Research On The Magnetic Property Prediction Of Soft Magnetic Materials Under Complex Excitations

Soft magnetic materials have been extensively utilized in the production of iron cores for electrical equipment such as power transformers and motors due to their excellent ferromagnetic properties.However,their inherent hysteresis characteristics have an significant impact on the analysis of loss and heating characteristics.With the application of large scale electronic devices in ultra high voltage(UHV)transmission programmes,harmonics and DC biases are inevitably generated inside the converter transformer,which makes it hard to predict the magnetic properties of the iron cores.Furthermore,there is partial rotating magnetic field at the "T" joint and corner of the transformer cores,which makes it necessary to consider the vector distribution properties of the magnetic field inside the materials.In this paper,the hysteresis characteristics modeling and prediction for the soft magnetic materials under different complex excitations are studied.The research in the paper is sponsored by the National Natural Science Foundation of China(Grand No.51777073,52177006)and the National Key Research and Development Program of China(Grand No.2017YFB0902703).An improved parameter identification method is proposed on the basis of the concentric hysteresis loops to realize the classical scalar Preisach model for the defect of using traditional numerical method.The magnetic characteristics of oriented silicon steel sheets(27ZH95)under different complex excitations were measured by the BROCKHOUS magnetic performance experimental platform.Based on the unification of loss statistics theory and field separation,a dynamic hysteresis model is proposed to predict the magnetic performance under the excitations of multi-harmonic and AC-DC hybrid excitation.The static part is realized by the Preisach model,and the influence of magnetic flux density amplitude,magnetization frequency and DC-bias magnetic field are considered in the dynamic part.Based on the classical vector Preisach model,the vector magnetic characteristics of soft magnetic materials under rotational magnetization are researched.The classical vector model is improved for its deficiency by taking the anisotropic characteristics of soft magnetic composites(SMC)into account.The improved model regulates the curve shape of magnetic field strength by utilizing the parameters related to its amplitude and direction angle.The static concentric hysteresis loops in direction x and y were experimented to structure the corresponding scalar and vector Everett functions.A hybrid optimization strategy based on particle swarm(PSO)and Powell technique is proposed to identify the parameters of the vector Preisach hysteresis model efficiently,which significantly improves the parameter extraction accuracy.The predicted results of the proposed model under different complex working conditions are compared with the measured ones,which indicates great consistency.The above research lays the foundation for in-depth research on the complex magnetic characteristics of the transformer cores.