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Hard-coupled model of local direct resistance heating of thin sheets
Karban, P. ; Mach, F. ; Doležel, Ivo
A monolithic model of local direct resistance heating of thin sheets is presented. The model respects all nonlinearities of the system such as the temperature dependencies of physical properties of individual parts of the system. Numerical computations are performed by a finite element method of higher order of accuracy and realized by our own codes Hermes2D and Agros2D. The methodology is illustrated by a typical example whose results are discussed.
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Transient Behavior of Active Front-End Rectifier under Unbalanced Voltage Supply
Chomát, Miroslav ; Schreier, Luděk ; Bendl, Jiří
Operation of voltage-source inverter supplied with unbalanced system of voltages is investigated in the paper. This situation can lead to problems in operation of an electric drive as voltage pulsations can arise in the DC-bus. Suitable kontrol methods may be applied to eliminate this effect in the aktive front-end rectifier. The paper particularly focuses on transient processes that accompany operation of the drive. They can be caused by changes in control of the drive, changes in load, or changes in the supply voltages.
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Influence of Third Space Harmonic on Properties of Five-Phase Induction Machine
Schreier, Luděk ; Chomát, Miroslav ; Bendl, Jiří
The paper deals with the necessity to consider higher space harmonic waves of a current layer, magnetic flux density and yoke flux in a five-phase induction motor fed from a tenpulse frequency converter. It is shown that especially the third space harmonic influences currents and torque of the machina considerably. The influence depends on connection arrangements of the converter and stator of the five-phase induction machine. Theoretical results are verified by experimental measurements.
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New Hybrid Power Filter Topology and Control for Application in Industrial Networks
Pecha, I. ; Šimek, Petr ; Škramlík, Jiří ; Valouch, Viktor
The paper presents the new structure and control strategy of the Hybrid Power filter (HPF) with a split passive part. Its impedance is divided into two parts tuned to 50Hz and 250 Hz. The HPF topology is very efficient to mitigate harmonic currents especially for higher frequencies. The HPF functionality is influenced by the grid inductance changes only negligibly. The new HPF characteristics were compared with those for a standard HPF and a classic passive compensation by the simulation done in the Matlab/Simulink environment. The voltage and current values and their harmonic spectra were also measured in the real industrial plant Remarkplast, Ltd. under different conditions.
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Measurement on Five-Phase IM Fed from Ten-Pulse Frequency Converter
Chomát, Miroslav ; Schreier, Luděk ; Bendl, Jiří
The mathematical model of a five-phase induction machine derived based on the theory of space vectors and symmetrical components was verified by means of comparison of simulation and experimental results. A multi-phase voltage source inverter was used to feed an experimental five-phase induction machine by ten-pulse voltage supply of constant frequency in different connection arrangements. Steady state operation was considered. The good agreement between the simulation and experimental results has proved the correct function of the mathematical and numerical model used.
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Volumetric Velocimetry and Accelerometry of Injected Particles in Thermal Plasma Jet
Šonský, Jiří
Measurements of the injected particles velocities and accelerations in the plasma jet are important for thermal plasma spraying technology improvement. Commonly used methods of optical diagnostic, such as particle image velocimetry (PIV) or particle tracking velocimetry and accelerometry (PTVA),are complicated due to strong optical self-emission of the plasma jet. We have developed 3-D variant of the PTVA, able to measure particle velocities and accelerations in hot core of the thermal plasma jet, as well as in surrouding areas, such as entrance of particle flow into the plasma jet.
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