Comparison of Single- and Double-Layer Windings in Spoke-type Synchronous Motors with Ferrite Magnets

In home appliance applications, spoke-type synchronous motors with ferrite magnets are gaining more attention, because of the advantages of lower cost and wider speed range compared to conventional synchronous motors with rare-earth magnets. However, ferrite magnets have lower magnetic energy product and higher risk when a demagnetizing current is applied. In this case, it is necessary to pay more attention to torque density and performance against irreversible demagnetization. In this paper, a 10-pole/12-slot spoke-type synchronous motor with ferrite magnets are designed. Configurations with single- and double-layer windings are discussed in aspects of torque density, torque ripple, efficiency, and irreversible demagnetization resistance. The results indicate that double-layer windings are superior to single-layer windings in this case, especially in aspects of irreversible demagnetization.