Advanced model of electromagnetic launcher

An advanced 2D model of electromagnetic launcher is presented respecting the influence of eddy currents induced in the accelerated ferromagnetic body. The time evolution of electromagnetic field in the system, corresponding forces acting on the projectile and time evolutions of its velocity and current in the field circuit are solved numerically using own application Agros2d. The results are then processed and evaluated in Wolfram Mathematica. The methodology is illustrated with an example whose results are discussed

Induction heating of rotating nonmagnetic billet in magnetic field produced by high-parameter permanent magnets

An advanced way of induction heating of nonmagnetic billets is discussed and modeled. The billet rotates in a stationary magnetic field produced by unmoving high-parameter permanent magnets fixed on magnetic circuit of an appropriate shape. The mathematical model of the problem consisting of two coupled partial differential equations is solved numerically, in the monolithic formulation. Computations are carried out using our own code Agros2D based on a fully adaptive higher-order finite element method. The most important resultsare verified experimentally on our own laboratory device

Visokofrekvencijski interferencijski signali generirani u sustavima s PWM izmjenjivačima, dugačkim kabelima i asinkronim motorima

The operation of inverter-fed asynchronous motor drives is inherently accompanied by high-frequency interferences caused particularly by parasitic currents of the common and differential modes. These emissions propagated by conduction and radiation may unfavourably affect the operation of nearby telecommunication and signal cables and various low-current devices. The paper deals with an analysis of these phenomena based on theoretical considerations and results of special measurements of the common and differential mode disturbances. Evaluated are mainly the frequency characteristics of selected parts of the system and their contributions to the resultant harmonic spectra.Pri radu asinkronih izmjeničnih motora napajanih iz statičkih izmjenivača pojavljuju se visokofrekvencijski interferencijski signali koji su posljedica parazitnih struja između faza i parazitnih struja prema zajedničkoj točki. Ovi interferencijski signali mogu nepoželjno utjecati na rad obližnjih telekomunikacijskih i signalnih kabela i raznih elektroničkih uređaja. Ove se pojave u članku analiziraju teoretskim razmatranjima, koja su potkrijepljena eksperimentalnim rezultatima specijalnih mjerenja smetnji izazvanih parazitnim strujama. Evaluirane su uglavnom frekvencijske karakteristike odabranih dijelova sustava i njihov doprinos ukupnom harmonijskom spektru

Static characteristic of components of controllable thermoelastic actuator

The paper deals with one of the basic conditions of practical employment of finely controllable thermoelastic actuators – problems of the static characteristics of its individual structural parts. It contains the formulation of the principle of such thermoelastic actuators, description of its components (a dilatation element heated by induction, auxiliary electromagnetic actuators, and self-locking friction clutches) and their mathematical models. Briefly discussed are also their corresponding computer models making use of the finite element method. The crucial point of the work consists in the presentation of the results – static characteristics of the considered structural parts of the controlled thermoelastic actuators

Integral computation of magnetic field of shielded three-phase line

The paper deals with numerical modeling of a three-phase harmonic-current carrying shielded line. In most similar cases, computation of magnetic field and other associated quantities is realized using the finite element method that is effective, reliable and the results obtained correspond to the physical reality. Nevertheless, the method may become problematic when particular subregions (conductors, insulation, shielding elements) are geometrically incommensurable, which is even the case of thin shielding shells. That is why the authors use the integral approach for modeling of the relevant effects. Presented is its basic continuous mathematical model that is solved numerically. The theoretical analysis is supplemented with a typical example

Models of reliability prediction of electric machine taking into account the state of major structural units

It is shown that conventional mathematical models for calculation of the reliability of electric machine structural units, based on the theory of planning an experiment, do not take into account the peculiarities of their properties variation during the process of manufacture and long-term operation. Taking into consideration the multiple factors of the assigned problem, the prospect of the use of fuzzy logic postulates in the creation of models for calculation of reliability is substantiated. An approach to such models building is formed

Visokofrekvencijski interferencijski signali generirani u sustavima s PWM izmjenjivačima, dugačkim kabelima i asinkronim motorima

The operation of inverter-fed asynchronous motor drives is inherently accompanied by high-frequency interferences caused particularly by parasitic currents of the common and differential modes. These emissions propagated by conduction and radiation may unfavourably affect the operation of nearby telecommunication and signal cables and various low-current devices. The paper deals with an analysis of these phenomena based on theoretical considerations and results of special measurements of the common and differential mode disturbances. Evaluated are mainly the frequency characteristics of selected parts of the system and their contributions to the resultant harmonic spectra.Pri radu asinkronih izmjeničnih motora napajanih iz statičkih izmjenivača pojavljuju se visokofrekvencijski interferencijski signali koji su posljedica parazitnih struja između faza i parazitnih struja prema zajedničkoj točki. Ovi interferencijski signali mogu nepoželjno utjecati na rad obližnjih telekomunikacijskih i signalnih kabela i raznih elektroničkih uređaja. Ove se pojave u članku analiziraju teoretskim razmatranjima, koja su potkrijepljena eksperimentalnim rezultatima specijalnih mjerenja smetnji izazvanih parazitnim strujama. Evaluirane su uglavnom frekvencijske karakteristike odabranih dijelova sustava i njihov doprinos ukupnom harmonijskom spektru