05-04-2012, 11:39 AM
The Inductrack: A Home-Grown Maglev System for our Nation
The Inductrack A Home-Grown Maglev System for our Nation.ppt (Size: 6.25 MB / Downloads: 260)
There are many reasons why magnetically levitated trains could be preferred over conventional trains
Inter-city transportation: Much higher speeds than are possible with steel-wheeled trains, lower noise, greater passenger comfort, increased safety against mechanical failures, reduced maintenance.
Relative to aircraft: Higher energy efficiency, safer, less weather-dependent, and would permit in-city departure and arrival.
Urban transit systems: Lower noise, much lower maintenance, greater rider comfort, can climb steeper grades, potentially higher energy efficiency than buses or rubber-tired urban trains.
Two different types of Maglev trains have been built and demonstrated at full scale at speeds up to 500 km/hr
Magnetic attraction - EMS (Electro-Magnetic Suspension) systems, using servo-controlled electromagnets on the train car, attracted upward to a iron-plate rail.
Magnetic repulsion -EDS (Electro-Dynamic Suspension) systems, using cryogenically cooled superconducting magnets on the moving car, repelled by currents induced in coils embedded in “tracks” on each side of the train.
Example EMS system: The German Trans-Rapid TR08 demonstration train and 30 kilometer test track, with operating speeds up to 450 km/hr.
Example EDS system: The Japanese Yamanashi demonstration train, with speeds of 500 km/hr on a 18 kilometer test track.
The LLNL “Inductrack” maglev system developed as a spin-off from the Lab’s flywheel energy storage program
It is an EDS system, but uses only permanent magnets and does not require cryogenically cooled superconducting coils
It is a passive system that requires no control circuits to maintain stable levitation
Levitation off of the auxiliary wheels occurs as soon as a low “transition speed” is reached.
The Inductrack system is”fail safe” in the event of a power failure; the train car would simply slow down and settle down on its auxiliary wheels at a low speed.
The simplicity of the Inductrack should make it substantially less expensive than the present EDS or EMS maglev trains.
The Inductrack system optimizes levitation efficiency, using permanent magnets and a passive “track.”
Special arrays (Halbach arrays) of permanent magnets are employed, mounted on “bogies” underneath the car.
The periodic magnetic fields from the magnet arrays on the moving train car induce currents in a close-packed array of shorted electrical coils in the “track” to produce levitation (above a low “transition” speed).
In the 1980’s Klaus Halbach came up with better ways to employ permanent magnets in focusing particle beams
The Halbach array makes optimal use of permanent-magnet material by concentrating the field on the front face of the array, while nearly canceling the field on the back face of the array
The magnetic field on the front face of the array varies sinusoidally with position parallel to the face of the array, and falls off exponentially with distance away from the front face.
Only permanent-magnet material is employed in Halbach arrays; no “back iron”elements or iron poles are needed.