TORQUE AND MAGNET HEATING IN A SURFACE-MOUNTED PM MOTOR: A COMPARISON BETWEEN SLOTTED AND SLOTLESS STATOR DESIGNS

The advantages and disadvantages of two permanent magnet motor designs – slotted and slotless – are analyzed. A commercially available micromotor was adopted as the slotted design. Their performance is compared in terms of torque production and permanent magnet heating under intensive operating conditions. The rotor geometry was as-sumed to be identical, the maximum flux density in the magnetic cores was set to 1,7 T, and the rotational speed was considered constant. Modeling was carried out using COMSOL Multiphysics, with the results for the slotted design validated using the Simcenter Motorsolve software package. The torque and the amplitude of torque pulsations for both designs were evaluated, and the differences between them were analyzed. The causes of magnetic flux density pulsa-tions in the magnets were studied, and their impact on eddy current losses was assessed. Numerical results for the out-put parameter ratios of the two designs were presented. The possibility of neglecting magnet heating in the slotless de-sign was emphasized. References 11, figures 8, table 1.