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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TL;DR: In this paper, a systematic review of bridgeless power factor correction (PFC) boost rectifiers, also called dual-boost PFC rectifiers is presented, where loss analysis and experimental efficiency evaluation for both CCM and DCM/CCM boundary operations are provided.
Abstract: In this paper, a systematic review of bridgeless power factor correction (PFC) boost rectifiers, also called dual boost PFC rectifiers, is presented. Performance comparison between the conventional PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier family is performed. Loss analysis and experimental efficiency evaluation for both CCM and DCM/CCM boundary operations are provided.
739 citations
22 Jun 1997
TL;DR: In this paper, the number and diameter of strands to minimize loss in a litz-wire transformer winding is determined, and a power law to model insulation thickness is combined with standard analysis of proximity effect losses to find the optimal stranding.
Abstract: 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 the optimal stranding. Suboptimal choices under other constraints are also determined.
683 citations
07 May 2007
TL;DR: In this article, a systematic review of bridgeless PFC boost rectifiers, also called dual boost PFC rectifiers is presented, where design considerations and experimental results in both CCM and DCM/CCM boundary operations are provided.
Abstract: In this paper, a systematic review of bridgeless PFC boost rectifiers, also called dual boost PFC rectifiers, is presented. Performance comparison between the conventional PFC boost rectifier and a representative member of the bridgeless PFC boost rectifier family is performed. Design considerations and experimental results in both CCM and DCM/CCM boundary operations are provided.
588 citations
TL;DR: In this paper, the authors propose an orthogonality between skin effect and proximity effect to calculate the AC resistance of round conductor windings, which gives more accurate answers than the basic one-dimensional method because the exact analytical equations for round conductors can be used.
Abstract: The one well-known one-dimensional method for calculating the AC resistance of multilayer transformer windings contains a built-in orthogonality which has not been reported previously. Orthogonality between skin effect and proximity effect makes a more generalized approach for the analytical solution of AC resistance in windings possible. This includes a method to calculate the AC resistance of round conductor windings which is not only convenient to use, but gives more accurate answers than the basic one-dimensional method because the exact analytical equations for round conductors can be used. >
546 citations
TL;DR: In this paper, a new method for predicting the stray capacitance of inductors is presented, which is based on an analytical approach and the physical structure of the inductors, where the inductor winding is partitioned into basic cells.
Abstract: A new method for predicting the stray capacitance of inductors is presented. The method is based on an analytical approach and the physical structure of inductors. The inductor winding is partitioned into basic cells-many of which are identical. An expression for the equivalent capacitance of the basic cell is derived. Using this expression, the stray capacitance is found for both single- and multiple-layer coils, including the presence of the core. The method was tested with experimental measurements. The accuracy of the results is good. The derived expressions are useful for designing inductors and can be used for simulation purposes.
393 citations
References
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TL;DR: In this article, a set of curves showing eddy-current resistance as a function of the number of layers and conductor thickness are presented, with more information on their limitations, and further formulas are derived for minimum losses for a number of different cases.
Abstract: Most of the earlier studies of eddy-current resistance have been made by those interested primarily in the effect of compromise transpositions on the losses of rotating equipment. Their results have included formulas for the eddy-current resistance for perfect transpositions, but these have gotten into handbooks in difficult form or have been ignored entirely. Such formulas are presented here in more usable form, with more information on their limitations, and further formulas are derived for minimum losses for a number of different cases. Included is a set of curves showing eddy-current resistance as a function of the number of layers and conductor thickness. Formulas also are included that take into account the differing lengths of conductor in successive layers and that approximate the end losses in a spiral coil on account of radial flux.
5 citations