Contactless Magnetic Slip Ring

The NASA Ames Research Center has developed an innovative method for transmitting power or data between stationary and rotating frames without the use of conventional slip rings or brushes. There is no physical contact between the rotating and fixed parts of the apparatus. In this new device, inductive components are used to provide a reliable and efficient transfer of electrical power across the rotational boundary. The inductive components form a contactless magnetic slip ring that functions like a power transformer, but makes use of a rotating coil to accommodate the equipment's rotation. The slip ring transfers a constant level of electrical power regardless of the position of the rotating coil. The device includes bearings to support the rotating components, such as air bearings or mechanical bearings, depending on mechanical load and rotational speed factors. Conventional slip rings suffer wear, can cause unwanted arcing, and are prone to damage from dirt in field conditions. This device eliminates arcing and is inherently resistant to dirty environments because of lack of rubbing contacts. There are no exposed conductors, and the absence of sparks or arcing makes the device safe in the presence of flammable or explosive gases.

The technology consists of an inductive device serving as a magnetic slip ring with primary and secondary coils, one of which can be rotated with respect to the other. The two coils are coupled by outer and inner cores constructed from layered silicon steel to minimize eddy currents and heat loss. This arrangement achieves reliable and highly efficient transfer of electrical power between the stationary and rotating frames.

Potential Commercial Uses

• Can replace conventional brush/armature assembly in electrical motors and alternators.
  
• Can be used to transfer power to rotating devices such as helicopter rotors, centrifuges, etc.
  
• Appropriate for commercial applications ranging from simple toys to sophisticated medical equipment.
  
• Particularly well suited for use where explosive gas may be present since there is no risk of sparks.

Benefits

• Contactless: Unlike conventional slip rings, this invention has no mechanical contact between components to degrade the operational life of the device.
  
• Free of noise, no signal loss: The magnetic slip ring transfers power that is free of noise with no loss of electrical signal quality.
  
• Insulation not air dependent: Unlike mechanical slip rings which rely on the presence of air for insulation, this invention can be used in a vacuum or at high altitudes without any requirement for additional insulation or pressurization.
  
• Little or no maintenance required: Since the moving surfaces do not contact each other, it requires little or no maintenance compared with conventional slip rings which require cleaning to maintain performance.
  
• No possibility of sparks: This design has no electro-mechanical contact or exposed electrodes, eliminating the possibility of generating sparks. It can be used in an environment where explosive gases are present without concern for sealing. RF noise that causes signal interference is also eliminated.
  
• Reliability: The structure is relatively simple and durable. Unlike a conventional armature / brush assembly, the design has no consumable parts with limited life expectancy.
  
• Analog and Digital signal transmission capability: In addition to the power transmission capability, the inductive device can also transfer electrical signals of low frequency. Data rates depend on the inductance of the device.
  
• Lower long-term costs: By eliminating the cost of sealing and pressurizing the armature / brush assembly for high altitude application and reducing the cost of maintenance and replacement parts, the long-term savings can more than offset the higher initial cost.
  
• Easily Manufactured: The contactless magnetic slip ring is such as simple device that any U.S. company with light manufacturing capabilities should be able to set up a mass production facility. The manufacturers of power transformers, generators, alternators or motors may already have the equipment and materials needed for production.

Options for Commercialization

NASA Ames currently seeks to license the Contactless Magnetic Slip Ring to U.S. companies interested in manufacturing the device for commercial applications. The Contactless Magnetic Slip Ring was developed by Dr. Hiroyuki Kumagai, Aerospace Computing, Inc., NASA Ames Research Center. Patent Pending.

Contact

NASA Ames Research Center
Commercial Technology Office
Mail Stop 202A-3
Moffett Field, CA 94035-1000
Phone: 650-604-4595

http://ctoserver.arc.nasa.gov:80/TechOpps/slipring.html

Key Words

Contactless Magnetic Slip Ring, Electric Power Transfer, Power Coupling, Signal Transmission