Design principles for magnetic levitation

Abstract

General relations and limitations pertinent to the design of an inductive magnetic suspension system are derived. It is shown that in order to reduce magnetic drag we must increase the vehicle field and decrease the guideway currents. But this then produces a stiff suspension unless we are willing to increase guideway cost. Reasonable and consistent design objectives are shown to be: vehicle natural frequency for heave≃1 Hz without secondary suspension; suspension power lossessime;10 kW/ton (L/D=120 at 270 mi/h); aluminum requirements≃80 kg/m for a dual guideway. It was shown to be theoretically possible to operate at arbitrarily low speeds by using either a superconducting guideway or a feedback control system for short distances near terminals. Between terminals the guideway might resemble a parallel-wire transmission line with a thin conducting sheet between the wires. The design of an active-guideway linear synchronous motor is discussed and shown to be capable of supplying 5 MW of power at efficiencies of about 85 percent and a power factor of 0.5. For a dual guideway the armature windings require about 40 kg/m of aluminum, but no steel. The total cost of the maglev portion of a 120 m/s (268 mi/h) high-speed ground transportation system is estimated to be about 1 million dollars/km, with at least half of this related to propulsion and power distribution and control. If speed is reduced to 90 m/s (202 mi/h), substantial economies are possible.