Salient-rotor PM synchronous motors for an extended flux-weakening operation range

This paper proposes some novel designs of permanent-magnet synchronous motors for extending their flux-weakening capabilities. According to such a proposal, the motors are characterized by a saliency ratio l_d/l_q greater than one, whereas classical designs exhibit a saliency ratio lower than one. The innovative and classical design solutions are deeply compared in the paper. In order to understand better the basic differences in the motor design, the same base and flux-weakening performance are fixed. The influence of the saliency ratio on inverter voltampere ratings, maximum feasible speed, and current control characteristics is highlighted and discussed