EPE Association: EPE 2022 - DS1a: Passive Components

EPE 2022 - DS1a: Passive Components
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2022 ECCE Europe - Conference > EPE 2022 - Topic 01: Devices, Packaging and System Integration > EPE 2022 - DS1a: Passive Components

   [return to parent folder]

   A complete PFC inductor design for lighting equipment applications
By Wai Keung MO [View]
[Download]

Abstract: This paper presents the comparison of two novel air-gap inductor designs: two step air-gap solution (TSAG) and curved air gap solution (CAG). The effective mathematical inductance model of the proposal CAG design is derived and verified experimentally in terms of harmonic and EMI emissions. A complete optimal PFC inductor design procedure is given.

   A General Method to Measure Parasitic Capacitance of Transformer Using Guarding Technique
By Shaokang LUAN [View]
[Download]

Abstract: Precise, simple, and general measurement methods are essential for parasitic capacitance of transformer. Conventional two-terminal method has some limitations on the measurement of multi-winding transformer, like complex measurement processes. This paper introduces guarding technique into a new method to measure parasitic capacitance of multi-winding transformer. The principle and measurement processes of proposed three-terminal guarding method are introduced in detail. Comprehensive comparisons between two-terminal method and guarding method are made based on circuit verification and three case studies. Guarding method has high accuracy, but simpler measurement processes, and higher feasibility for multi-winding transformer compared to the conventional two-terminal method.

   A Low-Leakage, Low-Loss Magnetic Transformer Structure for High-Frequency Applications
By Allen NGUYEN [View]
[Download]

Abstract: Energy-storage transformers, such as transformers for flyback or LLC converters, have different design constraints than typical transformers. Since primary and secondary currents are not in phase, interleaving does not necessarily reduce high-frequency losses. Such transformers often must be designed with low leakage as well. In this work, we propose design guidelines for a transformer structure that uses field shaping to achieve current conduction along most of the skin of the conductors (double-sided conduction), equal current sharing between paralleled turns, even for out-of-phase currents, and near zero MMF drop across the leakage reluctance paths. The transformer therefore has low leakage inductance and low conduction loss without the use of litz wire and can be used effectively at frequencies beyond a few megahertz. Step-by-step design guidelines are proposed and a prototype transformer is built which achieves a leakage to magnetizing ratio of 1.12\%, a power loss 14-17\% of a traditional lumped-gap transformer, and current sharing variation less than 1.5\% between paralleled turns.

   A Novel Concept to Optimize Core Loss in Planar Magnetic Based on an Unbalanced-Flux- Approach
By Sobhi BARG [View]
[Download]

Abstract: this paper presents a new method to design planar magnetics. Unlike existing magnetics which have a balanced-flux distribution, the proposed method is based on the principle of unbalanced-flux distribution. The Steinmetz model, derived for this design principle, shows that the unbalanced-flux method reduces the core loss by more than 50\%. The core loss reduction brings several benefits to planar magnetics such as: high magnetic power factor, better thermal performance and larger safe operating area (SOA). The proposed method is experimentally evaluated and compared with the balanced-flux method. The obtained results confirmed the advantages of the unbalanced-flux method found from the theoretical study. The core loss is decreased by more than 50\%, the magnetic power factor is increased by 73\% and the SOA is much larger.

   An Open-Source FEM Magnetic Toolbox for Calculating Electric and Thermal Behavior of Power Electronic Magnetic Components
By Nikolas FÖRSTER [View]
[Download]

Abstract: Minimizing power losses and the thermal management are important factors in developing magnetics for power electronics. These are important to maintain the efficiency and the maximum operating temperatures of the core and conductors. To bring this calculation in the development workflow, the FEM (Finite Element Method) Magnetics Toolbox (FEMMT) will be continued. This open-source toolbox helps to automatically simulate magnetics in a guided, standardized format, requiring minimal effort. Based on the magnetoquasistatic simulation, a thermal simulation is set up. Conductor and core losses are taken from the magnetostatic simulation. The losses are homogenized inside the winding and inside the core. Thermal geometries and materials are set by script (e.g., for air gap filling and potting material), to automate the time-consuming drawing process inside the FEM tool. After simulation, the results are read back. With the help of this toolbox, which is publicly and collaboratively developed on GitHub, entireparameter sweeps can be easily performed and the simulation process is significantly speeded up.

   Analysis and Discussion of a Concept for an Adjustable Inductance Based on an Impact of an Orthogonal Magnetic Field
By Guido SCHIERLE [View]
[Download]

Abstract: In this paper the realisation of a concept for an adjustable inductance by the use of an auxiliary controlcurrent is analysed and discussed. Using a construction of two magnetic toroid cores the magnetic fieldof a load core, and by this its effective inductance, is influenced by an orthogonal magnetic field inducedby an additional control core. It will be shown that with an increase of the magnetic field generated bythe control circuit the inductance of the load circuit decreases.

   Analysis of Test Methods for Measurement of Leakage and Magnetising Inductances in Integrated Transformers
By Sajad ARAB ANSARI [View]
[Download]

Abstract: The attention in integrated transformers has increased recently. The operation of the converters with integrated transformers depends on their components' value significantly. Therefore, a sensitivity analysis is provided to find the most precise measurement method for characterization of integrated transformers, especially when they have different primary and secondary leakage inductances. The theoretical analysis is verified by simulation and experimental results.

   Analytical, FEM and Experimental Study of the Influence of the Airgap Size in Different Types of Ferrite Cores
By Asier ARRUTI [View]
[Download]

Abstract: This work reviews and compares different airgap reluctance calculation approaches with experimental results, focusing on the Schwarz-Christoffel transformation. The modelling of the airgap reluctance in two dimensions is tested against FEM simulations for typical airgap geometries. Then, an approach to obtain the three-dimensional reluctance is shown, and the limited experimental data shown in previous works is expanded to validate the different airgap calculation methods in EE cores. For the case of pot cores, a geometrical transformation is proposed and validated, allowing the application of the Schwarz-Christoffel methodology to other common core geometries.

   Characterisation of a Ferrite-Polymer based Magnetic Material
By Johan LE LESLE [View]
[Download]

Abstract: The design of highly integrated converter is more than ever a hot topic in the power electronic world.Integration also brings new challenges and opportunities for magnetic design, e.g. use of new magnetic material or innovative manufacturing process. This paper is presenting the manufacturing process and characterisation of a composite material applied to the design of a magnetic components which is fully compliant with the printed circuit board (PCB) process. This paper is presenting results of the characterisation on the ferrite powder and on the soft magnetic compound (SMC), some insight are given on the material manufacturing before presenting additional characterisation procedures, especially for core losses measurements.

   DC Bias Impact on Magnetic Core Losses at High Frequency
By Bima SANUSI [View]
[Download]

Abstract: This paper aims to provide more insight into core losses at high frequency (MHz range) with superimposed DC bias in ferrite. Inductive cancellation method is employed to reduce measurement sensitivity to phase errors. The tested MnZn ferrite has a nominal relative permeability (µr) of 1500 (core A) and 800 (core B), which was tested at frequency from 500 kHz to 3 MHz. The DC bias appears to create a shift in the Steinmetz parameters, in particular the ki and ß are affected the most. Higher Bdc creates higher losses gain and higher fsw makes the relative losses increase lower. This is a new finding. Furthermore, the Steinmetz Premagnetization Graph (SPG) with iGSE method ise used to create a core losses prediction model. A maximum error of 25\% were found. The measurement data and the built model will be published online for use by other magnetics designer.

   Frequency scaling of high-power medium-voltage medium-frequency transformers
By Thomas GRADINGER [View]
[Download]

Abstract: This paper provides a fundamental insight into the scaling laws of medium-frequency transformers (MFTs). Economic MFTs are a key enabler for solid-state transformers and viable MVDC solutions. An understanding of the influences on the MFT cost structure, and of the limitations to the reduction of size, mass, and cost, is therefore key. Simplified scaling laws are developed that suggest a potential of an increase in switching frequency to improve the MFT performance metrics. They suggest that for fixed MFT geometry, an increase in frequency can lead to lower losses under constrained inductances. The scaling laws also show that a core-size reduction at a given frequency must always be accompanied by increasing core losses. In practical MFT design, size reduction is only observed up to a certain 'scaling saturation' frequency. In the studied examples featuring nanocrystalline cores, it is located near 7 kHz. Insight into the scaling behavior is provided by the analysis of the constraint functions used in the MFT optimization. A constrained loss ratio may limit the designs at all frequencies and inhibit core-size reduction. The 'scaling saturation' frequency corresponds to a transition between saturation limit and thermal limit of the core, and can be shifted upward by improved core cooling. This enables an attractive compromise between cost savings and loss increase, and shows the importance of sufficient core cooling.

   Generalized Core and Winding Area Ratio - Trends for Inductors and Transformers in Power Electronics with High Switching Frequencies
By Siqi LIN [View]
[Download]

Abstract: The paper describes the general trend for the design of core shapes for inductors and transformers inpower electronic applications under the influence of increasing switching frequencies. The focus of the paper is on the ratio of the winding window and the core cross sectional area to identify the current trends and new shapes for magnetic circuits.

   Impact of aluminum casing on high-frequency transformer leakage inductance and AC resistance
By Reda BAKRI [View]
[Download]

Abstract: High-Frequency (HF) transformer is a central part of isolated HF power converters. Its parameters, in particular leakage inductance and losses, have a significant impact on the overall converter performances. With the increase of switching frequencies linked to the use of SiC and GaN based active devices, the control of the HF transformer parameters becomes essential. A HF transformer is usually designed without considering its surrounding. However, the latter can have a significant impact on the transformer's performance. In this paper, the effect of an aluminum casing surrounding the transformer is studied and quantified for two parameters: The transformer leakage inductance and the supplementary losses. The goal is to consider the casing effect in the early design stage of power converters.

   Inductance Estimation for Square-Shaped Multilayer Planar Windings
By Theofilos PAPADOPOULOS [View]
[Download]

Abstract: In this paper the inductance of square-shaped multilayer planar windings (MLPW) for power applications is investigated. Three well-known equations Wheeler's, Rosa's, and Monomial, which are suitable for single-layer (L1) planar windings, are extended to properly appertain to multilayer architectures. The proposed procedure is verified for two-layer (L2) windings, and the extension to three-layers (L3) or more is discussed, for different values of the geometric parameters. Furthermore, the dependance of thecoupling factor k with respect to the distance between the layers is investigated for L2. Finally, an experimental verification is carried out, for a number of selected windings.

   Loss characterization methodology for soft magnetic nano-crystalline tape materials in coupled inductors
By David BOHNE [View]
[Download]

Abstract: In this paper a four-wire magnetic core loss measurement test bench for waveforms typical for two-phase Coupled Inductors is presented. A low permeability nano-crystalline ribbon material is investigated. The advantage of the new test bench is its low measurement time of seconds for multiple operating points at good accuracy. Due to the improvements in preventing disturbances, the measurements are reliable and reproducible.

   Measurement Method for Simple Determination of Sinusoidal Large Signal Losses in Inductive Components
By Peter ZACHARIAS [View]
[Download]

Abstract: In this work, a resonance-based losses measurement method is shown suitable for the power dissipation measurement of small and large inductive components under sinusoidal test voltage. In a resonance-based measurement method, the magnetic losses of inductive devices are transformed to the measurement of electrical RMS magnitudes through the device under test. The sinusoidal shape of the test voltage is therefore inherently guaranteed in the measurement procedure.

   Modeling the arrangement of drill holes for orthogonal biasing in controllable inductors for power electronic converters
By Jonas PFEIFFER [View]
[Download]

Abstract: Magnetic devices are essential components of power electronic converters. Unfortunately, they usuallyare also the bulkiest and heaviest components in the converter system. Controllable magnetic devicesusing active premagnetization are a promising approach regarding further volume and weightreduction. One method of active premagnetization is orthogonal biasing. To be able to use thismethod, drill holes in the ferrite core material are necessary. Because of the material's fragility andbrittleness, manufacturing ferrite cores is a difficult and expensive process. For this reason, aneffective arrangement of the drill holes is critical.In this paper a basic model of drill hole arrangement based on congruent circle packing is presentedfor circular and square core cross sections. 2D-FEM-simulations and measurement results are madefor comparison and verification. The deviations between calculation and measurement results arediscussed and opportunities for model improvement are given.

   New Analytical Model for Calculating HF-Losses in Litz Wire Regions Located Outside the E/U-CoreWindow of Transformers
By Qingchao MENG [View]
[Download]

Abstract: Litz wire is essential for reducing high-frequency losses in medium frequency transformers, which arebuilt often with 'E' or 'U' shaped cores. Many analytical models focus only on the winding section inside the core window, where the winding is completely enclosed by the core. The losses of the winding section outside the core window are not determined separately. This paper compares the losses of both winding sections and provides an accurate and fast loss model for the winding section outside the core window. The error of the model is less than 5\%, which is much smaller than the 1D field model (up to 30\%). Moreover, to compute the total winding losses the model requires about 90 µs, which is comparable to the time consumed by the 1D field model (72 µs on a standard laptop with a 4.8GHz,4-core CPU and a 16GB RAM).

   PCB Layer Optimization of Planar Medium Frequency Transformer for On-Board EV Chargers
By Fabian GROON [View]
[Download]

Abstract: Planar medium frequency transformer (MFT) is a promising solution for on-board electric vehicle (EV)chargers, to achieve high power density and high efficiency. The trend towards higher power densities and higher efficiencies exposes a number of limitations on conventional litz wire transformers, especially for increasing the current density. Litz wire current density is limited by the temperature, due to poor thermal management capabilities. PCBs, however, have better thermal management capabilities, which allows for higher current densities. This paper optimizes planar MFT windings focusing on maximizing current density and the simplicity of the implementation. The losses, power density and thermal constraints are investigated and a pareto-front is created based on optimal solutions. High efficiency and power densities are achieved from 2D/3D FEM simulations. A solution within thermal constraints is selected and a prototype is built based on similar ratings. Tests with different current densities are carried out on the prototype and the temperatures are compared. The results verify that planar MFT with high current densities are feasible solutions for high efficiency and high power density MFTs.

   Substitution of Nanocrystalline Toroid by Laminated Ferrite Toroid in the Application of a Common-Mode Choke
By Lukas REISSENWEBER [View]
[Download]

Abstract: In this work, it is investigated if a nanocrystalline toroid of a common-mode (CM) choke can be substituted by a laminated ferrite toroid. Small-signal measurement results for the complex impedance, of laminated toroidal cores of material T38 with different diameters and thicknesses at 25 °C and 100 °C are presented. Further the calculated attenuation and the complex permeability are shown. Based on the obtained material data, a CM choke made of laminated ferrite cores is designed and analyzed. The focus is thereby on the comparison with the nanocrystalline CM choke.

   The Variation of Core Loss in High-Frequency Transformers Under Different Load Conditions
By Navid RASEKH [View]
[Download]

Abstract: Typically, the core loss of the high-frequency (HF) transformers is considered constant regardless of the load condition on the secondary side. This paper indicates that the various load conditions can affect the core loss in HF transformers due to the variation of winding parasitics elements and subsequently the transformer's excitation voltage and current waveforms, and the field interactions between the primary and secondary windings and between the windings and core. The contribution of this work is demonstrating the core loss variation depending on different load conditions in HF transformers, which is not commonly assessed and considered in previous studies. The captured experimental results are compared with the three-dimensional (3D) finite element analysis (FEA) results conducted in Ansys Maxwell, to provide a better comprehension.

EPE 2022 - DS1a: Passive Components
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2022 ECCE Europe - Conference > EPE 2022 - Topic 01: Devices, Packaging and System Integration > EPE 2022 - DS1a: Passive Components
	[return to parent folder]

	A complete PFC inductor design for lighting equipment applications By Wai Keung MO	[View] [Download]
Abstract: This paper presents the comparison of two novel air-gap inductor designs: two step air-gap solution (TSAG) and curved air gap solution (CAG). The effective mathematical inductance model of the proposal CAG design is derived and verified experimentally in terms of harmonic and EMI emissions. A complete optimal PFC inductor design procedure is given.

	A General Method to Measure Parasitic Capacitance of Transformer Using Guarding Technique By Shaokang LUAN	[View] [Download]
Abstract: Precise, simple, and general measurement methods are essential for parasitic capacitance of transformer. Conventional two-terminal method has some limitations on the measurement of multi-winding transformer, like complex measurement processes. This paper introduces guarding technique into a new method to measure parasitic capacitance of multi-winding transformer. The principle and measurement processes of proposed three-terminal guarding method are introduced in detail. Comprehensive comparisons between two-terminal method and guarding method are made based on circuit verification and three case studies. Guarding method has high accuracy, but simpler measurement processes, and higher feasibility for multi-winding transformer compared to the conventional two-terminal method.

	A Low-Leakage, Low-Loss Magnetic Transformer Structure for High-Frequency Applications By Allen NGUYEN	[View] [Download]
Abstract: Energy-storage transformers, such as transformers for flyback or LLC converters, have different design constraints than typical transformers. Since primary and secondary currents are not in phase, interleaving does not necessarily reduce high-frequency losses. Such transformers often must be designed with low leakage as well. In this work, we propose design guidelines for a transformer structure that uses field shaping to achieve current conduction along most of the skin of the conductors (double-sided conduction), equal current sharing between paralleled turns, even for out-of-phase currents, and near zero MMF drop across the leakage reluctance paths. The transformer therefore has low leakage inductance and low conduction loss without the use of litz wire and can be used effectively at frequencies beyond a few megahertz. Step-by-step design guidelines are proposed and a prototype transformer is built which achieves a leakage to magnetizing ratio of 1.12\%, a power loss 14-17\% of a traditional lumped-gap transformer, and current sharing variation less than 1.5\% between paralleled turns.

	A Novel Concept to Optimize Core Loss in Planar Magnetic Based on an Unbalanced-Flux- Approach By Sobhi BARG	[View] [Download]
Abstract: this paper presents a new method to design planar magnetics. Unlike existing magnetics which have a balanced-flux distribution, the proposed method is based on the principle of unbalanced-flux distribution. The Steinmetz model, derived for this design principle, shows that the unbalanced-flux method reduces the core loss by more than 50\%. The core loss reduction brings several benefits to planar magnetics such as: high magnetic power factor, better thermal performance and larger safe operating area (SOA). The proposed method is experimentally evaluated and compared with the balanced-flux method. The obtained results confirmed the advantages of the unbalanced-flux method found from the theoretical study. The core loss is decreased by more than 50\%, the magnetic power factor is increased by 73\% and the SOA is much larger.

	An Open-Source FEM Magnetic Toolbox for Calculating Electric and Thermal Behavior of Power Electronic Magnetic Components By Nikolas FÖRSTER	[View] [Download]
Abstract: Minimizing power losses and the thermal management are important factors in developing magnetics for power electronics. These are important to maintain the efficiency and the maximum operating temperatures of the core and conductors. To bring this calculation in the development workflow, the FEM (Finite Element Method) Magnetics Toolbox (FEMMT) will be continued. This open-source toolbox helps to automatically simulate magnetics in a guided, standardized format, requiring minimal effort. Based on the magnetoquasistatic simulation, a thermal simulation is set up. Conductor and core losses are taken from the magnetostatic simulation. The losses are homogenized inside the winding and inside the core. Thermal geometries and materials are set by script (e.g., for air gap filling and potting material), to automate the time-consuming drawing process inside the FEM tool. After simulation, the results are read back. With the help of this toolbox, which is publicly and collaboratively developed on GitHub, entireparameter sweeps can be easily performed and the simulation process is significantly speeded up.

	Analysis and Discussion of a Concept for an Adjustable Inductance Based on an Impact of an Orthogonal Magnetic Field By Guido SCHIERLE	[View] [Download]
Abstract: In this paper the realisation of a concept for an adjustable inductance by the use of an auxiliary controlcurrent is analysed and discussed. Using a construction of two magnetic toroid cores the magnetic fieldof a load core, and by this its effective inductance, is influenced by an orthogonal magnetic field inducedby an additional control core. It will be shown that with an increase of the magnetic field generated bythe control circuit the inductance of the load circuit decreases.

	Analysis of Test Methods for Measurement of Leakage and Magnetising Inductances in Integrated Transformers By Sajad ARAB ANSARI	[View] [Download]
Abstract: The attention in integrated transformers has increased recently. The operation of the converters with integrated transformers depends on their components' value significantly. Therefore, a sensitivity analysis is provided to find the most precise measurement method for characterization of integrated transformers, especially when they have different primary and secondary leakage inductances. The theoretical analysis is verified by simulation and experimental results.

	Analytical, FEM and Experimental Study of the Influence of the Airgap Size in Different Types of Ferrite Cores By Asier ARRUTI	[View] [Download]
Abstract: This work reviews and compares different airgap reluctance calculation approaches with experimental results, focusing on the Schwarz-Christoffel transformation. The modelling of the airgap reluctance in two dimensions is tested against FEM simulations for typical airgap geometries. Then, an approach to obtain the three-dimensional reluctance is shown, and the limited experimental data shown in previous works is expanded to validate the different airgap calculation methods in EE cores. For the case of pot cores, a geometrical transformation is proposed and validated, allowing the application of the Schwarz-Christoffel methodology to other common core geometries.

	Characterisation of a Ferrite-Polymer based Magnetic Material By Johan LE LESLE	[View] [Download]
Abstract: The design of highly integrated converter is more than ever a hot topic in the power electronic world.Integration also brings new challenges and opportunities for magnetic design, e.g. use of new magnetic material or innovative manufacturing process. This paper is presenting the manufacturing process and characterisation of a composite material applied to the design of a magnetic components which is fully compliant with the printed circuit board (PCB) process. This paper is presenting results of the characterisation on the ferrite powder and on the soft magnetic compound (SMC), some insight are given on the material manufacturing before presenting additional characterisation procedures, especially for core losses measurements.

	DC Bias Impact on Magnetic Core Losses at High Frequency By Bima SANUSI	[View] [Download]
Abstract: This paper aims to provide more insight into core losses at high frequency (MHz range) with superimposed DC bias in ferrite. Inductive cancellation method is employed to reduce measurement sensitivity to phase errors. The tested MnZn ferrite has a nominal relative permeability (µr) of 1500 (core A) and 800 (core B), which was tested at frequency from 500 kHz to 3 MHz. The DC bias appears to create a shift in the Steinmetz parameters, in particular the ki and ß are affected the most. Higher Bdc creates higher losses gain and higher fsw makes the relative losses increase lower. This is a new finding. Furthermore, the Steinmetz Premagnetization Graph (SPG) with iGSE method ise used to create a core losses prediction model. A maximum error of 25\% were found. The measurement data and the built model will be published online for use by other magnetics designer.

	Frequency scaling of high-power medium-voltage medium-frequency transformers By Thomas GRADINGER	[View] [Download]
Abstract: This paper provides a fundamental insight into the scaling laws of medium-frequency transformers (MFTs). Economic MFTs are a key enabler for solid-state transformers and viable MVDC solutions. An understanding of the influences on the MFT cost structure, and of the limitations to the reduction of size, mass, and cost, is therefore key. Simplified scaling laws are developed that suggest a potential of an increase in switching frequency to improve the MFT performance metrics. They suggest that for fixed MFT geometry, an increase in frequency can lead to lower losses under constrained inductances. The scaling laws also show that a core-size reduction at a given frequency must always be accompanied by increasing core losses. In practical MFT design, size reduction is only observed up to a certain 'scaling saturation' frequency. In the studied examples featuring nanocrystalline cores, it is located near 7 kHz. Insight into the scaling behavior is provided by the analysis of the constraint functions used in the MFT optimization. A constrained loss ratio may limit the designs at all frequencies and inhibit core-size reduction. The 'scaling saturation' frequency corresponds to a transition between saturation limit and thermal limit of the core, and can be shifted upward by improved core cooling. This enables an attractive compromise between cost savings and loss increase, and shows the importance of sufficient core cooling.

	Generalized Core and Winding Area Ratio - Trends for Inductors and Transformers in Power Electronics with High Switching Frequencies By Siqi LIN	[View] [Download]
Abstract: The paper describes the general trend for the design of core shapes for inductors and transformers inpower electronic applications under the influence of increasing switching frequencies. The focus of the paper is on the ratio of the winding window and the core cross sectional area to identify the current trends and new shapes for magnetic circuits.

	Impact of aluminum casing on high-frequency transformer leakage inductance and AC resistance By Reda BAKRI	[View] [Download]
Abstract: High-Frequency (HF) transformer is a central part of isolated HF power converters. Its parameters, in particular leakage inductance and losses, have a significant impact on the overall converter performances. With the increase of switching frequencies linked to the use of SiC and GaN based active devices, the control of the HF transformer parameters becomes essential. A HF transformer is usually designed without considering its surrounding. However, the latter can have a significant impact on the transformer's performance. In this paper, the effect of an aluminum casing surrounding the transformer is studied and quantified for two parameters: The transformer leakage inductance and the supplementary losses. The goal is to consider the casing effect in the early design stage of power converters.

	Inductance Estimation for Square-Shaped Multilayer Planar Windings By Theofilos PAPADOPOULOS	[View] [Download]
Abstract: In this paper the inductance of square-shaped multilayer planar windings (MLPW) for power applications is investigated. Three well-known equations Wheeler's, Rosa's, and Monomial, which are suitable for single-layer (L1) planar windings, are extended to properly appertain to multilayer architectures. The proposed procedure is verified for two-layer (L2) windings, and the extension to three-layers (L3) or more is discussed, for different values of the geometric parameters. Furthermore, the dependance of thecoupling factor k with respect to the distance between the layers is investigated for L2. Finally, an experimental verification is carried out, for a number of selected windings.

	Loss characterization methodology for soft magnetic nano-crystalline tape materials in coupled inductors By David BOHNE	[View] [Download]
Abstract: In this paper a four-wire magnetic core loss measurement test bench for waveforms typical for two-phase Coupled Inductors is presented. A low permeability nano-crystalline ribbon material is investigated. The advantage of the new test bench is its low measurement time of seconds for multiple operating points at good accuracy. Due to the improvements in preventing disturbances, the measurements are reliable and reproducible.

	Measurement Method for Simple Determination of Sinusoidal Large Signal Losses in Inductive Components By Peter ZACHARIAS	[View] [Download]
Abstract: In this work, a resonance-based losses measurement method is shown suitable for the power dissipation measurement of small and large inductive components under sinusoidal test voltage. In a resonance-based measurement method, the magnetic losses of inductive devices are transformed to the measurement of electrical RMS magnitudes through the device under test. The sinusoidal shape of the test voltage is therefore inherently guaranteed in the measurement procedure.

	Modeling the arrangement of drill holes for orthogonal biasing in controllable inductors for power electronic converters By Jonas PFEIFFER	[View] [Download]
Abstract: Magnetic devices are essential components of power electronic converters. Unfortunately, they usuallyare also the bulkiest and heaviest components in the converter system. Controllable magnetic devicesusing active premagnetization are a promising approach regarding further volume and weightreduction. One method of active premagnetization is orthogonal biasing. To be able to use thismethod, drill holes in the ferrite core material are necessary. Because of the material's fragility andbrittleness, manufacturing ferrite cores is a difficult and expensive process. For this reason, aneffective arrangement of the drill holes is critical.In this paper a basic model of drill hole arrangement based on congruent circle packing is presentedfor circular and square core cross sections. 2D-FEM-simulations and measurement results are madefor comparison and verification. The deviations between calculation and measurement results arediscussed and opportunities for model improvement are given.

	New Analytical Model for Calculating HF-Losses in Litz Wire Regions Located Outside the E/U-CoreWindow of Transformers By Qingchao MENG	[View] [Download]
Abstract: Litz wire is essential for reducing high-frequency losses in medium frequency transformers, which arebuilt often with 'E' or 'U' shaped cores. Many analytical models focus only on the winding section inside the core window, where the winding is completely enclosed by the core. The losses of the winding section outside the core window are not determined separately. This paper compares the losses of both winding sections and provides an accurate and fast loss model for the winding section outside the core window. The error of the model is less than 5\%, which is much smaller than the 1D field model (up to 30\%). Moreover, to compute the total winding losses the model requires about 90 µs, which is comparable to the time consumed by the 1D field model (72 µs on a standard laptop with a 4.8GHz,4-core CPU and a 16GB RAM).

	PCB Layer Optimization of Planar Medium Frequency Transformer for On-Board EV Chargers By Fabian GROON	[View] [Download]
Abstract: Planar medium frequency transformer (MFT) is a promising solution for on-board electric vehicle (EV)chargers, to achieve high power density and high efficiency. The trend towards higher power densities and higher efficiencies exposes a number of limitations on conventional litz wire transformers, especially for increasing the current density. Litz wire current density is limited by the temperature, due to poor thermal management capabilities. PCBs, however, have better thermal management capabilities, which allows for higher current densities. This paper optimizes planar MFT windings focusing on maximizing current density and the simplicity of the implementation. The losses, power density and thermal constraints are investigated and a pareto-front is created based on optimal solutions. High efficiency and power densities are achieved from 2D/3D FEM simulations. A solution within thermal constraints is selected and a prototype is built based on similar ratings. Tests with different current densities are carried out on the prototype and the temperatures are compared. The results verify that planar MFT with high current densities are feasible solutions for high efficiency and high power density MFTs.

	Substitution of Nanocrystalline Toroid by Laminated Ferrite Toroid in the Application of a Common-Mode Choke By Lukas REISSENWEBER	[View] [Download]
Abstract: In this work, it is investigated if a nanocrystalline toroid of a common-mode (CM) choke can be substituted by a laminated ferrite toroid. Small-signal measurement results for the complex impedance, of laminated toroidal cores of material T38 with different diameters and thicknesses at 25 °C and 100 °C are presented. Further the calculated attenuation and the complex permeability are shown. Based on the obtained material data, a CM choke made of laminated ferrite cores is designed and analyzed. The focus is thereby on the comparison with the nanocrystalline CM choke.

	The Variation of Core Loss in High-Frequency Transformers Under Different Load Conditions By Navid RASEKH	[View] [Download]
Abstract: Typically, the core loss of the high-frequency (HF) transformers is considered constant regardless of the load condition on the secondary side. This paper indicates that the various load conditions can affect the core loss in HF transformers due to the variation of winding parasitics elements and subsequently the transformer's excitation voltage and current waveforms, and the field interactions between the primary and secondary windings and between the windings and core. The contribution of this work is demonstrating the core loss variation depending on different load conditions in HF transformers, which is not commonly assessed and considered in previous studies. The captured experimental results are compared with the three-dimensional (3D) finite element analysis (FEA) results conducted in Ansys Maxwell, to provide a better comprehension.