Effects Of Slot On Torque And Loss Of Halbach Fault-tolerant Permanent-magnet Motors

Due to the increasing market demands of motors in modern industry, it is extremely important to improve their electromagnetic performance and reliability. Thus, high-reliability permanent-magnet fault-tolerant(FTPM) motors have been gaining great attention. For FTPM motors, their performance of FTPM motors is greatly affected by the back-EMF, the torque, the losses and the efficiency, and they are influenced each other. So we have to analyze the performance of the motor in many aspects.Two 8-notch/6-pole Halbach FTPM motors with different notch structures were designed and analyzed in this paper, and mainly analyzed their influence on no-load back-EMF, torque and eddy current loss. In details, based on the models of FTPM motors in finite element method(FEM), the structure parameters of FTPM motors were optimized. And then, analyses were made that how the variation of notches affected the static characteristics,the torque, the rotor current losses, and the efficiency. Finally, a manufactured prototype and related hardwares were introduced. The achievements of this paper were summarized as:1. To improve the sine degrees of back-EMF and great torque ripple in the existing half open-slot FTPM motors, an open-slot FTPM motor was proposed by optimizing the notch width and the rotor pole arc of the existing ones. And performance analyses of these two motors were made based on FEM models, and the performance analyses included magnetic field lines, no-load counter electromotive forces, harmonics,inductance, etc.2. The formulas of cogging torque and output torque were studies, as well as the one of output torque and tank full rate, and analyses were made that how the notch structure affected the cogging torque and the output torque, which further validated the formulas.All analyses above were prepared for the following researches that how the notch structure affected the rotor eddy current losses.3. Firstly, based on FEM models of these two motors with different notch structures,comparisons of rotor eddy current losses were made. And the principles and the characteristics of rotor eddy current losses were analyzed, and then the formulas werededuced. Secondly, the definition, the principles and the formulas of conformal transformation were introduced, and analyses were made that how open slots affected gap flux density and eddy current density in Matlab based on conformal transformation and final results were obtained. Thirdly, axial segmentation was applied to rotor permanent magnets in 3-D finite element simulation to decrease the eddy current loss of the open-slot FTPM motor.4. Analyses were made that how different notch structures affected core losses and effectiveness. And their prototype were manufactured and relative tests were conducted on it.