Advanced testing and modeling of magnetic materials including a new method of core loss separation for electrical machines

This paper presents a new method for the separation of core loss components (hysteresis and eddy current) in laminations exposed to high frequency excitations. Accurate separation of core losses is achieved by calculating the hysteresis losses at each frequency taking into account the non-uniform flux distribution inside the lamination. The results highlight that the assumption of constant hysteresis energy loss per cycle is only valid at low frequencies, where skin effect is negligible. The developed model is then used to study the effect of the annealing process on core loss components in laminations exposed to high frequency excitations. Core loss measurements are performed on different laminations at several frequencies in the range of 20 Hz - 4000 Hz. A comparison of the separated core loss components shows that a huge reduction in the hysteresis loss is achieved by annealing, while the annealing process increases the eddy current loss component at high frequencies and high flux densities. The results are then analyzed by comparing the separated eddy current loss with an analytical eddy current loss model that accounts for the non-uniform distribution of the magnetic field.