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Inductrack is a passive, fail-safe electrodynamic 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 aluminium sheets. There are three designs: Inductrack I, which is optimized for high speed operation, Inductrack II, which is more efficient at lower speeds, and Inductrack III, which is intended for heavy loads at low speed. Inductrack (or Inductrak) was invented by a team of scientists at Lawrence Livermore National Laboratory in California, headed by physicist Richard F. Post, for use in maglev trains, based on technology used to levitate flywheels.〔(【引用サイトリンク】''A New Approach for Magnetically Levitating Trains — and Rockets'' )〕〔 〕〔(【引用サイトリンク】author = Richard F. Post )〕 At constant velocity, power is required only to push the train forward against air and electromagnetic drag. Above a minimum speed, as the velocity of the train increases, the levitation gap, lift force and power used are largely constant. The system can lift 50 times the magnet weight. == Description == The name ''inductrack'' comes from the word ''inductance'' or ''inductor''; an electrical device made from loops of wire. As a Halbach magnet array passes over the loops of wire, the sinusoidal variations in the field induce a voltage in the track coils. At low speeds the loops are a largely resistive impedance, and hence the induced currents are highest where the field is changing most quickly, which is around the ''least'' intense parts of the field, thus little lift produced. However, at speed, the impedance of the coils increases, proportionate to speed, and dominates the composite impedance of the coil assemblies. This delays the phase of the current peak so that induced current in the track tends more closely to coincide with the field peaks of the magnet array. The track thus creates its own magnetic field which lines up with and repels the permanent magnets, creating the levitation effect.〔 The track is well modeled as an array of series L-R circuits. When neodymium–iron–boron permanent magnets are used, levitation is achieved at low speeds. The test model levitated at speeds above , but Richard Post believes that, on real tracks, levitation could be achieved at "''as little as ''". Below the transition speed the magnetic drag increases with vehicle speed; above the transition speed, the magnetic drag ''de''creases with speed.〔(''Track To The Future: Maglev Trains On Permanent Magnets'' ) — Scott R. Gourley — Popular Mechanics〕 For example, at the lift to drag ratio is 200:1,〔(In "MagLev: A New Approach", above, section on "The Issue of Efficiency" ) 〕 far higher than any aircraft but much lower than classic steel on steel rail which reaches 1000:1 (rolling resistance). This occurs because the inductive impedance increases proportionately with speed which compensates for the faster rate of change of the field seen by the coils, thus giving a constant current flow and power consumption for the levitation. The Inductrack II variation uses two Halbach arrays, one above and one below the track, to double the magnetic field without substantially increasing the weight or area of the arrays, while also reducing drag at low speeds.〔(''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 space planes.〔 〕 General Atomics is developing Inductrack technology in cooperation with multiple research partners. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Inductrack」の詳細全文を読む スポンサード リンク
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