The total loss per cycle was previously formed as P/f congruent to k(0) + k(1) f + k(2) f(0.5) for 3% SiFe in the range of 0 less than or equal to f less than or equal to 100Hz. A mathematical model for core losses including the skin effect is improved using Matlab(TM) up to 1 kHz induction frequency. This model uses an approach similar to the above equation. However, it has some extra terms for high frequency and geometrical effects, it is in good agreement with experimental data measured previously on a range of toroids magnetized between 50 Hz and 1 kHz. (C) 2003 Elsevier B.V. All rights reserved.