Influence of Novel Magnetic Screen Structure on Leakage Flux, Losses, and Thermal Field in the End of Turbogenerator

The end leakage flux generated by the current in the end winding of the turbogenerator is large, which has a significant effect on the electromagnetic losses and temperature in the end region. As the capacity of the power and electromagnetic load increase, the end leakage flux increases obviously in the end of the generator. It results in the high eddy current losses in the components of the end region. The turbogenerator produces local overheating, local stress, and other problems in the end. In this paper, the mathematical model of the three-dimensional transient electromagnetic field in the end is developed for a 1407 MVA nuclear turbogenerator. The flux density distribution and losses of the end components under multi-layer magnetic screen structure are studied. A novel magnetic screen with circumferential ventilation duct (MSWCVD) is proposed. The flux density and losses of the end components are compared and analyzed under different depths and widths of circumferential ventilation duct of the multi-layer magnetic screen. The three-dimensional thermal model of the end region is proposed. The fluid-thermal coupling field of the end region of the turbogenerator is calculated and studied. The results are close to the measured values.