Marius Purcar

Numerical optimization of an electrostatic device based on the 3D XFEM and genetic algorithm

The objective of this paper consists in the development, implementation, testing and validation of a new mathematical model based on the eXtended Finite Element Method (XFEM) and Genetic Algorithm (GA) specially designed for modeling the mobile material discontinuities with direct application in optimization of electric structures in 3D space. This new mathematical concept eliminates the conventional use of discrete elements and provides an efficient, stable, accurate and fast calculation scheme, removing the finite elements network re-meshing at each step of optimization.

CAD/CAE modeling of the human exposure to electric field inside a high voltage substation

This paper presents the computer aided design (CAD) and computer aided engineering (CAE) modeling of Cluj-Sud 110 kV high voltage substation in order to examine the influence of substation constructive elements and apparatus (e.g. phase conductors, bypass bus bars, breakers and towers) on the spatial electric field distribution. The substation belongs to FDEE Electrica distributie Transilvania Nord SA. In a first step the detailed three dimensional (3D) CAD models of the substation components are constructed and assembled in the CAD environment SolidWorks. Then the exact 3D coordinates of the terminals are automatically retrieved and the electric field distribution is computed on the 3D CAD model using a CAE software developed. The electric field distribution is represented on horizontal and transversal slices at the 3D CAD model in order to highlight the high intensity field zones and compare them with respect to the actual legislation norms of human exposure.

A study of adaptive mesh refinement techniques for an efficient capture of the thermo-mechanical phenomena in power integrated circuits

Numerical simulation (le. based on the Finite Element Method — FEM) is an important design method and tool that allows prediction of failure position of the Double Diffused Metal-Oxide Semiconductor (DMOS) devices and a comparative analysis of the robustness of different metallization topologies with regard to Thermal Induced Plastic Metal Deformation (TPDM). As the dimension of analyzed components is very small and multiple physical phenomena occur, the finite element mesh size and density is very important for the accuracy and efficiency of the analysis method. The aim of this paper is to present an Adaptive Mesh Refinement (AMR) study for an efficient and accurate quantification by numerical simulation of the thermal induced stress and strain distribution in Power Integrated Circuits (PICs). The study is demonstrated on simple 3D substructures commonly found at different high integration Bipolar CMOS-DMOS (BCD) technologies.

CAD/CAE modeling of electromagnetic field distribution in hv substations and investigation of the human exposure

The recent advances in computer aided design (CAD) modeling of electromagnetic field distribution in high voltage (HV) substation are presented in this paper. The substation constitutive components (e.g. towers, breakers, circuit conductors, bus bars, transformers, etc.) were built-up by the authors as three dimensional (3D) CAD models and stored in a data base under the SolidWorks CAD environment. A computer aided design software (CAE) developed by the authors retrieves the 3D coordinates of the substation constitutive components and based on the specific loads computes the electromagnetic field spatial distribution. Both 3D CAD and CAE approaches are outlined on a 3D CAD model of a cell belonging to a 400kV substation. The simulated electromagnetic field distributions are computed and represented over the HV substation 3D CAD model. This allows to visualize and spot the high concentration electromagnetic field areas. A comparison between the measurements performed in situ and simulated electric field is made. The resulted electromagnetic field is finally compared with the professional human exposure limits in controlled environment.

Shape optimization approach based on the extended finite element method

Purpose – This paper proposes to extend the combination of Extended Finite Element Method (XFEM) and Level Set Method (LSM) from structural mechanics to electromagnetics. Based on this approach, the actual stage of the research work, dedicated to the investigation, development, implementation and validation of a shape optimization methodology, particularly tailored for 2D electric structures is described.Design/methodology/approach – The proposed numerical approach is based on the efficiency of the XFEM and the flexibility of the LSM, to handle moving material interfaces without remeshing the whole studied domain at each optimization step.Findings – This approach eliminates the conventional use of discrete finite elements and provides efficient, stable, accurate and faster computation schemes in comparison with other methods.Research limitations/implications – This research is limited to shape optimization of two‐dimensional electric structures, however, the work can be extended to 3D ones too.Practical i...

A simple metal-semiconductor substructure for the advanced thermo-mechanical numerical modeling of the power integrated circuits

The lifetime of power DMOS devices subjected to Thermal Induced Plastic Metal Deformation (TPMD) is highly dependent on the design of the metallization systems and thus requires the understanding of temperature, stress and strain distribution. This paper introduces and studies via numerical simulations with finite element method (FEM) a simple three dimensional (3D) transistor substructure commonly found in different high integration BCD technologies, for the assessment of thermo-mechanical phenomena in order to identify the areas of high stress accumulation and failure mechanisms.

Thermo-mechanical simulation of the metal-semiconductor structures of power integrated circuits

Thermo-mechanical stress accumulation in the power electronic integrated circuit (PIC) devices influences their lifetime and reliability. In order to determine both the temperature and the stress accumulation, numerical simulation is a very important tool in the design of PIC devices for quantifying and enhancing their lifetime and reliability. An open source solution integrated in Salome-Meca and Code_Aster based on the finite element method (FEM) is used in this paper to analyze the thermo-mechanical behavior on a simple metal-semiconductor structure, which is typically found in a PIC. The computational time and accuracy of the simulations results is improved by finding the optimal mesh configuration. A convergence study is computed for five different cases by progressively reducing the size of the discretization elements (hence, increasing the number of mesh elements) in the area of interest. The results for an optimal relative error and computational time are compared with the results obtained using the commercial software Comsol. The simulated mechanical stress is compared with similar results reported in literature.

Study of the electromagnetic field distribution inside a HV/MV substation

The electromagnetic field interferences (EMI) can influence both human health and functioning of electrical appliances. An EMI map is an important instrument for monitoring the health exposure limits versus the standards. In order to draw an EMI map measurement methodologies and advanced computational models are required. In case of high voltage (HV) and or medium voltage (MV) substations the numerical simulation has several advantages because it does not require investment in measurement devices and operative personnel and can easily analyze complex working scenarios covering both substation yard and its neighborhoods. Examples of numerical simulations are presented on the 3D model of the 110/20 kV substation named Biharia in order to visualize the electromagnetic field and to make comparisons with the professional human exposure limits.

Numerical analysis of electro-thermal behavior and optimization of the cooling system in electronic power devices using CAD/CAE tools

Due to ongoing push of technology to smaller dimensions and higher computational speed of the electronic devices, a higher heat generation on device is obtained, increasing the thermal management challenges. This paper proposes a study of the electro-thermal behavior in electronic power devices and the optimization of the cooling system in order to increase the lifetime of the device. Different heat-sink designs for L298N Dual H-Bridge are proposed in this article. For each testing design of the heat sink two problems need to be solved: the electrical process model, which provides the power dissipation of the system, and the thermal process model, which provides the temperature distribution. The thermal analysis results and the optimal design of the heat sink are modeled using CAD/CAE specialized tools.

A two layer ground computational model for the numerical simulations of the earthing systems

A two layer ground model for the computation of the earthing systems is presented. The model combines the pipe element method with multiple image technique by using a fundamental solution defined for the two-layered three-dimensional (3D) half space. The model couples two problems: an external one that models the phenomena that occur in the soil - solved with the boundary element method (BEM), and an internal one that models the potential distribution in the buried metallic structures - solved with the finite element method (FEM). In order to evaluate the two layer ground computational model, the resistance-to-earth is computed for three particular earthing systems (vertical rod, horizontal rod and gradient control mat) and compared with the analytical solution. The earth potential rise (EPR) in case of the gradient control mat is represented.