Fractional model of magnetic field penetration into a toroidal soft ferromagnetic sample
Résumé
We propose an original approach to solve the coupled problem of alternative magnetic field penetration inside a toroidal soft ferromagnetic sample and frequency dependent magnetic hysteresis. Local repartition of ferromagnetic losses depends on the instantaneous material properties and on the frequency of the excitation field waveform. A correct solution to the model, with respect to this repartition, implies a higher resolution in two dimensions of the diffusion equation including local dynamic hysteresis consideration. The resulting model gives precious local information but requires complex parameter setting, high computational capacity and long simulation time. Due to the toroidal shape, a single dimension algorithm solving of the diffusion equation is clearly insufficient and it would lead to inaccurate simulation results. Consequently, a large number of discretization nodes and extended simulation time must be considered in two dimensional configurations. In our alternative solution, starting from a lumped model, we add a fractional time derivative of the dynamic hysteresis losses. It leads to an accurate formulation of the problem with a reduction in complexity and simulation times.