Permeability (µi, µmax): reading the datasheet
Initial permeability µi is measured at very low flux; maximum permeability µmax is the peak of the µ–H curve. Current transformers and RCDs need high µi for small signals, while energy-storage inductors care more about saturation flux density and DC bias behaviour.
Typical values
Grain-oriented silicon steel: µmax around 40,000–60,000 after annealing.
Nanocrystalline 1K107: µi up to 80,000–120,000 depending on annealing and coating.
MnZn ferrite: µi 2,000–15,000 depending on grade; NiZn much lower (10–1,500) but works to hundreds of MHz.
FAQ
Does higher permeability reduce the number of turns?
Yes — inductance rises with µ, so a higher-permeability core reaches the same inductance with fewer turns, which lowers copper loss and size.
