Multilayer Bonded Magnets in Surface-Mounted PM Synchronous Machines

This paper investigates the manufacturability and applicability to electrical machines of unified multilayer magnetic blocks consisting of PMs with variable magnetic force. In particular, the self-produced multilayer magnets are realized using compressed phenolic NdFeB bonded powders for the ‘strong’ magnet layer, and hybrid composite materials for the ‘weak’ magnet layer. Different material combinations for the self-produced permanent magnets have been experimentally investigated, and their applicability of resultant multilayer bonded magnets to electrical machines is articulated on the basis of simulations. An existing geometry of a small surface-mounted PM synchronous machine has been chosen as reference, and the influence on the machine performance of conventional single-layer and multilayer magnets have been studied. In detail, the back-EMF, output torque, torque ripple, losses, efficiency, and the cost have been assessed.