Study on Amplitude and Frequency Characteristics of Magnetic Flux in Three-Dimensional Wound Core Transformer

Abstract

In order to deeply study the mathematical model and amplitude-frequency characteristics of the split-frame flux and composite flux of a three-dimensional wound core transformer. Firstly, based on the phasor relationship between the composite flux and the split-frame flux, this paper obtains the constraint equation between the composite flux and the split-frame flux. Based on Ohm's law for magnetic circuits, the constraint equation between the three-phase frame fluxes are derived, and the analytical solution of each split-frame flux is obtained by solving it. Secondly, combined with the characteristics that the flux distribution in the magnetic circuit always realizes the minimum magnetic resistance, starting from the relationship between the harmonic content, initial phase angle and the amplitude of the composite flux in the analytical solution of the split-frame flux, a calculation method for the harmonic content of the split-frame flux and the amplitude of the composite flux of a three-dimensional wound core transformer based on the multivariate function method is proposed. The harmonic content of the split-frame flux and the amplitude of the composite flux under excitation of an infinite power system and a small power system is clarified, and its typical applications are discussed. Finally, a test platform for a three-dimensional wound core transformer capable of realizing the presence or absence of zero-sequence flux components in each frame flux is built and relevant tests are carried out to verify the correctness of the proposed method.