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Results for “Homopolar Machines”

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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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Field Emission Current Transfer for Homopolar Machines

With the increasing electrification of transportation, the need for high power density electric machines is higher than ever. The required specific power for the more demanding applications, such as airplane propulsion, is over 20 kW/kg for multi-megawatt range power levels. Fully superconducting synchronous machines could reach the required performance, but significant challenges remain to be addressed such as AC losses management and rotating cryogenics implementation. Homopolar machines constitute the simplest electro-mechanical conversion systems possible, however the difficulty of establishing reliable and efficient low voltage, high DC current transfer from a stationary to a rotating system has prevented homopolar machines from competing with AC electrical machines. While sliding contacts or liquid metal contacts are feasible, they lead to high losses, high maintenance requirements and the use of environmentally unfriendly materials. We investigated field emission current transfer as an alternative to sliding contacts. We have demonstrated field emission current transfer in vacuum between a copper electrode and carbon nanotubes and diamond pyramids to evaluate the feasibility of contact-free current transfer for homopolar machines. The initial field emission testing was successfully demonstrated with current densities in the 10 mA/cm 2 range. The initial experiments validated the concept and supported the development of a roadmap for the development of contactless current transfer for homopolar machines, helped understand the limitations of the current test system and identify the key parameters that will lead to better performance.

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS1984

Westinghouse programs in pulsed homopolar power supplies

This document details Westinghouse's ongoing study of homopolar machines since 1929 with the major effort occurring in the early 1970's to the present. The effort has enabled Westinghouse to develop expertise in the technology required for the design, fabrication and testing of such machines. This includes electrical design, electromagnetic analysis, current collection, mechanical design, advanced cooling, stress analysis, transient rotor performance, bearing analysis and seal technology. Westinghouse is using this capability to explore the use of homopolar machines as pulsed power supplies for future systems in both military and commercial applications.

Litz, D. C.↗
NASA NTRS1981

A study pertaining to inertial energy storage machine designs for space applications

The preliminary design of a counterrotating fast discharge homopolar generator (HPG) and a counterrotating active rotary flux compressor (CARFC) for space application is reported. The HPG is a counterrotating spool-type homopolar with superconducting field coil excitation. It delivers a 20-ms, 145-kJ pulse to a magnetoplasmahydrodynamic thruster. The peak output current is 42.7 kA at 240 V. After 20 ms the current is 29.7 kA at 167 V. The CARFC delivers ten 50-kJ, 250 microsecond pulses at 50-ms interval to six Xenon flash lamps pumping an Nd glass laser. The flux compressor is counterrotating for torque compensation. Current is started in the machine with a 5-kV, 5-kJ pulse-charged capacitor. Both designs were based upon demonstrated technology. The sensitivity of the designs to technology that may be available in five to ten years was determined.

Zowarka, R. C.↗
NASA NTRS1996

Magnetic Bearing

AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

Source record↗
NASA NTRS1980

A study of the applicability/compatibility of inertial energy storage systems to future space missions

The applicability/compatibility of inertial energy storage systems like the homopolar generator (HPG) and the compensated pulsed alternator (CPA) to future space missions is explored. Areas of CPA and HPG design requiring development for space applications are identified. The manner in which acceptance parameters of the CPA and HPG scale with operating parameters of the machines are explored and the types of electrical loads which are compatible with the CPA and HPG are examined. Potential applications including the magnetoplasmadynamic (MPD) thruster, pulsed data transmission, laser ranging, welding and electromagnetic space launch are discussed.

Weldon, W. F.↗
NASA NTRS1976

Insulation end life determination for completed form-wound generators

Tests were conducted to predict remaining electrical insulation life of a polyimide-epoxy insulated 60 kW form-wound homopolar inductor generator following completion of 23,130 hours of turbo-generator endurance tests. The generator stator was sectioned to provide five sections, designated statorettes, and to permit 33 coil dielectric measurements on each section. Thermal aging tests were conducted on each section at select elevated temperatures to establish an Arrhenius life-temperature plot for end-life prediction and product or application use. The statorette fabrication technique is considered novel and provides means to establish insulation life-temperature profiles on completed electromagnetic components of rotating machines.

Penn, W. B.↗
NASA NTRS2001

Low loss pole configuration for multi-pole homopolar magnetic bearings

A new pole configuration for multi-pole homopolar bearings proposed in this invention reduces rotational losses caused by eddy-currents generated when non-uniform flux distributions exist along the rotor surfaces. The new homopolar magnetic bearing includes a stator with reduced pole-to-pole and exhibits a much more uniform rotor flux than with large pole-to-pole gaps. A pole feature called a pole-link is incorporated into the low-loss poles to provide a uniform pole-to-pole gap and a controlled path for pole-to-pole flux. In order to implement the low-loss pole configuration of magnetic bearings with small pole-to-pole gaps, a new stator configuration was developed to facilitate installation of coil windings. The stator was divided into sector shaped pieces, as many pieces as there are poles. Each sector-shaped pole-piece can be wound on a standard coil winding machine, and it is practical to wind precision layer wound coils. To achieve maximum actuation efficiency, it is desirable to use all the available space for the coil formed by the natural geometric configuration. Then, the coils can be wound in a tapered shape. After winding, the sectored-pole-pieces are installed into and fastened by bonding or other means, to a ring of material which encloses the sectored-pole-pieces, forming a complete stator.

Blumenstock, Kenneth A.↗