The non-oriented silicon iron sheets are available in two categories as a result of the production process: fully-process and semi-process sheets. For the semi-process type the manufacturer has to apply a supplementary thermal treatment. There was studied the influence of three thermal treatments on Fe-Si non-oriented (NO) sheets: first treatment at 200 °C for 30 minutes in a vibrating oil bath, the second treatment was done at 550 °C for 15 minutes and the third treatment was done at 700 °C. The measurements were realized for every case on sheets cut in rolling direction and in transversal direction with a single strip tester for samples of 280 × 30 mm2. To analyze the results was made a separation of the total energy losses in three components: Wh – hysteresis losses, WF – Foucault losses and Wexc – excess losses.

Keywords: Non-oriented silicon iron sheets, Thermal treatments, Loss separation