Calculation of core loss and copper loss in amorphous/nanocrystalline core-based high-frequency transformer

Xiaojing Liu,Gang Lei,Jianguo Zhu,Youhua Wang,Chengcheng Liu,Youguang Guo

doi:10.1063/1.4944398

Abstract

Amorphous and nanocrystalline alloys are now widely used for the cores of high-frequency transformers, and Litz-wire is commonly used as the windings, while it is difficult to calculate the resistance accurately. In order to design a high-frequency transformer, it is important to accurately calculate the core loss and copper loss. To calculate the core loss accurately, the additional core loss by the effect of end stripe should be considered. It is difficult to simulate the whole stripes in the core due to the limit of computation, so a scale down model with 5 stripes of amorphous alloy is simulated by the 2D finite element method (FEM). An analytical model is presented to calculate the copper loss in the Litz-wire, and the results are compared with the calculations by FEM.

Highlights

With the demand of high power electrical power conversion, the high-frequency transformers coupled with switching power converters have attracted significant attention in the recent years.[1,2] Thanks to the low loss property, amorphous and nanocrystalline alloys have been widely used for the core of high-frequency transformers
It is difficult to simulate the whole stripes in the core due to the limit of computation, so a scale down model with 5 stripes of amorphous alloy is simulated by the 2D finite element method (FEM)
The additional eddy current loss caused by the effect of end stripe is insignificant, and can be ignored

Summary

INTRODUCTION

With the demand of high power electrical power conversion, the high-frequency transformers coupled with switching power converters have attracted significant attention in the recent years.[1,2] Thanks to the low loss property, amorphous and nanocrystalline alloys have been widely used for the core of high-frequency transformers. Paper[7] presented an approximate model for resistance calculation of multi-strand wire winding, including Litz-wire winding by taking into account the proximity effect and skin effect according to the Dowell’s equation. Paper[8] presented a computational procedure to calculate the losses of Litz-wire according to the skin and proximity effect losses, based on a fast numerical simulation tool. Finite element method (FEM) is widely used in simulation and calculation of core and wire windings It usually simulates the core as a whole, while the core is wounded layer by layer and there are gaps between any two layers.2D FEM can be used in resistance calculation of un-twisted parallel solid wires (Litz-wire without twisting) and 3D FEM can be accurately, while it is still difficult to use FEM to simulate the Litz-wire due to the long computation time. In order to calculate the core loss accurately, the additional core loss by the effect of end stripe is considered

CORE LOSS CALCULATION

COPPER LOSS CALCULATION

Findings

CONCLUSION