Ferrite based soft magnetic composite development intended for inroad charging application

Abstract

The magnetic performance of ferrite based soft magnetic composite materials (SMCs) have been investigated for inductive power transfer (IPT) applications in roads. The magnetic permeabilities and magnetic losses of SMCs were characterized for varying ferrite particle size fractions and particle loadings. The magnetic performance of the crushed ferrite powders were 2–3 times higher than expected based on magnetic particle theory for spherical magnetic particles. Findings were confirmed by comparing the magnetic performance of SMCs made from spherically ground ferrite powders. The good agreement of magnetic relative permeability measurements and related analytic models have shown that the key parameters affecting the relative permeability of SMCs are the magnetic particle loading, the magnetic particle aspect ratio and related shape factor, and interparticle alignment. Similarly, the measured magnetic power loss densities measurements in the low field limit (μr < 100) compared well with magnetic loss models where there is an inverse relationship to the magnetic relative permeability. Therefore, the best performance for ferrite SMCs is to be achieved by maximising the magnetic relative permeability which also minimises the power losses for a given B.