Affiliations: Kungliga Tekniska Högskolan, Stockholm, Sweden
Correspondence:
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Corresponding author: Claes Carrander, Kungliga Tekniska Högskolan (KTH), Elektroteknisk Teori och Konstruktion, Teknikringen 33, 100 44 Stockholm, Sweden. Tel.: +86 46 72 720 50 40; E-mail:claesca@kth.se
Abstract: The magnetic properties of a power transformer core are generally held to be
quite similar to those of the core steel itself. Due mainly to it being rare
and practically difficult to acquire a transformer for testing and
verification, testing of large units is usually only performed concerning
no-load losses. However, other parts of the magnetic hysteresis loop are
more sensitive to variations in material and geometry and could be used for
more detailed diagnostics. This paper shows that measurements of magnetic
hysteresis can be performed with good results on large power transformers.
Methods to compensate for capacitive currents and to calculate the effective
magnetic length of the core are shown and the results are compared to
standard material measurements. The results show good agreement with Epstein
frame measurements on annealed samples.
Keywords: Power transformers, magnetic hysteresis, core steel, magnetic length, epstein, SST, magnetic properties
