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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Bidirectional dc-to-dc Power Converter

Solid-state, series-resonant converter uses high-voltage thyristors. Converter used either to convert high-voltage, low-current dc power to lowvoltage, high current power or reverse. Taking advantage of newly-available high-voltage thyristors to provide better reliability and efficiency than traditional converters that use vacuum tubes as power switches. New converter essentially maintenance free and provides greatly increased mean time between failures. Attractive in industrial applications whether or not bidirectional capability is required.

Griesbach, C. R.↗
NASA NTRS1994

A study of DC-DC converters with MCT's for arcjet power supplies

Many arcjet DC power supplies use PWM full bridge converters with large arrays of parallel FET's. This report investigates an alternative supply using a variable frequency series resonant converter with small arrays of parallel MCT's (metal oxide semiconductor controlled thyristors). The reasons for this approach are to: increase reliability by reducing the number of switching devices; and decrease the surface mounting area of the switching arrays. The variable frequency series resonant approach is used because the relatively slow switching speed of the MCT precludes the use of PWM. The 10 kW converter operated satisfactorily with an efficiency of over 91 percent. Test results indicate this efficiency could be increased further by additional optimization of the series resonant inductor.

Stuart, Thomas A.↗
NASA NTRS2024

Clock Synchronization Characterization of the Washington DC Metropolitan Area Quantum Network (DC-QNet)

Quantum networking protocols relying on interference and precise time-of-flight measurements require high-precision clock synchronization. This study describes the design, implementation, and characterization of two optical time transfer methods in a metropolitan-scale quantum networking research testbed. With active electronic stabilization, sub-picosecond time deviation (TDEV) was achieved at integration times between 1 s and 10 5 s over 53 km of deployed fiber. Over the same integration periods, 10-picosecond level TDEV was observed using the White Rabbit-Precision Time Protocol (WR-PTP) over 128 km. Measurement methods are described to understand the sources of environmental fluctuations on clock synchronization towards the development of in-situ compensation methods. Path delay gradients, chromatic dispersion, polarization drift, and optical power variations all contributed to clock synchronization errors. The results from this study will inform future work in the development of link noise management methods essential for enabling experimental research in developing practical quantum networking protocols.

PIKTime↗
DOE OSTI2026

Urban Parameters Washington, DC 100m

132 Urban parameters based on building physical dimensions and location were generated for Washington, District of Columbia at 100m resolution using the NATURF model. To use the binary file with WRF, the binary file and the index file must be placed in their own directory in WRF_GEOG and accessed in the same way NUDAPT44 would be accessed.

Dumas, Melissa [ORNL] (ORCID:0000000233190846)↗
NASA NTRS1970

Efficient/reliable dc-to-dc inverter circuit

Feedback loop, which contains an inductor in series with a saturable reactor, is added to a standard inverter circuit to permit the inverter power transistors to be switched in a controlled and efficient manner. This inverter is applicable where the power source has either high or low impedance properties.

Pasciutti, E. R.↗
NASA NTRS1973

Development of a uninterrupted power system: ac and dc to dc converter

This program covered the design, fabrication and testing of an advanced development model uninterrupted power system. The input and output requirements imposed on the power processor were specified such that the unit is electrically interchangeable with existing power systems used by the Federal Aviation Administration in installations which have a history of failure due to electrical transient conditions. Input power is from either of two single-phase ac power sources or batteries with electronic selection and transfer between power sources. Battery reconditioning is automatic when either ac source is present. The output power is rated at 84OW; the nominal output is 24V at 35A. Within the 84OW limit, the regulated output voltage is adjustable from 22V to 30Vdc. Protection against continuous overloading or short circuit is provided. The unit is packaged in a standard 19-inch rack mount configuration with 7-inch panel height. Controls are on the front panel with power input and output through connectors on the rear surface. Cooling is by free convection from fin areas located on the side and rear panels. The packaged unit weighs 52.8 lbs., which can be reduced significantly if a three-phase ac power source is used.

Cronin, D. L.↗
NASA NTRS1975

Time domain modelling and stability analysis of an integral pulse frequency modulated dc to dc power converter

Using state variable representation a nonlinear, discrete-time system is derived that models the converter exactly. This system is linearized about its steady state solution, and converter stability, transient response and audio susceptibility are studied. The steady state solution of the converter is stable if and only if all the roots of the linearized system are absolutely less than unity. Excellent agreement with laboratory test data has been observed.

Iwens, R. P.↗
NASA NTRS1976

DC-to-DC conversion with voltage multipliers

Compact device uses transformerless capacitor/diode voltage multiplier. Advantages include efficiency at high power levels, increased reliability due to elimination of magnetics and associated electrical transients, no magnetic shielding requirement, and adaptability to modular or integrated circuit systems.

Harrigill, W. T., Jr.↗
NASA NTRS1977

A nonsaturating dc-to-dc parallel power converter

Device is conventional circuit modified with pair of diode rectifiers coupled to switching transistors via feedback winding. Transient-causing collector-current overlap between transistors is eliminated. Technique may be used with nonsaturating parallel-transistor converters operating from voltage source which remains fixed or varies over small range.

Lavigna, T.↗
NASA NTRS1976

The dc-to-dc converters employing staggered-phase power switches with two-loop control

A switched inductor voltage is coupled to a sense winding in each phase, and all sense windings are connected in series to one of two feedback loops to provide a signal that indicates when one of the power switches is on as the principal determinant of switching instants. A sequencer is triggered each time a pulse generator is triggered to turn on a different power switch in sequence at each switching instant.

Wester, G. W.↗