Design considerations for a PM synchronous motor with rotor saliency for high speed drives

Some new design proposals of permanent magnet synchronous motors for extending their flux-weakening capabilities propose a saliency ratio I/sub d//I/sub q/ greater than one, contrarily to classical designs that exhibit a value lower than one. This paper presents a comparison of several effective design solutions of synchronous motors including both the classical and the new solutions. To better understand the peculiar differences in the motor design, the same base and flux-weakening performance are fixed. The influence of the saliency ratio to inverter volt-ampere ratings, maximum feasible speed and current control characteristics is highlighted and discussed.