In Japan, “maglev” trains run just above, not on, their tracks. Both the bottom of the train and the track itself are magnetic. The magnets repel each other, so the train hovers just above the track, enabling it to run with less friction and so reach higher speeds.
Maglev trains incorporate a basic fact about magnetic forces—like magnetic poles repel each other, and opposite magnetic poles attract each other—to lift, propel, and guide a vehicle over a track (or guideway). Maglev train propulsion and levitation may involve the use of superconducting materials, electromgnets, diamagnets, and rare-earth magnets.
Two types of maglev trains are in service. Electromagnetic suspension (EMS) uses the attractive force between magnets present on the train’s sides and underside and on the guideway to levitate the train. A variation on EMS, called Transrapid and used in Germany, employs an electromagnet to lift the train off the guide way. The attraction from magnets presents on the underside of the vehicle that wraps around the iron rails of the guideway keep the train about 1.3 cm (0.5 inch) above the guideway.
Electrodynamic suspension (EDS) systems are similar to EMS in several respects, but the magnets are used to repel the train from the guideway rather than attract them. These magnets are supercooled and superconducting and have the ability to conduct electricity for a short time after power has been cut. (In EMS systems a loss of power shuts down the electromagnets.) Also, unlike EMS, the charge of the magnetized coils of the guideway in EDS systems repels the charge of magnets on the undercarriage of the train so that it levitates higher (typically in the range of 1–10 cm [0.4–3.9 inches]) above the guideway. EDS trains are slow to lift off, so they have wheels that must be deployed below approximately 100 km (62 miles) per hour. Once levitated, however, the train is moved forward by propulsion provided by the guideway coils, which are constantly changing polarity owing to alternating electrical current that powers the system.
Maglev trains eliminate a key source of friction—that of train wheels on the rails—although they must still overcome air resistance. This lack of friction means that they can reach higher speeds than conventional trains. At present maglev technology has produced trains that can travel in excess of 500 km (310 miles) per hour. This speed is twice as fast as a conventional commuter train and comparable to the TGV (Train à Grande Vitesse) in use in France, which travels between 300 and 320 km (186 and 199 miles) per hour. Because of air resistance, however, maglev trains are only slightly more energy efficient than conventional trains.
Picture Credit : Google