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. It is common practice for hydro electrical designers to compute the core losses in different section of the machine function of the flux density given only at 60 Hz by the manufacturer of the steel lamination which probably leads to inaccurate prediction of the magnetic core losses. In this paper, certain currently available core loss models are used to compute the electromagnetic core losses in large hydro electrical machine. The obtained results are discussed and compared with the available test data.