An electronic coercivitimeter for amorphous ribbon toroids

Abstract

The constant current flux reset (C.C.F.R.) method has been frequently used to measure the coercivity Hc, remanence Brem, and saturation flux density Bmax, of nickel-iron alloys. A new electronic coercivitimeter has been constructed based upon the C.C.F.R. method, which is capable of measuring the properties of amorphous ribbon toroids. The mode of operation and circuit of the coercivitimeter will be fully described. The coercivity and remanence to maximum induction ratio, Brem/Bmax, of amorphous ribbons of Co58Ni10Fe5Si11B16 and Fe81B13.5Si3.5C2 which have been forward wound, i.e., with the wheel side of the ribbon on the side of the toroid and reverse wound, i.e., with the wheel side of the ribbon on the outside of the toroid, have been measured. The measurements presented have been made over the frequency range 50 to 1000 Hz and for toroids field annealed under different conditions, i.e., temperature from 325 to 425 °C, in air, nitrogen, and hydrogen atmospheres. It is found that the coercivity increases and the Brem/Bmax ratio decreases as the frequency increases. These experimental results are explained by considering the effect of annealing conditions and frequency on the domain structure, B/H loop, metallurgical properties, manufacturing stresses, and induced anisotropies of amorphous ribbons.