Eddy current losses in ferromagnetic laminations

It is demonstrated through the comparison of analytical, numerical, and exp erimental results that the existence of excess eddy current losses can be e xplained by the peculiar nature of the nonlinear diffusion of electromagnet ic fields in magnetically nonlinear laminations. The essence of this peculi ar nature is that nonlinear diffusion occurs as inward progress of almost r ectangular profiles of magnetic flux density of variable height. Approximat ing actual profiles of magnetic flux density by rectangular ones, the probl em of nonlinear diffusion can be treated analytically by using a simple mod el. The accuracy and the limit of applicability of the rectangular profile model are discussed by comparing its predictions with finite elements numer ical solutions of nonlinear diffusion equation as well as with experimental results. (C) 2000 American Institute of Physics. [S0021- 8979(00)24808-1].