USE OF ENGINEERING SOFTWARES AND MODELING TECHNIQUES APPLIED TO THE MODELING OF FERRITES: EDUCATIONAL ASPECTS
Ferrites are widely used in the area of electronic industry as a magnetic core of inductors and transformers in power electronic applications such as photovoltaic solar energy. Ferrite materials show nonlinear magnetic properties such as hysteresis and saturation and come in different sizes and geometrical shapes, some simpler and others more complex. In order to study the behaviour of the ferrites we need to be able to simulate these electrical and magnetic characteristics. Modeling and computer simulations play an important role in the analysis, design, and education for students of power electronic systems. In the field of science we can find a great variety of commercial programs for calculation, modeling and simulation that can be used for educational and industrial applications.
In this article we demonstrate how in the development of the modeling procedure of ferrites it is necessary to resort to the linked use of different modeling and simulation techniques (finite elements, mathematical equations, circuit simulation, etc...). This helps us to show the students how different softwares can operate together to solve one task.
The procedure begins with the construction of the inductor that consists of a ferrite core and a coil former on which a copper wire is wound, the measurement of the magnetic properties under direct current that characterize the ferrite core and the design in 3D or 2D of the real inductor using a Computer Aided Design program (AutoCAD).
This design together with the measurements, boundary conditions and parameters to generate the adaptative mesh are used as input in a Finite Element Analysis program (Maxwell). This is done in order to compute the two nonlinear parameters (inductance and resistance) of the serial equivalent electric circuit of the inductor. These parameters are expressed as a function of the frequency and the excitation current from the linear to the saturation region.
The next step uses a scientific calculus program (Matlab), a numerical simulation program (Simulink) and finally an electronic circuit simulation program (PSIM), the three of them working linkedly. Matlab and Simulink are used together in order to numerically solve the mathematical equation that expresses the voltage across the inductor using the previously computed inductance and resistance values.
We draw the electrical circuit to be simulated in the circuit simulator PSIM and assign the input voltage and/or current excitation level. At each instant in time the Simulink program sends the excitation current value that flows through the inductor to PSIM and PSIM sends the voltage across the inductor to Simulink. Finally, the voltage, current and power waveforms of the inductor are obtained in PSIM.