Core Loss Calculation Method Considering Leakage Flux Induced Power Loss for Nanocrystalline Core High-Frequency Transformer Under Load Condition

Besides the main flux-induced core loss, high flux density, and normal leakage flux in surface ribbons of nanocrystalline core can produce excess leakage flux core loss (LFCL) and leakage flux eddy current loss (LFECL), which are usually overlooked in core loss calculation. In this paper, total core loss of nanocrystalline core HFT under load condition is proposed to be calculated by summation of main flux induced core loss, LFCL and LFECL. The LFCL is proposed to be calculated by improved generalized Steinmetz equation based on practical flux density distribution and the LFECL is proposed to be calculated by Fourier superposition method based on LFECL resistances. Further, the impacts of surface ribbons saturation on LFCL and LFECL are analyzed. A three-dimensional finite element simulation method is proposed to calculate flux density and eddy current density distributions. A LFCL attenuation factor and a LFECL multiplication factor are proposed to correct LFCL and LFECL considering saturation. A HFT prototype is made and calorimetric method is applied to measure core loss. Without considering LFCL and LFECL, core loss calculation errors can exceed 60%. With the proposed method, leakage flux power loss calculation errors are within 15% and total core loss calculation errors are within 10%. The LFCL and LFECL are negligible in nanocrystalline core loss. The proposed method can guide nanocrystalline core HFT design.