Performance calculation for single-sided linear induction motors with a double-layer reaction rail under constant current excitation

A method for computing the performance of a single-sided linear induction motor (SLIM) with a double-layer reaction rail, under constant current excitation, is presented. This method takes into account the reaction of secondary eddy currents on the airgap field, transverse edge and longitudinal end effects, together with skin effect, saturation, nonlinear magnetic permeability, and hysteresis in the solid steel core of a reaction rail. In an equivalent circuit of the machine, the mutual and secondary impedances are found from a solution of the two-dimensional electromagnetic field distribution. Modifying factors account for configurations in which the width of the secondary conductive layer is different from that of the steel core, and in which the thickness of the conductive overhand is different from that over the steel core. Good correlation is obtained between analysis and test results from a large-scale linear induction motor (LIM) at Queen´s University. The developed expressions are appropriate for small and large LIM´s and may also be used for constant voltage excitation conditions.