Slot Permanent Magnet Synchronous Machines Research Articles

Analytical Calculation of Complex Relative Permeance Function and Magnetic Field in Slotted Permanent Magnet Synchronous Machines

In order to analyze accurately the airgap magnetic field of the slotted permanent magnet synchronous machine (PMSM) taking into account the influence of slotting effects, this article proposes an analytical method for calculating the complex relative permeance function. Based on one tooth pitch of the machine as the solution model, the governing Laplace field equation of the airgap region is solved analytically in the polar coordinate system. According to the boundary conditions between the slot and airgap region, the analytical expressions of the radial and tangential components of the complex relative permeance function are derived. With this complex permeance, the no-load radial and tangential airgap magnetic fields of the internal and external slotted PMSM with different slot/pole combinations are obtained. The accuracy of the analytical model is validated by the results of finite element analysis. With good simplicity and generality, this model can be an effective means for further study of motor performance.

Effects of manufacturing tolerances of permanent magnets in fractional slot permanent magnet synchronous machines

The fractional slot permanent magnet synchronous machines are well-known for their low torque ripple. However, in mass-production machines, not all the permanent magnets are identical due to the manufacturing tolerances and new torque harmonics could appear. In addition, the magnetic field is modified and unbalanced magnetic pull (UMP) could happen. Apart from that it is important to study the effect on vibrations since the magnetic field is no longer ideal. So, here, a study of the effect of unevenly magnetised permanent magnet distribution on torque ripples, unbalance magnetic pull, and vibrations is proposed. Apart from that, the tolerance grade sensitivity is studied. Finally, experimental tests show good agreement with finite element analysis.

Comparison of optimal slot/pole number combinations in fractional slot permanent magnet synchronous machines having similar slot and pole numbers

Here, the selection of optimal slot/pole (Ns-slot/pr-pole) number combination between the pairs of fractional slot concentrated winding (FSCW) permanent magnet synchronous machines (PMSMs) with Ns = 2pr ± 1 or Ns = 2pr ± 2 will be analysed by a modified winding function accounting for slot opening and validated by finite element method. The results show that for FSCW PMSMs with Ns = 2pr ± 1 or Ns = 2pr ± 2, the higher pole machine will have larger winding factor and hence better torque performance than the lower pole one. Moreover, it also reveals that this torque advantage is more evident in the external rotor machine than that in internal rotor machine.