EPE Association: EPE 2021

EPE 2021 - Passives
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2021 ECCE Europe - Conference > EPE 2021 - Topic 01: Devices, Packaging and System Integration > EPE 2021 - Passives

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   A Magnetic Design Method for Powder Core Inductor with Concentrated Airgap Considering DC Superposition Characteristic Used for High Current Application
By Jun IMAOKA [View]
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Abstract: Powder cores are attractive magnetic cores for high current applications such as bidirectional dc/dcconverters used in power trains of eco-friendly automotive because of their high saturation flux density, high Curie temperature, and soft saturation characteristics. However, powder cores have nonlinear relative permeability characteristics dependent on the magnetic field intensity which results in a drop in the inductance value at high current values. There are two key solutions to keep constant inductance value at maximum power rating of circuit specifications: (1) inserting a concentrated airgap (2) reducing the number of turns to tackle the drop of relative permeability due to dc-bias. Therefore, this paper proposes a novel magnetic design method for powder core inductors with concentrated airgap which to keep the desired inductance constant under dc-bias conditions. The feature of the proposed design methodology is based on considering non-linear relative permeability directly based on the magnetic characteristics modeling. The validity of the proposed method is confirmed by experimental tests using EE core.

   Analytical eddy current loss model for foil conductors in gapped cores
By Jürgen BIELA [View]
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Abstract: For modelling and optimizing gapped high-frequency inductors, the calculation of eddy current losses in foil windings due to the two-dimensional fringing field caused by air gaps in the core is important. The winding loss models must offer a high accuracy when calculating the 2D field distribution and must be computationally efficient in order to enable several thousand calculations required during the optimization. This article proposes an analytical model based on the magnetic vector potential formulation that can predict the eddy current losses in foil windings due to the fringing field of an arbitrary number of air gaps. The analytical model is combined into a closed-form loss formula and verified by FEA simulations.

   Foil-winding design for medium-frequency medium-voltage transformers
By Thomas GRADINGER [View]
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Abstract: In this paper, the challenges tied to the design of foil windings for medium-frequency medium-voltage transformers for solid-state transformer applications, are addressed. Besides the core losses, winding losses represent the most important design challenge of any transformer, limiting its efficiency and power-processing capability. This is especially true for transformers operating at medium frequency, where additional winding losses are unavoidable and cooling surfaces are decreased due to frequency scaling. While litz-wire windings can help to overcome this challenge to some extent, foil windings remain a technology of choice in many industrial applications due to their low cost, easy manufacturability, good fill factor and high temperature class. A detailed case study of optimally designed foil-winding medium-frequency transformers, for the relevant range of standardized medium voltage levels, and considering state-of-the-art materials and technologies, is presented in this paper. This is done using a custom developed design optimizer that employs 2D finite-element simulations for accurate modeling of AC effects within the foil windings. The analysis of the mentioned results provides valuable insights, highlighting the influence of the selected insulation technology and a strong correlation between the rated insulation voltage and the additional frequency-dependent foil-winding losses.

   Modelling and minimization of the parasitic capacitance of ring core inductors
By Florentin SALOMEZ [View]
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Abstract: High-frequency static converters requires inductors, common and differential mode chokes with a low equivalent parallel capacitance. To reduce it, this paper proposes first a semi-analytical model of this capacitance for inductors made with coated ring cores of nano-crystalline material. This model is based on 2D finite element method to compute the turn-turn and turn-core parasitic capacitances, taking into account loose windings. Then the total capacitance is computed thanks to an energetic approach. The model is validated against measurements performed on one core for several numbers of turns. Since the model shows that the capacitance is almost linear with the parasitic turn-core capacitance, specific devices are proposed to increase the distance between turns and core and thus decrease the capacitance. It is demonstrated that a small increase in overall volume allows to divide the equivalent parallel capacitance of a common mode choke by almost a factor of three while increasing its overall volume by only 37 percents.

EPE 2021 - Passives
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2021 ECCE Europe - Conference > EPE 2021 - Topic 01: Devices, Packaging and System Integration > EPE 2021 - Passives
	[return to parent folder]

	A Magnetic Design Method for Powder Core Inductor with Concentrated Airgap Considering DC Superposition Characteristic Used for High Current Application By Jun IMAOKA	[View] [Download]
Abstract: Powder cores are attractive magnetic cores for high current applications such as bidirectional dc/dcconverters used in power trains of eco-friendly automotive because of their high saturation flux density, high Curie temperature, and soft saturation characteristics. However, powder cores have nonlinear relative permeability characteristics dependent on the magnetic field intensity which results in a drop in the inductance value at high current values. There are two key solutions to keep constant inductance value at maximum power rating of circuit specifications: (1) inserting a concentrated airgap (2) reducing the number of turns to tackle the drop of relative permeability due to dc-bias. Therefore, this paper proposes a novel magnetic design method for powder core inductors with concentrated airgap which to keep the desired inductance constant under dc-bias conditions. The feature of the proposed design methodology is based on considering non-linear relative permeability directly based on the magnetic characteristics modeling. The validity of the proposed method is confirmed by experimental tests using EE core.

	Analytical eddy current loss model for foil conductors in gapped cores By Jürgen BIELA	[View] [Download]
Abstract: For modelling and optimizing gapped high-frequency inductors, the calculation of eddy current losses in foil windings due to the two-dimensional fringing field caused by air gaps in the core is important. The winding loss models must offer a high accuracy when calculating the 2D field distribution and must be computationally efficient in order to enable several thousand calculations required during the optimization. This article proposes an analytical model based on the magnetic vector potential formulation that can predict the eddy current losses in foil windings due to the fringing field of an arbitrary number of air gaps. The analytical model is combined into a closed-form loss formula and verified by FEA simulations.

	Foil-winding design for medium-frequency medium-voltage transformers By Thomas GRADINGER	[View] [Download]
Abstract: In this paper, the challenges tied to the design of foil windings for medium-frequency medium-voltage transformers for solid-state transformer applications, are addressed. Besides the core losses, winding losses represent the most important design challenge of any transformer, limiting its efficiency and power-processing capability. This is especially true for transformers operating at medium frequency, where additional winding losses are unavoidable and cooling surfaces are decreased due to frequency scaling. While litz-wire windings can help to overcome this challenge to some extent, foil windings remain a technology of choice in many industrial applications due to their low cost, easy manufacturability, good fill factor and high temperature class. A detailed case study of optimally designed foil-winding medium-frequency transformers, for the relevant range of standardized medium voltage levels, and considering state-of-the-art materials and technologies, is presented in this paper. This is done using a custom developed design optimizer that employs 2D finite-element simulations for accurate modeling of AC effects within the foil windings. The analysis of the mentioned results provides valuable insights, highlighting the influence of the selected insulation technology and a strong correlation between the rated insulation voltage and the additional frequency-dependent foil-winding losses.

	Modelling and minimization of the parasitic capacitance of ring core inductors By Florentin SALOMEZ	[View] [Download]
Abstract: High-frequency static converters requires inductors, common and differential mode chokes with a low equivalent parallel capacitance. To reduce it, this paper proposes first a semi-analytical model of this capacitance for inductors made with coated ring cores of nano-crystalline material. This model is based on 2D finite element method to compute the turn-turn and turn-core parasitic capacitances, taking into account loose windings. Then the total capacitance is computed thanks to an energetic approach. The model is validated against measurements performed on one core for several numbers of turns. Since the model shows that the capacitance is almost linear with the parasitic turn-core capacitance, specific devices are proposed to increase the distance between turns and core and thus decrease the capacitance. It is demonstrated that a small increase in overall volume allows to divide the equivalent parallel capacitance of a common mode choke by almost a factor of three while increasing its overall volume by only 37 percents.