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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

PWM Switching Frequency Effects on Eddy Current Sensors for Magnetically Suspended Flywheel Systems

A flywheel magnetic bearing (MB) pulse width modulated power amplifier (PWM) configuration is selected to minimize noise generated by the PWMs in the flywheel position sensor system. Two types of noise are addressed: beat frequency noise caused by variations in PWM switching frequencies, and demodulation noise caused by demodulation of high order harmonics of the switching voltage into the MB control band. Beat frequency noise is eliminated by synchronizing the PWM switch frequencies, and demodulation noise is minimized by selection of a switching frequency which does not have harmonics at the carrier frequency of the sensor. The recommended MB PWM system has five synchronized PWMs switching at a non-integer harmonic of the sensor carrier.

Jansen, Ralph↗
NASA NTRS1982

Transistorized PWM inverter-induction motor drive system

This paper describes the development of a transistorized PWM inverter-induction motor traction drive system. A vehicle performance analysis was performed to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of inverter and motor specifications. The inverter was a transistorized three-phase bridge using General Electric power Darlington transistors. The description of the design and development of this inverter is the principal object of this paper. The high-speed induction motor is a design which is optimized for use with an inverter power source. The primary feedback control is a torque angle control with voltage and torque outer loop controls. A current-controlled PWM technique is used to control the motor voltage. The drive has a constant torque output with PWM operation to base motor speed and a constant horsepower output with square wave operation to maximum speed. The drive system was dynamometer tested and the results are presented.

Peak, S. C.↗
NASA NTRSDate not supplied

Ground-based Characterization of Plant Water Management (PWM) Hydroponic Root Modules for Spaceflight

Hydroponic crop production in space is crucial for long-term space travel but faces numerous challenges – one of which is providing sufficient dissolved oxygen (DO) in nutrient solution. In microgravity environments, surface tension is the primary force acting on liquids, causing water to form into suspended spherical droplets. This can suffocate plants as the liquid clings onto plant roots and the lack of aeration deprives the plant of oxygen needed for growth. To overcome these challenges, plant water management (PWM) systems explore options of growing plants in space autonomously and passively through capillary forces. From 2018-2023, there have been 6 PWM experiments conducted on the ISS. In past experiments conducted in microgravity, bubbles formed in test cells have disrupted fluid dynamics and may adversely affect plant growth. The accumulation of bubbles may lead to inconsistent nutrient delivery, break prime in tubing, and suspend plant roots in air, leading to plant stress and eventually death. Current research efforts focus on the oxygenation capabilities of the PWM system along with a comprehensive sensor array that will improve nutrient and DO monitoring capabilities.

L Wang↗
NASA NTRS1993

Design of a ZVS PWM inverter for a brushless DC motor in an EMA application

The Component Development Division of the Propulsion Laboratory at Marshall Space Flight Center (MSFC) is currently investigating the use of electromechanical actuators for use in space transportation applications such as Thrust Vector Control (TVC). These high power servomechanisms will require rugged, reliable, and compact power electronic modules capable of modulating several hundred amperes of current at up to 270 Vdc. This paper will discuss the design and implementation of a zero-voltage-switched PWM (Pulse Width Modulation) inverter which operates from a 270 Vdc source at currents up to 100 A.

Bell, J. Brett↗
NASA NTRS1995

Asymmetric Switching For A PWM H-Bridge Power Circuit

Only two of four switches interrupt substantial current. An asymmetric timing scheme improves design and operation of pulse-width-modulation (PWM) H-bridge switch-and-transformer circuit. Circuit part of dc-to-dc converter or dc-to-ac inverter; in either case, output current or voltage regulated by adjusting times of opening and closing of semiconductor switches 1 through 4 to adjust durations of current pulses in primary winding of transformer.

Wong, See-Pok↗
NASA NTRS2001

Performance of High-Speed PWM Control Chips at Cryogenic Temperatures

The operation of power electronic systems at cryogenic temperatures is anticipated in many NASA space missions such as planetary exploration and deep space probes. In addition to surviving the space hostile environment, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. As part of the NASA Glenn Low Temperature Electronics Program, several commercial high-speed Pulse Width Modulation (PWM) chips have been characterized in terms of their performance as a function of temperature in the range of 25 to -196 C (liquid nitrogen). These chips ranged in their electrical characteristics, modes of control, packaging options, and applications. The experimental procedures along with the experimental data obtained on the investigated chips are presented and discussed.

Elbuluk, Malik E.↗
NASA NTRS2004

Inverter Output Filter Effect on PWM Motor Drives of a Flywheel Energy Storage System

NASA Glenn Research Center (GRC) has been involved in the research and development of high speed flywheel systems for small satellite energy storage and attitude control applications. One research and development area has been the minimization of the switching noise produced by the pulsed width modulated (PWM) inverter that drives the flywheel permanent magnet motor/generator (PM M/G). This noise can interfere with the flywheel M/G hardware and the system avionics hampering the full speed performance of the flywheel system. One way to attenuate the inverter switching noise is by placing an AC filter at the three phase output terminals of the inverter with the filter neutral point connected to the DC link (DC bus) midpoint capacitors. The main benefit of using an AC filter in this fashion is the significant reduction of the inverter s high dv/dt switching and its harmonics components. Additionally, common mode (CM) and differential mode (DM) voltages caused by the inverter s high dv/dt switching are also reduced. Several topologies of AC filters have been implemented and compared. One AC filter topology consists of a two-stage R-L-C low pass filter. The other topology consists of the same two-stage R-L-C low pass filter with a series connected trap filter (an inductor and capacitor connected in parallel). This paper presents the analysis, design and experimental results of these AC filter topologies and the comparison between the no filter case and conventional AC filter.

Santiago, Walter↗
NASA NTRS2019

Plant Water Management (PWM) Experiment

Plant Water Management is a technology demonstration of recent advances in micro-g capillary fluidics research applied to plant growth systems. It has applications in long-term food production systems for missions to the Moon and Mars, as well as the immediate need for ISS food supplements to the crew diet. PWM will demonstrate the low-gravity role of surface tension, wetting, and system geometry to effectively replace the role of gravity in certain terrestrial plant growth systems.

Hatch, Tyler↗
NASA NTRS1979

Improved ripple rejection in a PWM

Line-ripple rejection of pulse-width modulator is more than doubled by substituting exponentially increasing ramp voltage for conventional linear ramp, yet circuit is simplified.

Loftis, C. B., Jr.↗
NASA NTRS1981

A PWM transistor inverter for an ac electric vehicle drive

A prototype system consisting of closely integrated motor, inverter, and transaxle has been built in order to demonstrate the feasibility of a three-phase ac transistorized inverter for electric vehicle applications. The microprocessor-controlled inverter employs monolithic power transistors to drive an oil-cooled, three-phase induction traction motor at a peak output power of 30 kW from a 144 V battery pack. Transistor safe switching requirements are discussed, and a circuit is presented for recovering trapped snubber inductor energy at transistor turn-off.

Slicker, J. M.↗
NASA NTRS1993

Analysis of a PWM-Resonant DC-TO-DC Converter

When a parallel resonant tank is excited by a bipolar current pulse train a sinusoidal voltage develops across the tank whose amplitude depends on the duty cycle of the pulse train.

Converter Resonant Tank↗
NASA NTRS2019

Plant Water Management (PWM)

The NASA Plant Water Management technology demonstration exploits recent advances in microgravity capillary fluidics to develop techniques for plant growth in a space environment. Plant growth in the low-g environment is often hampered by inadequate aeration and over-saturation in the root zone. The present effort aims to make passive use of poorly wetting liquids (i.e., contaminated water) within unique system geometries that effectively replace the role of gravity in providing sufficient aeration and hydration for simulated plants. Several ISS demonstrations are in preparation for launch in 2019, including hydroponic and soil approaches. Supportive terrestrial and low-g drop tower tests are conducted to aid in experiment design via proof-of-concepts, limits of operation, system stability, and others. The implications to short and long term applications are discussed in relation to plant growth facilities for both near-term microgravity plant science research and long duration human exploration missions.

Hatch, Tyler↗
NASA NTRS1993

Pulse-Modulation Scheme For Voice And Telemetry

Pulse-modulation scheme provides for transmission of 1 channel of voice information along with 16 channels of serially multiplexed analog iotelemetric information, all on single radio-frequency carrier signal. Encoder/multiplexer combination effects PMD scheme, in which biotelemetry encoded in time-division multiplex PIM, while voice encoded in PWM. Combination of PIM and PWM encoding called "pulse modulated data" or PMD. Principal advantage of scheme simplicity: comodulation of voice along with biotelemetry involves minimal additional circuitry in transmitter. In receiver, biotelemetric data extracted by ordinary PIM-encoding circuitry, not affected by voice PWM; and simple PWM decoder added to receiver to recover voice.

Mills, William J.↗
NASA NTRS2007

Multiloop Rapid-Rise/Rapid Fall High-Voltage Power Supply

A proposed multiloop power supply would generate a potential as high as 1.25 kV with rise and fall times <100 s. This power supply would, moreover, be programmable to generate output potentials from 20 to 1,250 V and would be capable of supplying a current of at least 300 A at 1,250 V. This power supply is intended to be a means of electronic shuttering of a microchannel plate that would be used to intensify the output of a charge-coupled-device imager to obtain exposure times as short as 1 ms. The basic design of this power supply could also be adapted to other applications in which high voltages and high slew rates are needed. At the time of reporting the information for this article, there was no commercially available power supply capable of satisfying the stated combination of voltage, rise-time, and fall-time requirements. The power supply would include a preregulator that would be used to program a voltage 1/30 of the desired output voltage. By means of a circuit that would include a pulse-width modulator (PWM), two voltage doublers, and a transformer having two primary and two secondary windings, the preregulator output voltage would be amplified by a factor of 30. A resistor would limit the current by controlling a drive voltage applied to field-effect transistors (FETs) during turn-on of the PWM. Two feedback loops would be used to regulate the high output voltage. A pulse transformer would be used to turn on four FETs to short-circuit output capacitors when the outputs of the PWM were disabled. Application of a 0-to-5-V square to a PWM shut-down pin would cause a 20-to-1,250-V square wave to appear at the output.

Bearden, Douglas↗
NASA NTRS2007

High-Voltage Power Supply With Fast Rise and Fall Times

A special-purpose high-voltage power supply can be electronically switched on and off with fast rise and fall times, respectively. The output potential is programmable from 20 to 1,250 V. An output current of 50 A can be sustained at 1,250 V. The power supply was designed specifically for electronically shuttering a microchannel plate in an x-ray detector that must operate with exposure times as short as 1 ms. The basic design of the power supply is also adaptable to other applications in which there are requirements for rapid slewing of high voltages. The power-supply circuitry (see figure) includes a preregulator, which is used to program the output at 1/30 of the desired output potential. After the desired voltage has been set, the outputs of a pulse width modulator (PWM) are enabled and used to amplify the preregulator output potential by 30. The amplification is achieved by use of two voltage doublers with a transformer that has two primary and two secondary windings. A resistor is used to limit the current by controlling the drive voltage of two field-effect transistors (FETs) during turn-on of the PWM. A pulse transformer is used to turn on four FETs to short-circuit four output capacitors when the outputs of the PWM have been disabled. The most notable aspects of the performance of the power supply are a rise time of only 80 s and a fall time of only 60 s at a load current of 50 A or less. Another notable aspect is that the application of a 0-to-5-V square wave to a shutdown pin of the PWM causes the production of a 0-to-1,250-V square wave at the output terminals.

Bearden, Douglas B.↗