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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Proceedings Article•
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TL;DR: In this article, a model of effective permeability of a multilayer magnetic substrate is proposed to analyze the behavior of magnetic multilayers. But the model is not suitable for the case of antenna devices.
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01 Nov 2020
TL;DR: In this paper, the authors derived the harmonic current of three-phase medium-frequency transformer (MFT) with different winding configurations by using fundamental wave analysis, and the calculation method of copper loss was proposed.
Abstract: In this study, based on the analysis of operation principle and approximate equivalent circuit of the three-phase DAB converter, the expressions of harmonic current of three- phase medium-frequency transformer (MFT) with different winding configurations, including wye-wye, wye-delta, delta- delta, are derived by using fundamental wave analysis, and the calculation method of copper loss is proposed. Considering the voltage waveforms and phase shift strategy under different winding configurations, the expressions of magnetic flux density under six-step and three-step voltage waveform excitations are deduced, the extended expressions of various modification expressions of Steinmetz equation are presented to determinate the magnetic core losses of three-phase MFT under no-load and load condition. On this basis, the equivalent thermal network of three-phase MFT with five-legged core topology is built to calculate the temperature rise. Simulation and experimental results on three 5 kHz/15 kW three-phase MFT models with nanocrystalline alloy core verify the effectiveness of the above methods.
2 citations
20 Jul 2011
TL;DR: In this article, a low voltage DC-DC converter with a flyback transformer was designed and simulated using ANSYS PExprt software and an LT3574 IC chip from Linear Technology has been chosen for converter control.
Abstract: In this paper, we design a low voltage DC-DC converter with a flyback transformer. The converter will be used as a biased power supply to drive IGBTs. The flyback transformer using planar EI-core is designed and simulated using ANSYS PExprt software. Besides, anLT3574 IC chip from Linear Technology has been chosen for converter control. Finally, the converter modeling and simulation are presented and PCB layout is designed.
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27 Jun 2016
TL;DR: In this article, an improved methodology for selecting a core for higher power inductors, by using a more advanced approach to select initial values for the Window Utilization Factor (WUF) and the Core to DC Copper Loss Ratio (CCLR) as the two key starting parameters for the inductor design process.
Abstract: This paper presents an improved methodology for selecting a core for higher power inductors, by using a more advanced approach to select initial values for the Window Utilization Factor (WUF) and the Core to DC Copper Loss Ratio (CCLR) as the two key starting parameters for the inductor design process. The paper identifies the reasons why the conventional starting point assumptions for the WUF and CCLR based on higher frequency lower power inductor design principles are not appropriate for higher power inductors, and then presents a basis for identifying improved design starting points for these parameters that better suit inductors operating in the intermediate frequency range. Consequently the number of iterations required to achieve a final inductor design can be substantially reduced.
2 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