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R.A. Salas Merino, J. Pleite Guerra

Universidad Carlos III de Madrid (SPAIN)
Power electronics is a multidisciplinary subject, taught in universities at both Bachelor and graduate levels, which covers many areas such as electronics, electromagnetics, power systems, simulation and computing and so on. Although this is an attractive area for students it can be sometimes difficult for them to grasp. Many of the circuits used in power electronics include inductors that consist of a ferrite core, a winding of copper wire and sometimes a coil former. The modeling of the ferrite inductors is a complicated task due to the nonlinearity of the magnetic fields and the great variety of shapes, sizes of the core and number of turns in the winding. Therefore, it is necessary to resort to modeling and simulation techniques as well as experimental measurements to understand circuit operation and obtain enough information to achieve a robust design. Modeling and simulation are essential ingredients of the analysis and design process in power electronics.

We present a methodological procedure that combines modeling, simulation and experimental measurements on real inductors.
We apply this procedure to the modeling and simulation of ferrite inductors. These inductors are widely used in the field of power electronics. Our methodology can be applied to Bachelor and graduate students to help them understand the behavior of typical circuits such as power converters and the nonlinear physical phenomena involved in power electronics.
This procedure is based on the use of different programming and modeling techniques coupled together: A Computer Aided Design program (AutoCAD), a Finite Element Analysis software (Maxwell), two scientific calculus programs for the numerical solving of derivatives and integrals (Origin and Matlab), numerical simulation program (Simulink) combined with Matlab, and finally, an electronic circuit simulation software (PSIM). An alternative would be to use the software OpenCascade, FreeFEM, Scilab and so on with the same methodology.

As the procedure is very laborious and complex, we have decided to divide it into four levels with growing complexity that can be applied to students at different educational stages. These levels are the following.
The first and second levels can be used for Bachelor students and the third and fourth levels for graduate students.
The first level consists of four activities: design and construction of the inductors and transformers, preliminary experimental measurements at low current intensity, DC current experiments and AC current experiments. These activities can be suggested as optional additional work for the subject. The optimal organization would be individual or groupwork. The second level focuses on the design, analysis and simulation of the inductors with ferrite cores using Finite Element Analysis. In general, the software based on this analysis has a visual interface and provides a physical and extremely useful perspective which helps students understand concepts that are difficult for them. As the simulations can be carried out in 2D or in 3D the instructor can propose different geometries and compare the 2D to 3D results. For the third and fourth level we proposed applying the full procedure to a specific geometry and validated the results with experimental measurements for the case of a sinusoidal waveform or square waveform. This latter case is of great interest in power converters.