Regularly used in power transformers, grain-oriented (GO) steels are also usually chosen for the ... more Regularly used in power transformers, grain-oriented (GO) steels are also usually chosen for the manufacturing of the stator cores of hydro generator and turbogenerator. These steels are renowned for their high magnetic performances in the rolling direction (RD) (high permeability and low magnetic losses). Nevertheless, in a turbogenerator where GO steels are employed to reduce the size of the stator core, the magnetic flux flows through several successive directions within the plane of the steel. So, the anisotropic behavior of the GO steel has to be considered in the design step of the related devices in order to improve their energy efficiency as well as their diagnosis based on modeling. In this article, an anisotropic phenomenological iron loss model, quite recently developed, has been studied and successfully implemented in a finite element method (FEM) simulation environment. The implementation has been validated against experimental data achieved on an industrial conventional GO grade typically used in turbogenerators. The results show a good agreement of the computational results with the experiments for both quasi-static and dynamic regimes.
Conference Record of the 2008 IEEE International Symposium on Electrical Insulation, 2008
During recent years, one of the main causes of large generators failure reported worldwide is rel... more During recent years, one of the main causes of large generators failure reported worldwide is related to the stator insulation defaults. For the majority of studied cases, the insulation weakness is the result of cooling system problems, generally water micro-leakage located between the water joint box and the end of the stator bars. Experimentations have been conducted over more than one year on several stator bars to determine the water propagation law in the main insulation. The goal of this article is to estimate the potential breakdown risk of high voltage generator stator bars presenting different levels of humidity content. The risk estimation is based on electrical field constraint calculation using a finite element model.
2016 IEEE Conference on Electromagnetic Field Computation (CEFC), 2016
In this communication, an a posteriori equilibrated error estimator for the 3D Finite Element app... more In this communication, an a posteriori equilibrated error estimator for the 3D Finite Element approximation of the eddy current problem is developed. Upper and lower bounds for the error are provided. Finally some numerical tests are performed in order to validate the theoretical results and check the efficiency of the estimator.
2019 6th International Advanced Research Workshop on Transformers (ARWtr), 2019
This paper deal with the modeling of large power and distribution transformers by means of reluct... more This paper deal with the modeling of large power and distribution transformers by means of reluctance network method. It's about a meshed approach that has the flexibility to fit different transformers topologies. The nonlinear behavior and the coupling with the electrical circuit have been considered. The proposed model has the smartness to estimate accurately the appropriate distributions of the MagnetoMotive Forces (MMF) and the ElectroMotive Forces (EMF) even in the case of eventual defects. The model is generated by MatLab and built automatically under EMTP, which is used as a solver. The obtained results are validated with finite element calculations and with measurements.
2019 19th International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering (ISEF), 2019
This paper deal with the modeling of large power and distribution transformers by means of reluct... more This paper deal with the modeling of large power and distribution transformers by means of reluctance network method. It’s about a meshed approach that has the flexibility to fit different transformers topologies. The non-linear behavior and the coupling with the electrical circuit have been considered. The proposed model has the smartness to estimate accurately the appropriate distributions of the MagnetoMotive Forces (MMF) and the ElectroMotive Forces (EMF) even in the case of eventual defects. The model is generated by MatLab and built automatically under EMTP-RV, which is used as a solver. The obtained results are validated with finite element calculations and with measurements.
Grain-oriented (GO) materials are widely known for their strong anisotropic behavior. Their magne... more Grain-oriented (GO) materials are widely known for their strong anisotropic behavior. Their magnetic characteristics depend on the angle between the applied magnetic field and rolling direction (RD). However, these characteristics can be further modified according to their stacking configuration and to the influence of the demagnetizing field. In this paper, a 3-D finite element analysis is performed in order to study the effect of the parallel and x-stacking configuration on the magnetic properties of the lamination stack. The results are interpreted in terms of the demagnetizing field which vectorially combined with the applied field affects the magnetization.
The modeling of the capacitive phenomena, including the inductive effects becomes critical, espec... more The modeling of the capacitive phenomena, including the inductive effects becomes critical, especially in the case of a power converter with high switching frequencies, supplying an electrical device. At a low frequency, the electro-quasistatic (EQS) model is widely used to study the coupled resistive-capacitive effects, while the magneto-quasistatic (MQS) model is used to describe the coupled resistive-inductive effects. When the frequency increases, the Darwin model is preferred, which is able to capture the coupled resistive-capacitive-inductive effects by neglecting the radiation effects. In this work, we are interested in specifying the limits of these models, by investigating the influence of the frequency on the electromagnetic field distributions and the impedance of electromagnetic devices. Two different examples are carried out. For the first one, to validate the Darwin model, the measurement results are provided for comparison with the simulation results, which shows a go...
Abstract: Due to their texture, the magnetic characteristics of grain oriented (GO) steels depend... more Abstract: Due to their texture, the magnetic characteristics of grain oriented (GO) steels depend on the angle between the applied magnetic field and the rolling direction RD. These GO steels exhibit advantageous magnetic characteristics, such as high permeability in the RD and relatively poor properties in the transverse direction TD. In order to obtain a better electromagnetic modeling of the electrical energy conversion systems using GO steels, the dissipative phenomena and the anisotropy must be reliably represented. One example is the case of the GO electrical steels used in stators of turbo-generators. In order to create an appropriate model, the associated magnetic losses have to be taken into account for any angle between the applied field and the RD. However, the problem of computing iron losses whatever the angle between the applied field and the RD has remained unsolved especially within the finite element method (FEM) framework.<br/><br/>In this paper, a phen...
Le developpement des convertisseurs de l'electronique de puissance rend possible aujourd'... more Le developpement des convertisseurs de l'electronique de puissance rend possible aujourd'hui des frequences de travail de plus en plus elevees pour les moteurs electriques polyphases. Cependant ces moteurs sont le siege de pertes electromagnetiques plus fortes par rapport aux machines classiques. Il est donc tres important lors de leurs conceptions de disposer d'outils de modelisation suffisamment precis pour estimer au mieux ces pertes. La difficulte reside dans le fait que de nombreux phenomenes physiques sont couples. Ici nous ne nous sommes interesses qu’a l'aspect electromagnetique. Nous avons mis au point une methodologie pour calculer ces pertes. Elle repose, a la fois, sur le formalisme bond graph qui permet aisement de passer d'un domaine physique a un autre et sur le calcul de champs electromagnetiques par la methode des elements finis. Elle se divise en deux etapes: la premiere consiste a utiliser les bond graphs pour obtenir un modele macroscopique de l'association convertisseurs machines. Ce modele fournit les courants d'alimentation qui sont les grandeurs d'entree du modele elements finis pour le calcul de champs electromagnetiques. A partir de la repartition du champ magnetique ainsi obtenue, les pertes electromagnetiques sont finalement calculees
Numerical dosimetry is widely used to demonstrate compliancy to regulation. There are several pos... more Numerical dosimetry is widely used to demonstrate compliancy to regulation. There are several possible approaches but whatever the method is, an appreciation of the numerical imperfections is required. We proposed here a geometrical criterion on the finite element mesh. We applied this method on an academic benchmark to demonstrate the efficiency and the sensitivity of numerical methods to this criterion, then on a human phantom in order to check mesh quality. Computations are performed on three software. Results show a good agreement between some results. However there is a great discrepancy on some organs.
Regularly used in power transformers, grain-oriented (GO) steels are also usually chosen for the ... more Regularly used in power transformers, grain-oriented (GO) steels are also usually chosen for the manufacturing of the stator cores of hydro generator and turbogenerator. These steels are renowned for their high magnetic performances in the rolling direction (RD) (high permeability and low magnetic losses). Nevertheless, in a turbogenerator where GO steels are employed to reduce the size of the stator core, the magnetic flux flows through several successive directions within the plane of the steel. So, the anisotropic behavior of the GO steel has to be considered in the design step of the related devices in order to improve their energy efficiency as well as their diagnosis based on modeling. In this article, an anisotropic phenomenological iron loss model, quite recently developed, has been studied and successfully implemented in a finite element method (FEM) simulation environment. The implementation has been validated against experimental data achieved on an industrial conventional GO grade typically used in turbogenerators. The results show a good agreement of the computational results with the experiments for both quasi-static and dynamic regimes.
Conference Record of the 2008 IEEE International Symposium on Electrical Insulation, 2008
During recent years, one of the main causes of large generators failure reported worldwide is rel... more During recent years, one of the main causes of large generators failure reported worldwide is related to the stator insulation defaults. For the majority of studied cases, the insulation weakness is the result of cooling system problems, generally water micro-leakage located between the water joint box and the end of the stator bars. Experimentations have been conducted over more than one year on several stator bars to determine the water propagation law in the main insulation. The goal of this article is to estimate the potential breakdown risk of high voltage generator stator bars presenting different levels of humidity content. The risk estimation is based on electrical field constraint calculation using a finite element model.
2016 IEEE Conference on Electromagnetic Field Computation (CEFC), 2016
In this communication, an a posteriori equilibrated error estimator for the 3D Finite Element app... more In this communication, an a posteriori equilibrated error estimator for the 3D Finite Element approximation of the eddy current problem is developed. Upper and lower bounds for the error are provided. Finally some numerical tests are performed in order to validate the theoretical results and check the efficiency of the estimator.
2019 6th International Advanced Research Workshop on Transformers (ARWtr), 2019
This paper deal with the modeling of large power and distribution transformers by means of reluct... more This paper deal with the modeling of large power and distribution transformers by means of reluctance network method. It's about a meshed approach that has the flexibility to fit different transformers topologies. The nonlinear behavior and the coupling with the electrical circuit have been considered. The proposed model has the smartness to estimate accurately the appropriate distributions of the MagnetoMotive Forces (MMF) and the ElectroMotive Forces (EMF) even in the case of eventual defects. The model is generated by MatLab and built automatically under EMTP, which is used as a solver. The obtained results are validated with finite element calculations and with measurements.
2019 19th International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering (ISEF), 2019
This paper deal with the modeling of large power and distribution transformers by means of reluct... more This paper deal with the modeling of large power and distribution transformers by means of reluctance network method. It’s about a meshed approach that has the flexibility to fit different transformers topologies. The non-linear behavior and the coupling with the electrical circuit have been considered. The proposed model has the smartness to estimate accurately the appropriate distributions of the MagnetoMotive Forces (MMF) and the ElectroMotive Forces (EMF) even in the case of eventual defects. The model is generated by MatLab and built automatically under EMTP-RV, which is used as a solver. The obtained results are validated with finite element calculations and with measurements.
Grain-oriented (GO) materials are widely known for their strong anisotropic behavior. Their magne... more Grain-oriented (GO) materials are widely known for their strong anisotropic behavior. Their magnetic characteristics depend on the angle between the applied magnetic field and rolling direction (RD). However, these characteristics can be further modified according to their stacking configuration and to the influence of the demagnetizing field. In this paper, a 3-D finite element analysis is performed in order to study the effect of the parallel and x-stacking configuration on the magnetic properties of the lamination stack. The results are interpreted in terms of the demagnetizing field which vectorially combined with the applied field affects the magnetization.
The modeling of the capacitive phenomena, including the inductive effects becomes critical, espec... more The modeling of the capacitive phenomena, including the inductive effects becomes critical, especially in the case of a power converter with high switching frequencies, supplying an electrical device. At a low frequency, the electro-quasistatic (EQS) model is widely used to study the coupled resistive-capacitive effects, while the magneto-quasistatic (MQS) model is used to describe the coupled resistive-inductive effects. When the frequency increases, the Darwin model is preferred, which is able to capture the coupled resistive-capacitive-inductive effects by neglecting the radiation effects. In this work, we are interested in specifying the limits of these models, by investigating the influence of the frequency on the electromagnetic field distributions and the impedance of electromagnetic devices. Two different examples are carried out. For the first one, to validate the Darwin model, the measurement results are provided for comparison with the simulation results, which shows a go...
Abstract: Due to their texture, the magnetic characteristics of grain oriented (GO) steels depend... more Abstract: Due to their texture, the magnetic characteristics of grain oriented (GO) steels depend on the angle between the applied magnetic field and the rolling direction RD. These GO steels exhibit advantageous magnetic characteristics, such as high permeability in the RD and relatively poor properties in the transverse direction TD. In order to obtain a better electromagnetic modeling of the electrical energy conversion systems using GO steels, the dissipative phenomena and the anisotropy must be reliably represented. One example is the case of the GO electrical steels used in stators of turbo-generators. In order to create an appropriate model, the associated magnetic losses have to be taken into account for any angle between the applied field and the RD. However, the problem of computing iron losses whatever the angle between the applied field and the RD has remained unsolved especially within the finite element method (FEM) framework.<br/><br/>In this paper, a phen...
Le developpement des convertisseurs de l'electronique de puissance rend possible aujourd'... more Le developpement des convertisseurs de l'electronique de puissance rend possible aujourd'hui des frequences de travail de plus en plus elevees pour les moteurs electriques polyphases. Cependant ces moteurs sont le siege de pertes electromagnetiques plus fortes par rapport aux machines classiques. Il est donc tres important lors de leurs conceptions de disposer d'outils de modelisation suffisamment precis pour estimer au mieux ces pertes. La difficulte reside dans le fait que de nombreux phenomenes physiques sont couples. Ici nous ne nous sommes interesses qu’a l'aspect electromagnetique. Nous avons mis au point une methodologie pour calculer ces pertes. Elle repose, a la fois, sur le formalisme bond graph qui permet aisement de passer d'un domaine physique a un autre et sur le calcul de champs electromagnetiques par la methode des elements finis. Elle se divise en deux etapes: la premiere consiste a utiliser les bond graphs pour obtenir un modele macroscopique de l'association convertisseurs machines. Ce modele fournit les courants d'alimentation qui sont les grandeurs d'entree du modele elements finis pour le calcul de champs electromagnetiques. A partir de la repartition du champ magnetique ainsi obtenue, les pertes electromagnetiques sont finalement calculees
Numerical dosimetry is widely used to demonstrate compliancy to regulation. There are several pos... more Numerical dosimetry is widely used to demonstrate compliancy to regulation. There are several possible approaches but whatever the method is, an appreciation of the numerical imperfections is required. We proposed here a geometrical criterion on the finite element mesh. We applied this method on an academic benchmark to demonstrate the efficiency and the sensitivity of numerical methods to this criterion, then on a human phantom in order to check mesh quality. Computations are performed on three software. Results show a good agreement between some results. However there is a great discrepancy on some organs.
Uploads
Papers by jean-pierre ducreux