Comparative Studies on Linear Motor Topologies for Reciprocating Vapor Compressors

The paper examines the relative merits of competing linear motor technologies and topologies for reciprocating compressor applications. It has been shown that a single-phase, short-stroke, tubular permanent magnet excited motor with a quasi-Halbach magnetized armature and a slotted stator is the most appropriate, due to its high specific force capability and efficiency, its relative simplicity, and the availability of emerging soft magnetic composite materials and high-energy rare-earth permanent magnets. The magnetic field distribution, emf and thrust force of the proposed motor are subsequently established analytically in cylindrical co-ordinate system. The analytical results are compared with finite element calculations. It has been shown that the difference in average emfs (thrust force) between the analytical and FE predictions over a stroke range of 0.01 (m) is less than 5%. Measurements carried on a single phase, short-stroke, prototype motor have validated the analysis, and the emf and thrust force predictions.