47 research outputs found
Analytical Calculation of Rotor Magnet Eddy-Current Losses for High Speed IPMSM
International audienceFor high-speed machines applications, eddy-current losses in the interior permanent magnet of synchronous machine (IPMSM) form a portion of the total losses which can be significant. Indeed, the magnets are exposed to the harmonic fields which rotate with respect to the rotor. The induced losses in the magnets provoke temperature arising that must be limited to avoid the risk of demagnetization. The study carries out a prediction of eddy current losses in PM where the skin effect is considered. A complete analytical model is presented and compared to 3D Finite Element (FE) harmonic computations. The results given by the proposed model are in agreement with the FEA results for local electromagnetic quantities and loss calculations. This approach can be useful for losses estimation in magnets when designing machines by analytical method
Optimal design of a wound rotor synchronous generator using genetic algorithm
International audienceThe manufacturers are tempted to reduce the amount of active materials in the devices in order to lower the material bill. However, reducing the weight of the devices directly affects the energy efficiency. In this paper, a solution to this problem is proposed for the case of synchronous wound rotor generators. The trade-off between cost and efficiency is formulated as a constrained optimization problem and solved using a Genetic Algorithm. The cost optimization of three different machines is carried out through various design approaches. The proposed approach always gives better results than the classical approach concerning the global cost of the range
Modélisation analytique d'un moteur synchro-réluctant assisté d'aimants permanents
L'article présente un modèle analytique électromagnétique pour un Moteur Synchro-Réluctant Assisté d'Aimants Permanents (MSR-AP). Le modèle proposé se base sur les équations de Maxwell : le théorème d'Ampère et la loi de conservation de flux. La saturation magnétique dans le stator et le rotor est prise en considération, ainsi que l'influence des ponts magnétiques des barrières de flux. Le but est de calculer les performances du moteur (couple électromagnétique, tension phase-phase et facteur de puissance) pour plusieurs valeurs de courants et d'angles de calage. Les résultats du modèle analytique sont comparés à ceux des éléments finis (MEF) et sont validés par des essais sur un prototype de moteur
Hearing Loss and Sixth Cranial Nerve Paresis after COVID-19
An 80-year-old patient was admitted to the internal medicine department for binocular diplopia and hearing loss with sudden onset. The patient had presented with SARS-CoV-2 infection 3 weeks previously and had been admitted to hospital. Complete work-up including autoimmunity, serum and LCR viral serology and MRI did not allow a diagnosis to be established. The hypothesis of a microvascular origin or the previous SARS-CoV-2 infection was considered. The latter was retained in light of the temporal relationship, the absence of other pathologies after exhaustive work-up, and the clinical evolution
Focal myositis of the sternocleidomastoid muscle: a rare and uncommon cause of cervical mass
We report on a 70-year-old male patient admitted to the internal medicine department for evaluation of a right cervical mass. He had been treated with antibiotics as an outpatient by his primary care doctor. Upon admission the patient was asymptomatic, but within a few hours his cervical mass enlarged; this enlargement was confined to the right sternocleidomastoid muscle. Complete blood investigations including serology and autoimmunity were negative. The neck scan and MRI were in favour of myositis. No other lesions were found either in the nasal fibre-optic exam or in the thoracic-abdominal-pelvic scan. The biopsy of the muscle showed a lymphoplasmacytic inflammatory infiltrate of the perimysium. The diagnosis of focal myositis was made. The patient clinically improved during hospitalisation with complete resolution of symptoms without any specific intervention
Modelling and optimisation of a set converter - machine. Application to High-Speed Drives
Les travaux présentés dans cette thèse concernent la modélisation et l’optimisation d’un ensemble Convertisseur-Machine devant fonctionner à haute vitesse. La première partie établit un état de l’art des méthodologies de conception relatives au dimensionnement optimal de systèmes d’entrainement et analyse les particularités du fonctionnement à haute vitesse. Puis, une modélisation analytique multiphysique des éléments du système est réalisée. Afin de mener une conception globalement optimale, les interactions significatives entre les éléments du système doivent être modélisées. Cela est effectué à l’aide d’une modélisation électrique fine – qui est le cœur de la caractérisation des interactions – mettant en œuvre une approche harmonique originale. Il en découle alors une modélisation des interdépendances entre onduleur et machine au niveau des pertes dans le système et de la qualité du couple. La modélisation est ensuite couplée à un algorithme génétique selon une méthodologie de conception hybride faisant intervenir des modèles analytiques puis par éléments finis. Enfin, cette démarche est appliquée au dimensionnement de deux systèmes d’entrainement dont le moteur est une MSAP à aimantation orthoradiale. Ces deux cas d’application ont été traités avec succès et ont mis en avant l’intérêt d’une approche « Système » dans la conception de systèmes d’entrainement. Par ailleurs nous avons analysé les morphologies des machines en fonction de la vitesse de rotation. Ceci a fait ressortir des capacités intéressantes de ce type de machines – pour la haute vitesse – d’un point de vue magnétique, mécanique, et des pertes au rotor.The work presented in this thesis aims at the modelling and optimisation of a set Converter-Machine that is intended to run at high speeds. The first part is a state of the art of the conception methodologies related to the optimal design of drives and investigates the particularities of high speed operations. Then, an analytic and multiphysic modelling of the elements of the system is performed. But, in order to carry out a global optimal conception, the significant interactions between the various elements of the system must be modelled. This is achieved through a precise electrical model – that is the core of the characterization of the interactions – involving an original harmonic approach. From this follows a modelling of the interdependences between inverter and machine in the system losses and in the torque quality. The models are then associated with a genetic algorithm according to a hybrid methodology of conception involving analytical and finite-element models. Finally, this procedure is applied to the design of two drives of which the motor is a PMSM with circumferentially magnetised magnets. These two cases have been successfully handled and clearly show the assets of a “System” approach for the design of drives. In addition, the morphologies of the optimal machines are analysed according to their rotation speed. This analysis highlights some interesting abilities of this kind of machines – in high speed – regarding the magnetic and mechanical behaviours, and the rotor losses
Modélisation et optimisation d’un ensemble convertisseur-machine. Application aux systèmes d’entrainement à haute vitesse.
The work presented in this thesis aims at the modelling and optimisation of a set Converter-Machine that is intended to run at high speeds. The first part is a state of the art of the conception methodologies related to the optimal design of drives and investigates the particularities of high speed operations. Then, an analytic and multiphysic modelling of the elements of the system is performed. But, in order to carry out a global optimal conception, the significant interactions between the various elements of the system must be modelled. This is achieved through a precise electrical model – that is the core of the characterization of the interactions – involving an original harmonic approach. From this follows a modelling of the interdependences between inverter and machine in the system losses and in the torque quality. The models are then associated with a genetic algorithm according to a hybrid methodology of conception involving analytical and finite-element models. Finally, this procedure is applied to the design of two drives of which the motor is a PMSM with circumferentially magnetised magnets. These two cases have been successfully handled and clearly show the assets of a “System” approach for the design of drives. In addition, the morphologies of the optimal machines are analysed according to their rotation speed. This analysis highlights some interesting abilities of this kind of machines – in high speed – regarding the magnetic and mechanical behaviours, and the rotor losses.Les travaux présentés dans cette thèse concernent la modélisation et l’optimisation d’un ensemble Convertisseur-Machine devant fonctionner à haute vitesse. La première partie établit un état de l’art des méthodologies de conception relatives au dimensionnement optimal de systèmes d’entrainement et analyse les particularités du fonctionnement à haute vitesse. Puis, une modélisation analytique multiphysique des éléments du système est réalisée. Afin de mener une conception globalement optimale, les interactions significatives entre les éléments du système doivent être modélisées. Cela est effectué à l’aide d’une modélisation électrique fine – qui est le cœur de la caractérisation des interactions – mettant en œuvre une approche harmonique originale. Il en découle alors une modélisation des interdépendances entre onduleur et machine au niveau des pertes dans le système et de la qualité du couple. La modélisation est ensuite couplée à un algorithme génétique selon une méthodologie de conception hybride faisant intervenir des modèles analytiques puis par éléments finis. Enfin, cette démarche est appliquée au dimensionnement de deux systèmes d’entrainement dont le moteur est une MSAP à aimantation orthoradiale. Ces deux cas d’application ont été traités avec succès et ont mis en avant l’intérêt d’une approche « Système » dans la conception de systèmes d’entrainement. Par ailleurs nous avons analysé les morphologies des machines en fonction de la vitesse de rotation. Ceci a fait ressortir des capacités intéressantes de ce type de machines – pour la haute vitesse – d’un point de vue magnétique, mécanique, et des pertes au rotor
Optimised design of a transformer and an electronic circuit for IGBT drivers signal impulse transmission function based on a virtual prototyping tool
International audienceIn this study, a signal impulse transmission function is investigated which provides high insulation voltage capabilities for IGBT drivers devices. This electrical insulation is achieved with a printed circuit board (PCB) and classical copper windings. Two ferrite cores are added to improve the magnetic coupling effect and thus decrease the impulse current maximum value in the primary side. The electronic circuit involves a series resonant topology in the primary side and a parallel one in the secondary side. The classical electronic components lead potentially to cost-effective solutions. However, so as to optimise the proposed system, a design methodology based on virtual prototyping tools is carried out. The simulation results presented on a Pareto front are analysed with the help of propagation delay and average power consumption. Moreover, measurement results with a 1.6 mm PCB are compared with simulation ones. Finally, the proposed solution and the methodology design are clearly accurate and suitable for power electronic designers and especially for IGBT driver devices designers
Virtual prototyping and pre-sizing methodology for buck DC-DC converters using genetic algorithms
International audienceIn this article, the authors study the pre-sizing approach of DC-DC buck converters useful for electronics and system designers. The pre-sizing step in an industrial process is suitable to obtain a preliminary precise sizing of a sub-system (here a buck DC-DC converter): it permits the system designer to perform a feasibility analysis of an overall system (e.g. that contains a buck DC-DC converter). First, static modelling of power devices is proposed: MOSFET, diode, inductor and heatsink. According to an industrial context, the MOSFETs, diodes and heatsinks fitting curves are issued from the manufacturer-s datasheets. Second, the objective functions are explained in the case of mixed integer programming problems. Then, the optimisation variables and constraints are highlighted. Third, a section describes the choice of a multi-objective optimisation technique that leads to genetic algorithms (GAs). Fourth, the optimisation results are given. The choice of a final solution of the pre-sizing approach is discussed, considering additional constraints such as diode and MOSFET junctions temperatures, switching frequency etc. The authors focus on the general aspect of the optimisation method proposed here. It can also be used by power electronics designers with the help of additional constraints in accordance to their specific applications