Experimental Tests of Fractional-Slot SPM Motor with Star-Delta Windings

A surface-mounted permanent magnet (SPM) motor has been designed to address a winding with two combinations of star- and delta-connected coils. Its performance, in term of torque behaviour, has been simulated and experimentally tested in healthy conditions as well as with open-circuited coils. An analytical model is proposed to compute the currents in the coils which are adopted to predict the torque behaviour. Experimental results are compared to the analytical predictions, finding a suitable match. Different winding connections have been tested, with the aim of investigating the advantages in comparison to the classic three-phase winding.