Kontam da hoce neki zabavani park da napravi u fazonu
sedne nekoliko ljudi u neki tanjir, on ukljuci elektromagnet
i oni krenu da se dizu ka gore. Cak i da se napravi taj gigantski
magnet, vec mi je u glavi slika sudbine tih u tanjiru.
Elem, posto Maglev radi na tom principu, evo sta sve moras da
uzmes u obzir na samo 15 mm rastojanja i koliko je problem
kontrolisati levitaciju, a nije ni moguce u svim uslovima (pri
svim brzinama voza):
[Ovu poruku je menjao Srđan Pavlović dana 19.07.2012. u 04:29 GMT+1]
Main article: Electromagnetic suspension
In current electromagnetic suspension (EMS) systems, the train levitates above a steel rail while electromagnets, attached to the train, are oriented toward the rail from below. The system is typically arranged on a series of C-shaped arms, with the upper portion of the arm attached to the vehicle, and the lower inside edge containing the magnets. The rail is situated between the upper and lower edges.
Magnetic attraction varies inversely with the cube of distance, so minor changes in distance between the magnets and the rail produce greatly varying forces. These changes in force are dynamically unstable – if there is a slight divergence from the optimum position, the tendency will be to exacerbate this, and complex systems of feedback control are required to maintain a train at a constant distance from the track, (approximately 15 millimeters (0.59 in)).
The major advantage to suspended maglev systems is that they work at all speeds, unlike electrodynamic systems which only work at a minimum speed of about 30 km/h (19 mph). This eliminates the need for a separate low-speed suspension system, and can simplify the track layout as a result. On the downside, the dynamic instability of the system demands high tolerances of the track, which can offset, or eliminate this advantage. Laithwaite, highly skeptical of the concept, was concerned that in order to make a track with the required tolerances, the gap between the magnets and rail would have to be increased to the point where the magnets would be unreasonably large. In practice, this problem was addressed through increased performance of the feedback systems, which allow the system to run with close tolerances.
Main article: electrodynamic suspension
JR-Maglev EDS suspension is due to the magnetic fields induced either side of the vehicle by the passage of the vehicle's superconducting magnets.
EDS Maglev propulsion via propulsion coils
In electrodynamic suspension (EDS), both the guideway and the train exert a magnetic field, and the train is levitated by the repulsive and attractive force between these magnetic fields. In some configurations, the train can be levitated only by repulsive force. In the early stages of JR-Maglev development in Miyazaki test track, a repulsive system was used, instead. This fact sometimes causes conception that the EDS system is a repulsive one, but that is not true. The magnetic field in the train is produced by either superconducting magnets (as in JR–Maglev) or by an array of permanent magnets (as in Inductrack). The repulsive and attractive force in the track is created by an induced magnetic field in wires or other conducting strips in the track. A major advantage of the EDS maglev systems is that they are naturally stable – minor narrowing in distance between the track and the magnets creates strong forces to repel the magnets back to their original position, while a slight increase in distance greatly reduces the repulsive force and again returns the vehicle to the right separation. In addition, the attractive force varies in the opposite manner, providing the same adjustment effects. No feedback control is needed.
EDS systems have a major downside as well. At slow speeds, the current induced in these coils and the resultant magnetic flux is not large enough to support the weight of the train. For this reason, the train must have wheels or some other form of landing gear to support the train until it reaches a speed that can sustain levitation. Since a train may stop at any location, due to equipment problems for instance, the entire track must be able to support both low-speed and high-speed operation. Another downside is that the EDS system naturally creates a field in the track in front and to the rear of the lift magnets, which acts against the magnets and creates a form of drag. This is generally only a concern at low speeds (This is one of the reasons why JR abandoned repulsive system and adopted sidewall levitation system.); at higher speeds the effect does not have time to build to its full potential and other forms of drag dominate.
The drag force can be used to the electrodynamic system's advantage, however, as it creates a varying force in the rails that can be used as a reactionary system to drive the train, without the need for a separate reaction plate, as in most linear motor systems. Laithwaite led development of such "traverse-flux" systems at his Imperial College laboratory. Alternatively, propulsion coils on the guideway are used to exert a force on the magnets in the train and make the train move forward. The propulsion coils that exert a force on the train are effectively a linear motor: an alternating current through the coils generates a continuously varying magnetic field that moves forward along the track. The frequency of the alternating current is synchronized to match the speed of the train. The offset between the field exerted by magnets on the train and the applied field creates a force moving the train forward