Search NASA⌕ Search

SEARCH · Search NASA

Results for “MAGNETIC CORES”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Paralleling power MOSFETs in their active region: Extended range of passively forced current sharing

A simple passive circuit that improves current balance in parallelled power MOSFETs that are not precisely matched and that are operated in their active region from a common gate drive are exhibited. A nonlinear circuit consisting of diodes and resistors generates the differential gate potential required to correct for unbalance while maintaining low losses over a range of current. Also application of a thin tape wound magnetic core to effect dynamic current balance is reviewed, and a simple theory is presented showing that for operation in the active region the branch currents tend to revert to their normal unbalanced values even if the core is not driven into saturation. Results of several comparative experiments are given.

Niedra, Janis M.↗
NASA NTRS1991

Rugged Direct-Current Transducer

Direct-current transducer withstands thermal and mechanical shocks. Operates from single, nominally 15-V power supply and nearly insensitive to both large variations in temperature and variations of as much as plus or minus 5 V in supply voltage. Its output voltage highly linear function of sensed current, with full-scale value of about 3 Vdc and offset of about 0.1 Vdc at 0 sensed current. Ruggedness of transducer due in large part to novel magnetic core, machined from solid block of nickel/iron high-permeability, low-hysteresis alloy.

Mclyman, W. T.↗
NASA NTRS1992

The large-angle magnetic suspension test fixture

As part of a NASA effort to develop the technology and techniques required to demonstrate the magnetic suspension of objects over wide ranges of attitudes, a small-scale demonstration project was undertaken. The objectives here are to suspend a cylindrical element containing a permanent magnet core, to demonstrate stability and control in five degrees-of-freedom, and to permit controlled rotation of the model in one degree-of-freedom over the full range of 360 deg. Further constraints are that all suspension and control electromagnets are to be behind a flat plane, located some distance from the model. Since this is a ground-based experiment and in order to maintain generality, the plane is chosen to be horizontal with the model levitated above the plane by repulsive forces.

Britcher, Colin P.↗
NASA NTRS1992

Electromagnetic attachment mechanism

An electromagnetic attachment mechanism is disclosed for use as an end effector of a remote manipulator system. A pair of electromagnets, each with a U-shaped magnetic core with a pull-in coil and two holding coils, are mounted by a spring suspension system on a base plate of the mechanism housing with end pole pieces adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate of a grapple fixture affixed to a target object. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery backup is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary source. A centerline mounted camera and video monitor are used in cooperation with a target pattern on the reflective surface of the strike plate to effect targeting and alignment.

Monford, Leo G., Jr.↗
NASA NTRS1993

Direct-Current Monitor With Flux-Reset Transformer Coupling

Circuit measures constant or slowly-varying unidirectional electrical current using flux-reset transformer coupling. Measurement nonintrusive in sense that no need for direct contact with wire that carries load current to be measured, and no need to install series resistive element in load-current path. Toroidal magnetic core wrapped with coil of wire placed around load-current-carrying wire, acts as transformer core, load-current-carrying wire acts as primary winding of transformer, and coil wrapped on core acts as secondary winding.

Canter, Stanley↗
NASA NTRS1991

Optical position measurement for a Large Gap Magnetic Suspension System

This paper describes the design of an optical position measurement system which is being built as part of the NASA Langley Large Gap Magnetic Suspension System (LGMSS). The LGMSS is a five degree-of-freedom, large-gap magnetic suspension system which is being built for Langley Research Center as part of the Advanced Controls Test Facility (ACTF). The LGMSS consists of a planar array of electromagnets which levitate and position a cylindrically shaped model containing a permanent magnet core. The optical position measurement system provides information on the location and orientation of the model to the LGMSS control system to stabilize levitation of the model.

Welch, Sharon S.↗
NASA NTRS1994

Optical position measurement for a large gap magnetic suspension system: Design and performance analysis

An optical measurement system (OMS) has been designed and tested for a large gap magnetic suspension system (LGMSS). The LGMSS will be used to study control laws for magnetic suspension systems for vibration isolation and pointing applications. The LGMSS features six degrees of freedom and consists of a planar array of electromagnets that levitate and position a cylindrical element containing a permanent magnet core. The OMS provides information on the location and orientation of the element to the LGMSS control system to stabilize suspension. The hardware design of this optical sensing system and the tracking algorithms are presented. The results of analyses and experiments are presented that define the accuracy limits of the optical sensing system and that quantify the errors in position estimation.

Welch, Sharon S.↗
NASA NTRS1996

A Digital Control Algorithm for Magnetic Suspension Systems

An ongoing program exists to investigate and develop magnetic suspension technologies and modelling techniques at NASA Langley Research Center. Presently, there is a laboratory-scale large air-gap suspension system capable of five degree-of-freedom (DOF) control that is operational and a six DOF system that is under development. Those systems levitate a cylindrical element containing a permanent magnet core above a planar array of electromagnets, which are used for levitation and control purposes. In order to evaluate various control approaches with those systems, the Generic Real-Time State-Space Controller (GRTSSC) software package was developed. That control software package allows the user to implement multiple control methods and allows for varied input/output commands. The development of the control algorithm is presented. The desired functionality of the software is discussed, including the ability to inject noise on sensor inputs and/or actuator outputs. Various limitations, common issues, and trade-offs are discussed including data format precision; the drawbacks of using either Direct Memory Access (DMA), interrupts, or program control techniques for data acquisition; and platform dependent concerns related to the portability of the software, such as memory addressing formats. Efforts to minimize overall controller loop-rate and a comparison of achievable controller sample rates are discussed. The implementation of a modular code structure is presented. The format for the controller input data file and the noise information file is presented. Controller input vector information is available for post-processing by mathematical analysis software such as MATLAB1.

Britton, Thomas C.↗
NASA NTRS2006

A Bearingless Switched-Reluctance Motor for High Specific Power Applications

A 12-8 switched-reluctance motor (SRM) is studied in bearingless (or self-levitated) operation with coil currents limited to the linear region to avoid magnetic saturation. The required motoring and levitating currents are summed and go into a single motor coil per pole to obtain the highest power output of the motor by having more space for motor coil winding. Two controllers are investigated for the bearingless SRM operation. First, a model-based controller using the radial force, which is adjusted by a factor derived from finite element analysis, is presented. Then a simple and practical observation-based controller using a PD (proportional-derivative) control algorithm is presented. Both controllers were experimentally demonstrated to 6500 rpm. This paper reports the initial efforts toward eventual self levitation of a SRM operating into strong magnetic core saturation at liquid nitrogen temperature.

Choi, Benjamin B.↗
NASA NTRS1995

Grapple fixture for use with electromagnetic attachment mechanism

An electromagnetic attachment mechanism for use as an end effector of a remote manipulator system. A pair of electromagnets 15A,15B, each with a U-shaped magnetic core with a pull-in coil 34 and two holding coils 35,36 are mounted by a spring suspension system 38,47 on a base plate 25 of the mechanism housing 30 with end pole pieces 21,22 adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate 65 of a grapple fixture 20 affixed to a target object 14. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery back-up 89A,89B is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary power source. A centerline mounted camera 31 and video monitor 70 are used in cooperation with a target pattern 19 on the reflective surface 67 of the strike plate to effect targeting and alignment.

Monford, Jr., Leo G.↗
NASA NTRS2010

Memories and NASA Spacecraft: A Description of Memories, Radiation Failure Modes, and System Design Considerations

As NASA has evolved it's usage of spaceflight computing, memory applications have followed as well. In this slide presentation, the history of NASA's memories from magnetic core and tape recorders to current semiconductor approaches is discussed. There is a brief description of current functional memory usage in NASA space systems followed by a description of potential radiation-induced failure modes along with considerations for reliable system design.

LaBel, Kenneth A.↗
NASA NTRS2011

Miniature high speed compressor having embedded permanent magnet motor

A high speed centrifugal compressor for compressing fluids includes a permanent magnet synchronous motor (PMSM) having a hollow shaft, the being supported on its ends by ball bearing supports. A permanent magnet core is embedded inside the shaft. A stator with a winding is located radially outward of the shaft. The PMSM includes a rotor including at least one impeller secured to the shaft or integrated with the shaft as a single piece. The rotor is a high rigidity rotor providing a bending mode speed of at least 100,000 RPM which advantageously permits implementation of relatively low-cost ball bearing supports.

Zhou, Lei↗
NASA NTRS2011

Co-Flow Hollow Cathode Technology

Hall thrusters utilize identical hollow cathode technology as ion thrusters, yet must operate at much higher mass flow rates in order to efficiently couple to the bulk plasma discharge. Higher flow rates are necessary in order to provide enough neutral collisions to transport electrons across magnetic fields so that they can reach the discharge. This higher flow rate, however, has potential life-limiting implications for the operation of the cathode. A solution to the problem involves splitting the mass flow into the hollow cathode into two streams, the internal and external flows. The internal flow is fixed and set such that the neutral pressure in the cathode allows for a high utilization of the emitter surface area. The external flow is variable depending on the flow rate through the anode of the Hall thruster, but also has a minimum in order to suppress high-energy ion generation. In the co-flow hollow cathode, the cathode assembly is mounted on thruster centerline, inside the inner magnetic core of the thruster. An annular gas plenum is placed at the base of the cathode and propellant is fed throughout to produce an azimuthally symmetric flow of gas that evenly expands around the cathode keeper. This configuration maximizes propellant utilization and is not subject to erosion processes. External gas feeds have been considered in the past for ion thruster applications, but usually in the context of eliminating high energy ion production. This approach is adapted specifically for the Hall thruster and exploits the geometry of a Hall thruster to feed and focus the external flow without introducing significant new complexity to the thruster design.

Hofer, Richard R.↗
NASA NTRS2012

Discontinuous Mode Power Supply

A document discusses the changes made to a standard push-pull inverter circuit to avoid saturation effects in the main inverter power supply. Typically, in a standard push-pull arrangement, the unsymmetrical primary excitation causes variations in the volt second integral of each half of the excitation cycle that could lead to the establishment of DC flux density in the magnetic core, which could eventually cause saturation of the main inverter transformer. The relocation of the filter reactor normally placed across the output of the power supply solves this problem. The filter reactor was placed in series with the primary circuit of the main inverter transformer, and is presented as impedance against the sudden changes on the input current. The reactor averaged the input current in the primary circuit, avoiding saturation of the main inverter transformer. Since the implementation of the described change, the above problem has not reoccurred, and failures in the main power transistors have been avoided.

Lagadinos, John↗
NASA NTRS2015

Feasibility of Dynamic Stability Measurements of Planetary Entry Capsules Using MSBS

The feasibility of conducting dynamic stability testing of planetary entry capsules at low supersonic Mach numbers using a Magnetic Suspension and Balance System (MSBS) is reviewed. The proposed approach would employ a spherical magnetic core, exert control in three degrees-of-freedom (i.e. x, y, z translations) and allow the model to freely rotate in pitch, yaw, and roll. A proof-of-concept system using an existing MSBS electromagnet array in a subsonic wind tunnel is described, with future potential for development of a new system for a supersonic wind tunnel.

Britcher, Colin↗
NASA NTRS2010

Memory Overview - Technologies and Needs

As NASA has evolved it's usage of spaceflight computing, memory applications have followed as well. In this talk, we will discuss the history of NASA's memories from magnetic core and tape recorders to current semiconductor approaches. We will briefly describe current functional memory usage in NASA space systems followed by a description of potential radiation-induced failure modes along with considerations for reliable system design.

LaBel, Kenneth A.↗
DOE OSTI2018

Electrical machine cooling structure

A stator assembly that includes a graphite sheet-like element that has fold(s) so as to define at least two planar sections. The face of one of the planar section abuts a surface of a heat generating location(s) of the stator assembly and a face of another planar section abuts one the tooth or the slot bottom of the stator assembly. Also, a subassembly that includes an electrical machine stator assembly that includes a sheet-like element of a material having high thermal conductivity, wherein a portion of the element abuts the end winding(s) such that the sheet-like element conducts heat to the magnetic core, the stator housing, and/or a winding heat conduction element.

42 ENGINEERING↗
DOE OSTI2020

Magnetically-recoverable catalysts for depolymerization

The present invention relates, in part, to methods for depolymerizing a polymer, in which the method includes use of a magnetic catalyst. The magnetic catalyst can include, e.g., a ore-shell particle, such as a particle having a magnetic core and a shell including a metal-organic framework.

36 MATERIALS SCIENCE↗