EDDY-CURRENT INTERACTION LOSS OF RANDOMLY DISTRIBUTED MAGNETIC DOMAIN-WALLS WITH SPEEDS IN FIELD EQUILIBRIUM

Eddy current losses are calculated for a domain model of Pry & Bean [1] type in which the domain walls are distributed randomly with mean spacing W across a lamination of thickness D. Two cases are considered. In the first, all walls are constrained to reverse flux at the same rate. The resulting eddy loss exceeds the “classical” loss (for uniform dB/dt) by a factor ηo+l where no= 1.628W/D is the value in the limit of negligible wall-to-wall eddy overlap. This confirms earlier work [2] and Bertotti’s role [3] that independent random eddy interactions between walls make a claasical loss contribution. In the second case, each wall adjusts its individual flux rate to balance the eddy current drag against the applied field pressure. A lower loss ratio ηA=ηo+η1results. η1decreases from 1 for W≪dto 0.7 for ≫d. This is contrary to Bertotti’s rule that correlated magnetic activity enhances eddy current loss [3]. © 1990 IEEE