Alimentations électriques et étude énergétique d'un générateur de jets synthétiques à plasma

Les générateurs de jets synthétiques à plasma (JSP) produisent des jets d'air à grande vitesse (induit par un plasma) permettant de réduire les turbulences provoquées par un fluide le long d'une aile d'avion. Deux structures d'alimentation ont été conçues et réalisées afin de produire la décharge dans le JSP. Ces deux alimentations dissipent l'énergie de manière totalement différente dans la décharge (pulsée pour la première et beaucoup plus lentement pour la seconde). L'alimentation pulsée produit une décharge très chaude (12 000 K), et la seconde une décharge beaucoup plus froide (2000 K). L'alimentation pulsée génère ainsi des jets de plus grande vitesse mais beaucoup plus courts que la seconde qui produit des jets peu puissants mais très longs. Cependant le calcul du rendement par différente modèles (thermique, aérodynamique) indique que l'alimentation pulsée est la plus efficace. Enfin des essais en soufflerie montrent une modification notable des écoulements sur différents profils (plaque plane, aile d'avion ...) lorsque les JSP sont actifs.Plasma Synthetic jet actuator (PSJ) produces high velocity jet reducing turbulences generated by the external flow along of airplane's wings.. In this study two power supply structures, i.e. pulsed or not, have been designed and used to produce the electric discharge in the PSJ actuator. The pulsed power supply induces a hot (12 000 K) discharge while the second one produces a non homogenous cold discharge (2000 K). It is assumed that the air within the cavity is not heated the same way producing a high velocity and short length jet in the pulsed case and a low velocity short jet in the other case. Nevertheless experimental monitoring shows that the heating of the actuator's wall is less significant using the pulsed supply. Those measurements are in adequacy with the results from efficiency modeling using two different models (thermal and aerodynamic). It is then concluded that the pulsed power supply is more effective and, for that reason was chosen for the wind tunnel tests. The results show an significant modification of the external flow on different profiles (plate, airwings ...) when PSJ are used

DBD tranformerless power supplies: impact of the parasitic capacitances on the power transfer

A new transformerless power supply for DBD application is presented here. The power supply is built with 10kV SiC MOSFET. This high voltage switches allow holding the high voltage required by the DBD. An analytical study of the converter's operation is presented to deduce the power transmitted to the DBD. A comparison between the experimental and theoretical electrical waveforms is shown. The experimental waveforms are particularly affected by all the parasitic capacitances. When all the switches are in OFF state, oscillations cause over-voltages across the switches. An analysis of the effect of each capacitance is presented and demonstrates that the parasitic capacitances of the switches and of the inductance play a key role in the actual power transfer

Parametric study of dielectric barrier discharge excimer UV lamps supplied with controlled square current pulses

A parametric study of a system dedicated to non-coherent UV emission, by means of DBD excilamps, supplied by a controlled square shape current source is proposed. The presentation highlights on the one hand the performances experimentally obtained by combining together a set of 20 different bulbs with different diameters, gap and wall thicknesses (all the bulbs have the same length and are filled with the same Xe-Cl gas mixture), with different electrical power supplying conditions: magnitude, frequency (in the 30 kHz – 200 kHz range) and duty cycle of the square shape current pulses injected into the bulb. The performances concern the average UV power, the efficiency of the bulb conversion (electrical power to UV) and the adjustability of the power. On the second hand, we present design considerations of the power supply which has been especially developed for the purpose of these experiments

Far Zone Effects for Integral Transformations: Theory and Implementation

Integrální transformace jsou užitečný matematický aparát pro modelování gravitačního pole a vyžadují formulaci integrálních odhadů včetně chybových charakteristik. Pro klasické integrální transformace byla již tato problematika prozkoumána, ale zatím nebyla studována formulace vzájemně vztahující všechny dostupné gravitační pozorovatelné veličiny. Předpokladem je globální pokrytí daty a globální integrace. Dostupnost dat může být omezená, proto globální integraci rozdělujeme na vliv blízkých a vzdálených zón. Výpočet vzdálených zón je nezanedbatelný systematický efekt, vyžadující přesný výpočet. Potřebná teorie a její implementace se realizují v podobě přesného softwarového nástroje. V tomto příspěvku představujeme základní teorii vlivu vzdálených zón. Dále studujeme vlastnosti integrálních jader a Moloděnského koeficientů. V numerických experimentech porovnáme výpočet vzdálených zón numerickou integrací s omezenou sumací ve formě sférických harmonických řad. Jedním z výstupů tohoto příspěvku je i softwarová knihovna na výpočet vlivu vzdálených zón pro integrální transformace až po třetí derivace gravitačního potenciálu.Integral transformations are a useful mathematical apparatus for modelling the gravitational field and require the formulation of integral estimates including error propagation. For classical integral transformations, this issue has already been studied, but the formulation for all available gravitational observables has not been studied yet. The assumption of integral transformations is global data coverage. In practice, however, data availability is limited, so we divide the global integration into the effects of the near and far zones. The computation of distant zones is a non-negligible systematic effect requiring an accurate calculation. The theory is implemented in the form of a precise software. In this paper, we present the basic theory for the evaluation of the far zones. We also investigate properties of integral kernels and truncation error coefficients. In the numerical experiments, we compare calculation of the far zones by numerical integration with truncated spherical harmonic series. One of the outputs of this contribution is a software library for computation of the far zones for integral transformations mutually relating all quantities up to the third derivatives of the gravitational potential

Advanced analysis of transient overvoltage in electromechanical chain fed by SiC inverter

Key areas in the development of More Electrical Aircraft (MEA) are, currently, DC power distribution in higher voltage levels and the use of disruptive technology such as Wide BandGap (WBG) semiconductor. Using WBG components (SiC and GaN) increases the power converter mass density. However, fast switching of WBG components (tens of kV/µs) induces voltage transient overshoots due to parasitic coupling within the inverter. In addition, propagation and reflection phenomena along the harness, even for small lengths, cause voltage overshoots across the loads. Such overvoltage in an electromechanical chain (association of inverter, harness and motor) supplied by the new HVDC 540V aeronautical network could be fatal for the Electrical Insulation System (EIS). This paper proposes an accurate and fast model to predict overvoltage along a harness; it allows to analyze the impact of SiC inverter output voltage waveforms

Overvoltage at motor terminals in SiC-based PWM drives

Key points in the development of More Electrical Aircraft (MEA) are currently DC power distribution in higher voltage levels (540 V) and the use of disruptive technology such as Wide BandGap (WBG) semiconductors in power inverters. Using WBG components (SiC and GaN) increases the power converter mass density. However, fast switching of WBG components (tens of kV/s) induces voltage transient overshoots due to parasitic elements within the inverter. In addition, propagation and reflection phenomena along the harness connected to this inverter, even for small lengths, cause a significant voltage overshoot across the loads. Such overvoltage in Adjustable Speed Drives (ASD: association of inverter, harness and motor) supplied by the new HVDC 540 V aeronautical network could be fatal for the Electrical Insulation System (EIS). This paper proposes a fast and accurate modeling methodology to predict transient overvoltage; it allows us to analyze the impact of SiC inverter technology on overvoltage at motor terminals