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Preda Ioana

Preda Ioana

Professeure HES associée


COMPÉTENCES PRINCIPALES

dielectric materials

high voltage insulation

materials for electrical eng.

polymer, resins, insulating systems

Finite element modeling (Comsol)


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Contrat principal

Professeure HES associée

Téléphone: +41 26 429 65 58

Bureau: C20.11

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH
Haute école d'ingénierie et d'architecture de Fribourg

Institut
iPrint - Institut de printing

BSc HES-SO en Génie électrique - Haute école d'ingénierie et d'architecture de Fribourg

  • Electricité 1 (Introduction to electrodynamics)
  • Matériaux de l'électrotechnique (Materials science for electrical engineers)
  • Systèmes énergétiques (Energy and electricity generation / Smart Energy Systems 1)
  • Modélisation et simulation (Modeling and numerical simulations)
  • MEMS Design (HES-SO Master in Micro and Nano technology)



2020

Dielectric properties of a semicrystalline supramolecular polymer ArODES Conference

Ioana Preda

Proceedings of IEEE 2020 International Conference on Dielectrics, 6th-31st July 2020, Valencia, Spain

Lien vers la publication

Résumé:

Supramolecular polymers (SPs) are assemblies of monomers that bind to another through non-covalent interactions. The reversible nature of these interactions permits one to temporarily disassemble SPs “on command” by applying an appropriate stimulus, which is advantageous for processing and recycling and allows creating stimuli-responsive materials. Here we report on the dielectric properties of an SP network assembled from monomers based on polypropylene oxide (PPO) cores, functionalized with UPy groups. In this work, we measured the DC breakdown strength, dielectric relaxation and electrical conductivity and show that the dielectric properties are similar to those of silicones or silicon-based adhesives. However, the material is reprocessable, thus has a potential for medium voltage applications, within the context of a circular economy.


Characterization of dielectric walls of capacitors ArODES Conference

Ioana Preda

Proceedings of IEEE 2020 International Conference on Dielectrics, 6th-31st July 2020, Valencia, Spain

Lien vers la publication

Résumé:

This work presents the preliminary results of a study that proposes the development of capacitors with similar or better performance in terms of reliability and partial discharges (PD) level than their oil-impregnated counterparts. It presents the comparison of several configurations and technologies of layered dielectric films capacitors impregnated with a commercial polymeric resin, with the aim to improve the properties of its inner dielectric wall. To find a suitable match between the different dielectric film arrangements and technologies with the polymeric resin used, tests on different sample configurations were carried out. These tests also covered the impact of the surface treatment prior to impregnation and the final enhancement of dielectric properties of the system due to the encapsulating polymeric resin. To ensure a reliable fabrication process, the Vacuum Pressure Impregnation (VPI) technique was used. The results show that rough polypropylene (PPR) films with prior surface treatment and set in polymeric resin may be the best candidate to compete with current technologies to carry out oil-free capacitors.




2018

Lightning breakdown voltage of dielectric oil : discussion on measuring setups and standards ArODES Conference

Ioana Preda

Proceedings of the 36th Electrical Insulation Conference (EIC), San Antonio, TX, USA, 17-20 June 2018

Lien vers la publication

Résumé:

Nowadays, more and more studies present the results obtained while testing the lightning impulse breakdown behavior of newly developed, innovative dielectric oils. As showed for industrial frequencies, clear standardized test conditions are mandatory to allow the interpretation of test results without uncertainties. This paper addresses the characteristics of the measuring cell suggested by ASTM and IEC standards and their influence on performing impulse breakdown measurements. As an addition to the results recently published by other research teams, this work intends to discuss several aspects that could be further investigated in a working group. The joint research could provide the ASTM and the IEC standards organizations with a broader view of lightning impulse breakdown (LI) and withstand data that can benefit and improve their regulation.


A digital robust control scheme for dual half-bridge DC-DC converters ArODES Conference

André Rotzetta, Ioana Preda

2018 IEEE Applied Power Electronics Conference and Exposition (APEC)

Lien vers la publication

Résumé:

This paper presents a digital control scheme used in the control system of a bi-directional Dual Half-Bridge (DHB) converter over a wide range of operating conditions (load variations, input voltage changes). The proposed control scheme is a nonlinear current controller, where it enforces the current error of the high frequency transformer to converge to zero in a geometric progression. It offers higher stability, improved transient performance and increased robustness compared to the conventional control methods in DHB converters. Moreover, the proposed control scheme is a simple structure technique, which is easy to implement on digital microprocessors (e.g. DSP, FPGA). Simulation and experimental results show the superior performance of the GSC compared to other conventional control techniques.


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