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This paper presents some aspects on measurements of radiated emission from a Laptop. The used Standards are presented and discussed. The measurements were carried out in a Semi-Anechoic Chamber (SAC) in accordance with EN 55022 (CISPR 22) Standard. The test arrangement was in accordance with IEC 61000-4-3 Standard and the following equipment was included: reception antenna, signal generator and emission...
This paper presents a shielding effectiveness evaluation for some metallic threads materials. The tests were performed using a non-standardized method in a dual transversal electromagnetic cell (DTEM). The materials' shielding characteristics must be properly evaluated in order to choose an appropriate shielding material. The tests were conducted for three different types of material designated for...
Single phase currents and voltages were acquired from the primary winding of a locomotive transformer. Four operating regimes were considered (acceleration, running at constant speed, normal and respectively regenerative braking). 6 data sets consisting of 3 consecutive periods were considered as representative for this study and analyzed: one per each of the first 3 mentioned operating regimes and...
The paper is focused on finding appropriate and systematic procedures of denoising highly distorted small currents with significant “signal to noise” ratios and on evaluating the denoising effects over the power quality (PQ) indices. Real currents were acquired from 2 consumers placed in a small industrial hall with highly variable power consumptions. Denoising procedures relying on wavelet based...
The paper deals with the behavior of a medium / low voltage transformer (MV/LV), for a non-sinusoidal consumer placed in the transformer's secondary winding. The analysis is performed using the Discrete Wavelet Transform (DWT). The monitoring is realized with two data acquisition systems, briefly described in the paper. Problems associated to the conducted and radiated emissions are addressed and...
The paper is focused on finding appropriate procedures of denoising electrical signals (SN) acquired from the secondary winding of the excitation transformer in a large power group and evaluating their benefits. The signals were affected by white Gaussian noise with relatively high Signal to Noise ratios. The currents have significant harmonic contents (total harmonic distortions exceeding 25%). Two...
The paper deals with the design of an electric locomotive drive system used in electric railway transportation. The drive system consists of an induction motor and a voltage source inverter. A dedicated induction motor design algorithm is developed, in order to improve the motor efficiency. The design of the induction motor was realized with MathCAD and validated with Matlab Simulink. In the second...
The capabilities related to active filtering of the Stationary Wavelet Transform — SWT were evaluated considering 3 Daubechy wavelet mothers. Firstly a study on errors was performed on synthetic waveforms. The waveforms were obtained from sinusoids polluted by single harmonics with orders from the range 3…40 and magnitudes, respectively phase differences varied in a systematic manner. The differences...
The design process of a rectangular waveguide pyramidal horn antenna is carried out. A mathematical design algorithm is developed and implemented in Matlab. The antenna model is built afterwards, accounting for the same computed parameters, with two different dedicated antenna design and simulation software packages: CST Microwave Studio and ANSYS HFSS. Both are based on the Finite Element Method...
The paper deals with a series of issues relative to power quality in drive systems and the behavior of a load composed from a uncontrolled rectifier, chopper and a DC motor. A MATLAB-Simulink scheme was designed in order to study the possibility to eliminate the unwanted power-related effects from the system. An equipment having the role of active filter is modeled and studied. The active filter is...
The paper is concerned with the behavior of a transformer used to supply the excitation from a power group. Waveforms from the transformer secondary winding were recorded and analyzed. Numerical simulations were performed in order to evaluate the performances of different solutions for the improvement of transformer operation by means of diminishing the current and voltage harmonics. Passive filtering...
Computational techniques conceived to improve the efficiency of PQ analysis of quasi-stationary signals acquired from the secondary winding of the excitation transformer in a power plant are addressed. Signals of 30 periods (SN) were analyzed. SN were polluted by white Gaussian noise and "arithmetic average" signals (AS) of one period length were computed for 2 reasons: (a) simpler noise...
The paper is concerned with aspects related to the reactive power compensation capacitors influence over the current and voltage distortions. This work aims to discover if the use of capacitors for the reactive power compensation have more drawbacks than positive effects. A solution of compensation is modeled and simulated in the MATLAB/Simulink software environment. The compensation algorithm is...
The paper aims to analyze the effects introduced by additional equipment and consumers (AEC) over power quality indices in electric substations and general internal services from a Romanian power plant which uses solid fuel combustion. AEC includes asynchronous motors, rectifiers and frequency converters, introduced for environment protection. The measurement points are presented. Some of the most...
Special preprocessing techniques for denoising quasi-stationary signals (SN) acquired from the secondary winding of the excitation transformer in a power plant are addressed. Sequences of 30 periods were analyzed. SN were polluted by white Gaussian noise and “average” signals (AS) of one period length were deduced. Because vectors of samples were handled, corrective measures (CM) were applied firstly...
This paper presents a study of electromagnetic shielding materials for frequency range under 1 GHz. Optimal shielding materials will be achieved taking into consideration the quality of the shielding effectiveness, the frequency range where attenuation occurs, the costs of production for achieving the shielding material and the costs for achieving the shielding itself. The new materials have the capacity...
A complex data acquisition system used in the monitoring and diagnosis of an entire large power group delivering electric power in a power system is presented. The tests are performed with three independent synchronized data acquisition systems able to acquire up to 24 electrical quantities. The hardware and software solutions are described. Considerations on the preprocessing of data and preliminary...
The results of the measurements concerning the electric quantities from an auxiliary generator, a three-phase rectifier controlled by thyristors, and a main generator from a power group, performed using an integrated measuring system are presented. The modality to determine the power quality parameters is detailed. The analysis allows the detection of possible undesired distorting regimes, with serious...
This paper presents some considerations on designing and simulating permanent magnet motors with AlNiCo magnets. The design parameters of the motor considered during the simulations, along with the equation describing the motion and equations describing the involved electric model are presented. Finite Element Method Magnetics (FEMM) was used to make a bidimensional magnetostatic simulation of the...
The paper deals with the analysis using Wavelet Packet Transform (WPT) and Fast Fourier Transform (FFT) of synthetically generated signals. The signals are initially sine waves of 10 periods with linearly decreasing/increasing magnitude M. M varies according to a constant slope G. The studied absolute difference between the final and initial values of M belongs to the set {2,5, 5, 7.5 and 10}% from...
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