Teaching electrodynamic levitation theory

A theoretical approach to teaching the principles of electrodynamic levitation is described. Two theories are used to obtain analytical solutions to predict the performance of a simple MAGLEY arrangement. The first theory, based on Maxwell's equations and vector force relationships, is for a simplified model allowing for a finite-thickness track conductor. The second theory is for a thin plate track and is a straightforward calculation of the lift and drag forces for a particular electromagnetic repulsion geometry, involving solution by one-dimensional integral equations. The magnetic flux source travels at a constant velocity and is derived from a sinusoidally distributed current sheet which in practice can be derived from windings or permanent magnets. Edge and end effects are neglected in both cases, which is equivalent to assuming infinite iron above the excitation surface and below the conducting plate. The simplified theory is illustrated quantitatively by a laboratory experiment in which a tray of permanent magnets is suspended over a rotating conducting plane. Gap magnetic field and drag force are measured as functions of velocity. The theoretical approach allows the following aspects to be investigated: the magnetomotive force and physical dimensions to produce suitable field magnitudes and measurable forces; the effect of harmonics by practical measurement of field profiles; and the effect of skin depth and conducting plate dimensions.<
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