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Stadler A.,STS Spezial Transformatoren Stockach GmbH and Co. KG
Journal of Physics: Conference Series | Year: 2011

In this paper a new approach is presented, how to calculate the inductance and the core losses of chokes considering DC premagnetization. The formulation is based on the well known Hodgdon model. Generalized material functions are applied that can be easily adapted to measured data. To obtain these data, an experimental set-up was developed according to the standards. It is shown that the measurement of symmetrical B-H loops is sufficient to calibrate the model. By means of the adapted dynamical model also unsymmetrical hysteresis loops can be simulated with high accuracy in steady state. The influence of DC premagnetization on the inductance and the core losses is investigated under practical conditions using commercial ferrite ring core specimens. The results are verified by measurements and illustrated in various figures and tables. © Published under licence by IOP Publishing Ltd. Source

Stadler A.,STS Spezial Transformatoren Stockach GmbH and Co. KG | Albach M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Lindner A.,Friedrich - Alexander - University, Erlangen - Nuremberg
IEEE Transactions on Magnetics | Year: 2010

In this paper, a new method to construct ac electrical properties from impedance measurements using conventional ring core specimens is proposed. Different coaxial cartridges are developed allowing four-wire measurements with an automatic compensation of the test-leads. To achieve optimum results, the specific material parameters are reconstructed from the measured impedances by means of an analytical solution of Maxwell's equations for the toroidal sample geometry. Hence inhomogeneous electromagnetic fields due to occurring eddy currents and displacement currents are considered up to the megahertz range. To investigate the influence of the temperature on the electrical properties, the temperature-resistant cartridges can be transferred into a heating cabinet-specific results are finally exemplified for different MnZn ferrite materials. © 2010 IEEE. Source

Stadler A.,STS Spezial Transformatoren Stockach GmbH and Co. KG
IET Conference Publications | Year: 2014

In this paper, the AC resistance of transformer lead-outs is investigated. For this purpose, an equivalent complex permeability model is used. It is shown, that the copper losses can be split into DC (RMS), skin and proximity losses. Parallel bundles of insulated strands are assumed for the leadouts. Hence, the proximity losses are dominated by the inner proximity effect which can be easily calculated by a given approximate formula. Finally, the model is compared to measured data. Source

Stadler A.,STS Spezial Transformatoren Stockach GmbH and Co. KG
2011 7th International Conference-Workshop Compatibility and Power Electronics, CPE 2011 - Conference Proceedings | Year: 2011

The frequency range below 135kHz is preferred for inductively coupled radio frequency identification (RFID) systems. At low frequency, the magnetic field coupling between reader and transponder can be increased by using a ferrite core transponder antenna. In this paper, the magnetic field pattern of such a device is investigated. A semi-numerical procedure is presented, how to calculate the magnetic fields resulting from coil and core with avoidance of virtual boundaries. Consequently, calculations at short as well as at large distances can be conducted with high accuracy and minimum computational expense. The model is finally verified by measurements and further simulation based on finite element method (FEM). © 2011 IEEE. Source

Stadler A.,STS Spezial Transformatoren Stockach GmbH and Co. KG | Gulden C.,STS Spezial Transformatoren Stockach GmbH and Co. KG
2013 15th European Conference on Power Electronics and Applications, EPE 2013 | Year: 2013

In this paper, a systematic procedure is presented, how to predict the AC resistance of litz-wire windings considering air gap fringing fields. For this purpose, an equivalent complex permeability model is derived for hexagonally packed wires. It is shown, how finite element method (FEM) can be used to determine the real as well as the imaginary part of the complex permeability with the copper filling factor as a parameter. A further FEM-model is deduced to describe the air gap fringing fields of gapped inductors. Accordingly, the exact proximity losses of the litz-wire winding are determined correctly and the AC resistance of practical inductors can be predicted over a wide frequency range with high accuracy. This offers the opportunity to optimize such components. Finally, the influence of various parameters on the copper losses is investigated and verified by means of experimental data drawn from impedance measurements. © 2013 IEEE. Source

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