Analysis of Various Slot and Pole Number for PM Flux Switching Machines for Electric Bicycle Applications

Permanent magnet flux switching machine (PMFSM) has the benefits of a robust design structure, high efficiency, and high torque density. The way to improve the performance and reduce the cost of the machine by selection of pole and slot number is an important issue to be solved. This paper presents a complete performance comparison of a PMFSM design motor with different combinations of slot and pole numbers. Under the same machine diameter and volume of permanent magnet, the flux linkage, unwanted/cogging torque, back-electromotive force (EMF), output torque and power performance are investigated and compared. The results display that the combinations of slot and pole numbers have a major impact on the performance of motor design. Four PMFSM motor design configurations, namely motor 1 with 4S-8P, motor 2 with 8S-16P, motor 3 with 10S-20P and motor 4 with 12S-18P are compared to observe the best one for electric bicycle application. 2D finite element analysis (2D-FEA) with JMAG Designer version 14.1 is used to perform the analysis. Simulation result displayed the 4S-8P PMFSM structure has produced 4.1Nm, compared with the other three designs namely 8S-16P at 1.8Nm, 10S-20P, and 12S-18P at 2.15Nm and 0.48Nm respectively. Motor 1 by 4S-8P illustrated a valuable opportunity to achieve the target performances compared to rest of other selected motor and will be even better in the future. The results of the comparison show that motor 1 with 4S-8P is the best selection according to the criterion of maximum torque performance. However, it is found that high back EMF under no load condition due to the high flux linkage. Therefore, through greater refinement and optimization of the design in the selected configuration of the stator pole and the rotor, it is expected to achieve the target performance of the PMFSM design.