Different Types Of Generators Research Articles

Simulation of a Transient Fault Controller for a Grid Connected Wind Farm with Different Types of Generators

This paper aims to simulate a wind farm model that includes wind turbine and three different types of generators , which are three-phase synchronous generator, three-phase squirrel-cage induction generator and three-phase doubly-fed induction generator ,these generators are the main machines that generally used in the field of wind energy generation. All generators are connected in parallel at the point of common coupling (PCC) and connected to the utility grid. This model is a simple representation of the actual model of Zafarana, which is the biggest wind farm in Egypt and further to use it in different kinds of simulations, and display the difference in response among all generators with the same power rating (500 kW) and subjected to the same operating conditions and faults. This paper describes the simulation of the different faults that occur along the transmission line of the power system such as single-line fault, line to line fault, double lines to ground fault, and finally three line faults. The response of the wind turbine and the different generators will be analyzed and discussed to compare the transient response of all generators at the different types of faults, where the fault period is selected to be 300 ms. The model is created in MATLAB software that enables the dynamic and static simulations of electric, electromagnetic and electromechanical systems. The machines are standard blocks in the software library. Keywords : transient faults, wind farm, simulation model. DOI: http://dx.doi.org/10.11591/ijpeds.v1i2.104

Corpus Callosum has Different Channels for Transmission of Spatial Frequency Information

Corpus Callosum has Different Channels for Transmission of Spatial Frequency Information

Optimal Power Flow by Improved Evolutionary Programming

This article proposes an improved evolutionary programming (IEP) for solving optimal power flow (OPF) with nonsmooth and nonconvex generator fuel cost curves. Initially, the whole population is divided into multiple subpopulations, which are used to perform the parallel search in divided solution space. IEP includes Gaussian and Cauchy mutation operators in different subpopulations to enhance the search diversity, selection operators with probabilistic updating strategy to avoid entrapping in local optimum, and reassignment operator for every subpopulation to exchange search information. The proposed IEP was tested on the IEEE 30 bus system with three different types of generator fuel cost curves. It is shown that IEP total generator fuel cost is less expensive than those of evolutionary programming, tabu search, hybrid tabu search and simulated annealing, and improved tabu search, leading to substantial generator fuel cost savings. Moreover, IEP can easily facilitate parallel implementation to reduce the computing time without sacrificing the quality of solution.

Study of gels of molybdenum with cerium in the preparation of generators of 99Mo - 99mTc

99mTc has ideal nuclear properties for organ imaging in nuclear medicine, and it is obtained from the 99Mo-99mTc generator. Four different types of generators are available: chromatographic that uses 99Mo from fission of uranium; MEK solvent extraction; Tc2O7 sublimation; gel chromatographic. This work presents the preparation of gel generators of molybdenum with cerium and characterization of the gels: mass ratio between molybdenum and cerium, structure, size of particles and elution percentage of 99mTc after irradiating the gels. Eight gels were prepared at the same temperature of 50 ºC with concentrations of NaOH of 2 and 4 mol/L, mass ratio of 0.31 and 0.38 and final pH of 3.5 and 4.5. The analysis of the results proved that these gels are not adequate for preparation of the generators of 99Mo-99mTc, since the elution percentages are low, when compared with the gel of molybdenum with zirconium.

Generator-Damped Torsional Vibrations of a Vertical Axis Wind Turbine

Torsional vibrations may be a critical issue for those vertical axis wind turbines having long drive trains as compared with standard horizontal axis wind turbines. Such vibrations are studied by simulation for two different types of generators used with a vertical axis wind turbine, namely a conventional induction generator with a gearbox and a directly-driven multipole synchronous generator. The synchronous generator has been designed with FEM simulations. The didactic calculations show from first principles that a directly-driven generator is to be preferred when torsional vibrations are considered, since the eigenfrequency of the fundamental vibration is greater for a directly driven generator than otherwise. Thus, the risk of resonance is reduced in a stiff assembly. The generator damping of the vibrations for the simulated, directly-driven synchronous generator is also studied.

Visual evoked potential interhemispheric transfer time in different frequency bands

Objective: Visual evoked potentials (VEP) have been used to estimate interhemispheric transfer time (IHTT). However, the complex wave of VEP is most probably formed by different generators of neural populations that act through different frequency channels. If the main peaks of VEP are established by different types of generators, which can also be connected to each other by a different type of callosal fibres, we would be able to estimate a wide range of various IHTT by measuring the latency between time-locked peaks of narrow band-pass filtered VEP. This research aimed to test this hypothesis. Mmethods: Nine right-handed men were presented with a reversal of a checkerboard pattern as stimuli at RVF or LVF, and EEG was recorded at O1, O2, P3, P4. The grand-averaged VEPs were transformed to the frequency domain by means of the fast Fourier transform to obtain the amplitude frequency characteristics. Band-pass filters were chosen adequately, according to tuning frequencies indicated by clear peaks in the amplitude frequency characteristics. The chosen band pass filters (4–8 Hz, 8–15 Hz, 15–20 Hz, 20–32 Hz) were applied to the VEP of the subjects, and 4 different components of VEPs for each VEP were obtained. The latency of P100 and N160 of unfiltered VEP was measured. In the band-pass digital filter applied VEPs, positive and negative peaks, which are consistent with P100 and N160, were measured for each subject. Latency differences between hemispheres for digitally unfiltered and filtered VEPs were computed to estimate IHTT. Results: In the different frequency bands, different IHTTs were estimated, ranging from 3 ms to 30 ms. Approximately 16 ms for theta band, 11 ms for alpha band, 6 ms for 15–20 Hz and 3 ms for 20–32 Hz bands were found. Conclusions: Our findings support the hypothesis which states that unfiltered VEPs provide us with only a rough estimation of IHTT. Also, they are consistent with anatomical findings that describe callosal fibres of varying dimensions, predicting various velocities between hemispheres.

574 Intellectual peculiarities of boys and girls with different laterality indices

Objective: Visual evoked potentials (VEP) have been used to estimate interhemispheric transfer time (IHTT). However, the complex wave of VEP is most probably formed by different generators of neural populations that act through different frequency channels. If the main peaks of VEP are established by different types of generators, which can also be connected to each other by a different type of callosal fibres, we would be able to estimate a wide range of various IHTT by measuring the latency between time-locked peaks of narrow band-pass filtered VEP. This research aimed to test this hypothesis.Mmethods: Nine right-handed men were presented with a reversal of a checkerboard pattern as stimuli at RVF or LVF, and EEG was recorded at O1, O2, P3, P4. The grand-averaged VEPs were transformed to the frequency domain by means of the fast Fourier transform to obtain the amplitude frequency characteristics. Band-pass filters were chosen adequately, according to tuning frequencies indicated by clear peaks in the amplitude frequency characteristics. The chosen band pass filters (4–8 Hz, 8–15 Hz, 15–20 Hz, 20–32 Hz) were applied to the VEP of the subjects, and 4 different components of VEPs for each VEP were obtained. The latency of P100 and N160 of unfiltered VEP was measured. In the band-pass digital filter applied VEPs, positive and negative peaks, which are consistent with P100 and N160, were measured for each subject. Latency differences between hemispheres for digitally unfiltered and filtered VEPs were computed to estimate IHTT.Results: In the different frequency bands, different IHTTs were estimated, ranging from 3 ms to 30 ms. Approximately 16 ms for theta band, 11 ms for alpha band, 6 ms for 15–20 Hz and 3 ms for 20–32 Hz bands were found.Conclusions: Our findings support the hypothesis which states that unfiltered VEPs provide us with only a rough estimation of IHTT. Also, they are consistent with anatomical findings that describe callosal fibres of varying dimensions, predicting various velocities between hemispheres.

Evaluation of absorption cycles with respect to COP and economics

The calculation of the performance of absorption heat pump cycles or the comparison of different types of machine cannot be done in a reasonable way without considering the first cost of the machine and especially the cost of the heat exchangers, as their area and particularly the distribution of the area between the respective components of the heat pump determine the COP. Therefore it makes sense only to compare machines that are optimized in this respect. A good way to evaluate cycles is to calculate the maximum COP in terms of the total cost of the heat exchangers. For that purpose a computer program was developed for different absorption heat pump cycles with water as refrigerant. The calculation method is simple and thus the result reliable. The program is suitable for evaluating double-lift, single-, double- and some triple-effect cycles, each one with different absorption fluids and with different options, such as different solution flows (parallel, serial), different types of absorber (spray- or falling-film absorber), and different types of generator (pool- or falling-film generator). With this instrument different cycles or similar cycles with different features can be compared. An economically significant estimation of the performance of a cycle working under defined conditions is possible.

Theoretical modeling of chemical generators producing O2(1Δ) at high pressure for chemically pumped iodine lasers

A theoretical model is developed for chemical generators producing O2(1Δ) at high pressure. Such generators are especially important for supersonic chemical oxygen-iodine lasers. The model treats different types of generators, e.g., bubble-column, film, aerosol, and jet generators. The main factor affecting the O2(1Δ) yield under high pressure is liquid-phase quenching enhanced by depletion of HO2− ions near the gas/liquid interface. Simple analytical expressions are derived for the O2(1Δ) yield at the exit of the generator. Output characteristics of different specific generators are calculated and compared with available experimental results. O2(1Δ) yield ≥0.5 can be achieved for oxygen pressure up to 50 Torr and flow rates of 3 mmol/cm2 s. For equal velocities of the gas and the liquid the maximum flux of the energy carried by O2(1Δ) for jet or aerosol generators reaches 200 W/cm2. It can be increased by increasing the liquid velocity in the generator.

Performance of different types of renewable power supply systems

SYNOPSIS A combination of different types of generator has proved useful on technical and economic levels. In this paper we investigate the performance of a hybrid Photovoltaic(PV)-Wind generator power supply system operating under good and fair insolation and wind regimes. The effectiveness of such a hybrid system is measured by the Relative Sizing Parameter (RSP), Money Saving Parameter (MSP), and the Overall Reliability Parameter (ORP). Under specified weather conditions and for a nominal load demand, the RSP relates the product of the PV-modules and storage batteries involved in sizing the PV-Wind hybrid system to those of a stand alone PV-system sized to meet the same load. The MSP reports the difference between the total costs of a stand-alone PV power supply system and a hybrid PV-Wind power supply system, both sized to meet the same load, as a percentage of the total costs involved in supplying the load with a stand-alone PV power supply system only. The ORP compares the yearly average of the daily excess energy (positive difference between generated and consumed energy) of the hybrid system to that of the stand-alone PV power system. Based on this strategy we were able to develop a number of design diagrams which can be used in judging the benefits of utilizing hybrid PV-Wind generators on both economic and energy reliability grounds.

Generators, x-ray tubes, and exposure geometry in mammography.

The author reviews different types of generators used in mammography, x-ray tubes, and physical principles affecting exposure geometry. Target and filter combinations, focal spots, and unsharpness are discussed in detail.

Effect of relaxation times on the dynamics of lasing in a laser with a bleachable filter

In this work the authors analyze a dynamic system describing a laser whose bleachable filter has a finite relaxation time. The effect of the finiteness of this time on the character and arrangement of the regions of parameters with different types of generation is shown, and the dynamic regimes of such a laser and a laser with a filter with a zero time constant are compared.

Energy characteristics of harmonic internal wave generators

The propagation of internal waves plays an important role in liquid media with layers that vary according to density (stratified liquids) and are located in a gravitational field, which include the Earth's atmosphere and oceans. Highly controlled experiments are essential for investigating efficient generators of internal waves (in particular, harmonic internal waves). Hence, it is important to compare the efficiences of various types of internal wave generators. This problem is considered for the simplest forms of stratification: discontinuous and uniform (with a constant buoyancy frequency N). Although there are very few studies of oscillations in the case of discontinuous stratification, there are even fewer investigations of uniform stratification (e.g., see [1–4]). A comparison of the efficiences of different types of generators has not been made for the latter case. This is done below on the basis of energy estimates for two types of generators: for objects (a sphere or cylinder) that undergo small harmonic oscillations in a liquid and for objects with pulsating volumes.

The Use of Kr-81M in Ventilation Imaging

Radioactive gases are very useful in the study of pulmonary disorders because they allow an assessment of regional lung function. The most widely used radioactive gases are Xe-133 and, more recently, Kr-81m. This paper is a review of the physical characteristics of Kr-81m, its production from the parent Rb-81, the different methods to produce Rb-81, the different types of generators which can be used in hospitals, and the clinical applications of pulmonary ventilation imaging. The paper suggests that Kr-81m offers several advantages over previous methods that used Xe-133 due to its improved spatial resolution, its capacity to provide superimposable ventilation and perfusion images in multiple projections, and its total lung dose which is ten times lower than that of Xe-133.

Optimization studies on open-cycle MHD generators.

An optimization theory is developed which predicts the variation of thermodynamic properties, duct shape, and electrical loading along an MHD generator for minimum duct length, duct surface area, or duct volume. The model is based on the one-dimensional flow equations including heat transfer and friction, and the analysis is developed for a fluid with arbitrary dependence of density, enthalpy, electrical conductivity, and mobility on temperature and pressure. Four types of electrical loading of the generator are considered: the segmented-electrode Faraday generators; and the cross-connected generator, first with constant cross-connection angle and multiple load connections; then with a single load; and finally with constant cross-connection angle and with single load. This theory is then applied to the design of an open-cycle MHD generator for a 2000-MW power plant. Numerical results for these four different types of generator are calculated with a computer program and compared, with particular emphasis on the loading parameter variation. It is concluded that the additional constraints of constant cross-connection angle and single load do not significantly affect the overall generator performance, although they do modify the parameter variation along the duct.