Empirical equations for the magnetization curve

AN EQUATION of the form μ = PB^a has been derived experimentally, where μ represents permeability and B represents flux density. This equation closely reproduces the flux density-permeability curve for magnetic materials of various compositions and qualities in the flux range of approximately 80 to 6,500 gausses. The data, obtained in the usual way from averaging samples, is graphed on log-log paper using μ/B² versus B, the latter being the independent variable. The coefficient P and exponent a are determined by graphical and analytical means, both being influenced by the nature of the material, the former being indicative of the relative value of the initial permeability. Several curves and data sheets show the salient features of the method and accuracy in reproduction. A list of various grades of silicon steel and alloys is included to illustrate the values P and a may have, and the range over which the equation holds.