Characterization of amorphous iron distribution transformer core for use in high-power medium-frequency applications

Large strip-wound amorphous iron cores for 60 Hz distribution transformers have been commercially manufactured for almost two decades. For megawatt-scale power electronics applications with transformer operating frequencies in the low kilohertz range, these cores offer interesting characteristics. This paper presents the results of a characterization of a distribution transformer core specimen at kilohertz frequencies under rectangular voltage excitation. Measurements are carried out at different temperatures and installation conditions. Coefficients for Steinmetz loss approximation equations are provided. It is investigated how measured losses at rectangular voltage excitation can be used to calculate power dissipation at duty-cycle modulated voltages by use of appropriate core loss functions. Furthermore, cooling constraints are discussed based on the surface power dissipation of the core.