Two-Step Method for the Calculation of Eddy Current Losses in an Open-Core Transformer

In order to minimize eddy current losses in an open-core type of transformer, a lower width-to-thickness ratio of lamination sheets and even varying lamination stacking direction than in the case of standard transformers are used. Consequently, narrow eddy current loops must be considered as a 2-D phenomenon, i.e., edge effects and irregular current density distributions cannot be neglected. A two-step method for the calculation of eddy currents and eddy current losses in an open-core transformer is presented. In the first step, using the anisotropic surrogate material, the magnetic flux density distribution within the bulk core model is calculated. In the second step, the magnetic flux density obtained in the first step is used as input to calculate eddy currents in a sufficient number of densely meshed 2-D slices of the laminated core. Numerical simulation of the method is carried out, and the results are compared with those obtained using a homogenization method and the brute force approach. The results show good agreement and indicate the importance of taking edge effects into account.