Sensorless rotor position detection capability of a dual three-phase fractional-slot IPM machine

The interest for fractional-slot permanent magnet (PM) synchronous machines is more and more increasing in recent years. Particularly attractive is the interior PM (IPM) machine, since it is characterized by two torque components: the PM torque and the reluctance torque. Thanks to this feature, the IPM machine is able to operate under flux-weakening conditions, as required by many applications, such as automotive, machine tools, washing machines, and so on. Another feature is that the rotor position can be detected without sensor also at zero speed, by means of techniques based on high-frequency signal injection. The aim of this paper is to investigate the torque components and the sensorless position detection capability of an IPM dual three-phase machine equipped with two fractional-slot windings. These two windings are designed to be supplied by two separate converters, yielding an increase of the fault-tolerant capability of the machine. The analysis and the tests presented deal with the capability of the machine when it operates under healthy as well as faulty conditions, that is, when one three-phase winding set is removed and only one continues to be supplied.