Measurements and modeling of the effects of an orthogonal bias field on properties of isotropic magnetic materials

摘要

The effects of the orthogonal bias field were investigated systematically in this study. The measurements on various magnetic materials under different experimental conditions showed that the orthogonal bias field rotated the hysteresis loop reducing permeability and reduced its enclosed area. As a result, permeability, hysteresis loss, coercivity and remanence decreased with increasing orthogonal bias field. The experimental results indicated that the orthogonal field reduced hysteresis loss by increasing the component of reversible domain rotation magnetization;In the present study, the Jiles-Atherton model has been expanded to include the effect of an orthogonal bias field. Based on the experimental observation, a dynamically variable reversibility coefficient was proposed to include the reversible domain rotation magnetization in the model. This models the change of the reversibility coefficient during the magnetization process and is characterized by an irreversible field range. After incorporating an orthogonal anisotropy and the dynamic reversibility coefficient into the model, the modeled hysteresis loops showed all experimentally observed features and were consistent with the results of measurements on a ferrite toroid;Based on measurement results on a circular button ferrite inductor developed in this study, a prototype un-gapped variable ferrite inductor, which utilizes selected saturation to increase energy storage and can be controlled by an orthogonal current, was proposed in this study. The measurements on an assembled prototype rectangular button ferrite inductor based on the above design confirmed the expected behavior. The measured inductance was observed not only to decrease with increasing orthogonal current, but also with an appropriate choice of orthogonal current the inductance only has a small fluctuation within a designed excitation current range;Finite element method was extensively used to analyze and model problems involved in this study. 2D linear FEM modeling was used to evaluate the internal orthogonal field along a toroid axis and flux line distribution of magnetic devices, while 3D nonlinear FEM modeling was successfully used to study the evolution of the saturation regions of variable inductors and to model the terminal inductance of the variable inductors.