Design, taking into account the partial discharges phenomena, of the electrical insulation system (EIS) of high power electrical motors for hybrid electric propulsion of future regional aircrafts

La réduction des émissions de CO2 est un enjeu majeur pour l'Europe dans les années à venir. Les transports sont aujourd'hui à l'origine de 24% des émissions globales de CO2. L'aviation ne représente que 2% des émissions globales de CO2. Cependant, le trafic aérien est en pleine expansion et, déjà, des inquiétudes apparaissent. A titre d'exemple, en Suède, depuis les années 1990, les émissions de CO2 dues au trafic aérien ont augmenté de 61%. Ce constat explique l'apparition du mouvement "Flygskam" qui se repend dans de plus en plus de pays Européen. C'est dans ce contexte que l'Union Européenne a lancé en septembre 2016 le projet Hybrid Aircraft Academic research on Thermal and Electrical Components and Systems (HASTECS). Le consortium regroupe différents laboratoires et Airbus. Ce projet s'inscrit dans le programme "Clean Sky 2" qui vise à développer une aviation plus verte. L'objectif ambitieux est de réduire de 20% les émissions de CO2 et le bruit produits par les avions d'ici 2025. Pour cela, le consortium étudie une architecture hybride de type série. La propulsion est assurée par des moteurs électriques. Deux cibles ont été définies. En 2025, les moteurs doivent atteindre une densité de puissance de 5kW/kg, système de refroidissement inclus. En 2035, la densité de puissance des moteurs sera doublée pour atteindre 10kW/kg. Pour atteindre ces cibles, le niveau de tension sera considérablement augmenté, au-delà du kilovolt. Le risque de décharges électriques dans les stators des moteurs électriques est considérablement accru. L'objectif de cette thèse est de mettre au point un outil d'aide au design du Système d'Isolation Electrique (SIE) primaire du stator de moteur électrique piloté par convertisseur. Elle est découpée en cinq parties. La première partie commence par préciser les enjeux et défis d'une aviation plus verte. Le SIE du stator de moteur électrique est développé. Enfin, les contraintes qui s'appliquent sur le SIE dans l'environnement aéronautique sont identifiées. La deuxième partie présente les différents types de décharges électriques que l'on peut retrouver. Le principal risque vient des Décharges Partielles (DP) qui détériorent peu à peu le SIE. Le principal mécanisme pour expliquer l'apparition des DP est l'avalanche électronique. Le critère de Paschen permet d'évaluer le Seuil d'Apparition des Décharges Partielles (SADP). Différentes techniques permettent de détecter et mesurer l'activité des DP. Des modèles numériques permettent d'évaluer le SADP. La troisième partie présente une méthode originale pour déterminer les lignes de champ électrique dans un problème électrostatique. Elle n'utilise qu'une formulation en potentiel scalaire. La quatrième partie présente une étude expérimentale pour établir une correction du critère de Paschen. Un bobinage de moteur électrique est très loin des hypothèses dans lesquelles ce critère a été originellement défini. Enfin, la cinquième partie est consacrée à l'élaboration de l'outil d'aide au design du SIE. Des abaques sont construites afin de fournir des recommandations sur le dimensionnement des différents isolants dans une encoche de stator. Une réduction du SADP due à une variation combinée de la température et de la pression est prise en compte.Reducing CO2 emissions is a major challenge for Europe in the years to come. Nowadays, transport is the source of 24% of global CO2 emissions. Aviation accounts for only 2% of global CO2 emissions. However, air traffic is booming and concerns are emerging. For instance, CO2 emissions from air traffic have increased by 61% in Sweden since the 1990s. This explains the emergence of the "Flygskam" movement which is spreading in more and more European countries. It is in this context that the European Union launched in September 2016 the project Hybrid Aircraft Academic research on Thermal and Electrical Components and Systems (HASTECS). The consortium brings together different laboratories and Airbus. This project is part of the program "Clean Sky 2" which aims to develop a greener aviation. The ambitious goal is to reduce CO2 emissions and the noise produced by aircraft by 20% by 2025. To do that, the consortium is studying a serial hybrid architecture. Propulsion is provided by electric motors. Two targets are defined. In 2025, the engines must reach a power density of 5kW/kg, including the cooling system. In 2035, the power density of the engines will be doubled to reach 10kW/kg. To reach these targets, the voltage level will be considerably increased, beyond one kilovolt. The risk of electric discharges in the stators of electric motors is considerably increased. The objective of this thesis is to develop a tool to assist in the design of the primary Electrical Insulation System (EIS) of the stator of an electric motor controlled by a converter. It is organized in 5 parts. The first part begins by clarifying the issues and challenges of a greener aviation. The electric motor stator EIS is developed. Finally, the constraints that apply to the EIS in the aeronautical environment are identified. The second part presents the different types of electric discharges that can be found. The main risk comes from Partial Discharges (PD) which gradually deteriorate the EIS. The main mechanism for explaining the appearance of PD is the electronic avalanche. The Paschen criterion makes it possible to evaluate the Partial Discharge Inception Voltage (PDIV). Different techniques are used to detect and measure the activity of PD. Numerical models are used to evaluate the PDIV. The third part presents an original method for determining the electric field lines in an electrostatic problem. It only uses a scalar potential formulation. The fourth part presents an experimental study to establish a correction of the Paschen criterion. An electric motor winding is very far from the hypotheses in which this criterion was originally defined. Finally, the fifth part is devoted to the development of the SIE design aid tool. Graphs are generated to provide recommendations on the sizing of the various insulators in a stator slot. A reduction in the PDIV due to a combined variation in temperature and pressure is taken into account

Tool to design the primary electrical insulation system of low voltage rotating machines fed by inverters

International audienceIn this communication, we describe a methodologic tool (software) that give instruction to design the coil winding of low voltage machines fed by inverters. The aim of this tool is to bring useful information to the coil manufacturer who has, first, to respect the size of the slots, the total copper section (slot occupancy) and the coil voltage that are imposed by the motor designer. Then, to increase the PDIV between turns and between turns and ground to the highest value. For that purpose, by using a numerical simulation that takes into account the Paschen's law, the developed software will provide how to choose and arrange the enameled wires in the slots: random or form-wound coils, wires shape (round or rectangular), number of wires in parallel by turn, insulation thickness (grade), turns arrangement,... up to find the best solution that allow to respect both motor designer and PDIV constraints. Some practical examples will be given to prove the efficiency of such a tool

Revealing the regime of shallow coral reefs at patch scale by continuous spatial modeling

International audienceReliably translating real-world spatial patterns of ecosystems is critical for understanding processes susceptible to reinforce resilience. However, the great majority of studies in spatial ecology use thematic maps to describe habitats and species in a binary scheme. By discretizing the transitional areas and neglecting the gradual replacement across a given space, the thematic approach may suffer from substantial limitations when interpreting patterns created by many continuous variables. Here, local and regional spectral proxies were used to design and spatially map at very fine scale a continuous index dedicated to one of the most complex seascapes, the coral reefscape. Through a groundbreaking merge of bottom-up and top-down approach, we demonstrate that three to seven-habitat continuous indices can be modeled by nine, six, four, and three spectral proxies, respectively, at 0.5 m spatial resolution using hand-and spaceborne measurements. We map the seven-habitat continuous index, spanning major Indo-Pacific coral reef habitats through the far red-green normalized difference ratio over the entire lagoon of a low (Tetiaroa atoll) and a high volcanic (Moorea) island in French Polynesia with 84 and 82% accuracy, respectively. Further examinations of the two resulting spatial models using a customized histoscape (density function of model values distributed on a concentric strip across the reef crest-coastline distance) show that Tetiaroa exhibits a greater variety of coral reef habitats than Moorea. By designing such easy-to-implement, transferrable spectral proxies of coral reef regime, this study initiates a framework for spatial ecologists tackling coral reef biodiversity, responses to stresses, perturbations and shifts. We discuss the limitations and contributions of our findings toward the study of worldwide coral reef resilience following stochastic environmental change

De la mine à l’habitat:Économie des productions minières du Bassin de Mons au Néolithique. De la fin du 5e millénaire à la fin du 3e millénaire.

info:eu-repo/semantics/nonPublishe

Mining for a week or for centuries: Variable aims of flint extraction sites in the Mons Basin (Province of Hainaut, Belgium) within the lithic economy of the Neolithic

The Mons Basin (Province of Hainaut, western Belgium) is a geologically rich region, particularly from the point of view of Upper Cretaceous sedimentary deposits, conducive to an important flint gathering activity during the whole regional Prehistory. Focusing on the Neolithic period, indications of flint procurement as early as the end of the 6th millennium have been recorded, but there are concrete evidences of mining sites in the region since the second half of the 5th millennium. Flint extraction activities have lasted at least until the second half of the 3rd millennium. According to literature and recent researches, eleven sites could be extraction sites, including the World Heritage site of Spiennes. This paper critically assesses the accuracy of the data available and focuses on the issue of the unequal function of these extraction sites and their socio-economic function for Neolithic communities. Is it really possible to establish a hierarchy between the extraction sites? Can different acquisition-production strategies be highlighted? These questions are dealt with by synthesizing the data concerning the methods of flint exploitation in the Mons Basin, the qualitative and quantitative characteristics of the products relative to the production intentions but also by addressing the issue of their importance in exchange networks

Shoulder biomechanics in normal and selected pathological conditions

The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon. Shoulder stabilization techniques include anatomic procedures such as repair of the labrum or restoration of bone loss, but also non-anatomic options such as remplissage or tendon transfers.Rotator cuff repair should restore the cuff anatomy, reattach the rotator cable and respect the coracoacromial arch whenever possible. Tendon transfer, superior capsular reconstruction or balloon implantation have been proposed for irreparable lesions.Shoulder rehabilitation should focus on restoring balanced glenohumeral and scapular force couples in order to avoid an upward migration of the humeral head and secondary cuff impingement. The primary goal of cuff repair is to be as anatomic as possible and to create a biomechanically favourable environment for tendon healing

Evaluation of the subscapularis split created with passive rotation during arthroscopic dynamic anterior stabilization (DAS): A cadaveric study.

Abstract Introduction The purpose of the present study was to analyze the ability to create a subscapularis split by passive rotation of the arm during dynamic anterior stabilization (DAS) and to analyze the new geometry of the long head of the biceps LHB. Hypothesis The hypothesis was that this passive simple technique can create subscapularis split without additional dissection giving rise to new position of LHB with a new stabilization function. Material and methods A technique of subscapularis split using the LHB was used in 12 fresh-frozen human cadaveric shoulders. A subscapularis split was created by passive rotation of the arm after the LHB is shuttled into the joint during DAS. The length of the subscapularis split, post-DAS position and length of the LHB, and the angulation of the LHB relative to bicipital groove were measured after DAS and if this new geometry can give a new dynamic effect on subscapularis muscle. Results The mean length of the subscapular split after maximal rotation was 20.4 ± 6.0 mm (range: 10–32 mm). The mean elongation of the LHB was 0.6 ± 1.4 mm (range: −1 to +3 mm). The final angle of the LHB relative to the bicipital groove was 45 ± 5 degrees (range: 41 to 55 degrees). Discussion There is no need to create a distinct split prior to DAS. Additionally, DAS maintains the length-tension relationship of the LHB. The post-procedure medial angulation of the LHB relative to the bicipital groove may provide a lowering of the subscapularis, helping explain the anterior reinforcement of this technique. Level of evidence Basic science study, cadaver study

Tool to design the primary electrical insulation system of low voltage rotating machines fed by inverters

In this communication, we describe a methodologic tool (software) that give instruction to design the coil winding of low voltage machines fed by inverters. The aim of this tool is to bring useful information to the coil manufacturer who has, first, to respect the size of the slots, the total copper section (slot occupancy) and the coil voltage that are imposed by the motor designer. Then, to increase the PDIV between turns and between turns and ground to the highest value. For that purpose, by using a numerical simulation that takes into account the Paschen's law, the developed software will provide how to choose and arrange the enameled wires in the slots: random or form-wound coils, wires shape (round or rectangular), number of wires in parallel by turn, insulation thickness (grade), turns arrangement,... up to find the best solution that allow to respect both motor designer and PDIV constraints. Some practical examples will be given to prove the efficiency of such a tool

Outil d’aide au design du système d’isolation primaire de machines tournantes basse tension alimentées par onduleur

Dans cet article, la méthodologie d’un outil (programme) donnant des instructions pour le design du bobinage de machines basse tension alimentées par onduleur est présentée. L’objectif de cet outil est d’apporter des informations utiles au bobineur qui doit, d’abord, respecter les dimensions de l’encoche, la section totale de cuivre (remplissage) et la tension appliquée à la bobine, imposés par le motoriste. Ensuite, d’augmenter le seuil d’apparition des décharges partielles (SADP) entre spires et entre spire et fond d’encoche jusqu’à la valeur la plus élevée. Pour cela, en utilisant une simulation numérique qui prend en compte la loi de Paschen, le logiciel développé devra choisir et arranger les fils émaillés dans l’encoche: bobinage en vrac ou préformé, forme des conducteurs (fils ronds ou méplats), nombre de conducteurs en parallèle par spire, épaisseur du vernis d’émail (grade), disposition des spires… ce jusqu’à trouver la meilleure solution qui permet de respecter les contraintes données par le motoriste et le SADP. Des exemples seront donnés pour démontrer l’efficacité d’un tel outil