Looking down the track at very fast trains

Box 2 | How the maglev works

If you put two magnets together they will either repel or attract, depending on their polarity: two magnets with the same polarity will repel and two with different polarities will attract. Levitating, guiding and propelling the maglev is based on these properties of magnets.

Levitating the maglev

The attraction or repulsion of electromagnets is used to levitate a maglev. On one breed of maglevs, the Transrapid, levitation magnets fitted to the train are attracted to support magnets on the underside of the guideway. A computer-controlled system ensures that the vehicle levitates – via this attractive force at a constant distance from its guideway. In other words, the two magnets attract each other and thus lift the carriage, but the attraction is not strong enough so that the two magnets make contact with each other. The train therefore 'floats', making no physical contact with the guideway.

Some other types of maglev use the repelling force of magnets with the same polarity to levitate the train. In all types, guidance magnets ensure that the train remains at the appropriate distance from the vertical edge of the guideway.

Propelling the maglev

Electromagnets also propel maglev trains. A series of electromagnets are laid out in a line along the guideway and electromagnets are installed on the train.

An electromagnet on the guideway pulls a train magnet towards it because it has an opposite polarity. As the train passes over the guideline magnet, the polarity of the magnet is reversed so it matches that of the train magnet, thus repelling the train magnet. As the train hurtles along, the electromagnets in the guideway switch on and off and reverse polarity as required. Electric current activates the guideway electromagnets only when the train passes over them.

Box
Box 1. The centrifugal effect and tilt trains

Related sites
How maglev trains will work (How Stuff Works, USA)
Maglevs (magnetically levitated trains) (Oliver Keating)

External sites are not endorsed by the Australian Academy of Science.
Posted October 1998.