Simulation of Nanocrystalline Magnetic Cores Using Maxwell Ansys

Modeling magnetic core saturation has been of interest for various pulsed power topologies, such as those using linear transformer drivers (LTD). An extensive 3D Finite Element Method (FEM) analysis of FINEMET cores using Maxwell ANSYS is presented, aiming to align the computational model closely with experimental results obtained under varying magnetization rates obtained with voltage pulses of $\sim 10$ nanosecond rise times and $\sim 1$ microsecond duration. The study aims to elucidate the experimentally well-known widening effect of the hysteresis curve under high-frequency or pulse applications by exploring a range of model parameters, such as core conductivity, solid vs. laminations, etc., that best match the experiment. The more successful approach employs the concept of “effective conductivity” $(\sigma_{\text{eff }})$ to simulate the hysteresis shift away from a DC curve in the magnetic core due to eddy currents in the core accompanied by ohmic core losses. While this specific method does not resolve laminations, it relies on adjusting $\sigma_{\text{eff }}$ to closely match the experimental hysteresis curve for a base set of magnetization rate data. An effective conductivity value of $\sim 10 \mathrm{S} / \mathrm{m}$ using a solid core approximation reasonably matched that of an experimental laminated FT-3KL core with the pure magnetic material at $833 \text{kS} / \mathrm{m}$ conductivity. A thin oxide layer of insulation between laminations assumed $0.001 ~\mathrm{S} / \mathrm{m}$. Keeping all simulation core properties constant, the widening of the BH curve for higher magnetization rates is reproduced in the simulation, facilitating a direct comparison with the experimental data over a broader range.