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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Active Gas-Gap Heat Switch with Fast Thermal Response

An active gas-gap heat switch may significantly reduce the time required to transition between the open and closed states, reduce the heat require to warm the getter, and reduce the heat that leaks from the getter to the switch body. A thermal interface at one end of the active gas-gap heat switch may include a plurality of fins. A getter assembly may be hermetically attached to the thermal interface and a containment tube may surround and house the plurality of fins.

Shirron, Peter J.↗
NASA NTRS2020

High Performance Thermal Switch for Lunar and Planetary Surface Extreme Environments

This paper describes a high performance thermal switch for lunar/planetary extreme environments. This device has been given the name Reverse-Operation DTE Thermal Switch (or ROD-TSW). Two different prototypes were designed, built, and tested. Their basis of operation is the mating/de-mating of parallel flat metal surfaces driven by the differential thermal expansion (DTE) between mid-to-high CTE metal/polymer or metal-only end-pieces and a low CTE, low thermal conductivity (k) metal/polymer support rod. The requirements were to be fully ON above 300 K and fully OFF below 260 K. A series of four tests were carried out to verify/qualify the prototypes. In the first (non-vacuum) test, the thermal switches were cooled with freeze-spray and the non-conductive rod in the OFF thermal path allowed electrical resistance to confirm the 273 K as-designed ON/OFF actuation temperature. In the second (vacuum) test, a calibrated Q-meter was used, which indicated 5 W/K ON, 0.002 W/K OFF conductance (2500:1 ON/OFF ratio). To increase readiness to TRL6, a vibration test with pre/post thermal cycling followed by a 36-day test in a relevant environment were also carried out. This paper describes the development program and on-going related work at JPL.

Bugby, David C↗
NASA NTRS2020

High Performance Thermal Switch for Lunar and Planetary Surface Extreme Environments

This paper describes a high performance thermal switch for lunar/planetary extreme environments. This device has been given the name Reverse-Operation DTE Thermal Switch (or ROD-TSW). Two different prototypes were designed, built, and tested. Their basis of operation is the mating/de-mating of parallel flat metal surfaces driven by the differential thermal expansion (DTE) between mid-to-high CTE metal/polymer or metal-only end-pieces and a low CTE, low thermal conductivity (k) metal/polymer support rod. The requirements were to be fully ON above 300 K and fully OFF below 260 K. A series of four tests were carried out to verify/qualify the prototypes. In the first (non-vacuum) test, the thermal switches were cooled with freeze-spray and the non-conductive rod in the OFF thermal path allowed electrical resistance to confirm the 273 K as-designed ON/OFF actuation temperature. In the second (vacuum) test, a calibrated Q-meter was used, which indicated 5 W/K ON, 0.002 W/K OFF conductance (2500:1 ON/OFF ratio). To increase readiness to TRL6, a vibration test with pre/post thermal cycling followed by a 36-day test in a relevant environment were also carried out. This paper describes the development program and on-going related work at JPL.

Bugby, David C.↗
DOE OSTI2015

Electronic devices containing switchably conductive silicon oxides as a switching element and methods for production and use thereof

In various embodiments, electronic devices containing switchably conductive silicon oxide as a switching element are described herein. The electronic devices are two-terminal devices containing a first electrical contact and a second electrical contact in which at least one of the first electrical contact or the second electrical contact is deposed on a substrate to define a gap region therebetween. A switching layer containing a switchably conductive silicon oxide resides in the gap region between the first electrical contact and the second electrical contact. The electronic devices exhibit hysteretic current versus voltage properties, enabling their use in switching and memory applications. Methods for configuring, operating and constructing the electronic devices are also presented herein.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Capacitive microelectromechanical switches with dynamic soft-landing

A microelectromechanical system (MEMS)-based electrical switch. The electrical switch includes a moveable electrode, a dielectric layer positioned adjacent the moveable electrode on a first side of the dielectric layer and spaced apart from the moveable electrode when the moveable electrode is in an inactivated position and in contact with the moveable electrode when the moveable electrode is in an activated position, and a substrate attached to the dielectric layer on a second side opposite to the first side, the moveable electrode is configured to brake prior to coming in contact with the dielectric layer when the moveable electrode is switched between the inactivated state and the activated state.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2015

Photoconductive switch package

A photoconductive switch is formed of a substrate that has a central portion of SiC or other photoconductive material and an outer portion of cvd-diamond or other suitable material surrounding the central portion. Conducting electrodes are formed on opposed sides of the substrate, with the electrodes extending beyond the central portion and the edges of the electrodes lying over the outer portion. Thus any high electric fields produced at the edges of the electrodes lie outside of and do not affect the central portion, which is the active switching element. Light is transmitted through the outer portion to the central portion to actuate the switch.

14 SOLAR ENERGY↗
DOE OSTI2016

Hybrid zero-voltage switching (ZVS) control for power inverters

A power inverter combination includes a half-bridge power inverter including first and second semiconductor power switches receiving input power having an intermediate node therebetween providing an inductor current through an inductor. A controller includes input comparison circuitry receiving the inductor current having outputs coupled to first inputs of pulse width modulation (PWM) generation circuitry, and a predictive control block having an output coupled to second inputs of the PWM generation circuitry. The predictive control block is coupled to receive a measure of Vin and an output voltage at a grid connection point. A memory stores a current control algorithm configured for resetting a PWM period for a switching signal applied to control nodes of the first and second power switch whenever the inductor current reaches a predetermined upper limit or a predetermined lower limit.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Capacitive microelectromechanical switches with dynamic soft-landing

A microelectromechanical system (MEMS)-based electrical switch. The electrical switch includes a moveable electrode, a dielectric layer positioned adjacent the moveable electrode on a first side of the dielectric layer and spaced apart from the moveable electrode when the moveable electrode is in an inactivated position and in contact with the moveable electrode when the moveable electrode is in an activated position, and a substrate attached to the dielectric layer on a second side opposite to the first side, the moveable electrode is configured to brake prior to coming in contact with the dielectric layer when the moveable electrode is switched between the inactivated state and the activated state.

42 ENGINEERING↗
DOE OSTI2016

A 600 VOLT MULTI-STAGE, HIGH REPETITION RATE GAN FET SWITCH

Using recently available GaN FETs, a 600 Volt three- stage, multi-FET switch has been developed having 2 nanosecond rise time driving a 200 Ohm load with the potential of approaching 30 MHz average switching rates. Possible applications include driving particle beam choppers kicking bunch-by-bunch and beam deflectors where the rise time needs to be custom tailored. This paper reports on the engineering issues addressed, the design approach taken and some performance results of this switch.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

High-voltage, high-current, solid-state closing switch

A high-voltage, high-current, solid-state closing switch uses a field-effect transistor (e.g., a MOSFET) to trigger a high-voltage stack of thyristors. The switch can have a high hold-off voltage, high current carrying capacity, and high time-rate-of-change of current, di/dt. The fast closing switch can be used in pulsed power applications.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Radio frequency-assisted fast superconducting switch

A radio frequency-assisted fast superconducting switch is described. A superconductor is closely coupled to a radio frequency (RF) coil. To turn the switch "off," i.e., to induce a transition to the normal, resistive state in the superconductor, a voltage burst is applied to the RF coil. This voltage burst is sufficient to induce a current in the coupled superconductor. The combination of the induced current with any other direct current flowing through the superconductor is sufficient to exceed the critical current of the superconductor at the operating temperature, inducing a transition to the normal, resistive state. A by-pass MOSFET may be configured in parallel with the superconductor to act as a current shunt, allowing the voltage across the superconductor to drop below a certain value, at which time the superconductor undergoes a transition to the superconducting state and the switch is reset.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

High frequency modulation circuits based on photoconductive wide bandgap switches

Methods, systems, and devices for high voltage and/or high frequency modulation. In one aspect, an optoelectronic modulation system includes an array of two or more photoconductive switch units each including a wide bandgap photoconductive material coupled between a first electrode and a second electrode, a light source optically coupled to the WBGP material of each photoconductive switch unit via a light path, in which the light path splits into multiple light paths to optically interface with each WBGP material, such that a time delay of emitted light exists along each subsequent split light path, and in which the WBGP material conducts an electrical signal when a light signal is transmitted to the WBGP material, and an output to transmit the electrical signal conducted by each photoconductive switch unit. The time delay of the photons emitted through the light path is substantially equivalent to the time delay of the electrical signal.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Trends in SiC MOSFET Threshold Voltage and ON-Resistance Measurements from Thermal Cycling and Electrical Switching Stresses: Preprint

Integrating SiC power MOSFETs is very attractive for advancing power electronic systems, yet the system reliability with new devices remains in question. This work presents two accelerated test experiments to further investigate the packaging and semiconductor failures of a TO-247 SiC MOSFET. First, a variation on power cycling experiments -- switching cycling -- is introduced. Traditional power cycling experiments utilize conduction losses to self-heat the device where a large temperature swing causes degradation at the packaging level. However, by decreasing the on-time such that the device only turns on and immediately turns off, the temperature swing is decreased and the semiconductor itself is degraded. This work shows experimental device degradation caused by continuous switching events - switching cycling, at 90% of the device's breakdown voltage. Second, thermal cycling experiments were conducted between -40 degrees C and 175 degrees C to observe degradation in the mechanical packaging of the device. Experimentally-measured changes in threshold voltage and ON-resistance are recorded in both experiments and compared. These results also illustrate the spectrum between device and package degradation from accelerated test methods.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

Gas tube-switched flexible alternating current transmission system

A var compensator circuit is provided. The var compensator circuit includes a gas tube switch and a reactive impedance. The gas tube switch is configured to be coupled to a transmission line. The transmission line is configured to deliver real power and reactive power to a load at an alternating current (AC) line voltage. The reactive impedance is configured to be coupled to the transmission line at the AC line voltage through the gas tube switch. The reactive impedance is configured to modify the reactive power configured to be delivered to the load.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Low voltage drop, cross-field, gas switch and method of operation

A gas switch includes an anode and a cathode spaced apart from the anode, wherein the cathode includes a conduction surface. The gas switch also includes a plurality of magnets arranged to generate a magnetic field that defines an annular path over a portion of the conduction surface at a radial distance from a switch axis, and a control grid positioned between the anode and the cathode. In operation, the control grid is arranged to establish a conducting plasma between the anode and the cathode, wherein, in the presence of the conducting plasma, a voltage drop between the anode and the cathode is less than 150 volts, and wherein the conducting plasma forms a cathode spot that circles the annular path.

42 ENGINEERING↗
DOE OSTI2019

Low sputtering, cross-field, gas switch and method of operation

A gas switch includes a gas-tight housing containing an ionizable gas, an anode disposed within the gas-tight housing, and a cathode disposed within the gas-tight housing, where the cathode includes a conduction surface. The gas switch also includes a control grid positioned between the anode and the cathode, where the control grid is arranged to receive a bias voltage to establish a conducting plasma between the anode and the cathode. In addition, the gas switch includes a plurality of magnets selectively arranged to generate a magnetic field proximate the conduction surface that reduces the kinetic energy of charged particles striking the conduction surface and raises the conduction current density at the cathode surface to technically useful levels.

42 ENGINEERING↗
DOE OSTI2020

High voltage, cross-field, gas switch and method of operation

A high voltage gas switch includes a gas-tight housing containing an ionizable gas at a preselected gas pressure. The gas switch includes a gas-tight housing containing an ionizable gas at a gas pressure selected based upon a Paschen curve for the ionizable gas, where the Paschen curve plots breakdown voltages of the ionizable gas as a function of gas pressure multiplied by grid-to-anode distance, and where values of gas pressure multiplied by grid-to-anode distance increase over at least a portion of the Paschen curve in conjunction with increasing breakdown voltages. The gas switch also includes an anode disposed within the gas-tight housing, a cathode disposed within the gas-tight housing, and a control grid positioned between the anode and the cathode, where the control grid is spaced apart from the anode by a grid-to-anode distance selected based upon a desired operating voltage.

42 ENGINEERING↗
DOE OSTI2019

Final Conversion of the Spallation Neutron Source Extraction Kicker Pulse Forming Network to a High Voltage Solid-State Switch

The Spallation Neutron Source (SNS) extraction kicker 60Hz pulsed system uses 14 Blumlein pulse-forming network (PFN) modulators that require timing synchronization with stable rise times. A replacement design has been investigated and the kickers have been converted over to use a solid-state switch design, eliminating the lifetime and stability issues associated with thyratrons and subsequent maintenance costs. All kickers have been converted, preventing thyratron jitter from impacting the beam performance and allowing higher-precision target impact. This paper discusses the completion of the conversion of the high-voltage switch from a thyratron to a solid-state switch with improved stability of the extraction system and associated accelerator beam stability.

Morris, B↗