Influence of the Induction $\boldsymbol {B}(\boldsymbol {t})$ Shape on Hysteresis and Loss Measurements of Soft Magnetic Materials

The frequency dependence of the hysteresis loop of high-pressure torsion treatment (HPT)-deformed Fe
₇₅
Al
₂₅
, industrial steel Fe-3wt%Si, bulk Fe-3wt%Si plates, and nanocrystalline VP800 was measured on ring-shaped samples. Applying a sinusoidal or triangular H(t) delivers a strong frequency dependence of the losses. A sinusoidal or triangular B(t) reduces the total loss [this reduction is larger for triangular B(t)] and the dependence of loss on frequency becomes smaller. Our results are discussed in terms of Bertotti's loss separation model. For HPT-deformed Fe
₇₅
Al
₂₅
, the total loss W linearly varies with the square root of frequency when a triangular H(t) is applied; however, no significant change in the total loss was found for a triangular induction B(t) up to 500 Hz. The hysteresis, classical, and excess loss values of the Fe-3wt%Si steel plates are different from those of bulk Fe-3wt%Si for all H(t) and B(t) shapes due to different microstructures. In nanocrystalline VP800, the contribution of classical eddy current loss to the total core loss is very small due to high resistivity and small ribbon thickness.