Influence of Metal Screen Materials on 3-D Electromagnetic Field and Eddy Current Loss in the End Region of Turbogenerator

Since the structure of a large capacity turbogenerator is complex in the end region, accurate calculation about the leakage magnetic field becomes a key factor in the design. In this paper, a 330-MW level turbogenerator is electromagnetically analyzed and investigated with different metal screens in the end region. Its nonlinear transient electromagnetic field and eddy current loss were calculated by using the time step finite-element method (FEM). The influences of metal screen materials on the electromagnetic field and eddy current loss were compared and analyzed. All of these will contribute to the turbogenerator engineering design. Using the loss gained by the magnetic field calculation as a heat source, the thermal field of the end region with a copper screen was calculated. Compared with the test data, the calculated temperature results match well with the measured data.