Development of a New MnZn-Ferrite Soft Magnetic Material for High Temperature Power Applications

At power electronic applications (e.g. in automotive, lighting, electrical equipment etc.) the inductive components that consist the heart of the power transformers are made of ceramic ferromagnetic materials of the type (MnxZnyFe2 +1 − x − y)Fe3 +2O4. Usually they are designed in such a way in order to exhibit optimum magnetic performance and electromagnetic power loss minimum at 80–100∘C, which is the steady state operation temperature region for most devices. However, the continuous miniaturization of electric and electronic equipment associated with a continuous increase in the density of electronic components has as unavoidable consequence the gradual shift of the steady state operation temperature to higher levels. The need is therefore becoming obvious for the development of new power soft magnetic materials optimized to operate at higher temperatures than those at which current existing materials operate. In the present work the development is described of such a new soft ferrite material having the chemical composition (Mn0.76Zn0.17Fe2 +0.07)Fe3 +2O4, initial magnetic permeability of 1800 (measured at a frequency f = 10 kHz, an induction level B < 0.1 mT and a temperature T = 25∘C), Curie temperature of 225∘C and electromagnetic power losses < 350 mW/cm3 measured at a temperature of 140∘C, frequency of 100 kHz and a magnetic field strength of 200 mT. The material has been successfully introduced to production and is now commercially available. The largest application is offered by the automotive industry in particular for tackling high temperature operating problems arising when control is being done near the engine (near the engine electronics).