| Abstract |
An electromagnetic suspension system is described, in which a suspended moving object (the runner) is completely passive. The runner comprises three sets of iron pole-pieces separated by non-magnatic spacers to form a hexagonal structure, it is suspended magnetically in a tunnel formed by three iron-cored stators with distributed coils. The airgaps between the runner poles and the stators are held constant by feedback control, and the runner is moved axially by microcomputer control of the currents in the stator coils. Each stator has a 2-phase winding, with the coils grouped in pairs: each pair of coils is supplied from a separate pulsewidth modulated MOSFET power amplifier which uses a novel design for compactness and reliability. The dynamic behaviour of the 2-phase system is described, there is a severe nonlinearity in the control characteristic, which makes a constant runner velocity difficult to achieve, this problem can be largely eliminated by using a 4-phase system. |
