Maglev trains need strong magnetic fields, faster changing fields, thicker material with lower resistivity such as copper, silver, aluminum etc… in order to go fast.
(EMS) "Transrapid International"
Method: Electromagnetic Suspension is based on magnetic attraction; it is very complex and somewhat unstable.
How Does It Work?: Electromagnets line the undercarriage of the train, while the "track" (seen in this diagram as the guideway) is lined with coils. Because the current is constantly changing, the polarity of the coils also changes, permitting the system of magnetic fields to pull and push the train along the guideway. A power source is constantly supplying power to the electromagnets allowing the interaction between the coils and electromagnets to levitate the train. The train levitates about 1cm and remains like this even when it's not moving. The distance is continuously monitored and corrected by computers to avoid accidents. The guidance magnets on the left of the undercarriage are use to stabilize the train, helping it avoid hitting the sides while it's moving.
How Fast? These trains can reach speeds up to 438km/h with passengers on board.
On-board Emergency Equipment: EMS trains are equipped with battery power supplies in case of power failures (trains can suddenly stop levitating and potentially crash), this allows the train to come to a smooth stop.
Potential Health Risks: *Passengers with pacemakers must be careful! The strength of the magnetic fields that are being produced is believed to interfere and disrupt pacemakers.
Method: Electrodynamic Suspension is based on the repulsion of magnets. The magnetic levitation force balances the weight of the car at a stable position. It is for this reason that the EDS system is believed to be safer than the EMS system.
How Does It Work?: Super-cooled superconducting magnets are placed on the train cars while electromagnetic coils are placed along the track. Superconductors are used because they can conduct electricity even after the power supply has been shut off (unlike the EMS system). When the trains get close to the coils a current is induced which allows the train to levitate about 10 cm and center itself in the middle of the guideway. To get the train moving a second set of coils are placed along the guidance coils and after the train reaches approximately 100km/h the propulsion coils are activated. The electric current that is constantly changing allows for a change in polarity of the electromagnets which in turn pushes and pulls the superconducting magnets of the passing train to allocate movement.
Environmentally Friendly?: By chilling the coils using cryogenics engineers are able to save energy, however the process is very expensive.
How Fast?: These trains can reach speeds up to 522km/h, which is considerably faster than the EMS trains.
Disadvantage/Advantage: EDS train must roll on rubber wheels until they reach a lift-off speed of about 100km/h which causes resistance. However having these wheels is an advantage during a power outage, it allows the train can come to a smooth/safe.