Contactless Rotary Electrical Couplings
- Thursday, 18 January 2007
Efficient inductive couplings are used in place of slip rings.
Rotary electrical couplings based on induction (transformer action) rather than conduction between rotating and stationary circuitry have been invented. These couplings provide an alternative to slip rings and contact brushes.
Mechanical imperfections of slip-ring and brush contact surfaces and/or dust particles trapped between these surfaces tend to cause momentary interruptions in electrical contact and thereby give rise to electrical noise. This source of noise can be eliminated in the inductive rotary couplings because no direct contact is necessary for transformer action.
The transformer core partly resembles the core of a common type of conventional power transformer; it includes an inner part framed in a generally rectangular outer part. However, unlike the core of a conventional power transformer, this core includes a clearance hole for the rotating shaft, and the inner core is a round cylinder (instead of a rectangular solid) with the clearance hole lying along its axis. Moreover, there is a gap at one end of the inner core to provide clearance for a clamp that attaches the rotating coil to the shaft. Both coils are annular, with inner radii and outer radii to fit the recess between the inner and outer core. To provide clearance for rotation, the inner radius of the stationary coil must be made somewhat greater than the outer radius of the inner part of the core.
This work was done by Hiroyuki Kumagai of Aerospace Computing, Inc., for Ames Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Computers/Electronics category.
This invention has been patented by NASA (U.S. Patent No. 5,691,687). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Ames Research Center; (650) 604-5104. Refer to ARC-12072.
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Contactless Rotary Electrical Couplings (reference ARC-12072) is currently available for download from the TSP library.
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