Nonlinear magnetisation in thin ferromagnetic plate

In ferromagnetic circuits, a problem of interest is the predetermination of the time required for complete magnetisation of the material under impact excitation. The time of magnetisation gives an indication of the rapidity of response. Rigorous solutions of the problem are available in the literature for constant permeability and sections of simple geometry. For a nonlinear case of variable permeability, it is well known that an analytical description of the behaviour is extremely difficult. The problem of nonlinear magnetisation has applications in electrical machines, pulse transformers, magnetic memories and magnetic shift registers. The paper presents nonlinear analysis of the problem for a step m.m.f. excitation, using Maxwell´s equations. For easy handling by practical design engineers, assumptions are made to obtain the final equations in a simple form. The results based on these equations are then compared with those of the painstaking graphical solution of the same problem. The favourable agreement justifies the assumptions made in obtaining the solution of the complex nonlinear problem. It is also shown in the paper that, for quick approximate computations, the author´s previously reported equivalent circuit can be successfully used.