Saturation flux density and DC bias
Saturation flux density Bs sets the DC bias limit: silicon steel ~2.0 T, nanocrystalline ~1.2 T, MnZn ferrite ~0.4–0.5 T. For DC-biased inductors, a gapped silicon steel or nanocrystalline core usually beats ferrite on size.
Rule of thumb
Work out the DC magnetising force H = N·I/le, then check the material curve. Keep operating flux below 70–80% of Bs for stable inductance.
