Eddy Current Loss in Grain-Oriented Steel Laminations Due to Normal Leakage Flux

Leakage flux penetrating laminated iron cores in power transformers and large generators induces eddy current and local loss. Due to the strong magnetic anisotropy of the lamination structure, the penetrating flux tends to saturate the lamination in its plane, even when the incident stray flux density is low. Therefore, the combined effect of anisotropy and nonlinearity has a great impact on the eddy current distribution and the associated power losses. Moreover, the incident normal flux often interacts with the main flux, where the phase angle between the two fluxes may play a significant role. A measurement device is developed to emulate the actual leakage flux in a steel lamination and the power losses are measured at the flux densities of various magnitudes and phases. The measurement results are compared and interpreted by the results obtained from a finite-element analysis, where the homogenization approach for material modeling is implemented, taking the combined effect of magnetic anisotropy and the saturation into account.