Giant Epstein Tester for Magnetic Energy Loss Measurements of Non-Annealed Domain-Refined Fe–Si

Since 100 years, the Epstein tester serves as a compact and simple apparatus for the measurement of magnetic energy losses, in particular for Fe–Si steel. However, drawbacks result from time-consuming cutting and stacking of the high number of just $W =3$ cm wide sample strips of the standard Epstein tester (SET). Furthermore, the effects of cutting result in increased losses. Needs of annealing impede tests of modern materials with domain refinement that may lose its effectiveness. Results of numerical modeling indicated that both problems can be reduced by a strong enlargement of the strip width. Here, we report a novel giant Epstein tester (GET) with $W =10$ cm, in combination with increased strip length $L = 65$ cm. Sufficient averaging over test material is attained with two layers, i.e., from just eight strips. The magnetic field strength is determined by four large 3-D-printed tangential field coils, excluding impact from the four corners of frame. Time-averaged loss $P$ is computed from instantaneous magnetization power values $p$ , offering also maximum loss and orientation power. Results of GET were compared to data from single-sheet tester (SST) data, proving close similarities, without needs of annealing which is significant for laser scribed steel, as tested here. Results from SET prove to be higher. Analysis of power $p$ indicates the impact of supplementary domains in the magnetization process of the scribed material. Compared to SST, the drawbacks of the GET are the need of eight sample strips, as well as lower absolute accuracy, due to higher inhomogeneity. On the other hand, advantages are the absence of a yoke system and simplicity of test apparatus.