Analysis of the Electromechanical Characteristics of Power Transformer under Different Residual Fluxes

Abstract

When the electromagnetic transients occur in a power transformer, an inrush current is generated in its winding. The inrush current not only affects the performance of the transformer windings, but also affects the lifetime of the transformer. Many factors affect the inrush current, the most influential ones among which are the closing phase angle and the residual flux. In this paper, a dry-type transformer simulation model is built to analyze the influence of the inrush current on the performance of transformer windings during no-load reclosing conditions. Firstly, the inrush current was generated in the transformer windings during the no-load reclosing operation under different residual fluxes. Secondly, the field-circuit coupling 3d finite element method is used to analyze the electromagnetic force at different locations of the transformer windings under the influence of different inrush currents. The results of winding structural parameter variations are obtained through electromagnetic-structural coupling simulation, and the electromagnetic forces are used as the input parameter for the structural analysis. Finally, the residual flux is generated by controlling the opening and closing angle of the transformer through the phase-controlled switch, and the winding electromechanical characteristics are tested under different residual fluxes. Finally, comparisons of the test and simulation results are drawn to verify the impact of the closing angle and residual flux on inrush current and the winding deformation during the no-load reclosing conditions.

Study on the Uniformity of Temperature Distribution of Transverse Flux Induction Heating Based on a New Magnetic Pole

“…The two-dimensional plan of the induction heater with the new magnetic pole is shown in Figure 7. Because the magnetic flux will flow along the path with small magnetic resistance in the magnetic circuit [17], the magnetic flux generated by the heater coil passes through the air gap between the pole and the strip only once in the process of flow through the new magnetic pole, so the proportion of air in the magnetic circuit decreases, and the magnetic resistance of the alternating magnetic field through the magnetic circuit decreases. In conclusion, the effective value of the alternating magnetic field used to heat the strip in the induction heater with the new magnetic pole is large, which makes the heat source of the heating strip large and the temperature of the strip high.…”