Multiconductor line with non homogeneous dielectric is modeled and analyzed. Model of the multiconductor line is presented. The finite element method and Matlab PDE Tools software were used for analysis and calculation of characteristic impedances. The program for characteristic impedance calculation was developed. Calculation results are presented and analyzed. They confirm that the finite element method and the presented program can be used for calculations of characteristic impedances of multiconductor lines with non homogeneous dielectric.

The digital protection relay for 550 kW - 1 MW asynchronous motors is investigated in this finishing work. In the theoretical chapter are examinated the structure of multifunctional protection relay, non-regular asynchronous motor operating conditions and their reasons. Two operating conditions are marked out, first - when supply current is changed, second - alternation in supply voltage. Next is made investigation of Siprotec 7SJ621 digital protection relay. There's made survey of 630 kW power asynchronous motor from non-regular operating konditions when there was overcurrent and overvoltage in the supply.

Nowadays the popularity of WLANs is growing very rapidly. The basic solution for the connection of WLAN users to the global internet network is using leased lines or the other standard data transmission networks. But there may occur situations, when the only network for the data transmission we can use for the connection to the internet, is GSM network. In such a case, we are proposing to connect the users of WAN/WLAN networks by using GSM network, which has complete coverage in the territory of Lithuania. To guarantee the sufficient data transfer rate, we use bonding of several parallel GPRS/EDGE/UMTS channels into one total channel. In such a way we increase the reliability and data transfer rate of the total mobile data transmission channel. The parallel channels are bonded into one total channel by using either the hardware (Cisco) routers, or the software routers, configured using network administration tools of Linux operating system. In this work we give all the tools and configuration settings necessary for the realization of such a system. The results of QoS characteristics measurements are given too. We measure packet delay and data transfer rate. The majority of measurements are made by using several parallel GPRS channels because of wide spread GPRS technologies. The key accent of the system is free selection of the physical layer (OSI model) of the parallel channel. So we can bond either several GPRS, or EDGE, or UMTS channels.

The research object is to develop and investigate methods and algorithms for fmleexthiboldes ,c othnetr oplr oobfl etmwso -ocfo osradviinnagt ea nddri vrea tisoynsatel mhas.n dAlipnpgl inogf edneevreglyo,p eeqdu cipomnternotl and global material resources have to be investigated in cases of two dimensional positioning and scanning processes under circumstances omaximal.

The purpose of the research is to create traffic optimal adjustment methods and algorithms based on the theory of Petri nets. To investigate the functionality of created algorithms.

DEVELOPMENT AND RESEARCH OF SPECIAL LUMINAIRE SYSTEMS Relevance of the research When Lithuania were joined into the European Community it has become necessary to use lighting devices corresponding to requirements of the European Community – ENEC norms. Taking into account the specificity of given devices in Lithuania and other new EU countries they should be steady against low temperatures, humidity, acts of vandalism, to be suitable for the illumination of industrial buildings and to fulfil the requirements of low prices of the new incorporated countries. Recently new comprehensive ENEC norms (EN European Norms, EC Electrical Certification) for luminaires were drawn up and effectively introduced by the European Union. As a result, the production of a wide range of electrical operating equipment was discontinued due to the inconsistency between technical parameters of produced equipment and new norms. Such equipments were not allowed to be marketed. Therefore it has become necessary to develop luminaires capable to fulfil the increased quality requirements of the European Union. Their development should also taken into account due to the targets of product responsibility (§ 22) laid down in the Act for Promoting Closed Substance Cycle Waste Management and Ensuring Environmentally Compatible Waste Disposal introduced in 1996 also should be taken into account extensively the aspects of ecological efficiency. In the past, plastic luminaire systems belonging to a higher... [to full text]

DEVELOPMENT AND RESEARCH OF SPECIAL LUMINAIRE SYSTEMS Relevance of the research When Lithuania were joined into the European Community it has become necessary to use lighting devices corresponding to requirements of the European Community – ENEC norms. Taking into account the specificity of given devices in Lithuania and other new EU countries they should be steady against low temperatures, humidity, acts of vandalism, to be suitable for the illumination of industrial buildings and to fulfil the requirements of low prices of the new incorporated countries. Recently new comprehensive ENEC norms (EN European Norms, EC Electrical Certification) for luminaires were drawn up and effectively introduced by the European Union. As a result, the production of a wide range of electrical operating equipment was discontinued due to the inconsistency between technical parameters of produced equipment and new norms. Such equipments were not allowed to be marketed. Therefore it has become necessary to develop luminaires capable to fulfil the increased quality requirements of the European Union. Their development should also taken into account due to the targets of product responsibility (§ 22) laid down in the Act for Promoting Closed Substance Cycle Waste Management and Ensuring Environmentally Compatible Waste Disposal introduced in 1996 also should be taken into account extensively the aspects of ecological efficiency. In the past, plastic luminaire systems belonging to a higher... [to full text]

The main purpose of this research - to investigate the mechanical and working characteristics of single - phase induction motor with asimmtrical stator. The other purpose - to evaluate single phase motor use with frequensy transformer.

Disertacijoje keliamas tikslas - sudaryti trifazio asinchroninio variklio matematinį modelį, kuris ne tik adekvačiai aprašo nesimetriškų asinchroninių variklių dinamiką, bet ir kurio greitaveika būtų didesnė už universalaus elektrodinaminio modelio greitaveiką, ši modelį pritaikyti įvairiems variklio apvijų jungimo būdams, jo pagrindu sudaryti kompiuterinius modelius dažniu valdomiems asinchroniniams varikliams tirti. Pirmajame skyriuje aptariami šiuo metu dažniausiai naudojami asinchroninių variklių modeliai, aptariami jų privalumai ir trūkumai. Nesimetriško asinchroninio variklio matematinio modelio fazinėje koordinačių sistemoje lygtys išvestos antrajame skyriuje. Trečiasis skyrius skirtas kompiuteriniams asinchroninio variklio modeliams. Sudarytas universalus, t. y. visiems variklio apvijų jungimo atvejams tinkamas, programinis asinchroninio variklio modelis. Sudarytas Simulink paketui tinkamas objektinis asinchroninio variklio modelis. Ketvirtasis skyrius skirtas valdomų elektros pavarų modeliams. Sudaryti algoritmai inverterio-variklio ir lygintuvo-inverterio-variklio sistemų imitavimui. Pateikti šių sistemų imitavimo rezultatai. Sudarytas Simulink paketui tinkamas srovės kanalo metodu valdomos dažninės pavaros modelis. Darbo pabaigoje pateiktos išvados. / The aim of dissertation is to develop mathematical and computer models of induction motor in phase coordinate system at various ways of stator windings connection, transform this model for investigation of dynamics of linear induction motor, and carry out computer models for investigation of frequency-controlled induction motors. Chapter 1 discusses mathematical models of induction motors, their advantages and shortcomings. Mathematical model of induction motor in phase coordinate system applicable to consider non-symmetry of motors is derived in Chapter 2. Chapter 3 is devoted for computer models of induction motors. Universal algorithm of programmed motor model is elaborated and presented. Objective Simulink motor model is developed. Chapter 4 is devoted for models of controlled electric drives. Algorithm to simulate system inverter-motor is carried out and results of simulation are presented. Model of system rectifier-inverter-motor with changeable structure was proposed and simulations of transients are discussed. Model of drive, controlled by current channel is developed. General conclusions of the research are made.

Kompozicinių medžiagų konstrukcijų taikymas aviacijoje didėja. Saugumui aviacijoje užtikrinti reikalingos patikimos kontrolės sistemos. Šiame darbe pateiktas ultragarso greičio matavimo metodo taikymas kompozicinėms struktūroms tirti. Metodas numato akustinių gardelių panaudojimą, sudarant ultragarso bangų sklidimo greičio matavimo kanalą tiriamame sluoksnyje. Šis metodas atitinka keliamus tikslumo, patikimumo ir operatyvumo reikalavimus. Darbo apimtis – 65 p. teksto be priedų, 44 iliustr., 3 lent., 16 bibliografiniai šaltiniai. / Usage of compositional materials in aviation increases. To ensure safety in aviation - reliable control systems are required. Method of examination of compositional materials using ultrasound measuring system is introduced in this work. This method implies usage of acoustic lattice for measurement of created ultrasound waves in examined layer. This method complies with requirements for accuracy, reliability and effectiveness.