SciTech

# Maglev trains allow for fast travel

Despite huge technological advances in the past several decades, common alternatives to air travel are relatively slow. A trip that would take a few hours on a plane could take days (or be impossible) by car, bus, or engine-powered trains. Enter the maglev train.

The term maglev is derived from “magnetic levitation,” a powerful technology that can accelerate trains up to 361 mph. This is comparable to the average speed of a commercial airplane, which, according to Boeing, is 565 mph. To achieve such high speeds, most maglev trains utilize EMS, or electromagnetic suspension.

EMS works on the basic principle that opposite magnetic poles attract while like poles repel. Inside the track is a long series of magnetized coils known as the guide way. An electromagnetism research exhibit at Northeastern University explains that these coils generate a large magnetic field of the same type as the magnets attached to the underside of the train. Since the track and the train have like magnetic poles, they repel, causing the train to actually levitate between one and 10 cm above the guiding coils. The maglev remains levitated for the duration of travel, meaning that the negative impact of friction is effectively zero. This allows the train to maintain its speed for larger distances with a relatively small energy output.

The lack of friction raises an important question: Without anything to push off against, how does the maglev train accelerate? The answer, once again, lies in the power of electromagnetism. The power supplied to the coils of the track alternates at a rapid pace, causing the portion of the track behind the train to have one magnetic polarization and the portion in front to have the opposite. Calculated precisely, this allows the track to magnetically yank the train from the front (since opposite forces attract) and push the train from behind (since like forces repel). This constant magnetic system of push and pull allows the train to achieve high speeds without an engine.

Currently in development, a Japanese alternative to the EMS maglev system uses EDS, or electro-dynamic suspension. While tracks in EMS require a constant source of energy to keep the magnetic field fluctuating, EDS tracks use super-cooled conductors, which allow for a magnetic field to exist even when the energy supply is shut off.

Professor Eric Hellstrom of Florida State University’s Magnetic Field Laboratory demonstrated this process with a modified train set, showing that once a conducting material drops below the critical temperature of –294°F, it becomes a superconductor, allowing for levitation. While cooling the tracks saves energy and allows the train to levitate higher, it is much more expensive than the EMS method.

In terms of speed, energy efficiency, and maintenance, maglev trains far exceed the limits of other types of land travel. As researchers around the world improve the technologies of trains, costs, —which are currently around \$45 million per mile of track — will reduce as well. A group known as American Maglev Technology (AMT) has developed a “smart vehicle” that requires only \$20 million per mile — a significant improvement from conventional models.

Thanks to that oft-repeated principle of “opposites attract,” we may soon see the day when maglev replaces cars, buses, and conventional trains as the most efficient form of transport on land.