Identification and feature characterization of low voltage FS-IPM synchronous machines

The paper deals with a class of fractional-slot PM synchronous machines (FSPMSMs) which are characterized by specific star of slots including two spokes of back-EMF phasors in each of the two sectors allocated to a given phase. This offers the possibility to build the armature with phases made up of parallel-connected dual coils. With this done, an improvement of the fault-tolerance capability is gained under open-circuit faulty operation in so far as a failure affecting a coil would discard one among the parallel branches of the corresponding phase, rather than the total phase in FSPMSMs with series-connected coils in the armature. The fallouts of the parallel connection on the torque production capability are investigated through a comparison of the resulting iso-torque curves, plotted in the direct-quadrature currents plane, with those yielded by the series connection. It has been found that, while the torque is almost halved for a given armature current, the constant torque and flux weakening speed ranges are similar under both coil connections.