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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Thermal Analysis of Potted Litz Wire for High-Power-Density Aerospace Electric Machines

Increasing the power density and efficiency of electric machines (motors and generators) is integral to bringing Electrified Aircraft (EA) to commercial realization. To that end an effort to create a High Efficiency Megawatt Motor (HEMM) with a goal of exceeding 98% efficiency and 1.46 MW of power has been undertaken at the NASA Glenn Research Center. Of the motor components the resistive losses in the stator windings are by far the largest contributor (34%) to total motor loss. The challenge is the linear relationship between resistivity and temperature, making machine operation sensitive to temperature increases. In order to accurately predict the thermal behavior of the stator the thermal conductivity of the Litz wire-potting-electrical insulation system must be known. Unfortunately, this multi material system has a wide range of thermal conductivities (0.1 W/m-K – 400 W/m-K) and a high anisotropy (axial vs transverse) making the prediction of the transverse thermal conductivity an in turn the hot spot temperatures in the windings is difficult. In order to do this a device that simulates the thermal environment found in the HEMM stator was designed. This device is not unlike the motorettes (little motors) that are described in IEEE standards for testing electrical insulation lifetimes or other electric motor testing. However, because the HEMM motor design includes significant rotor electrical and thermal considerations the term motorette was not deemed appropriate. Instead statorette (or little stator) was adopted as the term for this test device. This paper discussed the design, thermal heat conjugate analysis (thermal model), manufacturing and testing of HEMM's statorette. Analysis of the results is done by thermal resistance network model and micro thermal model and is compared to analytical predictions of thermal conductivity of the insulated and potted Litz wire system.

Motor↗
NASA NTRS2001

Packaging Technology Developed for High-Temperature Silicon Carbide Microsystems

High-temperature electronics and sensors are necessary for harsh-environment space and aeronautical applications, such as sensors and electronics for space missions to the inner solar system, sensors for in situ combustion and emission monitoring, and electronics for combustion control for aeronautical and automotive engines. However, these devices cannot be used until they can be packaged in appropriate forms for specific applications. Suitable packaging technology for operation temperatures up to 500 C and beyond is not commercially available. Thus, the development of a systematic high-temperature packaging technology for SiC-based microsystems is essential for both in situ testing and commercializing high-temperature SiC sensors and electronics. In response to these needs, researchers at Glenn innovatively designed, fabricated, and assembled a new prototype electronic package for high-temperature electronic microsystems using ceramic substrates (aluminum nitride and aluminum oxide) and gold (Au) thick-film metallization. Packaging components include a ceramic packaging frame, thick-film metallization-based interconnection system, and a low electrical resistance SiC die-attachment scheme. Both the materials and fabrication process of the basic packaging components have been tested with an in-house-fabricated SiC semiconductor test chip in an oxidizing environment at temperatures from room temperature to 500 C for more than 1000 hr. These test results set lifetime records for both high-temperature electronic packaging and high-temperature electronic device testing. As required, the thick-film-based interconnection system demonstrated low (2.5 times of the room-temperature resistance of the Au conductor) and stable (decreased 3 percent in 1500 hr of continuous testing) electrical resistance at 500 C in an oxidizing environment. Also as required, the electrical isolation impedance between printed wires that were not electrically joined by a wire bond remained high (greater than 0.4 GW) at 500 C in air. The attached SiC diode demonstrated low (less than 3.8 W/mm2) and relatively consistent dynamic resistance from room temperature to 500 C. These results indicate that the prototype package and the compatible die-attach scheme meet the initial design standards for high-temperature, low-power, and long-term operation. This technology will be further developed and evaluated, especially with more mechanical tests of each packaging element for operation at higher temperatures and longer lifetimes.

Chen, Liang-Yu↗
NASA NTRS2018

Lightweight, Durable, and Multifunctional Electrical Insulation Material Systems for High Voltage Applications

Newly developed multilayer structures of well-known polymer insulation materials significantly improved dielectric breakdown voltage, VB, or dielectric strength, K, if well-bonded, when compared to those of single material insulations or the commercial SOA systems, such as Teflon-Kapton-Teflon (TKT), at the same overall thickness. To date, the greatest improvement of the new structures from a few candidate materials, including various types of Kapton PIs and PFA or PET as bond layer (BL), was about 61% higher than that of the Kapton PI alone films, 40.1 vs. 24.9 kV, which was translated to 86.3% decrease in insulation thickness, thus significant volume and weight reduction of the final system. However, it was of interest to note that most improvements of the multilayer structures occurred at thicker overall thicknesses, above ~ 0.15 mm. Extensive analyses also showed that K of the multilayer structures increased with (i) decreasing individual layer thickness regardless of material type, (ii) increasing total accumulated thickness of PI or overall PI/BL ratio, and (iii) increasing number of interface or total number of layers, but only above the aforementioned overall thickness limit. Increases in VB of the multilayer structures were directly correlated with damage evolution and failure mode. With further material-design-process optimizations of the multilayer structures, it was expected to achieve other multifunctionalities, such as high partial discharge (PD) resistance, improved durability, EMI shielding, and high thermal dissipation in addition to high dielectric strength. These new structures can be used in various high voltage and high temperature applications, such as future hybrid or all electric aircraft wiring and power transmission as well as many other non-aerospace high power cables, electronic parts and components, printed circuit board, and so forth. The multilayer insulation system can be easily processed and manufactured with various conductor types via calendaring, compression-molding, stamping, laminating, vacuum-bagging and autoclaving, or 3D printing, even for complex 3-D components. Based on their unique structural configurations and potential capabilities, the new insulation system was identified as micro-multilayer multifunctional electrical insulation (MMEI). Patent application of the MMEI concept and current design configurations was filed for a 1-year provisional application (OAI-58834, Serial No.: 62/659,234), pending conversion to a U.S. utility application. This paper presents details of the MMEI structures, their dielectric performance analyses, potential mechanisms, and commercial scaleup feasibility assessment.

Electric aircrafts↗
NASA NTRS2018

Lightweight, Durable, and Multifunctional Electrical Insulation Material Systems for High Voltage Applications

Newly developed multilayer structures of well-known polymer insulation materials significantly improved dielectric breakdown voltage, VB, or dielectric strength, K, if well-bonded, when compared to those of single material insulations or the commercial SOA systems, such as Teflon-Kapton-Teflon (TKT), at the same overall thickness. To date, the greatest improvement of the new structures from a few candidate materials, including various types of Kapton PIs and PFA or PET as bond layer (BL), was about 61% higher than that of the Kapton PI alone films, 40.1 vs. 24.9 kV, which was translated to 86.3% decrease in insulation thickness, thus significant volume and weight reduction of the final system. However, it was of interest to note that most improvements of the multilayer structures occurred at thicker overall thicknesses, above ~ 0.15 mm. Extensive analyses also showed that K of the multilayer structures increased with (i) decreasing individual layer thickness regardless of material type, (ii) increasing total accumulated thickness of PI or overall PI/BL ratio, and (iii) increasing number of interface or total number of layers, but only above the aforementioned overall thickness limit. Increases in VB of the multilayer structures were directly correlated with damage evolution and failure mode. With further material-design-process optimizations of the multilayer structures, it was expected to achieve other multifunctionalities, such as high partial discharge (PD) resistance, improved durability, EMI shielding, and high thermal dissipation in addition to high dielectric strength. These new structures can be used in various high voltage and high temperature applications, such as future hybrid or all electric aircraft wiring and power transmission as well as many other non-aerospace high power cables, electronic parts and components, printed circuit board, and so forth. The multilayer insulation system can be easily processed and manufactured with various conductor types via calendaring, compression-molding, stamping, laminating, vacuum-bagging and autoclaving, or 3D printing, even for complex 3-D components. Based on their unique structural configurations and potential capabilities, the new insulation system was identified as micro-multilayer multifunctional electrical insulation (MMEI). Patent application of the MMEI concept and current design configurations was filed for a 1-year provisional application (OAI-58834, Serial No.: 62/659,234), pending conversion to a U.S. utility application. This paper presents details of the MMEI structures, their dielectric performance analyses, potential mechanisms, and commercial scaleup feasibility assessment.

Multifunctional↗
NASA NTRS1991

Intramuscular Contact Lead Filled With Conductive Solution

Proposed sheath for braided-wire intramuscular conductor preserves electrical continuity even if wire breaks. Plastic sheath surrounds conductive solution in which braided wire immersed. At end of cable, wire and sheath crimped together and press-fit in porous titanium electrode. Implanted surgically with aid of device resembling catheter. Used to deliver electrical stimuli to muscles in biomedical research on human and animal physiology, development of prostheses, regeneration of nerves and muscles, and artificial implants.

Bamford, Robert M.↗
NASA NTRS2021

Improved Potting of Litz Wires for High Power Density Electric Motor

Specific details including selections of process materials, tooling/fixture setups, and a step-by-step procedure for scaling-up demonstrations of the newly developed potting process, namely vacuum-assisted axial injection potting (VaAIP) have been fully developed for the stator winding of high power density electric motors for the future electrified aircrafts. Various essential pre-trial subtasks identified for the full-scale demonstrations were carried out. To date, optimization of cure condition and thermal stability of the coating epoxy and determination of optimum application conditions and thermal stability of the high temperature encapsulant wax were completed successfully and other subtasks were under way. The efforts to enhance thermal conductivity of the selected potting compound by adding conductive nano fillers such as boron nitride nanosheets (BNNS) have also been advanced. Initially, selection of the best mixing method and procedures was attempted via extensive and systematic experimental design.

Litz wire↗
NASA NTRS1964

A physical criterion for metal ignition.

Ignition temperatures of magnesium ribbon and aluminum wire samples electrically heated in argon-oxygen-carbon dioxide-water vapor mixtures

COMBUSTION TEMPERATURE↗
NASA NTRS1968

Nonstructural materials for aerospace.

Aerospace applications of nonstructural materials, discussing potting compounds, conformal coatings, wire insulation, electrical contact materials, lubricants, etc

Kingsbury, J. E.↗
NASA NTRS1972

Oscillating hot-wire anemometer

Performance analysis was made of oscillating hot-wire anemometer electrical output in gas stream. Advantages include no calibration and measurement of fluid direction as well as fluid speed.

Conley, J. M.↗
NASA NTRS1973

Development of high temperature strain gages

High temperature electric resistance wire strain gages were developed and evaluated for use at temperatures exceeding 922 K (1200 F). A special high temperature strain gage alloy (Fe-25Cr-7.5A1), designated BCL-3, was used to fabricate the gages. Pertinent gage characteristics were determined at temperatures up to 1255 K (1800 F). The results of the evaluation were reported in graphical and tabular form. It was concluded that the gages will perform satisfactorily at temperatures to at least 1089 K (1500 F) for at least one hour.

Lemcoe, M. M.↗
NASA NTRS1981

Compliant transducer measures artery profile

Instrument consisting of compliant fingers with attached semiconductor pickups measures inside contours of narrow vessels. Instrument, originally designed to monitor human arteries, is drawn through vessel to allow finges to follow contours. Lead wires transmit electrical signals to external processing equipment.

Feldstein, C.↗