Abstract
Laminated soft magnetic cores of transformers, rotating machines etc. may exhibit complex 3D flux distributions with pronounced normal fluxes (off-plane fluxes), perpendicular to the plane of magnetization. As recent research activities have shown, detections of off-plane fluxes tend to be essential for the optimization of core performances aiming at a reduction of core losses and of audible noise. Conventional sensors for off-plane flux measurements tend to be either of high thickness, influencing the measured fluxes significantly, or require laborious preparations. In the current work, thin novel detector bands for effective and simple off-plane flux detections in laminated machine cores were manufactured. They are printed in an automatic way by an in-house developed 3D/2D assembler. The latter enables a unique combination of conductive and non-conductive materials. The detector bands were effectively tested in the interior of a two-package, three-phase model transformer core. They proved to be mechanically resilient, even for strong clamping of the core.
Highlights
In the past, it was well accepted that flux distribution in cores of transformers or rotating machines can be considered as a two-dimensional magnetization problem
Recent studies have shown that laminated soft magnetic cores may exhibit complex 3D flux distributions with pronounced normal fluxes perpendicular to the magnetization plane
The results indicate the important role of the overlaps for the entire flux distribution of multi-package transformer cores
Summary
It was well accepted that flux distribution in cores of transformers or rotating machines can be considered as a two-dimensional magnetization problem. Sensors 2017, 17, 2953 a significant drawback of all numerical methods is the lack of accurate material data, e.g., non-linear permeability functions in the transverse and in the normal direction The latter may be a source of significant deviations of calculated local induction values from real ones. Even the thinnest sensors are about 1 mm thick and appropriate for measurements only on the surface, not in the core interior Another possibility would be the usage of single turn normal search coils of thin wire stuck directly onto laminations, as often used for transformer cores [14,15]. These measurements are linked with high expenditure of manual work, requiring the opening of the core, preparation of laminations and re-stacking. While the previous work [16] described applications in the corner regions of a transformer core, the current paper presents an example of results for T-joint regions
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