Flux penetration in two dimensions into saturating iron and the use of surface equations

A mechanism of flux penetration in two dimensions into saturating iron is described when the B/H characteristic can be represented by a step function. The description is an extension of the wavefront method used by earlier authors to describe 1-dimensional penetration. Field computations using a differential method have been used to illustrate the process, and surface equations are developed which remove the need to compute within the material. Results obtained using these equations are compared with those from the full computation of the whole region, and the error arising from using only the 1-dimensional model is illustrated. A composite surface equation which can be used to represent materials having real B/H curves is also developed.