Factors Affecting the Accurate Prediction of Iron Losses in Electrical Machines

A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multi-frequency Epstein tests is described and examples are provided for three typical grades of non grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20 Hz and 400 Hz and inductions from 0.05 T up to 2 T the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed and examples from an interior permanent and an induction motor are included