ABSTRACT
In this paper, a novel coupled model, which includes the electric circuit and the magnetic circuit of the three-phase three-legged transformer under Direct Current (DC) bias, is built. In a magnetic circuit model, the eddy currents, the iron core topology, and the saturation characteristics of the core material are taken into account. The magnetomotive forces due to the eddy currents are given in the magnetic circuit equations. By combining the electrical circuit with the magnetic circuit and considering the non-linear characteristic curve of the iron core, the non-linear equations can be obtained. A series of mathematics transformation is performed and the numerical non-linear algebraic equations are solved. And then, the experimental work of the three-phase three-legged transformer under DC bias has been carried out. Finally, the simulation results and the experiment results are compared. They are in good agreement. Meanwhile, the DC bias problem on the three-phase three-legged transformers is analyzed. It demonstrates the validity of the simulation model and the accuracy of analyzing the DC bias phenomenon of the three-phase three-legged transformer.
