The currently available core losses calculation formulae do not take the impacts of frequency and flux density on the loss coefficients into account at high frequency and high flux density. To solve this problem

we proposed an improved core losses calculation formula. On the basis of the original losses data of several typical laminated silicon steels

in combination with the experimental data of core losses over wide range of excitation frequency carried out by using a novel 3-D magnetic properties testing system

we investigated the influences of eddy current skin effect and the dynamic hysteresis loop on the loss coefficients by employing the improved calculation formula. Then we drew out new curves of core losses

and compared them with the measured data. The results show that the core losses calculated by the proposed formulae have a good consistency with the measured data. The proposed method can improve the computation accuracy obviously

and reduce the maximum error from 35% to 10%. Moreover

it is validated that the loss coefficients should change with frequency and flux density at high frequency and high flux density.