Calculation and Analysis of Transformer No Load over Excitation Current Based on Magnetic Circuit-circuit Coupling Model

In order to calculate and analyze the current of transformer accurately under no load over excitation operating condition, this paper proposes a current calculation method based on the magnetic circuit-circuit coupling model. The laminated core model of product level is used to simulate the transformer core in actual working state, the no load over excitation current is measured and compared with the current obtained by the magnetic circuit-circuit coupling model, which proves the accuracy of this model. Based on this model and taking the actual transformer as an example, the over excitation current is calculated and the current harmonic content variation law is analyzed. With the increase of the no load over excitation multiple, the research results show that the distortion of excitation current becomes more serious, the odd harmonics increase faster and the content is higher, the even harmonics have a smaller amplitude and the content remains basically unchanged.