Constant Voltage Power Supply Research Articles

Experimental research on single-pulse discharge crater morphology in SEAM

ABSTRACT The analysis of craters in electrical discharge machining (EDM) can help improve the understanding of the basic theory and predict the process indexes; thus, the research on craters has been a popular topic in this field. However, a novel low-voltage, high-current EDM technique based on a constant-voltage power supply, namely short electric arc machining (SEAM), is almost completely unexplored. To fill this gap and reveal the basic theory of SEAM, in this work, the influences of the voltage and pulse duration under different polarities on the crater diameter, the width, depth, and thickness of the recast layer, and the bulge height are investigated by single-factor experiments using single-pulse discharge, and the differences between the surfaces and cross-sections of craters are further analyzed. The experimental results demonstrate that as the voltage and pulse duration increase, the discharge channel expands, the energy density of the discharge channel increases, and the crater diameter, the width and depth of the recast layer, and the bulge height all increase. It is also found that negative-polarity machining tends to form large and shallow craters with lower surface roughness, while positive-polarity machining tends to form small and deep craters with higher machining efficiency.

Solid state radio-measuring optical-frequency transducer of gas flow rate

The paper presents a study of a solid state radio-measuring optical-frequency transducer of gas consumption based on a transistor structure with a negative differential resistance. A mathematical model of a solid state radio-measuring optical-frequency flowmeter was developed, which made it possible to obtain the conversion function and the sensitivity equation. The solid state radio-measuring optical-frequency gas flowmeter is based on a transistor structure with a negative differential resistance, consisting of a HEMT field-effect transistor and a bipolar transistor with a passive inductive element. When replacing the passive inductance with an active inductive element, the transducer can be completely integrated. The negative differential resistance formed by the parallel connection of the impedance with the capacitive component on the collector-drain electrodes of the transistor structure and inductance leads to the occurrence of electrical oscillations in the oscillator circuit. Theoretical and experimental studies have shown that with an increase in gas consumption from 0 l/h to 4 l/h, the generation frequency decreases from 812.65 MHz to 811.62 MHz at a supply voltage of 3.3 V, and at a supply voltage of 3.8 V from 813.00 MHz to 811.80 MHz. It is shown that by choosing a constant voltage power supply mode, it is possible to obtain an almost linear dependence of the generation frequency on the gas flow rate and choose channels for transmitting measurement information. The obtained theoretical and experimental studies are in good agreement, the relative error does not exceed 2.5 %.

Direct Current Electric Stimulation Alters the Frequency and the Distribution of Mitotic Cells in Planarians.

Background: The use of direct current electric stimulation (DCS) is an effective strategy to treat disease and enhance body functionality. Thus, treatment with DCS is an attractive biomedical alternative, but the molecular underpinnings remain mostly unknown. The lack of experimental models to dissect the effects of DCS from molecular to organismal levels is an important caveat. Here, we introduce the planarian flatworm Schmidtea mediterranea as a tractable organism for in vivo studies of DCS. We developed an experimental method that facilitates the application of direct current electrical stimulation to the whole planarian body (pDCS). Materials and Methods: Planarian immobilization was achieved by combining treatment with anesthesia, agar embedding, and low temperature via a dedicated thermoelectric cooling unit. Electric currents for pDCS were delivered using pulled glass microelectrodes. The electric potential was supplied through a constant voltage power supply. pDCS was administered up to six hours, and behavioral and molecular effects were measured by using video recordings, immunohistochemistry, and gene expression analysis. Results: The behavioral immobilization effects are reversible, and pDCS resulted in a redistribution of mitotic cells along the mediolateral axis of the planarian body. The pDCS effects were dependent on the polarity of the electric field, which led to either increase in reductions in mitotic densities associated with the time of pDCS. The changes in mitotic cells were consistent with apparent redistribution in gene expression of the stem cell marker smedwi-1. Conclusion: The immobilization technique presented in this work facilitates studies aimed at dissecting the effects of exogenous electric stimulation in the adult body. Treatment with DCS can be administered for varying times, and the consequences evaluated at different levels, including animal behavior, cellular and transcriptional changes. Indeed, treatment with pDCS can alter cellular and transcriptional parameters depending on the polarity of the electric field and duration of the exposure.

Энергосберегающая методика изучения физической модели высоковольтного инвертора на основе электронно-лучевого клапана

The schemes of inverters applied in static reactive power compensators (SRPC) are as a rule developed with the use of power semiconductor devices (PSD); however, attempts to develop industry-grade prototypes of high-voltage inverters on the basis of serially produced vacuum-tube devices (VTD) are also made. High-voltage electron beam valves (EBV), which feature—owing to beam recovery at the anode — the minimum possible voltage drop across the anode-cathode section in the conductive state among the VTDs and a high steepness of the impulse front and trailing edges in comparison with PSDs, seem to be promising for such applications. An EBV was simulated in the EWB circuit engineering computer program environment to determine the minimum permissible load resistance at which the EBV has the maximum electrical efficiency up to 0.99. To determine whether it is advisable to construct such inverters, it is necessary to conduct not only theoretical, but also experimental investigations on physical models using dedicated test benches. A high-voltage energy-saving bench for testing EBVs operating within the SRPC circuit in an inverter mode has been developed. The bench takes power supply from the 3x380 V, 50 Hz network. The bench comprises a three-phase high-voltage transformer, using which the power supply voltage can be increased to a 40 kV level. This voltage is rectified according to the Larionov bridge scheme, and, owing to an artificial midpoint, the 0 to +20 kV and 0 to -20 kV voltages with the maximum current up to 1 A are obtained. The voltage amplitude can be smoothly varied using a three-phase electromechanical regulator installed in the high-voltage transformer primary winding. A 50 Hz sine-wave voltage is produced in the inverter mode by means of pulse-width modulation (PWM) with a clock frequency smoothly variable in the 1...3 kHz range and is applied to a water equivalent of load. To increase the bench power level during the test and achieve energy saving, a gating logic device (GLD) was introduced, which allows the EBV control system to operate in an intermittent PWM generation mode. The GLD produces pulses using which three cycles of a 50 Hz sine-wave voltage (with the total duration equal to 60 ms) repeating at approximately 1.2 s intervals are generated. The use of the GLD producing packs of control pulses makes it possible to study the EBV operation modes on the bench at a short-term power of up to 200 kW in pulse-periodic mode, which is significantly (by 10.20 times) higher than the average power of the bench constant-voltage network power supply source. The GLD output voltage waveforms and the load voltage and current front and trailing edge waveforms are given.

Diffuse arc discharge with a hot cathode in a magnetic field as a plasma source of lead and silver mixture for the problem of spent nuclear fuel reprocessing

Conversion of a solid substance mixture into a low-energy (≈ 10 eV) plasma stream with stable parameters is a one of the important tasks for the developing nowadays method of plasma separation. The study of plasma stream characteristics of Pb and Ag mixture was carried out. The evaporation of the substances was realized using induction crucible heating. The discharge was initiated by an electron beam. A variation of the thermionic cathode (LaB6) temperature and the crucible heater power allowed us to control the parameters of the discharge. It was shown, that maintaining a constant potential difference in the cathode-anode gap, in spite of the substantial difference in the saturated vapor pressure of model substances, is possible due to control of the thermionic current from the cathode and constant voltage power supply parameters. Measurements of the spectral composition of plasma radiation made it possible to determine the discharge burning regimes in which ions of multiplicity 2 were absent. The obtained results indicate a possibility of using this type of discharge for testing the method of plasma separation of spent nuclear fuel.

Strategies for Inverter Dual-output Shore-to-ship Seamless Power Supply

This paper simulates the micro-grid to establish a shore-to-ship seamless connection power supply system and control strategy by the shore-controlled inerter dual-output. The shore-controlled 60Hz inverter power supply and the 50Hz inverter transition transformer are directly supplied without changing the control of the ship power station. The shore-ship power supply is seamlessly connected through the shore-controlled inverter, which is suitable for most ships. The strategies for inverter dual-output shore-to-ship seamless power supply are: V/f control method controls inverter constant frequency constant voltage power supply; P/Q control method controls shore ship seamless connection and smooth transfer load; Phase-locked loop control method controls phase-shifting and variable-frequency control of the shore power during the integration of shore power into the ship's power to complete the parallel condition, assisting to stabilize the frequency and voltage of the output of the rectifier inverter; Inverter control reduces frequency and voltage fluctuations of V/f control and P/Q control conversion by following from state following to reverse state following innovation.

Influence of heating mode on life reliability of a hollow cathode heater

The electric propulsion hollow cathode is a thermal electron emission device that can be used as an electron source and a neutralizer for aerospace electric propulsion systems. As a serial structure, the cathode's life reliability is the key to its application in orbit. The heater is used to start the hollow cathode, and short-circuit and open-circuit failure are important forms of hollow cathode failure. Herein, we compare multiple groups of constant voltage power supply mode (U mode) and traditional constant current power supply mode (I mode) for the same structural heater, and reliability analysis is performed using two-parameter Weibull distribution. The results show that under the constant voltage power supply mode, there is a negative feedback mechanism that increases the resistance of the heater, and the overall heating power decreases. This extends the heater's lifetime and reduces dispersion of resistance variations, leading to a substantial increase in the lifetime reliability of the heater in the constant voltage mode. Finally, we propose a current limiting method that starts when the constant voltage power supply is applied and solves the problem of excessive current surge when the heater starts.

Application of fuzzy control method in gas metal arc welding

In the short circuit transfer welding processes, a frequent change of arc length often causes dissatisfactory bead formation, but the control for arc length is nonlinear and complicated as it is difficult to derive a mathematical model of the controller. Thus, conventional controllers such as constant voltage power supply with constant wire feed speed cannot keep the arc length stable. This work presents a fuzzy controller using Mamdani method to stabilize the arc in gas metal arc welding (GMAW), where the deviation of arc voltage and its change rate serve as the input, and the large current at the initial arcing stage is the output. The controller is simple and easy to implement, because it has only one control object (i.e., welding current) in the system. To assess the validity of this method, two experiments on torch height change and upward slope welding were carried out, and the result suggests that the proposed fuzzy controller had a fast dynamic response and good stability under every condition.

Dynamic commutation torque‐ripple reduction for brushless DC motor based on quasi‐Z‐source net

The commutation torque ripple in the six-step square-wave driving mode of the brushless DC motor affects the motor performance and generates mechanical vibrations and noise when used for industrial applications. The cause of commutation torque ripple is analysed in this study and a non-linear transient model of the phase current during the commutation interval is developed. According to the transient-current model, the commutation voltage and the time required to produce a constant torque can be calculated without current sampling; this makes the control system easier to realise in industrial applications, and reduces the need for a high performance controller. Based on the pulse-with modulated chopping method and quasi-Z-source net, the proposed control system can adjust the motor speed using a constant-voltage power supply and reduce the commutation torque ripple over the entire speed-adjustable range. A torque transducer is used to measure the dynamic torque ripple in the experiment. The results show that the proposed commutation torque-ripple reduction strategy can reduce the dynamic torque ripple by about 70% in both simulation and experiment compared with the traditional driving methods.

The Response of a Heat Loss Flowmeter in a Water Pipe Under Changing Flow Conditions

A heat loss flowmeter for measuring the volume flow rate of water in real time ( $t)$ was formed using two thick film segmented thermistors, range constant voltage (RCV) power supply, acquisition card, PC, and software. The input water temperature $T_{w}(t)$ was measured by a cold thermistor, while the water flow rate $Q(t)$ was determined using the heat loss principle by measuring the self-heated thermistor current $I(t)$ . The flowmeter inertia, stability, and accuracy were measured and analyzed on a flowmeter prototype in real-time and real conditions on the water mains. The flowmeter response was measured for different durations of step input water flow-out functions and intervals between steps. An independent ultrasonic flowmeter was connected in series with the thermal flowmeter to measure the ordered input water flow functions. The realized intelligent functions in real time were: measuring the input water temperature $T_{w}(t)$ and self-heating temperature $T_{s}(t)$ , auto-selection of RCV supply voltage $U(T_{w})$ , determination and modeling of the water flow rate in real time $Q(t)$ , determination of the water volume $V(t)$ , and determination of the thermal gradient on the self-heating thermistor as a water flow indicator $\Delta R_{s}(t)$ .

Self-Powered Eddy Current Damper for Rotordynamic Applications

The vibration control of rotors is often performed using elastomeric or fluid dampers together with rolling element or hydrodynamic type bearings. Electromagnetic dampers seem a valid alternative to conventional solutions and also to active magnetic bearings (AMBs) because their simpler architecture, size and, if of transformer type, also for the absence of power electronics, position sensors, and any fast feedback loop. However, transformer eddy current dampers require a constant voltage power supply than can be provided by an embedded generator to reduce cost and improve the reliability. The present paper proposes a self-powered damper to fulfill these requirements. A three-phase permanent magnet electric generator (connected to the rotating shaft) generates the required power for the damping device. The generator is connected to the damping circuit by means of tuned impedance and a three-phase rectifier.

Analysis and optimization of a thermal sensor system for measuring water flow

A simple thermal sensor system was designed for measuring water flow in the water mains using the heat loss principle with a NTC thick film segmented thermistor as a self-heating sensor. Thick film segmented thermistors were screen printed on alumina substrate. NTC thermistor paste was formed of very fine Cu0.2Ni0.5Zn1.0Mn1.3O4 powder obtained by a combined mechanical activation/thermal treatment process, an organic vehicle and glass frit. The thermal sensor system was analyzed in the static and dynamic regime. A range constant voltage power supply was defined in the range 9–19V for input water temperatures of 30–2°C, maintaining a supply voltage in steps of 2V for a change in 5°C of input water temperature. This enables optimal operating power, i.e. heat generation on the self-heating thermistor. Measured calibration curves for different input water temperatures and input water flow rates were modeled, enabling interpolation of additional calculated curves to cover a wide range of input water temperatures.

Comparison of entropy production rates in two different types of self-organized flows: Bénard convection and zonal flow

Two different types of self-organizing and sustaining ordered motion in fluids or plasmas—one is a Bénard convection (or streamer) and the other is a zonal flow—have been compared by introducing a thermodynamic phenomenological model and evaluating the corresponding entropy production rates (EP). These two systems have different topologies in their equivalent circuits: the Bénard convection is modeled by parallel connection of linear and nonlinear conductances, while the zonal flow is modeled by series connection. The “power supply” that drives the systems is also a determinant of operating modes. When the energy flux is a control parameter (as in usual plasma experiments), the driver is modeled by a constant-current power supply, and when the temperature difference between two separate boundaries is controlled (as in usual computational studies), the driver is modeled by a constant-voltage power supply. The parallel (series)-connection system tends to minimize (maximize) the total EP when a constant-current power supply drives the system. This minimum/maximum relation flips when a constant-voltage power supply is connected.

Design and Implement of Low Ripple and Quasi-digital Power Supply

Abstract A switch linearity hybrid power supply based on single chip microcomputer is designed which merged the merits of the switching and linear power supply. Main circuit includes pre-regulator which works in switching mode and series regulator which works in linear mode. Two-stage regulation mode was adopted in the main circuit of the power. A single chip computer (SCM) and high resolution of series D/A and A/D converters are applied to control and measurement which achieved continuous adjustable and low ripple constant current or voltage power supply

Comparação do desempenho operacional e das características do cordão na soldagem com diferentes arames tubulares em polaridade negativa

Este trabalho objetivou o estudo comparativo das características do cordão produzido por arames tubulares nacionais dos tipos rutílico (ASME SFA-5.20: E71T-1/E71T-9/E71T-9M), básico (ASME SFA-5.20: E71T-5/E71T-5M) e "metal cored" (ASME SFA-5.18: E70C-3M) com 1,2 mm, destinados à soldagem de aços estruturais de baixo e médio teor de carbono. Realizaram-se testes de soldagem com o eletrodo na polaridade negativa (CC-), na posição plana, sobre chapas grossas (espessura de 12 mm) de aço carbono comum de baixo carbono utilizando-se uma fonte operando no modo "tensão constante" e com monitoração dos sinais de corrente e tensão do arco e velocidade de alimentação (fusão) do arame. Variaram-se, na soldagem com cada tipo de arame tubular, a composição do gás de proteção (75%Ar-25%CO2 e 100%CO2) e a velocidade de alimentação do arame (7 e 9 m/min). Os demais parâmetros foram mantidos fixos, incluindo-se, além da polaridade negativa do eletrodo, os comprimentos energizado do eletrodo (16 mm) e do arco (3,5 mm). Para os diferentes arames tubulares, avaliaram-se comparativamente as principais características do cordão, incluindo a sua geometria (penetração, reforço, largura, área fundida, área depositada e diluição), presença de descontinuidades, microestrutura e dureza. Levantaram-se as condições operacionais associadas a um cordão com características adequadas à soldagem de chapas grossas de aços estruturais com a polaridade do eletrodo negativa.

Parameters Design of Main Circuit of AC Constant Voltage Power Supply Based on Dual Directional Reversible PWM Control

The constant voltage power supply with dual directional reversible PWM compensation has merits of high precision, high efficiency, small volume, and so on. To ensure the quality of supply, it is important to fix the value of inductance, capacitance in main circuit. From the angle of filtering, and through analysis of the circuit working, detailed formulas of the inductance and capacitance calculation are given and an example of it is given too. In parameters calculation, to reduce the volume, the filter inductance is taken a smaller value but the capacitance is taken a greater value; the DC smoothing capacitance should be chosen according to the amplitude limit of DC voltage rising in inversion, and should be taken as great as possible to maintain voltage stabilizing precision.

Bead characterization of FCAW of a rutilic fluxed core wire

This paper studies the effect of operational conditions on bead shape characteristics in fluxed core arc welding with a Brazilian-made wire with rutilic flux (ASME SFA-5.20: E71T-1/E71T-9/E71t-9M) of 1.2 mm in diameter. Bead-on-plate downhand welding trails were performed on 12 mm-thick low-carbon steel plates with a constant voltage power supply. A digital data logging system was used to measure the welding current and voltage, and wire feed rate. While the shielding gas composition (75% Ar–25% CO2 and 100% CO2), wire polarity, and feed rate (7 and 9 m/min) were varied during the trials, the electrode voltage (16 mm) and arc length (3.5 mm) were not changed. Weld bead characteristics (penetration depth, width, and fused and deposited areas), the presence of discontinuities, bead microstructure, and hardness were evaluated. Welding conditions of high productivity (high deposition rate) associated with adequate bead characteristics were determined for the wire.

Caracterização do cordão na soldagem FCAW com um arame tubular "metal cored"

Este trabalho objetivou o estudo do efeito de algumas condições operacionais nas características do cordão produzido por um arame tubular "metal cored" (ASME SFA-5.18: E70C-3M) de fabricação nacional com 1,2 mm de diâmetro, destinado à soldagem de aços carbono comuns estruturais de baixo e médio teor de carbono. Realizaram-se testes de soldagem, na posição plana, sobre chapas grossas (espessura de 12 mm) de aço de baixo carbono utilizando-se uma fonte operando no modo "tensão constante" e com monitoração dos sinais de corrente e tensão do arco e velocidade de alimentação (fusão) do arame. Variaram-se a composição do gás de proteção (75%Ar-25%CO2 e 100%CO2), a polaridade do eletrodo (positiva e negativa) e a velocidade de alimentação do arame (7 e 9 m/min). Os demais parâmetros de soldagem foram mantidos fixos, incluindo-se os comprimentos energizado do eletrodo (16 mm) e do arco (3,5 mm). Avaliaram-se os efeitos das condições operacionais nas principais características do cordão incluindo a sua geometria (penetração, reforço, largura, área fundida, área depositada e diluição), presença de descontinuidades, microestrutura e dureza. Levantaram-se, para o arame "metal cored", as condições operacionais de maior produtividade (maior taxa de deposição) associadas a um cordão com características adequadas à soldagem de chapas grossas de aços estruturais.

Comparação do desempenho operacional e das características do cordão na soldagem com diferentes arames tubulares

Este trabalho objetivou o estudo comparativo das características do cordão produzido por arames tubulares nacionais dos tipos rutílico (ASME SFA-5.20: E71T-1/E71T-9/E71T-9M), básico (ASME SFA-5.20: E71T-5/E71T-5M) e "metal cored" (ASME SFA-5.18: E70C3M) com 1,2 mm, destinados à soldagem de aços estruturais de baixo e médio teor de carbono. Realizaram-se testes de soldagem, na posição plana, sobre chapas grossas (espessura de 12 mm) de aço carbono comum de baixo carbono utilizando-se uma fonte operando no modo "tensão constante" e com monitoração dos sinais de corrente e tensão do arco e velocidade de alimentação (fusão) do arame. Variaram-se, na soldagem com cada tipo de arame tubular, a composição do gás de proteção (75%Ar-25%CO2 e 100%CO2) e a velocidade de alimentação do arame (7 e 9 m/min). Os demais parâmetros foram mantidos fixos, incluindo-se a polaridade do eletrodo (CC+) e os comprimentos energizado do eletrodo (16 mm) e do arco (3,5 mm). Para os diferentes arames tubulares, avaliaram-se comparativamente as principais características do cordão, incluindo a sua geometria (penetração, reforço, largura, área fundida, área depositada e diluição), presença de descontinuidades, microestrutura e dureza. Levantaram-se as condições operacionais associadas a um cordão com características adequadas à soldagem de chapas grossas de aços estruturais.

A 30 kJ Bi2223 High Temperature Superconducting Magnet for SMES with Solid-Nitrogen Protection

A conduction-cooled high temperature superconducting (HTS) magnet system through a solid nitrogen protection with energy storage of 30 kJ was developed. The HTS magnet system is used to investigate fast discharging performances with a constant output voltage. The superconducting magnet consists of 14 double pancakes wound with Bi2223 tape with the length of 200 m. The magnet has an outer diameter of 212 mm and a clear bore of 108 mm. Cryostat for the HTS magnet system is designed and the coil is cooled with a GM cryocooler together with the solid nitrogen protection technology. The superconducting magnet is fabricated and tested. The operating current is about 155 A with raping rate of 5 A/s. It can generate a central magnetic field of 4.31 T at a temperature lower than 20 K. In this paper, the magnet design, coil fabrication and cryogenic system are presented. Experimental research of the superconducting magnet as a constant voltage power supply was carried out.