Charles R. Sullivan

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to reprint or republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Abstract— An improved calculation of ferrite core loss for nonsinu-soidal waveforms separates a(More)
— The two best-known methods for calculating high-frequency winding loss in round-wire windings—the Dowell method and the Ferreira method—give significantly different results at high frequency. We apply 2-D finite-element method (FEM) simulations to evaluate the accuracy of each method for predicting proximity-effect losses. We find that both methods can(More)
— An extension to the Steinmetz equation is proposed, to enable estimation of hysteresis losses in magnetic core materials with nonsi-nusoidal flux waveforms. The new formulation is shown to avoid anomalies present in previous modified-Steinmetz-equation calculations of loss with nonsinusoidal waveforms. Comparison with experimental measurements in MnZn(More)
— It has recently been shown that the most commonly used methods for calculating high-frequency eddy-current loss in round-wire windings can have substantial error, exceeding 60%. Previous work includes a formula based on a parametric set of finite-element analysis (FEA) simulations that gives proximity-effect loss for a large range of frequencies, using(More)
—The largest loss in an example litz-wire flyback transformer is found during current commutation between windings. In order to reduce this loss, a new optimization method is introduced. The new method optimizes strand size and number in litz wire considering cost and loss. Unlike previous methods, it is valid with two-or three-dimensional field geometry(More)
— The number and diameter of strands to minimize loss in a litz-wire transformer winding is determined. With fine stranding, the ac resistance factor can be decreased, but dc resistance increases as a result of the space occupied by insulation. A power law to model insulation thickness is combined with standard analysis of proximity-effect losses to find(More)
— T HIS paper explores opportunities and challenges in power conversion in the VHF frequency range of 30-300 MHz. The scaling of magnetic component size with frequency is investigated, and it is shown that substantial miniaturization is possible with increased frequencies even considering material and heat transfer limitations. Likewise, dramatic frequency(More)
A numerical method is used to determine the winding shape that minimizes total winding losses in a gapped inductor with round-wire windings. The algorithm accounts for proximity-effect loss that results from the two-dimensional field in the winding area, and for the effect of the winding on that field. Results are presented for an example geometry. The(More)
— Previous methods for calculating power loss in litz-wire windings usually assume very fine strands such that the diameter of strands is much smaller than skin depth. In this paper, we present a method for calculating proximity-effect loss in litz-wire windings. This method uses an equivalent complex permeability model of the winding to describe the(More)