Magnetic Measurements on Electrical Steels using Epstein und SST Methods

Electrical steel sheet is an important material for which world market volume amounts to several billion Euros. Since the efficiency of all electrical and electromechanical energy transformation depends on the magnetic loss in the cores formed by this material its quality is also of eminent economic significance. The magnetic loss, which normative term is the specific total loss measured in Watt per kilogram, is the key quantity for the grading of this material. Its precise measurement requires well defined and controlled conditions, proper equipment and careful calibration of the setup. The existing two international standards specify methods for this purpose using different magnetic circuits having different systematic error characteristics. This situation is due to different preferences and demands of different user circles. In short, transformer designers, insisting in historical continuity, prefer the Epstein method whereas steel manufacturers are in favour of the Single Sheet Tester (SST) method for reasons of rational and economical quality control procedures. Standard institutes have thus to provide both, the Epstein method and the SST method in order to trace these measurements back to the SI units.