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Journal ArticleDOI

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
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Proceedings ArticleDOI
Felix Jauch1, Jurgen Biela1
17 Oct 2013
TL;DR: An isolated three-phase bidirectional AC-DC converter with a novel modulation strategy that enables Zero-Voltage-Switching (ZVS) for all switches over the whole AC line period is presented.
Abstract: This paper presents an isolated three-phase bidirectional AC-DC converter with a novel modulation strategy that enables Zero-Voltage-Switching (ZVS) for all switches over the whole AC line period. The AC-DC converter allows the direct coupling of a three-phase AC system with a DC port applying a single high-frequency transformer. A novel modelling approach for the power flows and the derivation of the control variables under ZVS conditions are provided. The design of components including loss models and simulation results of a 11kW electric vehicle battery charger to connect to the 230Vrms, 50Hz mains considering a battery voltage range of 380V to 540V validate the theoretical analysis.

18 citations

Journal ArticleDOI
TL;DR: To quantify the influence of the magnetic tank, its impedance model is thoroughly modeled by considering all the parasitic components and it is found that the parasitic capacitors of the magnetics do not equally affect the current ringing, and thereby the critical one is addressed.
Abstract: In dual active bridge (DAB) converters, there can be transformer current ringing, especially when the transformer turns ratio is high. It is induced by high dv / dt generated by fast switching as well as the low impedance of the magnetic tank at the high-frequency range. To quantify the influence of the magnetic tank, its impedance model is thoroughly modeled by considering all the parasitic components. It is found that the parasitic capacitors of the magnetics do not equally affect the current ringing, and thereby the critical one is addressed. On top of that, the design guide of the inductor is provided for the mitigation of the current ringing. Additionally, the impact of dv / dt is also studied. The models and analyses are verified on a 2.5-kW DAB prototype.

18 citations

Proceedings ArticleDOI
16 Jul 2000
TL;DR: In this paper, a set of IPEM models has been developed, including a 3D solid model by I-DEAS, parasitic model by Maxwell, thermal model by FLOTHERM and electrical model by Saber.
Abstract: The need for integrated analysis and design tools is becoming more evident, especially when integrated power electronics module (IPEM) is concerned. The whole procedure of developing IPEM needs the support from integrated tools. In this paper, a set of IPEM models has been developed. This includes a 3D solid model by I-DEAS, parasitic model by Maxwell, thermal model by FLOTHERM and electrical model by Saber. The exchange of geometry information among these models has been achieved. Furthermore, based on these models, this paper explores the tradeoff between minimizing parasitics and improving thermal performance.

18 citations

Proceedings ArticleDOI
09 Jul 2006
TL;DR: In this paper, eddy current losses in round conductors are discussed and a graphical approximation of kc as a function of wire diameter, frequency, layer number, copper packing factors in the direction parallel and perpendicular to the layer is provided.
Abstract: A practical method for calculating eddy current losses in transformer windings is reported. The method improves the classical loss presentation by introducing a loss coefficient, called eddy current factor kc. In this paper, eddy current losses in round conductors are discussed. A graphical approximation of kc as a function of wire diameter, frequency, layer number, copper packing factors in the direction parallel and perpendicular to the layer is provided. The graphs are obtained by analytical expressions compared with FEM simulations. To unify the approach for different cases, a reference diameter, apparent and equivalent frequency are defined. A few short examples for applying the method in transformer design are given. The method is applicable for a variety of transformers with different frequencies, wire diameters and conductor fittings. The proposed method is verified by designing several transformers. As an example, a 2.5 kW transformer is fully described. The experiments show good matching with the calculations.

18 citations

Journal ArticleDOI
Fu Wong1, Junwei Lu1
09 Apr 2000
TL;DR: In this paper, a high frequency planar transformer with helical windings is proposed, which combines the advantages of the planar magnetic core transformer and air core transformer, and the experimental results show that the input impedance and the voltage ratio of this new transformer are much higher than its air core counterpart.
Abstract: A high frequency planar transformer with helical windings is proposed. This transformer combines the advantages of the planar magnetic core transformer and air core transformer. The experimental results show that the input impedance and the voltage ratio of this new transformer are much higher than its air core counterpart. The numerical result shows that the flux is evenly distributed and totally enclosed inside the planar ferrite. The electromagnetic interference (EMI), generated from the windings of transformer, is significantly reduced by using magnetic ferrite cores.

18 citations

References
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Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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