Magnetic behaviour of GOES wound cores of transformers fed by square or sine voltages
Résumé
For medium frequencies, transformers can be designed with wound magnetic cores made of grain oriented electrical steel (GOES) thin strips. The material high magnetic permeability makes it possible to design transformers with long average field lines offering large windows for coils. However, GOES strips have a non-zero thickness. Eddy currents form loops inside each strip that concentrate the filed under their surfaces (skin effect). This phenomena is well known for sine voltages. The paper proposes an extension to square voltages. It explains that,for identical frequencies and peak fluxes, eddy current losses are lower for rectangular voltages than for sine ones. Analytical results, obtained for linear conditions, are confirmed by finite element (FE) simulations and measurements.
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