Investigation of the electromagnetic simulation results variation of a hydro electrical generator

The electromagnetic modeling and simulation of existing hydro electrical generators in operation always require a large number of variables to carry out an accurate study and to be able to properly validate the different test results. Simulation can be affected by parameters, such as: the model meshed density; the magnetic materials (magnetic proprieties are usually unknown); the air gap size (the design air gap is always different from the operation air gap due to the thermal expansion) and its uniformity. The excitation current calculated during simulation to achieve the proper line current depends on the air gap and the magnetic properties at the fundamental frequency and its harmonics. This paper reports a FEM simulation of an existing hydro generator of 122.6 MVA, 13.8 kV, 60 Hz, 60 poles with 504 slots, considering the magnetic material, mesh size, air gap length and excitation current as variable inputs. The impact of the modification of these parameters on the electromagnetic finite element simulation is presented, besides, the simulation results were compared with test ones.