Coupled Magnetic Circuit-Based Design of an IPMSM for Reduction of Circulating Currents in Asymmetrical Star–Delta Windings

Combined star (Y)–delta ($\Delta )$ windings suffer from undesirable circulating currents resulting in increased winding losses and saturation, leading to demagnetization in permanent magnet synchronous machines (PMSMs). The main causes for these currents are the induced voltage harmonics from the winding configuration and rotor saliency. Thus, this article presents a novel coupled winding function and magnetic circuit model to accurately model the winding harmonics and rotor saliency in $Y$ –$\Delta $ wound PMSMs. Unlike existing winding harmonic analysis methods, such as winding factor approach and star of slots, the developed winding function incorporates the effect of winding asymmetry. Although asymmetrical $Y$ –$\Delta $ windings suffer from higher circulating currents, such configurations result in higher torque, efficiency, and reduced torque ripple when compared to conventional symmetrical windings. Therefore, using the proposed magnetic circuit model incorporating rotor saliency, an interior PMSM (IPMSM) rotor structure is developed for reduced circulating currents without compromising the traction performance. Experimental results are presented to highlight reduced circulating currents in terms of induced voltage harmonics and machine saliency and to illustrate its effect on the machine’s superior traction performance capability such as improved rated torque, efficiency, and reduced torque ripple, winding losses, and magnetic saturation.