Foster-Miller has been an active contributor in the development of magnetic levitation (Maglev) technology for high-speed ground transportation. The Department of Transportation sponsored work to develop the locally commutated linear synchronous motor (LCLSM), an idea that we originated. Unlike rotating machines, the moving part of this machine (corresponding to the rotor of a rotating machine) and the stationary part (stator) must have different lengths. Foster-Miller reviewed two design options.

• Short Stator. The powered motor windings are mounted on the moving vehicle. This decreases the size of the wound motor that must be built, which is an asset. However, the short stator approach increases vehicle weight, requires power transfer to the moving vehicle, and can exacerbate entry and exit effects. Power transfer and end effect phenomena are particularly problematic at high vehicle speeds.
•  Long Stator. Although a much longer wound section must be built (essentially the entire length of the track), no power transfer is required to the moving vehicle. The vehicle can interact with the track via passive conducting plates, permanent magnets, or superconducting coils. The LCLSM takes the long stator approach. There is an array of vehicle-mounted permanent magnets that interact with a series of track coils. To make the machine amenable to laboratory experiments (i.e., so an experiment can run continuously) the track of the LCLSM machine is wrapped into a circle.
  For any long stator machine, the track must be segmented into sections that are powered only when a vehicle is present. On this program, Foster-Miller evaluated local commutation, in which each track coil is individually driven by its own dedicated power and control electronics. The advantages of local commutation rather than powering large track sections are: 
•  A high level of fault tolerance. Since the coils are individually controlled, many individual coils can fail without noticeably degrading the track's ability to drive vehicles.
• No limitations on vehicle proximity. A vexing problem in typical long-stator maglev trains is that only one train can be in an energized block at a time. This can be especially problematic near stations, when trains are necessarily in close to each other.  When the coils are locally commutated, trains can be very close to one another because the sections of track that drive each train do not interact.

Return to Thermal Systems

Printable Version