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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Induction graphitizing furnace acceptance test report

The induction furnace was designed to provide the controlled temperature and environment required for the post-cure, carbonization and graphitization processes for the fabrication of a fibrous graphite NERVA nozzle extension. The acceptance testing required six tests and a total operating time of 298 hrs. Low temperature mode operations, 120 to 850 C, were completed in one test run. High temperature mode operations, 120 to 2750 C, were completed during five tests.

Source record↗
NASA NTRS1973

Induction motor control system with voltage controlled oscillator circuit

A voltage controlled oscillator circuit is reported in which there are employed first and second differential amplifiers. The first differential amplifier, being employed as an integrator, develops equal and opposite slopes proportional to an input voltage, and the second differential amplifier functions as a comparator to detect equal amplitude positive and negative selected limits and provides switching signals which gate a transistor switch. The integrating differential amplifier is switched between charging and discharging modes to provide an output of the first differential amplifier which upon the application of wave shaping provides a substantially sinusoidal output signal. A two phased version with a second integrator provides a second 90 deg phase shifted output for induction motor control.

Nola, F. J.↗
NASA NTRS1973

Optimum windings for linear induction machines.

The matrix method of calculating linear induction machine performance as a function of winding current distribution was extended to determine the winding current distribution for maximum efficiency. Application of the method to typical magnetohydrodynamic generator geometries showed that electrical efficiencies of 0.5 to 0.6 are possible with fractional wavelength windings and without insulating vanes in the flow.

Elliott, D. G.↗
NASA NTRS1973

NASTRAN buckling study of a linear induction motor reaction rail

NASTRAN was used to study problems associated with the installation of a linear induction motor reaction rail test track. Specific problems studied include determination of the critical axial compressive buckling stress and establishment of the lateral stiffness of the reaction rail under combined loads. NASTRAN results were compared with experimentally obtained values and satisfactory agreement was obtained. The reaction rail was found to buckle at an axial compressive stress of 11,400 pounds per square inch. The results of this investigation were used to select procedures for installation of the reaction rail.

Williams, J. G.↗
NASA NTRS1974

Feasibility study of a swept frequency electromagnetic probe (SWEEP) using inductive coupling for the determination of subsurface conductivity of the earth and water prospecting in arid regions

Techniques developed for electromagnetic probing of the lunar interior, and techniques developed for the generation of high power audio frequencies were combined to make practical a magnetic inductive coupling system for the rapid measurement of ground conductivity profiles which are helpful when prospecting for the presence and quality of subsurface water. A system which involves the measurement of the direction, intensity, and time phase of the magnetic field observed near the surface of the earth at a distance from a horizontal coil energized so as to create a field that penetrates the earth was designed and studied to deduce the conductivity and stratification of the subsurface. Theoretical studies and a rudimentary experiment in an arid region showed that the approach is conceptually valid and that this geophysical prospecting technique can be developed for the economical exploration of subterranean water resources.

Latorraca, G. A.↗
NASA NTRS1974

Polarized magnetic field fluctuations at the Apollo 15 site - Possible regional influence on lunar induction

High-frequency (5 to 40 millihertz) induced lunar magnetic fields, observed at the Apollo 15 site near the southeastern boundary of Mare Imbrium and the southwestern boundary of Mare Serenitatis, show a strong tendency toward linear polarization in a direction radial to the Imbrium basin and circumferential to the Serenitatis basin, a property that could be indicative of a possible regional influence on the induction.

Schubert, G.↗
NASA NTRS1975

Variable frequency inverter for ac induction motors with torque, speed and braking control

A variable frequency inverter was designed for driving an ac induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a dc power source.

Nola, F. J.↗
NASA NTRS1975

Electromagnetic induction in spherical cap current layers under lunar and terrestrial conditions

Attention is given to electromagnetic induction in infinitesimally thin spherical cap current layers of arbitrary size and arbitrary axisymmetric integrated conductivity, taking into account a location at nonzero but otherwise arbitrary depth beneath the surface of observation. The description of a theoretical model is presented and the induced fields computed from the theoretical formulas for several different spherical cap models are discussed.

Schubert, G.↗
NASA NTRS1975

Sheath-limited unipolar induction in the solar wind

A model of the steady-state interaction between the solar wind and an electrically conducting body having neither an atmosphere nor an intrinsic magnetic field sufficient enough to deflect the plasma flow is presented which considers some effects of a plasma surface sheath on unipolar induction. The Sonett-Colburn (1967, 1968) unipolar dynamo model is reviewed, and it is noted that the unipolar dynamo response of an electrically conducting body in the solar wind's motional field can be controlled by sheath effects in certain cases where the body radius is less than a certain critical value. It is shown that sheath effects do not limit the unipolar response of the moon or Mercury since their body radii are much larger than their critical radii. Sheath effects are also considered for asteroids, the Martian satellites, the irregular Jovian satellites, the outer satellites of Saturn, and meteorite parent bodies in a primordial enhanced solar wind.

Srnka, L. J.↗
NASA NTRS1977

Direct-reading inductance meter

Meter indicates from 30 nH to 3 micro H. Reference inductor of 15 micro H is made by winding 50 turns of Number 26 Formvar wire on Micrometal type 50-2 (or equivalent) core. Circuit eliminates requirement for complex instrument compensation prior to taking coil inductance measurement and thus is as easy to operate as common ohmmeter.

Kolbly, R. B.↗
NASA NTRS1976

FORTRAN program for induction motor analysis

A FORTRAN program for induction motor analysis is described. The analysis includes calculations of torque-speed characteristics, efficiency, losses, magnetic flux densities, weights, and various electrical parameters. The program is limited to three-phase Y-connected, squirrel-cage motors. Detailed instructions for using the program are given. The analysis equations are documented, and the sources of the equations are referenced. The appendixes include a FORTRAN symbol list, a complete explanation of input requirements, and a list of error messages.

Bollenbacher, G.↗
NASA NTRS1977

Save power in AC induction motors

Relatively simple and inexpensive circuitry improves power factor and reduces power dissipation in induction motors operating below full load. Electronic control loop conserves energy by reducing voltage applied to lightly loaded motor. Circuit forces motor to run at constant predetermined optimum power factor, regardless of load or line voltage variations. Solid-state switch varies voltage.

Nola, F. J.↗
NASA NTRS1977

Low-inductance bus lines

Laminated bus strips and bifilar litz cable connectors for high-power rectifiers, thrisistors, and transistors provide low inductance and eliminate electromagnetic interference in high-power circuits. These techniques offer significant cost advantages because of ease of assembly and consistent high quality of product. Effectiveness makes general usage in static power conversion likely.

Kernick, A.↗
NASA NTRS1977

Performance characteristics of three-phase induction motors

An investigation into the characteristics of three phase, 400 Hz, induction motors of the general type used on aircraft and spacecraft is summarized. Results of laboratory tests are presented and compared with results from a computer program. Representative motors were both tested and simulated under nominal conditions as well as off nominal conditions of temperature, frequency, voltage magnitude, and voltage balance. Good correlation was achieved between simulated and laboratory results. The primary purpose of the program was to verify the simulation accuracy of the computer program, which in turn will be used as an analytical tool to support the shuttle orbiter.

Wood, M. E.↗
NASA NTRS1977

Some consequences of solar wind induction in the moon

A review is given of empirical and theoretical research into lunar induction excited by the solar wind. Transfer functions are discussed along with the bulk electrical-conductivity profile for the moon, limits on resolution and uniqueness, and comparisons of various conductivity models. Estimates of the lunar internal temperature profile are examined, sources for permanent magnetization of lunar rocks are considered, and the extreme frequency limit for detection of a lunar core is assessed. It is noted that there is no convincing evidence for a metallized lunar core with a radius of 500 km or larger.

Sonett, C. P.↗
NASA NTRS1977

A new source of lunar electromagnetic induction - Forcing by the diamagnetic cavity

Analysis of the power spectral densities (PSD's) of eight 50-hour time series from Apollo 12 lunar surface magnetometer (LSM) and isochronous Explorer 35 Ames magnetometer data points to the existence of a new source of electromagnetic induction in the interior of the moon which is independent of the transverse electric mode. This source is hypothesized to arise from extension of the cavity diamagnetic field into the moon in analogy with the fringing field of a solenoid.

Sonett, C. P.↗
NASA NTRS1978

Three-phase induction motors

Program simulates performance characteristics of three-phase induction motors under normal conditions and extreme temperature, frequency, voltage magnitude, and voltage balance.

Wood, M. E.↗