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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)
— 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)
—This paper investigates the loss characteristics of several commercial rf magnetic materials for power conversion applications in the 10 MHz to 100 MHz range. A measurement method is proposed that provides a direct measurement of inductor quality factor Q L as a function of inductor current at rf frequencies, and enables indirect calculation of core loss(More)
— Multiphase voltage regulator modules (VRMs) for microprocessor power delivery with coupled output inductors are discussed. Strong coupling is shown to be feasible and effective at reducing ripple if the correct magnetic topology is used. For more than two phases, this can be a " ladder " core with windings around each rung. Typical ripple reduction is(More)
—The squared-field-derivative method for calculating eddy-current (proximity-effect) losses in round-wire or litz-wire transformer and inductor windings is derived. The method is capable of analyzing losses due to two-dimensional and three-dimensional field effects in multiple windings with arbitrary waveforms in each winding. It uses a simple set of(More)