Combined Star-Delta Windings to Improve Synchronous Reluctance Motor Performance

This paper analyzes and compares the synchronous reluctance motor (SynRM) performance for a conventional star winding and for a combined star-delta connected winding under healthy and faulty conditions. The finite element method is used to simulate the SynRM characteristics in case of normal star and in case of combined star-delta connected windings. For the healthy case, it was found that for the same current, the SynRM output power increased by about 5% for the star-delta connected windings compared with the conventional star connection. Moreover, the efficiency increased slightly by 0.20%. Probably the strongest advantage of the combined star-delta winding is observed when a phase fault occurs. When one phase is missing, for the same current, the star-delta connected motor keeps 80% of the rated torque in the healthy case, while the star connected motor only keeps 40%. Furthermore, the torque ripple of the star wound machine is extremely high in case of a missing phase, compared to the star-delta wound machine. Simulation results were validated by experimental results to show the effectiveness of the star-delta connected windings on the SynRM.