Powerful Current Pulses Research Articles

Влияние параметров токового воздействия на радиальное рассеивание металлических кумулятивных струй

To reduce penetration effect of a shaped charge, powerful current effect on the shaped charge jet could be introduced. Based on numerical simulation within the framework of a model of the uniformly elongating cylindrical rod, the paper analyzes features of the metal shaped-charge jets stretching, when passing a powerful electric current pulse through them. Main attention is paid to the effect of jet material radial dispersion behind its exit from the interelectrode gap. The role of magnetic energy stored in the jet elements during exposure was clarified in this phenomenon. For the shaped-charge jet middle sections formed by charges with diameter of 50 to 150 mm, distributions along the jet radius of the material density and the material radial velocity were obtained immediately after the current “cutoff”. They indicated that as a result of current exposure, the jet material surface layer could be torn off and dissipated with maintaining continuity of its central part. With an increase in strength of the current passed through the jet, thickness of its destroyed layer acquiring radial velocity directed from the axis and increases. Critical currents corresponding to the jet surface layer breakdown and its complete destruction were determined.

Наблюдения обратного сейсмоэлектрического эффекта II рода при электрозондированиях в районе Центрально-Сахалинского разлома

The results of experiments on electrical sounding of the near-surface layer of the Earth's crust in the fault zone, which have involved a recording of seismoacoustic and seismic noise in the close zone near the source (the primary dipole source), are represented. The experiments were carried out in 2021-2022 in the southern part of the Central Sakhalin fault with the use of the generator of electric pulses developed at IMGG FEB RAS, output electric power being up to 3 kW. The aim was to reveal seismoacoustic signatures of the medium reaction to the soundings with current pulses of 5–13 A. The generator provided significantly higher current in the dipole than its typical characteristics in the case of soundings for electrical exploration by resistance methods, as well as in the case of conventional seismic and electrical exploration. At the same time, the range of current amplitudes was much smaller in comparison with the case of a deep sounding based on application of geophysical MHD generators or other extra high-power electric pulses units. Up to now, the inverse seismoelectric effect has remained practically unexplored at currents in the “intermediate” range of ~10 A and scale lengths of the order of few hundreds of meters. The presence or absence of the medium reaction to electrical soundings was distinguished by the records of molecular-electronic sensors developed by R-sensors LLC: the CME-6111 broadband seismometer and the hydrophone, installed at a distance of about 50 m from one of the poles of the electric dipole source. An increase in the average level of seismoacoustic noise during electrical soundings was revealed, which is essentially a variety of the inverse seismoelectric effect of the second kind (excitation of elastic waves during an electric current run in a two-phase medium). Previously, no similar signature of medium reaction to the current pulses was noted in the close zone adjacent to one of the dipole electrodes. The noise level increase occurs almost without delay after the start of electrical soundings, and this is in accordance with the previously obtained results on the responses of seismic acoustic emission to powerful current pulses, which were used for a deep sounding in the Northern Tien Shan.

Switches of Powerful Nanosecond Current Pulses Based on High-Voltage Units of Shock Ionized Dynistors

Monounit and modular switches of high-power current pulses with an operating voltage of 12 kV, made on the basis of series-connected shock ionized dynistors, are described. The switching processes of these switches are studied. The dependence of switching energy losses on the control pulse power is determined. The possibility of switching nanosecond current pulses with an amplitude of several kiloamperes at a frequency of several hundred hertz is shown.

Model of the object of temperature control by electrostimulating action parameters

Technologies for pressure treatment of metal workpieces using powerful current pulses are becoming increasingly widespread both in Russia and abroad. Unique electromechanical processes are studied and improved in laboratory and production conditions. The process of applying an electric current to the workpiece is accompanied by a change in its physical properties as a result of the so-called electroplastic effect (EPE). At the same time, the temperature of the workpiece in the deformation zone increases. For high-quality and reliable operation of the drawing mill with electrostimulated drawing (ESW), it is necessary to use an automatic system for regulating the force and temperature. In order to implement the temperature control circuit, it is necessary to synthesize the transfer function of the control object – steel wire processed by pressure (rolling or drawing). Synthesis and analysis of parameters of the model of temperature control object are considered. The known relations are used: dependence of the pulse generator power on the calculated parameters (initial temperature, diameter, specific weight and electrical resistance of the workpiece, pulse duration); dependence of the RMS current of the generator on the amplitude and frequency of pulse reproduction; dependence of the magnetic permeability of the workpiece on its temperature; and dependence of the specific electrical resistance of the conductor material on temperature. In MATLAB – Simulink medium, a model of the temperature control object is synthesized as a function of the parameters of generator of high-power current pulses (amplitude and frequency), as well as the parameters of the workpiece to be processed (diameter, sample length, linear velocity, initial temperature, and resistivity at the initial temperature). The model is analyzed, and transients under different operating modes are presented. Using the developed model, the dependences of the temperature, power, and equivalent resistance on parameters of the generator and the workpiece are obtained for different generator pulse frequencies and workpiece diameters. The developed model can be used for laboratory studies of the electroplastic effect, as well as in production in auto-control systems with electrostimulated drawing in order to implement the object of regulation in the form of a model.

Electromechanical installation based on high power current pulse generator

Electromechanical installation containing electromagnetic s noid with a piston operating in reciprocating motion mode has been developed. Technologies with similar operating modes are widely used in various industries (mechanical engineering, metallurgy, mining, mechanics, robotics, as presses for forging and stamping, as well as jack-hammers in crushing devices for coal, ore and rock). An economically effective generator of high power unipolar current pulses (with unique systems that allow adjustment of the main parameters in a wide range and with high speed: the frequency of pulse reproduction, amplitude) was used as a power source for electromechanical installation. The principle of operation of the generator is based on periodic discharge of pre-charged capacitors to a low-resistance active-inductive load. Generator contains power unit, consisting of a capacitor discharge unit for load; a generator control system (GCS), consisting of a capacitor charging unit (reversible thyristor converter with counter-parallel connected thyristor bridges); a recharge unit and an automatic control system of the ACS. According to the known equations, parameters of mechanical and electrical parts of the electromechanical installation were calculated: initial coordinate of the piston; magnetomotive force arising from change in inductance L(x) ; spring force; the force of resistance to the piston, proportional to the speed of its movement; force action on the piston; amplitude, duration and frequency of reproduction of current pulses. A simulation model of the installation has been developed in the MATLAB-SIMULINK environment. The graphs of transient processes during operation of the installation at idle and under load were built. Analysis of the operating modes of the installation was carried out. Developed electromechanical installation for influencing load with the aim of its destruction or deformation with a system of automatic control of parameters makes it possible to regulate process parameters with high speed: force and distance traveled by the piston.

Compact Induction Accelerator of Laser Plasma for Ion Energy up to 1 MeV

The collective acceleration of laser plasma ions in a rapidly increasing magnetic field (108 T/s) excited by a powerful current pulse in a low-inductive conical spiral expanding in the direction of plasma acceleration has been studied. A mathematical model and an algorithm for calculating the radial Br and axial Bz components of the magnetic field in the approximation of a conical spiral by a system of rings of variable radius are proposed to analyze the factors affecting the efficiency of such acceleration. Based on computer modeling and an experimental variation of magnetic-field excitation parameters, the regime of effective ion acceleration is obtained. With the help of time-of-flight collector measurements, the velocities of ions whose atomic mass differs by two orders of magnitude are determined. The maximum velocity of both light ions (lithium) and heavy ions (lead) exceeds 106 m/s, and the corresponding energy for lead ions is ~1 MeV. The efficiency of collective acceleration with the direct acceleration of laser plasma ions in a high-current high-voltage diode with magnetic insulation is compared.

Electromechanical installation based on a powerful current pulse generator for materials treatment

The electromechanical device containing an electromagnetic solenoid with a piston operating in the reciprocating motion mode was developed. Technologies with similar operating modes are widely used in various industries. Economical generator of powerful unipolar current pulses with unique systems is used in the electromechanical device. It allows its main parameters to be regulated in a wide range and with high speed: pulse reproduction frequency and amplitude. The principle of generator operation is based on the periodic discharge of pre-charged capacitors to a low-resistance active-inductive load. The parameters of the mechanical and electrical parts of the electromechanical device are calculated: the initial coordinate of the piston, the magnetomotive force resulting from a change in the inductance L(x), the spring elasticity, the resistance force of the piston proportional to its speed, amplitude, duration and frequency of current pulses. A simulation model of the device in the environment of Matlab-Simulink was developed. Plots of transients during the device idling and under load were constructed. The analysis of the device operating modes was performed. The developed electromechanical installation allows the process parameters to be adjusted.

Transformer Generator of Powerful Current Pulses

A generator design with a pulse energy of more than 1 MJ connected to an external constant voltage source with limited current strength and power is proposed. The power supply of an active-inductive load is calculated numerically and analytically. Generator parameters for pulse-frequency operation are determined. The efficiency of this generator and the validity of the method for calculating its characteristics are confirmed by the results of an experimental study of a small-size transformer generator.

High power current pulse generator based on reversible thyristor converter

In metal forming using high power current pulses, it becomes necessary to control both reproduction frequency and pulse amplitude. Description of a generator of high power current pulses with controlled thyristor converter is provided as a power source of charging device (charger) for regulating voltage (pulse amplitude) of capacitor charge. Faults of the generators associated with inrush current in capacitor charge modes are revealed, which reduces quality of supply network. To reduce time of transient processes while lowering voltage across capacitors, application of reverse thyristor converter is applied as a power source. Structural diagram of generator is considered, which includes reversible thyristor converter with separate control, power unit, capacitor recharge device, charger parameters automatic control system and capacitor charge process control system. Calculation of parameters of automatic control system regulators is presented. To obtain optimal transients, standard methodology for setting regulators to a modular optimum was used. In order to reduce overshoot at time of disturbances appearance, which can reach 100 % and higher, socalled logical device was introduced into the automatic control system. It blocks control pulses on thyristors of converter and simultaneously reduces signal at the output of current regulator to zero. Simulation model of high power current pulse generator in MatLab – Simulink environment was synthesized. Analysis of the model was carried out, and graphs are given that explain principle of device operation and transition processes under various operating modes. Generator application will allow user to adjust amplitude of current pulses with high speed and to obtain sufficiently high-quality transient processes of capacitors charge (discharge), which will have beneficial effect on supply network. Application of better converters will significantly increase frequency of reproduction of current pulses.

Collective Acceleration of Ions in a Pulsed Magnetic Field of a Conical Spiral

The collective acceleration of laser plasma ions in a magnetic field generated by a powerful fast-growing current pulse in a low-inductive conical spiral is studied. The velocity of ions for a number of elements which significantly differ in atomic weight are obtained on the basis of collector measurements. The maximum velocity of both light (lithium) and heavy (lead) ions exceed the value of 108 cm/s; for ions of lead, the corresponding energy amounts to a value of ∼1 MeV. A mathematical model of ion acceleration is proposed and simulation results are compared with the experiment.

An Algorithm for Designing of Cascaded Helical Flux Compression Generator

Cascaded helical flux compression generators (Cascaded-HFCG) are widely used to produce powerful current pulses in many industries, while there is no specific method to design these generators in any books or articles. In this paper, firstly some mechanical and electrical criteria are described, and then an algorithm is proposed based on these criteria. A computer code is written using MATLAB based on the proposed algorithm and some programs are prepared in COMSOL to calculate electrical parameters of the generators which can be used in the design procedure. The validity of the proposed algorithm is verified by simulation.

ИССЛЕДОВАНИЕ РАБОТЫ НИЗКОВОЛЬТНОГО УДАРНОГО ГЕНЕРАТОРА В УСТРОЙСТВЕ ЭЛЕКТРОГИДРАВЛИЧЕСКОГО ВОЗДЕЙСТВИЯ ДЛЯ МАЛОГЛУБИННОЙ СЕЙСМОРАЗВЕДКИ

Актуальность исследования обусловлена необходимостью разработки новых источников мощных импульсов тока для работы на электрогидравлический излучатель с раздвигающимися электродами, который может применяться для возбуждения сейсмических волн в невзрывной сейсморазведке. Цель: провести расчетные и экспериментальные исследования работы низковольтного ударного генератора на дугу в воде, инициированную раздвигающимися электродами в режиме одиночных импульсов и при получении серии импульсов давления. Провести оптимизацию параметров ударного генератора и электрогидравлического излучателя с целью получения максимального импульса давления. Объекты: низковольтный ударный генератор, выполненный в габаритах кранового асинхронного двигателя МТН-612, подключенный к электрогидравлическому излучателю с раздвигающимися электродами. Методы: согласование параметров ударного генератора и дугового разряда методом планирования эксперимента с помощью математической модели. Результаты. Проведены лабораторные исследования работы низковольтного ударного генератора на дугу в воде, инициированную раздвигающимися электродами в режиме одиночных импульсов и при получении серии импульсов. Методом планирования эксперимента получена математическая модель работы ударного генератора на дугу в воде, инициированную раздвигающимися электродами в режиме одиночных импульсов, получены уравнения регрессии для выходных параметров дугового разряда, проведена оптимизация параметров ударного генератора и электрогидравлического излучателя, что позволяет получить максимальный импульс давления для проведения малоглубинной сейсморазведки. Полученный амплитудно-частотный спектр импульса давления показал, что основная энергия импульса давления лежит в среднечастотном диапазоне от 50 до 100 Гц, что обеспечивает высокий сейсмический КПД для проведения малоглубинной сейсморазведки.

INFLUENCE OF PULSED ELECTRIC CURRENT ON THE WAVES MOTION CHARACTER OF PLASTIC DEFORMATION AT TENSION OF A STEEL PLATE

Infrared thermography and two-exposure speckle interferometry have been used to study the plastic deformation of low-carbon steel under the action of pulsed electric current. It was established that external electric effect leads to an increase in velocity of plastic waves by 65 %. Analysis of the velocity distribution patterns showed that they have the profile of “shock transition”. At the origin, velocity of the material is zero (motionless gripping), and at the right end of the curve material velocity is equal to stretching speed specified by testing machine. The effect of electric current leads to splitting of the displacements velocities, both at moving and stationary ends of the samples. It is assumed that the observed splitting is related to the Stark splitting of energy levels of the deformed system. This splitting leads to a decrease in the potential barrier for the motion of defects in crystal lattice. Thermographic studies have shown presence of a temperature gradient directed from clamps to center of the sample, which does not coincide with pattern of displacement distribution. It was determined that during the primary treatment with high power current pulses in the central area of the sample, sample temperature reaches 351 K, and 330 K in the area adjacent to clamps. Subsequent treatments result in a slight increase in temperature. This behavior of temperature can be explained by the fact that heat does not dissipate at a repetition rate of 10 Hz. On an average, sample temperature increases by 30 K. Theoretical calculation has shown that the Joule effect leads to an increase in temperature of the sample by 21 K per pulse, which is practically in agreement with experimental results. Estimates of thermal energy and energy of elastic deformation have shown that the fastest channel for converting the energy of electric pulse is structural changes in deformable system, which lead to the observed decrease in deforming force.

MELT DROPS MOVEMENT OVER SEMICONDUCTOR SURFACES CONTROLLED BY ELECTRIC FIELD

The problems of molten zones formation and their subsequent migration over material surface are of interest from the viewpoint of developing novel technological methods of forming microelectronic structures. Such drops can be used as primary working elements of microlenses and reflectors, displays, weighers. The aim of this work was experimental studying processes of electromigration of molten silver- and aluminum-based inclusions over surfaces of germanium and aluminum semiconductor crystals. The issues of formation and motion of molten drops over the surfaces of silicon and germanium semiconductor crystals are considered within the framework of the electrocapillary approach. It is shown by an example of Ge-Ag and Si-Al systems that accelerated migration is related to the contribution of an electrocapillary component that relates surface tension force of melt drops to electric potential difference at the interface. The experiment consisted in applying metal grain to the surface of the samples and vacuuming the chamber where excessive pressure and the surface temperature were created. Migration of inclusions by powerful current pulses was initiated. An analysis of the effect of direct current on a drop of melt deposited on the surface of a crystalline matrix was made. An analysis of the droplet composition was carried out using the AES method, the results of which showed the relationship between silver and germanium concentrations. Quantitative evaluations are given for migration rates in systems under direct current flow as well as under pulsed current loads. During the experiment, it was found that the energy required to detach the droplet from the rigid matrix was not consumed. The value of the surface charge transfer density was estimated. The results of the work can be used to develop new technological methods for the formation of microelectronic structures and their use for practical purposes.

Influence of Pulsed Electric Current on the Motion of Spontaneous Plastic-Deformation Waves in Steel-Plate Extension

Despite growing interest in the intensification of shape changes by means of current pulses, very limited experimental and theoretical information regarding plastic deformation is available, and the physics of plasticization in metals has not been adequately studied. That is delaying the application of promising techniques in practice. In studying electrically stimulated plastic deformation, it may be useful to regard plastic flow as a wave process. By infrared thermography and double-exposure speckle interferometry, the plastic deformation of low-carbon steel in the presence of pulsed electrical current is studied in the present work. Such treatment increases the velocity of the plasticity waves by 65%. Analysis shows that the velocity distribution corresponds to a impact-transition wave. At first, the velocity of the material is zero (motionless clamp), but on the right side of the graph the velocity of the material is equal to the extension rate specified by the test machine. When current pulses are applied, the distribution of displacement velocities is split at both the mobile and immobile ends of the sample. Thermal data show that a temperature gradient runs from the clamps to the center of the sample. That does not match the distribution of the displacement. In the initial treatment by powerful current pulses, the sample temperature reaches 351 K in the central region of the sample and 330 K at the clamps. In other words, the difference is 21 K. Subsequent treatment increases the temperature only slightly. According to literature data, such increase in temperature decreases the yield point by 10% for the given steel. That corresponds to the results of the present experiments. The present work confirms previous findings regarding the change in velocity of the slow wave on current transmission. The splitting of the velocity values at the mobile clamp has not previously been reported.

Study of plasma dynamics in a pulsed hollow cathode magnetron

Study of the hollow cathode magnetron (HCM) discharge, which is supplied by a source of powerful current pulses, was carried out. By means of probe and spectral measurements, the dynamics of a pulsed discharge was studied. The results show that a high density plasma (ne > 1012 cm-3) is generated at a distance of 20 cm from the HCM. Based on the data obtained, a mechanism for the formation and development of a discharge was proposed.

Physics-of-Failure (PoF) methodology for qualification and lifetime assessment of supercapacitors for industrial applications

Supercapacitors are used nowadays in an extensive range of battery-powered devices such as GPS/GPRS transceivers, active RFID tags, industrial PDAs, electronic locks, micro medical pumps, digital cameras, mobile phones and others. They are also used in vehicle's and machine's sub-systems requiring short but robust powerful current pulses. This covers back-up, delivery and leveling of high peak power as well as storing harvested energy.They are designed to meet high power requirements that cannot be fulfilled by standard batteries. Furthermore, their size and cost are very attractive for industries.However, selecting the right supercapacitor for a specific application remains a real challenge to industry. The specifications of these components only provide limited information about their lifetime for specific stress values. This information is not enough for industries to design a robust product and avoid high field returns.In this paper, we apply the Physics-of-Failure (PoF) methodology for qualification and lifetime assessment of electronic systems, to derive PoF models for supercapacitors at different stresses relevant for some industrial applications. It is expected from these models to better understand the performance of supercapacitors at different stresses and to predict accurate lifetime of supercapacitors allowing industry to robustly design their products and avoid high field returns.

Automatic Control of Electrostimulated Drawing

A system for regulating the parameters of electrostimulated drawing (the temperature in the deformation zone and the drawing force) is considered. This system produces a control signal for the unit generating powerful current pulses. The basic operating principle is periodic discharge of a precharged capacitor to a low-resistance load. For regulation of the pulse amplitude and increase in system power, the uncontrollable dc source in the charger is replaced by two irreversible thyristor converters, which are in series and operate in the same direction. That produces a controllable voltage at the power capacitors. To optimize capacitor charging, a two-loop subordinate control system is employed: the external loop regulates the voltage, while the internal loop regulates the current that charges the capacitors. The high speed of the transient processes in electrostimulated drawing—in particular, the rapid temperature rise in the deformation zone on account of the large current pulse (up to 10 kA) and the high pulse frequency (up to 400 Hz)—means that manual control is practically impossible. To boost the reliability and quality of electrostimulated drawing using a powerful current-pulse generator, an automatic control system for electrostimulated drawing is developed. It includes a single-loop system for regulating the drawing force and also delayed temperature feedback in the deformation zone. The dependence of the drawing force and temperature on the frequency of the current pulses is established by means of laboratory research and calculations using both new and familiar methods. A model of the proposed control system in MATLAB-Simulink software permits analysis of the operating conditions in electrostimulated drawing under automated control. The model is consistent with the actual parameters obtained in research on the electroplastic effect. The proposed model permits improvement in the characteristics and operating conditions of electrostimulated drawing. The formalized structure of the system, the proposed model of the system in MATLAB-Simulink software, and the oscillograms of the transient processes are considered. The single-loop automatic control system for the drawing force, with flexible temperature feedback in the deformation zone, permits optimization of the operating conditions and improvement in the reliability of electrostimulated drawing. The proposed system is recommended for use in studying electrostimulated deformation and also for the control of wire drawing in production conditions

POWERFUL SOURCES OF PULSE HIGH-FREQUENCY ELECTROMECHANICAL TRANSDUCERS FOR MEASUREMENT, TESTING AND DIAGNOSTICS

Aim. Development of powerful current radio pulses generators (CRPG) for powering high-frequency electromechanical transducers based on IGBT transistors. Methodology. To carry out the research, the statements of the magnetic and electromagnetic fields interaction with electric and ferromagnetic material, electric circuits, structure of radio electronic devices theory were used. Results. The main provisions for creating powerful broadband generators for powering electromechanical transducers based on IGBT transistors are determined. It is shown that the generators intended for use in measurements, testing and diagnostics should provide adjustment of the frequency and duration of the output current pulses, and also provide current in the transducer inductor of several hundred amperes. The connection between the power frequency of the resonant electromechanical transducer and the gap between the transducer and the surface of the metal being diagnosed is established. A CRPG variant for powering electromechanical transducers in the frequency range 1 ... 3 MHz and the duration of current pulses of 1 ... 20 periods of the filling frequency is developed and manufactured. The peak current in the inductor of a high-frequency electromechanical transducer has reached 450 A. Novelty. For the first time, the possibility of using powerful IGBT transistors in electronic devices working in a key mode in push-pull circuits for feeding high-frequency electromechanical transducers is shown. Practical value. Using the results obtained will allow the creation of new instruments for measurement, control and diagnostics with wider characteristics.

Electrostimulated machining of metals

New mechanical equipment requires structural materials whose high performance cannot be ensured by traditional methods. A promising approach to the shaping of steel is the use of powerful unipolar current pulses with the following characteristics: amplitude 10–15 kA; pulse frequency up to 400 Hz; pulse length up to 100 μs. The widespread industrial use of this technique is hindered by the low efficiency of the corresponding pulse generators, which also draw considerable power from the ac grid and are not sufficiently controllable. In the present work, a generator of powerful unipolar current pulses that is free of those defects is described. It includes a charging system connected to power capacitors; and a thyristor switch that discharges the capacitors to a low-resistance load. To reduce the power drawn from the grid, the generator includes a recharging device based on a thyristor, which is connected to a reverse-parallel thyristor switch. To permit regulation of the pulse amplitude and increase its power, the uncontrollable dc source in the charging system is replaced by two irreversible thyristor converters in series. That permits control of the voltage at the power capacitors. To optimize capacitor charging, a two-loop subordinate control system regulates the parameters of the pulse generator: the external control loop governs the voltage charging the capacitors, while the internal control loop governs the charging current. MATLAB Simulink software is used to create a model of the proposed generator. The model corresponds to the actual pulse generator used at Siberian State Industrial University to investigate the electrostimulated plastic deformation of metals and alloys. The model permits improvement in the characteristics of the pulse generator and its operating conditions. A benefit of the proposed generator over its counterparts is that the power drawn from the grid is considerably reduced, while the voltage charging the capacitor may be regulated in the range up to 600 V, with pulse frequencies up to 400 Hz. The generator may be used industrially—in particular, in rolling mills when drawing steel wire that is hard to deform.