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Results for “ALTERNATING CURRENT GENERATOR”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Optical properties of the atmospheric pressure helium plasma jet generated by alternative current (a.c.) power supply

In this work, an atmospheric pressure plasma jet (APPJ) was produced to generate cold flowing post-discharge plasma of pure helium gas. The main aim of this study was to generate cold flowing APPJ of pure helium gas and to determine how their optical emission spectrum change influences varying different flow rates. Lengths of early, middle, and late post-discharge plasma (jet) regions and their fluctuations were determined, respectively. Then, ignition condition dependence of the post-discharge plasma for flow rate was specified at a constant voltage. Spectroscopic studies of an atmospheric pressure plasma jet of helium were presented via analyzing OH, N{sub 2}, N{sub 2}{sup +}, oxygen, and helium intensities for various flow rates.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Alternating Current Photovoltaic Effect

It is well known that the photovoltaic effect produces a direct current (DC) under solar illumination owing to the directional separation of light-excited charge carriers at the p–n junction, with holes flowing to the p-side and electrons flowing to the n-side. In this study, we found that apart from the DC generated by the conventional p–n photovoltaic effect, there is another new type of photovoltaic effect that generates alternating current (AC) in the nonequilibrium states when the illumination light periodically shines at the junction/interface of materials. The peak current of AC at high switching frequency can be much higher than that from DC. The AC cannot be explained by the established mechanisms for conventional photovoltaics; instead, it is suggested to be a result of the relative shift and realignment between the quasi-Fermi levels of the semiconductors adjacent to the junction/interface under the nonequilibrium conditions, which results in electron flow in the external circuit back and forth to balance the potential difference between two electrodes. By virtue of this effect, the device can work as a high-performance broadband photodetector with extremely high sensitivity under zero bias; it can also work as a remote power source providing extra power output in addition to the conventional photovoltaic effect.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Radio-frequency discharge in a molecular gas flow at a frequency of 1.76 MHz

Results are presented from experiments on the initiation of a homogeneous stable capacitive RF discharge at a frequency of 1.76 MHz in a high-speed molecular gas flow between metal electrodes at a pressure of 5 Torr or dielectric-coated electrodes at a pressure of up to 50 Torr. A mechanism of the current closure in the electrode sheaths related to the primary photoelectric current generated alternately from different electrodes is proposed. The average electron energy increases via second-kind (superelastic) collisions, and fast electrons with energies corresponding to the amplitude value of the RF voltage appear in the electron energy spectrum. As a result, primary emission arises due to the excitation of emitting states from metastable molecular levels. The primary photoelectric current initiates electron avalanches in the electrode sheaths due to secondary photoelectron emission. According to calculations, the current−voltage characteristic of the sheath in this type of discharge is ascending and the field strengths in the electrode sheath and positive column are lower than those in a self-sustained dc discharge. The calculated results are compared with the experimental data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Fully Solid State Thermomagnetoelectric Generator: Cycle Model and Proof-of-Concept Results

Electricity generation from heat in small-scale systems is currently limited to internal and external combustion heat engine generators or thermoelectric elements. This study introduces a new concept for a solid state thermomagnetoelectric power generator and presents a theoretical study of the cycle. While magnetocaloric materials (MCMs) are common in cryogenic cooling applications, in this work the magnetocaloric thermodynamic heat pump cycle is reversed to generate electricity from low-grade heat. A critical distinguishing feature of the approach is that there are no moving parts: the system directly converts heat into electricity with no moving magnet or regenerators (similar to thermoelectric elements). By periodic heating and cooling of the MCM, the magnetic field inside the copper coil changes in time, generating alternating current electricity. This fully solid state system can directly convert heat into electricity and is modeled at 54% of Carnot efficiency. Compared with state-of-the-art thermoelectric elements, the proposed technology has 3-4 times higher heat-to-electricity conversion efficiency at the same driving temperature difference.

Zhang, Mingkan↗
DOE OSTI2017

Implications of the 2015 and 2016 Ukrainian electric grid cyber attacks to nuclear power plants - 113

Nuclear plants can be vulnerable from electric grid cyber attacks. In December 2015 and December 2016, cyber attackers attacked the Ukrainian electric grid and 'turned off the lights' by opening substation protective relays. The 2015 cyber attacks targeted electric distribution systems and the 2016 cyber attacks targeted electric transmission systems. In order to accomplish the attacks, the cyber attackers compromised field control system devices to inject malware and then open protective relays in substations. There are some very significant implications to nuclear plant operations from hacking the substations and switchyard breakers that serve nuclear plants. The nuclear plant operational concerns are compromising protective relays to prevent relay protection that would result in damage to large electric equipment; spurious actuation of protective relays causing loss-of-offsite power (LOOP) conditions; and the closing and then reopening of protective relays out-of-phase with the grid causing the Aurora vulnerability damaging generators, Alternating Current (AC) motors, and transformers. All of these protective relay conditions have already occurred in actual or test conditions. The common thread to these scenarios are that switchyard and substation protective relays are out-of-scope of existing nuclear cyber security regulations yet, when compromised, have demonstrated impacts to nuclear plant operations and challenged safety systems. There is one other issue about an attack originating from a protective relay. That is, it would be irrelevant whether the nuclear plant system that would be impacted would have analog or digital instrumentation and control (I and C) systems because the impact is upstream of the I and C. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1981

Electrical power generating system

An alternating current power generation system adopted to inject power in an already powered power line is discussed. The power generating system solves to adjustably coup an induction motor, as a generator, to an ac power line wherein the motor and power line are connected through a triac. The triac is regulated to normally turn on at a relatively late point in each half cycle of its operation, whereby at less than operating speed, and thus when the induction motor functions as a motor rather than as a generator, power consumption from the line is substantially reduced. The principal application will be for windmill powered generation.

Nola, F. J.↗
DOE OSTI2015

System and method of adjusting the equilibrium temperature of an inductively-heated susceptor

A system for inductively heating a workpiece may include an induction coil, at least one susceptor face sheet, and a current controller coupled. The induction coil may be configured to conduct an alternating current and generate a magnetic field in response to the alternating current. The susceptor face sheet may be configured to have a workpiece positioned therewith. The susceptor face sheet may be formed of a ferromagnetic alloy having a Curie temperature and being inductively heatable to an equilibrium temperature approaching the Curie temperature in response to the magnetic field. The current controller may be coupled to the induction coil and may be configured to adjust the alternating current in a manner causing a change in at least one heating parameter of the susceptor face sheet.

42 ENGINEERING↗
DOE OSTI2019

System for adjusting the equilibrium temperature of an inductively-heated susceptor

A system for inductively heating a workpiece may include an induction coil, at least one susceptor face sheet, and a current controller coupled. The induction coil may be configured to conduct an alternating current and generate a magnetic field in response to the alternating current. The susceptor face sheet may be configured to have a workpiece positioned therewith. The susceptor face sheet may be formed of a ferromagnetic alloy having a Curie temperature and being inductively heatable to an equilibrium temperature approaching the Curie temperature in response to the magnetic field. The current controller may be coupled to the induction coil and may be configured to adjust the alternating current in a manner causing a change in at least one heating parameter of the susceptor face sheet.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Elviz – exploration of metagenome assemblies with an interactive visualization tool

Metagenomics, the sequencing of DNA collected from an entire microbial community, enables the study of natural microbial consortia in their native habitats. Metagenomics studies produce huge volumes of data, including both the sequences themselves and metadata describing their abundance, assembly, predicted functional characteristics and environmental parameters. The ability to explore these data visually is critically important to meaningful biological interpretation. Current genomics applications cannot effectively integrate sequence data, assembly metadata, and annotation to support both genome and community-level inquiry. Elviz (Environmental Laboratory Visualization) is an interactive web-based tool for the visual exploration of assembled metagenomes and their complex metadata. Elviz allows scientists to navigate metagenome assemblies across multiple dimensions and scales, plotting parameters such as GC content, relative abundance, phylogenetic affiliation and assembled contig length. Furthermore Elviz enables interactive exploration using real-time plot navigation, search, filters, axis selection, and the ability to drill from a whole-community profile down to individual gene annotations. Thus scientists engage in a rapid feedback loop of visual pattern identification, hypothesis generation, and hypothesis testing. Compared to the current alternative of generating a succession of static figures, Elviz can greatly accelerate the speed of metagenome analysis. Elviz can be used to explore both user-submitted datasets and numerous metagenome studies publicly available at the Joint Genome Institute (JGI). Elviz is freely available at http://genome.jgi.doe.gov/viz and runs on most current web-browsers.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Direct current power delivery system and method

A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1980

Solar cell system having alternating current output

A monolithic multijunction solar cell was modified by fabricating an integrated circuit inverter on the back of the cell to produce a device capable of generating an alternating current output. In another embodiment, integrated curcuit power conditioning electronics was incorporated in a module containing a solar cell power supply.

Evans, J. C., Jr.↗
DOE OSTI2014

Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.

79 ASTRONOMY AND ASTROPHYSICS↗