Evaluation of the effect of doubling the stator slot number of a permanent magnet machine

Abstract

The slot numbers of an electric machine play an important role in the machine’s output performance(s). Thus, the significance of doubling stator slot number of a Double Stator (DS) Permanent Magnet Machine (PMM) is presented in this study; to evaluate its impact on the overall electromechanical output of the considered machine and for better guide on appropriate slot-pole number combinations of the chosen machine type. The number of slots considered is six (6) slots and its corresponding binary is taken to be twelve (12). The machine indices comprise: flux linkage, induced voltage, torque, loss, power, and efficiency. Finite Element Analysis (FEA) is implemented in this investigation using MAXWELL-2D software. The study shows that the 12-slot machine configuration has higher flux linkage, induced voltage, power, and torque values compared to its equivalent 6-slot machine. The predicted shaft torque and power of the 6-slot machine are 0.93 Nm and 353.5 W, respectively, while the corresponding values obtained for 12 slots are 1.42 Nm and 491.3 W. However, greater electromagnetic loss and consequent lower efficiency are obtained from the 12-slot machine type, coupled with high usage of magnetic materials and likely higher cost consequences. The investigated machine is suitable for in-wheel traction applications.