TSURU, Yamanashi Prefecture--A rail operator has unveiled a prototype high-speed magnetic levitation train, which it plans to operate on one of Japan's busiest routes from 2027.
On Nov. 22, Central Japan Railway Co. (JR Tokai) revealed its Series L0 prototype, which after further development could enter service carrying passengers at speeds of 500 kph on the Chuo Shinkansen Line.
So-called maglev trains use magnetic repellence to lift the train above the track, eliminating friction.
JR Tokai aims to run the train between Tokyo and Nagoya on the JR Chuo Shinkansen Line, a route currently served by Japan's high-speed bullet trains. The service will be expanded to Osaka by 2045.
The new train features a streamlined nose similar to those on its bullet train counterparts, which reduces wind drag. JR Tokai plans the train to comprise 14 carriages including the cab car. The carriages contain four seats abreast; the end car can accommodate 24 passengers, while other cars will hold 68. SOURCE - THE ASAHI SHIMBUN
There's a not-unimportant misrepresentation here of the kind that tends to creep into stories on any technical topics when written by journalists who have not informed themselves of the larger picture. Like many other popular articles on maglev, this story gives the impression that maglev is a single technology, which is not the case: maglev is a family of technologies that have no more in common than the fact that they use magnets of some kind to suspend the vehicles and interact with electric currents to move them. Maglev technologies are as varied as the different wheel-on-ground technologies are, or varying winged flight technologies.
ReplyDeleteMaglev *can* use magnetic repulsion to lift vehicles (they don't have to be trains) above the guideway. This is one type of magnetic suspension, known as electrodynamic suspension (EDS), the one used in the superconducting maglev invented in the US and developed by JR Central. In EDS, the magnetic field of superconducting magnets induces currents in passive guideway windings when moving past them above a certain speed, and these induced currents generate an equal magnetic force that interacts with the on-board magnets to lock them in an equilibrium position between the two sides of the windings. This is what raises the JR maglev vehicles above the guideway above minimum speed so that the on-board magnets align with the vertical centre of the wall-mounted windings, effectively suspending the vehicles above the guideway floor.
This is also what suspends vehicles in the second-generation quadrupole version of this technology, by aligning under-chassis SC magnets with the vertical centre of box-beam mounted windings when the vehicle moves above minimum speed, or with the horizontal centre of floor-mounted windings in parts of the guideway using this alternative design, typically either electronically-controlled switches with converging or diverging guideway "tracks" or route segments with guideway panels attached to the outsides of existing railway track.
The other type of suspension is electromagnetic suspension (EMS), which is used in the German Transrapid that is in service on the Shanghai airport run, and several other similar low-speed maglev systems. This uses electromagnets on an armature wrapping around the underside of the guideway to raise the armature up toward iron rails on the underside of the guideway, raising the chassis of the vehicle above the top side of the guideway.
EMS requires constant, millisecond-level servo-controlled modulation of the current fed to the electromagnets to keep them from clamping on to the underside of the guideway whereas EDS, once the vehicle moves past the windings above a minimum speed, magnetically "locks" the vehicles into a position where the on-board magnets remain in the vertical and horizontal equilibrium position determined by the "null flux" geometry of the guideway windings. This gives EDS an inherent automatic stability that EMS needs to compensate for with constant computer monitoring and control. And although the walls on first generation JR SC maglev and the wrap-around design of EMS systems are solid barriers preventing vehicles from "derailing", i.e. leaving the track, the magnetic "lock" of EDS maglev that automatically forces the magnets into a position centred over the null-flux winding geometry, despite being invisible, is a no less powerful physical force countering any drift off the guideway.
Of course even this explanation oversimplifies to some extent, since other systems are themselves variations on one of these two main approaches to magnetic suspension, but at least it gives a more nuanced impression than the article.