Losses and forces due to eddy currents in a magnetically non-linear conductive half space

Abstract

A simple soft magnetically non-linear moving conductor model (“iron”) as “half-space” is presented under the inducing effect of a sinusoidal distributed current loading at different current amplitudes, covering the low to very high saturation level of 1–4 T. Eddy current losses, penetration depth of field and tangential braking and normal attractive forces are compared with the results for a linear conductor with constant saturation (relative permeability 100) for a velocity range, described by magnetic Reynolds numbers 1–300. Eddy current losses and the braking force are bigger for the non-linear case (typically 160–200%) and the penetration depth is bigger by 200–400%. The attractive force is smaller, first due to field compression at higher velocity, second due to the increased saturation level, which gives lower relative permeability values than the assumed constant value of 100 in the linear case. For a rough estimate of either eddy current effects in eddy current brakes and linear induction motors with massive secondary or of eddy current losses in electrical machines and apparatus often a constant saturation is assumed. The here presented results allow a preliminary correction due to the non-linear conductor effect, before a detailed non-linear numerical analysis of the investigated geometry is done.