Analysis Of Iron Loss In Transformer Core Based On Magnetic Reluctivity Tensor Model

This subject is from the National Natural Science Foundation of China, that is "The fine simulation of comprehensive electromagnetic properties of the electrical steel sheet and its composite structures in the computational electromagnetics" (under Grant 50777042), and "Measurement and modeling of three-dimensional hysteresis property of ferromagnetic materials" (under Grant 50807039).In the machines and transformers'core, the magnetic filed consists of both alternating and rotating magnetic flux, and thus the iron core loss is composed of alternating loss and rotating loss. Owing to the limited measurement technique, the computation on the iron core loss based on the conventional magnetic property model is not accurate enough to the design of electrical equipments, which result into the overheating at the local parts. Therefore, it is very important for the fine design of electrical equipments to develop the measurement and modeling of the electrical steel sheet under rotating magnetic flux. Under this background, in this paper, a magnetic reluctivity tensor model based on the two-dimensional (2D) magnetic property measurement technique was studied, and the magnetic field distribution and loss analysis were calculated, the main research work is as follows:Firstly,2D magnetic property measurement apparatus and methods are introduced briefly, and two popular mathematical model describing the magnetic property of the electrical steel sheet, i.e. E&S model and |B|-θB model, are analyzed in detail. The main advantages for them are discussed.Secondly, by utilizing the measuring system of two-dimensional magnetic property of electrical sheet steel, the measurement data were analyzed, and a fully magnetic reluctivity tensor model considering the rotating magnetic property was developed. Because the magnetic parameters in this model depended greatly on the measurement data, in this paper, the coefficients in this model were analyzed and drawn considering different rotating magnetic flux locus. At the same time, in order to facilitate the coupling with the finite element analysis, the measurement data were interpolated. At last, the finite element analysis formula coupled with the magnetic reluctivity tensor model, in which the rotating magnetic property was taken into consideration, was deduced, and the corresponding FORTRAN program was compiled. The three-phase transformer core model was taken as an example, and the magnetic flux line and the distribution of the iron loss were shown.