Non-oriented electrical steels are sub-divided into 'fully processed'
and semi-processed' types. The history of loss reduction has generally
been associated with silicon additions for both types of steel which
unfortunately is detrimental to high field permeability. More recently
the availability of ultra low carbon and ultra low sulphur steels has
permitted a shift in the loss/permeability compromise associated with
silicon addition by adopting a 'lean and clean' approach in which los
ses are lowered by improved purity and. perhaps. thickness selection w
hilst good high field permeability is maintained by a restriction on s
ilicon additions. This paper deals with recently developed steels of t
his type, particularly 'Polycor' aimed at the high efficiency inductio
n motor marker. The changing role of insulative coatings on new materi
als is also considered. Potential further development of low loss high
permeability grades is discussed.