Effects of NonUniform Copper Shielding Thickness on End Leakage Flux and Temperature Rise in Turbogenerators

ABSTRACT Magnetic flux leakage and excessive heating at the generator end are significant challenges in large steam turbine design. Copper shielding is an effective strategy to reduce end‐region magnetic losses and enhance heat dissipation. However, under leading power factor operation, leakage flux intensifies, increasing thermal stress. This study investigates the impact of nonuniform copper shielding thickness on electromagnetic and thermal performance using a 320 MVA steam turbine generator. A three‐dimensional electromagnetic model, integrated with a fluid–solid coupling thermal model, was developed to evaluate leakage flux, eddy current losses, and temperature rise under various shielding configurations. The results show that reducing the shielding thickness in the third section increases copper shielding loss by 5.12 kW compared to the baseline. The maximum temperature of the stator winding under the Type III configuration reached 63.6°C, 0.9°C higher than the baseline, whereas the peak temperatures of the copper shields increased by 3.3°C, 5.5°C and 6.1°C, respectively. The maximum magnetic flux density was 0.92 T near the pressure finger. Experimental data showed good agreement with simulations, with discrepancies below 5%. This study provides a foundation for design refinement of copper shielding, considering performance, cost and manufacturability. Future work will introduce optimisation methods to improve shielding design.