MagLev uses magnetic levitation instead of wheels. Because the system makes no physical contact between the vehicle and the guideway, there is nothing to wear out or fail. MagLev vehicles are levitated a short distance away from the guideway and both lift and thrust are produced by electromagnets. This low-energy technology is very safe, clean and takes a giant step toward addressing global climate change.
Among the advantages of MagLev are:
- Smoother and more quiet than wheeled mass transit systems
- Acceleration and deceleration surpass that of wheeled transports
- Systems and components are unaffected by weather
- Power needed for levitation is a fraction of the overall energy consumption
- Routinely has higher top speeds than conventional rail systems
- Requires less maintenance and has lower on-going costs
Image Credit: Transrapid • www.railway-technology.com
A prime example of an active MagLev system is the German (Siemens) Transrapid MagLev. It uses the attractive forces between individual, electronically controlled electromagnets in the vehicle and in the ferromagnetic reaction rails which are installed on the underside of the guideway. The support magnets pull the vehicle up to the guideway from below, the guidance magnets keep it laterally on track. A synchronous longstator linear motor is used both for propulsion and braking. By supplying alternating current to a three-phase motor winding, an electromagnetic traveling field is generated which moves the vehicle, pulled along by support magnets which act as the excitation component. The speed can be continuously regulated from standstill to full operating speed by varying the frequency of the alternating current.
Image Credit: Lawrence Livermore National Laboratory • www.llnl.gov
An example of an early, pioneering passive MagLev system is the Lawrence Livermore National Laboratory’s Inductrack. This system has permanent magnets attached to vehicles and conductive arrays attached to the track. As the magnets move past the conductive arrays repulsive forces are generated between the two components and the vehicles lift off the track. As the gap between the magnets and track increases, the repulsion force decreases so the gap size settles at a stable distance. The only power required to achieve this is the propulsion power for the vehicle. No levitation sensors are required and there is no need or capacity for a control system.
Image Credit: MagneMotion • www.magnemotion.com
A Combination of Both
There are other MagLev systems that combine elements of both of these technologies. MagneMotion’s M3 uses permanent magnets attracting to steel rails, with electromagnets to modulate the field strength of the permanent magnets. One can think of this as a Transrapid type system bolstered by permanent magnets. Their operational gap is about 20mm.
Image Credit: JRTT • www.jrtt.go.jp
The Japanese Yamanashi system uses large superconducting electromagnets in an inductive lift configuration analogous to Inductrack, with a few extra features. The salient characteristic of superconducting electromagnets is their ability to project intense magnetic fields over a much greater distance. For this reason Yamanashi can operate with an air gap of 100mm. Unfortunately, this performance comes at the cost of having large active (powered) components whose uninterrupted performance is critical to vehicle operation and safety. In the event of a loss of function of the superconducting magnets the vehicles will not levitate and risk touching down at extreme velocity.
Next Generation (skyTran) MagLev
skyTran‘s patented STML is a “Next Generation MagLev System”; it achieves safe, reliable high speeds up to 150 mph (240 kph) allowing for large local, regional and national networks to be built. The modular design can easily be installed, inspected, and replaced when necessary thereby providing greater safety and redundancy.