Communications - Scientific Letters of the University of Zilina, 2011 (vol. 13), issue 2A
Articles
Combined Forward-Flyback-Converter with Only Two Diodes - Function and Modelling
Felix A. Himmelstoss, Helmut L. Votzi
Communications - Scientific Letters of the University of Zilina 2011, 13(11):6-12 | DOI: 10.26552/com.C.2011.2A.6-12 
A combined forward and flyback converter with a simple two windings transformer, an inductor, an active switch, two diodes and a buffer capacitor is explained. The voltage transfer ratio and the demagnetizing condition are derived. The voltage transfer ratio of the new converter is significantly higher compared to the forward and the flyback converters. The converter is useful for applications where a flyback converter is too small and a forward converter with its complicate transformer is too expensive. By shunting the two diodes by a third one the efficiency can be increased and due to the reduced losses the cooling is easier. The state space equations...
Protocols Performance in Next Generation Networks
Asimakis Lykourgiotis, Stavros Kotsopoulos
Communications - Scientific Letters of the University of Zilina 2011, 13(11):13-18 | DOI: 10.26552/com.C.2011.2A.13-18
Next Generation Network (NGN) is a packet-based network integrating legacy networks and providing ''anywhere, anytime and on any device'' ubiquitous services. One of the prerequisites of NGN is to support generalized mobility making Mobility Management (MM) a crucial factor towards a seamless provision of multimedia applications. A very promising scenario is the design and implementation of a UMTS / WLAN interworking architecture. In literature a variety of MM protocols operating from different layers of the protocol stack have been proposed. Nevertheless, the comparison of them has been less extensive mainly narrowed between extensions of the same...
Induction Heating of Very Thin Metal Plates Modelled by Electric Vector Potential
Ivo Dolezel, Bohus Ulrych
Communications - Scientific Letters of the University of Zilina 2011, 13(11):19-24 | DOI: 10.26552/com.C.2011.2A.19-24
A novel way of modelling of induction heating of very thin nonferromagnetic plates exposed by periodically varying magnetic flux is presented. The currents induced in the plate are described by means of the T-electric vector potential. The mathematical model is solved numerically, by a code developed and written by the authors. The methodology is illustrated with an example whose results are discussed.
Choosing Modulation Strategies for 2-Stage Combine LLC- and Direct Converter-Modelling, Simulation, Application
Branislav Dobrucky, Mariana Benova, Michal Frivaldsky, Michal Prazenica
Communications - Scientific Letters of the University of Zilina 2011, 13(11):25-31 | DOI: 10.26552/com.C.2011.2A.25-31
The paper deals with design of switching and control strategy of 2-stage combine LLC- and matrix converter, supplied from DC voltage source. It also deals with comparison of the four different switching control modes: phase-mode control, sinusoidal PWM mode control, pulsedepletion mode control and packet-mode control. Numerical harmonic analysis for total harmonic distortion is used. Simulation and preliminary results of experimental verification are given in the paper.
Simulation Based Method for Design and Application of Digital Control System
Peter Drgona, Anna Prikopova, Michal Frivaldsky, Martin Priecinsky
Communications - Scientific Letters of the University of Zilina 2011, 13(11):32-37 | DOI: 10.26552/com.C.2011.2A.32-37
With increasing number of microprocessors and DSP use as a control system in power semiconductor converters, the new approaches for design of digital control system must be implemented. Designing a digital control system requires use of control to output transfer function. For new, frequency controlled resonant converters, like LLC converter, standard averaging methods cannot be applied for revealing the transfer function. Instead of that, new simulation based, numerical methods must be employed.
The Investigation of Terminal Segment Effect on Blood Pressure Propagation Patterns in Cardiovascular System Models
Daniela Gombarska, Barbora Czippelova, Ivo Cap
Communications - Scientific Letters of the University of Zilina 2011, 13(11):38-43 | DOI: 10.26552/com.C.2011.2A.38-43
The electro-mechanical analogy method is used for the simulation of blood flow in blood vessels. Particularly the subject of this paper is the investigation of the influence of terminal segment topology on the blood pressure propagation patterns. The cardiovascular system is widely branched and therefore very complex. Thus, it is impractical to create the simulation model consisting of all blood vessels and attention is focused to development of models for smaller parts of vascular system. The selection and adjustment of terminal segments for such simulation model is important on behalf of the model accuracy. Three different types of terminal segments...
Simulation of a Power Substation's Control System Operation
Marek Hoger, Peter Bracinik, Marek Roch
Communications - Scientific Letters of the University of Zilina 2011, 13(11):44-48 | DOI: 10.26552/com.C.2011.2A.44-48
This paper describes a simulator of power substation automation system developed as part of software suit for complex simulation of power substation operation. This software simulates behavior of a distributed control system built from a group of interconnected and cooperating intelligent electronic devices. The basic structure and communication principles are derived from standard IEC 61850.
Converter with Synchronous Rectifiers for Electroplating
Peter Hurtuk, Martin Priecinsky, Anna Kondelova
Communications - Scientific Letters of the University of Zilina 2011, 13(11):49-54 | DOI: 10.26552/com.C.2011.2A.49-54
This paper presents the requirements for resources for electroplating processes, principles of the synchronous rectifier and its control. It describes simulation and experimental verification of the synchronous rectifier, compares the efficiency of switching power supply using a synchronous rectifier and a diode rectifier, where body diode of MOSFET transistor is used for rectification. Finally the paper brings thermal images of synchronous rectifier transistors.
Uncertainty in Depth Evaluation of Partially Conductive Cracks from Eddy Current Testing Signals
Ladislav Janousek, Milan Smetana
Communications - Scientific Letters of the University of Zilina 2011, 13(11):55-60 | DOI: 10.26552/com.C.2011.2A.55-60
The paper deals with eddy current non-destructive evaluation of partially conductive cracks. Especially, uncertainty of a depth estimation of such cracks from eddy current testing signals is considered here. A plate specimen having the electromagnetic parameters of a stainless steel SUS316L is inspected in this study by numerical means. A crack with variable depth, width and conductivity is positioned in the middle of the plate. One of the most utilized eddy current probes so called pancake probe is employed for the inspection. Response signals of the crack with different parameters are numerically calculated and further analysed. Presented results...
Numerical Studies of Optical Bistability of Absorptive Type
Eliska Jurisova, Jarmila Mullerova
Communications - Scientific Letters of the University of Zilina 2011, 13(11):61-66 | DOI: 10.26552/com.C.2011.2A.61-66
Theoretical analysis is presented to search for the purely absorptive optical bistability in a Fabry-Perot cavity filled with a saturable absorber. A simple model of singlet absorption is used on numerically solving the relationships between the input and output light fields. The proposed model corresponds well to organic compounds considered as novel optical materials with third-order optical nonlinearities. The effects of saturable absorber parameters on the output light characteristics are studied and purely absorptive optical bistabilities are shown numerically to search for bistable behaviour. The simulated results are indications for promising...
Verification of Operation Modes of Designed LLC Resonant Converter
Pavol Spanik, Jozef Kandrac, Michal Frivaldsky, Peter Drgona
Communications - Scientific Letters of the University of Zilina 2011, 13(11):67-73 | DOI: 10.26552/com.C.2011.2A.67-73
This paper describes the design of the LLC resonant converter, which is done by means of fundamental harmonic approximation (FHA). Output power of proposed converter is 1kW with output voltage 48 V at switching frequency of 500 kHz. Performance of converter at different operational conditions was verified through simulation analysis by utilization of OrCAD PSpice software. The simulation results of multiple parametrical experiments were obtained and consequently evaluated into graphical interpretation of efficiency of proposed converter.
Passive Electronic Componets Parameters Searching with Differential Evolutionary Algorithm
Juraj Palecek, Martin Vestenicky
Communications - Scientific Letters of the University of Zilina 2011, 13(11):74-78 | DOI: 10.26552/com.C.2011.2A.74-78
This paper describes computing of inductor parameters as passive electronic component with algorithm of differential evolution. Computing of parameters is based on substitute model of inductor which is described with three basic parameters such as resistance, inductance and capacitance. Measured frequency response of complex impedance of the real inductor is input parameter to the iterative loop driven by the differential evolution algorithm. There are three output parameters of the algorithm, where resistance value is considered to be a combination of DC coil resistance and skin effect influence, second value describes inductance of a real inductor...
Increase Safety of Traffic Control on the Minor Railway-Tracks
Jan Slezak, Juraj Spalek
Communications - Scientific Letters of the University of Zilina 2011, 13(11):79-82 | DOI: 10.26552/com.C.2011.2A.79-82
The paper aims at detecting the existing safety risks on the minor railway-tracks being operated in accordance with the provision CD-D3 of the Czech Railways, and at providing the solutions and technologies suitable for the mentioned minor railway-tracks. These tracks are currently equipped with out of date safety related systems monitoring the railway, whose operation depends purely on human factor. The latest railway accidents were reported just on these low traffic frequency tracks.
Artificial Heart Valve Inspection Using Eddy Current Techniques
Tatiana Strapacova, Klara Capova, Ladislav Janousek
Communications - Scientific Letters of the University of Zilina 2011, 13(11):83-86 | DOI: 10.26552/com.C.2011.2A.83-86
This paper discusses about minimally invasive techniques to detect the single leg fracture in special type of artificial heart valve called Bjork Shiley Convexo - Concave (BSCC). The fracture affects the outlet strut of these artificial heart valve and it is needed to detect it. For this purpose the electromagnetic methods based on eddy current testing were used. The coils are excited in the selected range of the frequencies for identification of the fractures in the outlet strut. The fractures occurring in BSCC heart valve and their numerical simulations are described. The results obtained with a prototype setup are presented and they demonstrate...
The Measuring System for Evaluation of Parameters of Integrated Mach-Zehnder Modulator
Jiri Svarny
Communications - Scientific Letters of the University of Zilina 2011, 13(11):87-91 | DOI: 10.26552/com.C.2011.2A.87-91
The paper deals with some issues linked to practical application of the analog intensity electro-optic modulator of Mach-Zehnder type. An accurate adjustment and long-term stabilization of optimal operating point of the modulator belongs to the most severe problems linked to implementation of the appliance like this. The paper describes functionality of Mach-Zehnder modulator, highlights some of the problems the designer is faced to and presents the methodology that has been used to measure parameters of the modulator that are not specified in the manufacturer data-sheet and might be helpful to solve the problem.
LPG Concentration Measurement in Vehicles Transporting Dangerous Goods
Martin Vestenicky, Peter Vestenicky
Communications - Scientific Letters of the University of Zilina 2011, 13(11):92-96 | DOI: 10.26552/com.C.2011.2A.92-96
This paper describes the design of intelligent sensor unit for LPG (Liquefied Petroleum Gas) concentration measurement in the air. The sensor unit is a part of sensor network which has been designed for vehicles transporting dangerous goods. The described sensor unit uses sensor element based on SnO2 structure which is vapoured on the aluminum substrate. Main part of the paper is focused on hardware solution of the sensor unit, signal processing applied on signal from its sensor element, compensation of air temperature and relative humidity influence on the sensor resistance and description of its application layer communication protocol.
MRAS Based Sensorless and Sensor Vector Control and Smooth Transient Between Them
Jakub Vonkomer, Milan Zalman
Communications - Scientific Letters of the University of Zilina 2011, 13(11):97-103 | DOI: 10.26552/com.C.2011.2A.97-103
Dynamic control, like vector control is an essential feature of every modern AC drive. In some cases it might be very important to provide continuous operation in case of encoder failure. It further means that the transient between sensor vector control and sensorless vector control has to be smooth. To obtain that a modified vector and sensorless vector control algorithms were designed. To allow smooth transitions, both sensor and sensorless control share common flux model. In this paper a novel robust MRAS-based speed estimator based on error between current estimators output and measured current and modifications of direct sensor vector control...
Safety of Railway Systems and Formal/Semiformal Methods
Milan Slivka
Communications - Scientific Letters of the University of Zilina 2011, 13(11):104-108 | DOI: 10.26552/com.C.2011.2A.104-108
The contribution deals with computer based railway safety systems. It shortly concerns problems associated with using computer systems in comparison with traditional safety systems. The attention is paid to formal and semiformal methods in development and approval of railways systems, seen in the context of standardization and legislation framework. The author summarizes current state of using formal and semiformal methods from whole life cycle point of view of railway safety system in the area of Slovak and Czech railways and possible reasons for their rare use.
Photovoltaics in Present Days and Their Coexistence with Power System
Jan Turcek, Matej Hrasko, Juraj Altus
Communications - Scientific Letters of the University of Zilina 2011, 13(11):109-113 | DOI: 10.26552/com.C.2011.2A.109-113
The article deals with the issue of presentation of photovoltaic power and photovoltaic power plants, describes their main features, their advantages and disadvantages, and also deals with the possible massive deployment of these power sources to the power system and their impacts on power system operation.
The First Application of The Electrodynamic Wagon Retarder in Poland
Jerzy Mikulski, Jakub Mlynczak
Communications - Scientific Letters of the University of Zilina 2011, 13(11):114-118 | DOI: 10.26552/com.C.2011.2A.114-118
The article discusses design and installation method of the EDG Electrodynamic Wagon Retarder at the railway siding of the Power Plant Rybnik. It is the first structure of its kind in Poland. Up to now mostly hydraulic brakes have been used in Poland. They were difficult to operate and hardly environmentally friendly due to contamination and noise. Electrodynamic wagon retarders are free from such defects. The issue of introducing new railroad brake construction in Poland is very important because the Polish Railway Lines (PLK) are confronted with the need of devices modernization on a humps. The German railways' experience confirms the effectiveness...