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E Mulasalihovic, H. Pfützner, P. Zanolin, G. Shilyashki, V. Galabov:
"Effects of Moderate DC-magnetization on 3-D Loss Distributions of a 3-phase Model Transformer Core";
Poster: International Workshop on 1&2 Dimensional Magnetic Measurement and Testing, Wien, Österreich; 09-03-2012 - 09-06-2012; in: "Short Paper Proceedings", (2012), ISBN: 3-902-105-03-8; 59 - 60.

Unbalanced DC bias of 3-phase transformers may cause very strong increases of excitation currents and thus of stray fields. We investigated whether influx of the latter into the core yields planar eddy currents (PECs) as a source of planar eddy current losses. By use of the rise-of-temperature method, local distributions of total losses P were determined at 128 regions of the surface of a 3-phase/3-limb model core. Moderate bias in the middle limb yielded increases of P up to 100%, especially in limbs, while T-joint regions of rotational magnetization prove to be less affected. Local determinations of planar, classical eddy current losses P_{PEC} by means of a field vector sensor revealed local increases up to a factor of 10. Finally, interior PECs were analyzed by means of thin silver layer sensors. As a result, the intensity of P_{PEC} decreases exponentially towards the centre of the core.