Eddy current effects in a homopolar permanent-magnet array for maglev applications

Magnetic levitation systems exploiting homopolar flux designs aim to reduce power losses. Hybrid electromagnetic suspensions in homopolar arrangements capable of zero-power levitation are of interest due to their affordable track construction with no laminations. Although induced eddy current density is lower in a transverse-flux magnetic circuit, parasitic effects are nevertheless present. Thus, magnetic drag as well as lift force reduction are of concern at high speeds. The present study addresses modelling and experimental validation of this phenomenon in a permanent-magnet array for a hybrid electromagnet levitation module. Previous work has largely centred on eddy current effects for conventional electromagnets. The analytical model based on the magnetic flux density Fourier transform is refined for the studied design, where skin effect and flux leakage as functions of air gap and speed are introduced. A finite-element model is presented, with results motivating the proposed analytical model refinement. Subsequently, a magnetic levitation test bench is used to acquire experimental forces. It is shown that the analytical model is able to reproduce the described behaviour when compared against the finite-element model and the experiments. This poses a substantial advantage in terms of computational cost, making the analytical model a useful tool for component design and parametric optimisation.