Partial discharge testing in aeronautic environment on magnet wire and feeder cables

Rationalization of energy sources aboard aircraft and improvements in more electric technologies are pushing the aeronautic industry to meet the all-electric aircraft challenge. As a result, onboard power has been steadily increasing, reaching 1MW for B787. AC and HVDC network voltage have followed reaching 230VAC and 540VDC increasing the likeliness of partial discharge. In the future, this shift will lead to the complete redesign of the architecture of onboard power systems. The aim of this study is to characterize the partial discharge inception voltage, with the aforementioned constraints in mind, on two components of the electromechanical chain: magnet wires used in electric actuators and feeder cable used in harness

Influence of pressure on partial discharge spectra

In forecoming “more electrical aircrafts”, aircrafts will become more compact and light, as hydraulic, pneumatic or mechanical systems will be replaced by electrical ones. The network voltage is expected to increase far above Paschen’s minimum, thus increasing the risk of partial discharges. These discharges, known as silent enemies, may affect the reliability of the system. Moreover, some electrical equipments are located in unpressurized area and their operating conditions (temperature, pressure) may change in a large range. These environmental parameters (and their cycling) have an influence on discharge inception voltage and may even modify its nature. This paper deals with the influence of the pressure on partial discharges and especially on the modification of partial discharges spectra with pressure. Twisted pairs of enamel wires were subjected to repetitive square voltage waveform and sinusoidal voltage at various pressures

Recent advances in on-line PDs’detection in power conversion chains used in aeronautics.

At the dawn of this new millennium, transportations facing a much greener approach, the main aircrafts manufacturers have to change their paradigms: to replace the combination of hydraulic, pneumatic, electrical and mechanical power by a « More » (and “All” in the future) Electrical Aircraft approach consisting in drastically increasing the power density of electrical power systems without compromising on reliability. The increasing demand for more on board electrical power has led to increase the voltage and/or to change its shape. Such an increase may lead, depending on many parameters related to the electrical characteristics of the power chain (power converter, voltage waveform (dV/dt, frequency, …), the cables length, the type of machine driven) or to the environment (pressure, temperature, relative humidity) to the Partial Discharges Ignition in systems which were not supposed (and have not been designed) to endure them. Partial Discharges are voltage-dependent electrical discharges in insulation, which : - do not lead to a direct breakdown of the system, - lead to a gradual deterioration of the insulating material and to its premature failure - is often defined as “the silent enemy One of the main questions to address is the development of an approach for PD detection in type I machines (according to EIC 60034-18-41) ie machines supposed to be PD free allowing the determination of their existence under very different electrical conditions (PWM) due to the wide nature of the embarked equipment and to the different possible natures of the discharges. Recent advances made in the related different topics i.e on line PD detection under PWM voltage, influence of the pressure, influence of the components types…will be presented and discussed regarding their consequences

Numerical signal processing methods for partial discharge detection in more electrical aircraft

In forecoming “more electrical aircrafts”, aircrafts will become more compact and lighter. Hydraulic, pneumatic or mechanical systems will be replaced by electrical ones thus leading to an increased demand of electric power. The network voltage is expected to increase far above Paschen’s minimum, thus increasing the risk of partial discharges. Furthermore the use of inverter drives will be generalized and PD detection on square voltage powered equipments will become a mandatory challenge. The purpose of this study is to propose a method to denoise partial discharge signals embedded in the electromagnetic noise induced by switchings. This denoising is performed using the wavelet decomposition

Partial Discharges in Aeronautics: The last frontier?

This paper presents the recent advances made in the field of Partial Discharges detection and analysis in the field of aeronautics. More particularly, it intends to present the influence of the voltage waveform on the type of detection method, the role of the assembly process on the PD Inception Voltage and finally an on line PD detection under PWM voltage. The influence of the pressure on the type and nature of the discharges is also discussed

Fluorous l -Carbidopa Precursors : Highly Enantioselective Synthesis and Computational Prediction of Bioactivity

New fluorous enantiopure (S)-α-aminated β-keto esters were prepared through a highly enantioselective electrophilic α-amination step in the presence of europium triflate and (R,R)-phenyl-pybox. These compounds are precursors of fluorinated analogues of l-carbidopa, which is known to inhibit DOPA decarboxylase (DDC), a key protein in Parkinson's disease. Fluorination provides better stability for biological applications, which could possibly lead to DDC inhibitors better than l-carbidopa itself. Induced fit docking computational simulations performed on the new structures interacting with DDC highlight that for an efficient binding at the DDC site, at least one hydroxyl substituent must be present at the aromatic ring of the l-carbidopa analogues and show that the presence of fluorine can further fix the position of the ligand in the active site

Poses – Sur la Mare

Dans le cadre du suivi systématique des sablières dans la vallée de la Seine, mis en place dans la région depuis une dizaine d’années, une fouille et une surface de près de 5 ha a permis l’étude de plusieurs implantations, chronologiquement différentes, couvrant le Néolithique ancien, le Néolithique final (fouille C. Billard) l’âge du Bronze, La Tène finale (fouille T. Dechezleprêtre) et le Gallo-romain (fouille J.-Y. Langlois).Fig. 1 – Plan général des structures du Néolithique au début de ..

A fourfold coordinated point defect in silicon

Due to their technological importance, point defects in silicon are among the best studied physical systems. The experimental examination of point defects buried in bulk is difficult and evidence for the various defects usually indirect. Simulations of defects in silicon have been performed at various levels of sophistication ranging from fast force fields to accurate density functional calculations. The generally accepted viewpoint from all these studies is that vacancies and self interstitials are the basic point defects in silicon. We challenge this point of view by presenting density functional calculations that show that there is a new fourfold coordinated point defect in silicon that is lower in energy

Copper-deficiency in Brassica napus induces copper remobilization, molybdenum accumulation and modification of the expression of chloroplastic proteins

During the last 40 years, crop breeding has strongly increased yields but has had adverse effects on the content of micronutrients, such as Fe, Mg, Zn and Cu, in edible products despite their sufficient supply in most soils. This suggests that micronutrient remobilization to edible tissues has been negatively selected. As a consequence, the aim of this work was to quantify the remobilization of Cu in leaves of Brassica napus L. during Cu deficiency and to identify the main metabolic processes that were affected so that improvements can be achieved in the future. While Cu deficiency reduced oilseed rape growth by less than 19% compared to control plants, Cu content in old leaves decreased by 61.4%, thus demonstrating a remobilization process between leaves. Cu deficiency also triggered an increase in Cu transporter expression in roots (COPT2) and leaves (HMA1), and more surprisingly, the induction of the MOT1 gene encoding a molybdenum transporter associated with a strong increase in molybdenum (Mo) uptake. Proteomic analysis of leaves revealed 33 proteins differentially regulated by Cu deficiency, among which more than half were located in chloroplasts. Eleven differentially expressed proteins are known to require Cu for their synthesis and/or activity. Enzymes that were located directly upstream or downstream of Cu-dependent enzymes were also differentially expressed

Electrophilic aromatic trifluoromethylthiolation with the second generation of trifluoromethanesulfenamide

International audienceDirect trifluoromethylthiolation of various aromatic and heteroaromatic compounds, variously substituted, can be performed with the second generation of trifluoromethanesulfenamide via a ‘Friedel–Crafts-like reaction’. This reaction requires mild conditions with a catalytic amount of protic or Lewis acid. Good results have been obtained, even with aromatic compounds bearing deactivating substituents