Eddy Current Distribution and Lift Force for Finite Maglev Strips

Abstract

The transverse distribution of induced eddy currents across a flat conducting strip of finite width, due to a rectangular d.c. magnet moving above it, has been modelled experimentally, and has been compared with that calculated for an infinite sheet. The electrodynamic suspension was simulated by means of a stationary a.c.-excited copper magnet suspended above an aluminum strip, and the induced surface current density was measured by a voltage pickup probe connected to a lock-in amplifier. Good agreement is obtained between the eddy current profiles for a wide sheet and those calculated by determining the current distribution required to cancel the vertical component of the magnet field at the surface of the sheet. The effect of reducing strip width is examined and shown to produce high current densities close to the edges. These results are related to the variation of lift force with strip width, determined by impedance modelling. A slight enhancement of lift is evident for intermediate strip widths.