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G. Shilyashki, H. Pfützner, Y. Kanto, U. Meisl, A. Windischhofer, M. Giefing:
"Thin band detector for analyses of rotational magnetization in laminated machine cores";
Journal of Magnetism and Magnetic Materials, Vol. 503 (2020), 1 - 5.

Soft magnetic SiFe cores of rotating machines or 3-phase transformers tend to exhibit rotational magnetization (RM). RM is of high industrial importance, sincecausing significant increases of both losses and magnetostriction. However, so far, for the direct detection of RM, not any sensor type was available that could beintroduced to the inner of a core in non-destructive ways. This paper describes a promising novel principle that takes advantage from so-called tangential inductionsensors, as developed recently. The sensor consists of a nano-crystalline ribbon of e.g. 30 mm × 10 mm × 20 µm size. It is placed on the to-be-inspected region ofSiFe lamination, with its long axis in transverse direction. With the up-come of significant RM, the ribbon tends to be strongly magnetized, up to saturation. Thesensor principle is based on the finding that the slope of upcoming saturation induction increases with increasing so-called axis ratio a of RM. Aiming for a sensor thatcan be inserted in a machine core without creating a disturbing inter-laminar air gap, a less than 300 µm thick sensor prototype was manufactured by means of a so-called 2D/3D assembler. On a kapton foil as a substrate, the latter produces a winding of eight silver ink turns round the ribbon that acts as a nucleus of a coil. Ininstants of upcoming saturation, the spike-like coil signal exhibits an amplitude that is proportional to the axis ratio a of RM, in approximation.

http://dx.doi.org/10.1016/j.jmmm.2020.166575