EPQU Journal Volume 11 Issue 2

Leszek S. CZARNECKI

The paper summarizes the present state of discussions on power phenomena, power definitions and compensation in single-phase linear circuits. The main concepts developed over several decades on how various non-active powers in circuits with nonsinusoidal voltages and currents should be defined and compensated are presented along with a detailed discussion of these concepts. The paper presents also the concept of the single-phase load current decomposition into Currents’ Physical Components (CPC) and its application for power definitions and compensation in such circuits. The paper is not addressed to scientists and experts on powers, but rather to common electrical engineers that sometimes face power related problems in nonsinusoidal systems.

In this paper the external magnetic stray field is investigated in transformers realized on gapped toroids with a rectangular cross section. An analytical method is used in which the field distribution is calculated by means of orthogonal expansion. As a conclusion it is shown that optimum EMC design for the case of a flyback converter is given by the results for a simple inductor. In case of a load resonant converter minimum parasitic induction is obtained, if the winding conducting maximum current is located exactly above the air gap. The second winding has to be located as close as possible to the first one with respect to the desired value of the total leakage inductance.

Irena KOVÁČOVÁ, Ján KAŇUCH, Dobroslav KOVÁČ

This paper deals with construction design of DC permanent magnet disc motor by classical calculation method and its verifying by computer finite element simulation method. The paper deals also with the computer analysis of the electromagnetic compatibility (EMC) problems focused to the area of electrical machines, which can also disclose the startling facts concerning. A problem of interference between electric motor and surroundings space caused by electromagnetic field radiation is discussed too.

Reinhard DOEBBELIN, Thoralf WINKLER, Andreas LINDEMANN

Resulting from the connection between the change rate of a magnetic field and the induced currents in an exposed hu­man body, pulsating magnetic fields have to be evalu­ated analysing the waveforms of the field or the field-generating current. A corresponding assessment guideline is given in the German safety regu­lation on “Electromagnetic Fields” BGV B11. Considering the specific output current waveforms of resistance welding installa­tions, in the paper appropriate procedures to determine the waveform-dependent exposure limits are explained by the examples of an a.c. resistance welding machine and a resistance welding inverter. Based on investigations of the field distribution the occurring actual flux density values are compared to the ascertained exposure limits and a practical method to de­termine minimum distances ensuring compliance with the given regulations is shown.

Artur KNITTER, Jarosław ŁUSZCZ, Piotr J. CHRZAN

In this paper effectiveness of spread spectrum modulation techniques to the electromagnetic interference (EMI) suppression is investigated. Comparative evaluation of spread spectrum methods is reviewed and demonstrated with the aid of function generator and EMI receiver. Obtained results indicate advantageous features of random carrier frequency modulation (CFM), which results in more steady spectral distribution. For a switch mode dc-dc converter, random and periodical sinusoidal CFM is systematically tested. Based on disturbance voltage measurements using Line Impedance Stabilization Network (LISN) and EMI receiver, conducted emission spectra are evaluated in function of the defined randomness index R and frequency range. For the acceptable range of R variations up the 20dB EMI suppression level was reached.

Stephan SCHUH, Manfred ALBACH

The integration of passive components in printed circuit boards by using structured layers of different material leads to completely new technical challenges, both in technological realisations and in simulations or modelling of the embedded components. The integration of inductive components is very interesting due to the substantial place reduction on the surface of the printed circuit board. In this context the shielding of the stray field of these inductive components leads to some new approaches in magnetic field calculation and simulation by planar structures. So in this paper the influence of FPC foils (Ferrite Polymer Compounds), -metal and thin layers of copper on the magnetic field distribution and thus on the inductive coupling mechanisms in multilayers is analytically calculated and verified by some measurements. The presented results – measurement and simulation – lead to the final conclusion that the integration of μ-metal in comparison to FPC foils and thin layers of copper in the multilayer is one of the promising procedures for EMC-shielding.

Elżbieta SZYCHTA

The article presents properties of multiresonant voltage-increasing converter to be applied in DC voltage supply systems. The configuration of the system elements enables application of the technique of zero voltage switching (ZVS) of semi-conductor elements, which yields high operating frequencies of the system while maintaining high energy efficiency and reliability of operation. Results of simulation tests of the converter, based on Simplorer, are discussed. Regulation characteristics are presented and the converter’s efficiency is determined.

Q.C. ZHONG, L. HOBSON, M.G. JAYNE

In this paper, the classical control techniques are applied to the neutral point in a 3-phase 4-wire DC-AC power converter. The converter is intended to be connected to 3-phase 4-wire loads and/or the power grid. The neutral point can be steadily regulated by a simple controller, involving in voltage and current feedback, even when the three-phase converter system (mostly, the load) is extremely unbalanced. The achievable performance is analyzed quantitatively and the parameters of the neutral leg are determined. Simulations show that the proposed theory is very effective.

Three-leg active power filter topology is the cost effective solution implementing a four-wire active power filter but it has some disadvantages compared to four-leg topology. The lack of a neutral wire filter inductor results in larger filter losses and therefore the efficiency of the topology is impaired. The neutral wire filter inductor is typically used with the four-leg four-wire active power filter topology and significantly reduces switching frequency current ripple. In this paper the suitability of a neutral wire filter inductor for the three-leg topology is studied. The performance of three-leg topology with a neutral wire filter inductor is studied through computer simulations and laboratory tests. The results indicate that the use of the neutral wire filter inductor clearly improves the performance of three-leg topology.

Andrzej SZROMBA

The aim of the paper is to demonstrate how to use sampled method of control of a shunt active power filter to maintain invariable power of a supplying voltage source, even though the supplied load varies randomly. The definition by S. Fryze of load current components is used as a basis for the construction of a family of shunt active power filters. The under discussion family of filters is designed to work synchronically with a time period T. The period T may be regulated in some range. The distinctive property of these filters is maintaining non-deformed source current in every one individually considered period T.

Main features of the family of filters are described in the first part of the paper, which is devoted to DC circuit. Then in the second part, the results, which are obtained in DC circuit, are implemented to a single- and then to a three-phase circuit. Additionally, some new features, which may be applied only for AC circuit, are discussed in the second part. All the presented waveforms are obtained using computer simulation tools.

Energy saving is an important factor of economic growth and effectiveness growth of national economy. Solving the problem of energy saving is possible when improving a variable speed electric drive based on induction motors which should be designed and manufactured for special energy saving technologies. New approach to induction motor design taken into account service condition is required. Energetic characteristic increase is a determining factor. In this factor energy saving effectiveness evaluation mathematical model has been presented. The possibility of improvement of the induction motor without cross section geometry changing has been considered on the proposed model basis

The paper deals with the update studies on Power Quality for electric traction systems. Probabilistic methods of analysis are presented both for the supply lines and the rolling stocks. Simulation software tools are created for disturbance propagation studies and examples of application are reported with reference to the Italian railway case.

The electric high speed railway loads supplied by the three phase power system represent one of the main sources of voltage unbalance perturbation in the grid. The power system configuration and the load conditions influence the degree of this power quality perturbation. The present paper deals with the problems raised by the practical determination of the voltage unbalance factor in conformity with the European and IEEE standards. The procedure for identifying a vulnerability area in which the voltage unbalance presents values that exceed the standard limits is elaborated and comparison on the use of the two mentioned set of standards is performed. A case study referred to the 63 buses CIGRE network analyzed in the paper gives rise to interesting comments and discussion.