Comparison of flux switching and modulated pole linear machines for use with a free piston

This paper investigates the design of direct drive linear generators for use in Free Piston Engines. Flux switching, modulated pole and surface mounted magnet machines are individually modelled and optimized to react the force of the engine with minimum magnet mass. The mass of magnet used in each design is found to be heavily dependent on the copper loading in the machine and the flux produced at no load. The modulate pole or transverse flux machine, which in other applications gives an extremely efficient use of magnet, is here shown to be more effective than conventional machines but less effective than the flux switching machine.