Comparative of Permanent Magnet Motors Based on Rotor Topologies and Magnet Types

Abstract

This research examines slotless permanent magnet synchronous machines (PMSMs) with surface-mounted (SPM) and in-plane-mounted (IPM) topologies using NdFeB and ferrite magnets. To ensure a fair comparison, the original and equivalent surface areas of the magnets were calculated, as shown in Table 4 for neodymium, iron, and boron magnets, and for ferrite. Finite element analysis (FEM) confirmed equal flux per pole. Parametric evaluations of the number of poles, magnet thickness, air gap length, pole-to-pitch ratio, splitting ratio, and shaft material were performed using ANSYS 2D Maxwell, with validation using MATLAB. The results demonstrate that while NdFeB provides higher flux density, optimized ferrite designs achieve lower flux density with fewer harmonics, with equal flux in both cases, highlighting ferrite as a promising and low-cost alternative. These results give an explanation for the effects of rotor parameters in slotless machines and lay the foundation for future studies incorporating slots and windings.