Space‐time correlation properties of the magnetization process and eddy current losses: Applications. II. Large wall spacing

摘要

The physical processes controlling the behavior of dynamic losses in oriented materials are analyzed on the basis of a general statistical theory of losses developed in preceding papers. In contrast to the Pry and Bean model, the case of a system of statistically independent walls, in which dynamic wall‐wall interactions are neglected, is considered. In this approximation, the basic parameter controlling the loss behavior turns out to be the surface Q~ of active walls participating in the magnetization process at different magnetizing frequencies fm. A simple model is developed, starting from the observation that it is the applied magnetic field that essentially controls the increase of Q~ with increasing fm. Since the applied field governs, at the same time, the velocity of the moving walls, a competition between wall velocity and active wall surface changes is predicted, which leads to a nonlinear dynamic loss behavior. The obtained loss expression represents a simple generalization of the Pry and Bean model, capable of taking into account, in an approximate but unified way, the various mechanisms, such as the presence of irregularities in the wall motion, domain refinement, and wall bowing, which strongly affect the behavior of dynamic losses in oriented materials.