The paper intends to study the core losses of non-oriented electrical steel laminations under high frequency voltage excitations. The measurement of core losses of the electrical steel laminations in Epstein Frame is implemented step by step from 50 Hz to 5000Hz. The accuracy of results evaluated from Expanded GSE method is compared with those tested by Epstein Frame. The core loss database for three different kinds of medium, medium-high and high quality electrical steel laminations (50CS350, 50CS470, 50CS600) is completed in the paper. Also, 85 test points of core loss data are established in the flux density ranging from 0.3T to 1.8T and in the power supply frequency ranging from 50Hz to 5000Hz. Maximum core loss value is close to 443W/kg. The tested core loss data and the Expanded GSE models are useful and may cover for the applications of large-scale wind-driven generators and general motors. They also enough provide designers with the accurate information to minimize the core losses of wind turbine generators.