The losses and temperatures of end parts will increase obviously in the turbogenerator end region under underexcited operation. In order to study the influence of different underexcited operations on temperature of end parts in the turbogenerator end region with magnetic shield structure, a turbogenerator is considered as an example in this paper. Three-dimensional transient electromagnetic field of turbogenerator end region is given. The magnetic density distribution of clamping plate and magnetic shield is researched. The losses of end parts and stator end cores from three-dimensional transient electromagnetic field calculation are applied to end region as heat sources under different underexcited operations. Pressure value of fan outlet and velocity values of different inlets from flow network calculations are applied to end region as boundary conditions in the 3-D fluid and thermal coupling analysis model. Further, fluid field and thermal field are calculated under different underexcited operations. The distribution laws of fluid velocity and fluid temperature in the turbogenerator end region are determined. The temperature distribution laws of the stator-end copper windings, press finger, clamping plate, screen plate, magnetic shield, and stator end cores are studied under different underexcited operations. The accuracy of numerical calculation is validated by measured values. (C) 2019 Elsevier Ltd. All rights reserved.