When a magnetic rotor is both rotated and translationally moved above a conductive, nonmagnetic, guideway eddy currents are induced that can simultaneously create lift, thrust, and lateral forces. In order to model these forces, a 3D finite-element model with a magnetic charge boundary has been created. The modeling of the rotational motion of magnets by using a fictitious complex magnetic charge boundary enables fast and accurate steady-state techniques to be used. The conductive regions have been modeled using the magnetic vector potential and nonconducting with the magnetic scalar potential. The steady-state model has been validated by comparing it with a Magsoft Flux 3D transient model (without translational velocity) and with experimental results. The 3D model is also compared with a previously presented 2D steady-state complex current sheet model.

A 3-D Magnetic Charge Finite-Element Model of an Electrodynamic Wheel

We present a two-dimensional complex steady-state finite-element method for calculating the lift and thrust or breaking forces created when a magnetic rotor is translationally moved and rotated over a conducting sheet. The method replaces the magnetic rotor with an equivalent current sheet by equating the current sheet's and magnet rotor's magnetic vector potentials. We validate the steady-state method by comparing the forces with transient finite-element models. The utility of this steady-state model is that it enables a study of the effects of parameter changes for such a machine to be undertaken rapidly.

Calculating the Forces Created by an Electrodynamic Wheel Using a 2-D Steady-State Finite-Element Method

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.

Design principles for magnetic levitation

The mechanical rotation of a radially positioned permanent-magnet Halbach array above a conducting, nonmagnetic track induces eddy currents in the track that can inductively create suspension and propulsion forces simultaneously. The parameters that affect the performance of this electrodynamic wheel are studied using a 2-D steady-state finite-element method. Tradeoffs between the lift and thrust force performance are investigated and methods to improve the thrust efficiency are proposed.

Characteristics of an Electrodynamic Wheel Using a 2-D Steady-State Model

A status report on progress toward the development of a magnetic levitation and propulsion system for mass transportation is presented. It summarizes important results and provides a bibliography for further study. Emphasis is placed on various aspects of different magnetic structures which have been proposed for this application.

Magnetic levitation and propulsion, 1975

High‐speed ground vehicles magnetically suspended above a continuous aluminum guideway by superconducting coils can have a clearance of 0.1–0.3 m. To take full advantage of the large clearance, a propulsion system with a comparable clearance is needed. Two such systems based upon physically moving static magnetic fields produced by superconducting coils are proposed. With the use of a prime mover such as a gas turbine or a diesel engine, these systems avoid power collection problems and should result in a lower‐weight propulsion unit. A numerical analysis of each has been made to determine the thrust, the lift force, and the efficiency as a function of various parameters. The mechanical efficiency of the paddle wheel appears to have a maximum of ∼60% at 483 km/h (300 mph), while that of the superconducting screw is (1‐slip) for an infinitely long machine. End effects will degrade the efficiency somewhat for a screw of finite length.

L. C. Davis

Papers

Superconducting paddle wheels, screws, and other propulsion units for high‐speed ground transportation