Accounting for resistivity and permittivity in high frequency permeability measurements: application to MnZn ferrites

Kéradec, Jean-Pierre; Fouassier, P.; Cogitore, B.; Blache, François

doi:10.1109/imtc.2003.1207952

Cited by 13 publications

(22 citation statements)

References 3 publications

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“…When the apparent complex permeability is measured using the ferrite core inductors, special attention should be paid to the turn numbers and the way of coil disposition [12]. The purpose is to minimize the influence of the stray capacitance between turns at high frequencies, while the impedance of the inductors should not be too weak to be measured.…”

Section: Resultsmentioning

confidence: 99%

“…In the following analysis, the imaginary part of the complex permittivity includes the electrical conductivity of the Mn-Zn ferrites. When the width of the core (R 2 − R 1 ) is smaller than its mean radius, the mathematical model for the toroidal core can be simplified to a 2-D one, and Cartesian coordinates can be adopted to solve the fields in the cross section [7], [8], [12]. For more accurate results, in the following analysis, cylindrical coordinates are adopted.…”

Section: Mathematical Model Of Toroidal Ferrite Core Inductors Wimentioning

confidence: 99%

“…Different from the methods of using one ferrite core inductor and one ferrite core capacitor [7]- [9], [12] to trace the intrinsic values, the method in this paper avoids the difficulty in making solid electrical contacts on the surfaces of the ferrite material, and thus, has the advantage of easier preparation of the samples needed.…”

Section: Introductionmentioning

confidence: 99%

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Determination of Dimension-Independent Magnetic and Dielectric Properties for Mn–Zn Ferrite Cores and Its EMI Applications

Huang

Zhang

Tseng

2008

IEEE Trans. Electromagn. Compat.

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Simultaneously high permeability and permittivity results in a pronounced dimensional effect in Mn-Zn ferrite cores, which makes the measured complex permeability differ for cores with different dimensions. This paper provides a succinct method to solve an inverse problem of tracing dimension-independent or intrinsic complex permeability and permittivity for Mn-Zn ferrites using two toroidal and rectangular-cross-sectioned cores with different dimensions. The apparent complex permeability of ferrite cores with other dimensions can then be predicted from the traced intrinsic values, so will the effective impedance of common-mode chokes made of such cores. The traced intrinsic permeability is in good agreement with the measured apparent complex permeability of a very small toroidal ferrite core, in which dimensional effect can be ignored. The apparent complex permeabilities of ferrite cores with other dimensions are measured experimentally, and are also calculated from the determined intrinsic values. A very good agreement between the measured and calculated values is found.Index Terms-Complex permeability, complex permittivity, dimensional effect, Mn-Zn ferrite, Newton-Raphson method.

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Section: Resultsmentioning

confidence: 99%

Section: Mathematical Model Of Toroidal Ferrite Core Inductors Wimentioning

confidence: 99%

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Determination of Dimension-Independent Magnetic and Dielectric Properties for Mn–Zn Ferrite Cores and Its EMI Applications

Huang

Zhang

Tseng

2008

IEEE Trans. Electromagn. Compat.

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“…For example, if the HP 16451B dielectric test fixture [17] is used to measure the impedance of the ferrite core capacitor, the bandwidth is limited to 15 MHz. If a wire wound ferrite core inductor is used in the measurement, the stray capacitance between the coils and the unsymmetrical disposition of the coils will definitely limit the bandwidth of measurement [11]. Solid electrical contacts on the ferrite core are required when the impedance of the ferrite core capacitor is measured.…”

Section: Introductionmentioning

confidence: 99%

“…Solid electrical contacts on the ferrite core are required when the impedance of the ferrite core capacitor is measured. But in practice, the electrical contacts made by using either silver conductive paint [13], [14] or aluminum deposition [11] are not perfect at high frequencies. Usually the upper frequency of the measurement results by using the field-circuit coupled methods is limited to 10 MHz.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Mn–Zn Ferrites Using the Coaxial Transmission Line Method

Huang

2008

IEEE Trans. Magn.

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In the coaxial transmission line method, a factor that greatly influences the accuracy of the results is the air gaps between the material under test and the coaxial transmission line test fixture. In this paper, we discuss the influence of the air gaps and the measures that can be taken to minimize that influence when Mn-Zn ferrites are measured. We propose an improved simulation model of the coaxial transmission line test fixture holding the material under test in which the air gaps are filled with conductive materials. By combining the improved simulation model, the mode-matching method, and the Newton-Raphson method, the Mn-Zn ferrites' intrinsic complex permeability and permittivity can be determined accurately, even if the conductor-filled gaps are quite wide. We also examine the influence of the finite conductivity of the coaxial transmission line test fixture. We manufactured a coaxial transmission line test fixture to measure the intrinsic complex permeability and permittivity of Mn-Zn ferrites in the frequency range from 10 to 200 MHz. The intrinsic values thus determined have been experimentally verified. We describe the structure of the test fixture, its calibration issues, and the experimental results.

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Current Sharing Between Parallel Turns of a Planar Transformer: Prediction and Improvement Using a Circuit Simulation Software

Margueron

Keradec

Besri

2007

2007 IEEE Industry Applications Annual Meeting

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Abstract-With the increase of power needs in low voltage applications, wiring several windings in parallel to sustain large currents becomes common. This operation often has a dangerous impact on transformer reliability because additional currents, we call "circulation currents", create extra losses, generally not taken into account by analytical approaches. Yet, hot points which result from these currents can destroy the component. In planar transformers, windings are made of PCB layers and circulation currents lead to severe unbalance of current sharing between parallel layers. This paper presents an analytical method which enables currents in all layers to be evaluated using only a circuit simulation software such as Pspice ® or PSIM ® . For a designer, this method is very intuitive and fast compared with the use of fem simulations.

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Accounting for resistivity and permittivity in high frequency permeability measurements: application to MnZn ferrites

Cited by 13 publications

References 3 publications

Determination of Dimension-Independent Magnetic and Dielectric Properties for Mn–Zn Ferrite Cores and Its EMI Applications

Determination of Dimension-Independent Magnetic and Dielectric Properties for Mn–Zn Ferrite Cores and Its EMI Applications

Characterization of Mn–Zn Ferrites Using the Coaxial Transmission Line Method

Current Sharing Between Parallel Turns of a Planar Transformer: Prediction and Improvement Using a Circuit Simulation Software

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