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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Validation of the 'full reconnection model' of the sawtooth instability in KSTAR

In this paper, the central safety factor (q 0 ) during sawtooth oscillation has been measured with a great accuracy with the motional Stark effect (MSE) system on KSTAR and the measured value was However, this measurement alone cannot validate the disputed full and partial reconnection models definitively due to non-trivial off-set error (~0.05). Supplemental experiment of the excited m = 2, m = 3 modes that are extremely sensitive to the background q 0 and core magnetic shear definitively validates the 'full reconnection model'. The radial position of the excited modes right after the crash and time evolution into the 1/1 kink mode before the crash in a sawtoothing plasma suggests that in the MHD quiescent period after the crash and before the crash. Finally, additional measurement of the long lived m = 3, m = 5 modes in a non-sawtoothing discharge (presumably ) further validates the 'full reconnection model'.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Design and Optimization of High-frequency Transformer for Isolated Single-Stage Three-Phase AC/DC Converter using Bidirectional Switches

This paper presents the design and optimization of the high-frequency transformer for an isolated single-stage threephase AC/DC converter enabled by the 4H-SiC BiDirectional Field Effect Transistor (BiDFET). Non-dominated Sorting Genetic Algorithm II (NSGA-II) is used to perform a multiobjective optimization to minimize loss, weight, and volume. A 20 kW, 50 kHz hardware prototype based on the selected optimal point is characterized by a power amplifier. The finite element analysis simulation results are also presented to validate the core magnetic flux density and winding electric field strength. The experimental prototype was tested at 800 Vdc/480 Vrms at 10 kW rated power.

BiDFET, High-frequency transformer, Multiobjective↗
DOE OSTI2020

Thermal Analysis of Wireless Power Transfer Coils for Dynamic Wireless Electric Vehicle Charging

In this paper, safe operating conditions of a wireless power transfer coil were identified and road infrastructure for a dynamic wireless electric vehicle charging system was studied. Magneto-thermal simulations were used to map the power loss directly into the computed fluid dynamics solver. This method allowed the authors to analyze the heating pattern of the enclosed wireless power transfer coil in the road structure, as well as for the vehicle coil. Thermal heating patterns for three types of rectangular coil structures were analyzed. Heating patterns were analyzed for 200 kW coils and different magnetic field densities in the magnetic core.

Wojda, Rafal↗
DOE OSTI2026

Applications of Solid-State Transformers for Electric Power Grid HEMP/GMD Resilience

A high-altitude electromagnetic pulse (HEMP) or geomagnetic disturbance (GMD) can disrupt power grids by inducing low-frequency common-mode (CM) currents. When these currents flow through grounded transformers, they can bias the magnetic core, driving it into saturation and reducing performance or damaging equipment. This work presents a solid-state transformer (SST) to replace vulnerable assets and improve grid resilience. The paper reviews half-cycle saturation in conventional transformers, then describes an SST architecture that neutralizes and redirects CM currents during HEMP/GMD events. A prototype SST is built and validated, demonstrating stable CM-disturbance operation and protection of nearby transformers. Finally, large-scale simulations show how coordinated SST deployment mitigates CM disturbances and strengthens overall grid resilience.

four-leg inverter↗
DOE OSTI2022

Phasing Magnet for CSX-2 Beamline at NSLS-II

A phasing magnet has been developed at National Synchrotron Light Source II (NSLS-II) for the Coherent Soft X-ray Scattering (CSX) beamline. The phasing magnet will be located at the center of the straight section in between two identical and independent variably polarized APPLE-II devices. Based on Permanent Magnet technology, the phasing magnet has been designed to achieve the required electron beam delay to properly adjust the phase matching of these two consecutive EPUs (Elliptically Polarizing Undulators) and ensure a positive interference between the photon beam emitted in each device. Also this paper will describe the mechanical and magnetic design together with the final field measurements and magnetic tuning results. Also, the spectral performance of the two EPUs and the method used to properly set the field strength of the phasing magnet for any given radiation wavelength and polarization mode will be presented as well.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Novel Electrically Tunable Microwave Solenoid Inductor and Compact Phase Shifter Utilizing Permaloy and PZT Thin Films

A Permalloy (Py) thin film enabled tunable 3-D solenoid inductor is designed and fabricated. The special configuration of magnetic core is discussed and by selectively patterning Py thin film, the proposed tunable inductor can work at frequency up to several GHz range. The inductance of the solenoid inductor can be electrically tuned by dc current and the tunability is above 10%. Utilizing the implemented Py enabled tunable solenoid inductor and Lead Zirconate Titanate (PZT) thin film enabled metal-insulator-metal (MIM) capacitor, a compact fully electrically tunable lumped elements phase shifter is achieved. The tunable phase shifter has both inductive and capacitive tunability and the dual tunability significantly improves the tuning range and design flexibility. Moreover, the dual tunability is able to retain the equivalent characteristic impedance of the device in the process of the phase being tuned. Here, the phase of the device can be tuned by fully electrical methods and when dc current and dc voltage are provided, the length normalized phase tunability is up to 210°/cm

36 MATERIALS SCIENCE↗
DOE OSTI2021

Design and Optimization of a 200-kW Medium-Frequency Transformer for Medium-Voltage SiC PV Inverters

This paper presents a design and optimization methodology for a 200-kW medium-frequency transformer (MFT) based on low-loss magnetic core (FINEMET FT-3TL). The proposed optimal design methodology consists of predesign, preliminary design, and optimal design. In the preliminary design, the parallel-concentric winding structure is selected to increase the current carrying capability and reduce the leakage inductance. Based on the parallel-concentric winding concept, a novel cooing and insulation structure with 3-D printed bobbins are proposed. The optimal designed MFT prototype achieves a power density higher than 19.23 kW/L. The electrical insulation system is tested at 12 kV ac peak voltage. In addition, the partial discharge (PD) test is conducted at 7.5 kV ac peak voltage to ensure the PD-free design. The high-frequency bipolar pulsewidth modulation voltage insulation (PD) test is the first time applied in MFT design and test process. Finally, the transformer is applied in a dual-active-bridge (DAB) converter with 200 kW rated power. The peak efficiency of the DAB converter is 99.53%, and the efficiency at 200 kW is 98.85%. The peak efficiency of MFT is 99.844%, and the efficiency at 200 kW is 99.842%.

42 ENGINEERING↗
DOE OSTI2018

Finite element modeling of nanoscale-enabled microinductors for power electronics

Here, this paper focuses on the finite element modeling of toroidal microinductors, employing first-of-its-kind nanocomposite magnetic core material and superparamagnetic iron nanoparticles covalently cross-linked in an epoxy network. Energy loss mechanisms in existing inductor core materials are covered as well as discussions on how this novel core material eliminates them providing a path toward realizing these low form factor devices. Designs for both a 2 μH output and a 500 nH input microinductor are created via the model for a high-performance buck converter. Both modeled inductors have 50 wire turns, less than 1 cm 3 form factors, less than 1 Ω AC resistance, and quality factors, Q’s, of 27 at 1 MHz. In addition, the output microinductor is calculated to have an average output power of 7 W and a power density of 3.9 kW/in 3 by modeling with the 1st generation iron nanocomposite core material.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tapless Voltage Regulating Transformer. Final Report

Voltage regulation is a common practice in power grid operation. The conventional voltage regulation methods have been facing ever increasing challenges as the penetration of renewable generations deepens in the grid. The intermittent nature of the renewable sources may result in sudden rise or drop of power generation, possibly breaking the generation-load balance. A lack of adequate voltage control not only affects the power quality but is detrimental to the system operation with the potential for large economic losses. Most conventional voltage regulation devices rely on mechanical tap changers to impose the regulation in a step-wise manner. Although sufficient for normal operations, the mechanical tap changers can be easily worn out in the challenging situations created by renewables. In this project, a novel technology called tapless voltage regulating transformer (TAREX) was proposed and investigated. It has the potential to excel at addressing the new voltage regulation challenges and replace the conventional regulating transformers. TAREX is based on the concept of the saturable-core reactor (SCR). The voltage of a TAREX can be smoothly and continuously regulated in a reasonable range by using a low rating power electronics based controller. It uses control of the transformer core magnetization to regulate the voltage on the windings, and thus eliminates the mechanical tap changer. This project is to prove the principle of TAREX, understand the voltage regulation mechanism, and preliminarily understand its impacts on the power systems through modeling, prototyping, and testing.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2021

Surface Oxidation Behavior of FeNi-based Metal Amorphous Nanocomposite (MANC) Alloys for High-Speed Motor Applications

New interest in high performance soft magnetic materials (SMMs) have been fueled by the need to lower losses at higher operating frequencies while maintaining high flux density and tunable permeability in electrical motors, transformer, and generator applications. Conventional SMMs like electrical steels and Fe-based metal amorphous nanocomposite (MANC) alloys are dominated by eddy current losses at high frequencies. Recent breakthrough in high-performance FeNi MANC have shown promise in reducing eddy current losses as compared to electrical steels. Their intrinsic adherent native surface oxide layer provides sufficient electrical insulation to reduce interlaminate eddy current losses. However, notwithstanding advances in MANCs, there exists a gap in literature on investigations of the surface oxide layer responsible for significant reduction of interlaminate eddy current losses in magnetic cores. This work presents a detailed characterization of the surface oxide, oxidation behavior, and relationship between oxide thickness and resistivity of a new FeNi MANC alloy (Fe70Ni30)80Nb4B14Si2.

Egbu, James↗
DOE OSTI2024

Rapid-cycling HTS magnet for muon acceleration

A very wide range of operational temperatures of the HTS (YBCO) superconductor makes it suitable for the construction of rapid-cycling magnets required for the muon acceleration. The measured [3] very low power loss of the 0.4 T magnet operating at 300 T/s suggested a realistic possibility of the HTS-based accelerator magnet with much higher magnetic field and ramp rate. The magnet core and the HTS cable designs for the 2 T field in the 30 mm beam gap are presented. The simulation of the HTS cable hysteresis power loss for the 1000 T/s ramp rate is discussed in terms of the operational temperatures and required cryogenic power.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Purpose, Design, and Analysis of the NSTX-U Centerstack Casing Lateral Support Shims

The National Spherical Torus Experiment Upgrade (NSTX-U) centerstack casing surrounds the central magnet core of NSTXU. It provides the inner vacuum boundary of the plasma chamber and supports the radially inboard plasma facing components lining the plasma chamber. The casing is supported like a cantilever, fixed at the lower flange by a connection to the TF Bundle through a G-10 ring. It is flexibly supported at the top by bellows, and insulated shims intended to react the largest part of the inventory of the disruption loads at the upper support, thereby protecting the upper and lower connections from excessive loads. A large part of the qualification of the casing and tiles requires addressing and quantifying disruption loads. These have been estimated based on extensions of the behavior of NSTX during its run period roughly 15 years ago. Structural qualification of the Upgrade used these estimates of the loading as input to calculations to demonstrate adequacy for a “most probable” disruption. The estimates are included in a requirements document to guide conservative design of all components loaded by disruptions. However, the changes made for the upgrade made the extrapolation of disruption behavior uncertain. Disruptions include axisymmetric loading from axisymmetric currents induced in the vessel shells. In addition, more complex currents called Halo currents are a result of plasma poloidal currents impinging on the casing. The halo currents add another layer of uncertain behavior and net lateral loading to the casing. As a result, NSTX-U is equipped with a number of instruments intended to assess the nature and severity of disruptions. The casing shims are required for lateral support of the casing, but these have also been converted to load cells to provide another measure of the magnitude of symmetric and asymmetric loading. Some of the logic in the development of the requirements document are presented. Electromagnetic analysis of axisymmetric and halo loading is described. Global simulations of the casing transient dynamic response, and local analysis and testing of the shim/load cell are included. The shim load cells and other instrumentation will be an important guide in planning NSTX-U experiments beyond its next run period expected in late 2026 or early 2027.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Electrical machine cooling structure

A stator assembly that includes a graphite sheet-like element that has fold(s) so as to define at least two planar sections. The face of one of the planar section abuts a surface of a heat generating location(s) of the stator assembly and a face of another planar section abuts one the tooth or the slot bottom of the stator assembly. Also, a subassembly that includes an electrical machine stator assembly that includes a sheet-like element of a material having high thermal conductivity, wherein a portion of the element abuts the end winding(s) such that the sheet-like element conducts heat to the magnetic core, the stator housing, and/or a winding heat conduction element.

42 ENGINEERING↗
DOE OSTI2020

Magnetically-recoverable catalysts for depolymerization

The present invention relates, in part, to methods for depolymerizing a polymer, in which the method includes use of a magnetic catalyst. The magnetic catalyst can include, e.g., a ore-shell particle, such as a particle having a magnetic core and a shell including a metal-organic framework.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Small bore magnetic measurement system, method for measuring small bore magnets

The invention provides a system for measuring magnets, the system comprising a guide tube removably received by a beam chamber tunnel, wherein said guide tube has a first end terminating at a first end of the tunnel and a second end terminating at a second end of the tunnel; a flexible substrate removably and slidably received by the tube, wherein the flexible substrate has a first end and a second end; a first rotary stage removably attached to the first end of said flexible substrate and a second rotary stage removably attached to the second end of said flexible substrate wherein the first rotary stage and the second rotary stage effects movement of the substrate through the tube; and a Hall probe supported by the flexible substrate. Also provided is a method for measuring magnetic fields, the method comprising extending a measuring probe into a magnetic core while maintaining the probe at ambient temperature and pressure.

Kasa, Matthew T.↗
DOE OSTI2024

System and method for power converter interfacing with multiple series-stacked voltage domains

According to various embodiments, a power conversion circuit is disclosed. The power conversion circuit includes at least one DC bus. The power conversion circuit further includes a plurality of DC-AC conversion units coupled to the DC bus and configured to convert a DC voltage into an AC voltage. The power conversion circuit also includes a multi-winding transformer comprising a magnetic core and a plurality of windings, where each DC-AC conversion unit is coupled to a corresponding winding of the multi-winding transformer.

Chen, Minjie↗
DOE OSTI2024

Magnetic component and method of forming

A component includes a magnetic core having a body formed of a first material, defining a first opening and a second opening thereon. A duct formed of a second material extends at least partially through the body between the first opening and the second opening. The first opening and the second opening are in fluid communication by way of the duct.

Ramabhadran, Ramanujam↗
DOE OSTI2013

DR 21(OH): A HIGHLY FRAGMENTED, MAGNETIZED, TURBULENT DENSE CORE

We present high angular resolution observations of the massive star-forming core DR21(OH) at 880 {mu}m using the Submillimeter Array (SMA). The dense core exhibits an overall velocity gradient in a Keplerian-like pattern, which breaks at the center of the core where SMA 6 and SMA 7 are located. The dust polarization shows a complex magnetic field, compatible with a toroidal configuration. This is in contrast with the large, parsec-scale filament that surrounds the core, where there is a smooth magnetic field. The total magnetic field strengths in the filament and in the core are 0.9 and 2.1 mG, respectively. We found evidence of magnetic field diffusion at the core scales, far beyond the expected value for ambipolar diffusion. It is possible that the diffusion arises from fast magnetic reconnection in the presence of turbulence. The dynamics of the DR 21(OH) core appear to be controlled energetically in equal parts by the magnetic field, magnetohydrodynamic turbulence, and the angular momentum. The effect of the angular momentum (this is a fast rotating core) is probably causing the observed toroidal field configuration. Yet, gravitation overwhelms all the forces, making this a clear supercritical core with a mass-to-flux ratio of {approx_equal} 6 times the critical value. However, simulations show that this is not enough for the high level of fragmentation observed at 1000 AU scales. Thus, rotation and outflow feedback are probably the main causes of the observed fragmentation.

79 ASTRONOMY AND ASTROPHYSICS↗