Ampere Characteristics Research Articles

Field Weakening Characteristics Computed with FEM-Coupled Algorithms for Brushless AC Motors

Finite Element Method (FEM) analysis tools are the most adopted in the design of brushless alternating current motors due to the advantage of considering multi-physics effects with dependencies of variables such as cross-coupling, saturation and others that are not possible to be modeled analytically with high precision. During the design process designers compute operation points such as maximum torque per ampere or flux weakening characteristics that cannot be targeted directly on the FEM tool. Therefore, designers make a sweep of simulations and post-processed the data in order to obtain the results, this is repetitive particularly in the conceptual phase of the design where features of the motor are still not defined. This paper presents nine algorithms as an alternative to compute with iterative methods operation points that cannot be targeted directly on a FEM tool. The algorithms must be coupled to the FEM tool and can compute complex points such as the characteristic current and modes of operations limits within acceptable range of error and times of execution for practical purposes. Validation of the algorithms using Jython is presented with results for the three types of brushless motors (non-salient, interior permanent magnet and reluctance motor).

Generation of Terahertz Pulsed Radiation with Photoconductive Antennas Based of Low-Temperature-Grown Gallium Arsenide and Its Applications

.

Prebreakdown characteristics of weakly ionized liquid and gaseous media in the strongly nonuniform electric field

A theoretical model of electrohydrodynamic prebreakdown phenomena in slightly ionized (weakly conductive) media is proposed. The electric high voltage conduction of weakly conductive liquids and slightly ionized gases in intense electric fields using this model is considered. The formula for the calculations of volt–ampere characteristics under high voltage spherical capacitor field is analytically obtained. The experimental corona discharge volt–ampere characteristics of air are presented. It was found that the size of the ionization region in the case of corona discharge in air increases monotonically with increasing discharge voltage.

Determination of Ion Temperature from the Volt–Ampere Characteristics of Electrolytes

The author presents experimental volt–ampere characteristics measured in various media. From them, the density of ions and their temperature have been determined. An estimating formula has been derived for the thickness of a space-charge layer. It has been proposed in this work that the Fermi distribution function be used to calculate the thickness of a space-charge layer. A procedure has been presented to determine the ion temperature in electrolytes. The error of the described procedure amounts to 15–20%. To correct the ion temperature in the media, it is necessary to take account of the shielding of electrodes in the ion layer.

The influence of electrode configuration on light emission profiles and electrical characteristics of an atmospheric-pressure plasma jet

In this paper we focus on the influence of the type of electrodes, their dimensions and inter-electrode gap on the formation of a helium plasma jet. Plasma emission profiles are recorded by an ICCD camera simultaneously with volt–ampere characteristics for three different copper electrode configurations. The delivered power was up to 6.5 W, but it may be set and controlled to 0.1 W. This study shows how the electrode configuration shapes and controls temporal and spatial plasma development as well as electrical characteristics of an atmospheric pressure plasma jet. It is shown that, in our system, the width of the grounded electrode has no significant influence on the formation and properties of pulsed atmospheric-pressure streamers (PAPS) outside the tube, while the width of the powered electrode is crucial in their formation.

Cylindrical-probe diagnostics of plasma flows effusing from technological plasmatrons

Mathematical and numerical models have been considered for the problem of collisional plasma flow from a technological plasmatron past a cylindrical probe. A set of theoretical volt–ampere characteristics that can be used to process probe experiments has been presented. Novel probe techniques of processing natural probe experiments for collisional plasma have been described.

Effect of some carbon nanomaterials on ethanol oxidation by Gluconobacter oxydans bacterial cells

The effect of carbon nanomaterials (carbon nanotubes, thermally expanded and pyrolytic graphite) on the bioelectrochemical activity of Gluconobacter oxydans bacterial cells was studied during sorption contact with nanomaterials. For bacterial immobilization, the surface of a working bioelectrode was modified via the application of bacterial suspension in the studied nanomaterial and chitosan. The bioelectrochemical electrode characteristics (the amplitude of generated potential, cyclic volt–ampere characteristics, resistance) were estimated before and in the process of bacterial interaction with ethanol (3-electrode measurement scheme). Modification of the spectral graphite electrode by carbon nanotubes allowed a decrease in the resistance of the charge transfer by 48% and an increase in the oxidation current on cyclic volt—ampere characteristics at a voltage of 200 mV by 21% as compared with nonmodified electrode. The thermally expanded and pyrolytic graphite increased the bioelectrode resistance to 4050 and 8447 Ohm cm2, respectively. Mathematical modeling demonstrated that from 75 to 100% of biomaterial (depending on the used nanomaterial) were involved in the process of electricity generation with the selected method of the bacterial immobilization. The use of data obtained during the development of microbial biosensors and electrodes of biofuel cells is discussed.

Field emission properties of pointed cathodes based on graphene films on SiC

Electrical properties of low-threshold field emission cathodes produced by growth nanocluster graphene films on the pointed surface of heavily doped n +SiC by sublimation epitaxy have been considered. The quality of the graphene coating has been assessed based on the morphological studies and Raman spectroscopy. Using the volt–ampere characteristics the work function from a pointed cathode with graphene coating was calculated (∼ 0.76 eV). Such a low value of the work function is explained on the assumptions that the graphene film has the nanocluster nature and the sources of the field emission are graphene nanoclusters.

Effects of Electric Discharge Plasma Treatment on the Thermal Conductivity of Polymer–Metal Nitride/Carbide Composites

High-density polymer composites with semiconductor or dielectric fillers such as aluminum nitride (AIN), aluminum oxide (Al2O3), titanium carbide (TiC), titanium nitride (TiN), boron nitride (BN), silicon nitride (Si3N4), and titanium carbonitride (TiCN) were prepared by the hot pressing method. Each powder phase of the composites was exposed to an electric discharge plasma process before composite formation. The effects of the electric discharge plasma process and the filler content (volume fraction) on the thermal conductivity, volt–ampere characteristics, thermally stimulated depolarization current, as well as electrical and mechanical strength were investigated. The results of the study indicate that, with increasing filler volume fraction, the thermal conductivity of the samples also increased. Furthermore, the thermal conductivity, and electrophysical and mechanical properties of the high-density polyethylene + 70% BN composite modified using the electric discharge plasma showed improvement when compared with that without electric discharge plasma treatment.

Temperature Correction in Probe Measurements

This work is devoted to experimental investigations of a decaying plasma using Langmuir probes. The gas pressure, the discharge current, and the moment of afterglow were selected to obtain probe characteristics in collisionless, intermediate, and drifting regimes of motion of charged particles. The manner in which the shape of the volt–ampere characteristics changes on passage from the collisionless motion to diffusion motion has been shown. A detailed analysis has been made of the source of errors arising when orbital-motion formulas or the logarithmic-operation method are applied to processing of the probe curves. It has been shown that neglect of collisions of charged particles in the probe layer leads to an ion-density value overstated more than three times, an electron-temperature value overstated two times, and an ion temperature overstated three to nine times. A model of interaction of charged particles in the probe layer has been proposed for correction of the procedure of determining temperature. Such an approach makes it possible to determine the space-charge layer in the probe, and also the value of the self-consistent field. The use of the developed procedures gives good agreement between experimental and theoretical results.

Determination of Weber-Ampere Characteristics of Electric Devices Using Solution of Inverse Problem of Harmonic Balance

This work is devoted to development of measurement of weber--ampere characteristic of electric devices consisting of a magnetic core and a coil. In this method the coil of electric device is energized with sinusoidal voltage of known amplitude and frequency, and harmonic amplitudes of passing current are measured. On the basis of these data the inverse problem of harmonic balance is solved and the approximation coefficients of the equation describing the required weber--ampere characteristic are determined. The influence of the degree of approximating expression on measurement error is studied. The obtained results have demonstrated possibility of application of the proposed method to measurements of weber--ampere characteristics of electric devices. The measurement error of weber--ampere characteristic does not exceed 3 %.

Nonlinear Effects in MSM Structures Based on Ag4SSe

MSM structures W–Ag 4 SSe–W have been produced and their volt–ampere characteristics in the temperature range 290–350 K and at a temperature of 77 K were investigated. It is shown that the volt–ampere characteristic of such an MSM structure is substantially nonlinear and takes an N-like shape at different polarities of the voltage applied to the structure and that the portion of this characteristic corresponding to the negative resistance of the structure is preceded by the portion with a zero slope. It was established that the breakdown voltage of the volt–ampere characteristic of an W–Ag 4 SSe–W structure is determined by its temperature and is equal to ~0.3 V, which corresponds to the strength 1 V/cm of the electric field in it, and that the breakdown current of the structure changes by the law I ~ T 0.25 with increase in its temperature. The nonlinearity of the volt–ampere characteristics with a negative-resistance portion of the W–Ag 4 SSe–W structures obtained is explained by the existence of the trapping level in them at a certain state of the electrons at the metal–semiconductor interface.

Probe diagnostics in helium plasma, generated by a volume source of fission fragments

In the present paper experimental results of probe measurements in nuclear induced helium plasma are presented and analyzed. Both parts of olt–ampere characteristics (VAC) of the probe are used to get the density of electrons and positive ions in plasma. Plasma is formed by products of the reaction 3􀜪􀝁􀵅􀝊􀕜􀝌􀵅􀜶􀵅􀍲.􀍹􀍸􀜯􀝁􀝒 and studied under the pressure to be equal 760 torr and neutral flux about 1013–14 cm–2 s–1. The linear part of VAC and its slope might be used to evaluate density and temperature of the studied plasma. In some special cases like plasma diagnostics in the core of active of nuclear reactor the probe diagnostic methods is the only one possible experimental technique which makes possible to extract uclear induced plasma property information. Electrostatic probe represents ubstantially a metal electrode placed in the diagnostic cell, inserted in the active zone of nuclear reactor and within which the tested mixture is ploaded.

Defect states in amorphous Ge2Sb2Te5 phase change material

Steady-state photoconductivity measurements in the temperature range 100–300 K on amorphous Ge2Sb2Te5 thin film prepared by dc sputtering are analyzed. The dark conductivity is thermally activated with a single activation energy that allocates the position of the Fermi level approximately in the middle of the energy gap relative to the valance band edge. The temperature dependence of the photoconductivity ensures the presence of a maximum normally observed in chalcogenides with low- and high-temperature slopes, which predict the location of discrete sets of localized states (recombination levels) in the gap. The presence of these defect states close to the valence and conduction band edges leaves the quasi Fermi level shifts in a continuous distribution of gap states at high temperatures, as evidenced from the γ values of the lux–ampere characteristics.

Influence of the cathode surface conditions on V–A characteristics in low-pressure nitrogen discharge

In this paper we demonstrate and analyse the influence of cathode surface inhomogeneities on the breakdown, volt–ampere (V–A) characteristics and the spatial structure of the low-pressure non-equilibrium discharges. The idea for this work came from the need to explain the non-typical V–A characteristics (positive slope of the characteristics in low-current regime of the discharge) that we observed in a parallel-plate, dc discharge in nitrogen. It was found that the cathode was locally conditioned by the discharge that operated in the constricted glow regime. Spatial inhomogeneity of the cathode surface strongly affected the subsequent operation in the breakdown-Townsend regime where discharge is supposed to be uniform.

Sheet resistance of alumina ceramic after high energy implantation of tantalum ions

Abstract The results of investigation of the sheet resistance of alumina ceramic as a function of the fluence of implanted metal ions are presented. Tantalum ions with the average energy about 145 keV were used in experiments. Estimation of the sheet resistance was performed from analysis of volt–ampere characteristics by measuring the leakage current at a voltage between 100 V and several kilovolts, which was applied at a small area of the implanted surface. Energy dispersive X-ray analysis was used to determine composition of elements in the surface of the implanted ceramics. As a practical application of research results, it was shown that, after the creation of a weak conducting layer on the surface of the ceramic insulator, the electric field strength of the flashover increases by more than 25%.

Electrochemical performance study of solid oxide fuel cell using lattice Boltzmann method

A comprehensive numerical model was developed to predict the electrochemical performance of solid oxide fuel cell (SOFC). The multi-component Lattice Boltzmann (LB) model based on kinetic theory for gas mixtures combined with a representative elementary volume (REV) scale LB algorithm based on the Brinkman equation for flows in porous media, the Butler–Volmer equation and Ohm's law were adopted to deal with the concentration, activation and ohmic overpotentials, respectively. The volt–ampere characteristics were calculated and compared with those obtained by the existing electrochemical model, as well as the experimental data. It was shown that the electrochemical model given by this paper was capable of describing the electrochemical performance much more accurately because of the kinetic nature of the LB method which was based on microscopic models and mesoscopic kinetic equations for fluids, and the accurate prediction of multi-component mass transfer in SOFC porous electrodes affected the simulation of the cell electrochemical performance significantly. Moreover, the effects of different electrode geometrical and operating parameters on the cell performance were investigated. The developed electrochemical model based on LB algorithm at REV scale is useful for the design and optimization of SOFC.

Speed Control of DC Motor Using PSO Tuned PI Controller

The control of DC motor system is difficult and mathematically tedious due to their high non linearity property. To overcome this difficulty, a new approach has been required. This paper presented a systematic procedure to develop PI based speed controller for DC motor. The designing of speed controller through state estimation approaches. The optimal parameter of PI controller is finding out by using PSO algorithms.The performances and characteristics of DC motor are observed. The simulation results verify that steady state error is reduced, the rising time is improved and the disturbances affect is reduced hence the better performances of DC motor. with a constant speed rotating field. It is observed that most of the industry is operating under stress condition further load parameter and control variable exhibit uncertainness in real practice and in fact these are random variables. Calculated values of load variable normally contain various inaccuracies. It has been observed that error may vary in the range of 5-10%. A few percentage error may be required tolerable in the area of the load speed controlling where these inaccuracies in the entire controller. In such situation minor inaccuracy in speed control are of little concern. Further the speed controller can always be designed to have sufficiently low effect on the non linearity of DC motor; so as to worst effect of parameter uncertainty can be accounted. In real time operation, the situation is different; design controller may encounter situation never imagined by designer before it took its present shape. Hence, in real time operation condition, risk of affecting nonlinearity of motor is always present. Here it is designed a controller which not affects the nonlinearity in DC motor. II. DcMotor The stator of the DC motor has poles, which are excited by DC current to produce Magnetic fields. The rotor has a ring-shaped laminated iron-core with slots. Coils with several turns are placed in the slots. The distance between the two legs of the coil is about 180 electric degrees. DC motors are characterized by their versatility. By means of various combinations of shunt, series and separately excited field winding they can be designed to display a wide variety of volt ampere or speed torque characteristics for both dynamic and steady state operation. The separately excited dc motor model is chosen for its good electrical and mechanical performances rather than other DC motor models. The DC motor is driven by applied voltage. In DC motor, the torque may be controlled by varying the armature current or field current. One of these is varied to control the torque while the other is held constant.

Laser plasma ion implantation and deposition of platinum for SiC-based hydrogen detector fabrication

A pulsed plasma plume obtained by pulsed laser irradiation of a Pt target was used to fabricate a hydrogen sensor on a 6H–SiC single crystal by means of ion implantation followed by thin film deposition. To realize the ion implantation, high voltage pulses with positive polarity were applied to the Pt target when the laser plasma expanded from the target to the SiC substrate. Experimental diagnostics of pulsed ion beams extracted from laser-produced plasma were performed and the structure of the SiC crystal after high-temperature (500°C) ion implantation was studied by Rutherford backscattering spectroscopy of 4He+ ions. At the same time, a one-dimensional model of the plasma movement in a pulsed electric field was developed and simulations were carried out using the particle-in-cell method. Modeling allowed determination of the ion energy distribution depending on the delay time of the high voltage pulse after the laser pulse. The calculated energy distribution of Pt ions was used to predict the depth profile of implanted Pt ions in the SiC substrate. The predicted profile agreed sufficiently well with the experimentally measured depth distribution of Pt in the SiC substrate. To characterize the fabricated SiC sensor, the current flow through a barrier structure was studied. The volt–ampere characteristics of the structure were measured in air and in a mixture of air and hydrogen (2%) at a temperature of 500°C. The characteristic value of the change in voltage exceeded 2V at the bias current of 1mA when hydrogen was added to the air. The response of the sensor to the hydrogen was stable after long-term tests while the structure of the Pt film was disturbed. The ion-implanted layer operated as a series resistance, which had a significant effect on the current flow through the barrier structure. The resistance decreased under the influence of hydrogen and persisted during long-term tests.

The relationship between the n-value and applied strain

The most popular fit for describing the volt–ampere characteristic of a superconducting material is a power law with exponent n. Usually for a Nb3Sn wire the n-index is parametrized as a function of the sole critical current (Ic). An experiment to determine whether the n-index also shows an explicit dependence on the strain (ε) has been performed for an ITER (International Thermonuclear Experimental Reactor) wire. From the same wire, three pairs of samples were prepared. The three pairs were mounted on two Ti-ITER barrels, on two 316L stainless steel barrels and on two INCONEL™ alloy C-276 barrels, and heat treated. The critical current was then measured in the field range of 9–15 T. From the Ic measurements it was possible to derive three n versus Ic curves. Each curve corresponds to a different applied strain, as the three barrel materials have different thermal contraction coefficients. By analysing the three curves, the explicit dependence of the n-index on the strain is evaluated. In the strain range covered by the measurements (up to ≈−0.65% intrinsic strain), the n-value scales with the sole critical current Ic.