Current Pulse Generator Research Articles

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.

A repetitive high current pulse generator for high flux electrothermal plasma jets.

Power sources play an important role in the characteristics and the applications of the electrothermal (ET) plasma as an edge localized mode (ELM) heat flux simulator. A repetitive high current ET plasma source with the capability of working at a 10 Hz repetition rate and peak current 7.5 kA is presented in this paper. By controlling the sequence of discharge of ten pulse power modules, a repetitive high heat flux plasma jet can be generated. A two-stage capillary structure is presented, and its repetitive trigger driving circuit based on surface flashover ignition is designed to achieve reliable and repetitive discharge. The topology of the inductive and capacitive (LC) series resonant circuit is applied to the charging system of the pulsed power source. The charging current is limited to 500 A with a charging time of 3.5 ms, and the ratio of the charging voltage to the operating voltage is 1.85. A diode and a power resistor in series are used to suppress the negative overvoltage, which is helpful to increase the thyristors' operating reliability. Using the designed repetitive ET plasma source, the characteristics of the ET plasma jet are investigated by measuring the voltages and currents and by obtaining images of the discharges. Experimental results show that the repetitive ET plasma generator can be used as an appropriate way to simulate the ELM-like heat flux plasma.

Application of Inductive Sensors in the Study of Fast Processes

Launching and control of pyrotechnical systems at a specified coordinate is among the most complicated problems in the tests at a missile track. A method for launching and a corresponding device are proposed for activation of pyrothechnical systems of missile trains boosting along an ejection path to hypersonic velocities with ejection of an object to free flight. The method is based on generation of current pulses for activation of pyrotechnical systems of the moving stages of a missile train using inductive sensors. The principle can also be used for implementation of a noncontact method for activation of recording systems and a device for measurement of the mean velocity of an ejected object in continuous media. The method is based on the generation of starting signals (positive rectangular pulses) for activation of recording equipment with matching relative to the specified coordinate and measurement of the velocity of the ejected object at the moment when it passes through the measurement cross section. Methods for activation of recording systems and results of hydrodynamic and terradynamic experiments are presented.

Detection of femtosecond spin injection into a thin gold layer by time and spin resolved photoemission

The ultrafast demagnetization effect allows for the generation of femtosecond spin current pulses, which is expected to extend the fields of spin transport and spintronics to the femtosecond time domain. Thus far, directly observing the spin polarization induced by spin injection on the femtosecond time scale has not been possible. Herein, we present time- and spin-resolved photoemission results of spin injection from a laser-excited ferromagnet into a thin gold layer. The injected spin polarization is aligned along the magnetization direction of the underlying ferromagnet. Its decay time depends on the thickness of the gold layer, indicating that transport as well as storage of spins are relevant. This capacitive aspect of spin transport may limit the speed of future spintronic devices.

Performance Degradation of Automotive Power MOSFETs Under Repetitive Avalanche Breakdown Test

Avalanche ruggedness is one of the key factors for safe and reliable power converters deployed in various automotive subsystems. In this article, the avalanche capability of power MOSFETs is tested under different repetitive avalanche conditions to differentiate the die degradation and package degradation. While examining the degradation mechanisms, the corresponding electrical parameter shifts are analyzed to better understand the structural changes and root causes and identify potential precursors for condition monitoring. For this purpose, a high-resolution and cost-effective nanosecond current pulse generator (CPG) is designed. Due to the high-resolution pulsewidth modulation function of a digital signal processor (DSP), short current pulses can be generated in the order of 100 ps where the magnitude and duration of the current pulsewidth can be adjusted precisely. During the experiments, power MOSFETs are stressed under two different pulsewidths. It is observed that the ON-state resistance gradually increases in both cases, yet the roots of the degradations are different. The die degradation and package degradation are responsible for the changes in short pulse and long pulse, respectively. In the short pulse case, some devices show saturation in drain leakage current and ON-state resistance, while some others show a significant threshold voltage drop, which leads to a noticeable shift of transfer and output characteristics. The electrical parameter shifts indicate a possible gate degradation after the device aging. At the end of the tests, failure analyses are conducted on both devices under test (DUTs) under different stress conditions, revealing different failure mechanisms.

Pulse current generator with improved waveform fidelity for high-voltage capacitively coupled plasma systems

This paper proposes a current source-type pulse generator circuit to improve load voltage waveforms by solving the voltage ringing problem of capacitively coupled plasma systems. The voltage source-type pulse power supplies used in the plasma industry have short-circuit currents and voltage ringing problems with capacitively coupled plasma loads. The current source-type pulse generator proposed in this paper can solve these problems. The proposed circuit consists of four detailed circuits: bias current generator, bias current modulator, slope current generator, and slope current modulator. They form two constant currents at the DC link, and output two pulse currents to the load. These output currents contribute to generating the plasma load voltage required by the capacitively coupled plasma process. The proposed circuit is verified by a PLECS simulator and a laboratory-scale hardware system. To check the improvement of the output waveform, a voltage source-type pulse generator and the current source-type pulse generator are tested under the same experimental conditions. The results are represented by load voltage and current waveforms. In addition, the entire system of the current source-type pulse generator is designed and verified by simulation and experimental results. The resulting output waveforms meet the process requirements, and the obtained results demonstrate that the proposed current source-type pulse generator circuit can be suitably used for capacitively coupled plasma loads.

Effect of the prepulse current with an adjustable time-delay on the implosion dynamics of two-wire Z-pinch

Experiments are performed on the ‘Qin-1’ double pulse current generator at Xi’an Jiaotong University to study the effect of the prepulse current on the implosion dynamics of two-wire Z-pinches. An independent prepulse current with an adjustable time-delay (Tdelay) is introduced to preheat the wires before the start of the main pulse current. An estimation of the deposited energy and the areal density reconstructed from the interferogram suggest that the wires are partly vaporized with a gasification fraction of ∼67%. The prepulse preconditioning has a redistribution effect on the load mass, which determines the subsequent implosion process. The planar implosion of the two-wire load with a preset Tdelay ⩽ 450 ns can be divided into the two-layer phase and the merged implosion phase. The snowplow-like implosion is the main characteristic of the shot with a 1050 ns Tdelay. The ablation streams gradually disappear with the increasing Tdelay. The proportion of the mass that participates in implosion is increased as the preset Tdelay increases from 120 ns to 1050 ns.

Botulinum Toxin Type A Therapy: Intravesical Injection or Electromotive Drug Administration

To compare the outcomes of intravesical injection of botulinum toxin A (BoNTA) with intravesical electromotive drug administration (EMDA) of BoNTA on urinary incontinence secondary to neuropathic detrusor overactivity (NDO) in children with myelomeningocele (MMC). A total of 26 children with MMC (11 boys, 15 girls) who had urinary incontinence secondary to NDO were retrospectively enrolled in the study. Patients in EMDA group (n = 14), using an electrode-catheter, 10 IU/kg of BoNTA were inserted into the bladder for EMDA without anesthesia and on an outpatient basis. The EMDA equipment was connected to the electrode of indwelling catheter and 2 dispersive electrodes, a pulsed current generator delivered 10-20 mA for 20 minutes. Patients in injection group (n = 12) were received interavesical injection of 10 IU/kg of BoNTA via rigid cystoscope on an inpatient basis. All patients had been evaluated by a voiding diary, urodynamic study, renal, and bladder ultrasounds before, 6 months and 1 year after the treatment. Six months after the treatment, 12 of 14 (85.7 %) and 8 of 12 (66.6%) patients in EMDA and injection groups respectively became completely dry between 2 consecutive clean intermittent catheterizations, which maintained in 11 of 14 (78.5%) of patients in EMDA group compared to 6 of 12 (50%) of patients in injection group, 1 year after the treatment. Patients in both groups improved after the treatment; however improvement in EMDA group was more prominent with better sustained effects. BoNTA/EMDA is a feasible, reproducible, cost benefit, and pain free method as an outpatient basis and no need for anesthesia.

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.

An Improved Repetitive Inductive Pulsed Power Supply Circuit With ICCOS Technique

With the development of semiconductor switches in recent years, inductive energy storage has shown a good application potential in pulsed-power supplies. In our previous studies, a repetitive inductive pulsed-power supply (IPPS) circuit topology was proposed to generate continuous current pulses. An insulated-gate bipolar transistor (IGBT) is used as the main switch to cut off the charging current in this topology. Limited by the current turning off ability of the main switch, it may encounter difficulties in expanding to higher charging currents. In this article, with the concept of inverse current commutation with semiconductor devices (ICCOS) switch, which is proposed by the German-French Institute of Saint Louis (ISL), an improved repetitive IPPS circuit topology is proposed by using a bridge current commutation unit as ICCOS. The thyristor acts as the main switch in the improved circuit and the charging current is turned off by a precharged capacitor. To turn off the charging current for the next cycle, the capacitor can be self-charged by the leakage flux of the pulse transformer and the back electromotive force from the load. Other than that, when the load current pulse reaches the required width, the residual energy of the system can be recovered by switching the inductor to the charging state. Simulation and comparative study show that the improved circuit is suitable for the generation of repetitive current pulses in high-energy systems.

The use of electrohydropulse treatment of waste solutions in refining production for the recovery of platinum group metals

The high cost of precious metals and environmental requirements lead to the need for the completeness of their extraction from primary and secondary raw materials.During the processing of primary raw materials, waste solutions are produced that contain low-concentration precious metals, which must be removed from the process. To prevent losses and comply with environmental protection requirements, it is necessary to extract precious metals from waste solutions. The complexity of this task lies in the low concentration and chemical forms of the presence of precious metals in aqueous systems. The cementation method, currently used for the extraction of precious metals, has several disadvantages: the duration of the process, high-energy consumption, etc. To increase the efficiency of the method used, it is necessary to pre-treat the solution with the goal of labilizing the noble metal complexes. The purpose of the experiment: determination of the optimal modes of the electrohydropulse (EHP) method for intensifying the process of additional extraction of platinum group metals (PGM) and heavy non-ferrous metals from industrial solutions of refining production. As a result of the study, the necessary materials were selected to create the reactor and electrode systems, the volume of the laboratory reactor was determined. Trial launches of the installation were carried out, according to the results of which a pulse current generator (PCG) was configured. A series of tests was carried out, based on the results of which conclusions were drawn about the possibility of using this method to activate stock solutions.

GLIDER-A pulsed-current generator for laboratory astrophysics x-ray absorption experiments.

In the field of pulse-power, there has always been an interest on small and medium size pulsed-current generators (≤2 MA) which are affordable and of low maintenance. We developed the GLIDER, a compact and modular generator, that drives a gas-puff z-pinch load as a soft x-ray source (0.1-1 keV) for laboratory astrophysics absorption experiments. It comprises 48 bricks, tightly packed in a 1.7 m × 3.5 m × 0.8 m transformer oil container. Its compactness and reliability was enabled owing to unique multilayered oil-soaked insulators, and more than 100 post-hole convolutes. Its stripline includes interchangeable tiles for ease of construction and maintenance. Six triggering units enable current pulse shaping. The GLIDER was tested up to ±60 kV (34 kJ) and produced 2 MA in 450 ns rise time on a 5 nH load. We present grating spectra of K-shell absorption of neutral O and N proving the experimental concept and demonstrating column density and ionization measurements.

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.

A New Modular XRAM-Like Inductive High- Current Pulse Generator Circuit Topology

XRAM (MARX spelt back words) is currently a very important circuit for high current pulse generators. In our previous studies, an XRAM-like circuit was proposed based on multiple pulse transformer modules and a capacitor connected in parallel. Compared with the traditional XRAM circuit, the same number of inductive energy storage modules can be used to generate higher current pulses. This circuit is also capable to recover the residual energy and generate repetitive high-current pulses. However, this circuit topology requires more power electronic switches (three IGBT switches per pulse transformer module). In order to reduce the number of switches, by adding two IGBT switches in the capacitor module, a new modular XRAM-like circuit with reduced switches (one IGBT switch per pulse transformer module) is proposed in this paper. The change of the circuit topology makes the capacitor discharge the primary inductors of the pulse transformer in series during the residual energy recovery stage, instead of the parallel discharge in the previous circuit. This requires the closing time of the IGBT switch in each pulse transformer module ahead of the discharge start time of the capacitor. Working process of the proposed circuit was described in detail and simulations of a 12-module circuit were carried out to verify the circuit operation. Finally, the preliminary experimental results of a two-module laboratory prototype are presented. The results confirm the theoretical analysis and show the validity of the converter scheme.

Algorithm for Calculating the Parameters of a Combined Electric-Discharge Energy Source in High-Voltage Electrochemical Explosion in a Confined Volume

In this paper, using experimental data, we develop an algorithm for calculating the parameters of combined electric-discharge energy sources in a high-voltage electrochemical explosion (HVECE) (pulse current generator parameters, discharge gap length, and exothermic composition mass). These parameters provide the energy characteristics specified by the technology of an HVECE in a confined volume. To eliminate the multivariance of the solutions when the proposed algorithm is used, we recommend using the amount of released chemical energy per unit of electrical energy introduced into the HVECE channel as an optimization criterion.

High peak optical power of 1ns pulse duration from laser diodes - low voltage thyristor vertical stack.

It is shown that the use of low-voltage GaAs/AlGaAs thyristors as high-speed and high-current switches in vertical stacks with semiconductor lasers ensures the efficient generation of high-power ns-duration laser pulses. The lasing and current dynamics in vertical stacks based on laser diode mini bar emitting at 1060 nm and a single as well as a double thyristor switch is studied. The possibility is demonstrated that a laser diode mini bar (with 3 laser emitters) together with a single thyristor switch can generate laser pulses with a peak power of 6 W with a duration of 950 ps and a peak current of 12 A for an operating voltage of 28 V. The use of a double thyristor switch leads to a broadening of the current pulse due to different delays in turn-on of the thyristor switches, while the peak power and duration of laser pulses increase to 8 W and 1.4 ns, respectively. It is found that the stage of low-speed turn-on of the thyristor limits the efficient generation of current and laser pulses of ns duration at low operating voltages (less than 21V). An efficient generation of current and laser pulses by low-voltage thyristors at control currents of 2-320 mA is ensured by efficient impact ionization in the region of the reverse biased p-n junction at high values of operating voltages (more than 21V).

Electrical parameters with His-bundle pacing: Considerations for automated programming

Programming of His-bundle pacing may be challenging because current implantable pulse generators are not specifically designed for this pacing modality. The purpose of this study was to evaluate electrical parameters in order to propose preset programming options with different configurations. Data were collected from 50 patients with His pacing leads connected to various ports (atrial, right ventricular, or left ventricular) of pacemakers and defibrillators during a detailed device interrogation, which included capture thresholds with various pacing vectors, measurement of timing intervals, and performance of automatic threshold algorithms. His-bundle pacing thresholds were significantly lower during unipolar pacing compared to bipolar and extended bipolar polarities. However, current drain was offset due to lower impedance. The His pace-right ventricular sensed intervals were measured at 40-150 ms (mean 85 ± 25 ms), with the longest delays in patients with uncorrected right bundle branch block and selective His capture. This has implications for ventricular safety pacing windows (which were inactivated without evidence of crosstalk) and delays to minimize unnecessary ventricular backup pacing (which was also affected by refractory periods). The measured intervals also impacted the performance of automatic threshold algorithms, which performed differently depending on which port the His lead was connected to and did not distinguish between His and myocardial capture. Our report provides data that could serve to configure automated programming settings to simplify management of His-bundle pacing.

Improvement of processing quality based on VHF resonant micro-EDM pulse generator

As an important non-traditional machining technology, micro-electrical discharge machining (micro-EDM) has become one of the ideal methods for conducting material parts in the mesoscopic scale. However, the current micro-EDM pulse generator has low discharge frequency and wide pulse width, and its nano-scale high-efficiency erosion ability is still difficult to meet the increasing practical requirement. For this purpose, a micro-energy pulse source with narrow pulse width and high-voltage amplitude, which is different from the current typical micro-energy pulse generator, is designed for a pulse generator with more fine-etching ability. Using the principle of circuit resonance, the very high-frequency (VHF) resonant discharge pulse generator can produce an open-circuit voltage waveform with a discharge frequency of 90 MHz and a peak value of 70 V. The single-pulse discharge energy can be continuously processed as low as 6nJ. Based on the VHF pulse generator and the transistor-type pulse generator, the discharge erosion experiments are carried out, and the surface roughness and recast layer are analyzed and compared. The experimental results show that the former processing quality is obviously better than the latter. The surface roughness after processing at a discharge frequency of 90 MHz can reach Ra 42 nm, the average diameter of craters is 0.38 μm, and the hole edge processed at a discharge frequency of 55 MHz has almost no recast layer which achieves similar cold processing effects.

Atmospheric pressure high-power impulse plasma source for deposition of metallic coatings

Abstract

ИССЛЕДОВАНИЕ И РАЗРАБОТКА УСТАНОВКИ ДЛЯ ПРЕДПОСАДОЧНОЙ ОБРАБОТКИ КЛУБНЕЙ КАРТОФЕЛЯ ВОЗДЕЙСТВИЕМ ЭЛЕКТРОФИЗИЧЕСКИХ ФАКТОРОВ

The purpose of processing potato tubers before planting by the complex effect of electrophysical factors is disinfection from a number of pests, activating the cells of potato tubers to accelerate and increase their germination, with the exception of side effects on the physico-chemical composition of the grown potatoes. The installation contains a toroidal cavity, inside the torus there is a conveyor, an unloading stopper and moving fluoroplastic scrapers. In the condenser space are electro-discharge lamps, connected to sources of a kHz frequency and a rotating disk, with a distributor. On the surface of the torus mounted magnetrons. An induction heater is installed under the torus. The torus has windows for unloading potato tuber waste. The developed installation contains various sources of electromagnetic radiation: microwave generators, which provide endogenous heating of potato tubers and prevent diseases and pests; induction heater to kill beetles and other pests due to thermal burns; high-frequency (110 kHz) alternating pulsed current generators with high voltage and electro-gas-discharge lamps, which accelerate biochemical reactions, saturate tubers with oxygen, increase the elasticity of the tuber peel and its permeability. This whole complex of energy sources contributes to the activation of potato tuber cells, accelerating and improving germination. Using a single unit with a capacity of up to 300 kg/h, it is possible to carry out preplant processing of up to 20 tons of potato tubers no larger than 6 cm in size, with specific energy expenditures of up to 0.2 kW h/kg.