Analysis of competing topologies of linear induction machines for high speed material transport systems

The authors investigate longitudinal and transverse flux linear motor topologies for very high acceleration rate (3-4 g) and high speed (120 km/hr) material transport systems which have significant technical and economic potential in flexible manufacturing environments. The general topology under consideration is a double-sided, short moving-secondary/long-fixed-primary, linear induction motor (LIM). The transport system requirements place severe demands on the machinery topology. In addition to efficient thrust production, the linear machine must be capable of generating large unbalanced normal (i.e., lateral) forces in order to achieve electromagnetic (mechanically passive) steering of vehicles with both straight and curvilinear primaries. Air gap chording and short secondary effects are two additional design complications. Particular emphasis is placed on the orientation of the magnetic flux (i.e., longitudinal vs. transverse). A hybrid system topology consisting of a longitudinal-flux orientation within straight sections and a transverse-flux orientation within curvilinear sections appears to offer the best of both topologies