The objective of this project was to develop switches capable of rapid operation at the maximum vehicle speeds for magnetically levitated (Maglev) systems with difficult topologies. Maglev systems require switches capable of enabling entry and exit from the main guideway at high speed (up to 134 m/sec) in order to maintain guideway capacity. Conventional vehicle and guideway configurations in which the vehicle wraps around the guideway are not well-suited to the implementation of a high-speed switch. Switching sections must be long (typically 300m or longer at 134 m/sec) to maintain ride quality. Mechanical systems which bend large sections of guideway to allow switching are not practical for such long lengths.

During the course of the project, concepts were evaluated that provided electromagnetic means of switching and required no moving structural guideway parts This effort analyzed the limits of performance in terms of speed, failure modes, susceptibility to interference, cost, and related performance factors. Ultimately, a concept that put the levitation coils on the sides of the track was chosen for implementation in a one-twentieth scale prototype test.

The prototype machine is an electrodynamics suspension (EDS), approximately 3m long, operating at 10 m/sec, and has successfully switched the test vehicle onto either of two different tracks. The full-scale machine would consist of superconducting coils mounted on the vehicle (which act like very strong permanent magnets) interacting with passive coils mounted on the track. In the full-scale system, there would be no power supplied to the coils through track-side electronics -- the track-side electronics would merely serve to open or short the ends of the coil to perform the switching function. The machine is a "null-flux" suspension, which means that when there is no displacement of the vehicle from the centered position with respect to the coils, the net flux linking the coils is zero. When the vehicle is displaced, a net flux links the coils, causing a current in the coils that tends to force the vehicle back towards the centered position. The prototype machine has the track coils function like solenoids. Instead of superconducting coils, this small-scale prototype employs pairs of strong, rare-earth magnets mounted on the vehicle.

Each coil is attached to a dedicated circuit board. The boards communicate the desired switch position to one another, and the coil controllers that are on the desired vehicle path close their switches so that their coils are shorted. In this small-scale prototype, the circuit boards also perform a secondary function of offsetting the DC resistance of the track coils, so that the prototype can be suspended at a relatively low speed.

Return to Advanced Materials

Printable Version