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|High Temperature Ageing of Fe-based Nanocrystalline Ribbons|
|Keywords: High temperature ageing, Soft magnetic materials, Nanocrystalline magnetic materials|
|The impact of long-term high-temperature stress on nanocrystalline Finemet materials is measured by keeping samples at 200 °C for 1300 hours. The standard industrialized high permeability Finemet materials as well as the recently available low permeability Finemet materials are investigated. Nanocrystalline magnetic materials are widely used in electrical engineering. The Finemet alloy, patented by Hitachi Metals, is the most common nanocrystalline magnetic alloy. Optimal composition and manufacturing process have almost been kept the same since the first industrialized Finemet materials in the 90’s. Power electronics is an important field of application for these materials. They are mainly used in power transformers, common mode chokes or sensors. Nowadays, power electronic converters are moving toward higher ambient temperatures thanks to an increase in maturity of the latest SiC power devices. Hybrid Electric Vehicle (HEV) or More Electrical Aircraft (MEA) projects are targeting respectively 150 °C and 200 °C as ambient temperature for commercial use. Characterizations are performed at different frequencies, temperatures and magnetic field excitations on both aged and non-aged samples. Their complex permeability is also monitored during the ageing test. Irreversible changes are pointed out on permeability, coercive field and magnetic flux density at saturation. Regarding the design considerations for high temperature power electronics, the suitability of these materials is demonstrated. However, the impact of the high temperature ageing on the design procedure has to be considered, especially for applications that must operate for long time (several years) with high reliability: space, avionics, automotive. For engineering purpose, according to these results, ageing data could be extrapolated easily with the presented ageing law. Indeed, for power electronics designers, a physical-based predictive ageing law could save experiments.|
|Christian Martin, Associate Professor
Universite de Lyon, Ampere Laboratory - UMR5005