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Ben Abdelmlek K.,Unite dEtude des Milieux Ionises et Reactifs | Araoud Z.,Unite dEtude des Milieux Ionises et Reactifs | Ghnay R.,Unite dEtude des Milieux Ionises et Reactifs | Abderrazak K.,Unite de Thermique et Thermodynamique des Procedes Industriels | And 2 more authors.
Applied Thermal Engineering | Year: 2016

This paper presents the details of a numerical study of the LEDs thermal conduction path deficiency. A three-dimensional numerical modeling using COMSOL Multiphysics® simulation software has been developed. The model was then validated by the literature, showed a good agreement. The effect of the number of LED-chips put on substrate was studied since it can affect the junction temperature and participate severely on the LED degradation. In addition, when there is trouble in the LED package, junction temperature can increase widely with no indication from the heat sink temperature, even with an efficient heat sink design. To justify this fact, a study of the effect of a deficient thermal conduction path between the heat sink and the thermal grease was performed by two methods: adding an air layer between the TIM and the heat sink, and modifying the effective thermal conductivity of the TIM. Its effects on the junction temperature, the heat sink average temperature, the total thermal resistance and the luminous flux was also investigated and it was found that a deficient thermal path affects severely the thermal properties of LED package even with an efficient heat sink. © 2016 Elsevier Ltd. All rights reserved.

Floricau D.,Polytechnic University of Bucharest | Richardeau F.,Toulouse 1 University Capitole | Richardeau F.,Ecole Polytechnique - Palaiseau | Richardeau F.,University Paul Sabatier | And 2 more authors.
IEEE Transactions on Industrial Electronics | Year: 2011

In this paper, a new three-level (3L) converter is presented. It is called 3L Vienna neutral-point-clamped (3L-VNPC) converter and consists of two stacked high-frequency (HF) commutation cells working with a shared power device. The HF cells are connected to a single-phase switched bridge controlled at low frequency. The 3L-VNPC topology is extended to 3L active VNPC (3L-AVNPC) concept, which is generalized for five levels (5L) and N odd voltage levels (N L). The proposed multilevel converters can be seen as two cascaded voltage stages. The high-voltage stage is specific to the single-phase switched bridge, while the low-voltage (LV) stage corresponds to the stacked HF cells with shared power devices. The new concept AVNPC is a useful and suitable solution for medium-voltage applications, where small modulation index (M) is as crucial as large M. The analyses of the new converters are verified by simulations both for 3L and for 5L topologies, and their features are generalized for NL. Experimental results for single-phase 3L-AVNPC converter on an LV test bench are also provided to validate the proper operation of the new concept. © 2011 IEEE.

Breton M.,Institute Gustave Roussy | Buret F.,Ecole Centrale Lyon | Krahenbuhl L.,Ecole Centrale Lyon | Leguebe M.,Institute National Of La Recherche En Informatique Appliquee Of Bordeaux | And 5 more authors.
IEEE Transactions on Magnetics | Year: 2015

We propose a non-linear steady-state model of irreversible electropermeabilization in a biological tissue. The non-linear problem is solved using a modified fixed point iteration. The unknown parameters are experimentally estimated from the observation of the necrosis on a potato tissue for different applied voltages. A variability study of the parameters involved in the model is performed. © 2015 IEEE.

Ibrahim M.,Laboratoire Plasma et Conversion dEnergie | Bernard L.,Laboratoire Of Genie Electrique Et Electronique Of Paris | Pichon L.,Laboratoire Of Genie Electrique Et Electronique Of Paris | Laboure E.,Laboratoire Of Genie Electrique Et Electronique Of Paris | And 4 more authors.
IEEE Transactions on Power Electronics | Year: 2016

This paper focuses on the interoperability analysis of a resonating contactless charging system for electric vehicles (EVs). The design uses different inductive loops realized by industrial partners. It highlights an advanced electromagnetic modeling (EM) concerning the geometrical characteristics, the resonant topologies, and the control loop. It is shown that the EV chassis plays a major role in the calculation of the electrical parameters and the radiation of the interoperable system. Furthermore, the position of the interoperable magnetic couplers with respect to the EV (middle or backend) has an important effect on the values of the coupling factor and also for the radiation of the system. Finally, an efficiency of 90% is realized in the experimental test with the interoperability which gives flexibility for the driver to use charging stations with different technologies. © 2016 IEEE.

Wormeester G.,Centrum Wiskunde and Informatica CWI | Pancheshnyi S.,Laboratoire Plasma et Conversion dEnergie | Luque A.,Institute Astrofisica Of Andalucia | Nijdam S.,TU Eindhoven | And 2 more authors.
Journal of Physics D: Applied Physics | Year: 2010

Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2. We also test reasonable parameter changes of the photo-ionization model. We find that photo-ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in high purity nitrogen, but not in air. © 2010 IOP Publishing Ltd.

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