Comparison of Permanent Magnet Machines Equipped with Unbalanced Fractional-Slot Distributed Windings vs. Balanced Fractional-Slot Concentrated Windings

Fractional-slot concentrated winding permanent magnet (PM) machines have been gaining interest over the last decade in various applications. In this paper, a comparison of various conventional fractional-slot PM machines with an unconventional and unbalanced fractional-slot distributed winding PM motor is presented. The motors are designed for the same torque-speed curve, same design envelope, same electrical loading and magnet weight. No skewing is utilized in the designs for a fair comparison. It is found that 12-slot/10-pole and 27-slot/12-pole combinations stand out in terms of meeting the same torque-speed profile of the baseline machine with 39-slot/12-pole while having comparable performance metrics especially when it comes to reducing torque ripple.