Advancements in axial flux permanent magnet machines utilizing coreless technology: A systematic review

Coreless axial flux permanent magnet machines (C-AFPMMs) offer exceptional efficiency, power, and torque density by eliminating iron losses, making them attractive for applications like electric vehicles, renewable energy systems, and aircraft propulsion. However, the coreless design introduces challenges, including complex mechanical structures, high production costs due to the usage of conventional materials, unstable axial forces leading to mechanical instability, potential cooling difficulties, and higher energy dissipation rates. Recent innovations in winding designs, advanced magnet arrays, and material technologies, combined with novel optimization techniques, have significantly enhanced the electromagnetic performance of these machines. This systematic review synthesizes advancements in AFPMMs with a focus on coreless technology, evaluating research developments, innovations, and applications from 2004 to 2024, based on a comprehensive analysis of 149 articles indexed by major databases such as Web of Science, Scopus, ScienceDirect, Google Scholar, and IEEE. The findings indicate sustained and increasing research activity from 2019 to 2024, with key areas of focus. Of the three coreless designs, single stator double rotors (SSDR) with stator coreless are the most commonly used, followed by double stators single rotor (DSSR) and fully coreless multi-stators multi-rotors (MSMR). There is also growing interest in rotor coreless designs, despite challenges like flux leakage, with Halbach magnet arrays of unconventional shapes being explored to mitigate these effects. These insights highlight the potential for enhancing modular configurations and thermal management in C-AFPMMs through the integration of high-strength materials, 3D printing of parts, and advanced optimization methods.