Ústav výkonové elektrotechniky a elektroniky


Recent Submissions

Now showing 1 - 5 of 21
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    TRIZ already 35 years in the Czech Republic
    (Elsevier B.V., 2016-02-10) Bušov, Bohuslav; Žídek, Jan; Bartlová, Milada
    In this paper the authors summarize the experience of teaching and implementation TRIZ at technical universities and findings from teaching and applications in companies in the Czech Republic and Slovakia for the last 35 years.
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    Thermal protection implementation of the contact overheadline based on bay controllers of electric transport traction substations in the mining industry
    (Saint Petersburg Minin University, 2021-10-29) Lantsev, Dmitrij; Frolov, Vladimir; Zverev, Sergej; Uhrlandt, Dirk; Valenta, Jiří
    The article presents the principle of thermal protection of the contact overheadlineand substantiates the possibility of practical implementation of this principle for rail electric transport in the mining industry. The algorithm for the implementation of modern digital protection of the contact overhead line as one of the functions of the controller is described. A mathematical model of thermal protection is proposed, which follows from the solution of the heat balance equation. The model takes into account the coefficient of the electrical networktopology, as well as the coefficient of consumption of the current-carrying core of the cable, which determines the reduction in the conducting section from contact erosion and the growth of oxide films. Corrections for air flows are introduced when receiving data from an external anemometer, via telemechanics protocol. The mathematical model was tested by writing a real thermal protection program in the C programming language for the bay controller, based on the circuitry of which is the STM32F407IGT6 microcontroller for the microcontroller unit. Verification tests were carried out on a serial bay controller in 2020. The graphs for comparing the calculated and actual values of temperatures, with different flow rates of the current-carrying conductor of the DC cable, are given. To obtain data, telemechanics protocols IEC 60870-104 and Modbus TCP, PLC Segnetics SMH4 were used.
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    Identification of Power BJT Operating Stages Based on Experimental Excess Charge Estimation
    (IEEE, 2021-05-12) Mikláš, Ján; Procházka, Petr
    The paper proposes and demonstrates an experimental waz of estimating the amount of stored charge of excess minority carriers within power BJT base and collector. This consequently allows a detailed identification of transistor operating stage. A brief device operation analysis is provided as a clear support of the measured characteristics. The method is based on determining the steadz-state stored charge at various operating conditions by integration of negative transient base current during turn-off event which deflates the stored charge. An ultimate objective of these and future experiments is an accurate interpretation and modelling of various device stages during IGBT switching process. Most of the observed phenomenons are common among a power BJT and IGBT's intrinsic BJT. As IGBT doesn't provide access to the internal base current, it is advantegous to measure and interpret the relations between stored charge and switching waveforms of power BJT first and further generalize the observations to IGBT measurements.
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    Compact High-Voltage AC Generator with Pulse Transformer for High-Frequency Irreversible Electroporation (H-FIRE)
    (MDPI, 2021-11-23) Folprecht, Martin; Červinka, Dalibor; Procházka, Petr
    This paper is focused on a design of a high-voltage (HV) generator, which is proposed for a high-frequency irreversible electroporation (H-FIRE). The generator produces bursts of bipolar symmetrical pulses. Most HV sources used for cell electroporation are based on a controlled discharge of a capacitor into a resistive load. This solution is very simple, but it is associated with a certain risk of an uncontrolled discharge of the capacitor. We present a different type of the generator, where a DC-AC inverter with pulse transformer is used and where the mentioned risk is eliminated. Our generator is able to deliver bursts with variable length from 50 to 150 s and a gap between bursts can be set from 0.5 to 1.5 s. Pulse frequency can be varied from 65 to 470 kHz and the output voltage is controlled in two ranges from 0 to 1.3 kV or from 0 to 2.5 kV. Results are presented with resistive load and with tissue impedance load.
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    Experimental model of occluded biliary metal stent recanalization using irreversible electroporation via a tubular catheter
    (Taylor & Francis, 2021-03-07) Rohan, Tomáš; Andrašína, Tomáš; Jůza, Tomáš; Matkulčík, Peter; Novotná, Veronika; Červinka, Dalibor; Bernard, Vladan; Válek, Vlastimil; Nahum Goldberg, Shraga
    Purpose To demonstrate the feasibility of irreversible electroporation (IRE) for treating biliary metal stent occlusion in an experimental liver model. Methods and materials IRE was performed using an expandable tubular IRE-catheter placed in nitinol stents in the porcine liver. A 3-electrode IRE-catheter was connected to an IRE-generator and one hundred 100 mu s pulses of constant voltage (300, 650, 1000, and 1300 V) were applied. Stent occlusion was simulated by insertion of liver tissue both ex vivo (n = 94) and in vivo in 3 pigs (n = 14). Three scenarios of the relationship between the stent, electrodes, and inserted tissue (double contact, single contact, and stent mesh contact) were studied. Electric current was measured and resistance and power calculated. Pigs were sacrificed 72 h post-procedure. Harvested samples (14 experimental, 13 controls) underwent histopathological analysis. Results IRE application was feasible at 300 and 650 V for the single and double contact setup in both ex vivo and in vivo studies. Significant differences in calculated resistance between double contact and single contact settings were observed (ex-vivo p < 0.0001, in-vivo p = 0.02; Mann-Whitney). A mild temperature increase of the surrounding liver parenchyma was noted with increasing voltage (0.9-5.9 degrees C for 300-1000 V). The extent of necrotic changes in experimental samples in vivo correlated with the measured electric current (r (2) = 0.39, p = 0.01). No complications were observed during or after the in-vivo procedure. Conclusion Endoluminal IRE using an expandable tubular catheter in simulated metal stent occlusion is feasible. The relationship of active catheter electrodes to stent ingrowth tissue can be estimated based on resistance values.