Cogging Torque Reduction in External Rotor PM Synchronous Motors by Optimum Pole Embrace

In this paper, a 4 kW external rotor permanent magnet (PM) synchronous motor was designed. It is aimed to obtain minimum cogging torque and minimum torque ripples by optimum pole embrace ratio. Conceptual design was modeled and analyzed by 2D finite element analyses (FEA). Low order harmonics of the induced phase voltages and torque ripples are investigated. According to optimization results, an external rotor PMSM was obtained with low cogging torque and low torque ripple. The designed PMSM was compared with a commercial inner rotor PMSM and much better performance results are taken.