Representation of magnetisation curves over extensive range by rational-fraction approximations

The paper presents a simple mathematical expression which enables representation of all types of magnetisation curves over a very wide range. The equation given is ideally suited for problems which require use of the B/H curve many times, since calculations using it require only a few operations of the basic arithmetic adding, multiplying and dividing. Although the equation is not linear in all the parameters, a method for obtaining the best parameters, in which the problem is first linearised and then restored to its original nonlinear form by a system of iteration, is described. A discussion of the meaning of the best parameters of the equation to fit the data curve, whether it is to be read fromB to H, or H to B, or both ways, is given. Comparison is given between several saturation curves and their mathematical counterparts over magnetising m.m.f. from zero to, in one case, 300000AT/m.