ACTA TECHNICA CSAV |

The paper presents an algorithm for numerical computation of surge phenomena on a one-phase overhead or cable line with distributed parameters that consists of n uniform parts. The algorithm was tested on a number of examples, in common with the stability and convergence of solution. The described method can be used for calculation of the overvoltage that may occur in the course of feeding transformers or AC rotating machines by voltage containing steep pulses.

The paper discusses conceptual questions of modelling and optimizing of quality providing processes.

The conception of a multiple input voltage operational amplifier (MIOA) is presented in common with its applications in voltage amplifier circuits with digitally tuned amplification. The general structure of a sinusoidal oscillator with one MIOA and digitally tuned parameters such as frequency of oscillation is described. Two versions of the sinusoidal oscillator, one with RLC elements and the other with RC elements are shown. Simulations of generated oscillations representing output voltages of the amplifier have been carried out by means of program SPICE. Investigated was also the influence of tuning its amplification based on the mentioned waveforms.

The work is focused on a three-level inverter with capture diodes. The problem to be solved is to divide a uniform voltage on an input capacitance divider. The currents of the divider are derived in dependence on inverter switching. The aim is to propose a voltage dividing control of the capacitance divider.

The paper presents a finite element model of mass transport and electrochemistry in a polymer electrolyte fuel cell at a constant temperature. Derived is a model of transport of the gases in the interdigitated gas distributor and porous layer based on Maxwell-Stefan equations in common with consequent computation of current density and electric potential distribution. The two-dimensional nature of gas transport within the fuel cell is discussed and plots of gas mole fraction and water contents are presented. The model is illustrated on an example.

A new type of passive tuned liquid damper (TLD), which relies on the motion of liquid inside a movable rectangular tank with two degrees of freedom (horizontal displacement and rotation) is investigated, including the influence of vessel's horizontal motion and rotation on the damping of vertical and horizontal vibrations of footbridges. Experimental solution consists in determining the magnitude of the excitation force of the shaking table, required under resonance during harmonic excitation of the vessel, the dimensions of which correspond with the dimensions of the girder of the footbridge. The effectiveness of TLD is determined by the ratio of the excitation force required for the liquid-filled tank harmonic motion and the excitation force needed for harmonic motion of an empty tank.

The paper deals with the problem of electromagnetic field analysis for spherical electromechanical converters, taking into account magnetic anisotropy in analytical way. The electromagnetic field is evaluated analytically with the help of separation method for magnetic vector potential. The electromagnetic torque and power losses are also calculated analytically. The results obtained can be used as test tasks for both electromagnetic field numerical analysis and torque calculation.