Study On Modeling Of Vector Magnetic Properties In Electrical Steel Sheet

The research on modeling of magnetic properties of electrical steel sheet is regarded as one of the current hot issues in computational electromagnetism. It includes three aspects. The first is to construct the proper mathematical model of magnetic properties. The second is to study the measurement device and method corresponding to the mathematical model of magnetic properties. The third is to study the numerical calculation method of electromagnetic field coupling with the model of magnetic properties. The target of this research is to accurately estimate the distributions of flux and iron loss in the iron core of electromagnetic device by taking the vector magnetic properties of electrical steel sheet under actual operating conditions into account, furthermore based on this research, to optimize the design of electromagnetic device in order to decrease the iron loss and local overheating to improve the security of the device. The study is developed around the three aspects in this dissertation.For this purpose, several typical magnetic property models are analyzed and their disadvantages are discussed. Because that for the vector magnetic property models such as E&S model, the vector magnetic properties of electrical steel sheet under the arbitrarily alternating and rotational flux condition is needed to measure. The two dimensional (2D) magnetic properties measurement method is investigated. The2D rotating magnetic property measurement system is designed and the feedback control of measurement system is realized by the criterion of sinusoidal magnetic field. The2D vector magnetic properties of a nonoriented electrical steel sheet and a grain-oriented electrical steel sheet are measured.Focused on the insufficient of E&S vector magnetic property model, an improved E&S model is proposed. In this model the coefficients are derived basing on the measurement data of rotational magnetic property. In order to retain the advantage of saving time of time-harmonic method in finite element analysis (FEA) and consider the alternating flux condition and rotational flux condition, a complex E&S vector magnetic property model is proposed. In this model, the effective magnetic reluctivity coefficients and the effective magnetic hysteresis coefficients are introduced to describe the vector magnetic property of electrical steel sheet.The methods of coupling the magnetic property model with FEA are investigated and the discretized formulation of FEA is derived. The computer programs are developed based on the FORTRAN language and the different calculating models are adopted. For the nonoriented electrical steel sheet and the grain-oriented electrical steel sheet, two core models are designed and calculated with FEA. By comparing the calculation results, it indicates that the two proposed methods are rational in theory and correct in computer programs. Besides, by comparing the two proposed methods with conventional one, it proves that the calculated results using the two proposed method are more reasonable.In order to revalidate the two proposed methods, a three phase transformer core model is designed and made. The distribution of local flux in the core model is measured by embedding the test coils. Comparing the calculated results of no-load operation with experimental ones, the validity of the two proposed methods is proved.