Modular airgap windings for linear permanent magnet machines

This study proposes an offset concentrated wound air-core linear synchronous machine for launch applications where reduced supply volt-amp per newton (VA/N) and attraction force is essential. A winding factor model based on the conductor distribution is derived and used to analyse the winding factor of possible topologies. Two configurations, 3-coil/4-pole and 12- coil/14-pole, have high fundamental winding factors and are selected for the design comparisons. Machines using single- and double-sided offset windings are compared. The results obtained for these selected designs show that the 3-coil/4-pole design with offset winding provides the highest thrust due to its higher winding factor, but the 12-coil/14-pole design has lower supply VA/N. The implementation of the offset windings reduces VA/N. A significant reduction can be seen when the long stator short rotor arrangement is considered. A half-segment prototype is built and tested. The experimental results obtained validate both the algebraic and three-dimensional finite element analysis.