A four-component model for high-μ ferrites

New models for the components of complex permeability are proposed to explain experimental measurements of inductors wound on high-permeability ferrite toroidal cores. In order to represent ferrite properties more directly, parallel instead of series complex permeability is used. The quantities μ\´_p and μ"_p are modeled for their asymptotic low-frequency property as well as for their frequency-dependent behavior. Low-frequency data for μ\´ _p versus induction, B, are reasonably matched by a parabolic curve, whereas the reciprocal of μ"_p B shows a distinctive linear dependence, which is a new finding. To explain it, the authors conjecture the existence of B-induced conductivity. The frequency dependences of μ\´_p and μ" _p were measured at three different levels of B. Each component appears to roll off at high frequency from a constant low-frequency value. Computer-aided polynomial curve fittings were used to quantify the data. Snoek\´s limit values are tabulated