Losses in electrical sheet steel

Various experiments on the magnetic losses in sheet steel at power frequencies and flux densities are described and their interpretation is discussed. It is concluded that an important fraction of the total loss in low-loss sheet cannot be accounted for by the normal hysteresis and eddy-current mechanisms, or by modifications of the latter to allow for non-uniformity of the permeability. This extra loss seems to be due to the finite velocity of domain wall movements, but it is not clear what mechanism limits this velocity; microscopic eddy currents induced by the wall movement are suggested as a possible cause.