Measurement and Modelling of Magnetic Properties of Fe-based Amorphous Magnetic Material

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Fe-based amorphous magnetic materials are attracting more and more attentions in the low and medium frequency electrical machines and transformers due to their favourable properties of low core loss and high saturation magnetic flux density. In this study, the core loss of a Fe-based amorphous magnetic material (amorphous 1k101) is measured and modelled under alternating and rotating magnetic field excitations. In particular, for numerical analysis using the vector magnetic potential under alternating magnetic field, an inverse magnetic hysteresis model is needed to predict the magnetic field strength from the magnetic flux density. This study proposes a generalised inverse Preisach model for characterisation of the magnetic material which considers the reversible magnetisation and magnetisation dependent hysteresis effect. Thus, the proposed inverse Preisach model improves the accuracy of the prediction of core loss compared to the normal inverse Preisach model. In addition, a modified Jiles-Atherton (J-A) model is utilised for modelling the magnetic material which eliminates the drawbacks of the inverse Preisach model such as high computational time and memory requirements. The implementation of J-A model is associated with model parameter identification which is generally carried out by different optimisation techniques. In the optimisation techniques, an additional error criterion along with conventional error criterion for the identification of the J-A model parameters is proposed in this study which improves the core loss prediction. Furthermore, a modified J-A model is proposed to improve the agreement between experimental and calculated results especially at the low magnetic induction levels by introducing a scaling factor in the anhysteretic magnetisation. Both the proposed inverse Preisach model and modified J-A model are verified by the results obtained from experimental methods and existing modellings in the literature. Moreover, the rotating (two-dimensional) magnetic properties of the Fe-based amorphous magnetic material is experimentally investigated in this thesis where a square specimen tester is exploited for experimental measurement. For modelling of the rotational hysteresis loss, an improved and simplified analogical model is proposed and verified for the magnetic material. The total specific rotational loss of the amorphous magnetic material for both circular and elliptical rotating magnetic fields are measured and modelled. Furthermore, an optimal design of a high-power density medium frequency transformer (MFT) using the Fe-based amorphous magnetic material is presented in this thesis where the effects of magnetisation current is considered in the design process. A prototype of the MFT is utilised for the experimental verification of the design.
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