EPE Association: EPE 2023 - DS2a: Passive Components

EPE 2023 - DS2a: Passive Components
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2023 ECCE Europe - Conference > EPE 2023 - Topic 01: Devices, Packaging and System Integration > EPE 2023 - DS2a: Passive Components

   [return to parent folder]

   A Half-turn Winding Layout in Planar Transformers
By Chao LIU, Pinhe WANG, Zhe ZHANG, Jiasheng HUANG, Michael ANDERSEN, Gabriel ZSURZSAN, Ziwei OUYANG [View]
[Download]

Abstract: This paper presents an analysis of the current distribution on the parallel conductors of typical interleaved planar transformers. Through the investigation, it is discovered that the S-P-S-P-S winding layout with 'n+1' parallel layers exhibits a half-turn winding current distribution, resulting in lower AC resistance. Simulation and experiment results are used to validate the current distribution in the proposed half-turn transformer, demonstrating a nearly 20\% reduction in winding loss and leakage inductance compared to conventional layouts.

   A High Frequency Magnetic Test Bench with Fast Isothermal Measurements for Large Cores
By Anartz AGOTE, Asier ARRUTI, Iosu AIZPURU [View]
[Download]

Abstract: This paper presents a magnetic core test-bench that has been developed for high-frequency measurements. The bench is able to perform tests at 1 MHz, 300 V and in a range of 20 ºC to 150 ºC. It exhibits precise temperature control and possesses a high-power capacity, making it suitable for testing large scale magnetic cores. Comprehensive tests were conducted to validate the capabilities and performance of the test bench, and the obtained results are presented and discussed

   An improved approach for litz wire loss calculation based on segmented equivalent circuit
By Yueyin WANG, Wu CHEN, Zhan SHEN, Jianxi LAN [View]
[Download]

Abstract: Litz wires are often used to reduce AC losses in high frequency transformers. However, modeling the AC resistance is still chal-lenging. In this paper, a new analytical calculation method is proposed. Based on the 2D field model, the section impedance is obtained, and then the 3D litz wire AC resistance is obtained using the equivalent circuit. The method is experimentally verified to have high accuracy.

   Analysis of Material Mixtures for the Characteristics of a Field Coupled Current Controlled Adjustable Inductance
By Guido SCHIERLE, Michael MEISSNER, Hendrik SASS, Klaus F. HOFFMANN [View]
[Download]

Abstract: In this paper the realization of a concept for an adjustable inductance with different composites of magnetic core material is described, analyzed and discussed. An electrical circuit is used to generate a magnetic field by an additional control core which is orthogonal to the magnetic field of the load core and thereby change the inductance. It is shown that the system can be influenced in different ways by the chosen material mixtures.

   Analytical Model for 3D Geometry, Radius and DC Resistance of Arbitrary Litz Wire
By Qingchao MENG, Jürgen BIELA [View]
[Download]

Abstract: Litz wire is frequently used for reducing high frequency losses in modern power electronic systems. However, due to its complex twisting procedure, the 3D geometry and the important parameters of LW such as radius and DC resistance are difficult to obtain. Therefore, the radius and DC resistance of LWs are usually measured, which is not helpful in the magnetic and converter design. To eliminate the barrier caused by the complex twisting structure of LW, this paper provides an analytical model that not only mathematically describes the 3D geometry but also calculates the radius and the DC resistance of an arbitrary LW with less than 4\% error proved by experiments. With the proposed model, a more flexible and accurate design and optimization for magnetics and converters can be achieved.

   Coupled PFC inductor for 22 kW on-board charger using PCB technology
By Stefan HOFFMANN, Eckart HOENE [View]
[Download]

Abstract: The concept of the coupled inductor is adapted to operate in continuous current mode in a 22 kW on-board charger. In order to obtain a component with a very short thermal path, the two inductor branches are each divided into two sub-windings. Besides the design, the focus is on uniform flux distribution in the four winding legs and the wiring of the sub-windings. The windings can be manufactured using PCB technology, making the component entirely machine-manufactured and therefore cost-effective. The designed PFC inductor is validated with measurement.

   Design Approaches for Nonlinear Inductors with a Stepped Air-Gap
By Jeremias KAISER, Thomas DÜRBAUM [View]
[Download]

Abstract: This paper presents design approaches to build a nonlinear inductor with a stepped air gap for PWM converters in CCM or BCM/DCM operation. The investigations are based on a reluctance model to derive the necessary correlations between geometry and inductance characteristics. Based on this, design approaches are developed to move from an existing conventional coil to a nonlinear one with a stepped air gap. Finally, the results are verified by comparison to numerical simulations and measurements.

   Eddy currents in rectangular conductors: Analytical 2D loss model in the context of magnetic component design
By Thomas EWALD, Jürgen BIELA [View]
[Download]

Abstract: The calculation of high-frequency windinglosses caused by eddy currents in solid conductors with circularcross-section has already been discussed sufficientlyoften. However, there is currently no such treatment forconductors with rectangular cross-section in literature. Inthis article such a model is presented, which is based ona simplified two-dimensional formulation for the magneticfield inside conductors with rectangular cross-section. Similarto existing circular conductor models, the formulationis linked to an external, magneto-quasi-static field in thecore window by means of boundary conditions, whichmakes it possible to a certain degree to calculate thefrequency-dependent eddy current losses.

   Estimation of Leakage Inductance in High-frequency Three-Winding Transformers for Electric Vehicle On-board Chargers
By Ioannis KOUGIOULIS, Amedeo VANNINI, Anirban PAL, Pat WHEELER, Md Rishad AHMED [View]
[Download]

Abstract: This paper reviews several methods to estimate the equivalent circuit model parameters of high frequency three-winding transformers, considering measurement accuracy and tolerance to measurement errors. First, several equivalent circuit models of the three winding transformer are reviewed and different methods to estimate the model parameters are investigated. A sensitivity analysis is performed to evaluate the accuracy of each method and its tolerance to measurement errors. In addition, transformer designs with E-cores and U-cores are simulated in ANSYS and their leakage inductance parameters are estimated for various winding arrangements. A three-winding transformer for EV charger application is simulated and the impact of the transformer model on theconverter operation is discussed. Finally, a three-winding transformer prototype is built and tested to compare the accuracy of each estimation method with respect to the 3-D FE simulations. The comparison shows that methods based on one-port impedance measurements yield the most accurate estimation results.

   Experimental Demonstration of the Transformer Interwinding Capacitance Voltage Waveform in an Isolated Full-Bridge Forward Converter
By Claus KJELDSEN, Christian ØSTERGAARD [View]
[Download]

Abstract: A thorough analysis of the transformer interwinding capacitance voltage waveform is presented when an isolated full-bridge forward converter is operated as hard-switched and phase-shifted. A large voltage variation is observed during steady-state, especially in scenarios with a large transformer turns-ratio. It is presented that a split inductor theoretically eliminates the voltage variation when the converter is hard-switched. When the converter is phase-shifted, the voltage variation is reduced while making it independent on the transformer turns-ratio.Measurements of the transformer interwinding capacitance voltage is carried out in four operation scenarios. The measured and calculated waveforms matches with off-sets of only 1.3 \% when the converter is hard-switched, while the maximum off-set is 4.2 V when phase-shifted. A second-order resonance is present in the measured voltage waveform. It is experimentally demonstrated that the amplitude of the second-order resonance is reduced when using a split inductor by a factor of 2.7 and 1.8 when hard-switched or phase-shifted, respectively.

   Fully Analytical Double 2D Model for a Capacitive Equivalent Circuit of Transformers
By Bastian KORTHAUER, Jürgen BIELA [View]
[Download]

Abstract: This paper presents a novel analytic model to derive the equivalent circuit (EC) of a power electronic transformer using a double 2D (D2D) approach. The model considers an arbitrary core potential, different winding heights as well as different permittivities of the wire insulation, the bobbin and the ambient insulation material.

   Highly Efficient and Flexible Optimization Algorithm for Magnetic Components in Power Electronics with Comprehensive Thermal and Power Loss Analysis
By Sven FIESSER, Ulf SCHWALBE [View]
[Download]

Abstract: This paper presents an algorithm for the optimization of magnetic components in power electronics which includes a comprehensive analysis of the power losses and the temperature rise using dimensionless numbers for natural and forced convection. The results show that this approach is highly efficient and comparatively accurate.

   Improved Analytical Core Temperature Prediction Based on Estimation of the Non-Uniform Flux Distribution
By Lucia CLAVERO, Alberto DELGADO, Pedro ALOU, Miroljub BAKIC, Thiwanka WIJEKOON [View]
[Download]

Abstract: Accurate modeling of the losses generated in magnetic components is becoming critical as power and operating frequencies ramp up. Core loss models in literature focus on the calculation of losses per volume unit, but the non-uniform distribution due to the material properties and geometry is barely addressed. In this paper a model for the losses of the ferrite core in planar magnetic components is presented, which provides a fast and accurate estimation of the non-uniform flux distribution. The magnetic model is coupled to a thermal model to obtain the temperature distribution. The coupled model is verified using Finite Element simulations, demonstratingan error of 3 \% with execution time of seconds.

   Long-term testing results of a high-performance 450 V Polymer Aluminium Electrolytic Capacitor
By Shova NEUPANE, Esther Olawale OLUWATOYIN, Vadzim ADASHKEVICH, William GREENBANK, Liciana TAVARES, Thomas EBEL [View]
[Download]

Abstract: The lifetime behavior of encapsulated 450V polymer Aluminium electrolytic capacitors was measured over ~1800 hours in an aging test under a high temperature of 105°C and a high-voltage of 450V. Leakage current, capacitance, and equivalent series resistance were measured at regular intervals throughout the study and show a successful implementation of two different additives containing Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS).

   Method for reducing eddy currents losses in planar transformer windings
By Andres REVILLA AGUILAR, Szymon BECZKOWSKI, Stig MUNK-NIELSEN, Hongbo ZHAO [View]
[Download]

Abstract: This article presents a method for reducing AC resistance in planar transformer windings by using a new type of cut-winding structure. The proposed winding modification aims at improving the current density distribution in the winding's area, by increasing the resistance of the eddy current's loop and organizing the proximity effects between primary and secondary interleaved layers. A physical prototype with the modified windings has been implemented on a 2 kVA planar transformer and compared with common planar windings. 2D FEA simulations has been used to investigate the proposed technique. Empirical measurements on the physical prototypes shows that the modified cut-windings present a 45\% lower AC resistance under full load.

   Model Approach for Simulation of the Large-Signal Performance ofInductive Components Using a N87 Core
By Peter ZACHARIAS [View]
[Download]

Abstract: In addition to the so-called Steinmetz formula, there are various approaches for describing theelectrical performance of inductive components with ferromagnetic cores. The following articleaims at developing a model for the simulation of the v(i) characteristic in power electronic circuits.Information on the small and large signal from data sheet data and from own measurements isused.

   Modeling of litz-wire losses in high-power medium-frequency transformers
By Thomas GRADINGER, Marko MOGOROVIC [View]
[Download]

Abstract: A comprehensive closed-form analytical model for litz-wire losses in windings of medium-frequency transformers is provided. It is suitable for optimization, reasonably simple, yet physics based and thus fairly general, and covers in particular the effects of practical importance in the windings of medium- and high-frequency transformers. The model covers wire level, bundle-level, subbundle level, and strand-level proximity effect. It is assumed that at each level, the subconductors of the next lower level are twisted only, without radial transposition. For more than five subconductors, this leads to extra losses due to high reversed current in the inner subconductors. A first experimental comparison is provided for the winding arrangement of a medium-frequency transformer. It is shown that the wire-level proximity effect plays an important role for a wire of six top-level bundles and significantly improves the agreement with the measurements as compared with a model of strand-level proximity effect only.

   Optimal Design of a Coupled Inductor for ZVS DCDC
By Lukas KEUCK, Martin DIERKES, Mathias WEBER [View]
[Download]

Abstract: Coupling inductors of DC-DC converters are a well-known approach to reduce the size and costs of the magnetic components. However, the common approaches are not suited for ZVS designs due to the large current ripple. In this study a coupled inductor concept is presented that is optimized for such a ZVS design. Experimental results proved a reduction in size by 25\% and losses by 17\%.

   Optimisation of Magnetic Loss Trade-offs in High-Frequency Litz Wire Transformers
By Hans WOUTERS, Xiaobing SHEN, Hassan PERVAIZ, Wilmar MARTINEZ [View]
[Download]

Abstract: Magnetic design poses numerous challenges, such as oversized components and excessive losses. Based on validated magnetic loss models, this paper presents an extensive analysis of the trade-offs in high-frequency transformer designs. Specifically, the trade-offs between core losses and winding losses are demonstrated in both analytical models and based on experimental data. From the validated loss models, this paper presents a practical and fast magnetic design method for high-frequency transformers in isolated DC-DC converters. The methodology enables a flexible design of litz wire windings and planar transformers based on an exhaustive search that identifies the Pareto optimal combinations of design parameters. Different core materials, shapes, sizes, and winding types can be considered, whereby four Pareto optimal planar transformers of different sizes are constructed. Finally, an optimised transformer is implemented in a 600 W dual active bridge converter operating at 460 V, with thermal images and waveforms indicating its operation.

   Ripple Cancellation of PWM Power Converters by Magnetically IntegratedFilter Technology
By Peter ZACHARIAS, Christian NOEDING, Alejandro AGANZA [View]
[Download]

Abstract: If the ripple current is subtracted from the output current of a PWM converter after separation ofthe low-frequency component, it is theoretically possible to generate an output current free ofripple. In the following, it is shown how the number of components as well as the constructionvolume and weight can be significantly reduced by combining the inductive components required for this purpose into one single component.

   Single-stage single-switch curved air gap power factor correction integrated flyback transformer design for lighting equipment power applications
By Wai Keung MO, Kasper M PAASCH, Thomas EBEL [View]
[Download]

Abstract: The paper presents a design of a single-stage single switch flyback transformer, which incorporates two auxiliary windings and a curved air gap. The main objective of the design is to enhance transformer efficiency and reduce harmonic current. To validate the proposed design, a 250W prototype circuit was constructed , using four ferrite materials. The results obtained from both FEM simulations and experiments are promising, indicating the effectiveness of the design. The proposed transformer configuration demonstrated improved efficiency and a reduction in harmonic current.

EPE 2023 - DS2a: Passive Components
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2023 ECCE Europe - Conference > EPE 2023 - Topic 01: Devices, Packaging and System Integration > EPE 2023 - DS2a: Passive Components
	[return to parent folder]

	A Half-turn Winding Layout in Planar Transformers By Chao LIU, Pinhe WANG, Zhe ZHANG, Jiasheng HUANG, Michael ANDERSEN, Gabriel ZSURZSAN, Ziwei OUYANG	[View] [Download]
Abstract: This paper presents an analysis of the current distribution on the parallel conductors of typical interleaved planar transformers. Through the investigation, it is discovered that the S-P-S-P-S winding layout with 'n+1' parallel layers exhibits a half-turn winding current distribution, resulting in lower AC resistance. Simulation and experiment results are used to validate the current distribution in the proposed half-turn transformer, demonstrating a nearly 20\% reduction in winding loss and leakage inductance compared to conventional layouts.

	A High Frequency Magnetic Test Bench with Fast Isothermal Measurements for Large Cores By Anartz AGOTE, Asier ARRUTI, Iosu AIZPURU	[View] [Download]
Abstract: This paper presents a magnetic core test-bench that has been developed for high-frequency measurements. The bench is able to perform tests at 1 MHz, 300 V and in a range of 20 ºC to 150 ºC. It exhibits precise temperature control and possesses a high-power capacity, making it suitable for testing large scale magnetic cores. Comprehensive tests were conducted to validate the capabilities and performance of the test bench, and the obtained results are presented and discussed

	An improved approach for litz wire loss calculation based on segmented equivalent circuit By Yueyin WANG, Wu CHEN, Zhan SHEN, Jianxi LAN	[View] [Download]
Abstract: Litz wires are often used to reduce AC losses in high frequency transformers. However, modeling the AC resistance is still chal-lenging. In this paper, a new analytical calculation method is proposed. Based on the 2D field model, the section impedance is obtained, and then the 3D litz wire AC resistance is obtained using the equivalent circuit. The method is experimentally verified to have high accuracy.

	Analysis of Material Mixtures for the Characteristics of a Field Coupled Current Controlled Adjustable Inductance By Guido SCHIERLE, Michael MEISSNER, Hendrik SASS, Klaus F. HOFFMANN	[View] [Download]
Abstract: In this paper the realization of a concept for an adjustable inductance with different composites of magnetic core material is described, analyzed and discussed. An electrical circuit is used to generate a magnetic field by an additional control core which is orthogonal to the magnetic field of the load core and thereby change the inductance. It is shown that the system can be influenced in different ways by the chosen material mixtures.

	Analytical Model for 3D Geometry, Radius and DC Resistance of Arbitrary Litz Wire By Qingchao MENG, Jürgen BIELA	[View] [Download]
Abstract: Litz wire is frequently used for reducing high frequency losses in modern power electronic systems. However, due to its complex twisting procedure, the 3D geometry and the important parameters of LW such as radius and DC resistance are difficult to obtain. Therefore, the radius and DC resistance of LWs are usually measured, which is not helpful in the magnetic and converter design. To eliminate the barrier caused by the complex twisting structure of LW, this paper provides an analytical model that not only mathematically describes the 3D geometry but also calculates the radius and the DC resistance of an arbitrary LW with less than 4\% error proved by experiments. With the proposed model, a more flexible and accurate design and optimization for magnetics and converters can be achieved.

	Coupled PFC inductor for 22 kW on-board charger using PCB technology By Stefan HOFFMANN, Eckart HOENE	[View] [Download]
Abstract: The concept of the coupled inductor is adapted to operate in continuous current mode in a 22 kW on-board charger. In order to obtain a component with a very short thermal path, the two inductor branches are each divided into two sub-windings. Besides the design, the focus is on uniform flux distribution in the four winding legs and the wiring of the sub-windings. The windings can be manufactured using PCB technology, making the component entirely machine-manufactured and therefore cost-effective. The designed PFC inductor is validated with measurement.

	Design Approaches for Nonlinear Inductors with a Stepped Air-Gap By Jeremias KAISER, Thomas DÜRBAUM	[View] [Download]
Abstract: This paper presents design approaches to build a nonlinear inductor with a stepped air gap for PWM converters in CCM or BCM/DCM operation. The investigations are based on a reluctance model to derive the necessary correlations between geometry and inductance characteristics. Based on this, design approaches are developed to move from an existing conventional coil to a nonlinear one with a stepped air gap. Finally, the results are verified by comparison to numerical simulations and measurements.

	Eddy currents in rectangular conductors: Analytical 2D loss model in the context of magnetic component design By Thomas EWALD, Jürgen BIELA	[View] [Download]
Abstract: The calculation of high-frequency windinglosses caused by eddy currents in solid conductors with circularcross-section has already been discussed sufficientlyoften. However, there is currently no such treatment forconductors with rectangular cross-section in literature. Inthis article such a model is presented, which is based ona simplified two-dimensional formulation for the magneticfield inside conductors with rectangular cross-section. Similarto existing circular conductor models, the formulationis linked to an external, magneto-quasi-static field in thecore window by means of boundary conditions, whichmakes it possible to a certain degree to calculate thefrequency-dependent eddy current losses.

	Estimation of Leakage Inductance in High-frequency Three-Winding Transformers for Electric Vehicle On-board Chargers By Ioannis KOUGIOULIS, Amedeo VANNINI, Anirban PAL, Pat WHEELER, Md Rishad AHMED	[View] [Download]
Abstract: This paper reviews several methods to estimate the equivalent circuit model parameters of high frequency three-winding transformers, considering measurement accuracy and tolerance to measurement errors. First, several equivalent circuit models of the three winding transformer are reviewed and different methods to estimate the model parameters are investigated. A sensitivity analysis is performed to evaluate the accuracy of each method and its tolerance to measurement errors. In addition, transformer designs with E-cores and U-cores are simulated in ANSYS and their leakage inductance parameters are estimated for various winding arrangements. A three-winding transformer for EV charger application is simulated and the impact of the transformer model on theconverter operation is discussed. Finally, a three-winding transformer prototype is built and tested to compare the accuracy of each estimation method with respect to the 3-D FE simulations. The comparison shows that methods based on one-port impedance measurements yield the most accurate estimation results.

	Experimental Demonstration of the Transformer Interwinding Capacitance Voltage Waveform in an Isolated Full-Bridge Forward Converter By Claus KJELDSEN, Christian ØSTERGAARD	[View] [Download]
Abstract: A thorough analysis of the transformer interwinding capacitance voltage waveform is presented when an isolated full-bridge forward converter is operated as hard-switched and phase-shifted. A large voltage variation is observed during steady-state, especially in scenarios with a large transformer turns-ratio. It is presented that a split inductor theoretically eliminates the voltage variation when the converter is hard-switched. When the converter is phase-shifted, the voltage variation is reduced while making it independent on the transformer turns-ratio.Measurements of the transformer interwinding capacitance voltage is carried out in four operation scenarios. The measured and calculated waveforms matches with off-sets of only 1.3 \% when the converter is hard-switched, while the maximum off-set is 4.2 V when phase-shifted. A second-order resonance is present in the measured voltage waveform. It is experimentally demonstrated that the amplitude of the second-order resonance is reduced when using a split inductor by a factor of 2.7 and 1.8 when hard-switched or phase-shifted, respectively.

	Fully Analytical Double 2D Model for a Capacitive Equivalent Circuit of Transformers By Bastian KORTHAUER, Jürgen BIELA	[View] [Download]
Abstract: This paper presents a novel analytic model to derive the equivalent circuit (EC) of a power electronic transformer using a double 2D (D2D) approach. The model considers an arbitrary core potential, different winding heights as well as different permittivities of the wire insulation, the bobbin and the ambient insulation material.

	Highly Efficient and Flexible Optimization Algorithm for Magnetic Components in Power Electronics with Comprehensive Thermal and Power Loss Analysis By Sven FIESSER, Ulf SCHWALBE	[View] [Download]
Abstract: This paper presents an algorithm for the optimization of magnetic components in power electronics which includes a comprehensive analysis of the power losses and the temperature rise using dimensionless numbers for natural and forced convection. The results show that this approach is highly efficient and comparatively accurate.

	Improved Analytical Core Temperature Prediction Based on Estimation of the Non-Uniform Flux Distribution By Lucia CLAVERO, Alberto DELGADO, Pedro ALOU, Miroljub BAKIC, Thiwanka WIJEKOON	[View] [Download]
Abstract: Accurate modeling of the losses generated in magnetic components is becoming critical as power and operating frequencies ramp up. Core loss models in literature focus on the calculation of losses per volume unit, but the non-uniform distribution due to the material properties and geometry is barely addressed. In this paper a model for the losses of the ferrite core in planar magnetic components is presented, which provides a fast and accurate estimation of the non-uniform flux distribution. The magnetic model is coupled to a thermal model to obtain the temperature distribution. The coupled model is verified using Finite Element simulations, demonstratingan error of 3 \% with execution time of seconds.

	Long-term testing results of a high-performance 450 V Polymer Aluminium Electrolytic Capacitor By Shova NEUPANE, Esther Olawale OLUWATOYIN, Vadzim ADASHKEVICH, William GREENBANK, Liciana TAVARES, Thomas EBEL	[View] [Download]
Abstract: The lifetime behavior of encapsulated 450V polymer Aluminium electrolytic capacitors was measured over ~1800 hours in an aging test under a high temperature of 105°C and a high-voltage of 450V. Leakage current, capacitance, and equivalent series resistance were measured at regular intervals throughout the study and show a successful implementation of two different additives containing Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS).

	Method for reducing eddy currents losses in planar transformer windings By Andres REVILLA AGUILAR, Szymon BECZKOWSKI, Stig MUNK-NIELSEN, Hongbo ZHAO	[View] [Download]
Abstract: This article presents a method for reducing AC resistance in planar transformer windings by using a new type of cut-winding structure. The proposed winding modification aims at improving the current density distribution in the winding's area, by increasing the resistance of the eddy current's loop and organizing the proximity effects between primary and secondary interleaved layers. A physical prototype with the modified windings has been implemented on a 2 kVA planar transformer and compared with common planar windings. 2D FEA simulations has been used to investigate the proposed technique. Empirical measurements on the physical prototypes shows that the modified cut-windings present a 45\% lower AC resistance under full load.

	Model Approach for Simulation of the Large-Signal Performance ofInductive Components Using a N87 Core By Peter ZACHARIAS	[View] [Download]
Abstract: In addition to the so-called Steinmetz formula, there are various approaches for describing theelectrical performance of inductive components with ferromagnetic cores. The following articleaims at developing a model for the simulation of the v(i) characteristic in power electronic circuits.Information on the small and large signal from data sheet data and from own measurements isused.

	Modeling of litz-wire losses in high-power medium-frequency transformers By Thomas GRADINGER, Marko MOGOROVIC	[View] [Download]
Abstract: A comprehensive closed-form analytical model for litz-wire losses in windings of medium-frequency transformers is provided. It is suitable for optimization, reasonably simple, yet physics based and thus fairly general, and covers in particular the effects of practical importance in the windings of medium- and high-frequency transformers. The model covers wire level, bundle-level, subbundle level, and strand-level proximity effect. It is assumed that at each level, the subconductors of the next lower level are twisted only, without radial transposition. For more than five subconductors, this leads to extra losses due to high reversed current in the inner subconductors. A first experimental comparison is provided for the winding arrangement of a medium-frequency transformer. It is shown that the wire-level proximity effect plays an important role for a wire of six top-level bundles and significantly improves the agreement with the measurements as compared with a model of strand-level proximity effect only.

	Optimal Design of a Coupled Inductor for ZVS DCDC By Lukas KEUCK, Martin DIERKES, Mathias WEBER	[View] [Download]
Abstract: Coupling inductors of DC-DC converters are a well-known approach to reduce the size and costs of the magnetic components. However, the common approaches are not suited for ZVS designs due to the large current ripple. In this study a coupled inductor concept is presented that is optimized for such a ZVS design. Experimental results proved a reduction in size by 25\% and losses by 17\%.

	Optimisation of Magnetic Loss Trade-offs in High-Frequency Litz Wire Transformers By Hans WOUTERS, Xiaobing SHEN, Hassan PERVAIZ, Wilmar MARTINEZ	[View] [Download]
Abstract: Magnetic design poses numerous challenges, such as oversized components and excessive losses. Based on validated magnetic loss models, this paper presents an extensive analysis of the trade-offs in high-frequency transformer designs. Specifically, the trade-offs between core losses and winding losses are demonstrated in both analytical models and based on experimental data. From the validated loss models, this paper presents a practical and fast magnetic design method for high-frequency transformers in isolated DC-DC converters. The methodology enables a flexible design of litz wire windings and planar transformers based on an exhaustive search that identifies the Pareto optimal combinations of design parameters. Different core materials, shapes, sizes, and winding types can be considered, whereby four Pareto optimal planar transformers of different sizes are constructed. Finally, an optimised transformer is implemented in a 600 W dual active bridge converter operating at 460 V, with thermal images and waveforms indicating its operation.

	Ripple Cancellation of PWM Power Converters by Magnetically IntegratedFilter Technology By Peter ZACHARIAS, Christian NOEDING, Alejandro AGANZA	[View] [Download]
Abstract: If the ripple current is subtracted from the output current of a PWM converter after separation ofthe low-frequency component, it is theoretically possible to generate an output current free ofripple. In the following, it is shown how the number of components as well as the constructionvolume and weight can be significantly reduced by combining the inductive components required for this purpose into one single component.

	Single-stage single-switch curved air gap power factor correction integrated flyback transformer design for lighting equipment power applications By Wai Keung MO, Kasper M PAASCH, Thomas EBEL	[View] [Download]
Abstract: The paper presents a design of a single-stage single switch flyback transformer, which incorporates two auxiliary windings and a curved air gap. The main objective of the design is to enhance transformer efficiency and reduce harmonic current. To validate the proposed design, a 250W prototype circuit was constructed , using four ferrite materials. The results obtained from both FEM simulations and experiments are promising, indicating the effectiveness of the design. The proposed transformer configuration demonstrated improved efficiency and a reduction in harmonic current.