Excess Loss Modeling in Ferromagnetic Materials, Including Thermal Effects

With traction machines operating in high-frequency conditions, the relative importance of excess loss as a core loss component has increased, requiring a higher accuracy prediction method. The impact of skin effect on the flux redistribution is integrated on the hysteresis loss, classical loss, and the excess loss. Given the fact that the flux redistribution is linked to the electrical resistivity and the permeability of the electrical steel laminations, this flux redistribution changes with the exploitation temperature of the material in the electrical machine. The proposed methodology extends the known loss models for the excess loss by using a dedicated excess loss coefficient below and above the maximum permeability of the magnetization graph to reflect the difference in skin effect behavior. While a change of temperature from 20 ° C to 200 ° C implies a resistivity change of 70%, hence the expected impact on the excess loss is 23% (according to the square root of the inverse of the resistivity), however, the excess loss changes with 70% due to the temperature effect on the skin effect. This enhanced model performance will assist machine design efficiency and, furthermore, allows for a clear link to the physical material parameters to be established.