Speaker
Description
Soft magnetic composites (SMCs) are a promising class of materials for high-frequency magnetic components in power electronics applications, including electric vehicle on-board chargers, DC-DC converters, and grid-tied inverters. Accomplishing higher operating frequencies than laminated steels and higher saturation flux density than common ferrites, SMCs consist of electrically insulated ferromagnetic particles that suppress eddy currents while enabling 3D flux paths, which provide great flexibility in component design. Despite these advantages, the high-frequency behaviour of SMCs — particularly those with ferrite coatings — remains critically undercharacterised in the literature, especially above 100 kHz.
This work investigates advanced ferro-ferrite SMCs in which a magnetically active ferrite phase is employed as the insulating medium. Iron and iron-alloy (Fe-Si, Fe-Si-Cr) particles will be coated with nickel-zinc or manganese-zinc ferrite. The two ferrites, chosen for their complementary resistivity-permeability trade-offs at high frequencies, are the most industrially applied ferrite materials. Different core materials introduce similar trade-offs, further complicating the selection of the appropriate core-shell material combination.
The processing route is crucial in determining the final properties of the material. SMCs are traditionally developed by the conventional two-step method of cold pressing followed by heat treatment to improve material density and relieve stresses. Benefits of more advanced methods, such as hot pressing, spark plasma sintering and cold sintering, will be evaluated, along with combinations of them.
The primary characterisation targets are magnetic performance properties, such as volumetric core loss, $P_{v}$, over broad frequency and temperature ranges, complex permeability, $μ$, and coercivity, $H_{c}$. Enhancing thermal and mechanical properties is another key demand for the incorporation of the material in real-world power electronic circuits.
A physics-based broadband loss model will be developed to account for all relevant loss mechanisms in the dual-phase microstructure: hysteresis losses in both the iron core and the ferrite shell, eddy currents, split between short-range (intra-particle), governed by skin depth, and long-range (inter-particle), propagating through the ferrite insulation, and excess losses. The model will be validated against measurements, so that it can be successfully integrated into power electronics circuit simulation tools.
This research is carried out within the Horizon EU Doctoral Network MAGNIFY, which aims to establish the foundation for modern power electronics, covering the whole chain from magnetic material development to power electronic circuit design and system-level modelling, with direct participation of five industrial partners.
Acknowledgements
This research is funded by the HORIZON.1.2 – MSCA programme (Grant agreement ID: 101226760).
