Magnetic properties of Fe-based toroidal cores prepared by continuous Joule heating under tensile stress

Abstract

Fe-based toroidal cores with a permeability value of several hundreds were prepared by the continuous Joule heating method under tensile stress at a high moving velocity of 120cm∕min, corresponding to an effective annealing time of approximately 1.8s, and their magnetic properties were evaluated. The prepared core showed a constant permeability value up to 2MHz and a low magnetic loss compared with those for conventional cores with controlled permeability. An investigation of dc-bias properties of the core suggested that the core has constant and good magnetic properties below the dc-bias field of 1kA∕m which is approximately 50% of the anisotropy field. Consequently, the continuous Joule heating under a tensile stress method at high moving velocity enables us to prepare a long annealed ribbon in a short time with simple equipment and improves productivity for the fabrication process of high performance Fe-based toroidal cores with controlled permeability.