Wrocław University of Science and Technology
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Time-Frequency Analysis of Complex Space-Phasor in Power Electronics
Get PDFThis paper considers applying nonparametric and parametric methods for the calculation of the time–frequency representation of nonstationary signals in power electronics. A space phasor is proposed as a complex representation of a three-phase signal to calculate the spectrum of positive- and negative-sequence components. The developed methods are tested with nonstationary multiple-component signals occurring during the fault operation of inverter-fed drives. First, the main differences between parametric and nonparametric methods are underlined. Then, some aspects of additional kernel functions are introduced on the basis of Wigner and Choi–Williams distributions. An additional comparison of uncertainty of measurements using the described methods, as well as a widely used Fourier technique, can be useful for practitioners. The proposed methods allow tracking instantaneous frequency as well as magnitude that can can lead to applications in the diagnosis and power quality areas
Phase relations in Bi2O3-SrO-CuO system at 800 degrees C
No full textPhase relations in the Bi2O3SrO-CuO system at 800°C are presented. Several binary and ternary phases existing within this system have been identified and characterised by x-ray powder diffraction and density and overall oxygen content determination. Among them, particular 'A' and 'B' phases (both of variable composition) represent potential interest from the point of view of superconductivity. Evidence of the actual stoichiometry of the 2201-type superconductor (T, = 9-20 K) and of the most probable distribution of structural component atoms within its elementary unit subcell is given. A new interpretation of the general formula for the Bi-based superconducting cuprates has been proposed
Digital Line Differential Protection Using Symmetrical Components
Get PDFA new method for digital line differential protection is presented. The protection compares the time function and the orthogonal function of the symmetrical positive- sequence component at the input and output of a transmission line. From these values the magnitude of the differential current is evaluated. The time function is calculated according to the SD4c algorithm and the orthogonal function according to the SD4s algorithm from four sampled triplets. The first results of the investigation are shown. By using this method, a phase-independent operating time of less than half a period can be obtained
New concept for fault location in series-compensated parallel lines
Get PDFNew concept for fault location in series- compensated parallel lines is presented. The developed one-end fault location algorithm offsets the series compensation and the reactance effects as well as takes the countermeasure for the mutual coupling between parallel lines. Its distinctive feature relies in no requirement of the impedance data for the equivalent systems behind both the line terminals and for the possible extra link between the substations. Moreover, complete avoiding of pre-fault measurements is provided. The sample fault location cases for the fault data obtained from versatile ATP-EMTP simulations are included and discussed
X-ray Emission Accompanying Cathode Microdischarge
Get PDFElectrical discharge in vacuum is accompanied by X-ray radiation. Knowledge of the generation mechanism of radiation may lead to its practical use. The analysis of this phenomenon indicates that it is only at the discharge development phase until the moment of the anode plasma generation that the proper conditions for X-ray generation are satisfied. The intensity of radiation is dependent on the field current intensity on the cathode surface as well as on the value of the electron current supplying the anode. The anode current at the vacuum discharge development phase has a pulse character, and the pulse amplitude is dependent on the cathode plasma density. The radiation intensity may be increased by increasing the current amplitude, e.g. by artificial plasma generation in the trigger system
Analysis of distorted waveforms using parametric spectrum estimation methods and robust averaging
No full textAfter the description of parametric methods (ESPRIT and MUSIC) and selected robust location measures (robust averaging methods), the comparison of the frequency and amplitude estimation error, based on numerical simulation is presented. Next part presents basics of selected power quality indices (harmonic sub/groups), followed by comparison of estimation error in the case of application of FFT-based algorithms and parametric methods as well as presentation of advantages of use of robust averaging
Further theoretical description for double injection in the metal-solid-metal system
Get PDFA problem of the current flow in a solid containing an arbitrary distribution of defects is presented. The different analytical forms of the electric field intensity distributions are found. The conditions in which the system can act as an n-p or ap-n blocking diode are determined. Also, it was found that the current density can decreases with the voltage. Usually, the current-voltage characteristic is strongly non-linear
Transformata ZET
Get PDFCelem ćwiczenia jest odwracanie transformaty ZET metodą rozkładu na ułamki proste, wykorzystując funkcje MATLABa, opis matematyczny systemów LTI w dziedzinie transformaty, badanie stabilności i przyczynowości systemów
Sprzętowa realizacja filtrów cyfrowych typu SOI
Get PDFCelem pracy jest poznanie sposobu fizycznej realizacji filtrów cyfrowych na procesorze sygnałowym firmy Texas Instruments TMS320C6711 oraz porównanie teoretycznych charakterystyk filtrów z ich praktyczną realizacją
Development of idea of surface recombination in analysis of bipolar-charge transport in metal-dielectric-metal system with thick dielectric.
Get PDFIn this model system there is presented t,he electric conduction with three mobilities of carriers where the surface traps exist. The free electrons and holes as well as the trapped electrons form the space charge in the dielectric. The transient state is examined for the different effects of the injection of carriers. There are determined the functions j(t) and qs(t) of current density and surface charge