Magnetic Flux Paths in Single Sheet Tester as Modeled Numerically

International standards assume that dissipative losses of the single sheet tester (SST) are restricted to the 450 mm long free sample region, according to negligible induction and losses in yoke and pole face regions. This article reports non-linear magnetic equivalence circuit calculation (MACC)-simulation of induction distributions, with focus on sample/yoke contact regions, for grain-oriented (GO) material and non-oriented (NO) material, respectively. Neglecting stray flux along the free sample region, it is shown that the flux of a GO-sample tends to propagate toward the center of the pole pieces, in order to enter into the yokes in distributed ways. The propagation length depends strongly on the air gap length
${g}$
from coating and pole face finishing. NO-steel shows weaker penetration, the flux going “round the corner” for small
${g}$
. As a consequence, the conventional assumption of a constant path length of 45 cm cannot be corrected. Effective adaptation of the latter to the many involved impact factors is not realistic.