design of the pulse transformer in this paper. Based on the theoretical calculation results, Finite Element Method simulations of magnetic and electric fields are carried out to obtain a more precise model for designing the transformer. Additionally, as the pulse transformer related in this paper works on the single forward state, a dc reset circuit, which can improve the utilization of the core material is implemented. Finally, accurate simulations of the pulse system equivalent circuit based on SABER are implemented. Meanwhile, output waveforms of pulse systems with different parasitic parameters and variable load are discussed. The simulation and experiment results showed that the optimum design of pulse transformer based on MATLAB programming and SABER simulation is effective to reduce the rise time of rectangular pulse shape to 1.5 \mus while the pulse duration is as large as 200 \mus. [ABSTRACT FROM PUBLISHER]

A 2-D discontinuous Galerkin time-domain (DGTD) scheme based on high-order hierarchical basis function is presented in this paper. Combined with the shift operator method solving the electromagnetic problem of dispersive media in finite-difference time domain, the iterative formula of DGTD method in dealing with plasma media is given. On this basis, taking the example of line element radiation, the computing ability of different basis functions is compared. To study the transmission characteristics of the electromagnetic (EM) wave in sheath, the DGTD calculation models of the plasma sheath of a blunt cone at different flight heights and velocities are established using Lagrange interpolation technique based on the calculation results of COMSOL (business software). The influences of antenna position, flight altitude, and flight speed on transmission characteristics of the EM wave are discussed through calculation and analyses. [ABSTRACT FROM PUBLISHER]

In this paper, a research on the damages of material caused by thermal stress in electromagnetic launch is presented. 3-D finite-element program is established to calculate the transient electromagnetic fields and temperature fields including a moving armature. The focus is mainly on the high temperature and large thermal stress damages to the rail. Thermal stress is produced by the current density concentration and defined as the skin effect. There are two main reasons for the current skin effect. One is due to the rapid changes of the current wave. The other is due to the moving conductors known as the velocity skin effect. The simulation results illustrate that with the influence of the current skin effect, the thermal stress will concentrate at a small area. This area may cause the grooving damage at startup, besides, the gouging damage at high velocity. Finally, the results are in agreement with the experiments. [ABSTRACT FROM PUBLISHER]

It is important to analyze the electromagnetic coupling characteristics in pulsed power supply (PPS) during the design, and electromagnetic force analysis is becoming more and more important with the development of large capacity and miniaturization of PPS module. In this paper, the magnetic force on the metal structure affected by the pulsed electromagnetic field of the reactor is analyzed and calculated by the means of the finite-element code ANSYS. The results show that the electromagnetic force on the metal structure near the reactor is about ten times that of other parts. The eddy current distribution is calculated by the electromagnetic coupling simulation while the stress on the metal frame is analyzed by the electromagnetic structure coupling simulation. The breaking point assumed to be the weakest point in the structure. The weakest point in the structure is indicated by structural stress simulation. The electromagnetic force is reduced by cutting off the main induce loop through simulation, and the eddy current is measured by experiments. [ABSTRACT FROM PUBLISHER]

In this paper, two kinds of abnormal rail-armature contact states are assumed and simulated, and the simulated B-dot probe waveforms are compared with the results from the experiments. Through theoretical analysis, simulations, and experiments, relations between the abnormal contact states and the output waveforms of the B-dot probe are investigated. Results show that with the help of the B-dot probe output waveforms, the transition position can be obtained and the intervals between the parallel circuit branches, which are created by the arcs arising from the abnormal contact states, can be primarily measured. [ABSTRACT FROM PUBLISHER]

Multiphase pulsed alternators use a thyristor converter to generate the direct current to power railguns. The desired current shape can be obtained by adjusting firing angles of thyristor. The discharge process of multiphase pulsed alternators is complicated due to a special air-core topology and the interactions between multiple current pulses, so the appropriate selection of firing angles only is obtained using a cut and try method within a system simulator. To quickly get the appropriate firing angle, this paper analyzes the discharge process of multiphase pulsed alternators. The calculations of the short-circuit current and transient parameters are obtained based on the classical theory of short circuit. Two types of interactions among multiple current pulses are revealed by theoretical deduction. A formula of peak current, relating to firing angles, is obtained. A finite-element method is used to verify the theoretical analysis. The results of those two methods are close and errors are acceptable. Therefore, the analysis of discharge process is valid. The analytical expression of discharge process can provide the theoretical guides for the selection of firing angles and current waveform control in the future. [ABSTRACT FROM PUBLISHER]

With the quick development of electromagnetic propulsion systems, permanent magnet linear synchronous motors (PMLSMs) have been the focus of research for high-performance propulsion systems. Compared with traditional windings, two ring windings with novel structures and better performance for PMLSMs are proposed: the single-layer ring windings are suitable for high-power systems; the double-layer ring windings can be adopted in low fluctuation systems. This paper first analyzes the electromagnetic parameters of the ring windings based on the equivalent magnetizing current method to verify the availabilities of ring windings. The main parameters of two ring windings are compared to achieve the optimization guides. Then, the magnetic fields and thrust characteristics of ring windings and traditional lap windings are analyzed by the finite-element method, and the independent magnetic field of ring winding ends is verified. And then a prototype motor with double-layer ring windings was manufactured and experimentally tested, the measurement data were matched with the theoretical calculations. The results illustrate that the PMLSM with ring windings has higher thrust density and lower thrust ripple, ring winding structure is more suitable for electromagnetic propulsion systems. [ABSTRACT FROM PUBLISHER]

Multisegmented dual-stator pulsed linear induction motor (LIM) is suitable for electromagnetic (EM) catapult based on the former research. This paper mainly analyzes the numerical model of same and reverse mode of the dual stator, magnetic thrust and EM parameters, and the magnetic field distribution has been built by finite-element model and the static performance are gotten by the prototype machine. Based on the analysis results and static experiments, the closed-loop control models for the dual stator have been established, and the dynamic launch test has been performed by using of multisegment prototype LIMs. The test results show that the dual-stator LIMs can accelerate the 300-kg load to the speed of 15 m/s within 11-m launch stroke. The fluctuation of the slip frequency is quite small and the block transition is smooth during the launching process. The test results show good agreement with the commanded values, which verify the dual-stator LIM model and control strategy. [ABSTRACT FROM AUTHOR]

With the development of electromagnetic launch (EML) technology, the pulsed power supply (PPS) module applied in EML needs to be smaller, lighter, and more compact. Electromagnetic force (EMF) is one of the most serious problems when PPS module works with high current. In this paper, we study the PPS module used in EML technology. The pulsed inductor model is built based on structure characteristics. The distribution of current density in the inductor during discharge is analyzed. The finite element analysis software is used to simulate and analyze the characteristics of the induction current and the EMF. The simulation model is composed of inductor and metals structures. The EMF laws are put forward by simulation of different shaped metals at different positions. By analyzing the distribution of the eddy current and EMF on the metal conductors at different positions, the EMF laws between the inductor and metal conductors in PPS module are presented in this paper. [ABSTRACT FROM PUBLISHER]

The dynamic response of an electromagnetic rail launcher (EMRL) has a direct influence on launch accuracy. With the Bernoulli–Euler beam located in the elastic support as an object of study, this paper presents an analytical model of the dynamic response of EMRL under the conditions of electromagnetic (EM) repulsive force and armature-and-rail contact force and obtains the analytical solution of the model. The redevelopment of the finite-element software makes it possible to perform a strong coupling transient simulation of the moving EM repulsive force, armature-and-rail contact force, moving thermal power, frictional thermal power, and the structural response in the dynamic launching process. Through the comparison of the results obtained by the analytical method, 2-D finite-element method (2-DFEM), and 3-D FEM (3-DFEM) for the dynamic response of the EMRL, the proposed model proves to be accurate and reliable. It is found that 3-DFEM can more accurately reflect the dynamic response process of the EMRL. On this basis, an analysis is made on the influence of the contact force, structural damping and heat on the dynamic response. The studies show that the contact force and the structural damping have little influence on the dynamic response under the condition of noncritical velocity, but have a great influence under the condition of critical velocity. However, the heat has a great effect on the dynamic response in both the conditions. [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]

Compensated pulsed alternator (compulsator) plays a significant role in the field of pulsed power supply. Different kinds of compulsators have been used to drive high-energy weapons. In this paper, the mathematical model of a two-phase four-pole air-core compulsator is established, taking the current coupling, the change of rotor speed and changing load characteristics into account. Both the self-excitation process and the discharge process are modeled. Simulation results indicate that our model has high accuracy in comparison with the results of the co-simulation method using finite-element method and circuit principle. Moreover, the usage of the mathematical model can improve the simulation efficiency and flexibility. The current pulse requirements of electromagnetic rail gun (EMRG), flash lamp, and electro-thermal-chemical gun (ETCG) are analyzed, respectively, and the pulse shape optimization problem is studied based on the intelligent optimization algorithm. For EMRG and flash lamp, the term “acceleration ratio” is introduced to identify whether a pulse is flat or spiked. For ETCG, the conception of “shape variance” is proposed to evaluate the fitness of its pulse shape. With the help of suitable objection function and intelligent optimization algorithm, the optimal discharge pulse for specific load can be obtained easily. [ABSTRACT FROM AUTHOR]

While Grover's tabular method to compute the mutual inductance of coaxial single-layer coils is convenient and fast when implemented on computer, its use has mostly been restricted to zeroth- and first-order calculations, since its accuracy is not well defined or quantified. This paper defines and quantifies the accuracy of Grover's tabular method for single-layer coaxial coils and shows that interpolation between the tabulated values is the primary factor limiting its accuracy. The results of this paper are used to develop an improved tabular-solution method that has accuracy approaching that of a finite-element field-code analysis. The analysis compares three mutual-inductance calculation methods for coaxial single-layer coils: a finite-element numerical method, an analytical method involving the numerical elliptic-integral evaluation, and Grover's tabular method. The finite-element numerical solution and the analytic solution are the most accurate and comparable to each other, while the tabular method is the least accurate. In terms of speed, however, the tabular method is the fastest while the finite-element method is the slowest. The interpolation techniques used in the analysis include cubic spline, cubic polynomial, polynomial, and linear. In comparison to finite-element numerical calculations, the improved tabular method developed in this paper decreases the computation time a factor of 4 × 103 while retaining an accuracy of at least four significant digits. The improved tabular method can be applied to similar-type problems that rely on the evaluation of elliptic integrals in their solution. [ABSTRACT FROM AUTHOR]

This paper presents the study and analysis of the error field of Joint TEXT tokamak. Error fields are first calculated through both the finite-element method and the theoretical method. Then, a Fourier decomposition of the error field is performed on the plasma surface to evaluate the lower mode ( $m$ , $n$ ) = (1, 1), (2, 1), and (3, 1) error fields. The results of the two methods are notably consistent. Superposition and linearity are also verified for small misalignments. The major sources of error fields are discussed by comparing the error fields caused by different misalignments of various coils. A Monte Carlo simulation, which combines the contribution of all the coils, is performed to obtain the total error fields. A comparison between the calculated and measured error fields is also conducted. The results indicate that the analysis method presented in this paper is very effective in predicting the error field. [ABSTRACT FROM PUBLISHER]

This paper presents an optimal design methodology of monolithic high-voltage (HV) pulse transformers based on the direct 2-D finite-element analysis (FEA) identification of the electrical equivalent circuit parameters without any simplified analytical modeling. This method is applied to the preliminary optimal design of the monolithic HV pulse transformer for the future compact linear collider modulators under study at CERN. The feasibility of such a transformer with tight specifications is demonstrated. The predicted performance obtained with the direct 2-D FEA optimization process is validated by 3-D FEA simulation. The dimensioning model based on the direct 2-D FEA identification of the electrical equivalent circuit parameters is validated on a prototype. [ABSTRACT FROM PUBLISHER]

In this paper, a new approach for modeling electromagnetic railguns is proposed. The model’s simplicity makes it suitable for sensitive analysis and optimization procedures. For validation, the railgun is simulated by a 3-D finite-element method (FEM) using Maxwell software and the results are compared with existing experimental data. Circuit model simulation results verified the accuracy of the model as they are very close to the experimental ones. As multistage railgun is one of the greatest improvements in railgun expansions, a successful attempt is made for the new circuit model to include this, as evidenced by comparing the results of multistage railgun model with those of the FEM. [ABSTRACT FROM PUBLISHER]

This paper presents a global method of evaluating nodal eddy currents based on the known nodal potentials, which is a Galerkin finite-element method formed by employing the Schaubert–Wilton–Glisson basis function as a weighting function. As a result, the accuracy of eddy-current evaluation in the railgun computation could be increased using the nodal finite-element method. The new method takes all the nodal potential values into account to obtain the global nodal current density directly by solving the finite-element equation, which could overcome the drawback of the traditional local element postprocessing method. The computational results show that the new method could greatly enhance the computational accuracy of eddy current, relative to the traditional element postprocessing method. This method could not only be used in the eddy-current evaluation of the railgun but also in other gradient field computations based on known nodal potential values. [ABSTRACT FROM PUBLISHER]

Based on the fact that the double-deck rail demonstrates excellent performance in preventing rails melting and gouging during electromagnetic launch tests, theory and simulation research studies were carried out on the lateral vibration of the double-deck rail and contact properties between the armature and the rail in this paper. We deduced the lateral vibration contact equations of the double-deck rail by simplifying the electromagnetic rail launcher as Bernoulli-Euler model based on the elastic foundation. A finite-element code was used to help us model the launch progress. The influence of the double-deck rail scheme has been analyzed. Both the characteristics of the contact surface between the rail and the armature and the displacement of the rail were considered. The results show that the double-deck rail can inhibit the propagation of bending waves and efficiently reduce rail gouging. Besides, the connection method of the two decks has much influence on this effect. [ABSTRACT FROM PUBLISHER]