Patent ID: 7473325

Claim:
A current transformer core made of an alloy having a composition represented by the general formula: Fe 100-x-a-y-c M x Cu a M′ y X′ c (by atomic %), wherein M is Co and/or Ni, M′ is at least one element selected from the group consisting of V, Ti, Zr, Nb, Mo, Hf, Ta and W, X′ is Si and/or B, and x, a, y and c are numbers satisfying 10≦x≦50, 0.1≦a≦3, 1≦y≦10, 2≦c≦30, and 7≦y+c≦31, respectively; at least part or all of the alloy structure being composed of crystal grains having an average particle size of 50 nm or less; and said alloy having a magnetic flux density B 8000 of 1.2 T or more at 8000 Am −1 , an anisotropic magnetic field H K of 150-1500 Am −1 , a squareness ratio B r /B 8000 of 5% or less, and an alternating-current specific initial permeability μ r of 800-7000 at 50 Hz and 0.05 Am −1 .