Jean-Pierre Schauwers

Ohmic losses calculation in SMPS transformers: numerical study of Dowell's approach accuracy

The paper compares two methods for ohmic losses calculation in switch-mode power supply transformers: Dowells 1D approach and 2D finite element method simulations (validated by measurements). Dowells method underestimates losses at the fundamental frequency for foil windings, whereas harmonic losses are generally overestimated (depending on conductor type). More significant differences are found with high leakage inductance transformers.

A closed-form formula for 2D ohmic losses calculation in SMPS transformer foils

A new closed-form formula aimed at calculating ohmic losses in switch-mode power supply transformers is presented. It is based on intensive 2D finite element method simulation. Only valid for one-layer-foil windings at the moment, it accurately covers cases where the classical Dowells formula significantly underestimated the losses.

Two-dimensional analysis of the edge effect field and losses in high-frequency transformer foils

In design of high-frequency magnetic devices, various approaches have been used to provide calculation tools that are able to predict winding losses, including skin effect and proximity effect, in their two-dimensional (2-D) aspects. Up to now, these approaches have been mainly focused on giving quantitative results for specific cases. Because the final purpose of designers is not to perform single calculations, but to obtain optimal designs, we have looked for a complementary approach providing more general 2-D guidelines and understanding of the phenomena. In this paper, we examine the case of a foil winding undergoing edge effect, a typical situation where classical one-dimensional theories underestimate the real losses. Using a 2-D closed-form formula we developed in a previous work and the associated database of 400 2-D numerical models, we systematically analyze the dependence of the 2-D field and the corresponding extra losses with the geometrical design variables describing the dimension and position of the winding.

Eddy current losses in SMPS transformers round wire windings: a semi-analytical closed-form formula

We provide a new closed-form formula that instantly calculates the 2D high-frequency ohmic losses (skin and proximity effects) in round wire windings. It has been obtained by overwriting the classical definition (shown to be erroneous) of the layer copper factor introduced in 1D analytical theories. Compared to similar previous formulas, the average error is divided by a factor of thousand. Experimental validation is provided

Planar transformer technology applied to AC/DC conversion

Magnetic components play an important role in the technological evolution towards increased power density of AC/DC power converters. Planar transformers provide several advantages that have to be balanced with the latest evolution of more classical transformer technology. This paper analyses the interest of using planar transformer for AC/DC power conversion. Results of the implementation of a planar transformer in a 600 W AC/DC converter illustrate the analysis.

Simultaneous analysis of harmonics and 2D effects on the optimal thickness of transformer windings

Summary form only given. Optimum transformer design needs accurate windings losses calculation. The current harmonic spectrum and 2D field effects have both been reported to significantly influence the winding losses. Up to now, these two topics have always been treated separately. Thanks to a new analytical form which permits one to to include 2D effects in the closed-form formula, this paper answers for the first time the designer question: what is the final impact of harmonics and 2D effects, considered simultaneously, on the losses and on the optimum thickness of the windings?.