Improved Method for Calculating Armature-Reaction Field of Surface-Mounted Permanent Magnet Machines Accounting for Opening Slots

Abstract

-This paper presented an improved analytical method for calculating armature-reaction field in the surface-mounted permanent magnet machines accounting for opening slots. The analytical model is divided into two types of subdomains. The current of the armature is centralized in the center of the slots. The field solution of each subdomain is obtained by applying the interface and boundary conditions of the model. Two 30-pole/36-slot prototype machines with different slot-opening width are used for validation. The FE (finite element) results confirm the validity of the analytical results with the proposed model. The investigation shows that the wider the slot-opening width is, the smaller the peak value of radial and circumferential components of flux density, and the analytical armaturereaction field produced by centralized current in the slots is similar with the armature-reaction field produced by distributed current in the slots in the FE.

The Application of Magnet Structures to Reduce the Cogging Torque Associated with Fractional Slot Number in Permanent Magnet Generators

“…Similar to the methodology employed in previous work, magnet trim shaping and form slotting were implemented on the stator core [2,22,23]. Owing to the intricate geometry and existence of non-uniform regions that lead to numerous boundary conditions in these systems, the analytical computation of PMGs is sometimes very challenging.…”

“…A further evaluation of the PMG using the SD approach can be seen in Figures 5 and 6. Instead of using stator slot simplification, as previously carried out in [2,22,23], this approach has the benefit of taking into account the real SOW, as well as the effects of the stator shoe peak and width. These investigations were divided into three areas as follows: the first contained the magnets and was bounded by the radii R 1 ≤ R 2 , the second contained the air gap within R 2 ≤ R 3 , and the third included all of the machine's stator slots situated within R 3 ≤ r ≤ R 5 .…”

“…A larger part of the magnet edge can be shaped to achieve a greater reduction, but the process can reduce the machine's efficiency in generating electric power. Shaping usually causes the edge of the magnet to be thinner than the middle [2,[22][23][24], and this can decrease both the CT and commutation torque ripple in the machine [24]. Another technique to consider is the integration of a dummy slot in the stator core, which can increase the air gap cross-section and ensure a more frequent connection between the magnet surfaces and slot opening.…”