Inductrack

Inductrack is a completely passive, fail-safe magnetic levitation system, using only unpowered loops of wire in the track and permanent magnets (arranged into Halbach arrays) on the vehicle to achieve magnetic levitation. The track can be in one of two configurations, a "ladder track" and a "laminated track". The ladder track is made of unpowered Litz wire cables, and the laminated track is made out of stacked copper or aluminum sheets.

There are two designs: the Inductrack I, which is optimized for high speed operation, and the Inductrack II, which is more efficient at lower speeds.

Description

Inductrack, or Inductrak, was invented by a team of scientists at Lawrence Livermore National Laboratory, headed by physicist Richard F. Post, for use in maglev trains. [http://www.llnl.gov/str/Post.html "A New Approach for Magnetically Levitating Trains — and Rockets] "] [ [http://www.skytran.net/press/sciam01.htm Richard F. Post, "MagLev: A New Approach", "Scientific American" January, 2000.] ] At constant velocity, the only power required is to push the train forward against air and electromagnetic drag. Above a minimum speed as the velocity of the train increases the levitation gap increases, but the lift force is constant.

Its name comes from the word "inductance" or "inductor"; an electrical device made from loops of wire. As the magnet array (with alternating magnetic field orientations) passes over the loops of wire, the variations in the field induces a voltage in the coils of the track. The inductance of the track causes the current to coincide with the peaks of the field of the magnet array. The current creates its own magnetic field which repels the permanent magnets.

When neodymium–iron–boron permanent magnets are used, levitation is achieved at low speeds, allowing it to lift 50 times the magnet weight. The test model levitated at speeds above 22 mph, but Richard Post believes that on real tracks, levitation could be achieved at "as little as 1 to 2 mph". Below the transition speed, the magnetic drag increases as the vehicle's speed increases and approaches the transition speed, but above this transition speed, the magnetic drag decreases inversely with the vehicle's speed [ [http://www.popularmechanics.com/science/transportation/1289196.html "Track To The Future: Maglev Trains On Permanent Magnets"] — Scott R. Gourley — Popular Mechanics] , reaching for example, a lift to drag ratio of 200:1 at 500 km/h, which is far higher than any aircraft. [ [http://www.skytran.net/press/sciam03.htm In "MagLev: A New Approach", above, section on "The Issue of Efficiency"] ] .

The Inductrack II variation uses two Halbach arrays, one above and one below the track to double the levitating magnetic field without substantially increasing the weight or footprint area of the Halbach arrays, while having lower drag forces at low speeds. [ [http://gcep.stanford.edu/pdfs/ChEHeXOTnf3dHH5qjYRXMA/09_Post_10_11_trans.pdf "Toward More Efficient Transport: The Inductrack Maglev System"] — Presented by Richard F. Post, 10 October 2005]

Several maglev railroad proposals are based upon Inductrack technology. The U.S. National Aeronautics and Space Administration (NASA) is also considering Inductrack technology for launching rockets.

General Atomics is currently developing Inductrak technology in cooperation with multiple research partners.

See also

* SkyTran — a personal rapid transit design that proposes to use Inductrack technology.

References

External links

* [http://www.ga.com/atg/EMS/urbanmaglev.php General Atomics, Urban Maglev]
* [http://www.llnl.gov/str/Post.html Lawrence Livermore National Laboratories]
* [http://www.llnl.gov/str/October04/Post.html S&TR article on Inductrack]
* [http://www.askmar.com/Inductrack/inductrack.html Media articles and technical reports on Inductrack, 1998 to 2005]
* [http://ccdc.mee.ucsb.edu/pdf/ccdc-05-0930.pdf Discrete track electrodynamic maglev modelling] This article has an overview of the history and current status of magnetic levitation
* [http://www.portoflosangeles.org/DOC/REPORT_ECCO_102706.pdf Electric Cargo Conveyor System with Inductrack, General Atomics, Final Report, October 2006]

Patents

* [http://www.freepatentsonline.com/5722326.html US patent 5722326: Magnetic levitation system for moving objects]
* [http://www.freepatentsonline.com/6664880.html US patent 6664880: Inductrack magnet configuration]
* [http://www.freepatentsonline.com/6758146.html US patent 6758146: Laminated track design for Inductrack maglev systems]
* [http://www.freepatentsonline.com/20050204948.html US patent application 20050204948: Inductrack configuration]