Influence of higher harmonics in the end region magnetic field on eddy currents in the stator clamping system of hydro generators

The reliability of the loss calculation is a very important issue during the electrical design phase of hydro generators. Therefore, the accurate calculation of eddy currents in the stator clamping system is a matter of particular interest with initial design and design optimization. Due to the nonlinear magnetic behaviour of the clamping plate, the eddy current losses in these regions can reach high values and produce local thermal hot-spots. The calculation results obtained from 3D time-harmonic and 3D non-linear transient finite element analyses of a 450 MVA hydro generator are compared with regard to local and total eddy current losses. Thereby, special attention is given to the influence of higher harmonics in the excitating end region magnetic field