Maglev – a technology for the future?

Magnetically-levitated trains are running in a small number of countries

By Morand Fachot

Railways have constantly improved since they were first introduced. However, they still rely on basically the same principle: train wheels running on steel tracks and causing friction. A technology that sees trains "floating" over a track using magnets and superconductivity may radically change train transport in the future.

Japan's MLX01-1 train holds the world record for fastest maglev train (581kph)

Not the end of the line yet

Ever since they were introduced trains have run on rails; currently those are made of steel. Even though rolling stock and rail technologies have greatly improved, allowing trains to run faster and faster, the mechanical friction between wheels and tracks is considered a factor limiting performance and requiring considerable maintenance of equipment in this well-established mode of transportation.

Magnetically-levitating trains that eliminate mechanical friction by using magnetic suspension (or levitation) are seen as offering an interesting possibility for the future of rail transport. The technology relies on superconducting magnets. Even so, existing networks built over decades are not likely to disappear soon as the few maglev trains functioning now are still mainly in the experimental phase or are running over relatively short distances.

Come fly with magnets

Maglev train rail systems need three components: a large electrical power source, metal coils lining a guideway or track and large guidance magnets attached to the underside of the train.

Two different concepts of magnetic levitation – or suspension – are currently being implemented.

EMS (electromagnetic suspension) uses electromagnets attached to the train's undercarriage; the magnets wrap around the steel guideway. The system levitates the train about 1 cm above the guideway and keeps it levitated even when it's not moving. This system is used in Germany's Transrapid train and the Shanghai Transrapid maglev train that connects Shanghai airport with its metro network.

EDS (electrodynamic suspension) is based on the repelling forces of magnets to levitate the train. In EDS systems, trains float about 10 cm above the guideway. EDS is used in Japan's MLX01 maglev train, the fastest train in the world, which reached a speed of 581 kph in 2003.

In August 2013 the mayor of Tel Aviv, Israel, announced plans to introduce skyTran, an urban maglev transportation system that uses two-seater pods hanging from magnetic rails

IEC work on superconductivity

IEC standardization work on superconductivity doesn't extend to transportation, although IEC  TC 90: Superconductivity, acknowledges that this domain could benefit from applications of superconductivity, in particular where HTS (high temperature superconductors) are introduced. Whilst LTS (low temperature superconductors) materials need to be cooled to about 4 K (- 269oC) to demonstrate superconductive properties, HTS materials reach these properties at temperatures as "high" as 77 Kelvin (- 143oC) or so.

TC 90 works on preparing International Standards to help the development of commercial markets for new products and/or applications using superconductivity.

As of March 2014 it had published 19 International Standards that concern various kinds of measurements for electronic or mechanical characteristics and properties for composite superconductors, including HTS.

TC 90 sees HTS as very promising for new applications and markets. Even so, their widespread use in maglev technology is still some years away – but then so too is the commercial operation of maglev trains.

JR-Maglev-MLX01-2 Japan's MLX01-1 train holds the world record for fastest maglev train (581kph)
TE1023_Linearmotor Cutaway of Transrapid maglev train propulsion system (Illustration: ThyssenKrupp Transrapid GmbH)
409347_orig skyTran urban mass transit pods use maglev technology (Image courtesy of skyTran)