Patent ID: 7358844

Claim:
A current transformer core comprising a ratio of the core outside diameter D a to the core inside diameter D i of <1.5, a saturation magnetostriction λ s ≦|4| ppm, a round hysteresis loop with 0.50≦Br/Bs≦0.85 and an H cmax ≦20 Ma/cm, whereby the current transformer cores consist of a soft magnetic iron-based alloy in which at least 50% of the alloy structure consists of fine crystalline particles with an average particle size of 100 nm or less and the iron-based alloy has essentially the composition: (Fe x-a Co a Ni b ) x Cu y M z Si v B w where M denotes an element from the group V, Nb, W, Ta, Zr, Hf, Ti, Mo or a combination thereof and in addition: x+y+z+v+w=100%, where Fe+Co+Ni=x=100%−y−z−v−w Co a≦1.5 at % Ni b≦1.5 at % Cu 0.5≦y≦2 at % M z≦5 at % Si 6.5≦v≦18 at % B 5≦w≦14 at % wherein v+w>18 at%.