@article{beddingfield_leary_noebe_nations_bowman_bhattacharya_2022, title={Calculation of Transformer Leakage Inductance by Simplified Flux Path Geometries}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947606}, abstractNote={Series inductance is a critical energy storage element in isolated power converters. Many have explored methods of estimating the total leakage inductance of transformers as an integrated series inductance without external inductors. However, this poses challenges with medium frequency converters and magnetic ribbon-based cores, e.g., metal amorphous nanocrystalline. The material's relatively high conductivity allows eddy currents to develop when magnetic flux intersects wide surfaces. These eddy currents result in significant additional losses that increase with increasing power flow. This paper presents a simplified and accurate method of estimating leakage flux while identifying separate leakage flux paths that correlate with the magnetic material surfaces. This enables an understanding the proportion of leakage flux that will contribute to extra losses. The methods presented are applicable to both leakage and fringing (around heterogeneous material interfaces) fluxes. This paper includes detailed FEA studies and 3D flux vector measurements matching the presented analytical models.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Beddingfield, Richard B. and Leary, Alex M. and Noebe, Ronald and Nations, Mark and Bowman, Randy and Bhattacharya, Subhashish}, year={2022} }
 @article{nations_beddingifield_bhattacharya_2022, title={Design Considerations and Performance Evaluation of 50kW, 40kHz DAB Converter with Coaxial Winding Transformer}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947822}, abstractNote={Design of power electronic systems is often done with top-down specifications for each subsystem, which leaves system-level tradeoffs between power electronics, magnetics, control strategies invisible to the design process. If all parts of the system are well modeled, it is possible to perform optimal design on the entire system in a single step, taking into account all modeled trade-offs and cross coupling between components. A 50kW dual active bridge converter utilizing a coaxial winding transformer is used to demonstrate this as a whole system co-design. Detailed modeling of coaxial transformer capacitance, winding design, and thermal performance is developed. The NSGA-II genetic algorithm-based optimization implementation is utilized with an extension to the simulated binary crossover (SBX) operator to handle bounded design variables. Co-design is performed, results are discussed, and a design with 40kHz switching frequency is selected. The converter is built utilizing Finemet nanocrystalline magnetic cores and improvements on CWT tubular winding construction are presented. The converter is tested and shown to operate above 98% efficiency over a wide load range. Converter thermal performance is verified with the proposed model.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Nations, Mark and Beddingifield, Richard B. and Bhattacharya, Subhashish}, year={2022} }
 @article{simizu_byerly_schneider_kim_nations_narasimhan_beddingfield_bhattachayara_mchenry_2021, title={Flux Switching Permanent Magnet Motor with Metal Amorphous Nanocomposite Soft Magnetic Material and Rare Earth Free Permanent Magnets}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE47101.2021.9594971}, abstractNote={The power losses in high power-density motors due to high rotational speed and/or high pole counts may be reduced adopting metal amorphous nanocomposites (MANCs) featuring low power loss and a relatively high flux density ($\sim$1.3 T). We recently proposed a flux switching permanent magnet (FSPM) motor with a rating of 2.5 kW at 1400 Hz electrical speed that incorporates low loss (<3W/kg at 1 kHz) FeNi-based MANC with projected iron loss of about 5 W. The motor design allows use of rare earth-free permanent magnets. To incorporate MANCs, an axial flux motor with rotor and stator cores made from a wound ribbon has been developed. We performed 3-d FEA to optimize the design and built and tested a prototype showing that low loss MANC material can be used for motor applications with high magnetic switching frequency.}, journal={2021 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Simizu, Satoru and Byerly, Kevin and Schneider, Kyle and Kim, Heonyoung and Nations, Mark and Narasimhan, Sneha and Beddingfield, Richard and Bhattachayara, Subhashish and McHenry, Michael E.}, year={2021}, pages={3866–3872} }