The increasing of the a.c. motors efficiency is a stringent necessity in Europe, having important effects on the final users’ expenditures and on the decreasing of the emissions associated by the burning of the primary fuel to produce electrical energy. The increasing of the a.c. motors efficiency may be obtained especially by decreasing the energy losses in magnetic cores. Non-oriented silicon iron (NO Fe-Si) alloys are soft magnetic materials used in the construction of medium and high power rotating machines. To obtain an efficiency higher than 95%, it is necessary to promote a new design of their magnetic circuits and/or alternative cutting technologies. There was tested an industrial type of NO Fe-Si alloys M400-65A. The magnetic properties of the samples were measured using an uniaxial single sheet tester (SST) at different magnetic polarizations in a range of frequencies from 3 Hz to 200 Hz. The sheet cutting technologies, involved in this study, are mechanical, laser, waterjetting and electro-erosion cutting

Keywords: Electrical machines, Non-oriented silicon iron sheets, Energy losses