Effects of eddy currents in transformer windings
01 Aug 1966-Vol. 113, Iss: 8, pp 1387-1394
TL;DR: In this article, the effect of eddy currents on transformer windings is considered and a method is derived for calculating the variation of winding resistance and leakage inductance with frequency for transformers with single-layer, multilayer and sectionalised windings.
Abstract: The effects of eddy currents in transformer windings are considered, and a method is derived for calculating the variation of winding resistance and leakage inductance with frequency for transformers with single-layer, multilayer and sectionalised windings. The method consists in dividing the winding into portions, calculating the d.c. resistances and d.c. leakage inductances of each of these portions, and then multiplying the d.c. values by appropriate factors to obtain the corresponding a.c. values. These a.c. values are then referred to, say, the primary winding and summed to give the total winding resistance and leakage inductance of the transformer. Formulas are derived and quoted for calculating the d.c. resistances and leakage inductances of the winding portions. Theoretical expressions are derived for the variation with frequency etc. of the factors by which the d.c. values must be multiplied to obtain the corresponding a.c. values. These expressions are presented in the form of graphs, permitting the factors to be read as required.
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Dissertation•
30 Jun 2017
1 citations
21 Jun 2010
TL;DR: A novel ac winding resistance model of integrated magnetics in switched-mode power supply is presented and it will be more intuitive and suitable to reveal the winding loss mechanism of theIntegrated magnetics which have both transformer and inductor functions.
Abstract: Integrated magnetics has been popularly used to improve the power density, but the winding loss mechanism becomes more complex and hard to understand for its versatile magnetic functions. Therefore, a novel ac winding resistance model of integrated magnetics in switched-mode power supply is presented in this paper. It will be more intuitive and suitable to reveal the winding loss mechanism of the integrated magnetics which have both transformer and inductor functions. The model is illustrated with the integrated magnetics in forward-type converter and the coupled inductor in voltage regulator. With the understanding of the proposed resistance model, the measures to reduce the ac winding loss of integrated transformer can be taken by balancing the transformer component winding loss and the inductor component winding loss.
1 citations
16 Dec 2008
TL;DR: In this paper, a composant mixe integre de type planar appele inductance-condensateur-transformateur, connu sous le nom de LCT, permet d'atteindre cet objectif.
Abstract: Il est bien connu que dans les convertisseurs de puissance, la majorite du volume est occupee par les composants passifs. Afin de limiter cet impact, les concepteurs ont de plus en plus recours a l'integration. Dans ce cadre, un composant mixe integre de type planar appele inductance-condensateur-transformateur, connu sous le nom de LCT [2][3][5]-[7] permet d'atteindre cet objectif. Malgre tout, afin d'optimiser le volume de ce composant, un travail important concernant l'optimisation du dimensionnement de ces composants est d'estimer les pertes (cuivre, fer et dielectrique) dissipees au cours de son fonctionnement doit etre conduit. Cet article presente, dans un premier temps, le principe d'un LCT puis, dans un second temps, les differentes methodes de modelisation des pertes cuivre dans les composants planar applique a un LCT. Les limitations et perspectives de chaque methode seront aussi decrites.
1 citations
TL;DR: In this article, a low-winding loss design methodology was proposed to develop a real-scaled medium frequency transformer (MFT) for an isolated DC-DC converter to be used in a DC-interconnected offshore wind farm system.
Abstract: This paper describes a low winding loss design methodology to develop a real-scaled medium frequency transformer (MFT) for an isolated DC-DC converter to be used in a DC-interconnected offshore wind farm system. We assembled a core-type 500 kVA MFT consisting of a lap-joint amorphous wound core and windings with a primary Cu sheet and divided secondary Cu sheets, wound alternately in turns. Then, we compared its loss performance with that of a conventionally designed MFT. The alternately wound winding structure suppressed the medium-frequency proximity effect between the Cu sheets and the in-plane eddy current due to the fringing flux crossing the edges of the sheets and fixtures, and the winding loss at 3 kHz was 61% lower than that of the conventional MFT. In addition, we propose and discuss an accurate estimation method for the winding loss of core-type MFTs, considering the in-plane eddy current loss at the edge of the Cu sheets based on the finite element method.
1 citations
References
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TL;DR: In this article, a multilayer winding carrying an alternating current, such as the windings illustrated in figures 1, 2, and 3, each layer of copper lies in the alternating magnetic field set up by the current in all the other layers.
Abstract: IN any multilayer winding carrying an alternating current, such as the windings illustrated in figures 1, 2, and 3, each layer of copper lies in the alternating magnetic field set up by the current in all the other layers. Eddy currents are set up in each layer in a direction to partly neutralize the magnetic intensities in the interior of the copper wire in each layer. As a result of the eddy-current losses in the copper, the effective resistance of the winding to the alternating current it carries may be many times its resistance to continuous currents.
103 citations
TL;DR: In this article, the authors discuss the more important causes of eddy currents in heavy conductors carrying alternating currents and surrounded on three sides by iron, and propose a method to identify the most important causes.
Abstract: The object of the present paper is the discussion of the more important causes of eddy currents in heavy conductors carrying alternating currents and surrounded on three sides by iron.
93 citations
64 citations
TL;DR: In this article, it is shown that a considerable proportion of the effective resistance of inductive coils when used at radio frequencies is caused by the eddy-currents set up in the wires of the coils by the alternating magnetic field in which they are situated, and that in extreme cases the alternating current resistance may amount to more than one hundred times the direct current resistance.
Abstract: It is well-known that a considerable proportion of the effective resistance of inductive coils when used at radio frequencies is caused by the eddy-currents set up in the wires of the coils by the alternating magnetic field in which they are situated, and that in extreme cases the alternating current resistance may amount to more than one hundred times the direct current resistance. It is therefore important to have reliable formulae for the eddy-current resistance of such coils in order to determine the conditions which will reduce the eddy-current losses to a minimum. The simplest case, that of a long straight cylindrical wire under the action of its own current, has been treated by Kelvin, Rayleigh, Heaviside, and others. The general effect is known as the “skin effect,” because the current tends to concentrate more and more upon the skin of the conductor as the frequency increases.
49 citations
TL;DR: In this article, the authors show how hyperbolic functions of complex angles may be applied to the solution of the problem of heat losses in rectangular conductors that are embedded in open slots.
Abstract: The principal object of this paper is to show how hyperbolic functions of complex angles may be applied to the solution of the problem of heat losses in rectangular conductors that are embedded in open slots. A certain knowledge of the functions themselves is presupposed. Inasmuch, however, as they are handled like trigometric functions of real angles?except in regard to the plus and minus signs?it is a simple matter to acquire the requisite technical skill to use them. The hyperbolic function of a complex angle, consisting as it does of a real and an imaginary part, may represent a vector?the real part being the component of the vector along the horizontal, and the imaginary part, component along the vertical. Thus, for example, A sinh (x + j x) represents a vector just as A e j ? A/?, A (cos ? + j sin ?) represent vectors. Considerable experience has shown that the vector method for handling a-c. problems is much superior to the original method in which simple trigonometric functions were used. With this lesson before us, it should require but little contact with the problem at hand to demonstrate the superiority of the vector method, even though it employs the possibly unfamiliar hyperbolic quantities. These hyperbolic vectors have been used for a number of years in the analysis of problems involving a-c. circuits, which have distributed inductance and capacitance, and have proved their usefulness.
27 citations