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.
Citations
More filters
••
17 Jun 2007TL;DR: In this paper, the ID propagation of a transverse electromagnetic (TEM) plane wave into conductive layers is modeled analytically and used to derive expressions for the field and current distributions in the metal.
Abstract: The attenuation of EMI transmission line filters can be improved at high frequencies by employing eddy current absorption. This is achieved by introducing a material having a low conductivity and/or high permeability in specific regions of the conduction paths. In this paper the ID propagation of a transverse electromagnetic (TEM) plane wave into conductive layers is modeled analytically and used to derive expressions for the field and current distributions in the metal. These results are the basis for computing the frequency dependent ohmic losses of the multi-layered conductive paths in the transmission line filter structures. They form part of a comprehensive analytical filter model, which is suitable for synthesis of integrated RF transmission line EMI filters.
7 citations
••
TL;DR: In this paper, a simple procedure to calculate the efficiency and power density of power conversion systems for offshore wind turbines is described, which can be used as a starting point into the linear design process to calculate losses in semiconductors and transformer as well as the volume of main elements.
7 citations
••
01 Dec 2018
TL;DR: This paper refines the existing analytical frequency-dependent method for accurately calculating leakage inductance in the medium frequency range based on the magnetic field intensity distribution and the stored magnetic energy method and employs mean turn length of individual layer which makes the calculation more precise.
Abstract: Nowadays, medium frequency transformers are widely employed with power electronic converters, offering obvious benefits for modern power system. Rising the switching frequency leads to the need for accurate estimation of the characteristics of a designed transformer. This paper refines the existing analytical frequency-dependent method for accurately calculating leakage inductance in the medium frequency range based on the magnetic field intensity distribution and the stored magnetic energy method. Unlike the previous expressions, the proposed method employs mean turn length of individual layer which makes the calculation more precise. The advantages and impacts of interleaved winding structure to minimize the leakage inductance are also shown by comparing different winding patterns. Transformer prototypes with specifications as 10kW, 500/5000V, 5kHz have been manufactured and tested. The presented equations for inductance calculation are benchmarked to the experimental results on the developed transformer prototypes as well as the finite element analysis (FEM) simulation results.
7 citations
•
20 Dec 2007
TL;DR: In this article, a nouvelle structure de convertisseur a transfert d'energie mixte (MET) adaptee au LCT pouvant offrir un interet industriel dans un futur proche compte tenu de sa similitude avec une alimentation a decoupage classique Forward.
Abstract: Dans le contexte de l'amelioration de la compacite des alimentations d'electronique de puissance, l'integration des composants passifs constitue l'un des principaux leviers pour atteindre des niveaux de miniaturisation consequents. Dans ce cadre, differents travaux ont deja ete engages de part le monde. Les travaux presentes dans ce memoire concernent la reduction des volumes des composants passifs, inductance - transformateur – condensateur, indispensables a toute structure d'electronique de puissance, en mariant ces trois elements en un seul et unique appele composant « LCT ». L'adaptabilite de cette association depend en grande partie des performances des dielectriques utilisables dans cette realisation permettant l'integration de capacites elevees pour ainsi inserer ce dispositif LCT dans tout type de structure. Actuellement, le developpement des materiaux ne permettant pas d'envisager toutes les applications classiquement rencontrees en electronique de puissance, nous avons etudie une nouvelle structure de convertisseur a transfert d'energie mixte (MET) adaptee au LCT pouvant offrir un interet industriel dans un futur proche compte tenu de sa similitude avec une alimentation a decoupage classique Forward. Outre les materiaux dielectriques en cours d'evolution, l'expansion de ce concept passe par un travail de modelisation consequent, ainsi que par des technologies de mise en œuvre performantes comme les circuits multicouches. A l'issu de ce travail, un prototype a ete realise dont les performances sont presentees, comprenant un composant LCT au sein de cette structure MET.
7 citations
••
01 Oct 2014
TL;DR: In this article, a modified transformer interleaving winding technique is implemented to reduce Skin, Proximity and leakage inductance which are associated with high voltage and high frequency, and the proposed techniques are implemented in a proto type of 220W dc-dc converter designed with RCD forward converter topology with current mode control.
Abstract: This paper addresses design issues involved in development of high voltage DC-DC converters such as optimizing isolation transformer parameters (leakage, proximity and Skin Effect), Power MOSFET losses and achieving tight voltage regulation (0.1%) used in Transmit Receive Multi Modules (TRMM). A modified transformer interleaving winding technique is implemented to reduce Skin, Proximity and leakage inductance which are associated with high voltage and high frequency. The proposed techniques are implemented in a proto type of 220W dc-dc converter designed with RCD forward converter topology with current mode control. Silicon Carbide (SiC) MOSFETS are used to improve efficiency of converter. 220W dc-dc converter is having the features of very good regulation ( 75%) in all operating conditions and meets MIL-STD-704E/F. The proto is developed in dimensions of 125mm×60mm.
7 citations
References
More filters
••
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
••
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