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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Minority-carrier mobility anomalies in low-resistivity silicon solar cells

Measurement of the minority-carrier mobility in the base region of a high-voltage metal-insulator-N-P solar cell (Green et al., 1984), as well as in other 0.1-ohm cm cells, provides direct proof that the high voltages measured for that cell are due not only to improved emitter characteristics but to an improved base region as well. The base characteristics are shown to be quite sensitive to the effects of diffusion-induced lattice stress originating in the emitter. The implications of these findings for the fabrication of high-efficiency cells are discussed.

Weizer, V. G.↗
NASA NTRS1991

Design of a fast computer-based partial discharge diagnostic system

Partial discharges cause progressive deterioration of insulating materials working in high voltage conditions and may lead ultimately to insulator failure. Experimental findings indicate that deterioration increases with the number of discharges and is consequently proportional to the magnitude and frequency of the applied voltage. In order to obtain a better understanding of the mechanisms of deterioration produced by partial discharges, instrumentation capable of individual pulse resolution is required. A new computer-based partial discharge detection system was designed and constructed to conduct long duration tests on sample capacitors. This system is capable of recording large number of pulses without dead time and producing valuable information related to amplitude, polarity, and charge content of the discharges. The operation of the system is automatic and no human supervision is required during the testing stage. Ceramic capacitors were tested at high voltage in long duration tests. The obtained results indicated that the charge content of partial discharges shift towards high levels of charge as the level of deterioration in the capacitor increases.

Oliva, Jose R.↗
NASA NTRS2017

Multilayered Functional Insulation System (MFIS) for AC Power Transmission in High Voltage Hybrid Electrical Propulsion

High voltage hybrid electric propulsion systems are now pushing new technology development efforts for air transportation. A key challenge in hybrid electric aircraft is safe high voltage distribution and transmission of megawatts of power (>20 MW). For the past two years, a multidisciplinary materials research team at NASA Glenn Research Center has investigated the feasibility of distributing high voltage power on future hybrid electric aircraft. This presentation describes the team's approach to addressing this challenge, significant technical findings, and next steps in GRC's materials research effort for MW power distribution on aircraft.

high voltage power transmission↗
DOE OSTI2022

A Flux Balancing Strategy for 10-kV SiC-Based Dual-Active-Bridge Converter

The transformer flux unbalance in dual-active-bridge (DAB) converters is a critical issue due to the electrical parameter and modulation mismatch, and load or control transients. Compared to low voltage DAB converters, the unbalance problem in medium voltage DAB converters may cause more severe problem, and become more difficult to deal with, because of the high operating voltage and insulation requirement. In this paper, a flux balancing strategy for a medium voltage (MV) DAB converter is proposed, including the transformer design with ferrite gap, current harmonic-based unbalance detection, as well as the flux balancing control scheme. With the proposed ferrite gap, nonlinear magnetizing current and its modeling are induced. Then, by analyzing the current harmonics, the flux unbalance level can be detected, and hence controlled. Test results have verified the proposed method in a MV DAB converter.

Gao, Zihan↗
NASA NTRS2017

Linear Transformer Drivers for Z-pinch Based Propulsion

The MSFC/UAH team has been developing of a novel power management and distribution system called a Linear Transformer Driver (LTD). LTD's hold the promise of dramatically reducing the required mass to drive a z-pinch by replacing the capacitor banks which constitute half the mass of the entire system. The MSFC?UAH tea, is developing this technology in hope of integrating it with the Pulsed Fission Fusion (PuFF) propulsion concept. High-Voltage pulsed power systems used for Z-Pinch experimentation have in the past largely been based on Marx Generators. Marx generators deliver the voltage and current required for the Z-Pinch, but suffer from two significant drawbacks when applied to a flight system: they are very massive, consisting of high-voltage capacitor banks insulated in oil-filled tanks and they do not lend themselves to rapid pulsing. The overall goal of Phase 2 is to demonstrate the construction of a higher voltage stack from a number of cavities each of the design proven in Phase 1 and to characterize and understand the techniques for designing the stack. The overall goal of Phase 3 is to demonstrate the feasibility of constructing a higher energy cavity from a number of smaller LTD stacks, to characterize and understand the way in which the constituent stacks combine, and to extend this demonstration LTD to serve as the basis for a 64 kJ pulse generator for Z-Pinch experiments.

Adams, Robert↗
DOE OSTI2023

A new approach to the design of surface subsystems of polymeric insulators for HV and MV apparatus under AC voltage

The design of high voltage and medium voltage AC and DC standoff insulators, and, in general, of insulation systems where surface and interface properties are predominant factors, is based on specifications and standards that rely upon long-term experiences and lab testing. Surface insulating properties depend on electrical and thermal stresses, besides environmental factors, and the inception of extrinsic ageing phenomena, such as partial discharges, can be already a cause of reduced reliability and premature failure (for organic insulating materials). An innovative approach, based on field simulation, discharge modelling, and partial discharge inception measurements is presented by the authors, which can establish a solid basis to optimise insulation design for any type of supply voltage waveform. This method, the three-leg approach, is applied here to a cable system under AC sinusoidal voltage, but it can work for any type of insulation system, such as bushings, switch gears, transformers, rotating machines, and power electronics boards.

42 ENGINEERING↗
DOE OSTI2023

Vacuum Insulator Flashover Physics LDRD Report

Large, pulsed power and high voltage systems often employ a stack of insulators to separate a vacuum section away from water or oil sections. The size of this insulator stack often drives overall costs and feasibility of these systems. An electric breakdown along the insulator surface is a primary failure mechanism and is especially impactful if it occurs while power is still being delivered downstream. This report describes a set of experimental and modeling investigations into the cause of these breakdowns, especially focusing on the much less well-understood anode-initiated breakdowns that occur during early parts of power delivery. Additionally, new diagnostics for assessing relevant material properties and behavior of insulators are described. These results describe breakdown behavior and evolution at new temporal and spatial fidelities and provide hypotheses and some answers as to how these breakdowns can occur. This new understanding of the roles of different physics phenomena guide modifications and trade-offs in generating newer insulator stack designs that are smaller and/or have higher electrical stress thresholds.

42 ENGINEERING↗
DOE OSTI2025

Mechanical Design of the PIP-II ORBUMP Pulsed Dipole Magnet

The Proton Improvement Plan II (PIP-II) project is a vital upgrade to the Fermilab accelerator complex. The magnet pulse rate of the PIP-II Injection system requires an increase from the current rate of 15 Hz to 20 Hz as well as a roughly 30% increase in the magnetic field of the new Orbital Bump (ORBUMP) pulsed dipole magnets in the Booster. Here, the ORBUMP magnet mechanical design is presented in this paper. The ORBUMP magnet is secured in a vacuum box and the core is made up of 0.127 mm thick, low carbon steel laminations with a C-5 inorganic magnesium phosphate coating. The core is clamped using external tie bars welded to the core end plates. ANSYS Finite Element Analysis (FEA) was used to evaluate the clamping design to minimize the deflection of the core post welding of the tie bars. The water-cooled, single turn coil, which shapes the magnetic field by acting as the pole tips, is critical for the integrated field homogeneity. The coil manufacturing tolerances and fabrication techniques were evaluated to ensure the magnetic properties of the magnet could be obtained. The coil is electrically isolated from the core using virgin Polyether ether ketone (PEEK) insulating material in the gap. An investigation into the high voltage performance of the virgin PEEK insulator was conducted via partial discharge testing using a 1:1 scale sample.

Karas, D. [Fermi National Accelerator Laboratory (↗
DOE OSTI2025

Mechanical Design of the PIP-II ORBUMP Pulsed Dipole Magnet

The Proton Improvement Plan-II (PIP-II) is a vital upgrade to Fermilab's accelerator complex. The upgrade is designed to power the world s most intense high-energy neutrino beam in future experiments. The magnet pulse repetition rate of the PIP-II injection system is being upgraded from 15 Hz to 20 Hz and requires a roughly 30% increase in the magnetic field of the new Orbital Bump (ORBUMP) magnets in the Booster. The magnet is secured in a vacuum box and the core is made up of 0.127 mm thick, low carbon steel laminations with a C-5 inorganic coating. The core is clamped using external tie bars welded to the core end plates. ANSYS Finite Element Analysis (FEA) was used to evaluate the clamping design to minimize the deflection of the core post welding of the tie bars. The water-cooled single turn coil is electrically isolated from the core using virgin PEEK insulating material in the gap. An investigation into the high voltage performance of the virgin PEEK insulator was conducted. The design of the coil which shapes the magnetic field by acting as the pole tips is critical for the integrated field homogeneity. The coil manufacturing tolerances and fabrication techniques were evaluated to ensure the magnetic properties of the magnet could be obtained. The ORBUMP magnet mechanical design is presented in this paper.

Karas, Dino [Fermilab] (ORCID:0000000304340670)↗
NASA NTRS2014

Material Challenges and Opportunities for Commercial Electric Aircraft

Significant reduction in carbon dioxide emission for future air transportation system will require adoption of electric propulsion system and more electric architectures. Various options for aircraft electric propulsion include hybrid electric, turboelectric, and full electric system. Realization of electric propulsion system for commercial aircraft applications will require significant increases in power density of electric motors and energy density of energy storage system, such as the batteries and fuel cells. In addition, transmission of MW of power in the aircraft will require high voltage power transmission system to reduce the weight of the power transmission system. Finally, there will be significant thermal management challenges. Significant advances in material technologies will be required to meet these challenges. Technologies of interest include materials with higher electrical conductivity than Cu, high thermal conductivity materials, and lightweight electrically insulating materials with high breakdown voltage, high temperature magnets, advanced battery and fuel cell materials, and multifunctional materials. The presentation will include various challenges for commercial electric aircraft and provide an overview of material improvements that will be required to meet these challenges.

materials↗
DOE OSTI2023

High Power Density Cost-Effective MVDC Aircraft Cable

To make the power density of electric aircraft closer to conventional aircraft, an electric power system (EPS) with high power delivery and low system mass is necessary. As an essential component of aircraft EPS, cables are necessary to transmit power from one node to another. Virginia Tech will design high-power density, cost-effective ±5 kV cables for twin-aisle all-electric aircraft. Innovations include conductors with increased current-carrying capacity and a multilayer, multifunctional insulation system made of exceptionally high thermal conductivity materials. Designed for DC voltage, the new insulator will allow fewer partial discharge events and provide improved electromagnetic interference protection.

42 ENGINEERING↗
NASA NTRS2008

New Techniques to Evaluate the Incendiary Behavior of Insulators

New techniques for evaluating the incendiary behavior of insulators is presented. The onset of incendive brush discharges in air is evaluated using standard spark probe techniques for the case simulating approaches of an electrically grounded sphere to a charged insulator in the presence of a flammable atmosphere. However, this standard technique is unsuitable for the case of brush discharges that may occur during the charging-separation process for two insulator materials. We present experimental techniques to evaluate this hazard in the presence of a flammable atmosphere which is ideally suited to measure the incendiary nature of micro-discharges upon separation, a measurement never before performed. Other measurement techniques unique to this study include; surface potential measurements of insulators before, during and after contact and separation, as well as methods to verify fieldmeter calibrations using a charge insulator surface opposed to standard high voltage plates. Key words: Kapton polyimide film, incendiary discharges, brush discharges, contact and frictional electrification, ignition hazards, insulators, contact angle, surface potential measurements.

Buhler, Charles↗
NASA NTRS2023

Evaluation of Elements used for Manufacturing of NanoLam Metallized Polymer Film Capacitors

Metallized polymer film capacitors (MPFC) manufactured by NanoLam technology have a better volumetric efficiency and performance that may exceed the reliability of conventional MPFCs typically used in power and high voltage systems that require high insulation resistance and low power losses. These capacitors can be also an effective replacement for electrolytic and stacked ceramic capacitors currently used in space applications looking to save significant volume and mass. This report evaluates the effects of environmental conditions including radiation and storage at room and high temperatures on the characteristics of NanoLam elements used in the production of MPFCs. Assessments of the reliability acceleration factors and predictions for the useful life are made based on highly accelerated life tests (HALT) using distributions of times to parametric failures at different stress conditions. It has been shown that even a relatively small amount of moisture absorbed at room environments in the dielectric layers may substantially change the probability of failure. In the presence of moisture, degradation processes that started after voltage application continue with time during storage.

Metallized polymer film capacitors (MPFC)↗
NASA NTRS1994

Plasma chamber testing of advanced photovoltaic solar array coupons

The solar array module plasma interactions experiment is a space shuttle experiment designed to investigate and quantify the high voltage plasma interactions. One of the objectives of the experiment is to test the performance of the Advanced Photovoltaic Solar Array (APSA). The material properties of array blanket are also studied as electric insulators for APSA arrays in high voltage conditions. Three twelve cell prototype coupons of silicon cells were constructed and tested in a space simulation chamber.

TRT-EXPERIMENTAL↗
DOE OSTI2022

Pulsed-Power Innovations for Next-Generation, High-Current Drivers

There are proposals to build larger high-current drivers to be used for high-energy-density physics (HEDP), inertial confinement fusion (ICF), radiation effects testing, and basic science. Drivers significantly larger than the Z Machine at Sandia National Laboratories, Albuquerque, NM, USA, encounter increasing difficulties in water power flow, insulator performance, and vacuum power flow. The physics requirements of imploding loads limit a designer’s flexibility in choosing machine parameters, such as current rise time, driving impedance, and total inductance. This article enumerates these physics constraints and shows how they impact driver design. Here, we conclude that advances in pulsed-power capabilities are needed to control risk and to build a cost-effective driver at peak currents of ~60 MA.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

An SF 6 gas-insulated −500 kV DC conical insulator vacuum feedthrough

A test electrode was biased to −500 kV direct current (DC) by means of a novel SF 6 gas-insulated conical alumina insulator feedthrough. The design enables the extreme high vacuum conditions required by spin-polarized electron sources by reducing the photogun vacuum chamber volume compared to coaxial cylindrical insulators. In contrast to conventional inverted-insulator photogun designs that rely on solid dielectric interfaces for high-voltage terminations, the present design employs a pressurized SF 6 intervening volume between a conical alumina insulator and a modified commercial epoxy high-voltage cable receptacle. Here, this approach enables the use of commercially available cable hardware while extending the demonstrated operating voltage of solid feedthroughs. A maximum voltage of −500 kV was applied to a test electrode attached to the narrow end of the feedthrough inside a chamber filled with SF 6 at 170.3 kPa (10 psig) and later under vacuum to −259 kV, limited by field emission. The results demonstrate that a commercial high-voltage cable combined with a custom-designed SF 6 gas-insulated vacuum feedthrough can be used to bias photogun electrodes to −500 kV DC.

Palacios-Serrano, Gabriel [Thomas Jefferson Nation↗