I. Introduction
Three-phase line-start permanent magnet synchronous motors (LSPMs) are a recent entrance in the marketplace. The rotor of this type of motor integrates permanent magnets and an auxiliary cage, for direct on-line starting and synchronization purposes. In general, such motors are designed to meet IE4/Super-Premium Class, having an excellent efficiency and power factor [1]–[3], and a fair tolerance to poor power quality [4]. Although the three-phase squirrel-cage induction motors (SCIMs) are still the most used technology in Industry, they hardly achieve the IE4 class requirements [1], [3]. In Industry, SCIMs are often oversized and/or drive variable-load fixed-speed applications and, when they operate at light partial loads, the efficiency and power factor are both poor. Moreover, since in most cases the motors operate at partial load, the manufacturers optimize the design for a peak efficiency load point within 50–80% load range, which can lead to a rated efficiency slightly lower than peak efficiency.