Power Electronics

T16-Magnetic Components, Design and Characterization Track: Devices and Components

The "T16-Magnetic Components, Design and Characterization Track: Devices and Components" technical session will be Wednesday, March 19 from 2 p.m. to 4:30 p.m:

Title: Method for Introducing Bias Magnetization in Ungaped Cores: “The Saturation-Gap”
Abstract: Inductors intended for DC applications present their working point on the load line restricted to the first quadrant and their energy storage capability on the third quadrant remains unused. A known technique for equilibrating the inherent asymmetry of DC inductors consists on introducing a negative bias flux by means of permanent magnets. This technique can help to draw upon the storage capability on the third quadrant and thus reduce the size of a given DC inductor. This paper analyzes the pros and cons of different permanent magnet inductors configurations found in the scientific literature. It will also present a new biasing configuration termed: The Saturation-Gap and test it experimentally.
Andres Revilla Aguilar, Aalborg University
Stig Munk-Nielsen, Aalborg University

Title: Gapped Transformer Design Methodology and Implementation for LLC Resonant Converters
Abstract: In the LLC resonant converter, the air gap is generally positioned in the core of the transformer for proper magnetizing inductance. Traditional transformer design methods assume infinite permeability of the core and no energy stored in the core. The improved design methodology for the gapped transformer is proposed with the optimum relative permeability and gap selection to meet the temperature rise and the magnetizing inductance requirements. The magnetizing current influences the magnetic flux in the core leading to the core saturation and core loss, while the resonant current contributes to the winding loss. The transformer design for a 200 W, 90 kHz LLC resonant converter is presented and experimental results validate the proposed methodology.
Jun Zhang, National University of Ireland, Galway
W. G. Hurley, National University of Ireland, Galway
W. H. Wolfle, Convertec Ltd.

Title: Design and Implementation of PCB Inductors with Litz-Wire Structure for Conventional-Size Large-Signal Domestic Induction Heating Applications
Abstract: Induction cookers are usually designed to deliver up to several kilowatts per burner, working above 20 kHz. These appliances are arranged by means of planar-spiral inductors, made of conventional multi-stranded litz-wire, whose size can reach up to tens of centimeters. In this work, a PCB implementation of such inductors is proposed in order to replace the conventional windings, considering the induction efficiency as the figure of merit. With this purpose, a finite-element analysis FEA-aided design and a planar litz-wire structure has been used for implementing the windings. The design was validated by means of experimental measurements on a prototype.
Ignacio Lope, Universidad de Zaragoza
Claudio Carretero, Universidad de Zaragoza
Jesus Acero, Universidad de Zaragoza
Rafael Alonso, Universidad de Zaragoza
José Miguel Burdío, Universidad de Zaragoza

Title: Realistic Litz Wire Characterization Using Fast Numerical Simulations
Abstract: The losses of realistic litz wires are characterized while explicitly accounting for their construction, using a procedure that computes the current-driven and magnetic-field–driven copper losses using fast numerical simulations. We present a case study that examines loss variation in one- and two-level litz wires as a function of twisting pitch, over a wide range of values and in small increments. Experimental confirmation is presented for predictions made by numerical simulations. Results confirm the capability and efficiency of numerical methods to provide valuable insights into the realistic construction of litz wire.
Richard Zhang, Massachusetts Institute of Technology
Jacob White, Massachusetts Institute of Technology
John Kassakian, Massachusetts Institute of Technology
Charles Sullivan, Dartmouth College

Title: New Core Loss Measurement Method with Partial Cancellation Concept
Abstract: As an essential part in a power converter, the magnetic cores and their design play an important role in achieving high efficiency and high power density. Accurate measurement of the core loss is important to their optimization. To improve the measurement accuracy, previous methods were proposed to cancel the reactive voltage of the testing core by a cancellation capacitor or inductor. However, the value of the cancellation component is critical, and a small variation may induce a big measurement error, so extra effort is required to fine-tune the cancellation component value. This paper presents a new measurement method with partial cancellation concept that enables accurate core loss measurement at high frequency without requirement to fine-tune the cancellation component value.
Dongbin Hou, Virginia Polytechnic Institute and State University
Mingkai Mu, Virginia Polytechnic Institute and State University
Fred C. Lee, Virginia Polytechnic Institute and State University
Qiang Li, Virginia Polytechnic Institute and State University

Title: Wire Bonded MEMS-Scale on-Chip Transformers
Abstract: We present a novel wafer-level fabrication method of 3D solenoidal microtransformers using an automatic wire-bonder. Automatic wire bonders allow to precisely shape 25 ?m diameter wire around prefabricated yokes or magnetic cores within seconds. Former reports of wire bonded micro coils treated individual solenoids with low mutual inductance, whereas in this study transformers with strongly coupled micro solenoids are presented. The process is fully compatible with standard microelectronic manufacturing and, therefore, enables the direct integration of transformers into a given electronic circuit. Two different prototypes are presented here. A non-magnetic core transformer with power efficiency of 67% and resonance frequency of 312 MHz and a magnetic core transformer with more than 1 ?H inductance and 74% power efficiency at 29 MHz. Both prototype’s feasibility with view to power conversion in miniaturized circuits are evaluated.
Ali Moazenzadeh, Albert-Ludwigs-Universität Freiburg
Nils Spengler, Albert-Ludwigs-Universität Freiburg
Vlad Badilita, Albert-Ludwigs-Universität Freiburg
Jan G. Korvink, Albert-Ludwigs-Universität Freiburg
Ulrike Wallrabe, Albert-Ludwigs-Universität Freiburg

Title: A New Model for Designing Multi-Hole Multi-Permeability Nonlinear LTCC Inductors
Abstract: A new model for designing multi-hole multi-permeability nonlinear inductors. The proposed model significantly simplified the complicated electromagnetic analysis of the nonlinear inductors by breaking down the inductor into three basic units. The calculation results of the proposed model highly agree with the simulation results. By using a nonlinear inductor, the efficiency of a DC/DC converter can be improved.
Laili Wang, Queen’s University
Zhiyuan Hu, Queen’s University
Yajie Qiu, Queen’s University
Hongliang Wang, Queen’s University
Yan-Fei Liu, Queen’s University

Title: Silicon-Embedded Toroidal Inductors with Magnetic Cores: Design Methodology and Experimental Validation
Abstract: An approach to the ultimate integration and miniaturization of MEMS-based 3-D magnetic components involves embedding the volume of the magnetic structures within the volume of the silicon wafer itself, exploiting lithographically-patterned windings to create current paths, and utilizing embedded magnetic cores within the limited footprint of these components to boost the magnetic performance. However, this embedding approach imposes volumetric and microfabrication constraints that require an unusual magnetic component optimization methodology compared to wire-wound inductors and PCB inductors. A design methodology encompassing these constraints is therefore needed. For a targeted inductance value within a given footprint, our design methodology addresses an inductor with a maximized quality factor based on the trade-offs between winding loss and core loss. To illustrate this methodology, silicon-embedded inductors with drop-in iron powder cores are designed and fabricated, where a quality factor of 24 is achieved at 30 MHz.
Xuehong Yu, Georgia Institute of Technology
Jungkwun Kim, Georgia Institute of Technology
Florian Herrault, Georgia Institute of Technology
Mark Allen, Georgia Institute of Technology

Title: Optimization of Windings in PFC Boosts and PWM Inverters to Maximize Converter Efficiency
Abstract: Optimization of the inductors and transformers in switching power converters is presented in the paper. Inductive components of different core ” coil geometries and wire technologies are taken into account. Rigorous analytical modeling was applied to achieve minimization of the losses, using homogenization of the stack of wires in equivalent conductive layers of the coils. The resolution has been carried out for many different shapes of conductors. Comparative study by complementary FEM approach shows and explains varied physical phenomena as e-mag interactions between the turns. Focus is done on skin and proximity effects and possible solutions to reduce their harmful influence on converter efficiency decreasing. Several new technologies by improved winding geometries and novel coil structures are discussed. The necessity of the optimization process to find the best industrial solution has been proven.
Timothe Delaforge, Schneider Electric
Herve Chazal, Université de Grenoble / G2Elab
Robert Pasterczyk, Schneider Electric

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