Step dB/dt magnetization losses in toroidal amorphous ribbon and polycrystalline cores

The losses during step dB/dt pulse magnetization reversal in a practical sized toroidal core of Fe81B13.5Si3.5C2have been measured over a range of reversal rates. The variations in loss dissipation within the core have been monitored using search coil techniques for nominal reversal rates of 0.1 and 1.0 T/μs. The variations in loss dissipation are greater at high reversal rates than might be expected from a comparison with conventional materials and can be exolained in terms of reduced domain mobility in the amorphous specimen. The non-uniform loss distribution requires that close packing is achieved to enhance thermal transfer betweem adjacent wraps to prevent localised hot spots appearing.