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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Expanded Equations for Torque and Force on a Cylindrical Permanent Magnet Core in a Large-Gap Magnetic Suspension System

The expanded equations for torque and force on a cylindrical permanent magnet core in a large-gap magnetic suspension system are presented. The core is assumed to be uniformly magnetized, and equations are developed for two orientations of the magnetization vector. One orientation is parallel to the axis of symmetry, and the other is perpendicular to this axis. Fields and gradients produced by suspension system electromagnets are assumed to be calculated at a point in inertial space which coincides with the origin of the core axis system in its initial alignment. Fields at a given point in the core are defined by expanding the fields produced at the origin as a Taylor series. The assumption is made that the fields can be adequately defined by expansion up to second-order terms. Examination of the expanded equations for the case where the magnetization vector is perpendicular to the axis of symmetry reveals that some of the second-order gradient terms provide a method of generating torque about the axis of magnetization and therefore provide the ability to produce six-degree-of-freedom control.

Groom, Nelson J.↗
DOE OSTI2023

Condition monitoring of permanent magnet AC machines for all-electric transportation systems: State of the art

The current state of the art on emerging and efficient techniques for condition monitoring of permanent magnet (PM) alternating-current (AC) machines deployed in electric vehicle (EV) applications is presented. The discussion includes the most common and specific types of faults in PM motors, such as rotor demagnetisation and stator inter-turn faults, respectively. Fault indicators, such as voltage (v s ) and current (i s ) signals and machine signatures based on motor back electromotive force (EMF) (E B ) and magnetic flux (φ), are taken into account as a measuring quantity in diagnosing motor faults. Other signatures, including thermal analysis, acoustic noise, and vibrations, are also illustrated as some of the emerging techniques in estimating the performance of EV motors while under operations. In addition, various fault modelling methods, condition monitoring techniques, and comprehensive approaches applied in diagnosing the effect of machine faults during its incipient stages are illustrated. Since most of the fault diagnostic techniques discussed here include only machine-based quantities as fault indices/indicators, the provided solutions are therefore found to be more reliable and accurate for diagnosing the motor faults. This comprehensive review study is inclusive of the existing fault diagnostic techniques, which are currently employed in industrial and commercial practices, in addition to the new methodologies proposed by the authors. All the given condition monitoring schemes therefore seem significantly vital in estimating the state of health of PM AC machines while under operation in all-electric transportation systems.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2014

Rare-Earth-Free Permanent Magnets for Electrical Vehicle Motors and Wind Turbine Generators: Hexagonal Symmetry Based Materials Systems Mn-Bi and M-type Hexaferrite

The research we conducted focuses on the rare-earth (RE)-free permanent magnet by modeling, simulating, and synthesizing exchange coupled two-phase (hard/soft) RE-free core-shell nano-structured magnet. The RE-free magnets are made of magnetically hard core materials (high anisotropy materials including Mn-Bi-X and M-type hexaferrite) coated by soft shell materials (high magnetization materials including Fe-Co or Co). Therefore, our research helps understand the exchange coupling conditions of the core/shell magnets, interface exchange behavior between core and shell materials, formation mechanism of core/shell structures, stability conditions of core and shell materials, etc.

25 ENERGY STORAGE↗
NASA NTRS2007

Large-Area Permanent-Magnet ECR Plasma Source

A 40-cm-diameter plasma device has been developed as a source of ions for material-processing and ion-thruster applications. Like the device described in the immediately preceding article, this device utilizes electron cyclotron resonance (ECR) excited by microwave power in a magnetic field to generate a plasma in an electrodeless (noncontact) manner and without need for an electrically insulating, microwave-transmissive window at the source. Hence, this device offers the same advantages of electrodeless, windowless design - low contamination and long operational life. The device generates a uniform, high-density plasma capable of sustaining uniform ion-current densities at its exit plane while operating at low pressure [<10(exp -4) torr (less than about 1.3 10(exp -2) Pa)] and input power <200 W at a frequency of 2.45 GHz. Though the prototype model operates at 2.45 GHz, operation at higher frequencies can be achieved by straightforward modification to the input microwave waveguide. Higher frequency operation may be desirable in those applications that require even higher background plasma densities. In the design of this ECR plasma source, there are no cumbersome, power-hungry electromagnets. The magnetic field in this device is generated by a permanent-magnet circuit that is optimized to generate resonance surfaces. The microwave power is injected on the centerline of the device. The resulting discharge plasma jumps into a "high mode" when the input power rises above 150 W. This mode is associated with elevated plasma density and high uniformity. The large area and uniformity of the plasma and the low operating pressure are well suited for such material-processing applications as etching and deposition on large silicon wafers. The high exit-plane ion-current density makes it possible to attain a high rate of etching or deposition. The plasma potential is <3 V low enough that there is little likelihood of sputtering, which, in plasma processing, is undesired because it is associated with erosion and contamination. The electron temperature is low and does not vary appreciably with power.

Foster, John E.↗
DOE OSTI2021

Design of High Power Density 100 kW Surface Permanent Magnet Machine with No Heavy Rare Earth Material Using Current Source Inverter for Traction Application

Surface permanent magnet (SPM) machines are appealing candidates for traction applications because of high power density and high efficiency. Rare-earth magnets deliver high performance but raise concerns about material supply dependability, particularly if they use heavy rare-earth materials. This paper presents the design of a high-performance SPM machine without any heavy rare-earth material that is optimized specifically for a current-source inverter (CSI) traction drive. This machine is designed for a constant-power speed ratio (CPSR) of 3. A genetic algorithm has been performed to achieve a target of 50 kW/L active power density at speeds up to 20,000 rpm. Operation at a peak line-to-line voltage of 800 V can be achieved using 1200 V power devices with a safety margin. The predicted electromagnetic and rotor structural performance characteristics are presented using both analytical and finite element analysis (FEA) results.

(CPSR)↗
DOE OSTI2023

Design and construction of the MUSE permanent magnet stellarator

This paper documents the design and construction of MUSE, the world's first permanent magnet (PM) stellarator and the first quasi-axisymmetric experiment. The purpose of MUSE is to develop and assess a new way of building optimised stellarators that uses simple planar coils PMs. Our PM optimisation algorithm consists of initialising a geometry to pack dipoles densely, running the FAMUS code to minimise surface field error subject to PM constraints and applying discrete jumps to reach a physically realisable solution. FAMUS treats the PM system as a set of ideal point dipoles. From there we construct finite-volume magnet towers to be housed in 3D-printed PM holders. We describe the design of the PM holders, which were validated by laser metrology. We analyse the effects of finite permeability, sensitivity to perturbations and magnetostatic forces. An exact analytic formula for the magnetic field from a finite-volume PM tower is presented to compute PM–PM forces and stress on the PM holder. Stellarator construction is complete and experiments are underway.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Improvement of microwave feeding on a large bore ECRIS with permanent magnets by using coaxial semi-dipole antenna

We are constructing a tandem type electron cyclotron resonance (ECR) ion source (ECRIS). The first stage of this ECRIS has a large-bore with cylindrically comb-shaped permanent magnets. 2.45GHz and 11-13GHz microwaves can be supplied individually and simultaneously to the plasma chamber. For 2.45GHz, a coaxial semi-dipole antenna is used to feed the microwaves. In previous experiments, there were two problems encountered when running the 2.45GHz microwaves. High incident power was necessary to keep ECR discharge at low operating pressure because of high reflected microwave power. The surface of a support insulator between the inner and the outer electrodes of coaxial semi-dipole antenna was easily metalized by sputtering of the metal wall inside the chamber. The purpose of this study was to solve these problems. Performing several simulation experiments supports the hypothesis that the position of the support insulator is significant for microwave power efficiency. The end result was the ability to sustain ECR discharges at extremely low incident microwave power, several tens of watts, by optimized matching of the position and shape of the insulator.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Transverse phase space diagnostics for ionization injection in laser plasma acceleration using permanent magnetic quadrupoles

We report the transverse phase space diagnostics for electron beams generated through ionization injection in a laser-plasma accelerator. Single-shot measurements of both ultimate emittance and Twiss parameters are achieved by means of permanent magnetic quadrupole. Beams with emittance of μm rad level are obtained in a typical ionization injection scheme, and the dependence on nitrogen concentration and charge density is studied experimentally and confirmed by simulations. A key feature of the transverse phase space, matched beams with Twiss parameter α T ≃ 0, is identified according to the measurement. Lastly, numerical simulations that are in qualitative agreement with the experimental results reveal that a sufficient phase mixing induced by an overlong injection length leads to the matched phase space distribution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Jump-Start U.S. Manufacturing of High-Performance Permanent Magnets

Gas atomized feedstock powders for Nd-Fe-B based magnets are more robust and cost effective than the strip-cast sheet currently used as feedstock for milling by the magnet industry. However, gas atomized powder’s crystallinity and grain boundary phases are less ideal than the strip cast flake. We proposed to optimize the atomization process as well as the powder chemistry to address this issue and to eliminate heavy rare earth elements from these magnet alloys. Our goal is to help GKN-Hoeganaes, a US metal powder company, who used to make Nd-Fe-B magnets, to bring back US manufacturing of these high energy density permanent magnets.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Binder-free cold spray deposition of NdFeB permanent magnets

Cold spray deposition is employed to manufacture binder-free Nd 2 Fe 14 B permanent magnets. Millimeter thick deposits can be fabricated in seconds on substrates such as glass or copper. The Nd 2 Fe 14 B particles appear to partially embed in the substrate and interlock with one another, building up a dense layer that is consolidated by subsequent impacts. The impact and subsequent heating of the particles leads to formation of a magnetically soft phase that significantly reduces coercivity, X-ray diffraction identifies it as Fe. Furthermore, this can be mitigated by reducing gas velocity and temperature, leading to a partial retention of magnetic properties.

36 MATERIALS SCIENCE↗
NASA NTRS1999

Three-Dimensional Simulations of Electron Beams Focused by Periodic Permanent Magnets

A fully three-dimensional (3D) model of an electron beam focused by a periodic permanent magnet (PPM) stack has been developed. First, the simulation code MAFIA was used to model a PPM stack using the magnetostatic solver. The exact geometry of the magnetic focusing structure was modeled; thus, no approximations were made regarding the off-axis fields. The fields from the static solver were loaded into the 3D particle-in-cell (PIC) solver of MAFIA where fully 3D behavior of the beam was simulated in the magnetic focusing field. The PIC solver computes the time-integration of electromagnetic fields simultaneously with the time integration of the equations of motion of charged particles that move under the influence of those fields. Fields caused by those moving charges are also taken into account; thus, effects like space charge and magnetic forces between particles are fully simulated. The electron beam is simulated by a number of macro-particles. These macro-particles represent a given charge Q amounting to that of several million electrons in order to conserve computational time and memory. Particle motion is unrestricted, so particle trajectories can cross paths and move in three dimensions under the influence of 3D electric and magnetic fields. Correspondingly, there is no limit on the initial current density distribution of the electron beam, nor its density distribution at any time during the simulation. Simulation results including beam current density, percent ripple and percent transmission will be presented, and the effects current, magnetic focusing strength and thermal velocities have on beam behavior will be demonstrated using 3D movies showing the evolution of beam characteristics in time and space. Unlike typical beam optics models, this 3D model allows simulation of asymmetric designs such as non- circularly symmetric electrostatic or magnetic focusing as well as the inclusion of input/output couplers.

Kory, Carol L.↗
DOE OSTI2017

A Comprehensive Review of Permanent Magnet Transverse Flux Machines for Direct Drive Applications

The use of direct drive machines in renewable and industrial applications are increasing at a rapid rate. Transverse flux machines (TFM) are ideally suited for direct drive applications due to their high torque density. In this paper, a comprehensive review of the permanent magnet (PM) TFMs for direct drive applications is presented. The paper introduces TFMs and their operating principle and then reviews the different type of TFMs proposed in the literature. The TFMs are categorized according to the number of stator sides, types of stator cores and magnet arrangement in the rotor. The review covers different design topologies, materials used for manufacturing, structural and thermal analysis, modeling and design optimization and cogging torque minimization in TFMs. The paper also reviews various applications and comparisons for TFMs that have been presented in the literature.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

Laminated Permanent Magnets Enable Compact Magnetic Components in Current-Source Converters

Magnetic components have become one of the primary barriers to high power density converters, especially to current-source converters (CSCs). In CSCs, the inductors/transformers have a predominantly dc flux to store energy, which can be offset by standard permanent magnets (PMs). However, eddy currents in standard PMs induce significant losses and thermal stress for medium-frequency applications. This article proposes using laminated PMs to offset the dc flux while reducing eddy currents, leading to significant reductions in the size, cost, and losses of inductors/transformers. Furthermore, the laminated PMs’ optimal location, orientation, and distribution are investigated to generalize this approach for maximum benefits. Here, three-dimensional finite-element analysis simulation and hardware experiments are presented to validate the effectiveness of the proposed approach in a medium-frequency transformer (MFT) for CSCs. Compared with standard PMs, the proposed use of laminated PMs reduces aggregate core-plus-PM losses by 85% in experiments, and thus, relaxes the MFT thermal design. Finally, the proposed approach is experimentally validated in a 40 kVA flyback-type MFT for a soft-switching solid-state transformer. Compared to the traditional design without any PMs, the proposed design increases the saturation current by 46% while inducing only 5% more losses, leading to significant savings in magnetics cost and size.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Permanent magnets for the return loop of the Cornell-Brookhaven energy recovery linac test accelerator

214 neodymium permanent magnets have been manufactured for the return loop of the CBETA multi-turn ERL at Cornell University. There are 5 types of quadrupole and combined-function gradient magnets using a variant of the circular Halbach design. These are made out of NdFeB material and glued into an aluminium housing with water channels for temperature stabilisation. The NdFeB wedges and magnet construction were done by outside companies, while the final “tuning” using inserts containing 64 iron rods per magnet was done at BNL over a period of about 6 months. Average relative field errors of 2.2×10 -4 were achieved on the beam region. The magnet strengths vary by type but are of order 10 T/m for quadrupole component and up to 0.3 T for the dipole. This paper reports on the field quality and timeline achieved in this production process

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Effect of Ce{sup 3+} Ion on Structural and Hyperfine Interaction Studies of Co{sub 0.5}Ni{sub 0.5}Fe{sub 2−x}Ce{sub x}O{sub 4} Ferrites: Useful for Permanent Magnet Applications

Nanoparticles of Co{sub 0.5}Ni{sub 0.5}Fe{sub 2−x}Ce{sub x}O{sub 4} (where x = 0.0, 0.01, 0.015 and 0.02) ferrites are prepared by the modified solution combustion method using a mixture of fuels and are characterized to understand their structural, microstructural and magnetic properties. The X-ray diffraction is used to confirm the formation of a single-phase cubic spinel structure. The average crystallite sizes are calculated using the Scherrer formula and are found to be less than 50 nm. The microstructural features are obtained by the scanning electron microscopy, and the compositional analysis is done by using the energy-dispersive spectroscopy. The transmission electron microscopy (TEM) investigations show that the synthesized ferrites are made up of very fine spherical nanoparticles. The influence of a rare-earth element (Ce{sup 3+}) on the magnetic properties of the samples was studied using the Mössbauer spectroscopy. The Mössbauer spectroscopy reveals the formation of broadened Zeeman lines and quadrupole-split lines and the presence of the Fe{sup 3+} charge state at B sites in the samples. The quadrupole splitting shows that the orientation of the magnetic hyperfine field with respect to the principle axes of the electric field gradient was random. The magnetic hyperfine field values indicate that the A sites have more A-O-B superexchange interactions than the B sites. The coexistence of magnetic sextet and a doublet component on the room-temperature spectra suggests superparamagnetic properties of the nanoparticles. The low-temperature (15 K) Mössbauer spectroscopy explores the paramagnetic relaxation in the nanoparticles. The area under the sextet refers to Fe{sup 3+} concentrations in the tetrahedral and octahedral sites of the ferrite. This study confirms that the Ce{sup 3+} substitution of Fe{sup 3+} only for octahedron sites causes the decrease in Fe-O-Fe arrangement. The effect of Ce{sup 3+} doping on the magnetic properties of Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} is examined from the vibrating sample magnetometry (VSM) spectra. Saturation magnetization values are decreased initially and then increased, as result of Ce{sup 3+} doping. This can be explained by Neel’s two-sub-lattice model. Further, the value of coercivity is found to be increasing with increasing Ce{sup 3+} concentration. The obtained results of M-H loop with improved coercivity (from 851 to 1039 Oe) by Ce{sup 3+} doping of Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} demonstrate the usefulness for permanent magnet applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Additive Manufacturing of Near-net Shaped Permanent Magnets

The technical objective of this technical collaboration phase I proposal is to fabricate near net-shaped permanent magnets using alloy powders utilizing direct metal deposition technologies at the ORNL MDF. Direct Manufacturing using the POM laser system was used to consolidate Nd 2 Fe 14 B (NdFeB) magnet powders into near net-shape parts efficiently and with virtually no wasted material as part of the feasibility study. We fabricated builds based on spherical NdFeB magnet particles. The results show that despite the ability to fabricate highly reactive materials in the laser deposition process, the magnetic coercivity and remanence of the NdFeB hard magnets is significantly reduced. X-ray powder diffraction in conjunction with electron microscopy showed that the material experienced a primary Nd 2 Fe 17 B x solidification due to the undercooling effect (>60K). Consequently the presence of alpha iron phase resulted in deterioration of the build properties. Further optimization of the processing parameters is needed to maintain the Nd 2 Fe 14 B phase during fabrication.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Development of Tunable, Precision Permanent Magnet Phase Shifter for X-Ray FEL

In an X-ray free-electron laser (XFEL), a high quality relativistic electron beam from a linear accelerator traverses an array of undulator magnets to generate a high power X-ray beam by allowing the FEL to reach saturation. In many XFELs, phase shifters haven’t been commonly used or included in their designs. The importance of the phase shifter was recognized only recently. A phase shifter can be constructed using either an electromagnet (EM) or a permanent magnet (PM). EM phase shifters are heavy, complex to operate, and take more valuable longitudinal space between the undulators. Compared to EMs, the PMs have several outstanding advantages, including compactness, lighter weights, simple operation, and low maintenance. This project has developed an innovative design of fixed-gap, tunable PM-based compact phase shifter for the XFEL. While keeping the poles and gap fixed, the new design incorporates proven features from the prior work, along with novel field tuning methods, which allow the field strength to be adjusted within a reasonably large range to achieve the desired range of the phase delay control. The PM design without electric currents and power electronics associated with EMs improves reliability by reducing the number of possible points of failure and lowers the operation cost. The compactness makes it possible to use PM phase shifters in the existing XFELs with small gaps between adjacent undulators, as well as in the new XFELs without significantly increasing the FEL length. In Phase I we have accomplished the followings; 1) determined the optimum physics parameters for both weak and strong phase shifters; 2) conducted magnetic design with concrete magnetic and geometrical parameters of actual produced PM materials; 3) provided solutions to achieve precision fine tuning of the magnetic fields with unique methods; 4) elaborated a design based upon ease of manufacturing and cost analysis; and 5) produced rare-earth PM materials, which will be used for prototyping in Phase II. The phase I results provide a foundation for the research and development in the Phase II project, which will aim at building two full-size PM phase shifters and testing at SLAC National Accelerator Laboratory. This project will significantly provide the potential to bring a paradigm change in accelerator technology, replacing conventional electromagnets for many existing accelerator applications and allowing the development of new applications in completely new areas. For example, the PM FEL phase shifters can help significantly improve coherence and power of an XFEL. The proposed use of PM phase shifters will also bring significant cost savings to the construction, operation and maintenance of FEL facilities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Voltage Regulation Using a Permanent Magnet Synchronous Generator with a Series Compensator: Preprint

A wind power plant (WPP) is often operated at unity power factor, and the utility host where the WPP connects prefers to regulate the voltage. Although this may not be an issue in a stiff grid, the connection to a weak grid can be a problematic. This paper explores the advantages of having voltage regulation capability via reactive power control. Another issue in wind power generation is that not all turbines are able to control their reactive power due to technical reasons or contractual obligations. A synchronous condenser (SC) using a permanent magnet synchronous generator (PMSG) is proposed to provide necessary reactive power for regulating voltage at a weak grid connection. A PMSG has the advantage of higher efficiency and reliability. Because of its lack of a field winding, a PMSG is typically controlled by a full-power converter, which can be costly. In the proposed system, the reactive power of the SC is controlled by a serially connected compensator operating in a closed-loop configuration. The compensator also damps the PMSG’s tendency to oscillate. The compensator’s VA rating is only a fraction of the rating of the SC and the PMSG. In this initial investigation, the proposed scheme is shown to be effective by computer simulations.

17 WIND ENERGY↗