Simulation of Losses in DC-Biased Single Phase Three Limb Transformer

According to the characteristics of electrical connection in the single phase three limb power transformer model, an equivalent coupled electric and magnetic circuit was established to calculate the excitation current of DC-biased power transformer model and analyze the changes of excitation current with the DC bias voltage effectively. Based on the finite element theory, the internal magnetic field distribution of the transformer under DC bias condition was analyzed in detail by taking account of excitation current. Moreover, the thesis discussed the magnetic flux density distribution as well as changes of additional loss in transformer with increasing DC bias level. The results show that the core saturation becomes higher and the excitation current distortion is more serious with low harmonic sharply increasing when the DC current of the transformer increases. The simulation results of losses are in accordance with the theory, confirming the validity of the proposed losses calculation method for transformer under DC-biasing. The relevant conclusions provide a reference for the design and maintenance of the transformer considering DC bias.