8. Characterization of the main properties of electrical laminations

8.1 Epstein frame

The magnetic circuit consists of the sheet metal to be tested (figure 14 ). The sheet is cut into rectangular strips 30 mm wide and at least 280 mm long. For standardized qualification of grain-oriented sheets, the longest side is parallel to the rolling direction. The strips are fed into four square-shaped sheaths, around which a voltage winding (secondary) and a current winding (primary) are wound. Each of the primary and secondary windings has 700 turns. The number of strips used is always a multiple of four. It must be sufficient to ensure that the section of the magnetic circuit provides a secondary voltage whose measurement will be compatible with the lowest level of error...