The predictions of the different magnetic core losses with acceptable accuracy are key parameters for temperature-rise calculations for any considered up-rate in large hydro electrical machines. In this paper, an overview of existing magnetic core loss models is reported. A new approach for the computation of the magnetic stator and rotor core loss is proposed. Finite element electromagnetic simulations were carried out on an existing hydro electrical generator rating 122.6 MVA, 13.8 kV, 60 Hz, 60 poles with 504 slots. The magnetic core losses were computed with the new proposed approach during the post processing in the stator and in the rotor. Finally, the obtained results are compared with other models and with the available test data.